JPH1116566A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the safety by using a positive electrode active material covered with a metal containing at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo and/or an intermetallic compound obtained by the combination of a plurality of thereof, and/or an oxide thereof. SOLUTION: The positive electrode surface on the side opposite to a negative electrode is preferably covered with a metal containing at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo and/or an intermetallic compound obtained by the combination of a plurality of thereof, and/or an oxide thereof. The separator surface on the side opposite to the positive electrode is preferably covered with a metal containing at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo and/or an intermetallic compound obtained by the combination of a plurality of thereof, and/or an oxide thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery that can be reversibly charged and discharged a plurality of times, and more particularly to a secondary battery using a non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, secondary batteries have become one of the essential components that are indispensable as power sources for personal computers and mobile phones, or as power sources for electric vehicles and power storage.

A portable computer (including a pen computer) and a personal digital assistant (Personal Digita)
l Assistant or Personal Intelligent Communic
A demand for mobile communication (mobile computing) such as an ator or a hand-held communicator includes miniaturization and weight reduction. However, it is difficult to make the system compact and lightweight because of the high power consumed by the backlight and drawing control of the liquid crystal display panel, and the fact that the capacity of the secondary battery is still insufficient at present. It is in.

[0004] Further, with the increase of global environmental problems, electric vehicles that do not emit exhaust gas and noise have attracted attention.
However, current batteries have problems such as short running distance, poor acceleration, small space inside the vehicle, and poor stability of the vehicle body due to low energy density and low output density.

[0005] Among secondary batteries, lithium secondary batteries using a non-aqueous electrolyte are particularly attracting attention because of their high voltage, light weight, and high energy density. As the positive electrode material of this secondary battery, conductive polymers such as polyaniline, polyacene, polyparaphenylene and Li _x
CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x Fe
Representative examples include oxides of transition metals such as O ₂ , V ₂ O ₅ , Cr ₂ O ₅ , and MnO _2, and chalcogenite compounds such as TiS ₂ and MoS ₂ . In particular, the positive electrode of a secondary battery such as Li _x CoO ₂ or Li _x NiO ₂ disclosed in JP-A-55-136131 has an electromotive force of 4 V or more when Li metal is used as the negative electrode. Can be expected. However, there has been a problem in terms of safety such that these positive electrode active materials decompose exothermically during overcharge and cause thermal runaway, causing the battery to ignite or explode, or to explode due to crushing or dumping in fire. Conventionally,
Various additives have been proposed to ensure safety during overcharge of the positive electrode. For example, for the positive electrode, lithium carbonate
(JP-A-4-328278) and lithium oxalate (JP-A-4-328278).
No. 329269), or MC for the positive electrode.
There is disclosed a material to which O ₃ (M is Co, Mn, Ni) is added (JP-A-6-111848).

[0006]

In order to suppress ignition or explosion of the battery at the time of overcharging, the internal pressure of the battery is increased before the battery is ignited, and the pressure switch is used to open the pressure valve, It is necessary to interrupt current. Lithium carbonate, carbonates such as Co, Mn, Ni, and lithium oxalate decompose and generate gas in an overcharged state, which can increase the internal pressure in the battery, thereby suppressing ignition and explosion. Can be. However, the voltage at which these substances decompose to generate gas is 4.7 to 5.0 V.
Gas generation does not occur at a low voltage of 4.2 V to 4.6 V, which is the normal upper limit of charging. As a result, 10% to 2% of the batteries will ignite or explode without operating the pressure switch.
It occurs at about a percentage. Further, in crushing and dumping in a fire, the thermal runaway reaction due to the decomposition of the positive electrode is faster than the decomposition of the above-mentioned substances, so that the effect of adding these substances is hardly obtained. As described above, few effective methods have been found for improving the safety of the secondary battery against overcharging, crushing, and dumping in fire.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a secondary battery which has improved safety against overcharge, crushing, dumping in fire, and the like, and is free from ignition and explosion.

[0008]

According to the present invention, a positive electrode and a battery include Ti, Al, Sn, Bi, C
using a metal containing at least one selected from u, Si, Ga, W, Zr, B and Mo and / or an intermetallic compound and / or an oxide obtained by combining a plurality of these metals; Features.

Further, the positive electrode and the battery of the present invention have a structure in which Ti, Al, Sn, Bi, C
using a metal containing at least one selected from u, Si, Ga, W, Zr, B and Mo and / or an intermetallic compound and / or an oxide obtained by combining a plurality of these metals; It is characterized by.

[0010] Further, the separator and the battery of the present invention include:
Ti, Al, S on the separator surface facing the positive electrode
Coated with a metal containing at least one selected from n, Bi, Cu, Si, Ga, W, Zr, B and Mo and / or an intermetallic compound and / or oxide obtained by combining a plurality of these metals Is used.

As a coating method, Ti, Al, S
Using an intermetallic compound or an oxide target obtained by a single metal containing at least one selected from n, Bi, Cu, Si, Ga, W, Zr, B, and Mo, or a combination of a plurality of these metals; A method using a dry process in which these layers are coated by sputtering or the like on the surface of the positive electrode active material particles, the surface of the positive electrode facing the negative electrode, or the surface of the separator facing the positive electrode, by electroplating or electroless metal plating After that, heat treatment in a reducing atmosphere or heat treatment in an oxidizing atmosphere
A method of coating a surface of a simple metal, an intermetallic compound, or an oxide film on the surface, by mechanically fusing the fine metal simple substance, an intermetallic compound, or an oxide on the surface of the positive electrode active material particles while mixing. There is a method of forming these layers on the particle surface. As the shape of the coating, even if the surface of the positive electrode active material particles, or the surface of the positive electrode facing the negative electrode, or the surface of the separator facing the positive electrode is coated in a film shape, a plurality of particles are coated in a granular manner. Is also good.

The positive electrode or separator of the present invention and a battery using the same are characterized in that the oxide is amorphous. These oxides preferably have a non-stoichiometric composition and desirably have a lower oxygen content than the stoichiometric composition.

Examples of the electrolyte include propylene carbonate, propylene carbonate derivatives, ethylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyl lactone, dimethyl carbonate,
Diethyl carbonate, methyl ethyl carbonate,
1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, gisanmethyl, methyl acetate, methyl propionate, ethyl propionate,
Triester phosphate, trimethoxymethane, dioxolane derivative, diethyl ether, 1,3-propanesultone, sulfolane, 3-methyl-2-oxazolidinone,
At least one non-aqueous solvent selected from the group consisting of tetrahydrofuran, tetrahydrofuran derivative, dioxolan, 1,2-diethoxyethane, and halides thereof, and a lithium salt such as LiClO ₄ ,
LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF _{3
CO 2, LiAsF 6, LiSbF 6} , LiB 10 Cl 10,
LiAlC _l4, LiCl ,. By using a mixed solution with at least one salt selected from the group consisting of LiBr, LiI, lithium lower aliphatic carboxylate, lithium chloroborane, lithium tetraphenylborate, and the like,
The negative electrode active material of the present invention shows good characteristics.

The positive electrode active material may be any material capable of inserting and releasing lithium, but is preferably a lithium-containing transition metal oxide. For example, Li _x Mn ₂ O ₄ , Li _x C
oO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x MaNi
_(1-a) O ₂ (M is Co, V, Mn, Fe, B, Mg, A
one or more elements selected from l, Cu, Cr, a = 0.
01-0.95).

The use of the reversibly chargeable / dischargeable battery of the present invention is not particularly limited. For example, notebook personal computers, pen input personal computers, pocket personal computers, notebook word processors, pocket word processors, electronic book players, mobile phones, cordless phones Phone handset, pager, handy terminal, portable copy, electronic organizer, calculator, LCD TV,
Electric shaver, power tool, electronic translator, car phone,
Power supplies for equipment such as transceivers, voice input devices, memory cards, backup power supplies, tape recorders, radios, headphone stereos, portable printers, handy cleaners, portable CDs, video movies, navigation systems, refrigerators, air conditioners, televisions,
Stereo, water heater, microwave oven, dishwasher,
It can be used as a power source for washing machines, dryers, game devices, lighting devices, toys, road conditioners, medical devices, automobiles, electric vehicles, golf carts, electric carts, power storage systems, and the like. It can be used not only for civilian purposes but also for military use and space.

That is, by using the positive electrode or the separator of the present invention or a battery using the same, the safety against overcharge, crushing, dumping in fire, and the like can be improved as compared with the conventional one.

The operation of the present invention will be specifically described. Ti, Al, Sn, Bi, Cu, Si, G around the positive electrode active material
a, W, Zr, B, Mo, and at least one metal selected from the group consisting of a metal and / or an intermetallic compound and / or an oxide obtained by combining a plurality of these metals. And ignition that does not depend on the voltage, such as ignition at low temperatures, ignition at low temperatures, crushing, and dumping during fire. The battery of the present invention has a built-in gas generating substance and generates gas at a predetermined voltage or a predetermined temperature before ignition, thereby increasing the internal pressure of the battery, opening a pressure valve, and interrupting current. Completely different. That is,
The battery of the present invention does not take measures to cause an increase in internal pressure. As a result of analyzing the cause of battery ignition, the following conclusions were reached. When the positive electrode active material is in an overcharged state, it becomes very unstable and releases oxygen to easily self-decompose. This decomposition reaction easily decomposes at a low temperature of about 200 ° C. with extremely large heat generation in a state where the organic electrolyte coexists. Oxygen gas generated at this time reacts with hydrogen or halogen generated by decomposition of the electrolytic solution, or a radical species containing these, causing ignition or explosion.

The battery of the present invention incorporates a substance for rapidly absorbing oxygen gas generated from the positive electrode, which causes ignition and explosion, and reduces the oxygen gas concentration to cause ignition and explosion.
Explosion can be suppressed. As a result of various studies as an oxygen absorbent, it was found that Ti, Al, Sn, Bi, Cu, Si, G
It was found that the metals a, W, Zr, B, and Mo were excellent in oxygen absorbing ability. It has also been found that these intermetallic compounds may be used, and oxides containing them may also have oxygen absorbing ability. These oxides are amorphous, preferably non-stoichiometric and have a lower oxygen content than the stoichiometric composition, and can absorb more oxygen. In addition, it has been found that these substances can obtain an effect by being attached around the positive electrode active material, and can also absorb oxygen on both the surface of the positive electrode and the surface of the separator. When it is attached to the surface of the separator, the oxygen absorption proceeds smoothly by attaching it to the separator surface on the positive electrode side.

As described above, in the present invention, since the safety can be ensured by absorbing the oxygen gas which causes the ignition and explosion, the safety test which has been conventionally difficult is 1.5 to 2.5. It is effective in overcharging at low voltage of 5 ° C, overcharging at low temperature, crushing, nailing, dumping in fire, etc.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the examples unless it exceeds the gist of the invention.

(Example 1) The materials shown in Table 1 were used as a positive electrode material and a coating material for coating the positive electrode material, and were weighed so that the weight ratio was 95: 5. This was rotated for 15 hours in an Ar atmosphere at a rotation speed of 250 rpm using a planetary ball mill to coat the coating material on the positive electrode surface. 85% by weight of this powder, 5 parts of polyvinylidene fluoride as a binder
Using a mixture prepared by preparing 10% by weight of graphite powder as a conductive agent by weight, the mixture was kneaded for 30 minutes with a rake machine, and then applied to both sides of a 20-micron thick aluminum foil. A graphite powder was used for the negative electrode, and a mixture prepared by mixing 87% by weight of acetylene black as a conductive agent, 6% by weight of acetylene black as a conductive agent, and 7% by weight of polyvinylidene fluoride as a binder was mixed with a grinder for 30 minutes. After bricking, it was applied to both sides of a copper foil having a thickness of 10 microns. The positive and negative electrodes were roll-formed by a press, and the terminals were spot-welded and then vacuum-dried at 150 ° C. for 5 hours.

A positive electrode and a negative electrode are laminated with a microporous polypropylene separator interposed therebetween, and this is spirally wound.
s battery can. The negative electrode terminal was welded to the battery can, and the positive electrode terminal was welded to the battery lid. The electrolyte contains 1 mol of LiPF ₆
Was dissolved in 1 liter of a mixed solution of ethylene carbonate and diethyl carbonate, and the solution was injected into a battery can. The battery cover was swaged to produce a cylindrical battery having a capacity of 1400 mAh. After charging the battery to 4.2 V at 280 mA, (1) nailing test, (2) crush test, (3) -10
℃, 1.5C overcharge test, (4) 700 ℃ fire dumping test was carried out. Table 1 shows the number of batteries that ignited or exploded out of the ten batteries. The number of batteries that ignite or explode is small,
Safety has improved.

(Comparative Example 1)

[0024]

[Table 1]

As in Example 1, a mixture prepared by preparing 85% by weight of LiNi _0.8 Co _0.2 O ₂ as a positive electrode material, 5% by weight of polyvinylidene fluoride as a binder, and 10% by weight of graphite powder as a conductive agent. To produce a battery. Table 1 shows the same safety test results as in Example 1. The number of ignited batteries is larger than in the first embodiment.

(Example 2) LiNi _0.8 as a positive electrode material
A mixture prepared by preparing 85% by weight of Co _0.2 O ₂ , 5% by weight of polyvinylidene fluoride as a binder, and 10% by weight of graphite powder as a conductive agent was kneaded with a triturator for 30 minutes, and the thickness was 20%. It was applied to both sides of a micron aluminum foil. A graphite powder was used for the negative electrode, and a mixture prepared by mixing 87% by weight of acetylene black as a conductive agent, 6% by weight of acetylene black as a conductive agent, and 7% by weight of polyvinylidene fluoride as a binder was mixed with a grinder for 30 minutes. After bricking, it was applied to both sides of a copper foil having a thickness of 10 microns. The positive and negative electrodes were roll-formed by a press, and the terminals were spot-welded and then vacuum-dried at 150 ° C. for 5 hours. A titanium powder having a particle size of 5 μm or less and polyvinylidene fluoride are prepared at a weight ratio of 90:10 on the positive electrode side of a microporous polypropylene separator, and a solution diluted with a volatile organic solvent is sprayed. Sprayed and dried. A battery was manufactured and a safety test was performed in the same manner as in Example 1. Table 1 shows the results. The number of batteries that ignite or explode is small, improving safety.

Example 3 LiNi _0.8 as a positive electrode material
A mixture prepared by preparing 85% by weight of Co _0.2 O ₂ , 5% by weight of polyvinylidene fluoride as a binder, and 10% by weight of graphite powder as a conductive agent was kneaded with a triturator for 30 minutes, and the thickness was 20%. It was applied to both sides of a micron aluminum foil and dried.
A Ti powder having a particle size of 5 μm or less and polyvinylidene fluoride were prepared in a weight ratio of 90:10, and a solution diluted with a volatile organic solvent was sprayed on the surface of the positive electrode by spraying and dried. . A graphite powder was used for the negative electrode, and a mixture prepared by mixing 87% by weight of acetylene black as a conductive agent, 6% by weight of acetylene black as a conductive agent, and 7% by weight of polyvinylidene fluoride as a binder was mixed with a grinder for 30 minutes. After pricking, thickness 1
It was applied to both sides of a 0 micron copper foil. The positive and negative electrodes were roll-formed by a press, and the terminals were spot-welded and then vacuum-dried at 150 ° C. for 5 hours. A battery was manufactured and a safety test was performed in the same manner as in Example 1. Table 1 shows the results. The number of batteries that ignite or explode is small, improving safety.

[0028]

As described above, according to the present invention, safety can be ensured by absorbing oxygen gas which causes ignition and explosion. It is effective in overcharging at low voltage of 2.5C, overcharging at low temperature, crushing, nailing, dumping in fire, etc.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Ren Muranaka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] 1. A battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt, which can be charged and discharged a plurality of times reversibly.
Around the positive electrode active material in the positive electrode, Ti, Al, Sn,
Metals containing at least one selected from the group consisting of Bi, Cu, Si, Ga, W, Zr, B, and Mo and / or those coated with an intermetallic compound and / or oxide obtained by combining a plurality of these metals And a battery using the same. 2. A battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt, which can be charged and discharged a plurality of times reversibly.
On the surface of the positive electrode opposite to the negative electrode, Ti, Al, Sn,
Metals containing at least one selected from the group consisting of Bi, Cu, Si, Ga, W, Zr, B, and Mo and / or those coated with an intermetallic compound and / or oxide obtained by combining a plurality of these metals And a battery using the same. 3. A battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt, wherein the battery is capable of reversibly charging and discharging a plurality of times, wherein the battery is separated by a separator between the positive electrode and the negative electrode. Ti, Al,
Coated with a metal containing at least one selected from the group consisting of Sn, Bi, Cu, Si, Ga, W, Zr, B and Mo, and / or an intermetallic compound and / or oxide obtained by combining a plurality of these metals And a battery using the separator. 4. The positive electrode or separator according to claim 1, wherein the oxide is amorphous, and a battery using the same. 5. The method according to claim 1, wherein the positive electrode active material is Li _x Mn ₂ O ₄ , Li _x Co
O ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x MaNi _(1-a) O
₂ (M is Co, V, Mn, Fe, B, Mg, Al, C
one or more elements selected from u and Cr, a = 0.01
The positive electrode or the separator according to claim 1, wherein the positive electrode or the separator is a lithium-containing transition metal oxide represented by -0.95). 6. The negative electrode active material includes graphite, pyrolytic graphite, carbon fiber, vapor-grown carbonaceous material, pitch-based carbonaceous material, coke-based carbonaceous material, phenol-based carbonaceous material, rayon-based carbonaceous material. , Polyacrylonitrile-based carbonaceous materials, glassy carbon, carbon black, furfuryl alcohol-based carbonaceous materials, polyparaphenylene, etc. The battery according to any one of claims 1 to 5, further comprising a carbon material obtained by combining one or a plurality thereof. 7. A notebook personal computer, a pen input personal computer, a pocket personal computer, a notebook type word processor, a pot word processor, an electronic book player, a mobile phone, a cordless phone handset, a pager, a handy terminal, a mobile copy,
Electronic organizer, calculator, liquid crystal television, electric shaver, electric tool, electronic translator, car phone, transceiver, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, portable printer, handy cleaner, portable CD, Video movie, navigation system, refrigerator, air conditioner,
Used for TVs, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, game equipment, lighting equipment, toys, road conditioners, medical equipment, automobiles, electric vehicles, golf carts, electric carts, and power storage systems. The battery according to claim 1, wherein: