HK1171116A - Lithium ion batteries with long cycling performance - Google Patents

Description

Lithium ion battery pack with long cycle performance

Technical Field

The present invention relates to a lithium secondary battery that provides a high specific discharge capacity and a long cycle life. In addition, the present invention relates to high discharge specific capacity positive electrode compositions and methods of making the same. In general, positive electrode materials and compositions have high specific capacities while having a layered structure.

Background

Lithium batteries are widely used in consumer electronics products because of their relatively high energy density. Rechargeable batteries are also called secondary batteries, and lithium ion secondary batteries generally have a negative electrode material that intercalates lithium. For some current commercial batteries, the negative electrode material may be graphite and the positive electrode material may include lithium cobalt oxide (LiCoO)₂). In practice, only about 50% of the theoretical capacity of the cathode can be used, for example about 140 mAh/g. There are at least two other lithium-based cathode materials in commercial use today. The two materials are LiMn with spinel structure₂O₄And LiFePO having an olivine structure₄. These other materials have not provided any significant improvement in energy density.

Lithium ion batteries generally fall into two categories depending on their application. The first category includes high power batteries, where lithium ion battery cells are designed to deliver high current (amps) for applications such as power tools (power to 1) and Hybrid Electric Vehicles (HEVs). However, the energy of these battery cells is deliberately made lower because the design that provides a large current generally reduces the total energy delivered from the battery. The second design category includes high energy batteries, where lithium ion battery cells are designed to deliver small to medium current (amps) for applications such as cellular phones (cellular phones), laptop computers (1ap-top computers), Electric Vehicles (EVs), and Plug-in Hybrid Electric vehicles (PHEVs) with higher total capacity delivery.

Disclosure of Invention

In a first aspect, the invention relates to a battery comprising a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and a non-aqueous electrolyte comprising lithium ions. The negative electrode of the battery comprises graphite and the positive electrode comprises a lithium intercalation composition. The battery has a room temperature cycle 5 specific energy of discharge of at least about 175Wh/kg discharged from 4.2V to 2.5V at a C/3 discharge rate. In addition, the battery maintains at least about 70% of the discharge capacity relative to the 5 th cycle at 1000 cycles in the case where the battery is discharged from 4.2V to 2.5V at a C/2 rate from the 5 th cycle to the 1000 th cycle. In some embodiments, the lithium intercalation composition of the positive electrode can comprise a lithium-rich layered lithium metal oxide.

In some embodiments, the lithium intercalation composition can be approximated by the formula Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂Where x is between about 0.05 and 0.3. In other or alternative embodiments, the lithium intercalation composition is approximated by the formula Li_1.2Ni_0.15Mn_0.55Co_0.10O₂And (4) showing. The lithium intercalation composition of the positive electrode can have a coating comprising a metal fluoride. In addition, the electrolyte of the battery may include a stabilizing additive.

In some embodiments, the battery pack comprises a cylindrical metal housing. In another embodiment, the battery has a foil casing and a prismatic shape to form a prismatic battery. The prismatic battery may have a room temperature 5 th cycle specific discharge energy of at least about 195Wh/kg discharged from 4.2V to 2.5V at a C/3 rate. In some embodiments, the battery can maintain at least about 70% of the discharge capacity relative to the 5 th cycle at 1100 cycles with the battery being discharged from 4.2V to 2.5V at a C/2 rate from the 5 th cycle to the 1100 th cycle. Additionally, the battery pack can have a room temperature 5 th cycle energy density of at least about 425Wh/L discharged from 4.2V to 2.5V at a C/3 rate.

In another aspect, the invention relates to a battery comprising a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and a non-aqueous electrolyte comprising lithium ions. The negative electrode of the battery comprises graphite and the positive electrode comprises a lithium intercalation composition comprising a lithium-rich layered lithium metal oxide, the battery can have a room temperature 5 th cycle specific discharge energy of at least about 175Wh/kg discharged from 4.2V to 2.5V at a C/3 rate, and the battery maintains a discharge capacity of at least about 70% at 600 cycles relative to the 5 th cycle with the battery discharged from 4.2V to 2.5V at a C/2 rate from the 5 th cycle to the 600 th cycle.

In some embodiments, the lithium-rich layered lithium metal oxide is represented by the formula Li_1+xNi_αMn_βCo_γO₂Where x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, and γ is in the range of about 0.05 to about 0.4. In other embodiments, the lithium-rich layered lithium metal oxide is approximated by the formula Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂Wherein x is in a range between about 0.05 and 0.3. The lithium-rich layered lithium metal oxide of the positive electrode can have a coating comprising a metal fluoride, and the electrolyte can comprise a stabilizing additive. In some embodiments, the battery maintains at least about 70% relative to the 5 th cycle at 850 cycles with the battery discharging from 4.2V to 2.5V at a C/2 rate from the 5 th cycle to the 850 th cycleAnd (4) discharge capacity.

In another aspect, the present invention relates to an electric vehicle comprising an electric motor, a drive train (drive train) comprising wheels mounted on axles driven by the electric motor, a passenger compartment (passager unit) comprising a seat and controls. The passenger compartment of an electric vehicle is at least partially supported by the drivetrain, and the electric motor is powered by a power pack (electrical power pack) that contains a plurality of lithium ion battery packs. The power pack may provide at least about 40kWh of electrical power, may have a volume of no more than about 128 liters, and may maintain at least about 70% of the discharge capacity relative to the 5 th cycle at 1000 cycles with the battery pack being discharged from 4.2V to 2.5V at a C/2 rate from the 5 th cycle to the 1000 th cycle at room temperature. In some embodiments, the plurality of lithium ion battery packs in the power pack comprise cylindrical 26700 batteries. In another embodiment, the plurality of lithium ion batteries may include a prismatic battery having a polymer pouch casing. In some embodiments, the plurality of lithium ion battery packs of the power pack include positive electrodes including Li of formula_1+xNi_αMn_βCo_γO₂The active composition of (a), wherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, and γ is in the range of about 0.05 to about 0.4. In some embodiments, the active composition of the positive electrode can have a coating comprising a metal fluoride, and the plurality of lithium ion batteries can comprise an electrolyte comprising a stabilizing additive.

Drawings

Fig. 1 is a schematic view of a battery pack structure separated from a container.

Figure 2 is an X-ray diffraction pattern of the sample described in example 1.

Fig. 3 is a plot of voltage versus capacity for a battery formed with the sample materials described in example 1.

Figure 4 is an X-ray diffraction pattern of the sample described in example 2.

FIG. 5 is a sample of an electropositive active material formed using the method of example 2 and then synthesized using the method of example 3 using A1F₃Specific capacity versus cycle number for the coated batteries.

Fig. 6 is a plot of discharge voltage versus discharge capacity for the cylindrical battery of example 4 cycled at discharge rates of 1/3C, 1C, 2C, and 3C, respectively, in a voltage range of 2.5V to 4.2V.

Fig. 7 is a plot of discharge voltage versus discharge capacity for the cylindrical battery of example 4 charged to 4.2V with a 50mA off at 22 ℃ and subsequently discharged at-20 ℃,0 ℃, 22 ℃ and 45 ℃ respectively in the voltage range of 2.5V to 4.2V.

Fig. 8 is a graph of discharge capacity versus cycle number for the cylindrical battery of example 4 charged at 0.5C rate in the voltage range of 2.5V to 4.2V and discharged at (a)0.33C, (b)0.5C, and (C)1C, respectively.

Fig. 9 is a plot of discharge capacity versus cycle number for the cylindrical battery of example 4 cycled at a charge and discharge rate of 0.5C in the voltage range of 2.5V to 4.2V at 45 ℃.

Fig. 10 is a plot of (a) charging voltage versus charging time and (b) percent charging capacity versus charging time for the cylindrical battery of example 4 cycled at 23 ℃ at a charging rate of 0.5C.

Fig. 11 is a plot of discharge current versus discharge time for a cylindrical battery of example 4 charged to 4.2V, discharged to 20% state of charge (80% depleted), and subsequently discharged at a constant potential of 2.1V at 23 ℃ for 30 seconds.

Fig. 12 is a plot of DC discharge resistance versus state of charge percentage for the cylindrical batteries of example 4 charged to 4.2V and subsequently subjected to the 1C Pulse Test (Pulse Test) in 1 second, 5 second, 10 second, 18 second, and 30 second pulses at 23 ℃.

Fig. 13 is a plot of DC charge resistance versus state of charge percentage for the cylindrical battery of example 4 charged to 4.2V and subsequently subjected to a 1C pulse test in 1 second, 5 second, 10 second, 18 second, and 30 second pulses at 23 ℃.

Fig. 14 is a set of photographs of the cylindrical battery pack of example 4 subjected to a poor use test (away test) (a) a needle penetration test (negative penetration test), (b) a press test (crush test), and (c) a hot box test (hot box test) (3 hours in a 150 ℃ hot box).

Detailed Description

The lithium ion batteries described herein combine features that yield performance improvements over a large number of charge and discharge cycles. In particular, the battery has excellent cycling performance such that the battery exhibits deep discharge cycles of 1000 cycles or more while maintaining appropriate performance levels. The battery pack described herein is particularly suitable for use in vehicles having an electric motor, such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles. The ability to maintain performance after a large number of discharge-recharge cycles can greatly enhance the practical nature of a vehicle having an electric motor because the battery pack does not need to be replaced as often. Because the battery pack may have a relatively high cost, by extending the cycle life of the battery pack, the cost of use of the vehicle with the electric motor may be correspondingly reduced over the life of the vehicle. In addition, the battery packs described herein have a relatively high capacity. Based on the relatively high capacity, the volume and weight of the automotive battery pack can be reduced without reducing the automotive load compartment range or the automotive reach range depending on the specific parameters of the battery pack. These desired performance characteristics may also be utilized in other battery pack applications.

The lithium ion batteries described herein have achieved improved cycling performance while exhibiting high specific capacity and high overall capacity. The large capacity positive electrode materials of the long cycle life batteries described herein can be fabricated using techniques that are scalable to industrial production. Suitable synthesis techniques include, for example, co-precipitation methods or sol-gel synthesis. The use of a metal fluoride coating or other suitable coating provides enhanced cycling performance. The positive electrode material also exhibits a high average voltage over the discharge cycle, so the battery has a high power output and a high specific capacity. The battery exhibits a continuously high total capacity when cycled due to a relatively high tap density (tap density) and excellent cycling performance. In addition, the proportion of the positive electrode material that shows irreversible capacity loss after the first charge and discharge of the battery is reduced, and therefore the negative electrode material can be reduced accordingly. The combination of excellent cycling performance, high specific capacity, and high overall capacity makes these resulting lithium ion batteries improved power sources, particularly for high energy applications such as electric vehicles, plug-in hybrid vehicles, and the like.

The batteries described herein are lithium ion batteries, wherein the non-aqueous electrolyte solution comprises lithium ions. For secondary lithium ion batteries, lithium ions are released from the negative electrode during discharge, such that the negative electrode acts as an anode during discharge with electrons being generated from the oxidation of lithium as it is released from the electrode. Accordingly, the positive electrode absorbs lithium ions during discharge by intercalation or the like, so that the positive electrode functions as a cathode that consumes electrons during discharge. Upon recharging of the secondary battery, lithium ions flow back through the battery while the negative electrode takes up lithium and the positive electrode releases lithium in the form of lithium ions.

The word "element" is used herein in a conventional manner to refer to a member of the periodic table, wherein the element has an appropriate oxidation state if in the composition, and is in its elemental form M only when the element is said to be in its elemental form⁰. The metallic element is therefore generally only in its elemental form in the metallic state, or in the corresponding alloy in the form of the metallic element. In other words, metal oxides or other metal compositions other than metal alloys generally do not have metallic properties.

In some embodiments, lithium ion batteries can use positive electrode active materials that are lithium rich relative to a reference homogeneous electroactive lithium metal oxide composition. While not wishing to be bound by theory, it is believed that the properly formed lithium-rich lithium metal oxideThe material has a composite crystal structure. For example, in some embodiments of the lithium-rich material, Li₂MnO₃The material can be structurally matched with layered LiMnO₂A component or similar composite composition in which the manganese cation is substituted with other transition metal cations having the appropriate oxidation state. In some embodiments, the positive electrode material can be represented in a bi-component representation as xLi₂MO₃·(1-x)LiM′O₂Wherein M' is one or more metal cations having an average valence of +3, and at least one cation is Mn⁺³Or Ni⁺³And wherein M is one or more metal cations having an average valence of + 4. These compositions are further described, for example, in U.S. patent 6,680,143 to sakrey (Thackeray), et al entitled "Lithium Metal Oxide Electrodes for Lithium Batteries and Batteries," which is incorporated herein by reference. A positive electrode active material of particular interest has the formula Li_1+xNi_αMn_βCo_γM_δO₂Wherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, γ is in the range of about 0.05 to about 0.4, and δ is in the range of about 0 to about 0.1, and wherein M is Mg, Zn, a1, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, or combinations thereof. Those of ordinary skill in the art will recognize that other ranges of parameters within these explicit ranges are contemplated and are within the scope of the present invention.

In the following examples, in Li_1.2[Ni_0.333Co_0.333Mn_0.333]O₂A surprisingly good cycle performance and a large capacity are obtained. Additionally, as presented in U.S. patent application 12/332,735 (' 735 application) in co-pending application entitled "Positive Electrode Material for High Specific Discharge Lithium ion batteries" (which is incorporated herein by reference), Li [ Li ] et al (Lopez) et al_0.2Ni_0.175Co_0.10Mn_0.525]O₂Surprisingly large capacities have been obtained. The materials in the' 735 application are synthesized using a carbonate coprecipitation process. Furthermore, as described in U.S. application No. 12/246,814 (' 814 application) entitled "Positive Electrode Materials for Lithium Ion Batteries Having High specific discharge Capacity and methods of synthesizing these Materials" (which is incorporated herein by reference), by wenkatalcalam (Venkatachalam), et al, which is entitled "Positive Electrode Materials for Lithium Ion Batteries Having High specific discharge Capacity and methods of synthesizing these Materials," this application uses a combination of hydroxide co-precipitation and sol-gel Synthesis methods to achieve extremely High specific capacities. These compositions have a low fire risk and improved safety properties due to their specific composition with a layered structure and reduced amount of nickel relative to some other high capacity cathode materials. These compositions use smaller amounts of elements that are less desirable from an environmental standpoint and can be made from starting materials that are reasonably cost effective for large scale production.

Co-precipitation processes have been performed on the desired lithium-rich metal oxide materials, and the resulting materials exhibit improved performance characteristics when incorporated into the battery forms described herein. In addition to high specific activity, the materials exhibit superior tap densities, which results in high overall capacity of the materials in fixed volume applications. As shown in the examples below, lithium-rich metal oxide materials formed with the co-precipitation method have excellent performance properties that can be incorporated into improved batteries.

The materials described herein also exhibit high tap densities. Generally, when the specific capacities are similar, the higher tap density of the positive electrode material results in a higher overall capacity of the battery. High tap density also results in high specific energy and specific power. Generally, a battery pack having a larger capacity may provide a longer discharge time for a specific application. Accordingly, these batteries may exhibit improved performance. It is important to note that during charge/discharge measurements, the specific capacity of the material depends on the discharge rate. The maximum specific capacity of a particular material is measured at a very slow discharge rate. In practical use, the actual specific capacity is below the maximum value because of the discharge at a finite rate. More practical specific capacities can be measured using reasonable discharge rates that are more similar to the rates during use. For low to medium rate applications, a reasonable test rate involves discharging the battery within 3 hours. In conventional notation, this is written as C/3 or 0.33C.

Lithium ion intercalation and deintercalation into and from the crystal lattice can cause changes in the lattice of the electroactive material when the corresponding battery with the intercalated positive electrode active material is in use. As long as these changes are substantially reversible, the material capacity does not change. However, the capacity of the active material was observed to decrease with cycling to varying degrees. Therefore, after many cycles, the performance of the battery pack is below an acceptable value, and the battery pack is replaced. Furthermore, the irreversible capacity loss of the battery for the first cycle typically significantly exceeds each cycle capacity loss of subsequent cycles. The irreversible capacity loss is the difference between the charge capacity of the new battery and the first discharge capacity. To compensate for this irreversible capacity loss from the first cycle, additional electroactive material is included in the negative electrode so that the battery can be fully charged even if this lost capacity is unavailable for a substantial portion of the life of the battery, such that the negative electrode material is essentially discarded. Most of the irreversible capacity loss of the first cycle is generally attributed to the positive electrode material.

Suitable coating materials can improve the long-term cycling performance of the material as well as reduce the first cycle irreversible capacity loss. While not wishing to be bound by theory, the coating may stabilize the crystal lattice during the absorption and release of lithium ions such that irreversible changes in the crystal lattice are significantly reduced. In particular, metal fluoride compositions can be used as effective coatings. As cathode active material (specifically LiCoO)₂And LiMn₂O₄) General use of Coated metal fluoride compositions is described in Sun et al entitled "Fluorine Compound Coated Cathode Active Material for Lithium Secondary batteries and method for preparing the same (Cathode Active Material Coated with Fluorine Compound for Lithium)Second batteries and Method for Preparing the Same) "which is incorporated herein by reference in published PCT application WO 2006/109930A.

It has been found that metal fluoride coatings can provide substantial improvements to lithium rich layered positive electrode active materials. These improvements generally involve long-term cycling with significantly reduced capacity reduction, significant reduction in first-cycle irreversible capacity loss, and capacity increase. Because the coating material is inactive during battery cycling, it is surprising that the coating material can enhance the specific capacity of the active material. The amount of coating material can be selected to enhance the performance improvement observed. Improvements in coating materials for lithium rich positive electrode active materials are further described in the '735 application and the' 814 application.

The cycling performance depends on the depth of discharge. In particular, deeper discharges generally cause a significant reduction in cycling performance. In the results described herein, the battery was cycled in deep discharge near 100% of total capacity. Generally, the term depth-of-discharge (DOD) is used to refer to the fraction of the battery capacity referred to during battery cycling. With the improved batteries described herein, the battery initially has a large capacity, and this capacity is better maintained during long-term cycling. Good cycling of lower capacity positive electrode materials cycled at 80% DOD is described in U.S. patent 7,507,503 (the' 503 patent) to emmine (Amine) et al entitled Long Life lithium batteries with Stabilized Electrodes (Long Life lithium batteries with Stabilized Electrodes), which is incorporated herein by reference. The' 503 patent describes a stable long-term cycling of a lithium manganese oxide spinel composition and a carbon-coated olivine metal phosphate.

The results described herein are based on the synergy found between several different approaches that give batteries with good capacity in terms of current, power and energy and good cycling to 1000 cycles with DOD approaching 100%. In particular, batteries typically include lithium-rich positive electrode materials, which can provide large capacity, especially when based on developed synthetic methods. The metal fluoride coating provides stabilization with respect to cycling and reduces first cycle irreversible capacity loss while maintaining or enhancing the capacity of the material. In addition, the stabilizing additives of the electrolyte provide synergistic further improvements in cycling performance. Thus, the outstanding performance described herein comes from providing a synergistic combination of excellent battery characteristics that can result in significant improvements in performance, especially for electric automotive applications.

Generally, batteries of particular interest herein exhibit a cycle life of the battery of at least about 70% capacity retention after 1000 cycles at a C/2 discharge rate of at least 95% DOD from cycle 5 to cycle 1000 relative to cycle 5 due to synergistic improvements in battery performance. These cycle results can be obtained along with high specific energy. For example, in some embodiments, the room temperature specific energy of discharge at a rate of C/3 from 4.2V to 2.5V may be at least about 175 Wh/kg. For many applications, it is desirable for the battery to operate over a range of temperatures, and the battery should maintain reasonable performance over these temperature ranges accordingly. In some embodiments, the battery has a specific energy of at least about 135Wh/kg when discharged from 4.2V to 2.5V at a C/3 rate in the temperature range of-20 ℃ to 45 ℃.

Rechargeable batteries have a variety of uses, such as mobile communication devices (e.g., telephones), mobile entertainment devices (e.g., MP3 players and televisions), portable computers, combinations of these devices in widespread use, and transportation devices (e.g., automobiles and forklifts). Most of the battery packs used in these electronic devices have a fixed volume. Therefore, it is highly desirable that the positive electrode materials used in these batteries have a high tap density, and therefore there is substantially more chargeable material in the positive electrode, resulting in a higher total battery capacity. Batteries described herein incorporating positive electrode active materials that are improved in specific capacity, tap density, and cycling can provide improved performance to consumers, particularly for medium-intensity current applications.

The battery packs described herein are suitable for automotive applications. In particular, these battery packs may be used in battery packs for hybrid vehicles, plug-in hybrid vehicles, and pure electric vehicles. These vehicles typically have a battery pack selected to balance weight, volume, and capacity. While larger battery packs may provide greater range in electrical operation, larger packages take up more space (i.e., and thus are not usable for other purposes) and have a greater weight that may degrade performance. Thus, due to the large capacity of the batteries described herein, batteries that produce the total amount of power required can be made in reasonable volumes, and these batteries can accordingly achieve the excellent cycling performance described herein. In some embodiments, the power pack may provide at least about 40kWh of power without exceeding about 128 liters in volume.

Battery pack structure

A battery of particular interest herein is a lithium ion battery, wherein the non-aqueous electrolyte typically comprises lithium ions. For secondary lithium ion batteries, lithium ions are released from the negative electrode during discharge, such that the negative electrode acts as an anode during discharge with electrons being generated by oxidation of the lithium after it has been released from the electrode. Accordingly, the positive electrode absorbs lithium ions during discharge through intercalation or other mechanisms, such that the positive electrode acts as a cathode that neutralizes the lithium ions and consumes electrons. Upon recharging of the secondary battery, lithium ions flow back through the battery while the negative electrode takes up lithium and the positive electrode releases lithium in the form of lithium ions.

The batteries described herein include a combination of features that provide synergistic improvements in overall battery performance. In particular, battery performance may be evaluated with respect to parameters important for use of the battery with an electric vehicle. For these applications, the cycle life of the battery pack is important because it is quite costly to replace the battery pack. Furthermore, the energy density of the battery is important because a lighter weight battery is desirable if the battery can deliver the same capacity. In addition, the batteries described herein provide superior volumetric performance, which is facilitated by the higher tap density and greater loading of the positive electrode material. As described herein, desired battery performance is obtained by using a high energy density positive electrode active material synthesized using a method that produces particularly desirable material properties. The positive electrode active material may be coated to stabilize the cycling of the material. Additives in the electrolyte may further stabilize the cycling of the battery. Furthermore, the properties of the positive electrode active material can lead to a high tap density, which in turn leads to a high loading of the active material in the electrode.

Lithium has been used in primary and secondary batteries. An attractive feature of metallic lithium is that it is lightweight and it is the most electropositive metal, and these feature aspects can also be advantageously captured in lithium ion batteries. Certain forms of metals, metal oxides, and carbon materials are known to incorporate lithium ions into their structures by intercalation, alloying, or similar mechanisms. The desired mixed metal oxides are further described herein to serve as electroactive materials for positive electrodes in secondary lithium ion batteries. Lithium ion batteries refer to batteries in which the negative electrode active material is also a lithium intercalation or lithium alloy material. If metallic lithium itself is used as the anode, the resulting battery is generally referred to simply as a lithium battery.

The composition of the positive electrode active material and the negative electrode active material affects the resulting voltage of the battery, as the voltage is the difference between the half-cell potentials at the cathode and the anode. Suitable negative electrode lithium intercalation or alloy compositions can include, for example, graphite, synthetic graphite, coke, fullerene (fullerene), niobium pentoxide, tin alloys, silicon, titanium oxide, tin oxide, and lithium titanium oxide (e.g., Li_xTiO₂(x is more than 0.5 and less than or equal to 1) or Li_1+xTi_2-xO₄(0. ltoreq. x. ltoreq. 1/3)). Other Negative electrode materials are described in Kumar (Kumar) filed on 2009, 7/14 entitled "Composite Compositions, Negative Electrodes with Composite Compositions and Corresponding Batteries (Composite Compositions, Negative Electrodes with Composite Compositions and compressive Batteries)" in co-pending U.S. patent application No. 12/502,609 and Kumar (Kumar) et al entitled "lithium ion Batteries with specific Negative electrode Compositions (Lith BatteriesU.S. patent application No. 12/429,438 to the genus of Ion Batteries with particulate Negative Electrode Compositions), "both of which are incorporated herein by reference.

However, with respect to the excellent cycling properties described herein, it is generally contemplated that carbon materials such as graphite, synthetic graphite, coke and/or fullerenes, as well as lithium titanium oxide, can achieve the desired long-term cycling. Batteries with lithium titanate anodes generally operate at relatively low voltages, so these materials are expected to produce low energy density batteries. Thus, for long-cycling high energy density batteries of particular interest, the negative electrode typically comprises an activated carbon material, such as graphite, synthetic graphite, coke, fullerene, carbon nanotubes, or other graphitic carbon. Graphitic carbon generally contains sp²Graphene sheets bonded to carbon atoms. For convenience, graphitic carbon as used herein generally refers to an elemental carbon material comprising substantial regions of graphene sheets.

The positive and negative electrode active compositions are typically powder compositions that are bound together with a polymeric binder in the respective electrodes. The binder allows ionic conductivity of the active particles when in contact with the electrolyte. Suitable polymeric binders include, for example, polyvinylidene fluoride, polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylates, rubbers such as ethylene-propylene-diene monomer (EPDM) rubber, ethylene- (propylene-diene monomer) copolymer (EPDM), or Styrene Butadiene Rubber (SBR), copolymers thereof, or mixtures thereof.

The loading of active particles in the binder may be large, such as greater than about 80 wt%, in other embodiments at least about 83 wt%, and in other embodiments from about 85 wt% to about 97 wt% active material. One of ordinary skill in the art will recognize that other ranges of particle loadings within the above-identified ranges are contemplated and are within the scope of the present invention. To form the electrode, the powder and polymer may be blended in a suitable liquid, such as a solvent for the polymer. The resulting paste can be pressed into the electrode structure.

The positive electrode composition (and in some embodiments the negative electrode composition) also typically includes an electrically conductive powder that is different from the electroactive composition. Suitable supplemental electrically conductive powders include, for example, graphite, carbon black, metal powders (e.g., silver powder), metal fibers (e.g., stainless steel fibers), and the like, and combinations thereof. In general, the positive electrode may include from about 1 wt% to about 25 wt%, in other embodiments from about 1.5 wt% to about 20 wt%, and in other embodiments from about 2 wt% to about 15 wt% of the substantially conductive powder. One of ordinary skill in the art will recognize that other ranges of amounts of conductive powder within the above explicit ranges are contemplated and are within the scope of the present invention.

The electrodes are typically associated with a conductive collector (current collector) to facilitate the flow of electrons between the electrode and an external circuit. The current collector may comprise a metal, such as a metal foil or a metal grid. In some embodiments, the current collector may be formed of nickel, aluminum, stainless steel, copper, or the like. The electrode material may be cast on the current collector in the form of a film. The electrode material with the current collector attached thereto may then be dried, for example in an oven, to remove the solvent from the electrode. In some embodiments, the dried electrode material in contact with the current collector foil or other structure may be subjected to, for example, about 2kg/cm²(kilogram per square centimeter) to about 10kg/cm²To form an electrode structure assembled in a battery.

The separator may be positioned between the positive electrode and the negative electrode. The separator is electrically insulating while providing at least selected ionic conduction between the two electrodes. A variety of materials may be used as the separator. Commercial separator materials are typically formed from polymers such as polyethylene and/or polypropylene, which are porous plates that provide ionic conduction. Commercial polymer separators include, for example, from Hoechst Celanese, of Charlotte, N.C, N.CA series of separator materials. Suitable separator materials include, for example, three, 12 to 40 microns thickLaminated polypropylene-polyethylene-polypropylene sheets, e.g. having a thickness of 12 micronsAnd M824. In addition, ceramic-polymer composites have been developed for separator applications. These composite separators can be stable at high temperatures and the composite material can significantly reduce the risk of fire. Polymer-ceramic composites for Separator materials are further described in U.S. patent application 2005/0031942a entitled "electrical Separator, Method for Producing the Same and the Use Thereof" to Hennige (Hennige) et al, which is incorporated herein by reference. Polymer-ceramic composites for lithium ion battery separators are available from the German winning industry (Evonik Industries, Germany) under the trademark Evonik IndustriesAnd (5) selling.

The electrolyte of a lithium ion battery may comprise one or more selected lithium salts. Suitable lithium salts generally have an inert anion. Suitable lithium salts include, for example, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonylimide), lithium trifluoromethanesulfonate, lithium tris (trifluoromethylsulfonyl) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride, and combinations thereof. In some embodiments, the electrolyte comprises a 1M concentration of the lithium salt, although other larger and smaller concentrations may be used.

For lithium ion batteries of particular interest, nonaqueous liquids are typically used to dissolve the lithium salts. The solvent is generally inert and does not dissolve the electroactive material. Suitable solvents include, for example, propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyltetrahydrofuran, dioxolane, tetrahydrofuran, ethyl methyl carbonate, gamma-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide, dimethylformamide, triglyme (tri (ethylene glycol) dimethyl ether), diglyme (diethylene glycol dimethyl ether), DME (glyme or 1, 2-dimethoxyethane or ethylene glycol dimethyl ether), nitromethane and mixtures thereof. Additives in the electrolyte have been found to further stabilize the cycling of the battery, and these additives are described in detail in the following sections.

The electrodes described herein can be incorporated into various commercial battery designs. For example, the cathode composition can be used in prismatic batteries, coiled cylindrical batteries, coin-type batteries, or other reasonable battery shapes. The battery may comprise a single cathode structure or a plurality of cathode structures assembled in parallel and/or series electrical connection. While the positive electrode active material may be used in a battery for one or a single charge use, the resulting battery generally has cycling properties required for a secondary battery over multiple battery cycles.

In some embodiments, the positive and negative electrodes can be stacked with a separator therebetween, and the resulting stacked structure can be rolled into a cylindrical or prismatic configuration to form a battery structure. A suitable electrically conductive tab can be welded (or the like) to the current collector and the resulting jellyroll structure can be placed, for example, in a metal can or a polymer package, while the negative and positive electrode tabs are welded to suitable external contacts. Electrolyte is added to the housing and the housing is sealed to complete the battery. Some currently used rechargeable commercial batteries include, for example, cylindrical 18650 batteries (18 mm diameter and 65mm length) and 26700 batteries (26mm diameter and 70mm length), although other battery sizes may be used.

Referring to fig. 1, a battery 100 is schematically shown having a negative electrode 102, a positive electrode 104, and a separator 106 between the negative electrode 102 and the positive electrode 104. The battery may comprise a plurality of positive electrodes and a plurality of negative electrodes, for example in the form of a stack with suitably placed separators therein. An electrolyte in contact with the electrodes provides ionic conductivity through the separator between the electrodes of opposite polarity. The battery generally includes current collectors 108, 110 associated with the negative electrode 102 and the positive electrode 104, respectively.

Additive agent

The selection of the electrolyte itself or electrolyte additives can further affect the cycling stability of the battery. In particular, the selection of the electrolyte itself and/or the doping of additives can improve cycling stability, and this improvement in stability can provide a synergistic improvement in combination with the coated positive electrode material. As described herein, the selection of these electrolyte additives can be combined with the doping of electroactive materials with superior properties in terms of energy density, other capacity parameters, and cycling to produce significant performance characteristics. In particular, the electrolyte should be stable against chemical changes over time as well as against chemical degradation (due to electrochemical reactions in the battery). In addition, the desired additive or electrolyte composition may further stabilize the electroactive material during cycling.

Some common lithium salts of lithium ion battery electrolytes are described above. One type of alternative Electrolyte is described in U.S. patent 6,783,896 entitled "Electrolyte for electrochemical device" to Tsujioka et al ("the' 896 patent"), which is incorporated herein by reference. These alternative electrolytes are also described as potential electrolyte additives. Specifically, the alternative electrolyte in the' 896 patent is an ionic metal complex formed as a lithium salt for forming a lithium-based electrolyte having the formula:

wherein a is a number from 1 to 3, b is a number from 1 to 3, p ═ b/a, M is a number from 1 to 4, n is a number from 1 to 8, q is 0 or 1, M is a transition metal or an element selected from groups 13 to 15 of the periodic table, a is a transition metal or an element selected from groups 13 to 15 of the periodic table^a+Is a metal ion, onium ion or hydrogen ion, R¹Is an organic radical, R²Is halogen or an organic radical, X¹And X²Independently O, S or NR⁴And R is⁴Is halogen or an organic group. R¹、R²And R³Suitable organic groups of (c) are further discussed in the' 896 patent.Note that the' 896 patent has a significant error in its formula, A^a+Is erroneously given as A²⁺. Compositions of particular interest are represented by A^a+Is Li⁺、R²The radical being a halogen atom and X¹And X²Is represented by the formula of O atom. The' 896 patent illustrates LiBF as an electrolyte or in the form of an electrolyte blend₂C₂O₄(lithium difluoro (oxalato) borate).

Other lithium salts having anions based on halogen-free metal complexes are additionally described in U.S. patent 6,787,267 entitled "Electrolyte for Electrochemical devices" (the' 267 patent) to Tsujioka et al, which is incorporated herein by reference. The' 267 patent describes an electrolyte represented by the formula:

the symbols used in formula (2) are the same as those used in formula (1) above. One compound of interest in this class is LiB (C)₂O₄)₂I.e., lithium bis (oxalato) borate. The combination of lithium bis (oxalato) borate with a solvent comprising a lactone is additionally described in U.S.6,787,268 to cell (Koike), et al, entitled "Electrolyte", which is incorporated herein by reference.

Electrolyte additives that stabilize Batteries based on spirocyclic hydrocarbons are described in U.S. patent 7,507,503 entitled "Long Life Lithium Batteries with stabilized electrodes" (the' 503 patent) to amicin (Amine), et al, which is incorporated herein by reference. The hydrocarbon contains at least one oxygen atom and at least one alkenyl or alkynyl group. Spirocyclic additives of particular interest include compositions represented by the formula:

wherein X¹、X²、X³And X⁴Independently is O or CR³R⁴With the proviso that when Y¹Is O or X¹When Y is not O²Is O or X²When Y is not O³Is O or X³Is not O and when y⁴Is O or X⁴Is not O; y is¹、Y²、Y³And Y⁴Independently is O or CR³R⁴；R¹And R²Independently is a substituted or unsubstituted divalent alkenyl or alkynyl group; and R is³And R⁴Independently H, F, C1 or an unsubstituted alkyl, alkenyl or alkynyl group. The' 503 patent describes the use of additives having various lithium salts, including, for example, conventional lithium salts. In addition, the' 503 patent teaches the use of a lithium (chelated) borate or lithium (chelated) phosphate as an additive to the lithium metal salt or to supplement another lithium salt in the electrolyte. Specifically, the' 503 patent describes a concentration of Li [ (C) in the electrolyte of about 0.0005 wt% to about 15 wt%₂O₄)₂B]、Li(C₂O₄)BF₂Or LiPF₂C₄O₈. The' 503 patent speculates that the additive protects the electrode from chemical attack. Specifically, it is suggested in the' 503 patent that the additive form on the electrode to prevent non-lithium metal ions (e.g., Mn) in the active material⁺²Or Fe⁺²) A membrane dissolved in an electrolyte.

The combination of a Lithium (chelated) borate and a second additive that is an organic Amine, olefin, aryl compound, or mixtures thereof, as a first electrolyte additive is described in published U.S. patent application 2005/0019670 to amicin (Amine), et al entitled "Long Life Lithium Batteries with Stabilized Electrodes (Long Life Lithium Batteries with Stabilized Electrodes)", which is incorporated herein by reference. Hydrocarbon electrolyte additives containing at least one oxygen atom and at least one aryl, alkenyl, or alkynyl group are described in published U.S. patent application 2006/0147809 to amicin (Amine) et al entitled "Long Life Lithium Batteries with stabilized electrodes (Long Life Lithium Batteries with stabilized electrodes"), which is incorporated herein by reference. Gas suppressing additives for unsaturated hydrocarbon-based Lithium ion batteries, typically at concentrations of 0.1 to 10% by weight in the electrolyte, are described in published U.S. patent application 2004/0151951 entitled "Lithium based electrochemical Cell Systems" to henry (Hyung) et al, which is incorporated herein by reference. Additives comprising lithium salts having a heteroborate cluster anion are described in U.S. patent 2008/0026297 to Chen et al entitled "Electrolytes, batteries, and Methods of forming passivation Layers," which is incorporated herein by reference.

Thus, the cycle modifying additive may be a lithium salt or other composition. The lithium salt may generally provide all of the lithium ions of the electrolyte, or the stabilized lithium salt may be combined with a conventional lithium salt. Generally, if the electrolyte comprises a lithium salt blend including lithium salts corresponding to formulas (1) and (2) above, the total lithium salt may comprise from about 0.0005 wt.% to about 15 wt.%, and in other embodiments from about 0.01 wt.% to about 12 wt.% of the lithium salts corresponding to formulas (1) and (2) above. For non-lithium salt stabilizing additives, such as the additive represented by formula (3) above, the electrolyte may comprise from about 0.0005 wt% to about 20 wt%, in other embodiments from about 0.01 wt% to about 15 wt%, and in other embodiments from about 0.1 wt% to about 10 wt% of the additive. One of ordinary skill in the art will recognize that other additive concentration ranges within the above-identified ranges are contemplated and are within the scope of the present invention.

Positive electrode active material

The positive electrode active material comprises a lithium intercalation metal oxide composition. In some embodiments, the lithium metal oxide composition may comprise a lithium-rich composition that is generally believed to form a layered composite structure. The positive electrode active compositions can exhibit surprisingly high specific capacities and high tap densities in lithium ion battery cells under practical discharge conditions. The desired electrode active material may be synthesized using the synthesis methods described herein.

In some embodiments, the composition may be prepared by reacting Li_1+xNi_αMn_βCo_γM_δO_2-zF_zWherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, γ is in the range of about 0.05 to about 0.4, δ is in the range of about 0 to about 0.1, and z is in the range of about 0 to about 0.1, and wherein M is Mg, Zn, a1, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, or combinations thereof. Those of ordinary skill in the art will recognize that other ranges of parameter values within the above explicit ranges are encompassed and are within the scope of the present invention. Fluorine is a dopant that can help with cycle stability and improve material safety. In the embodiment where z is 0, this formula is reduced to Li_1+xNi_αMn_βCo_γM_δO₂. In other embodiments, the parameters have ranges wherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.4 to about 0.65, γ is in the range of about 0.05 to about 0.3, and δ is in the range of about 0 to about 0.1.

Kang (Kang) and colleagues have described a composition for secondary batteries having the formula Li_1+xNi_αMn_βCo_γM′_δO_2-zF_zM' is Mg, Zn, Al, Ga, B, Zr, Ti, x is in the range of about 0 to 0.3, α is in the range of about 0.2 to 0.6, β is in the range of about 0.2 to 0.6, γ is in the range of about 0 to 0.3, δ is in the range of about 0 to 0.15, and z is in the range of about 0 to 0.2. These metal ranges and fluorine are proposed to improve the battery capacity and stability of the resulting layered structure during electrochemical cycling. See Kang (Kang) et al entitled "Layered cathode Material for lithium ion rechargeable batteries (Layered cathode mat)U.S. patent 7,205,072 ('072 patent) to materials ionic batteries,' which patent is incorporated herein by reference. The' 072 patent reports a cathode material having a capacity of less than 250mAh/g (milliamp hour/gram) after 10 cycles at room temperature at a rate that is not specified and can be assumed to be lower to enhance performance values. It is noted that if fluorine is replaced by oxygen, the oxidation state of the polyvalent metal is lower relative to that of the fluorine-free composition.

Suitable coatings have been found to provide desirable improvements in cycling properties without the use of fluorine dopants, but in some embodiments it may be desirable to have fluorine dopants. Additionally, it is desirable in some embodiments that δ be 0 in the above formula to make the composition simpler while still providing improved performance. For these embodiments, if z is 0 and δ is 0, then the formula reduces to Li_1+xNi_αMn_βCo_γO₂(wherein the parameters are summarized above) and it has been found that compositions within this formula achieve highly desirable properties.

With respect to some embodiments of the materials described herein, sakulare (Thackery) and coworkers have proposed composite crystal structures of some lithium-rich metal oxide compositions, where Li₂M′O₃The composition is structurally integrated with LiMO₂In the layered structure of the components. The electrode material can be represented by Li in a two-component representation₂M′O₃·(1-a)LiMO₂Wherein M is one or more metal elements having an average valence of +3 and at least one element is Mn or Ni, and M' is a metal element having an average valence of +4, and 0 < a < 1. For example, M may be Ni⁺²、Co⁺³And Mn⁺⁴Combinations of (a) and (b). The general formula of these compositions can be written as Li_1+xM′_2xM_1-3xO₂. It has been observed that batteries formed from these materials are comparable to batteries formed with the corresponding LiMO₂The composition forms batteries that cycle at higher voltages and have greater capacity. These materials are further described in saxorey (Thackery) et al entitled "lithium Metal oxide electrodes (Lit) for lithium batteries and Battery packsU.S. patent 6,680,143 to hium Metal Oxide Electrodes for Lithium Cells and Batteries and U.S. patent 6,677,082 to saxoley (Thackery), et al, entitled "Lithium Metal Oxide Electrodes for Lithium Batteries and Batteries," are both incorporated herein by reference. Sakeley (Thackery) identified Mn, Ti and Zr as being of particular interest for M' and Mn and Ni for M.

Some specific layered structure structures are further described in saxorey (Thackery) et al, "lithium rich Li for lithium batteries_1+xM_1-xO₂Review of the structural complexity of electrodes (M ═ Mn, Ni, Co) (Comments on the structural complexity of lithium-rich Li_1+xM_1-xO₂Electrochemistry (M ═ Mn, Ni, Co) for lithium batteries) ", electrochemical Communications (Electrochemistry Communications)8(2006), 1531-1538, which are incorporated herein by reference. The studies reported in this article reviewed compounds having the formula Li_1+x[Mn_0.5Ni_0.5]_1-xO₂And Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂The composition of (1). The article also describes the structural complexity of the layered material. The following examples are given with the composition Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂The properties of the material of (a). These materials were synthesized and modified with coatings as described below. The synthesis method and coating provide materials with superior performance in terms of capacity as well as cycling properties. These improved properties of the active materials, along with the method of cell construction and electrolyte additives, provide the improved battery performance described herein.

Li using the synthetic method described in the following application_1+xNi_αMn_βCo_γM_δO_2-z/2F_zThe composition achieves high specific capacity: wencacatalam (Venkatachalam) et al entitled "lithium ion with high specific discharge CapacityThe Positive Electrode materials of the Batteries and the methods of synthesizing these materials (Positive Electrode Material for Lithium Ion battery High Specific Capacity and process for the Synthesis of the materials) "are in co-pending U.S. patent application 12/246,814 ('814 application) and Lopez (Lopez) et al, entitled" Positive Electrode Material for High Specific Capacity Lithium Ion Batteries (Positive Electrode Material High Specific Capacity Lithium Ion battery "), are in co-pending U.S. patent application 12/332,735 (' 735), both of which are incorporated herein by reference. In particular, Li [ Li ]_0.2Ni_0.175Co_0.10Mn_0.525]O₂Surprisingly good results have been obtained. The carbonate co-precipitation method described in the' 735 application results in the desired lithium-rich metal oxide material having cobalt in composition and exhibiting high specific capacity performance with excellent tap density. These co-pending patent applications also describe the effective use of the coating to improve performance and recycling. The' 072 patent to Kang (Kang) et al investigated a number of specific compositions, including, for example, Li_1.2Ni_0.15Mn_0.55Co_0.10O₂Similar to the compositions studied in the examples of the '735 application and the' 814 application, but with significantly improved performance described in the '735 application and the' 814 application.

The performance of the positive electrode active material is affected by many factors. The average particle size and the particle size distribution are two basic properties characterizing the positive electrode active material, and these properties affect the rate capability and tap density of the material. Because batteries have a fixed volume, materials for the positive electrodes of these batteries are required to have a high tap density if the specific capacity of the material can be maintained at the desired high value. Thus, the overall capacity of the battery may be higher due to the presence of more chargeable material in the positive electrode.

Synthesis method

The synthetic methods described herein can be used to form a polymer with cyclic modificationsThe layered lithium-rich cathode active material has good specific capacity, excellent cycle performance and high tap density. The synthesis method is already suitable for synthesizing the compound with the formula of Li_1+xNi_αMn_βCo_γM_δO₂Wherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, γ is in the range of about 0.05 to about 0.4, and δ is in the range of about 0 to about 0.1, and wherein M is Mg, Zn, a1, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, or combinations thereof. The synthesis method is also suitable for industrial scale-up. Specifically, a co-precipitation method or a sol-gel method can be used to synthesize a desired lithium-rich type positive electrode material having a desired effect. In particular, hydroxide co-precipitation methods as well as carbonate co-precipitation methods have resulted in active materials with highly desirable properties.

In the hydroxide coprecipitation method, metal salts are dissolved in an aqueous solvent (e.g., purified water) in a desired molar ratio. Suitable metal salts include, for example, metal acetates, metal sulfates, metal nitrates, and combinations thereof. The concentration of the solution is generally chosen between 0.1M and 2M. The relative molar amounts of the metal salts can be selected according to the desired formula of the product material. The pH of the solution may then be adjusted, for example by adding lithium hydroxide and/or ammonium hydroxide, to precipitate a metal hydroxide having the desired amount of metal element. In general, precipitation may be performed by adjusting the pH to a value between about 10pH units and about 12pH units. The solution may be heated and stirred to promote precipitation of the hydroxide. Subsequently, the precipitated metal hydroxide may be separated from the solution, washed and dried to form a powder, followed by further processing. For example, drying may be performed in an oven at about 110 ℃ for about 4 hours to about 12 hours.

The collected metal hydroxide powder may then be subjected to a heat treatment to remove water from the hydroxide composition and convert to the corresponding oxide composition. Generally, the heat treatment can be performed in an oven, a furnace, or the like. The heat treatment may be performed in an inert atmosphere or an atmosphere in the presence of oxygen. In some embodiments, the material may be heated to a temperature of at least about 300 ℃ and in some embodiments to about 350 ℃ to about 1000 ℃ to convert the hydroxide to an oxide. The heat treatment may generally be carried out for at least about 15 minutes, in other embodiments from about 30 minutes to 24 hours or more, and in other embodiments from about 45 minutes to about 15 hours. Further heat treatment may be performed to increase the crystallinity of the product material. This calcination step for forming the crystalline product is generally conducted at a temperature of at least about 650 ℃, and in some embodiments from about 700 ℃ to about 1200 ℃, and in other embodiments from about 750 ℃ to about 1100 ℃. The calcination step to enhance the structural properties of the powder may generally be performed for at least about 15 minutes, in other embodiments from about 20 minutes to about 30 hours or more, and in other embodiments from about 30 minutes to about 24 hours. If desired, the heating step may be combined with a suitable ramp of temperature to obtain the desired material. One of ordinary skill in the art will recognize that other temperature and time ranges within the above explicit ranges are contemplated and are within the scope of the present invention.

In the carbonate coprecipitation method, metal salts are dissolved in an aqueous solvent (e.g., purified water) in a desired molar ratio. Suitable metal salts include, for example, metal acetates, metal sulfates, metal nitrates, and combinations thereof. The concentration of the solution is generally chosen between 1M and 3M. The relative molar amounts of the metal salts can be selected according to the desired formula of the product material. Then, for example, by adding Na₂CO₃And optionally ammonium hydroxide to adjust the pH of the solution to precipitate the metal carbonate in the desired amount of the metal element. Generally, the pH can be adjusted to a value between about 6.0 and about 9.0. The solution may be heated and stirred to promote precipitation of the carbonate. Subsequently, the precipitated metal carbonate may be separated from the solution, washed and dried to form a powder, followed by further processing. For example, drying may be performed in an oven at about 110 ℃ for about 4 hours to about 12 hours. Those of ordinary skill in the art will recognize that other ranges of method parameters within the explicit ranges above are contemplated and are within the scope of the present invention.

The collected metal carbonate powder can then be subjected to a heat treatment to decarbonate the carbonate composition for conversion to the corresponding oxide composition. Generally, the heat treatment can be performed in an oven, a furnace, or the like. The heat treatment may be performed in an inert atmosphere or an atmosphere in the presence of oxygen. In some embodiments, the material may be heated to a temperature of at least about 350 ℃ and in some embodiments to about 400 ℃ to about 800 ℃ to convert the carbonate to the oxide. The heat treatment may generally be carried out for at least about 15 minutes, in other embodiments from about 30 minutes to 24 hours or more, and in other embodiments from about 45 minutes to about 15 hours. Further heat treatment may be performed to increase the crystallinity of the product material. This calcination step for forming the crystalline product is generally conducted at a temperature of at least about 650 ℃, and in some embodiments from about 700 ℃ to about 1200 ℃, and in other embodiments from about 700 ℃ to about 1100 ℃. The calcination step to enhance the structural properties of the powder may generally be performed for at least about 15 minutes, in other embodiments from about 20 minutes to about 30 hours or more, and in other embodiments from about 1 hour to about 36 hours. If desired, the heating step may be combined with a suitable ramp of temperature to obtain the desired material. One of ordinary skill in the art will recognize that other temperature and time ranges within the above explicit ranges are contemplated and are within the scope of the present invention.

In either co-precipitation process, the lithium element may be incorporated into the material in one or more selected steps of the process. For example, the lithium salt may be incorporated into the solution by addition of a hydrated lithium salt before or after the precipitation step is performed. In this method, lithium species are incorporated into the precipitation material in the same manner as other metals. Furthermore, due to the nature of lithium, the lithium element can be incorporated into the material in a solid phase reaction without adversely affecting the resulting properties of the product composition. Thus, for example, an appropriate amount of a lithium source (e.g., LiOH H), typically in powder form, can be used₂O、LiOH、Li₂CO₃Or a combination thereof) is mixed with the precipitated metal hydroxide or carbonate. Subsequently, the powder mixture is advanced through a heating step to form an oxide and subsequently a crystalline positive electrode material.

The synthesis of lithium-rich layered metal oxide positive electrode materials using efficient co-precipitation and sol-gel methods is additionally described in the following documents: U.S. application No. 12/246,814 (' 814 application) entitled "Positive Electrode Material for High Specific Discharge Capacity Lithium Ion Batteries and process for the synthesis of Materials" and U.S. application No. 12/332,735 (' 735 application ') entitled "Positive Electrode Material for High Specific Discharge Capacity Lithium Ion Batteries (Positive Electrode Material for High Specific Discharge Capacity Lithium Ion Batteries"), both of which are incorporated herein by reference, "wenkatacaham (venkatacalam), et al. Examples in the '814 and' 735 applications relate to Li_1.2Ni_0.175Co_0.10Mn_0.525O₂The method can be generalized to other stoichiometries of lithium-rich layered complex metal oxides. The following examples relate toLi _1.07 Ni _0.31 Co _0.31 Mn _0.31 O ₂ Is performed.

Coating and method of forming coating

The inert inorganic coating has been found to significantly improve the performance of the lithium rich layered positive electrode active materials described herein. In particular, it has been found that the cycling properties of batteries formed from lithium metal oxides coated with metal fluorides are significantly improved compared to batteries formed from uncoated materials. In addition, for metal fluoride coatings, the total capacity of the battery also shows desirable properties in the case of fluoride coatings, and the first cycle irreversible capacity loss of the battery is reduced. As previously described, the first cycle irreversible capacity loss of a battery is the difference between the charge capacity of a new battery and its first discharge capacity. Most of the first cycle irreversible capacity loss is generally attributed to the positive electrode material.

In addition, other inert inorganic coatings have been proposed for stabilizing certain positive electrode active materials. Specifically, the use of metal oxide or metal phosphate coatings has been described in published U.S. patent application 2006/0147809 (the' 809 application) entitled "Long Life Lithium Batteries with Stabilized Electrodes" to Amine et al, which is incorporated herein by reference. Particularly for active materials having a spinel or olivine crystal structure, the' 809 application specifically describes ZrO-containing materials₂、TiO₂、WO₃、A1₂O₃、MgO、SiO₂、AlPO₄、Al(OH)₃Or a mixture thereof. The metal oxide may be formed by precipitating the hydroxide and calcining (i.e., heat treating) the product to form the oxide. Alternatively, a sol-gel process may be used to synthesize the oxide coating. The metal phosphate coating may be formed by precipitating phosphate in contact with the powder of the material to be coated.

The metal fluoride coating can provide unexpected improvements in the performance of the high capacity lithium-rich compositions described herein. Generally, selected metal fluorides or metalloid fluorides can be used as the coating. Similarly, coatings having combinations of metal and/or metalloid elements can be used. Metal/metalloid fluoride coatings have been proposed to stabilize the performance of positive electrode active materials of lithium secondary batteries. Suitable metal and metalloid elements for fluoride coatings include, for example, Al, Bi, Ga, Ge, In, Mg, Pb, Si, Sn, Ti, Tl, Zn, Zr, and combinations thereof. Aluminum fluoride can be a desirable coating material because it is reasonably cost effective and is considered environmentally friendly. A metal fluoride coating is generally described in published PCT application WO 2006/109930 (Sun) entitled "fluoride Coated Cathode active Material for Lithium Secondary Batteries and Method for preparing the Same" published PCT application WO 2006/109930'930PCT application), which is incorporated herein by reference. The' 930PCT application provides a coating coated with LiF, ZnF₂Or A1F₃Of LiCoO (R) in a gas phase₂The result of (1). The' 930PCT application specifically relates to the following fluorochemical compositions: CsF, KF, LiF, NaF, RbF, TiF, AgF₂、BaF₂、CaF₂、CuF₂、CdF₂、FeF₂、HgF₂、Hg₂F₂、MnF₂、MgF₂、NiF₂、PbF₂、SnF₂、SrF₂、XeF₂、ZnF₂、A1F₃、BF₃、BiF₃、CeF₃、CrF₃、DyF₃、EuF₃、GaF₃、GdF₃、FeF₃、HoF3、InF₃、LaF₃、LuF₃、MnF₃、NdF₃、VOF₃、PrF₃、SbF₃、ScF₃、SmF₃、TbF₃、TiF₃、TmF₃、YF₃、YbF₃、T1F₃、CeF₄、GeF₄、HfF₄、SiF₄、SnF₄、TiF₄、VF₄、ZrF₄、NbF₅、SbF₅、TaF₅、BiF₅、MoF₆、ReF₆、SF₆And WF₆。

A1F₃Coating pair LiNi_1/3Co_1/3Mn_1/3O₂The effect of cycling performance of (1) is described further in Sun (Sun) et al, "A1F₃Coating improved Li [ Ni ] of lithium secondary battery_1/3Co_1/3Mn_1/3]O₂High voltage cycling performance of cathode materials (A1F)₃-Coating to Improve High Voltage Cycling Performance of Li[Ni_1/3Co_1/3Mn_1/3]O₂Cathodal Materials for Lithium Secondary Batteries ", journal of the electrochemical Society, 154(3), A168-A172 (2007). Further, A1F₃Coating pair LiNi_0.8Co_0.1Mn_0.1O₂The effect of cycling performance is further described in Hu (Woo) et al, "Jing A1F₃Coated Li [ Ni ]_0.8Co_0.1Mn_0.1]O₂Significant Improvement of electrochemical Performance of cathode material (Significant Improvement of electrochemical Performance of AlF)₃-Coated Li[Ni_0.8Co_0.1Mn_0.1]O₂Cathode Materials) ", journal of Electrochemical Society, 154(11) a1005-a1009(2007), which is incorporated herein by reference. Wu (Wu) et al, "surface-modified, high-volume, layered Li [ Li ] with low irreversible capacity loss_(1-x)/3Mn_(2-x)/3Ni_x/3Co_x/3]O₂Cathode (High Capacity, Surface-modified layer Li [ Li ]_(1-x)/3Mn_(2-x)/3Ni_x/3Co_x/3]O₂Cathodes with Low Irreversible Capacity Low) ", Electrochemical and Solid State Letters, 9(5) A221-A224(2006) noted at A1₂O₃The irreversible capacity loss is reduced in the case of coatings, which article is incorporated herein by reference.

As demonstrated in the examples below, it has been found that metal/metalloid fluoride coatings can significantly improve the performance of lithium rich layered compositions of lithium ion secondary batteries. The coating improves the capacity of the battery. However, the coating itself is electrochemically inactive. A reduction in battery capacity is expected when the specific capacity loss due to the amount of added coating in the sample exceeds the benefit of the added coating offset by the electrochemical inactivity of the coating. In general, the amount of coating can be selected to balance the advantageous stability resulting from the coating in the event of a specific capacity loss due to coating material weight that does not typically directly contribute to the high specific capacity of the material. Generally, the amount of coating material ranges from about 0.01 mole% to about 10 mole%, in other embodiments from about 0.1 mole% to about 7 mole%, in other embodiments from about 0.2 mole% to about 5 mole%, and in other embodiments from about 0.5 mole% to about 4 mole%. Field of the inventionThose of ordinary skill in the art will recognize that other ranges of coating materials within the explicit ranges above are contemplated and are within the scope of the present invention. Warp beam A1F₃A1F in coated metal oxide materials effective to improve uncoated material capacity₃The amount of (c) is related to the particle size and surface area of the uncoated material. In particular, higher mole percent metal fluoride coatings are generally available for higher surface area powders to achieve equivalent effects relative to coatings on lower surface area powders.

The fluoride coating may be deposited using a solution-based precipitation method. Powders of the positive electrode material can be mixed in a suitable solvent (e.g., an aqueous solvent). The soluble composition of the desired metal/metalloid can be dissolved in a solvent. Subsequently, NH may be reacted₄F is gradually added to the dispersion/solution to precipitate the metal fluoride. The total amount of coating reactants can be selected to form the desired coating weight, and the ratio of coating reactants can be based on the stoichiometry of the coating material. The coating mixture may be heated to a reasonable temperature (e.g., in the range of about 60 ℃ to about 100 ℃ for aqueous solutions) for about 20 minutes to about 48 hours during the coating process to facilitate the coating process. After removing the coated electroactive material from the solution, the material may be dried and heated to a temperature of generally about 250 ℃ to about 600 ℃ for about 20 minutes to about 48 hours to complete the formation of the coated material. The heating may be performed under a nitrogen atmosphere or other substantially oxygen-free atmosphere.

Battery performance

Batteries formed as described herein exhibit synergistic performance improvements due to a combination of stabilization methods and improved synthesis of positive electrode active materials. In particular, the synthesis method described herein is suitable for manufacturing a lithium-rich type positive electrode active material with improved capacity and excellent cycle properties. The inorganic coating may further stabilize the positive electrode material. In addition, electrolyte additives also improve cycling in a synergistic manner, with other improvements to the material. Based on synergistic improvements, lithium ion batteries have achieved previously unavailable performance over long-term cycling of the battery under deep discharge conditions. For medium current applications, improved performance effects have been obtained with the positive electrode active materials described herein under actual discharge conditions.

The performance of the battery can be described in terms of the positive electrode active composition and/or with respect to the overall performance of the battery. Cell performance may depend on the anode material and the battery configuration and the performance of the positive electrode material. The lithium-rich layered metal oxide positive electrode materials described herein provide high specific capacity and high specific energy. Using the synthesis methods described herein, positive electrode materials with good crystallinity provide higher capacity and energy performance, and high tap densities can be obtained. These lithium-rich materials also have relatively good cycling properties.

Inorganic coatings on lithium rich type positive electrode materials have been found to provide several advantages. In particular, even if the coating is inert, it can surprisingly result in enhanced specific capacity and specific energy performance. In addition, the coating can reduce first cycle irreversible capacity loss over the first battery cycle. In addition, the coating also significantly improves the cycling performance of the battery.

The irreversible capacity loss is the difference between the charge capacity of the new battery and the first discharge capacity. To compensate for this first cycle irreversible capacity loss, additional electroactive material is included in the negative electrode so that the battery can be fully charged to the selected potential even if this lost capacity is not available during most of the battery's useful life, such that some negative electrode material is essentially wasted. Most of the first cycle irreversible capacity loss is generally attributed to the positive electrode material. In addition, in the case of the coated positive electrode active materials described herein, the proportion of the positive electrode material that exhibits irreversible capacity loss after the first charge and discharge of the battery is reduced, and thus the amount of the negative electrode material can be correspondingly reduced if necessary. Thus, it provides better performance to the battery because it is desirable to include a smaller excess of negative electrode material in the battery that does not promote cycling performance of the battery.

Generally, various similar test procedures may be used to evaluate battery performance. Specific test procedures are described to evaluate the performance values described herein. The test procedure is described in more detail in the examples below. Specifically, the battery pack may be cycled between 4.2 volts and 2.5 volts at room temperature or other selected temperatures. For the first three cycles, the stack was discharged at a rate of C/10 to create an irreversible capacity loss. The battery pack is then cycled at C/3, C/2 or other selected values (which is a reasonable test rate for medium intensity current applications). Further, the notation C/x means that the battery pack is discharged at a rate such that the battery pack is fully discharged to the selected voltage in x hours. Battery capacity depends to a large extent on the discharge rate, with capacity being lost as the discharge rate increases.

In some embodiments, the positive electrode active material has a specific capacity of at least about 150 milliamp hours per gram (mAh/g) and in other embodiments at least about 155mAh/g discharged from 4.2V to 2.5V at a C/3 discharge rate during the 5 th cycle. The first cycle irreversible capacity loss of the coated electroactive material can be reduced by at least about 25% relative to the equivalent performance of the uncoated material. The tap density of the material, measured as described below, may be at least about 1.8 g/mL. High tap density translates into high total capacity for a fixed volume battery. One of ordinary skill in the art will recognize that other ranges of specific capacity and tap density and irreversible capacity loss reduction are encompassed and within the scope of the present invention.

In general, tap density is the apparent density of the powder obtained under the tap conditions. The apparent density of a powder depends on how close the individual particles of the powder are packed together. The apparent density is affected not only by the true density of the solid but also by the particle size distribution, particle shape and cohesiveness. In general, a greater tap density allows for incorporation of a greater amount of active material in a fixed size electrode, resulting in an electrode with a correspondingly greater capacity. The positive electrode active materials herein have a relatively high tap density such that the performance per volume values of the battery generally exhibit particularly desirable values.

Generally, battery performance depends on the design properties of the battery. For example, the cylindrical batteries described in the examples below were packaged in cylindrical steel cans, which contributed significantly to the weight of the batteries. The battery pack may be assembled in, for example, a foil pouch or the like in the shape of a prism (e.g., generally a rectangular parallelepiped). The foil pouch may comprise a polymer and/or metal foil, or the like. The specific capacity and specific energy of a battery of foil cell design may be greater relative to a cylindrical cell design having a metal can due to the potential for weight reduction of the packaging material. In addition, prismatic cells may be constructed with a rigid outer casing formed from metal and/or plastic. For the batteries described in the examples below, if prismatic cells with pouch cans were used, the specific energy would be expected to approach 200Wh/kg relative to 175Wh/kg measured for the cylindrical batteries reported in the examples. Pouch cells incorporating High Energy positive electrode materials are additionally described in U.S. patent application 12/403,521, entitled "High Energy Lithium Ion Secondary Batteries," to Buckley et al, which is incorporated herein by reference. Furthermore, prismatic cells, due to their shape, can generally be packaged in volumes that are less space-wasting relative to cylindrical cells.

The United States Advanced Battery Consortium, USABC, has a set of Battery targets for electric vehicles. These objectives are presented in table 1.

TABLE 1

The long term objective was compared to the battery performance of example 4 below. The temperature range provides for proper operation for the range of operating environments to which the vehicle is exposed.

In terms of battery performance, current, energy and power capacity can be measured after several cycles, so the initial irreversible change does not affect the performance value. However, after several cycles, there is no significant performance degradation experienced at longer cycle times. For convenience, the performance of the cell independent of long-term cycling is commonly referred to as the 5 th cycle with a discharge rate of C/3. In some embodiments, the battery pack may have a room temperature specific energy of discharge of at least about 175Wh/kg, in other embodiments at least about 180Wh/kg, and in other embodiments from about 185Wh/kg to about 200Wh/kg for the 5 th cycle to discharge from 4.2V to 2.5V at a C/3 discharge rate. Additionally, the battery pack may have a room temperature discharge energy density of at least about 400Wh/L, in other embodiments at least about 420Wh/L, and in other embodiments from about 430Wh/L to about 480Wh/L for the 5 th cycle to discharge from 4.2V to 2.5V at a C/3 discharge rate. In terms of power density, the battery pack may have a power density of at least 1500W/L, in other embodiments at least about 1800W/L, and in other embodiments from about 2200W/L to about 2400W/L. The power density was measured at 80% depth of discharge within 30 seconds. In some embodiments, the power pack may provide at least about 40kWh of power while not exceeding about 128 liters in volume. Those of ordinary skill in the art will recognize that other ranges of specific energy, energy density, and power density within the above-identified ranges are contemplated and are within the scope of the present invention.

In general, the cycling performance of a battery depends very significantly on the depth of discharge during cycling. Specifically, significantly improved cycling can be obtained by cycling to a lower percentage of the depth of discharge. The depth of discharge is related to the battery capacity based on the design charging voltage. Thus, the design of a battery having a lower charging voltage may improve cycling performance, but on the other hand, may result in a correspondingly lower performance property, such as capacity, energy density, power density, and the like. The batteries described herein involve cycling between 4.2V and 2.5V, which represents a depth of discharge of at least about 97% at the discharge rate described herein (i.e., C/2 or slower rate).

From cycle 5 to cycle 1000, discharged from 4.2V to 2.5V at a C/2 rate, the improved performance batteries described herein exhibit room temperature cycling of at least about 70% capacity at 1000 cycles, in other embodiments at least about 70% capacity at 1100 cycles, in other embodiments at least about 70% capacity at 1200 cycles, in other embodiments from about 80% to about 85% capacity at 1000 cycles relative to cycle 5. For cycles at 45 ℃, discharging from 4.2V to 2.5V at a C/2 rate from cycle 5 to cycle 1000, the battery may exhibit cycles of at least about 70% capacity at 1000 cycles, in other embodiments at least about 70% capacity at 1100 cycles, and in other embodiments from about 72% to about 80% capacity relative to cycle 5. For pulsed operation, the impedance of the battery at room temperature may typically be below 45m Ω when charging or discharging the battery for 30 seconds at 20% or more state of charge of the battery with 1C pulse. Those of ordinary skill in the art will recognize that other ranges of cycling performance within the above-identified ranges are contemplated and are within the scope of the present invention.

Examples of the invention

Examples 1-3-Synthesis and preliminary testing of Positive electrode materials

The coin cell batteries tested in examples 1-3 were all performed using coin cell batteries manufactured according to the procedure outlined herein. Lithium Metal Oxide (LMO) powder was mixed with acetylene black (Super P from Timcal, Ltd, Switzerland)^TM) And graphite (KS 6 from ultra-dense high Limited (Timcal, Ltd.)^TM) Mixed thoroughly to form a homogeneous powder mixture. Polyvinylidene fluoride (PVDF) (KF 1300 from wu-feather corporation, Japan) was independently blended^TM) Mixed with N-methyl-pyrrolidone (NMP) (Honeywell) -Riedel-de-Haen) and stirred overnight to form a PVDF-NMP solution. Subsequently, the homogeneous powder mixture was added to the PVDF-NMP solution and mixed for about 2 hours to form a homogeneous slurry. Using a doctor's blade coat methoding process) the slurry was coated on an aluminum foil current collector to form a wet film.

The positive electrode structure was formed by drying the aluminum foil current collector with the wet film in a vacuum oven at 110 ℃ for about 2 hours to remove NMP. The positive electrode and foil current collector are pressed together between the rolls of the sheet mill to obtain a positive electrode structure having the desired thickness. An example of a positive electrode composition developed using the above method having an LMO: acetylene black: graphite: PVDF ratio of 80: 5: 10 is presented below.

The positive electrode was placed in a glove box filled with argon gas to manufacture a coin-type battery pack. A 125 micron thick Lithium foil (FMC Lithium) was used as the negative electrode. The electrolyte is 1M LiPF₆A solution by mixing LiPF₆The salt was formed dissolved in a 1: 1 volume ratio mixture of ethylene carbonate, diethyl carbonate and dimethyl carbonate (Ferro Corp., Ohio USA, Ohio). An electrolyte-impregnated three-layer (polypropylene/polyethylene/polypropylene) microporous separator (2320, available from celerd, LLC, NC, USA) was placed between the positive and negative electrodes. A few drops of electrolyte were added between the electrodes. Next, the electrodes were sealed in 2032 coin-type battery hardware (Hohsen corp., Japan) by a crimping method (crimping process), to form a coin-type battery pack. The resulting coin-type battery pack was tested with a mancor cycle tester (Maccor cycle tester) to obtain a charge-discharge curve and cycle stability during multiple cycles.

Example 1 formation of Li [ Li ] by Metal acetate with LiOH _0.07 Ni _0.31 Co _0.31 Mn _0.31 ]O ₂ Reaction of (2)

This example shows the formation of an active positive electrode material using a hydroxide co-precipitation method.

Adding stoichiometric amount of nickel acetate (Ni (CH)₃COO)₂·xH₂O), cobalt acetate (Co (CH)₃COO)₂·xH₂O) and manganese acetate (Mn (CH)₃COO)₂·xH₂O) was dissolved in distilled water to form a metal acetate solution. An aqueous solution of LiOH was prepared separately. The two solutions were gradually added to the reaction vessel to form a metal hydroxide precipitate. The reaction mixture was stirred while maintaining the temperature of the reaction mixture between room temperature and 80 ℃. The pH of the reaction mixture is about 10 to 12. Generally, the aqueous metal sulfate solution has a concentration of 1M to 3M, and the aqueous LiOH solution has a concentration of 1M to 4M. The metal hydroxide precipitate was filtered, washed with distilled water several times, and dried at 110 ℃ for 16 hours to form a metal hydroxide powder. Lithium hydroxide was added to adjust the pH and the washed precipitate was not expected to contain a significant amount of lithium.

An appropriate amount of LiOH powder was combined with dry metal hydroxide powder and thoroughly mixed by a Jar Mill (Jar Mill), double planetary mixer (double planetary mixer), or dry powder mixer to form a homogeneous powder mixture. The homogenized powder was calcined at 400 ℃ in air for 8 hours, followed by other mixing steps to further homogenize the powder formed. The homogenized powder was then calcined at 900 ℃ for 12 hours in air to form the approximate formulaLi[Li _0.07 Ni _0.31 Co _0.31 Mn _0.31 ]O ₂ The lithium complex oxide powder (LMO) shown below.

The LMO powder structure was measured by X-ray diffraction, and the X-ray diffraction pattern of the powder is shown in fig. 2. Coin cells were formed using LMO powder according to the procedure outlined above. Coin cells were tested and a graph of voltage versus capacity is shown in fig. 3. The cathode material has a specific discharge capacity of 176 mAh/g.

EXAMPLE 2 formation of Li [ Li ] by Metal sulfate with NaOH/NH4OH _0.07 Ni _0.31 Co _0.31 Mn _0.31 ]O ₂ Reaction of (2)

This example shows a co-precipitation process based on a metal sulfate starting material and a base provided as a mixture of sodium hydroxide and ammonium hydroxide.

The treatment in this example by forming a dry precipitate was carried out in an oxygen-free atmosphere. Adding stoichiometric amount of metal sulfate (NiSO)₄·xH₂O、CoSO₄·xH₂O、MnSO₄·xH₂O) is dissolved in distilled water to form an aqueous metal sulfate solution. Independently preparing NaOH and NH₄An aqueous solution of a mixture of OH. The two solutions were gradually added to the reaction vessel to form a metal hydroxide precipitate. During the precipitation step, the reaction mixture is stirred while maintaining the temperature of the reaction mixture between room temperature and 80 ℃. The pH of the reaction mixture is about 10 to 12. The aqueous metal sulfate solution has a concentration of 1M to 3M, and NaOH/NH₄The aqueous OH solution has a NaOH concentration of 1M to 3M and a NH concentration of 0.2M to 2M₄The OH concentration. The metal hydroxide precipitate was filtered, washed with distilled water several times, and dried at 110 ℃ for 16 hours to form a metal hydroxide powder.

The appropriate stoichiometric amount of LiOH powder was combined with the dry metal hydroxide powder and thoroughly mixed by a jar mill, double planetary mixer, or dry powder mixer to form a homogeneous powder mixture. The homogenized powder was calcined in air at 500 ℃ for 10 hours, followed by another mixing step to further homogenize the resulting powder. The homogenized powder was further calcined at 900 ℃ for 12 hours in air to form a lithium composite oxide powder (LMO). Product produced by birthThe composition has Li [ Li ]_0.07Ni_0.31Co_0.31Mn_0.31]O₂The stoichiometry of (a).

The LMO powder structure was measured by X-ray diffraction, and the X-ray diffraction pattern of the powder is shown in fig. 4. Coin cells were formed using LMO powder according to the procedure outlined above. The resulting coin cells were tested and a plot of specific capacity versus cycle life is shown in fig. 5. FIG. 5 also includes coatings A1F as described in the examples below₃Data of active powder of (4). The first three cycles were measured at a discharge rate of 0.1C. Subsequent cycles were measured at a rate of 0.33C.

Example 3-warp A1F ₃ Formation of coated metal oxide materials

This example shows the formation of aluminum fluoride coated particles, and presents an assessment of the specific capacity of these materials compared to the corresponding uncoated materials.

The metal oxide particles prepared in the above examples can be coated with aluminum fluoride (A1F) using a solution-assisted method₃) A thin layer. For a selected amount of aluminum fluoride coating, a saturated solution of an appropriate amount of aluminum nitrate was prepared in an aqueous solvent. Subsequently, the metal oxide particles are added to the aluminum nitrate solution to form a mixture. The mixture was mixed vigorously for a period of time to homogenize. The length of time of mixing depends on the volume of the mixture. After homogenization, a stoichiometric amount of ammonium fluoride is added to the homogenized mixture to form aluminum fluoride precipitates on the surface of each particle. After the precipitation was complete, the mixture was stirred at 80 ℃ for 5 hours. Subsequently, the mixture was filtered and the resulting solid was washed repeatedly to remove any unreacted material. The solid was calcined at 400 ℃ for 5 hours in a nitrogen atmosphere to form a calcined product A1F₃A coated metal oxide material.

Specifically, the method described in this example was used to coat the Lithium Metal Oxide (LMO) particles synthesized in example 2 with 3 mole% aluminum fluoride. Subsequently, coin cells were formed using the aluminum fluoride coated LMO according to the procedure outlined above. The specific capacity versus cycle life of the coin cell is shown in fig. 5. Figure 5 also contains data for coin cells formed from the uncoated LMO of example 2. The first three cycles were measured at a discharge rate of 0.1C. Subsequent cycles were measured at a rate of 0.33C. The coated samples had significantly greater discharge capacity, especially after cycling.

EXAMPLE 4 commercial form of cylindrical Battery

This example demonstrates the excellent cycling performance of a layered lithium-rich metal oxide composition having stabilization as described herein.

Manufacture of a catalyst approximating the formula Li [ Li ] using a carbonate coprecipitation process_0.07Ni_0.31Co_0.31Mn_0.31]O₂The powder composition shown. Lithium Metal Oxide (LMO) powder was mixed with acetylene black (Super P from Timcal, Ltd, Switzerland)^TM) And graphite (KS 6 from ultra-dense high Limited (Timcal, Ltd.)^TM) Mixed thoroughly to form a homogeneous powder mixture. Separately, polyvinylidene fluoride (PVDF) was mixed with N-methyl-pyrrolidone (NMP) and stirred overnight to form a PVDF-NMP solution. Subsequently, the homogeneous powder mixture was added to the PVDF-NMP solution and mixed for about 2 hours to form a homogeneous slurry. The slurry was coated on an aluminum foil current collector using a commercial squeegee to form a wet film.

The positive electrode structure was formed by drying an aluminum foil current collector having a wet film electrode to remove NMP. The positive electrode and the current collector are pressed together between the cylinders of the sheet mill to obtain a positive electrode of the desired thickness associated with the foil current collector. One example of a positive electrode composition developed using the method corresponding to the results described herein above has a ratio of LMO to acetylene black to graphite to PVDF of 95: 2: 1: 2.

The positive electrode structure was placed in an argon filled glove box toA cylindrical battery pack was manufactured. A blend of graphite and binder was used as the negative electrode, and the negative electrode composition was coated on a copper foil current collector. The polymer binder is a blend of Styrene Butadiene Rubber (SBR) and carboxymethylcellulose. The negative electrode composition had a weight ratio of graphite to SBR to CMC of 97.5 to 1.2. The electrolyte is 1M LiPF₆A solution by mixing LiPF₆The salt was formed dissolved in a 1: 1 volume ratio mixture of ethylene carbonate, diethyl carbonate and dimethyl carbonate (Ferro Corp., Ohio USA, Ohio). The electrolyte additionally comprises a stabilizing additive. An electrolyte-impregnated three-layer (polypropylene/polyethylene/polypropylene) microporous separator (2320, available from celerd, LLC, NC, USA) was placed between the positive and negative electrodes. A few drops of electrolyte were added between the electrodes. The electrode stack with positive electrode-separator-negative electrode was rolled up and placed in a can sized for a 26700 size (26mm x 70mm) cylindrical cell. The electrodes are then sealed to form a complete 26700 battery. The resulting cylindrical batteries were tested with a marcoble tester to obtain charge-discharge curves and cycle stability over multiple cycles.

In the first set of measurements, the battery pack was tested for discharge characteristics. Specifically, the cylindrical batteries were cycled in a voltage range of 2.5V to 4.2V at discharge rates of 1/3C, 1C, 2C, and 3C, respectively, and a plot of discharge voltage versus discharge capacity for the 5 th discharge cycle is shown in fig. 6. The cell exhibited slightly greater capacity at the relatively low 1/3C discharge rate, while the discharge capacities at 1C, 2C, and 3C discharge rates were approximately equal.

The performance of the cells was also tested at different temperatures. Referring to fig. 7, a group of battery packs were discharged at-20 deg.c, 0 deg.c, 22 deg.c and 45 deg.c, respectively, and the voltage of the 5 th discharge cycle was plotted as a function of the capacity. Although the capacity decreases at lower temperatures, the capacity of the battery pack is reasonable at low temperatures. At a temperature of-20 ℃, the battery retained 76% of the room temperature capacity.

To test the cycling stability of cylindrical batteries at room temperature, the batteries were charged at a rate of 0.5C in a voltage range of 2.5V to 4.2V and discharged at (a)0.33C, (b)0.5C, and (C)1C, respectively. This voltage range represents close to 100% capacity in terms of depth of discharge. A plot of discharge capacity versus cycle number for the three discharge rates is shown in fig. 8. In addition, each rate test was repeated three times. At room temperature, the batteries maintained good discharge capacities up to about 900 cycles at 0.33C, 0.5C, and 1C discharge rates. The battery was additionally tested at a 0.5C charge/discharge rate in a voltage range of 2.5V to 4.2V at 45 deg.c, and a graph of discharge capacity versus cycle number is shown in fig. 9. The cell maintained good discharge capacity up to about 1100 cycles at 45 ℃.

In general, the cycling performance in the test set was based on an upper limit of 4.2V for the charging voltage. Thus, the initial charge of the battery is to 4.2V, and the battery is then cycled to the upper limit of this charge voltage. However, the material has the ability to be charged to higher voltages. Thus, when the battery is charged to 4.2V, the active material is not at full capacity when the voltage of 4.2V is first reached. Referring to fig. 10, the percent charge capacity and change in charge voltage versus charge time were recorded when the battery was charged at a charge rate of C/2 at 23 ℃. When the voltage reached 4.2V, the capacity percentage was about 90%.

The capacity of these batteries during discharge of the batteries near the end of their useful life was also investigated. After the battery was initially charged to 4.2V, the battery was discharged to a 20% state of charge, i.e., the battery pack was depleted by 80%. Subsequently, the battery was discharged at a constant potential of 2.1V at 23 ℃ for 30 seconds. A graph of discharge current as a function of time is shown in fig. 11.

Further, the battery pack was initially charged to 4.2V and subsequently discharged to a 20% state of charge, and the maximum current available over a set period was evaluated based on the battery remaining at a voltage greater than 2.1V. Under a10 second discharge pulse, the current delivered during discharge was 49A while remaining above 2.1V. At a 30 second discharge pulse, the discharge current delivered by the battery pack was 35A while remaining at a voltage greater than 2.1V. The specific power of the battery pack is calculated from the current capacity measurement. Specifically, the current delivered during the discharge pulse is multiplied by the average voltage. For example, for a 30 second pulse, the specific power is calculated as follows: (35A × 2.2V)/94.5g ═ 800W/kg. For a10 second pulse, the specific power was 1,100W/kg. In addition, in the case of the instantaneous discharge, the specific power was 1,250W/kg.

To perform the pulse test again, the battery was charged to 4.2V and then subjected to the 1C pulse test at 23 ℃ with 1 second, 5 second, 10 second, 18 second, and 30 second pulses. In the pulse test, the DC resistance as a function of the state of charge starting from an initial 90% state of charge corresponding to an initial charge to 4.2V was evaluated. Plots of DC discharge/charge resistance versus battery state of charge for five different pulse times are shown in fig. 12 (discharge) and fig. 13 (charge), respectively. Detailed 1C pulse test data is summarized in table 2 below.

TABLE 2

The battery was additionally subjected to poor use tests including a needle punch test, a compression test, and a hot box test in which the battery was held in a hot box at 150 ℃ for 3 hours. No fire or explosion was observed from these poor use tests, and a photograph of the poor use battery is shown in fig. 14.

The overall performance of the battery is summarized in table 3.

TABLE 3

Capacity of	4.4Ah
		Nominal voltage	3.7V
Size of	26mm(OD)×70mm(H)
		Weight (D)	92.7 g
Cycle life	Greater than 1000 times at about 100% DOD
		Cathode electrode	Li[Li0.07Ni0.31Co0.31Mn0.31]O2
Cathode capacity	Discharge from 4.2 to 2.5V at 0.33C of 160mAh/g

Capacity and nominal voltage were evaluated by fully discharging at C/3 rate at cycle 5.

The united states advanced battery pack consortium (USABC) has a set of targets for batteries for electric vehicles, which are compared in table 4 with the battery performance of example 3.

TABLE 4

Power and capacity reduction is an acceptable loss in the form of percentage of rated specification before the end of the useful life of the battery is reached. The battery in this example met or exceeded all parameters for long term performance, except for the specific energy, which had a value of 90% of the target. The use of a foil housing instead of a metal can or a higher energy lithium rich composition can easily increase the specific energy well beyond the target value.

The above embodiments are intended to be illustrative and not limiting. Other embodiments are within the scope of the following claims. In addition, although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Any incorporation by reference of documents above is limited such that no subject matter is incorporated that departs from the explicit disclosure herein.

Claims (21)

1. A battery comprising a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and a non-aqueous electrolyte comprising lithium ions, wherein the negative electrode comprises graphite and the positive electrode comprises a lithium intercalation composition, the battery having a room temperature specific energy of discharge of at least about 175Wh/kg at a C/3 discharge rate from 4.2V to 2.5V for cycle 5 and a cycle life of at least about 70% capacity at 1000 cycles versus cycle 5 at a C/2 discharge from 4.2V to 2.5V from cycle 5 to cycle 1000.

2. The battery of claim 1, wherein the lithium intercalation composition of the positive electrode comprises a lithium-rich layered lithium metal oxide.

3. The battery of claim 1, wherein the lithium intercalation composition is approximated by the formula Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂Where x is between about 0.05 and 0.3.

4. The battery of claim 1, wherein the lithium intercalation composition is approximated by the formula Li_1.2Ni_0.15Mn_0.55Co_0.10O₂And (4) showing.

5. The battery of claim 1 wherein the lithium intercalation composition of the positive electrode has a coating comprising a metal fluoride.

6. The battery of claim 1, wherein the electrolyte comprises a stabilizing additive.

7. The battery of claim 1, further comprising a cylindrical metal housing.

8. The battery of claim 1 having a foil casing and a prismatic shape.

9. The battery of claim 8, wherein the battery has a specific energy to discharge at room temperature of at least about 195Wh/kg at a C/3 discharge rate from 4.2V to 2.5V for cycle 5.

10. The battery of claim 1, wherein the battery has a cycle life of at least about 70% capacity at 1100 cycles relative to 5 cycles at C/2 discharge from 4.2V to 2.5V from 5 cycles to 1100 cycles.

11. The battery of claim 1, wherein the battery has a room temperature energy density of at least about 425Wh/L discharged from 4.2V to 2.5V at a C/3 discharge rate for cycle 5.

12. A battery comprising a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and a non-aqueous electrolyte comprising lithium ions, wherein the negative electrode comprises graphite and the positive electrode comprises a lithium intercalation composition, wherein the lithium intercalation composition comprises a lithium-rich layered lithium metal oxide, the battery having a specific energy at room temperature discharge of at least about 175Wh/kg with a C/3 discharge rate from 4.2V to 2.5V for cycle 5 and a cycle life of at least about 70% capacity at 600 cycles relative to cycle 5 at C/2 discharge from 4.2V to 2.5V from cycle 5 to cycle 600.

13. The battery of claim 12, wherein the lithium-rich layered metal oxide composition is represented by the formula Li_1+xNi_αMn_βCo_γO₂Where x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, and γ is in the range of about 0.05 to about 0.4.

14. The battery of claim 12, wherein the lithium-rich layered metal oxide composition is approximately represented by the formula Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂Where x is between about 0.05 and 0.3.

15. The battery of claim 12 wherein the lithium-rich layered metal oxide composition of the positive electrode has a coating comprising a metal fluoride and the electrolyte comprises a stabilizing additive.

16. The battery of claim 12, wherein the battery has a cycle life of at least about 70% capacity at 850 cycles relative to the 5 th cycle at C/2 discharge from 4.2V to 2.5V from the 5 th cycle to the 850 th cycle.

17. An electric automobile comprising an electric motor, a drivetrain comprising wheels mounted on axles driven by the electric motor, a passenger compartment comprising seats and controls, and a power pack comprising a plurality of lithium ion battery packs, wherein the passenger compartment is supported at least in part by the drivetrain, wherein the power pack provides at least about 40kWh of power and a volume of no more than about 128 liters and a room temperature cycle life of at least about 70% capacity at 1000 cycles relative to the 5 th cycle at a discharge from the 5 th cycle to the 1000 th cycle at C/2 from 4.2V to 2.5V.

18. The electric automobile of claim 17, wherein the plurality of lithium ion batteries comprises cylindrical 26700 cells.

19. The electric vehicle of claim 17, wherein the plurality of lithium ion batteries comprises a prismatic battery having a polymeric pouch casing.

20. The electric vehicle of claim 17, wherein the plurality of lithium ion batteries include a positive electrode including Li of the formula_1+xNi_αMn_βCo_γO₂The active composition of (a), wherein x is in the range of about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.3 to about 0.65, and γ is in the range of about 0.05 to about 0.4.

21. The electric vehicle of claim 20, wherein the active composition of the positive electrode has a coating comprising a metal fluoride, and wherein the plurality of lithium ion batteries comprise an electrolyte comprising a stabilizing additive.