JP2003243030A - Non-aqueous electrolyte battery - Google Patents

Abstract

(57) [Problem] To prevent deterioration of charge / discharge cycle characteristics. A LOC battery (1) comprising a positive electrode (2), a negative electrode (4), and a non-aqueous electrolyte (7), wherein the non-aqueous electrolyte (7) has a higher charge potential than the potential at the time of deposition on the lithium metal negative electrode (4). The addition of an additive having an oxidation-reduction potential lower than the potential of the positive electrode 2 of the negative electrode 2 causes the additive to ionize lithium metal that has been deactivated on the negative electrode 4. Prevents deterioration of charge / discharge cycle characteristics due to deactivation of metal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte battery including a positive electrode, a negative electrode and a non-aqueous electrolyte, and having greatly improved battery characteristics.

[0002]

2. Description of the Related Art In recent years, for example, a notebook type portable computer, a mobile phone, a camera-integrated VTR (vide)
o tape recorders) and other portable electronic equipment power supplies,
Development of lightweight secondary batteries with high energy density is underway. As a secondary battery having this high energy density, lithium, a lithium alloy, or a carbon material capable of doping / dedoping lithium ions is used as a negative electrode active material, and a metal oxide or a metal sulfide is used on the positive electrode side. A lithium-ion secondary battery or the like used as the electrode active material is known. This lithium-ion secondary battery is widely used as a power source for various electronic devices because it has a larger energy density than lead batteries, nickel-cadmium batteries, and the like, and has little capacity deterioration due to repeated charging and discharging. ing.

In addition, as the above-mentioned portable electronic equipment has become more sophisticated and has higher power consumption, the power consumption increases, and a secondary battery using lithium metal having a larger capacity than a lithium ion secondary battery, so-called metallic lithium secondary battery. Practical application of batteries is expected. This metal lithium secondary battery has a problem that lithium is deposited on the negative electrode by repeating charging and discharging, and the deposited lithium is lost from the negative electrode, resulting in a decrease in battery capacity.

As a means for solving such a problem,
There is a lithium polymer secondary battery or the like that can physically prevent loss of lithium deposited on the negative electrode by including a lithium ion conductive polymer in the electrolyte.
It is also known to reduce the loss of lithium deposited on the negative electrode by using an ether-based electrolyte as the electrolyte.

Among the above-mentioned solutions, the former has a problem that the conductivity of the lithium ion conductive polymer contained in the electrolyte decreases at low temperature, and it is considered difficult to put it into practical use. . On the other hand, the latter is a vanadium-based positive electrode in which the battery capacity becomes small when the ether-based electrolytic solution uses lithium cobalt oxide, which can increase the battery capacity, as the positive electrode active material and is oxidized to the lithium cobalt oxide. Since an active material is used, it is difficult to obtain a high capacity battery. Therefore, lithium metal is mainly used as an electrode of a primary battery, not a secondary battery.

[0006]

By the way, recently, by using the above-mentioned lithium ion secondary battery as a battery for further improving the battery capacity, by depositing lithium metal on a negative electrode using a carbonaceous material as an active material, Lithium On Carbon (hereinafter referred to as LO), which can be used as the battery capacity by combining the capacity of the active material and the capacity of the deposited lithium metal
It is written as C. Batteries have been proposed. This LOC battery can have a significantly larger battery capacity than a lithium ion secondary battery.

However, this LOC battery has a problem that the discharge capacity retention rate after repeated charging and discharging becomes smaller than that of the lithium ion secondary battery. In this LOC battery, as shown in FIG.
When the lithium metal 101 deposited on the anode 0 is discharged, the lithium metal 101 is ionized from the side closer to the surface of the negative electrode 100, and the lithium metal 101 closer to the surface of the negative electrode 100 is sequentially dissolved. Become. For this reason,
A space 102 is formed between the negative electrode 100 and the lithium metal 101 farther from the surface of the negative electrode 100, and the space 102 causes the lithium metal 101 farther from the surface of the negative electrode 100 to be in an insulating state and lost. Since it becomes the activated lithium metal 101a, the deactivated lithium metal 101a does not contribute to the charge and discharge, and the discharge capacity decreases as the charge and discharge are repeated.

Therefore, the present invention has been proposed in view of such a conventional situation, and makes it possible to prevent deterioration of charge / discharge cycle characteristics such as a decrease in discharge capacity with repeated charge / discharge. The purpose of the present invention is to provide a non-aqueous electrolyte battery.

[0009]

A non-aqueous electrolyte battery according to the present invention comprises a positive electrode having an active material containing lithium, and doping / dedoping metal in an ionic state and / or depositing / eluting metal. A negative electrode having an active material capable of
A non-aqueous electrolyte battery comprising a non-aqueous electrolyte containing an electrolyte salt, the non-aqueous electrolyte has a redox potential nobler than the potential when deposited on a metal negative electrode, and has a positive electrode active material in a charged state. It is characterized in that an additive whose redox potential is lower than the potential is added.

This non-aqueous electrolyte battery comprises a non-aqueous electrolyte,
An additive having a redox potential higher than the potential of the metal when deposited on the negative electrode and lower than the potential of the positive electrode active material in the charged state is added. As a result, in this non-aqueous electrolyte battery, when the metal deposited on the negative electrode is in a state where it does not contribute to charging and discharging due to being insulated from the negative electrode, the additive oxidizes the metal that does not contribute to charging and discharging. While being ionized, the positive electrode active material in the charged state oxidizes the additive reduced by the metal that does not contribute to charge and discharge, and again makes the redox potential of the additive higher than the potential of the metal deposited on the negative electrode.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the non-aqueous electrolyte battery according to the present invention will be described in detail below with reference to the drawings.

In the non-aqueous electrolyte battery to which the present invention is applied, light metal begins to deposit on the negative electrode at the time when the open circuit voltage (battery voltage) is lower than the overcharge voltage during the charging process. That is, in this non-aqueous electrolyte battery, the light metal is deposited on the negative electrode when the open circuit voltage is lower than the overcharge voltage, and the capacity of the negative electrode is the capacity component obtained when the light metal is occluded and released in the ionic state. And the capacity component obtained when the light metal is deposited and dissolved. That is, in this non-aqueous electrolyte battery, in the process of charging, light metal begins to deposit on the negative electrode at a time point when the open circuit voltage (battery voltage) is lower than the overcharge voltage,
It is a so-called LOC (Lithium On Carbon) battery. The details will be described later.

FIG. 1 shows a constitutional example of a non-aqueous electrolyte secondary battery using lithium as a light metal. Non-aqueous electrolyte secondary battery to which the present invention is applied (hereinafter referred to as battery) 1
Is a positive electrode 2, a positive electrode can 3 containing the positive electrode 2, and a negative electrode 4.
A negative electrode can 5 accommodating the negative electrode 4, a separator 6 interposed between the positive electrode 2 and the negative electrode 4, a non-aqueous electrolyte solution 7,
It has a gasket 8. In the battery 1, the positive electrode can 3 and the negative electrode can 5 are caulked with the gasket 8 interposed therebetween, so that the positive electrode 2, the negative electrode 4, the separator 6, the non-aqueous electrolyte solution 7 are discharged into the positive electrode can 3 and the negative electrode can 5. The structure is enclosed by.

The positive electrode 2 comprises a positive electrode current collector 2a and a positive electrode mixture layer 2b containing a positive electrode active material formed thereon. For the positive electrode current collector 3a, a thin metal such as aluminum or a mesh metal is used. The positive electrode mixture layer 3b is configured to contain, for example, a positive electrode active material, a conductive agent such as graphite or carbon black, and a binder such as polyvinylidene fluoride.

As the positive electrode active material, a compound containing lithium, which is a light metal, such as a lithium oxide, a lithium sulfide, or an intercalation compound containing lithium, is used alone or in combination. In particular, when increasing the energy density, the positive electrode active material may be Li _x M.
It is preferable to contain a lithium composite oxide mainly containing O ₂ . In addition, M is one or more kinds of transition metals. Specifically, M is cobalt (Co), nickel (N
i), manganese (Mn), iron (Fe), aluminum (Al), vanadium (V), and titanium (Ti). Also,
x depends on the charge / discharge state of the battery and is usually 0.0
The range is 5 or more and 1.10 or less. Specific examples of such a lithium composite oxide include Li _x CoO ₂ and Li.
_{x NiO 2, Li x Ni y} Co 1-y O 2 ( where these are wherein x ≒ 1,0 <y <1), and the like.
Further, as a lithium composite oxide, Li _x Mn ₂ O ₄ having a spinel structure, and Li _x FeP having an olivine structure.
It is also possible to use O ₄ . In addition, for example, sulfide such as titanium sulfide or molybdenum sulfide, or conductive polymer such as polyaniline or polythiophene can be used by incorporating lithium.

Such a lithium composite oxide is
For example, lithium carbonate, nitrate, oxide or hydroxide and transition metal carbonate, nitrate, oxide, sulfide or hydroxide are mixed to have a desired composition, and after pulverization, It is synthesized by firing at a temperature in the range of 600 to 1000 ° C. in an oxygen atmosphere.

From the standpoint of increasing the charge / discharge capacity, the positive electrode mixture layer 3b has a charge of at least 280 mAh / g of the negative electrode active material in a steady state (for example, after repeating charge / discharge about 5 times). It is preferable to contain lithium in an amount corresponding to the discharge capacity. Also, 350
It is more preferable to contain lithium corresponding to a charge / discharge capacity of mAh or more. However, this lithium does not necessarily have to be entirely supplied from the positive electrode mixture layer 3b, that is, the positive electrode 2, and may be present in the entire battery. For example, it is possible to replenish the lithium in the battery by bonding lithium metal or the like to the negative electrode 4. The amount of lithium in the battery is quantified by measuring the discharge capacity of the battery. The positive electrode mixture layer 3b may further contain a metal carbonate such as lithium carbonate (Li ₂ CO ₃ ). When the metal carbonate is contained as described above, the cycle characteristics can be further improved. this is,
This is because the metal carbonate is partially decomposed in the positive electrode 2 to form a stable coating film on the negative electrode 4.

The positive electrode can 3 is a dish having a shallow bottom, which is a so-called petri dish container for accommodating the positive electrode 2. For example, when the positive electrode 2 is accommodated, aluminum, stainless steel, and nickel are sequentially laminated from the inside in the thickness direction. It is configured and serves as an external positive electrode of the battery 1.

The negative electrode 4 is formed by forming a negative electrode mixture layer 4b containing a positive electrode active material on a negative electrode current collector 4a. For the negative electrode current collector 4a, for example, a thin metal such as copper or a mesh metal is used. The negative electrode mixture layer 4b is configured to include, for example, a negative electrode active material capable of doping / dedoping a light metal in an ionic state as a negative electrode active material. Negative electrode mixture layer 4b
For example, the negative electrode active material and a binder such as polyvinylidene fluoride or polytetrafluoroethylene are contained.

Here, specific light metals include lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and alloys containing them. Above all, from the viewpoint of ensuring compatibility with existing lithium ion secondary batteries, it is preferable to use lithium or an alloy containing lithium as the light metal. Further, as a light metal, an element capable of forming an alloy with lithium is aluminum (Al), zinc (Zn), lead (Pb), tin (Sn), bismuth (B).
i), cadmium (Cd) and the like.

Storage of light metal in the ionic state means that the light metal exists in the ionic state, as represented by an electrochemical intercalation reaction of the light metal ion with respect to graphite. It is a concept different from precipitation. In the following description, in order to simplify the description, occluding and desorbing light metal lithium in an ionic state may be simply referred to as light metal doping / dedoping. As such a negative electrode active material,
For example, a carbonaceous material, a metal compound, a lithium nitride such as LiN ₃ , or a polymer material can be used, and any one or a plurality of these materials can be mixed and used.

In the negative electrode active material, examples of carbonaceous materials include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, and carbon. Examples include fibers and activated carbon. Among these, the cokes include pitch coke, needle coke, petroleum coke, and the like. The organic polymer compound fired body is obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature to carbonize it, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as. Further, as the metal compound,
An oxide such as SnSiO ₃ or SnO ₂ , Mg ₂
Examples thereof include compounds containing elements such as Si such as Si, Sn, Mg, Cu, Pb, and Cd, and examples of polymer materials include polyacetylene and polypyrrole.

As such a negative electrode active material, one having a charge / discharge potential relatively close to that of lithium metal is preferable. This is because the lower the charging / discharging potential of the negative electrode 4, the easier the energy density of the battery can be increased. Among them, carbonaceous materials are
This is preferable because the change in the crystal structure that occurs during charge and discharge is extremely small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained. Particularly, graphite has a large electrochemical equivalent and can obtain a high energy density. Further, non-graphitizable carbon can obtain excellent cycle characteristics.

As the graphite, for example, the true density is 2.10.
g / cm ³ or more is preferable, 2.18 g / cm ³
The above is more preferable. To obtain such a true density, the C-axis crystallite thickness of the (002) plane is 14.
It must be 0 nm or more. Also, (002)
It is more preferable that the surface spacing is less than 0.340 nm and the range is 0.335 nm or more and 0.337 nm or less. The non-graphitizable carbon has a (002) plane spacing of 0.37 nm or more and a true density of 1.70 g / c.
m ³ and a differential thermal analysis in air (differ
700 ° C in the critical thermal analysis (DTA)
Those that do not exhibit the exothermic peak are preferable.

Of these, the graphite may be natural graphite or artificial graphite. The artificial graphite can be obtained, for example, by carbonizing an organic material, subjecting it to high-temperature heat treatment, and crushing and classifying. The high temperature heat treatment may be carried out by, for example, nitrogen (N
₂ ) 300 ℃ -700 ℃ in an inert gas stream
Carbonized at 900 ℃ ~ 15 at a rate of 1 ℃ ~ 100 ℃ / min
The temperature is raised to 00 ° C., and this temperature is maintained for about 0 to 30 hours for calcination and 2000 ° C. or more, preferably 2
It is performed by heating to 500 ° C. or higher and maintaining this temperature for an appropriate time.

Coal or pitch can be used as the starting organic material. Pitch includes, for example, coal tar, tars obtained by thermally decomposing ethylene bottom oil or crude oil at high temperature, asphalt, etc. by distillation (vacuum distillation, atmospheric distillation or steam distillation), thermal polycondensation, extraction, There are those obtained by chemical polycondensation, those produced when wood is refluxed, polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate or 3,5-dimethylphenol resin. These coals or pitches exist as a liquid at a maximum temperature of about 400 ° C during carbonization, and by being held at that temperature, aromatic rings are condensed and polycyclic, and become in a laminated orientation state, and then about 500 ° C or higher. To form a solid carbon precursor, that is, semi-coke.

Examples of the organic material include condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphene, pentacene and the like or derivatives thereof (for example, carboxylic acid and carboxylic acid anhydride of the above compounds, Carboxylic imide), or a mixture thereof or the like is used. Furthermore, a condensed heterocyclic compound such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine, or a derivative thereof, or a mixture thereof can be used.

In order to produce artificial graphite using the above-mentioned organic material as a starting material, for example, the organic material is carbonized at a temperature of 300 ° C. to 700 ° C. in an inert gas stream such as nitrogen, and then an inert gas stream is obtained. Medium, heating rate 1 ° C-1000 / min
℃, the ultimate temperature 900 ℃ ~ 1500 ℃, calcination under the conditions of the ultimate temperature holding time 0 ~ 30 hours, further temperature 20
Heat treatment is performed at 00 ° C. or higher, preferably 2500 ° C. or higher.
However, in some cases, the carbonization and calcination operations may be omitted. In this way, graphite is produced. Then, the generated graphite is classified or pulverized and classified to be used as a negative electrode active material.

The negative electrode 4 may contain lithium metal or lithium alloy as the negative electrode active material of the negative electrode mixture layer 4b, and although not shown, separately from the negative electrode mixture layer 4b, lithium metal or lithium alloy. The negative electrode 4 may have a metal layer made of

The negative electrode can 5 is a dish-shaped container for housing the negative electrode 4, and is made of, for example, stainless steel, iron with nickel plated on its surface, or the like, and serves as an external negative electrode of the battery 1.

The separator 6 separates the positive electrode 2 and the negative electrode 4 from each other and allows lithium ions in the electrolytic solution to pass through while preventing a short circuit of current due to contact between both electrodes. The separator 6 is made of a microporous film having a large number of minute holes.
Here, the microporous film is a resin film having a large number of micropores having an average pore diameter of about 5 μm or less. As the material of the separator 6, it is possible to use a material that has been used in a conventional battery as a material. Among them, a microporous film made of polypropylene, polyolefin, or the like, which has an excellent short circuit prevention effect and which can improve battery safety by a shutdown effect, is used.

The separator 6 has a thickness of 5 μm or more,
It is in the range of 50 μm or less, and the porosity indicating the ratio of void volume in the entire volume is 20% or more, 6
It is set to a range of 0% or less. With the separator 6 that meets such conditions, it is possible to obtain the battery 1 having excellent manufacturing yield, output characteristics, cycle characteristics, and safety.

In the battery 1 according to the present invention, as shown in FIG. 2, the non-aqueous electrolyte solution 7 composed of the electrolyte salt and the non-aqueous solvent is more than the potential when the lithium metal 9 as a light metal is deposited on the negative electrode 4. Positive electrode 2 with a high redox potential and in a charged state
Additive 10 having an oxidation-reduction potential lower than that of No. 3 is added. Note that FIG. 2 shows a case where a carbonaceous material is used as the negative electrode active material, lithium cobalt oxide is used as the positive electrode active material, and lithium iodide is used as the additive 10. Further, an arrow A in the figure shows an oxidation reaction with respect to the deactivated metal lithium 9a by the additive 10, and an arrow B in the figure shows an oxidation reaction with respect to the additive in a reduced state by the positive electrode 2 in the charged state. .

By adding such an additive 10 to the non-aqueous electrolyte solution 7, for example, the lithium metal 9a deposited on the negative electrode 4 becomes in an insulating state and cannot contribute to charge / discharge, that is, deactivation. Lithium metal 9
When it becomes a, the lithium metal 9 in which the additive 10 is deactivated
By oxidizing a to ionize a, the deactivated lithium metal 9a can be contributed again to charge and discharge.
Then, the positive electrode 2 in the charged state is the deactivated lithium metal 9
Since the additive 10 reduced by a is oxidized, the redox potential of the additive 10 becomes higher than the potential of the lithium metal 9 deposited on the negative electrode 4, and the additive 10 is oxidized again to the deactivated lithium metal 9a. Will be used.
That is, the additive 10 itself is the lithium metal 9a.
It is a so-called redox agent that is reduced when it is oxidized or is oxidized by the positive electrode 2 in a charged state.

For example, as shown in FIG.
When lithium iodide is used as the material, the redox potential of the additive 10 is in the range of 0.1 V or more and 1.1 V or less. This is because the potential for depositing the lithium metal 9 on the negative electrode 4 is 0.0 V.
This is because the potential on the positive electrode 2 side where the positive electrode active material in the charged state is lithium cobalt oxide is 4.2V.

The additive 10 added to the non-aqueous electrolytic solution 7 has the above-mentioned oxidation-reduction potential and reacts with a non-aqueous solvent, an irreversible oxidation reaction in the positive electrode 2, and the negative electrode 4.
What is soluble in the non-aqueous electrolyte solution 7 in the oxidized state and the reduced state without being decomposed by the irreversible reduction reaction in 1.

Specifically, the additive 10 includes, for example, iodide ions (I ⁻ ) and bromide ions (B) as inorganic substances.
r ⁻ ), chloride ion (Cl ⁻ ), cyanide ion (CN ⁻ ), thiocyanate ion (NCS ⁻ ), and the like, and any one or more of them are used.
In addition, the additive 10 contains a thiolate (R ₂ such as ethanethiolate ion (C ₂ H ₅ S ⁻ ) as an organic substance.
S ⁻ , provided that R is an alkyl group or an aryl group. ),
A pyridinium salt represented by Chemical Formula 1, a bipyrimium salt represented by Chemical Formula 2, pyridines such as pyridine represented by Chemical Formula 3 and quinoline represented by Chemical Formula 4, bipyridines such as phenanthroline represented by Chemical Formula 5, parabenzoquinone represented by Chemical Formula 6, and naphthoquinone represented by Chemical Formula 7. And quinones such as anthraquinone represented by the chemical formula 8, tetracyanoquinodimethane represented by the chemical formula 9, tetracyanoethylene represented by the chemical formula 10, alkyl-substituted compounds, and the like.
Any one or more of these are used.

[0038]

[Chemical 1]

[0039]

[Chemical 2]

[0040]

[Chemical 3]

[0041]

[Chemical 4]

[0042]

[Chemical 5]

[0043]

[Chemical 6]

[0044]

[Chemical 7]

[0045]

[Chemical 8]

[0046]

[Chemical 9]

[0047]

[Chemical 10]

The additive 10 as described above is used in the non-aqueous electrolytic solution 7
It is added in the range of 100 ppm or more and 3000 ppm or less. When the amount of the additive 10 added to the non-aqueous electrolyte solution 7 is less than 100 ppm, the amount of the additive 10 added to the non-aqueous electrolyte solution 7 is too small.
It becomes difficult to properly ionize the deactivated lithium metal 9a to contribute to the charge and discharge again, and reduce the battery capacity. On the other hand, when the amount of the additive 10 added to the non-aqueous electrolyte solution 7 is more than 3000 ppm, a problem such as a decrease in discharge capacity due to self-discharge occurs. Therefore, the additive 10 is appropriately added to the nonaqueous electrolytic solution in the range of 100 ppm or more and 3000 ppm or less to appropriately ionize the deactivated lithium metal 9a on the negative electrode 4 and to deactivate the deactivated lithium metal. Even if it is reduced by 9a, it will be used again for the oxidation of the deactivated lithium metal 9a that is oxidized by the charged positive electrode 2.

The non-aqueous electrolytic solution 7 is a non-aqueous solvent in which a lithium salt is dissolved as an electrolyte salt. The non-aqueous solvent has an intrinsic viscosity of 10.0 mP at 25 ° C., for example.
It means a non-aqueous compound having a.s or less. This non-aqueous solvent is, for example, ethylene carbonate (E).
C) and propylene carbonate
e: PC). As a result, cycle characteristics can be improved. Particularly, it is preferable to use EC and PC as a mixture, because the cycle characteristics can be further improved.

When graphite is used as the negative electrode active material,
The concentration of PC in the non-aqueous solvent is set to less than 30% by mass. This is because PC has a relatively high reactivity with graphite, and therefore there is a possibility that the characteristics may deteriorate if the PC concentration is too high. When the non-aqueous solvent contains EC and PC, the mixed mass ratio of EC to PC in the non-aqueous solvent (EC / PC), that is, the value obtained by dividing the EC content by the PC content is 0.5 or more. It is preferable that Examples of the non-aqueous solvent include PC and EC, as well as diethyl carbonate and dimethyl carbonate (DM).
C), ethyl methyl carbo
nate; EMC) or a chain carbonic acid ester such as methyl propyl carbonate, or the like, or any one or more of them may be mixed. This makes it possible to further improve the cycle characteristics.

Further, examples of the non-aqueous solvent include butylene carbonate, γ-butyrolactone, γ-valerolactone,
Or those obtained by substituting a part or all of hydrogen groups of these compounds with fluorine groups, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3
-Dioxolane, tetrahydropyran, 1,3-dioxane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3
-Methoxypropyronitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide or trimethyl phosphate, etc. You may contain any 1 type or multiple types.

Examples of the lithium salt include LiPF ₆ ,
LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C
₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , L
_{iN (CF 3 SO 2) 2} , LiN (C 2 F 5 S
O ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiAlC
Any one kind or a plurality of kinds of l ₄ , LiSiF ₆ , LiCl, LiBr and the like is mixed and used. Above all, L
iPF ₆ can obtain high ionic conductivity and can further improve the cycle characteristics. The concentration of the lithium salt in the non-aqueous solvent is not particularly limited, but is in the range of 0.1 mol / liter or more and 5.0 mol / liter or less, more preferably 0.5 mol / liter or more, 3.0 or less. It should be in the range of mol / liter or less. By setting the concentration range as described above, the ionic conductivity of the non-aqueous electrolyte solution 7 can be increased.

The gasket 8 is made of, for example, an insulating resin such as polypropylene, and insulates the positive electrode can 3 and the negative electrode can 5 from each other, and the surface is coated with asphalt or the like to be in a sealed state. The airtightness inside the battery is maintained.

The battery 1 having the above structure operates as follows. In this battery 1, when charged, lithium ions are dedoped from the positive electrode active material contained in the positive electrode mixture layer 2b of the positive electrode 2, pass through the separator 6 via the non-aqueous electrolyte solution 7, and the negative electrode 4 is charged. The negative electrode active material contained in the negative electrode mixture layer 4b is doped. When the charging is further continued, when the open circuit voltage is lower than the overcharge voltage, the charging capacity exceeds the charging capacity of the negative electrode active material, and lithium metal 9 begins to deposit on the surface of the negative electrode 4. Specifically, depending on the electrode active material, the open circuit voltage of the battery 1 is 0 V or higher,
At any point within the range of 4.2 V or less, lithium metal 9 starts to be deposited on the surface of the negative electrode 4. After that, lithium metal 9 continues to be deposited on the negative electrode 4 when the open circuit voltage of the battery 1 reaches, for example, 4.2 V, that is, until charging is completed. As a result, the appearance of the negative electrode 4 changes from black to golden and then silver when a carbonaceous material is used as the negative electrode active material.

Next, in the battery 1, when discharged, the negative electrode 4
The lithium metal 9 deposited in the solution is dissolved as ions, passes through the separator 6 through the non-aqueous electrolyte solution 7, and is doped into the positive electrode active material contained in the positive electrode mixture layer 2a of the positive electrode 2.
When the discharge is further continued, lithium ions doped in the negative electrode active material contained in the negative electrode mixture layer 4a of the negative electrode 4 are released and doped in the positive electrode active material.

The overcharge voltage here means an open circuit voltage when the battery 1 is in an overcharged state, and is one of the guidelines set by the Japan Storage Battery Industry Association (Battery Industry Association), for example. Lithium Secondary Battery Safety Evaluation Standard Guidelines "(S
B G1101), page 6 and defined,
Refers to a voltage higher than the open circuit voltage of a "fully charged" battery. In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, the standard charging method, or the recommended charging method used when the nominal capacity of each battery is obtained. Specifically, in this battery 1, for example, the battery is fully charged when the open circuit voltage is 4.2 V, and the lithium metal 9 is formed on the surface of the negative electrode 4 in a part of the range where the open circuit voltage is 0 V or more and 4.2 V or less. It has been deposited.

Therefore, when the negative electrode 4 in the fully charged state is measured by, for example, the Li multi-nuclide nuclear magnetic resonance spectroscopy, a peak attributed to the lithium ion and a peak attributed to the lithium metal 9 are obtained. On the other hand, in the completely discharged negative electrode 4, the peaks attributed to lithium ions are obtained, but the peaks attributed to lithium metal 9 disappear. The complete discharge corresponds to the case where the electrode reactive species from the negative electrode 4 to the positive electrode 2, that is, the supply of lithium ions is stopped. For example, in the case of the battery 1 or the lithium-ion secondary battery according to the present embodiment, it is considered to be “fully discharged” when the closed circuit voltage reaches about 2.75V.

As a result, in the battery 1, a high energy density can be obtained, and the charge / discharge cycle characteristics and the quick charge characteristics can be improved. This is the same as the lithium secondary battery using lithium metal or a lithium alloy in the negative electrode 4 in that the lithium metal 9 is deposited on the negative electrode 4, but the lithium metal 9 is deposited on the negative electrode 4. This is because the following advantages will occur.

In this battery 1, the surface area of the negative electrode active material made of, for example, a carbonaceous material is generally larger than that of a conventional lithium secondary battery in which it is difficult to uniformly deposit lithium metal. The lithium metal 9 can be uniformly deposited on the surface 4. In this battery 1, compared with a conventional lithium secondary battery, which is said to have a large volume change due to charge and discharge of the lithium metal used for the negative electrode, for example, even in the gaps between the particles of the negative electrode active material made of a carbonaceous material or the like. Since the lithium metal 9 is deposited, the volume change on the negative electrode 4 side can be reduced. As a result, in the battery 1, deterioration of charge / discharge cycle characteristics is prevented.

Further, in this battery 1, the above problems become more serious as the battery capacity increases, but doping / dedoping of lithium ions in the negative electrode active material also contributes to the charge / discharge capacity, so that the battery capacity is large. Can reduce the precipitation of the lithium metal 9 and suppress the volume change on the negative electrode 4 side.

Furthermore, in this battery 1, compared with the conventional lithium secondary battery in which the lithium metal may be unevenly deposited on the negative electrode and the charge / discharge cycle characteristics may be further deteriorated when the battery is rapidly charged, Since lithium ions are doped into the negative electrode active material at the initial stage of charging, rapid charging is possible and deterioration of charge / discharge cycle characteristics due to rapid charging can be prevented.

Therefore, in this battery 1, the negative electrode active material is doped with lithium ions in the negative electrode 4 in the initial stage of charging, and lithium is formed on the surface of the negative electrode active material in the negative electrode 4 during the charging process when the open circuit voltage is lower than the overcharge voltage. Since the metal 9 is deposited, the characteristics of both so-called metallic lithium secondary battery and lithium ion secondary battery can be obtained. That is,
In this battery 1, a high energy density is obtained, and charge / discharge cycle characteristics and quick charge characteristics are improved.

In the negative electrode of the non-aqueous electrolyte battery described above, when the negative electrode is discharged from the negative electrode on which lithium metal is deposited, the lithium metal is ionized from the side closer to the negative electrode surface, and Lithium metal in the nearer direction will be sequentially dissolved. From this,
A space is created between the negative electrode and the lithium metal far from the negative electrode surface, and this space causes the lithium metal far from the negative electrode surface to become an insulating state and deactivate, so that the deactivated lithium metal is charged. It will not contribute to the discharge, and the electric capacity and other extreme capacity deterioration will occur. That is, the deactivated lithium metal on these negative electrodes is the main cause of deterioration of charge / discharge cycle characteristics in the non-aqueous electrolyte battery according to the present invention.

Therefore, in consideration of the above-mentioned mechanism of capacity deterioration, and a thorough investigation on a method of improving it,
In the battery 1, the oxidation-reduction potential is higher than the potential when the lithium metal 9 is deposited on the negative electrode 4 in the non-aqueous electrolyte solution 7,
In addition, the addition of the additive 10 having a redox potential less base than the potential of the positive electrode 2 in the charged state can prevent deterioration of the charge / discharge cycle.

As a result, in the battery 1, the additive 10
However, the lithium metal 9a deposited on the deactivated negative electrode 4 is oxidized to be ionized, and is again converted into lithium ions that contribute to charge and discharge. Then, the negative electrode 3 in the charged state oxidizes the additive 10 reduced by the deactivated lithium metal 9a to make the redox potential of the additive 10 higher than the potential of the lithium metal 9 deposited on the negative electrode 4. Therefore, the additive 10 is used again for the oxidation of the deactivated lithium metal 9a.

Therefore, in the battery 1, since the additive 10 deposits on the negative electrode 4 by repeating charge and discharge and deactivates the deactivated lithium metal 9a again to form lithium ions that can contribute to charge and discharge, the negative electrode 4 Since the deactivated lithium metal 9a is not stored, it is possible to prevent the deactivation of the lithium metal 9 from lowering the battery capacity and deteriorating the charge / discharge cycle characteristics.

Then, such a battery 1 is manufactured as follows. The positive electrode 2 is obtained by uniformly applying a positive electrode mixture coating liquid containing a positive electrode active material, a conductive material, and a binder onto a metal foil such as an aluminum foil, which will be the positive electrode current collector 2a, and drying the positive electrode mixture. The positive electrode 2 is produced by forming the agent layer 2b and cutting out the positive electrode current collector 2a and the positive electrode mixture layer 2b in a predetermined shape at once. In the positive electrode 2, as the binder used in the positive electrode mixture layer 2b, known binders such as polyvinylidene fluoride, polytetrafluoroethylene, and styrene butadiene rubber can be used.
Known additives and the like can be added to the positive electrode mixture layer 2b.

For the negative electrode 4, a negative electrode mixture coating liquid containing a negative electrode active material and a binder is uniformly applied onto a metal foil such as a copper foil, which will be the negative electrode current collector 4a, and dried to form a negative electrode mixture. The agent layer 4b is formed, and the negative electrode current collector 4a and the negative electrode mixture layer 4b are formed in a predetermined shape.
The negative electrode 4 is manufactured by cutting out all at once. In the negative electrode 4, known binders such as polyvinylidene fluoride, polytetrafluoroethylene, and styrene butadiene rubber can be used as the binder used in the negative electrode mixture layer 4b, and also known in the negative electrode mixture layer 4b. Additives and the like can be added.

Next, the electrolyte is dissolved in a non-aqueous solvent and the additive 10 is added to prepare the non-aqueous electrolytic solution 7. Next, the positive electrode 2 is accommodated in the positive electrode can 3, the negative electrode 4 is accommodated in the negative electrode can 5, and the separator 6 made of a polypropylene porous film or the like is disposed between the positive electrode 2 and the negative electrode 4. As a result, the battery 1 has a structure in which the positive electrode 2, the separator 6, and the negative electrode 4 are sequentially stacked.

Next, the non-aqueous electrolyte solution 7 is poured into the positive electrode can 3 and the negative electrode can 5, and the positive electrode can 3 and the negative electrode can 5 are fixed by caulking with the gasket 8 having the surface coated with asphalt or the like. To do. In this way, the coin type battery 1 is manufactured.

In the battery 1 described above, for example, a notebook type portable computer, a mobile phone, a camera-integrated VT
When used in portable electronic devices such as R (video tape recorder), electric vehicles, electrically assisted bicycles, etc., they have better charge / discharge cycle characteristics than conventional lithium secondary batteries. It becomes possible to mount the battery in a state where the usable time is extended and the energy density is increased. Further, since the battery 1 has good charge / discharge cycle characteristics, the life of electronic devices and the like due to deterioration of battery characteristics can be extended, and resource saving and cost reduction can be achieved.

In the above-described embodiment, the coin-type battery is given as an example of the non-aqueous electrolyte battery according to the present invention, but the present invention is not limited to this, and for example, a cylindrical shape, a rectangular shape, It is applicable to non-aqueous electrolyte batteries of various shapes such as button type. Further, in the above-described embodiment, the LOC battery is given as an example of the non-aqueous electrolyte battery according to the present invention, but the present invention is not limited to this. For example, a metal lithium secondary battery, a lithium ion secondary battery. It is also applicable to batteries, lead secondary batteries, magnesium secondary batteries, aluminum secondary batteries, zinc secondary batteries and the like.

[0073]

EXAMPLE An example in which a coin type LOC (Lithium On Carbon) battery is actually manufactured as a non-aqueous electrolyte battery to which the present invention is applied will be described below. A comparative example prepared for comparison with these examples will be described.

Example 1 First, 90 parts by weight of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 6 parts by weight of graphite as a conductive material, and polyvinylidene fluoride (PVdF) as a binder. 4 parts by weight were uniformly mixed to obtain a positive electrode mixture coating liquid. Next, the obtained positive electrode mixture coating liquid is uniformly applied onto an aluminum foil having a thickness of 10 μm to be a positive electrode current collector and dried to form a positive electrode mixture layer, and the positive electrode current collector and the positive electrode current collector are formed into a predetermined shape. The positive electrode material mixture layer is punched together to have a diameter of 15 mm and a thickness of 0.0865 m.
A m-shaped positive electrode was produced.

Next, 90 parts by weight of graphite as a negative electrode active material and 10 parts by weight of PVdF as a binder were homogeneously mixed to obtain a negative electrode mixture coating liquid. Next, the obtained negative electrode mixture coating liquid and a 10 μm-thick copper foil serving as a negative electrode current collector are uniformly applied and dried to form a negative electrode mixture layer, and the negative electrode current collector and the negative electrode are formed into a predetermined shape. The mixture layer was punched out at once to prepare a disk-shaped negative electrode having a diameter of 15 mm and a thickness of 0.056 mm.

Next, L was added to a solvent prepared by mixing ethylene carbonate and propylene carbonate in equal volumes.
A non-aqueous electrolyte was prepared by dissolving iPF ₆ at a concentration of 0.6 mol / liter. And in this non-aqueous electrolyte,
In a LOC battery, lithium iodide is added as an additive having a redox potential higher than that at the time of depositing lithium metal on the negative electrode and lower than the potential of the positive electrode in a charged state, and the addition amount to the non-aqueous electrolyte is 100 ppm Was added.

The positive electrode obtained as described above is housed in a positive electrode can made by stacking aluminum, stainless steel, and nickel in this order from the inside, and the negative electrode is housed in a negative electrode can made of stainless steel. Then, a separator made of a microporous polypropylene film having a thickness of 25 μm was laminated and arranged.

Next, a non-aqueous electrolytic solution was injected into the positive electrode can and the negative electrode can, and the positive electrode can and the negative electrode can were caulked and fixed through a gasket made of polypropylene to fix the battery capacity depending on the negative electrode active material. Is 3.3 mAh, the battery capacity depends on the lithium metal deposited on the negative electrode is 2.2 mAh, and the coin type LOC has a diameter of 20 mm and a thickness of 1.6 mm.
A battery was made. In the following description, for convenience, the LO
The C battery is simply referred to as a battery.

<Example 2> In Example 2, a battery was produced in the same manner as in Example 1 except that the additive was added so that the amount of the additive added to the non-aqueous electrolyte was 1000 ppm.

<Example 3> In Example 3, a battery was produced in the same manner as in Example 1, except that the additive was added so that the amount of the additive added to the non-aqueous electrolyte was 2000 ppm.

<Example 4> In Example 4, a battery was prepared in the same manner as in Example 1 except that the additive was added so that the amount of the additive added to the non-aqueous electrolyte was 3000 ppm.

Comparative Example 1 In Comparative Example 1, a battery was manufactured in the same manner as in Example 1 except that the additive was not added to the non-aqueous electrolyte.

<Comparative Example 2> In Comparative Example 2, a battery was produced in the same manner as in Example 1 except that the additive was added so that the addition amount to the nonaqueous electrolytic solution was 4000 ppm.

Next, the initial discharge capacities of the batteries of Examples 1 to 4 and Comparative Examples 1 and 2 produced as described above were measured. In addition, after charging, discharging, 20 times, and 30 times for each of these Examples and Comparative Examples,
That is, the discharge capacity retention rate after 10 cycles, 20 cycles, and 30 cycles was measured. The charging condition is
After charging to 4.2V with a constant current of 1.5 mAh,
It was set to charge at a constant voltage of 4.2 V for 2 hours. The discharge conditions were set to discharge up to 3 V with a current of 1.5 mAh.

Table 1 shows the evaluation results of the discharge capacity retention rate after the initial discharge capacity, after 10 cycles, after 20 cycles, and after 30 cycles in each of Examples and Comparative Examples.

[0086]

[Table 1]

In Table 1, after 10 cycles, 2
After 0 cycles and 30 cycles, the discharge capacity retention rate was 10 cycles after the initial discharge capacity, 20 cycles later,
The discharge capacity ratio after 30 cycles is shown.

From the evaluation results shown in Table 1, the amount of the additive added to the non-aqueous electrolyte is 100 ppm or more and 3000 pp.
In Examples 1 to 4 which are in the range of m or less, compared with Comparative Example 1 in which the additive is not added to the non-aqueous electrolyte solution, the discharge capacity retention rate after 10, 20, and 30 cycles It is found that the battery capacity is lowered due to charge / discharge, that is, the charge / discharge cycle characteristics are deteriorated.

In Comparative Example 1, when the additive was not added to the non-aqueous electrolyte and the lithium metal deposited on the negative electrode became insulative with the negative electrode and was deactivated, the deactivated lithium metal was ionized by oxidation. Since there is no additive, the amount of deactivated lithium metal continues to increase with repeated charging and discharging, and the charging and discharging cycle characteristics deteriorate.

On the other hand, in Examples 1 to 4, the amount of the additive added to the non-aqueous electrolyte was 100 ppm or more,
An appropriate amount is added in the range of 3000 ppm or less,
When the lithium metal deposited on the negative electrode is in an insulating state with the negative electrode and is deactivated, the additive oxidizes the deactivated lithium metal to ionize the lithium metal, which again contributes to charge and discharge. Then, in Examples 1 to 4, the positive electrode in the charged state oxidizes the additive reduced by the deactivated lithium metal, so that the redox potential of the additive is lower than the potential of the lithium metal deposited on the negative electrode. The high temperature causes the additive to be reused for the oxidation of deactivated lithium metal. As a result, in Examples 1 to 4, the additive deposits on the negative electrode with repeated charge and discharge and deactivates the deactivated lithium metal to form lithium ions that can contribute to charge and discharge. Deactivated lithium metal is not stored, and deterioration of charge / discharge cycle characteristics due to deactivation of lithium metal is prevented.

Here, in Example 3 and Comparative Example 1,
The relationship between the discharge voltage and the discharge time at the 20th cycle is shown in FIG. In FIG. 3, the horizontal axis represents discharge time, the vertical axis represents discharge battery voltage, and Example 3 is shown as S1 and Comparative Example 1 is shown as S2.

From FIG. 3, when comparing S1 and S2, the time until the relatively flat portion becomes relatively longer is S1, and the discharge time of S1 is longer and the battery capacity is larger accordingly. You can see that it has become. This is a band in which the lithium metal deposited on the negative electrode is ionized and discharged, that is, depending on the lithium metal, is discharged until the flat portion is reached. In S1, the negative electrode is deactivated by the additive. This is because the amount of lithium metal being charged is smaller than that of S2, and thus the time for ionizing and discharging lithium metal at the negative electrode can be longer than that of S2.

From the evaluation results shown in Table 1, the amount of additive added to the non-aqueous electrolyte was 100 ppm or more, 300
In Examples 1 to 4 which are in the range of 0 ppm or less, Comparative Example 2 in which the additive was added to the non-aqueous electrolyte solution at 4000 ppm.
It can be seen that the initial discharge capacity is significantly larger than that of.

In Comparative Example 2, the additive was added to the non-aqueous electrolyte at 40%.
Since it is added in an amount of 00 ppm and the amount added to the non-aqueous electrolyte is too large, a problem such as self-discharge occurs,
The discharge capacity of the battery is reduced.

On the other hand, in Examples 1 to 4, the amount of the additive added to the non-aqueous electrolyte was 100 ppm or more,
An appropriate amount is added in the range of 3000 ppm or less,
When the lithium metal deposited on the negative electrode is in an insulating state with the negative electrode and is deactivated, the additive oxidizes the deactivated lithium metal to ionize the lithium metal, which again contributes to charge and discharge. Then, in Examples 1 to 4, the positive electrode in the charged state oxidizes the additive reduced by the deactivated lithium metal, so that the redox potential of the additive is lower than the potential of the lithium metal deposited on the negative electrode. The high temperature causes the additive to be reused for the oxidation of deactivated lithium metal. Thus, in Examples 1 to 4, the additive deposits the deactivated lithium metal on the negative electrode and ionizes it again with repeated charging and discharging, and thus the deactivated lithium metal is stored in the negative electrode 4. Without
A decrease in discharge capacity due to deactivation of lithium metal is prevented.

From the above, it has been found that the non-aqueous electrolyte is used as an additive having an oxidation-reduction potential higher than the potential at which lithium metal is deposited on the negative electrode of a LOC battery and lower than the potential of the positive electrode in a charged state. Lithium chloride 100p
It has been clarified that the addition in the range of pm or more and 3000 ppm or less is very effective in producing a battery in which the reduction of discharge capacity and the deterioration of charge / discharge cycle characteristics are prevented.

[0097]

As is clear from the above description, according to the present invention, the redox in the non-aqueous electrolyte is higher than the potential of the metal when deposited on the negative electrode and lower than the potential of the positive electrode active material in the charged state. By adding an additive having a potential, the metal deposited on the negative electrode becomes an insulating state with the negative electrode and does not contribute to charging and discharging, that is, when the metal is deactivated, the deactivated metal While the additive oxidizes and ionizes, the positive electrode active material in the charged state oxidizes the additive reduced by the deactivated metal, and the redox potential of the additive is again determined from the potential of the metal deposited on the negative electrode. Make it higher

Thus, according to the present invention, the additive is ionized to a metal ion which is deposited and deactivated on the negative electrode with the repetition of charge and discharge to form a metal ion which can contribute to charge and discharge, and thus is deactivated on the negative electrode. It is possible to obtain a non-aqueous electrolyte battery in which the metal is not stored and the decrease in battery capacity and the deterioration of charge / discharge cycle characteristics due to deactivation of metal are prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an internal structure of a LOC battery according to the present invention.

FIG. 2 is a schematic diagram for explaining the action of an additive in the same LOC battery.

FIG. 3 LOC with non-aqueous electrolyte added with additives
FIG. 6 is a characteristic diagram showing the relationship between the discharge time at the 20th cycle and the discharge battery voltage in a battery and a LOC battery having a non-aqueous electrolyte solution to which an additive is not added.

FIG. 4 is a schematic diagram for explaining a state in which lithium metal deposited on a negative electrode is deactivated in a conventional LOC battery.

[Explanation of symbols]

1 LOC (Lithium On Carbon) battery, 2 positive electrode, 3
Positive electrode can, 4 Negative electrode, 5 Negative electrode can, 6 Separator, 7
Non-aqueous electrolyte, 8 gaskets, 9 lithium metal, 1
0 additive

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Akashi             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5H029 AJ03 AJ05 AK02 AK03 AK16                       AL01 AL02 AL06 AL07 AL08                       AL12 AL16 AL18 AM02 AM03                       AM04 AM05 AM07 BJ03 DJ09                       EJ04 EJ12 HJ01 HJ18 HJ19                 5H050 AA07 AA08 BA15 BA16 BA17                       CA07 CA08 CA09 CA11 CA20                       CB01 CB02 CB07 CB08 CB09                       CB12 DA13 EA09 EA11 EA24                       HA01 HA18 HA19

Claims (4)

[Claims] 1. A positive electrode having an active material containing lithium, a negative electrode having an active material capable of doping / dedoping a metal in an ionic state and / or depositing / eluting the metal, and an electrolyte salt. In a non-aqueous electrolyte battery comprising a non-aqueous electrolyte containing, in the non-aqueous electrolyte, the oxidation-reduction potential is nobler than the potential when depositing on the negative electrode of the metal, the potential of the positive electrode active material in the charged state has A non-aqueous electrolyte battery comprising an additive having a more basic redox potential added thereto. 2. The capacity of the negative electrode is a capacity component obtained when doping / dedoping the metal in an ionic state,
The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte battery is represented by a sum with a capacity component obtained when the metal is deposited / eluted. 3. The non-aqueous electrolyte battery according to claim 1, wherein the metal is lithium, and the redox potential of the additive is in the range of 0.1 V or more and 1.1 V or less. 4. The non-aqueous electrolyte battery according to claim 1, wherein the additive is lithium iodide, and the additive is added in the range of 100 ppm or more and 3000 ppm or less with respect to the non-aqueous electrolyte.