JPH1140153A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve battery characteristic by using an element which forms a compound with an alkali metal and a carbon material having no element, which forms a compound with an alkali metal for a negative electrode active material and specifying the composition of a positive electrode active material. SOLUTION: At least one bind of element which forms a compound with an alkali metal and a carbon material containing no element which forms a compound with an alkali metal are used for a negative electrode active material, and at least one kind of material to be used for a positive electrode active material is a compound oxide having Formula I (in the formula, A stands for one or more metals selected from among alkali metals, P is one or more kinds of elements selected from among Mg, B, P, and In, M is one or more kinds of elements selected from Mn, Co, And Al, N for one or more kind of element selected from among Si, Al, Ca, Cu, Sn, Mo, Nb, Y, and Bi, and w, v, z, y, z for the numbers of respective formulas II, III, IV, V, VI) and a mixture of the material with graphite having 150 Å or higher Lc, and a carbon black having 50 m<2> /g or lager specific surface area as conductive agents is used as the composition for the positive electrode active material.

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 Digi
tal Assistant or Personal Intelligent Comm
A demand for mobile communication (mobile computing) such as a unicator or a handheld communicator includes miniaturization and weight reduction.

However, since the power consumed by the backlight of the liquid crystal display panel and the drawing control is high, and the capacity of the secondary battery is still insufficient at present, the system is made compact and lightweight. Is in a difficult situation.

[0005] Further, with the increase in global environmental problems, electric vehicles that do not emit exhaust gas or noise are attracting 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.

[0006] Among secondary batteries, lithium secondary batteries using a non-aqueous electrolyte are attracting attention because they are expected to have 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 are 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.

[0007] However, these are not enough performances in terms of overvoltage, self-discharge characteristics, high temperature characteristics and the like during charging and discharging, in addition to the fact that the actually usable capacity is still low or the life is short. I can not say. In addition, there is also a problem in terms of safety such that the positive electrode active material is decomposed by heat during overcharge, causing thermal runaway, and the battery ignites and explodes. Conventionally, various active material compositions have been proposed in order to achieve higher capacity and longer life of a positive electrode.

For example, in order to improve the cycle characteristics, a positive electrode active material has a chemical formula of Li _x MO ₂ (M is Co, Ni, F
e, representing one or more elements selected from Mn) (JP-A-2-306022) or a chemical formula Li _x
M _y Ge _z O _p (M is Co, Ni, 1 or more transition metal elements selected from Mn, 0.9 ≦ x ≦ 1.3,0.8 ≦ y ≦
The use of a composite oxide represented by the following formula: 2.0, 0.01 ≦ z ≦ 0.2, 2.0 ≦ p ≦ 4.5) (JP-A-7-29603) is disclosed.

Further, the cycle characteristics, those for improving the self-discharge _{characteristics, A x M y N z O} 2 (A is at least one selected from alkali metal, M is a transition metal, N is the Represents at least one selected from the group consisting of Al, In, and Sn, wherein 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦
1.00, 0.001 ≦ z ≦ 0.10) (JP-A-7-176302).
To improve capacity and cycle characteristics, Li _y N
i _(1-x) MxO ₂ (M is at least one element selected from the group consisting of Cu, Zn, Nb, Mo, and W; 0 <x <1,0.
It discloses that a composite oxide represented by 9 ≦ y ≦ 1.3) is used (Japanese Patent Laid-Open No. 6-283174).

In order to improve the cycle characteristics and increase the load characteristics, a chemical formula Li _x Mg _y Co _z Ni is used.
_1-yz O _a (0.95 ≦ x ≦ 1.05, 0.02 ≦ z ≦ 0.1
5, a composite oxide represented by 0.003 <y <0.02, and if z <0.02, 0.003 <y <0.05, a = 2) is used. No. 185863).

Further, in order to reduce the overvoltage during charge and discharge and suppress the capacity deterioration, as a conductive agent added to the positive electrode, carbon black having an average primary particle size of 0.1 μm or less and graphite having an average primary particle size of 20 μm or less are used. (Japanese Unexamined Patent Publication No. Hei 8-222206) is disclosed.

Regarding the negative electrode material, Li ions are doped,
Highly crystalline graphite and amorphous carbon that can be undoped are mainly used.

[0013] However, in reality, in addition to the fact that the actually usable capacity is still low, the life is short, the load characteristics are low, and the like, Li precipitates in a dendritic manner on the negative electrode surface during rapid charging or overcharging. There have been problems such as short-circuiting, irreversible capacity increase, battery firing and explosion.

Conventionally, in order to achieve a higher capacity and an improved load characteristic of a negative electrode, for example, the surface of highly crystalline carbon particles forming a core is coated with a film containing a Group VIII metal element, and further coated thereon. Using a composite coated with carbon (Japanese Unexamined Patent Publication No. 5-299
No. 073) has been proposed. In order to improve the cycle characteristics, H / C <0.15, face spacing> 3.37
It has been proposed to use a mixture of a carbon material with {, Lc <150} and a metal that can be alloyed with Li (Japanese Patent Laid-Open No. 2-121258). Further, as a material capable of increasing the capacity, a material obtained by attaching copper oxide to graphite is used (Japanese Patent Laid-Open No.
No. 5-136099).

[0015]

The positive electrode active material has the formula L
i _x MO ₂ (M is Co, Ni, Fe, represents one or more elements selected from among Mn) when using a lithium-containing composite oxide represented by the cycle life is improved. However, it is hard to say that the characteristics are sufficient in terms of capacity. In addition, it has disadvantages such as a decrease in voltage. A _x M _y
N _z O ₂ (A is at least one selected from alkali metals, M is a transition metal, N is at least one selected from the group consisting of Al, In and Sn, and 0.05 ≦ x
≤ 1.10, 0.85 ≤ y ≤ 1.00, 0.001 ≤ z ≤
When the composite oxide represented by 0.10) is used, the cycle life is similarly improved, but the capacity that can be actually used for charging and discharging is reduced, so that the capacity cannot be increased. Chemical positive electrode active material formula _{Li x M y Ge z O p} (M is Co, Ni, M
one or more transition metal elements selected from n, 0.9 ≦ x ≦
1.3, 0.8 ≦ y ≦ 2.0, 0.01 ≦ z ≦ 0.2, 2.0
When the composite oxide represented by ≦ p ≦ 4.5) is used, the capacity and the cycle life are improved.

However, the thermal runaway reaction at the time of overcharging cannot be suppressed. Li _y Ni _(1-x) M _x O ₂ (M is Cu, Zn, N
at least one element selected from the group consisting of b, Mo, and W;
0 <x <1,0.9 ≦ y ≦ 1.3) When using a composite oxide represented by or formula _{Li x Mg y Co z Ni 1} -yz O a
(If 0.95 ≦ x ≦ 1.05, 0.02 ≦ z ≦ 0.15, then 0.003 <y <0.02, if z <0.02, 0.0.
003 <y <0.05, a = 2).

By using a mixed material of carbon black having an average primary particle size of 0.1 μm or less and graphite having an average particle size of 20 μm or less as a conductive agent to be added to the positive electrode, overvoltage during charging and discharging can be reduced. And cycle deterioration can be suppressed. However, control of the particle size alone cannot improve the rapid discharge characteristics, that is, the rate characteristics.
As described above, in addition to increasing the capacity and prolonging the life of the positive electrode material for secondary batteries, reducing the overvoltage during charging and discharging, and improving the rate characteristics, a sufficient improvement in safety has been found. Absent.

Further, the surface of the highly crystalline carbon particles forming the core of the negative electrode active material is coated with a film containing a Group VIII metal element,
When using a complex further coated with carbon on it,
Since the carbon on the surface assists the intercalation of lithium, the capacity is increased, and the load characteristics are also improved. However, the formation of dendritic precipitates of Li during overcharge cannot be suppressed, so that it reacts with the electrolyte or the positive electrode in the battery and causes an explosion, leaving a problem in terms of safety. H / C <0.15, face spacing> 3.
When a mixture of a carbon material of 37 ° and Lc <150 ° and a metal which can be alloyed with Li is used, the cycle life is apparently improved, but when the cycle is prolonged, the expansion and contraction of the metal alloyed with Li is large. As a result, collapse and falling off occur, and a sufficient cycle life cannot be obtained.

When graphite is used with copper oxide attached thereto, a high capacity can be obtained, but the formation of dendritic Li deposits during overcharge cannot be suppressed.

As described above, in the conventional combination of the positive electrode and the negative electrode, it is possible to achieve a high capacity, a long life, a low overvoltage during charge and discharge, and an improvement in rate characteristics, and an explosion and ignition during overcharge. No safe batteries have been obtained.

An object of the present invention is to improve these battery characteristics of a secondary battery material.

[0022]

According to the battery of the present invention, at least one of the negative electrode active materials is a carbon material containing an element forming a compound with an alkali metal and an element not forming a compound with an alkali metal. at least one of the positive electrode active material, the general formula _{a w P v Ni x M y} N z O 2 ( where a is at least one selected from alkali metal, P is Mg,
B is at least one kind selected from B, P, and In; M is at least one kind selected from Mn, Co, and Al;
N is Si, Al, Ca, Cu, Sn, Mo, Nb, Y,
Represents at least one selected from Bi, w, v,
x, y, z are respectively 0.05 ≦ w ≦ 1.2, 0.000
1 ≦ v ≦ 0.2, 0.5 ≦ x ≦ 0.95, 0.005 ≦ y ≦
0.5, 0 ≦ z ≦ 0.2), wherein Lc is 15 as a conductive agent of the positive electrode active material.
It is characterized by using a mixture of graphite of 0 ° or more and carbon black having a specific surface area of 50 m ² / g or more.

[0023] be one positive electrode active material in the novel cells of this invention represented by the general formula _{A w P v Ni x M y} N z O 2,
A is at least one selected from alkali metals, for example, Li, Na, and K, and among them, Li is preferable. The value of w varies depending on the charge state and the discharge state, and the range is 0.0.
5 ≦ w ≦ 1.2. In other words, deintercalation of A ions occurs due to charging and the value of w decreases, and intercalation of A ions occurs and discharging increases the value of w.

P is at least one selected from Mg, B, P, and In, and is preferably Mg,
More preferably, it is a combination of Mg and P. Although the value of v representing the amount of N does not fluctuate due to charging and discharging, it is 0.00
It is in the range of 01 ≦ v ≦ 0.02. The value of v is 0.0001
If it is less than N, the effect of N is not sufficiently exhibited, the cycleability in deep charge and deep discharge for obtaining a high capacity is poor, and the capacity is undesirably reduced. In addition, the value of v is set to 0.
If it exceeds 2, the capacity is undesirably reduced. M
The atomic ratio of Mg / P in the combination of g and P is preferably 0.1 or more and 12 or less.

The value of x representing the amount of Ni is 0.5 ≦ x
≦ 0.95. When the value of x is less than 0.5, the capacity is significantly reduced, which is not preferable. Also, if the value of x is 0.
If it exceeds 95, the cyclability in deep charge and deep discharge is poor, which is not preferable.

M is at least one selected from Mn, Co, and Al. The value of y does not vary depending on the state of charge and the state of discharge, and its range is 0.005 ≦ y ≦ 0.5. When the value of y is less than 0.005, the effect of M is not sufficiently exhibited, and the cycleability in deep charging and deep discharging is poor, which is not preferable. On the other hand, when the value of y exceeds 0.5, the capacity is reduced and the voltage is further reduced, which is not preferable.

N is Si, Al, Ca, Cu, Sn, M
It is at least one selected from o, Nb, Y, and Bi. The value of y does not vary depending on the state of charge and the state of discharge, and its range is 0 ≦ y ≦ 0.2. If the value of y exceeds 0.2, the capacity decreases and the voltage further decreases, which is not preferable.

The novel battery according to the present invention is characterized in that a mixture of graphite having an Lc of 150 ° or more and carbon black having a specific surface area of 50 m ² / g or more is used as a conductive agent of a positive electrode active material. If only graphite or only carbon black is added, the internal resistance of the electrode is high and good battery characteristics cannot be obtained. When graphite having an Lc of less than 150 ° is used, electron conductivity is low and good battery characteristics cannot be obtained. Also, when carbon black having a specific surface area of less than 50 m ² / g is used, the internal resistance of the electrode increases,
Good battery characteristics cannot be obtained.

At least one of the negative electrode active materials in the novel battery of the present invention is a carbon material containing an element that forms a compound with an alkali metal and an element that does not form a compound with an alkali metal. Contains at least one element selected from the group consisting of lead, tin, aluminum, silicon, indium, gallium, silver, boron, and magnesium;
Tin, aluminum, silicon, silver, and boron; more preferably, tin, aluminum, silicon, and silver; and most preferably, tin and silver. The element that does not form a compound with the alkali metal includes at least one element selected from the group consisting of iron, copper, cobalt, nickel, phosphorus, sulfur, and selenium, and preferably includes iron, copper, cobalt,
Phosphorus, sulfur, more preferably iron, copper, phosphorus,
Sulfur, most preferably iron and copper.

The element that forms a compound with an alkali metal and the element that does not form a compound with an alkali metal are at least one of a simple substance, an intermetallic compound, and an oxide, or a combination of a plurality of these, on the carbon material. It is characterized by being present. For example, when tin is contained as an element forming a compound with an alkali metal, tin alone, an oxide containing tin, or an intermetallic compound containing tin may be used. For tin,
An oxide containing tin is preferable, and amorphous is particularly desirable. In the case of silver, silver alone or an intermetallic compound containing silver is preferred.

When copper is contained as an element which does not form a compound with an alkali metal, copper alone, an oxide containing copper, or an intermetallic compound containing copper may be used. For copper,
Preferably, simple copper or an intermetallic compound containing copper is preferable, and an intermetallic compound of silver and copper is particularly desirable. In the case of phosphorus or sulfur, phosphorus or sulfur alone, an oxide containing phosphorus or sulfur, a phosphate or a sulfate, or an intermetallic compound containing phosphorus or sulfur may be used.

The element which forms a compound with an alkali metal and the element which does not form a compound with an alkali metal are formed into particles having a particle size of 1000 ° or less by an electroless plating process, an electrolytic plating process, or a dry process. The effect of the above-mentioned elements is sufficiently exerted by supporting them on. When the particle size is larger than 1000 °, the element forming a compound with the alkali metal undergoes a large volume change when the alkali metal is inserted and released, so that the element collapses.
Cycle life is short due to dropout.

Examples of the negative electrode active material include graphite, pyrolysis 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 of the present invention exhibits good characteristics by including one or a carbon material obtained by combining a plurality of them.

Examples of the electrolyte include propylene carbonate, propylene carbonate derivatives, ethylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyl lactone, dimethyl carbonate, and the like.
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 , Li
AsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl
₄ , a mixed solution of at least one salt selected from the group consisting of LiCl, LiBr, LiI, lithium lower aliphatic carboxylate, lithium chloroborane, lithium tetraphenylborate, etc .; For example, by using a gel electrolyte mixed with at least one selected from the group consisting of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride, polymethyl methacrylate, and hexafluoropropylene, the battery of the present invention has a good performance. Characteristics.

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. In addition to civilian use, it can also be used for military use and space use.

That is, a carbon material containing an element forming a compound with an alkali metal and an element not forming a compound with an alkali metal is used as at least one of the negative electrode active materials;
At least one of the positive electrode active materials has a general formula of A _w P _v Ni _x M
_y N _z O ₂ (where A is at least one selected from alkali metal, P is Mg, B, at least one selected P, from an In, M is selected Mn, Co, from Al And N is Si, Al, Ca, C
represents at least one selected from u, Sn, Mo, Nb, Y and Bi, w, v, x, y and z each being 0.0
5 ≦ w ≦ 1.2, 0.0001 ≦ v ≦ 0.2, 0.5 ≦ x ≦
0.95, 0.005 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.2) by using a complex oxide represented by the following formula: A highly safe battery that can achieve a reduction in overvoltage and that does not explode or ignite during overcharge can be obtained.

As a conductive agent for the positive electrode active material, Lc is 1
By using a mixture of graphite of 50 ° or more and carbon black having a specific surface area of 50 m ² / g or more, rapid charging characteristics are greatly improved, and a battery having particularly excellent low-temperature rate characteristics can be obtained. By using the electrode of the present invention and a battery using the same in various systems, the size and weight of the system can be reduced. In addition, it can be applied to a system that requires high-rate discharge at a low temperature.

The operation of the positive electrode active material of the present invention will be specifically described.

Since Mn, Co, and Al are less susceptible to oxidation than Ni, their pillar effect can extend the life.
The pillar effect refers to the effect of suppressing the stress of the crystal structure by pinning in the crystal because the specific element itself does not participate in the oxidation-reduction reaction in charge and discharge, that is, does not involve a change. Say Mg, Mo, C
Since u, Al, Ca, and Si have the effect of increasing the electrical conductivity of the positive electrode active material, overvoltage during charging and discharging can be reduced.

In addition, since B, P, and Si have small ionic radii, their substitution reduces the lattice volume of the positive electrode active material, suppresses collapse due to expansion of the lattice volume during charging, and extends the life. Can be. Since B and P are present at interstitial positions, the capacity does not decrease due to the replacement of B and P, and a high capacity can be maintained. Si, In, Sn, Mg, Ca, B
Substitution with i tends to cause defects in the crystal, so that the capacity can be increased and the rate characteristics can be improved. M
Since g, P, Al, B, Si, Y, Nb, and Ca have low oxygen releasing ability and are stably present as oxides, safety at high temperatures can be improved.

Further, Mg, P, Si, and Ca have different valences from the main constituent ions, Ni and Li, and are inserted at interstitial positions, so that the electronic structure in the crystal changes.
Since an improvement in electrical conductivity is expected, it is possible to achieve a reduction in overvoltage due to a reduction in internal resistance of the electrode, an improvement in rate characteristics and temperature characteristics, and a higher capacity. Mg is Li
Since the ionic radius is smaller than that of the ions, the replacement of the Li site with the Li site can reduce the lattice volume of the positive electrode active material, suppress the collapse due to expansion of the lattice volume during charging, and extend the life. Further, since Mg has a pillar effect after Li is released by substitution to the Li site,
The contraction of the grid that occurs at the end of charging is suppressed, the grid has almost no stress, and the life can be extended even when overcharging is performed.

Next, the function of the conductive agent of the present invention will be described. Lc
Is 400 ° or more, and the addition thereof increases the electron conductivity of the electrode itself. Further, in the case of carbon black having a specific surface area of 50 m ² / g or more, a binder used for fixing the positive electrode active material to the current collector is taken into the pores, so that the electrode is covered with a binder having a high insulating property. And the electronic conductivity is increased. By the addition of these two types of carbon, the electron conductivity is further enhanced,
High-rate discharge at low temperatures, which has been considered difficult, becomes possible.

Next, the operation of the negative electrode active material of the present invention will be described.
At the time of overcharging, the reaction of Li and an element forming a compound with an alkali metal can suppress the formation of dendritic precipitation of Li on the carbon material, and a highly safe battery with less explosion or ignition can be obtained. In addition, at the time of overdischarge, the release reaction of Li from the above compound obtained by the reaction with Li prevents the reduction reaction of the electrolytic solution on the carbon material, suppresses the deterioration of the positive electrode active material, and extends the life. it can.

Further, it was confirmed that by containing an element which does not form a compound with an alkali metal, the element forming a compound with the alkali metal can be relatively easily dispersed in the form of particles of 1,000 ° or less on a carbon material. Has been confirmed. The effect of highly dispersing into particles of 1000 ° or less is that the stress of expansion and contraction during insertion and release of Li in the element forming the compound with the alkali metal can be reduced, and the life can be greatly extended. In addition, by supporting the element shown in the present invention on a carbon material, the electronic structure of the carbon material can be changed. Thereby, the electrostatic trap of Li remaining in the layer can be released, and Li can be easily released. Thereby, a capacity substantially corresponding to the theoretical capacity can be obtained, and irreversible capacity loss can be reduced.

As an element forming a compound with an alkali metal, lead, tin, aluminum, silicon, indium, gallium, silver, boron, and magnesium are preferable because of excellent cycle reversibility. Elements that do not form compounds with alkali metals include iron, copper, cobalt, nickel, phosphorus, sulfur,
Selenium can easily and highly disperse an element forming a compound with an alkali metal. Above all, simple substances or intermetallic compounds of silver, tin, copper and aluminum also have the effect of improving the electrical conductivity, and are therefore effective in improving the rate characteristics and temperature characteristics. When phosphates, sulfates, and oxides are contained, the presence of these matrices can alleviate the stress of expansion and contraction at the time of Li insertion and release, and extend the life.

The operation of the combination of the negative electrode active material and the positive electrode active material of the present invention will be described. The safety at the time of overcharging at a low temperature, which becomes a problem when the positive electrode active material of the present invention is used, can be improved by combining the negative electrode active material of the present invention. In the overcharged state, if the amount of metallic Li deposited on the negative electrode is large, the deposited Li and the positive electrode active material of the present invention react rapidly, generating enormous heat at low temperature, leading to ignition and explosion. When a conventional carbon material, for example, natural graphite or mesophase pitch-based graphite is used for the negative electrode, overcharging at room temperature does not result in ignition or explosion even when combined with the positive electrode active material of the present invention.
At low temperatures, particularly at 10 ° C. or lower, metallic Li tends to precipitate on the carbon surface and reacts with the deposited Li to ignite or explode. The negative electrode active material of the present invention does not deposit metallic Li even at 10 ° C. or less, so that ignition and explosion can be suppressed even at overcharge at low temperatures.

Further, by the combination of the negative electrode active material and the positive electrode active material of the present invention, there is no capacity reduction at the time of overdischarge, and the overdischarge characteristics are greatly improved. When a conventional carbon material, for example, natural graphite or mesophase pitch-based graphite is used as a negative electrode and the positive electrode active material of the present invention is used as a positive electrode, in an overdischarge, an electrolytic solution is decomposed on the carbon material, and a generated decomposed product is formed. The reaction on the positive electrode active material of the present invention causes the positive electrode active material to deteriorate.

In the negative electrode active material of the present invention, since the reduction reaction of the electrolytic solution on the carbon material at the time of overdischarge can be suppressed, the life of the positive electrode active material can be extended without deterioration. Further, low-temperature characteristics and low-temperature rate characteristics, which are problems when the negative electrode active material of the present invention is used, can be improved by combining the positive electrode active material of the present invention. Conventional cathode material, for example, A _x M _y N
_z O ₂ (A is at least one selected from alkali metals, M is a transition metal, N is at least one selected from the group consisting of Al, In and Sn, and 0.05 ≦ x ≦
1.10, 0.85 ≦ y ≦ 1.00, 0.001 ≦ z ≦ 0.
When 10) is used, the electric conductivity of the positive electrode active material is significantly reduced at a low temperature, particularly at −20 ° C. or lower, so that the capacity of the positive electrode is significantly reduced. As a result, the operating potential of the negative electrode greatly deviates from the design value, and reaches the Li deposition region or the electrolytic solution decomposition region, and the battery cannot be charged or discharged.

The positive electrode active material of the present invention has a high electric conductivity, and exhibits a metallic behavior in which the electric conductivity increases particularly at a low temperature side. Furthermore, by combining with the positive electrode active material and the conductive agent of the present invention, even at a rapid discharge of −20 ° C. or less, almost the same capacity as at room temperature can be obtained, and the operating potential of the negative electrode greatly deviates from the design value, thereby causing Li deposition. There is no problem such as reaching the region or the decomposition region of the electrolytic solution, and the rate characteristics particularly at a low temperature are greatly improved.

As the combination of the positive electrode and the negative electrode of the present invention with the electrolytic solution, LiClO ₄ , LiBF ₄ , LiPF
₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , L
iSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiC
When l, LiBr, LiI, lithium lower aliphatic carboxylate, lithium chloroborane, and lithium tetraphenylborate are used, they show excellent temperature characteristics. Especially Li
When at least one of BF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , and LiCF ₃ CO ₂ is used, the elution of the M element in the positive electrode active material of the present invention is suppressed even at 60 ° C. Demonstrates excellent effect on high temperature characteristics.

Further, as a combination of the positive electrode and the negative electrode of the present invention with an electrolytic solution, propylene carbonate, a propylene carbonate derivative, 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, gisan methyl, methyl acetate, methyl propionate, ethyl propionate, phosphoric acid triester,
Trimethoxymethane, dioxolane derivative, diethyl ether, 1,3-propanesultone, sulfolane, 3-
Methyl-2-oxazolidinone, tetrahydrofuran,
When a tetrahydrofuran derivative, dioxolan, or 1,2-diethoxyethane is used, it shows excellent life characteristics. In particular, propylene carbonate, propylene carbonate derivatives, ethylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyl lactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane,
When at least one of 2-methyltetrahydrofuran and dimethylsulfoxide is used, an irreversible reaction between the negative electrode active material of the present invention and a solvent is suppressed, so that an effect with excellent life characteristics is exhibited.

Furthermore, by including a halide of the above solvent in the solvent as a combination of the positive electrode and the negative electrode of the present invention and the electrolytic solution, the safety is remarkably improved. In particular, propylene carbonate, propylene carbonate derivatives, ethylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyl lactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, part of 2-methyltetrahydrofuran, and dimethyl sulfoxide Element of-
_{F, -CF, -CF 2, -CF} 3, -Cl, -CCl, -
When at least one of CCl ₂ and -CCl ₃ is used, the exothermic reaction between the positive electrode active material of the present invention and the solvent under overcharge conditions is suppressed, the establishment of ignition is significantly reduced, Show safety.

The combination of the positive electrode, the negative electrode and the electrolytic solution of the present invention is selected from the group consisting of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride, polymethyl methacrylate, and hexafluoropropylene in the above mixed solution of the lithium salt and the solvent. When a gel electrolyte mixed with at least one of the above is used, the exothermic reaction of the positive electrode active material of the present invention and the gel electrolyte under overcharge conditions is suppressed, and the establishment of ignition is significantly reduced. Shows high security.
In addition, in the combination of the positive electrode active material of the present invention and the gel electrolyte, even at a high potential of 4.5 V, the positive electrode active material of the present invention can be charged, so that the capacity can be increased.

[0054]

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) A material having the composition shown in Table 1 was used as a positive electrode material, and graphite of Lc shown in Table 1 and carbon black 5: 1 having a specific surface area as a conductive agent were used as a binder. Vinylidene was weighed so as to have a weight ratio of 88: 7: 5, kneaded with a grinder for 30 minutes, and applied to both sides of a 20-micron thick aluminum foil. Table 1 as negative electrode material
Was applied to both surfaces of a copper foil having a thickness of 20 microns using a mixture prepared by mixing 93% by weight of a material having the composition shown in Table 1 and 7% by weight of polyvinylidene fluoride as a binder. 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 were laminated via a microporous polypropylene separator, wound up spirally, and inserted into an aluminum battery can. The negative electrode terminal was welded to the battery can, and the positive electrode terminal was welded to the battery lid. As an electrolytic solution, a solution prepared by dissolving 1 mol of LiPF ₆ in 1 liter of a mixed solution of ethylene carbonate and diethyl carbonate was used, and the solution was injected into a battery can. Caulked the battery cover 18
A cylindrical battery having a capacity of 00 mAh was produced. Battery is 360
After charging to 4.2V at mA, constant current charge / discharge is performed to discharge to 2.7V at 360mA, capacity, life, 1.5C rate characteristics at -20 ° C, 2C overcharge test at -20 ° C Was evaluated. Table 1 shows the results.

Comparative Example 1 A battery was produced in the same manner as in Example 1 except that the materials shown in Table 1 were used as the positive electrode material, the negative electrode material, and the conductive agent. Capacity, life, 1.5 C at -20 ° C
And the overcharge test of 2C at −20 ° C. were evaluated. Table 1 shows the results. There is an extremely low characteristic as compared with the first embodiment.

[0057]

[Table 1]

[0058]

According to the present invention, it is possible to realize high safety, compactness and light weight of a battery and a system, good high-rate characteristics at a low temperature, and a long life.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01M 10/40 H01M 10/40 A (72) Inventor Ren Murakana 7-1-1, Omika-cho, Hitachi City, Hitachi City, Ibaraki Pref. Hitachi Research Laboratory, Hitachi Research Laboratory

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.
At least one of the negative electrode active materials is a carbon material containing an element that forms a compound with an alkali metal and an element that does not form a compound with an alkali metal, and at least one of the positive electrode active materials has a general formula of A _w P _{v Ni x M y N z O 2} ( where A
Is at least one selected from alkali metals, and P
Is at least one selected from Mg, B, P, In, M is at least one selected from Mn, Co, Al, and N is Si, Al, Ca, Cu, Sn, Mo, N
represents at least one selected from b, Y, and Bi;
w, v, x, y, z are respectively 0.05 ≦ w ≦ 1.2,
0.0001 ≦ v ≦ 0.2, 0.5 ≦ x ≦ 0.95, 0.0
05 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.2), a graphite having an Lc of 150 ° or more as a conductive agent of the positive electrode active material, and a specific surface area of 50 m ² / g. A battery characterized by using a mixture with carbon black. 2. An element forming a compound with an alkali metal of the negative electrode active material, wherein at least one element selected from the group consisting of lead, tin, aluminum, silicon, indium, gallium, silver, boron and magnesium. As an element that contains an element and does not form a compound with an alkali metal,
2. The battery according to claim 1, further comprising at least one element selected from the group consisting of iron, copper, cobalt, nickel, phosphorus, sulfur, and selenium. 3. The element that forms a compound with an alkali metal and the element that does not form a compound with an alkali metal are a simple substance,
The battery according to claim 1, wherein at least one of an intermetallic compound and an oxide or a combination of a plurality thereof is present on the carbon material. 4. The carbon material according to claim 1, wherein said element forming a compound with said alkali metal and said element not forming a compound with said alkali metal are supported on a carbon material in the form of particles having a particle size of 1000 ° or less. Batteries. 5. The negative electrode active material includes graphite, pyrolysis graphite, carbon fiber, vapor-grown carbonaceous material, pitch-based carbonaceous material, coke-based carbonaceous material, phenol-based carbonaceous material, rayon-based carbonaceous material. Low-crystalline carbon and high-crystalline carbon selected from the group consisting of conductive materials such as porous materials, polyacrylonitrile-based carbonaceous materials, glassy carbon, carbon black, furfuryl alcohol-based carbonaceous materials, and polyparaphenylene. 2. The battery according to claim 1, wherein the battery comprises a carbon material obtained by combining at least one of the above or a plurality thereof. 6. An electrolyte comprising 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, phosphoric acid triester, trimethoxymethane, dioxolane derivative,
Diethyl ether, 1,3-propane sultone, sulfolane, 3-methyl-2-oxazolidinone, tetrahydrofuran, tetrahydrofuran derivative, dioxolan,
At least one or more non-aqueous solvents selected from the group consisting of 1,2-diethoxyethane and / or halides thereof, and LiClO ₄ , LiBF ₄ , LiP
F ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiS
bF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, Li
A mixed solution of at least one or more lithium salts selected from the group consisting of Br, LiI, lithium lower aliphatic carboxylate, lithium chloroborane, lithium tetraphenylborate, and / or a mixed solution thereof, and 2. The battery according to claim 1, wherein a gel electrolyte mixed with at least one polymer selected from the group consisting of acrylonitrile, polyethylene oxide, polyvinylidene fluoride, polymethyl methacrylate, and hexafluoropropylene is used. 7. A notebook personal computer, a pen input personal computer, a pocket personal computer, a notebook type word processor, a pocket word processor,
E-book player, mobile phone, cordless phone handset, pager, handy terminal, 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,
TV, stereo, water heater, microwave oven, dishwasher, washing machine, dryer, game equipment, lighting equipment, toy, road conditioner, medical equipment, automobile, electric car, golf cart, electric cart, power storage system The battery according to claim 1, wherein the battery according to item 1 is used.