TWI899812B - Process for the preparation of overlithiated lithium metal oxides - Google Patents

Abstract

The invention relates to a process for the preparation of overlithiated transition metal oxides, for example Li ₂NiO ₂, from a mixture consisting of lithium peroxide and at least one transition metal oxide or a manganese-containing spinel compound in a two-stage calcination process with respect to temperature and atmospheric composition.

Description

Preparation method of lithium metal oxide

This case relates to an economical method for preparing lithium peroxide metal oxide from lithium peroxide and at least one transition metal oxide, and its use. The lithium peroxide metal oxide is used as a cathode additive for pre-lithiation in lithium-ion batteries.

Lithium-ion batteries (LIBs) represent the upper limit of currently viable battery technologies on an industrial scale in terms of energy density. Consequently, their use in stationary and mobile current storage systems is rapidly expanding. Demand for mobile applications, particularly in automotive and other transportation technologies, is growing, and they demand even higher energy density. This trend necessitates the use of battery materials with extremely high capacities and electrode combinations capable of achieving extremely high voltages.

Current high-power lithium batteries contain high-voltage positive electrode materials, primarily nickel-rich materials such as Li(Ni _x Mn _y Co _z )O ₂ (x+y+z=1 and Ni>0.33) or high-voltage spinel compounds such as LiMn _1.5 Ni _0.5 O ₄ . Graphite-based materials with a theoretical capacity of 372 mAh/g are typically used as negative electrode materials. To increase capacity, lithium alloy materials, particularly silicon-based powders, are often mixed with graphite.

The usable energy of lithium-ion batteries (LIBs) decreases due to a series of decomposition and parasitic reactions. The most significant parasitic reaction in LIBs is the loss of active lithium during the negative electrode film formation process, which forms a solid electrolyte layer (SEI) on the surface of the anode particles during the initial charge/discharge cycle. As is well known, graphite anodes typically consume approximately 3-5% of the total lithium introduced into the battery along with the cathode material to form the SEI. For the remainder of the process, the SEI remains stable. The lithium is "consumed" by the formation of the protective layer, that is, it is converted into a form that is no longer electrochemically active and disappears during the complete utilization and discharge cycle of the cathode material.

When alloy anode components such as Si or Sn-based powders are used, the irreversible initial losses are significantly higher: Li losses can be as high as 20%, depending on their proportion in the anode material.

To compensate for these losses, metallic lithium or various lithium-rich compounds can be added to the cathode and/or anode materials. These pre-lithiated agents provide their lithium reserves during the "formation" period of the battery cell (i.e., during the first charge/discharge cycle) and decompose to form volatile by-products or primarily electrochemically inactive solids. To minimize the proportion of inactive solids, the amount of activatable lithium must be as high as possible. This is the case with many so-called overlithiated lithium metal oxides. Overlithiated metal oxides, also known as lithium-enriched metal oxides, have an increased lithium content compared to standard lithium-ion battery cathode materials and can provide additional lithium during the first charge cycle to compensate for irreversible lithium loss on the anode side. Because this process is irreversible, the overlithiated metal oxide does not recover in subsequent cycles.

In order to balance the charge, the transition metal M contained exists in a correspondingly reduced form compared to the corresponding lithium-ion battery positive electrode material.

The following table explains this: Redox active elements LIB-positive electrode material "normal form" M oxidation state Lithium-containing form (maximum lithium content) M oxidation state Fe Li ₂ FeO ₄ +6 Li ₅ FeO ₄ +3 Ni _LiNiO2 +3 Li ₂ NiO ₂ +2 Co _LiCoO2 +3 Li ₆ CoO ₄ +2 Mn, Ni LiNi _0.5 Mn _1.5 O ₄ +3.5 Li ₂ Ni _0.5 Mn _1.5 O ₄ +3 Mn LiMn ₂ O ₄ +3.5 Li ₂ Mn ₂ O ₄ +3

When the battery is discharged (usually irreversibly), the overlithiated lithium metal oxide can release lithium from the structure to form an oxide, and the redox-active metal contained in it is correspondingly oxidized.

The table above lists the final stages of overlithiation. Starting from a "normal" cathode material, there are all intermediate stages between the "normal form" and the overlithified forms in terms of lithium content. These are formed by the absorption of lithium into the base material, primarily under reducing conditions, i.e. in a non-oxidizing atmosphere. For the purposes of this application, all the above-mentioned lithium-ion battery cathode materials whose lithium content exceeds that of normal lithiumization are considered to be "overlithified" (see also US-A-6 652 605). Unlike lithium-ion battery cathode materials, overlithified metal oxides are generally unstable in air and water, i.e. they must be handled under inert gas to avoid adverse changes.

For example, the following compositions are used: Li _2+x FeO ₄ (0≦x≦3); Li _1+x NiO ₂ (0≦x≦1); Li _1+x CoO _1.5+0.5x (0≦x≦5); and the lithium spinel compound Li _1+x Mn ₂ O ₄ (0≦x≦1); Li _1+x Ni _0.5 Mn _1.5 O ₄ (0≦x≦1). In the case of Li ₆ CoO ₄ , this compound will absorb additional oxygen during the lithium absorption process (F. Holtstiege, Batteries 2018, 4, 4).

The preparation of the lithium metal compounds is generally carried out by reacting a lithium salt, for example hydrated lithium hydroxide, lithium carbonate, or preferably lithium oxide, with the corresponding transition metal hydroxide or transition metal oxide or a mixture of different transition metal hydroxides or oxides.

For example, according to the prior art (G. Cedar, Chem. Mater. 2004, 2685), lithium nickel oxide (Li2NiO2) is known to be produced by reacting lithium oxide with nickel oxide in an inert atmosphere (i.e., in the absence of oxygen):

To this end, nickel oxide and lithium oxide were first ground in a ball mill, then granulated and calcined at 650°C for 24 hours under an inert argon atmosphere.

Lithium percobaltate Li ₆ CoO ₄ is prepared by solid-solid reaction of CoO and Li ₂ O at 900°C in a nitrogen atmosphere (Yingying Zhou, Dissertation 2021, https://doi.org/10.14989/doctor.k22548). Li ₅ FeO ₄ is prepared by reacting Li ₂ O and Fe ₃ O ₄ at 500°C or 800°C in air (MV Blanco et al., Chem. Eng. J. 354, 2018, 370-7), according to the reaction formula: Fe ₃ O ₄ + 7.5 Li ₂ O + 0.5 O ₂ → 3 Li ₅ FeO ₄

Alternatively, it can be synthesized from a ground mixture of Fe ₂ O ₃ and Li ₂ O by first heating to 450°C and then heating to 750°C under inert conditions (WM Dose et al., J. Electrochem. Soc. 2020, 167 160543). Fe ₂ O ₃ + 5 Li ₂ O à 2 Li ₅ FeO ₄

Lithium spinels such as Li _1+x Ni _0.5 Mn _1.5 O ₄ are prepared by reacting the corresponding common cathode material LiNi _0.5 Mn _1.5 O ₄ with a lithium source under reduction conditions at 600°C (G. Gabrielli et al., J. Power Sources, 351, 2017, 35).

The disadvantage of the aforementioned process is the use of _Li₂O , which can only be produced through very complex processes. For example, by the combustion of metallic lithium, or by the thermal decomposition of lithium carbonate at temperatures >900°C, or by the thermal decomposition of a mixture of lithium carbonate and carbon black at temperatures >700°C. Since lithium carbonate melts at 720°C, the thermal decomposition of lithium carbonate usually produces a solidified melt or at least a strongly sintered product, which must then be crushed and ground through a complex process. This type of mechanical comminution and subsequent screening operations require the exclusion of air components ( _H₂O and _CO₂ ) that react with lithium oxide, resulting in very high process costs.

In contrast, the production of _Li₂O by thermal decomposition of lithium peroxide _Li₂O₂ requires relatively low temperatures _of about 300°C to 400°C, conditions well below the melting point. Therefore, thermal decomposition occurs according to the following formula:

Directly forms finely divided, flowable Li ₂ O powder, which is very suitable for producing products such as Li ₂ NiO ₂ (J. Kim et al., Molecules 2019, 24, 4624).

However, a disadvantage of this production process is that the _Li2O produced _{from Li2O2} must be separated separately and then mixed with NiO or another transition metal oxide or hydroxide in a separate reaction step before being pyrolyzed (KR101887171 B1).

The object of the present invention is to provide a method for preparing lithium metal oxides such as Li ₂ O ₂ from Li ₂ NiO ₂ and transition metal oxides such as NiO by low-cost, preferably one-pot synthesis.

The object of this case is solved by a method characterized by: a) mixing lithium peroxide _Li2O2 with at least one transition metal _{oxide MaOb or} a manganese-containing spinel compound, and then; b) calcining the mixture; wherein M in the transition metal oxide is selected from any one of Fe, Ni, Co and Mn, a is an integer from 1 to 3, b is a number from 1 to ₄ , and the manganese-containing spinel compound is selected from _LiMn2O4 or _{LiNi0.5Mn1.5O4 ;} and the mixture is continuously calcined at at least two consecutive different temperature levels; wherein step b) includes a first temperature level in the range of 280°C to 450°C and _a second temperature level in the range of 500°C to 950°C.

In this method, powdered lithium peroxide is mixed with at least one desired metal oxide or manganese-containing spinel compound to form a mixture. Preferably, the mixing of the at least two components, namely, lithium peroxide and at least one transition metal oxide or manganese-containing spinel compound, is performed under grinding conditions. The resulting mixture is preferably compressed or pressed by applying external pressure.

The mixture is then calcined in two process steps at two different temperature levels to convert it into lithium peroxide. Preferably, the calcination is carried out in a one-pot process.

The lithium peroxide used preferably has a high specific surface area, preferably at least 1 m2/g, particularly preferably at least 2 ^m2 /g.

The calcination includes a first temperature level preferably in the range of 300°C to 400°C, and a second temperature level preferably in the range of 600°C to 900°C.

In addition, the calcination time at the first temperature level is preferably in the range of 0.5 hours to 20 hours, particularly 1 hour to 10 hours, and most preferably 2 hours to 10 hours.

Independently, a calcination time at the second temperature level is preferably independently in the range of 1 hour to 96 hours, preferably 1 hour to 72 hours, more preferably 2 hours to 72 hours, and even more preferably 2 hours to 48 hours.

During calcination at the first temperature level, lithium oxide _Li2O is formed as oxygen is released, which is pumped out of the system either in vacuum or by overflowing with an inert gas such as nitrogen or argon.

During the calcination at the second temperature level, the formed lithium oxide Li ₂ O reacts with at least one transition metal oxide or a manganese-containing spinel compound to form a lithium metal oxide.

Calcination in the first and second temperature ranges is suitably carried out under vacuum or an inert gas atmosphere. The vacuum is preferably 1 Pa to 10,000 Pa (0.01 mbar to 100 mbar), particularly 5 Pa to 5,000 Pa (0.05 mbar to 50 mbar), and the inert gas atmosphere is formed by an inert gas or inert gas mixture that excludes water/moisture and _CO . The inert gas/inert gas mixture preferably comprises nitrogen, argon, or helium. Furthermore, calcination at the second temperature level is further carried out under conditions that largely exclude oxygen.

The two calcination steps can be carried out at different temperature levels and are preferably carried out in the same reaction vessel, with time and/or space separation measures being used to ensure that the different temperature ranges and atmosphere conditions in the two reaction steps meet the requirements.

The present invention surprisingly discovered that the decomposition of lithium peroxide under the condition of oxygen release does not cause undesirable oxidation of metal oxides or manganese-containing spinel compounds present in the mixture. Therefore, under the first temperature level of 280°C to 450°C calcination conditions required for peroxide decomposition under vacuum conditions or in an inert gas flow (such as nitrogen), it can be found that the transition metal-containing oxide is inert. In this way, the desired perlithiated metal oxide compound can be obtained with high purity by calcining at a high temperature of at least 500 to 950°C in the second step.

According to the present invention, calcination is carried out in a corrosion-resistant and high-temperature resistant container or reactor, and the structural material of the reactor is particularly a high-temperature resistant material that is resistant to alkaline lithium salt corrosion. Preferably, the structural material is selected from high-temperature resistant metal materials containing Cr and/or Al materials (particularly Ni-based alloys containing Cr and/or Al, Ni and Cr-containing austenitic steels, low-Ni or Ni-free ferritic steels containing Cr and Al, or Cr-containing mixed austenitic-ferritic steels), oxide ceramics (particularly Al ₂ O ₃ , lithium aluminate ceramics (LiAlO ₂ ), Ce-based ceramics (particularly Ce-stabilized ZrO ₂ ), non-oxide ceramics (particularly carbides, preferably SiC, BC, TiC; nitrides, preferably TiN, AlN; and borides, preferably NbB 2 , BN, aluminized TiB ₂ , "TiBAl").

According to the present invention, the preparation method can be performed under static conditions. The mixture of the transition metal oxide and _{the Li₂O₂} is first heated to a temperature range of 280°C to 450°C in a corrosion-resistant housing or as a bulk material on a tape under vacuum or in an inert gas atmosphere. Furthermore, the thermal decomposition of the _Li₂O₂ occurs with _the release of oxygen. After the decomposition of _{the Li₂O₂} is complete and the oxygen formed in the system is removed, the temperature is raised to the required range of 500°C to 950°C to form the lithiated metal oxide, while ensuring an oxygen-free atmosphere.

Alternatively, according to the present invention, the preparation method can be carried out under moving bed conditions in a reactor to ensure continuous mixing of the reaction mixture. In this case, the reactor preferably includes at least two heatable rotary tubes to operate continuously in different temperature zones. The temperature in the inlet area of the raw material mixture is 280°C to 450°C, while the temperature in the rear area is 500°C. The temperature range in the rear area closer to the product discharge area is 500°C to 950°C. In the temperature range of 500 to 950°C, suitable conditions are set to form lithium metal oxide by overflowing an inert gas or an inert gas mixture that is substantially free of _O2 , _CO2 and _H2O . In this process, the inert gas or inert gas mixture is preferably passed in countercurrent to the direction of movement of the solid reaction mixture.

The mixing of lithium peroxide and at least one transition metal oxide can be carried out in a rotary mixer with an energy input in the range of 100 kW/m ³ to 500 kW/m ³ or in a mill, in particular an impact rotor mill (impact mill), a grinding media mill or a pin mill.

The powder mixture is then preferably compacted, for example by tableting in a process. This involves applying pressure to the powder mixture in a movable die, or by means of a roller, i.e., two rollers rotating relative to each other, or by a powder press. The applied pressure ranges from 0.001 kbar to 100 kbar, preferably from 0.01 kbar to 50 kbar.

_The transition metal oxide used in the preparation method of the present invention is preferably selected from NiO, CoO, _Fe2O3 , _{Fe3O4 and} FeO.

_{The Li₂O₂} and transition metal oxides have a mixed molar ratio ranging from 0.6:1 to 3:1, preferably from 0.9:1 to 3:1, and particularly 1:1 when M=Ni. Other preferred ratios include 5:1 for M=Fe, 2:1 for M=Ni, and 6:1 for M=Co.

The superlithiated lithium metal oxide prepared in the present invention is preferably Li ₅ FeO ₄ , Li ₂ NiO ₂ , Li ₆ CoO ₄ or a superlithiated manganese-containing spinel compound, especially Li _1+x Mn ₂ O ₄ or Li _1+x Ni _0.5 Mn _1.5 O ₄ , wherein 0≦x≦1.

Particularly preferably, the lithium metal oxide is Li ₂ NiO ₂ and the mixed molar ratio of Li ₂ O ₂ :NiO is 1:1.

The lithium-ion metal oxide compound produced by the preparation method of this case is used for pre-lithiation in the production of lithium-ion batteries.

The implementation of the preparation method of this case is described in more detail below.

In order to implement the preparation method according to the present invention, lithium peroxide _{Li2O2 ,} preferably in powder form, and transition metal oxide _{MaOB are} first mixed. Different equipment and process technologies can be applied to the mixing process. Among them, rotary mixers are particularly suitable, which can provide an energy input in the range of about 10 kW/ ^m3 to 500 kW/ ^m3 . Among rotary mixers, those with a rotating container and those with a rotating mixing tool are suitable. It is important to have a sufficiently strong energy input. Similar units can be designed according to the countercurrent or crosscurrent principle, such as the "intensive mixer" designed by Eirich. Other suitable mixer designs are paddle dryers with an additionally installed knife grinder, such as those provided by Lödige, and intensive mixers with high-speed rotors, such as the brand name "Nobilta" from Hosokawa.

Most types of mills are also suitable for intensive mixing, particularly agitator rotor mills (impact mills), grinding media mills, or pin mills; knife or cutting mills can also be used to a limited extent. In grinding media mills, mixing is performed in the grinding drum using hard grinding media, such as balls or rods composed of metals (steel or nickel-based alloys) or hard ceramics (metal oxides, metal carbides, metal nitrides, etc.). The grinding container and grinding media should have a Vickers hardness of at least 400, preferably at least 600. Materials made of stainless steel or metal oxides, such as aluminum oxide or zirconium oxide, are particularly preferred. Ball mills, rod mills, or hammer mills can also be used.

For subsequent compaction, single-axis powder presses such as those available from Frey & Co. can be used. On a smaller scale, simple punch/die systems are preferred. For processing large quantities of powder, axial powder presses with servo motors, mechanical or hydraulic compression, such as those offered by Dorst Technologies, are more suitable.

The subsequent thermal conversion (calcination) was carried out at two different temperature levels and in different gas atmospheres.

This can be illustrated by the example of producing lithium nickel oxide.

In the first step, which is a low temperature step at 280°C to 450°C, preferably 300°C to 400°C, especially in the range of 320°C to 380°C, only the lithium peroxide in the mixture is converted to lithium oxide: Li ₂ O ₂ /NiO à Li ₂ O/NiO + 1/2 O ₂

The evolved oxygen is removed from the reactor system by evacuation, i.e., under constant depressurization (dynamic depressurization), or by a carrier gas flow consisting of a gas mixture free of _H₂O and _CO₂ . Suitable carrier gases are inert gases (commercial quality _N₂ , Ar, He) or dry, _CO₂ -free air.

In the second step, a mixture consisting of approximately equimolar amounts of lithium oxide and nickel oxide is calcined at a higher temperature to form the desired perlithiated nickel oxide in a solid/solid reaction: Li ₂ O/NiO à Li ₂ NiO ₂

This second reaction step needs to be carried out at a higher temperature of 550°C to 750°C, preferably 60°C to 700°C. Furthermore, this reaction step is also carried out under vacuum conditions or an inert gas atmosphere. The gas atmosphere is the opposite of the first calcination stage, and oxygen must be excluded (i.e., the gas atmosphere must be free of _H₂O , _CO₂ , and _O₂ ). Suitable inert gases include nitrogen and noble gases such as argon or helium. According to the present invention, two different process variants can be considered for the production of lithiated metal oxides:

1. Static process:

_A mixture of transition metal oxides and _Li₂O₂ is first heated to 280°C to 450°C in a corrosion-resistant tray or in bulk on a conveyor belt to cause thermal decomposition of the peroxides and release of _O₂ . This first reaction stage requires vacuum conditions or an inert gas atmosphere (i.e., a gas or gas mixture that does not react with the reactants and products (excluding _H₂O and _CO₂ ).

After the release of _O2 gas is completed, the temperature is raised to the temperature of 500℃ to 950℃ required to generate lithium transition metal oxide, and this reaction step is also carried out under vacuum conditions or in an oxygen-free inert gas atmosphere (i.e., an atmosphere without _H2O , _CO2 and _O2 ). Applicable inert gases include nitrogen and rare gases such as argon or helium. 2. Moving bed process:

This variant is preferably carried out continuously in a reactor that ensures mixing. The reactor preferably has two heatable rotary tubes that operate continuously in different temperature zones. The temperature range in the inlet zone of the raw material mixture is 280°C to 450°C, while the temperature level in the rear zone, i.e., the zone closer to the product outlet, is required to enable the lithium oxide formed in the first zone to undergo a synthesis reaction with at least one transition metal oxide to produce the desired lithium metal _oxide . In this case, the synthesis temperature range for _Li2NiO2 is 550°C to 950°C. To avoid undesirable oxidation of the transition metal oxide used at higher temperature levels (for example, from Ni(II) to Ni(III) or Ni(IV)), the high-temperature zone needs to have a reducing (i.e., oxygen-free) atmosphere. This can be achieved by passing a flow of oxygen-free inert gas through the reaction mixture in a countercurrent direction (i.e., in the opposite direction to the direction of motion of the moving bed of solids).

Both calcining steps are carried out in an apparatus whose surface facing the product is made of a material resistant to high temperatures and alkaline lithium salt corrosion. A variety of metal materials selected from high-temperature resistant Cr- and/or Al-containing materials can be used for this purpose. In particular, nickel-based alloys containing Cr and/or Al, austenitic steels containing Ni and Cr, and low-Ni or Ni-free, ferritic steels containing Cr and Al, as well as mixed austenitic-ferritic steels containing chromium can be used as container materials. In suitable alloys, the chromium content is at least 15 wt.%, preferably at least 20 wt.%, and particularly preferably at least 30 wt.%. In addition, when the Al content is at least 1 wt.%, the chromium content can be selected to be significantly lower (at least 5 wt.%). The preferred Al content is at least 1 wt.%, particularly preferably at least 2 wt.%. In addition to chromium and aluminum, the metal alloys suitable for the preparation method of the present invention may contain the elements niobium, titanium, tantalum, and/or silicon, in each case in a weight percentage of up to 10 wt.%. Low-Mo alloys are preferably used. The Mo content is less than 2 wt.%, preferably less than 1 wt.%.

The following commercially available metal materials are particularly suitable for this application:

Nickel-based alloys: Inconel 600, Inconel 601, Inconel 693, Inconel 702, Inconel 800, Inconel 825; Incoloy 901, Nickel-Chromium, Nickel-Chromium V, Nimonic 75, Nimonic 80A, Nimonic 90, RA602CA/Alloy 602 CA, Alloy X, and similar grades;

Austenitic steels: SS347 (1.4550), 253MA (1.4835), Nitronic 50, 310S, 316L, SS310, SS304, RA253MA, and similar steels;

Ferritic steels: Kanthal (e.g., Kanthal A1, Kanthal AF, Kanthal D (FeCrAl)), PM 2000, Incoloy MA 956, and similar steels.

Solid metal materials selected from the aforementioned material group and suitably coated, high-temperature-resistant black or stainless steel can be used in this case. The anti-corrosion coating on the product side contains at least 10 wt.%, preferably at least 30 wt.%, of chromium. Furthermore, it may contain the elements Ni, Fe, Nb, Al, Ti, Ta, and Si, each in an amount up to 10 wt.% by weight.

The thickness of the chromium-containing anti-corrosion coating is at least 5 μm, preferably at least 10 μm. The coating thickness can be determined using an electron microscope. For example, an austenitic steel (e.g., 1.4401) with only moderate corrosion resistance can have its corrosion resistance significantly improved by applying a 50 μm thick coating containing Cr and Al. This coating process can be accomplished using various electrochemical or physical techniques, such as the pack-cementation process (Kim, Mater. Transact. 43, 2002, 593).

In addition to the aforementioned metal materials, certain oxide ceramics (e.g., _Al₂O₃ , _lithium aluminate ceramics ( _LiAlO₂ ), or Ce-based ceramics, such as Ce-stabilized _ZrO₂ ) and non-oxide ceramics (e.g., carbides such as SiC, BC, and TiC; nitrides such as TiN and AlN; and borides such as NbB₂, BN, aluminized _TiB₂ , and "TiBAl") can also be used as container materials. Materials coated with the aforementioned ceramics (preferably _LiAlO₂ ), such as high-temperature steel, can also be used.

Carbon-based materials such as graphite (carbon graphite, hard carbon) and pure carbon with a disordered graphite structure and ceramic properties (glassy carbon) can be used to a limited extent in this context. However, the use of carbon-based materials in high-temperature calcination processes, i.e., temperatures above approximately 400°C, requires extremely carefully controlled inert gas conditions, i.e., the complete exclusion of oxidants (e.g., oxygen) or other oxygen donors (e.g., water or carbon dioxide). Because oxygen is released during the first reaction step, a certain amount of burnup is difficult to avoid over a longer period of time. Therefore, oxidation-stabilized graphite materials are preferred, as their burnup rate when exposed to ambient air is significantly lower than that of high-purity graphite, as used in (D.V. Savchenko, New Carbon Materials 2012, 27, 12-18). Graphite materials are high-temperature resistant materials produced through a filler/binder system. They are made from petroleum coke, asphalt coke, carbon black, and graphite. These materials are ground to a specified particle size distribution, mixed at high temperatures, formed and compacted into green bodies in a press, and then carbonized through a high-temperature pyrolysis process.

Carbon-based materials can be used to make solid reaction vessels, or they can be made into hollow bodies using graphite-coated or lined materials (e.g., metal tubes lined with graphite foil).

The lithium-ion battery cathode material is mixed with the lithium-ion battery cathode material for pre-lithiation and processing to form a positive electrode bar. As a component of the positive electrode, the lithium-ion battery cathode material decomposes and releases lithium during the first charge-discharge cycle.

Example

General Rules:

All manipulations of lithium raw materials (lithium peroxide and lithium oxide) were performed under inert conditions, i.e., in an argon-filled glove box.

The reaction products were characterized by powder diffraction (XRD) using a Bruker AXS D2 Phaser A26 instrument.

The specific surface area of the lithium compounds used was determined by gas adsorption according to the method of Stephen Brunauer, Paul Hugh Emmett and Edward Teller ("BET").

Example 1

Production of Li ₂ NiO ₂ from NiO and Li ₂ O ₂

In an Ar-filled glove box, 1.90 g (41.4 mmol) of lithium peroxide (97%, BET = 7.6 ^m² /g, Albemarle, Germany) and 3.09 g (41.4 mmol) of nickel(II) oxide (NiO green, catalog number SIAL399523-100G, Sigma Aldrich) were added, mixed and pre-ground in an agate mortar, and then ground together in a Fritsch planetary ball mill (Pulverisette 7 in an Easy GTM mill made of _ZrO² ). Twelve _ZrO² balls with a diameter of 10 mm were used to grind approximately 5 g of the powder mixture; the milling time was 2 hours at a rotational speed of 600 rpm. The resulting brown mixture was removed from the balls by sieving.

1.0 g of the milled mixture was filled into a Specac die and pressed into tablets under a contact pressure of 500 kg (equivalent to approximately 620 bar) for 15 minutes.

The tablets were then placed in an alumina crucible in a tubular furnace and calcined under a light nitrogen flow (20 L/h). The heated, nitrogen-filled furnace tube was made of quartz glass. Initially, the tube was heated to 300°C and held at this temperature for two hours. The furnace temperature was then increased. The temperature was then raised to 700°C over approximately 30 minutes and held at this temperature for 24 hours.

After cooling to room temperature, the crucible was placed in an air-free glove box. The tablets did not disintegrate and were black.

Yield: 0.87 g (weight loss 13.1%, equivalent to 99% of theoretical value).

XRD: The mixture contains Li ₂ NiO ₂ , 23 wt.%; NiO, 51 wt.%; Li 2 O, 26 wt.%.

Example 2 (Comparison example)

Production of Li ₂ NiO ₂ from NiO and Li ₂ O

In an Ar-filled glove box, 1.429 g (47.8 mmol) of lithium oxide (99%, BET = 2.4 m²/g, Albemarle, Germany) and 3.571 g (47.8 mmol) of nickel(II) oxide (NiO green, catalog number SIAL399523-100G, Sigma Aldrich) were mixed and pre-ground in an agate mortar and then ground together in a Fritsch planetary ball mill (Pulverisette 7 in an Easy GTM milling mortar made of _ZrO² ). Approximately 5 g of the powder mixture was ground using 12 ZrO² _balls with a diameter of 10 mm; the milling time was 2 hours at a rotational speed of 600 rpm. The resulting brownish-gray mixture was then sieved to remove the balls.

1.0 g of the milled mixture was filled into a Specac die and compressed into tablets under a contact pressure of 500 kg (equivalent to approximately 620 bar) for 15 minutes.

The tablets are then placed in an alumina crucible in a tubular furnace and calcined under a light nitrogen flow. The heated, nitrogen-flowing furnace tube is made of quartz glass. Initially, the tube is heated to 300°C and held at this temperature for two hours. The temperature is then raised to 700°C. Thereafter, the furnace temperature is raised to 700°C and held at this temperature for 24 hours.

After cooling to room temperature, the crucible was placed in an air-free glove box. The tablets did not disintegrate and appeared black.

Yield: 1.0 g (no appreciable weight loss).

XRD: The mixture contains Li ₂ NiO ₂ , 11 wt.%; NiO, 60 wt.%; Li 2 O, 29 wt.%.

Experiments have demonstrated that, through the controlled preparation method of this invention, the desired _{Li₂NiO₂ can be formed using Li₂O₂ ,} and the oxygen generated during the first calcination step does not change the oxidation number _of the _{NiO used. Surprisingly, the conversion rate when using Li₂O₂ is more} than double that observed when using _Li₂O .

The conversion rate can be further improved by optimizing the experimental conditions, especially by extending the calcination time.

without

without

Claims (15)

A method for preparing a lithium peroxide metal oxide is disclosed, comprising: a) mixing the lithium peroxide ( _{Li₂O₂ )} with the at least one transition metal oxide ( _{MaO₄ )} or the manganese-containing spinel compound to form a mixture; and b) calcining the mixture; wherein M in the transition metal oxide is selected from any one of Fe, Ni, Co, and Mn, the manganese _- containing spinel compound is selected from _LiMn₂O₄ or _LiNi₂O₄ , a is an integer from 1 to ₃ , and b is a number from 1 to ₄ ; and the mixture is calcined continuously at at least two consecutively different temperature ranges. The step b) includes a first temperature range of 280°C to 450°C and a second temperature range of 500°C to 950°C. The preparation method of claim 1, wherein the first temperature range is in the range of 300°C to 400°C, and the second temperature range is in the range of 600°C to 900°C. The preparation method as described in claim 1, wherein the calcination in the first temperature range and the second temperature range is carried out under a vacuum or an inert gas atmosphere, and the calcination in the second temperature range is carried out under the condition of excluding oxygen. The preparation method as described in claim 1, wherein the continuous calcination in at least two continuously different temperature ranges is carried out in the same reaction vessel, and time or space separation measures are used to ensure that the requirements are met in the at least two continuously different temperature ranges and atmosphere conditions. The preparation method of claim 1, wherein the lithium peroxide Li ₂ O ₂ used has a specific surface area of at least 1 m ² /g. The preparation method as described in claim 1, wherein the calcination is carried out in a reactor that is resistant to corrosion and high temperature. The preparation method as described in claim 1, wherein the preparation method is carried out under static conditions, wherein the mixture _of the transition metal oxide and the _Li2O2 is first heated to a temperature range of 280°C to 450°C in a corrosion-resistant shell _or as a block on a tape under vacuum conditions or in an inert gas atmosphere, wherein the thermal decomposition of the _Li2O2 occurs accompanied by the release of oxygen, and after the _{decomposition} of the _Li2O2 is completed, the temperature is increased to the temperature range of 500°C to 950°C required to form the lithiated metal oxide, while ensuring an oxygen-free atmosphere. The preparation method of claim 1, wherein the preparation method is carried out under moving bed conditions in a reactor to ensure continuous mixing of the reaction mixture. The preparation method as described in claim 8, wherein the reactor includes at least two heatable rotating tubes to operate continuously in different temperature zones, wherein the temperature range in the inlet area of the raw material mixture is 280°C to 450°C; and the temperature range in the rear area closer to the product discharge area is 500°C to 950°C, wherein in the temperature zone of 500°C to 950°C, appropriate conditions are set by introducing an inert gas or an inert gas mixture that is substantially free of _O2 , _CO2 and _H2O to form the lithium metal oxide. The preparation method of claim 1, wherein the mixing of the lithium peroxide and the at least one transition metal oxide is carried out in a rotary mixer with an energy input ranging from 100 kW/m ³ to 500 kW/m ³ or in a mill. The preparation method of claim 1, wherein the mixture consisting of the lithium peroxide and the at least one transition metal oxide or the manganese-containing spinel compound is compressed using a contact pressure in the range of 0.001 kbar to 100 kbar before the calcination. The preparation method of claim 1, wherein the transition metal oxide is selected from oxides of nickel, manganese, cobalt or iron. The preparation method of claim 1, wherein the Li ₂ O ₂ and the transition metal oxide have a mixed molar ratio ranging from 0.6:1 to 3:1. The preparation method as described in claim 1, wherein the lithium metal oxide is selected from Li _2+x FeO ₄ (0≦x≦3), Li _1+x NiO ₂ (0≦x≦1); Li _1+x CoO _1.5+0.5x (0≦x≦5); Li _1+x Mn ₂ O ₄ (0≦x≦1); Li _1+x Ni _0.5 Mn _1.5 O ₄ (0≦x≦1). The preparation method according to any one of claims 1 to 14, wherein the produced lithium-ion metal oxide is used for pre-lithiation in the production of lithium-ion batteries.