JPH11260365A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with high energy density, long cycle life, and high reliability. SOLUTION: An electrolyte layer is interposed between a pair of electrodes, whose at least one electrode is made of an electrode material having a heat of wetting of 1,100 (mJ/g) or less. One electrode made of this electrode material is used as a negative electrode. The negative electrode is preferably made of a material containing a carbon material, capable of doping/undoping lithium. The electrolyte layer is a nonaqueous electrolyte or a polymer matrix containing a nonaqueous solvent and an electrolyte salt. Or one electrode made of a material containing lithium is used as the negative electrode, and the other electrode made of a material containing a metal composite oxide is used as the positive electrode. Alternatively, one electrode made of a material containing the carbon material is used as the negative electrode and the other electrode made of a material containing a lithium-containing transition metal composite oxide is used as the positive electrode. The carbon material is preferably a graphoitization resistant carbon material or a graphite material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a battery. More specifically, the present invention relates to a battery in which high energy density and long cycle life are maintained by specifying the heat of wetting of a material forming an electrode, and high reliability is secured.

[0002]

2. Description of the Related Art In recent years, remarkable progress in electronic technology has enabled electronic devices to become smaller and lighter one after another. Along with this, there is an increasing demand for a battery as a portable power supply that is smaller, lighter and has a higher energy density.

Conventionally, aqueous secondary batteries such as lead batteries and nickel-cadmium batteries have been the mainstream as secondary batteries for general use. Although these batteries could satisfy the cycle characteristics to some extent, they could not be said to be satisfactory in terms of battery weight and energy density.

Subsequently, as a new secondary battery having an operating voltage equivalent to that of a nickel-cadmium battery and realizing a higher capacity, a nickel-hydrogen battery using a hydrogen storage alloy for the negative electrode and nickel hydroxide for the positive electrode has been developed. It was put to practical use. The battery is completely compatible with nickel-cadmium batteries, and the hydrogen storage alloy used for the negative electrode is cleaner than cadmium.

[0005] However, it has been found that a memory effect similar to that of a nickel-cadmium battery occurs as a practical problem. This is due to the formation of an inactive layer by a chemical reaction on the surface of the positive electrode active material used to maintain compatibility: nickel hydroxide.
Summary of the 5th Battery Symposium, p. 47). In other words, when shallow charge / discharge is repeated, discharge products that cannot react by normal charge / discharge are deposited on the surface of nickel hydroxide. Therefore, the positive electrode behaves as if the discharge has been completed, and apparently the battery cannot be discharged.

Further, like the nickel-cadmium battery, there is no improvement in self-discharge when the battery is left in a charged state. It is known that the alloy particles become finer in the process of undergoing the charge / discharge reaction in the hydrogen storage electrode, and it is said that the fined surface reacts with an alkaline aqueous solution as an electrolytic solution. It is considered that these problems cannot solve problems such as self-discharge.

On the other hand, non-aqueous electrolyte secondary batteries using lithium or a lithium alloy for the negative electrode have been actively researched and developed. This battery has excellent characteristics of high energy density, low self-discharge, and light weight.However, as the charge / discharge cycle progresses, lithium grows in a dendrite shape during charging, reaches the positive electrode, and causes an internal short circuit. It has many drawbacks, and is a major obstacle to practical application.

On the other hand, a lithium ion secondary battery using a carbon material for the negative electrode utilizes lithium doping / de-doping between carbon layers for the negative electrode reaction. Attention has been paid to the fact that no dendrite-like precipitation is observed at the time and good charge-discharge cycle characteristics are exhibited.

This battery uses a carbon material for the negative electrode and lithium cobalt oxide for the positive electrode. A normal battery reaction first proceeds by exchanging lithium ions dedoped from the positive electrode between the negative electrode carbon layer and the positive electrode active material layer like a catch ball. That is, since the lithium ions only enter and leave the positive and negative electrodes, the active material itself does not physically or chemically change unlike the nickel-metal hydride battery.

As described above, the lithium ion secondary battery using the carbon material for the negative electrode and the lithium cobalt oxide for the positive electrode has no memory effect and has a small self-discharge after being left in a charged state. It can be easily understood that the reason for having the characteristics lies in the basic system of the battery.

[0011]

As described above, although the lithium ion secondary battery is excellent in storage and reliability, demand for further improvement in characteristics has been increased with the recent expansion of applications. In particular, it is desired to maintain a dischargeable capacity even after being exposed to a severe environment such as a high temperature.

The present invention has been proposed in view of the above-mentioned circumstances, and has as its object to provide a battery which maintains high energy density and long cycle life while ensuring high reliability. I do.

[0013]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, in a battery using an electrode formed using an electrode material having a heat of wetting lower than a predetermined value. Found that the self-discharge characteristics after exposure to severe conditions such as high temperature were improved.

For example, in a lithium ion secondary battery, ions move between a positive electrode and a negative electrode via an electrolytic solution or a solid electrolyte, and the ions that reach the positive electrode or the negative electrode exchange electrons. At the same time, electrochemical deposition is performed by dissolving and depositing the metal if the active material is a metal, by allowing ions to enter and exit between layers if the compound is a layered compound, and by doping and undoping ions by using the alloy and other compounds. The reaction proceeds.

In order for this electrochemical reaction to occur, there must be an interface where the active material and the electrolyte or solid electrolyte are in contact. The interface is formed when a solvent in which the electrolyte salt is dissolved, a polymer matrix, or the like (hereinafter, referred to as a medium) comes into contact with the active material surface. Then, at that time, heat of wetting is generated.

If the heat of wetting is too large, smooth contact does not occur between the medium and the active material. For example, the medium reacts due to the catalytic activity of the surface functional groups of the active material, producing by-products. Then, when stored in a state before discharging (a charged state in the case of a secondary battery), a side reaction occurs between the active material in an active state and the by-product, thereby increasing self-discharge. Become. In addition, depending on the side reaction, the charge / discharge reaction site of the active material becomes inactive, and the capacity cannot be recovered.

As a result of further intensive studies, the present inventors have found that if a battery is formed using an electrode using an electrode material having a wetting heat of 1100 (mJ / g) or less, the wetting heat at the interface is reduced. Suppressed, smooth contact between the medium and active material occurs, by-products are unlikely to occur, self-discharge is suppressed, and self-discharge characteristics after exposure to severe conditions such as high temperatures are improved. Was found.

That is, the battery of the present invention has a pair of electrodes facing each other and an electrolyte phase interposed therebetween, and at least one of the pair of electrodes has a heat of wetting of 1100. (MJ / g).

Further, in the battery of the present invention, one of the pair of electrodes has a heat of wetting of 1100 (mJ / mJ / m 2).
g) It is formed using the following electrode materials, and this electrode is preferably used as a negative electrode.

In this case, it is preferable that the negative electrode is made of a material containing a carbon material which can be doped with and dedoped with lithium.

Further, in the battery of the present invention, the electrolyte phase is preferably a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent.

Further, in the battery of the present invention, it is preferable that the electrolyte phase contains a non-aqueous solvent and an electrolyte salt in a polymer compound matrix.

In the battery of the present invention, one of the pair of electrodes is a negative electrode made of a material containing lithium, and the other is a positive electrode made of a material containing a metal composite oxide. One of the pair of electrodes may be a negative electrode made of a material containing a lithium-doped, undoped carbon material, and the other may be a positive electrode made of a material containing a transition metal composite oxide containing lithium. preferable.

Further, in the battery of the present invention, the carbon material is preferably a non-graphitizable carbon material or a graphite material.

The battery of the present invention has a pair of electrodes facing each other and an electrolyte phase interposed therebetween. At least one of the pair of electrodes has a wetting heat of 1100 (mJ). / G) Since it is formed using the following electrode materials, smooth contact occurs between the active material surface and the medium of the electrolyte phase, and the generation of by-products, which are reaction products due to heat of wetting, is suppressed. During storage and storage in a state before discharging (a charged state in the case of a secondary battery), side reactions between the active material surface in an active state and the reaction product are reduced, and self-discharge is suppressed.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

The battery of the present invention has a pair of electrodes facing each other and an electrolyte phase interposed therebetween, and at least one of the pair of electrodes has a wetting heat of 1100 (mJ). / G) characterized by being formed using the following electrode materials.

In the battery of the present invention, one of the pair of electrodes has a heat of wetting of 1100 (mJ / mJ / m 2).
g) It is formed using the following electrode materials, and this electrode is preferably used as a negative electrode.

In this case, it is preferable that the negative electrode is made of a material containing a carbon material which can be doped and dedoped with lithium.

Further, in the battery of the present invention, the electrolyte phase is preferably a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent.

Further, in the battery of the present invention, it is preferable that the electrolyte phase contains a non-aqueous solvent and an electrolyte salt in a polymer compound matrix.

In the battery of the present invention, one of the pair of electrodes is a negative electrode made of a material containing lithium, and the other is a positive electrode made of a material containing a metal composite oxide. One of the pair of electrodes may be a negative electrode made of a material containing a lithium-doped, undoped carbon material, and the other may be a positive electrode made of a material containing a transition metal composite oxide containing lithium. preferable.

Further, in the battery of the present invention, the carbon material is preferably a non-graphitizable carbon material or a graphite material.

That is, the battery of the present invention has a pair of electrodes facing each other and an electrolyte phase interposed therebetween, and at least one of the pair of electrodes has a heat of wetting of 1100. (MJ / g) or less, a smooth contact occurs between the surface of the active material and the medium of the electrolyte phase, and the generation of by-products as reaction products due to heat of wetting is suppressed. When stored in a state before discharging (a charged state in the case of a secondary battery), side reactions between the active material surface in an active state and the reaction product are reduced, and self-discharge is suppressed. The self-discharge characteristics after being exposed to a high temperature or the like are greatly improved.

Further, in particular, the above-mentioned electrolyte phase is a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, or the above-mentioned one pair, wherein the polymer compound matrix contains a non-aqueous solvent and an electrolyte salt. One of the electrodes is a negative electrode made of a material containing lithium, and the other is a positive electrode made of a material containing a metal composite oxide, or one of the pair of electrodes is doped or dedoped with lithium. The carbon material is a non-graphitizable carbon material or a graphite material, which is a negative electrode made of a material containing a possible carbon material and the other is a positive electrode made of a material containing a transition metal composite oxide containing lithium. , A high energy density and a long cycle life are maintained.

FIG. 1 shows an example in which the present invention is applied to a non-aqueous electrolyte battery as an example of the battery according to the present invention.

As shown in FIG. 1, the nonaqueous electrolyte secondary battery comprises a positive electrode 3 having positive electrode mixture layers 2 a and 2 b formed on both surfaces of a positive electrode current collector 1, and a negative electrode current collector 4. A negative electrode 6 having negative electrode mixture layers 5a and 5b formed on both surfaces thereof and a separator 7 which is a microporous film made of polypropylene, polyethylene, or the like.
And wound into a wound electrode body, and housed in a battery can 9 with insulators 8 placed on top and bottom of the wound electrode body. Note that a center pin 15 is inserted into the center of the wound electrode body.

A battery cover 10 is attached to the battery can 9 by caulking through a sealing gasket 11,
Each is electrically connected to a positive electrode or a negative electrode via a positive electrode lead 12 and a negative electrode lead 13, respectively, and is configured to function as a positive electrode or a negative electrode of a battery.

However, in this battery, a current interrupting thin plate 14 is provided as a safety device, and the positive electrode lead 12 is attached to the current interrupting thin plate 14 by welding, and the battery is connected via the current interrupting thin plate 14. The electrical connection with the lid 10 is achieved.

In the battery having such a configuration,
When the pressure inside the battery rises, the current interrupting thin plate 14
Is pushed up and deformed. Then, the positive electrode lead 12 is cut leaving a portion welded to the current interrupting thin plate 14, and the current is interrupted.

In the battery to which the present invention is applied, any of the materials usually used as a mixture layer or a current collector constituting the positive electrode 3 and the negative electrode 6 can be used.

First, the positive electrode mixture layers 2a and 2b are configured to contain a positive electrode material, a conductive agent and a binder.

As the positive electrode material, any of the general positive electrode materials used for nonaqueous electrolyte batteries can be used. The positive electrode material is not particularly limited, and oxides, sulfides,
Nitride, alloy materials, silicon compounds, lithium-containing compounds, and composite metal compounds can be used.

For example, in the case of a primary battery, M _x O _y represented by MnO ₂ (M: one of transition metals, x ≧ 1, y ≧
The oxide of 1) or a secondary battery contains a sufficient amount of Li, for example, the general formula LiMO ₂ (where M is C
o, at least one of Ni, Mn, Fe, Al, V and Ti
Indicates the species. ), A composite metal oxide composed of lithium and a transition metal, an intercalation compound containing Li, and the like can be used.

When the later-described negative electrode material has sufficient lithium, a composite transition metal oxide represented by M _x O _y (where M represents at least one transition metal) is used. When lithium is not contained in the negative electrode, it is preferable that the intercalation compound containing Li contains a sufficient amount of Li. For example, the general formula LiMO ₂ (where M is Co, Ni, Mn , Fe, Al, V, and Ti) are preferable. A composite metal oxide composed of lithium and a transition metal represented by the formula:

In particular, since the present invention aims at achieving a high capacity, the positive electrode is 250 (mAh) per 1 (g) of the negative carbonaceous material in a steady state (for example, after repeating charging and discharging about 5 times). ) It is necessary to include Li corresponding to the charge / discharge capacity of at least 300, and more preferably to include Li corresponding to the charge / discharge capacity of 300 (mAh) or more.

It is not always necessary that Li be entirely supplied from the positive electrode material. As a result, the carbonaceous material 1
It suffices that Li (equivalent to a charge / discharge capacity of 250 (mAh) or more per g) exists. The amount of Li is determined by measuring the discharge capacity of the battery.

In the battery of this example to which the present invention is applied, the heat of wetting of these positive electrode materials is 1100 (mJ /
g) It is preferable that:

As a conductive agent for imparting conductivity to the positive electrode and a binder for holding the positive electrode material on the positive electrode current collector, those commonly used can be used.

For example, graphite and carbon black are suitably used as the conductive agent, and fluorine resins such as polyvinylidene fluoride are preferably used as the binder.

The negative electrode mixture layers 5a and 5b each include a negative electrode material and a binder.

As the negative electrode material, any of the general negative electrode materials used for non-aqueous electrolyte batteries can be used.

For example, as a negative electrode material of a primary battery or a secondary battery, alkali metals such as Li, Na, K, Ca, Mg, alkaline earth metals, aluminum, etc. can be used.

Those which cause an alloying reaction with an alkali metal such as lithium can be appropriately selected and used. As a metal that causes an alloying reaction with lithium metal,
Examples include Al, Bi, Cd, Pb, Sn, Si, and Zn. Examples of alloys or intermetallic compounds that have already been made include LiB, β-LiAl / Cu, and Cd / S
n, Bi / Cd, Pb / Cd, Cd / Sn, Bi / Cd
/ Pb and Pb / Cd / Sn can also be used.

In the case of a Li-ion secondary battery, a carbon material and / or metal oxide capable of doping / dedoping lithium can be used.

As the carbon material, a graphite material, a graphitizable carbon material, and a non-graphitizable carbon material can be selected.

As the above non-graphitizable carbon material, (00
2) The plane spacing is 0.37 (nm) or more and the true density is 1.70.
(G / cm ³ ), Differential thermal analysis (DTA) in air
In this case, a material exhibiting a physical parameter that does not have an exothermic peak at 700 (° C.) or more is preferable. As a typical example of the non-graphitizable carbon material, furfuryl alcohol or a furfural homopolymer or copolymer, or a furan resin obtained by copolymerization with another resin is calcined and carbonized.

Next, the production of the non-graphitizable carbon material will be described. Examples of the starting organic material include a phenol resin, an acrylic resin, a vinyl halide resin, a polyimide resin, a polyamide imide resin, a polyamide resin,
Conjugated resins such as polyacetylene and poly (p-phenylene), cellulose and derivatives thereof, and any organic polymer compounds can be used. Also, a petroleum pitch having a specific H / C atomic ratio into which a functional group containing oxygen is introduced (so-called oxygen cross-linking) is melted in a carbonization process (400 (° C.) or more), similarly to the furan resin. Will not
The final non-graphitizable carbon material remains in the solid state.

As the petroleum pitch, coal tar,
Distillation from tar bottoms, asphalt, etc. obtained by high-temperature pyrolysis of ethylene bottom oil, crude oil, etc. (vacuum distillation, atmospheric distillation,
Steam distillation), thermal polycondensation, extraction, chemical polycondensation and the like. At this time, the H / C atomic ratio of the petroleum pitch is important, and in order to obtain non-graphitizable carbon, this H / C
It is necessary to set the C atomic ratio to 0.6 to 0.8.

Means for introducing a functional group containing oxygen into these petroleum pitches is not limited. For example, a wet method using an aqueous solution of nitric acid, mixed acid, sulfuric acid, hypochlorous acid or the like, or an oxidizing gas (air, oxygen). A dry method, and a reaction with a solid reagent such as sulfur, ammonium nitrate, ammonium persulfate, and ferric chloride are used.

The oxygen content is not particularly limited, but is preferably at least 3 (%), more preferably at least 5 (%), as disclosed in JP-A-3-25253. This oxygen content affects the crystal structure of the finally manufactured carbon material, and when the oxygen content is within this range, the (002) plane spacing is 0.37 (nm) or more, and the The DTA has no exothermic peak at 700 (° C.) or more, and the negative electrode capacity is increased.

Further, the compound mainly containing phosphorus, oxygen and carbon disclosed in Japanese Patent Application Laid-Open No. 2-48184 also shows the same physical property parameters as the above-mentioned non-graphitizable carbon material, It can be used as an electrode material. Furthermore, any other organic material can be used as long as it becomes non-graphitizable carbon through a solid-phase carbonization process by oxygen crosslinking treatment or the like, and the treatment method for oxygen crosslinking is not limited.

When a carbon material is obtained by using the above organic material, for example, after carbonizing at 300 to 700 (° C.), the temperature is raised at a rate of 1 to 100 (° C.) per minute, and the ultimate temperature is 900 to 1300.
(° C.), and baking may be performed under the conditions of a holding time at the ultimate temperature of about 0 to 30 hours. Of course, in some cases, the carbonization operation may be omitted. The obtained carbon material is pulverized and classified to be used as a negative electrode material. This pulverization may be performed before or after carbonization, calcination, high-temperature heat treatment, or in a temperature-raising process.

The present invention is particularly effective in a battery using a graphite material for a negative electrode. The graphite material will be described below.

The usable graphite material preferably has a true density of 2.1 (g / cm ³ ) or more, and has a true density of 2.18 (g / cm ³ ).
cm ³ ) or more is more preferable. In order to obtain such a true density, the (002) plane spacing obtained by the X-ray diffraction method is preferably less than 0.340 (nm), and more preferably 0.
Satisfies 335 (nm) or more and 0.337 (nm) or less, and the C-axis crystallite thickness of the (002) plane is 14.0 (nm).
It is necessary to be above.

A long cycle life can be obtained by using a graphite material having a bulk density of 0.4 (g / cm ³ ) or more according to the method described in JIS K-1469. still,
A graphite material having a bulk density of 0.5 (g / cm ³ ) or more is more preferable, and a graphite material having a bulk density of 0.6 (g / cm ³ ) is more preferable.

The above bulk density is determined by the method described in JIS K-1469. That is, a measuring cylinder having a capacity of 100 (cm ³ ) whose mass has been measured in advance is slanted, and 100 (cm ³ ) of the sample powder is gradually introduced into the measuring cylinder. Then, the total mass is measured at the minimum scale of 0.1 (g), and the mass of the sample powder is obtained by subtracting the mass of the measuring cylinder from the mass.

Next, a cork stopper is placed on the measuring cylinder into which the sample powder has been charged, and the measuring cylinder in this state is dropped 50 times from a height of about 5 (cm) onto the rubber plate.
As a result, since the sample powder in the measuring cylinder is compressed, the volume V of the compressed sample powder is read,
The bulk density (g / cm ³ ) is calculated by the equation (1).

D = W / V (1) where: D: bulk density (g / cm ³ ) W: mass of sample powder in measuring cylinder (g) V: sample powder in measuring cylinder after falling 50 times to the volume (cm ³⁾ longer cycle life, a range bulk density of the as graphite material, and the average value of shape parameters indicated by equation (2) using 125 following powder It is desirable.

X = (W / T) × (L / T) (2) where X: shape parameter T: thickness of the thinnest portion of powder L: length of powder in the major axis direction W: The length in the direction orthogonal to the major axis of the powder, that is, the powder shape of the graphite material is a flat columnar shape or a rectangular parallelepiped shape shown in FIGS. Assuming that the thickness of the thinnest portion of the graphite material powder is T, the length of the longest portion is L, and the length in a direction perpendicular to this portion is W, each of L and W is divided by T. The product of the obtained values is the shape parameter X. The smaller the shape parameter X, the higher the height with respect to the bottom area and the smaller the flatness.

A graphite material powder whose bulk density is within the above range and whose average value of the shape parameter X thus obtained (hereinafter referred to as “average shape parameter Xave.”) Is 125 or less is used. Since the negative electrode formed by using the graphite material has a low flatness of the graphite material, the electrode structure is further improved, and a longer life cycle characteristic can be obtained. If the average shape parameter Xave. Of the graphite material powder is 125 or less, the above effect can be obtained.
It is preferably 15 or less, more preferably 2 or more and 100 or less.

Further, in order to obtain high safety and reliability as a practical battery, in the particle size distribution obtained by a laser diffraction method, the cumulative 10 (%) particle size is 3 (μm) or more, and the cumulative It is desirable to use a graphite powder having a (%) particle size of 10 (μm) or more and a cumulative 90 (%) particle size of 70 (μm) or less.

The graphite powder to be filled in the electrode can be more efficiently filled if the particle size distribution has a certain width, and is preferably closer to the normal distribution. However, the battery may generate heat in an abnormal situation such as overcharging or the like, and when the distribution number of particles having a small particle size is large, the heat generation temperature tends to increase, which is not preferable.

When the battery is charged, lithium ions are inserted between the graphite layers, so that the crystallite expands by about 10% and presses the positive electrode and the separator in the battery, causing an internal short circuit or the like during the first charge. Although the initial failure is likely to occur, it is not preferable if the distribution of large particles is large because the failure occurrence rate tends to increase.

Therefore, by using graphite powder having a particle size distribution that is well-balanced from large particles to small particles, a practical battery with high reliability can be obtained. The shape of the particle size distribution can be filled more efficiently if it is closer to the normal distribution. However, in the particle size distribution obtained by the laser diffraction method, the cumulative 10 (%) particle size is 3 (μm) or more and the cumulative 50 (%) particle size It is desirable to use a graphite powder having a diameter of 10 (μm) or more and a cumulative 90 (%) particle size of 70 (μm) or less, and particularly a cumulative 90 (%).
When the (%) particle size is 60 (μm) or less, initial failure is greatly reduced.

In order to improve the heavy load characteristics as a practical battery, the average value of the breaking strength of graphite particles is 6.0.
(Kgf / mm ² ) or more. The load characteristics are influenced by the easiness of movement of ions at the time of discharge. Particularly, when there are many pores in the electrode, a sufficient amount of the electrolytic solution is present, so that good characteristics are exhibited.

On the other hand, a graphite material having high crystallinity has a hexagonal graphite network developed in the a-axis direction, and the c-axis crystallite is formed by stacking the graphite hexagonal meshes. Since it is a weak bond called the Wales force, it is easily deformed by stress, so when graphite particles are compression-molded and filled into electrodes, they are more easily crushed than carbonaceous materials fired at low temperatures, and voids are formed. Difficult to secure. Therefore, by using graphite powder particles having a high breaking strength, the particles are less likely to be crushed, and thus it becomes easier to form pores, so that the load characteristics can be improved. In order to obtain such good load characteristics, the average value of the breaking strength of the graphite particles is desirably 6.0 (kgf / mm ² ) or more.

As long as the graphite material has the above-mentioned crystallinity, true density, bulk density, shape parameter X, specific surface area, particle size distribution and particle breaking strength, even natural graphite can be used. As described above, artificial graphite obtained by carbonizing an organic material and further performing high-temperature treatment may be used.

Coal and pitch are typical examples of the organic material used as a starting material in producing the artificial graphite.

The pitch in the case of artificial graphite includes distillation (vacuum distillation, atmospheric distillation, steam distillation) from tars obtained by high-temperature pyrolysis of coal tar, ethylene bottom oil, crude oil, etc., asphalt, and thermal polycondensation. , Extraction, chemical polycondensation, etc., and others formed during wood carbonization. Further, it is also possible to use a polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, 3,5-dimethylphenol resin, or the like as a starting material and subject these to predetermined processing to obtain a pitch.

These coals and pitches exist in a liquid state at a maximum temperature of about 400 ° C. during the carbonization, and when held at that temperature, aromatic rings are condensed and polycyclic to form a laminated orientation, and thereafter, at about 500 ° C. At the above temperature, a solid carbon precursor, that is, semi-coke is formed. Such a process is called a liquid phase carbonization process, and is a typical production process of graphitizable carbon.

In addition, condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphene and pentacene, and other derivatives (for example, carboxylic acids, carboxylic anhydrides, carboxylic imides and the like thereof), Alternatively, mixtures, condensed heterocyclic compounds such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine, and derivatives thereof can also be used as raw materials.

A desired graphite material using the above organic material as a starting material is obtained by, for example, carbonizing the organic material in an inert gas stream such as nitrogen at 300 to 700 (° C.), and then in an inert gas stream. Heating rate 1 to 100 (° C) per minute, ultimate temperature 900 to 1500 (° C), holding time at the ultimate temperature 0 to 3
It is obtained by calcining under the condition of about 0 hour (the material which has passed through this process is a graphitizable carbon material), and further heat-treated at 2000 (° C.) or more, preferably 2500 (° C.) or more. Of course, in some cases, the carbonization or calcination operation may be omitted.

The produced graphite material is pulverized and classified to be used as a negative electrode material. This pulverization may be performed before or after carbonization or calcination or in a temperature raising process before graphitization, and finally, a heat treatment for graphitization is performed in a powder state. Furthermore, in order to obtain a graphite material powder having a high bulk density and a high breaking strength, it is desirable to heat-treat a carbon material molded product, graphitize it, and pulverize and classify the graphitized molded product.

The graphitized molded body generally comprises coke as a filler and binder pitch as a molding agent or a sintering agent, and after mixing and molding, the binder pitch is carbonized. And carbonized, and then graphitized. Further, it is possible to obtain a similar graphitized molded body by using a raw material in which moldability and sinterability are imparted to the filler itself. The graphitized molded body is pulverized and classified after the heat treatment and supplied to the negative electrode material. However, since the molded body itself has a high hardness, a material having a high bulk density and a high breaking strength is easily obtained as a pulverized powder.

Further, since it is composed of coke as a filler and binder pitch, it becomes polycrystalline after graphitization, and also contains elements such as sulfur and nitrogen as raw materials and emits as a gas at the time of heat treatment. Micropores accelerate the progress of lithium doping / dedoping reactions of the negative electrode material. Further, there is an advantage that the processing efficiency is high industrially.

Further, as the negative electrode material of the battery of the present invention, a metal oxide capable of doping / dedoping lithium can be used. As the metal oxide, an oxide containing a transition metal is preferable, and a crystalline compound or an amorphous compound mainly composed of iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, tin oxide, or the like is used as a negative electrode. In particular, a compound having a charge / discharge potential close to lithium metal is desirable.

Then, in the battery of this example to which the present invention was applied, the heat of wetting of these negative electrode materials was 1100 (mJ /
g) It is preferable that:

In the battery of this example to which the present invention is applied, at least one of the positive electrode material and the negative electrode material needs to have a heat of wetting of 1100 (mJ / g) or less.

In the non-aqueous electrolyte battery of the present example, a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, a gel electrolyte in which a non-aqueous solvent and an electrolyte salt are impregnated in a polymer matrix,
Any electrolytic solution (electrolyte) such as inorganic and organic solid electrolytes can be appropriately selected and used. As the non-aqueous solvent for dissolving the electrolyte, it is premised that a solvent having a relatively high dielectric constant such as ethylene carbonate (EC) is used as the main solvent. There is a need to.

As the high dielectric constant solvent, propylene carbonate (PC), butylene carbonate, vinylene carbonate, sulfolane, butyrolactone, valerolactone and the like are preferable. As the low-viscosity solvent, symmetrical or asymmetrical chain carbonates such as diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate are preferable, and good results can be obtained by mixing two or more kinds. Is obtained. In particular, when a graphite material is used for the negative electrode, ethylene carbonate (EC) is preferred as a non-aqueous solvent, and a compound having a structure in which a hydrogen atom of ethylene carbonate (EC) is replaced with a halogen element is also suitable.

Further, although it is reactive with a graphite material, such as propylene carbonate (PC), ethylene carbonate (EC) as a main solvent or a compound having a structure in which a hydrogen atom of ethylene carbonate (EC) is substituted with a halogen element, etc. On the other hand, good characteristics can be obtained by substituting a very small amount of the part with the second component solvent. As the second component solvent, propylene carbonate (PC), butylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane, γ-butyrolactone, valerolactone, tetrahydrofuran,
-Methyltetrahydrofuran, 1,3-dioxolane,
4-methyl-1,3-dioxolan, sulfolane, methylsulfolane and the like can be used, and the addition amount is preferably less than 10 (vol%).

As the electrolyte dissolved in such a non-aqueous solvent, any electrolyte used in this type of battery can be used by mixing one or more kinds. For example, LiPF ₆ is suitable, but other LiClO ₄ , LiAsF ₆ , Li
BF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, C
F ₃ SO ₃ Li, LiN (CF ₃ SO ₂ ) ₂ , LiC
(CF ₃ SO ₂ ) ₃ , LiCl, LiBr and the like can also be used.

The separator 7 is not particularly limited, and examples thereof include a woven fabric, a nonwoven fabric, and a microporous synthetic resin membrane. In particular, a synthetic resin microporous membrane is preferably used, and among them, a polyolefin-based microporous membrane is suitably used in terms of thickness, film strength, film resistance, and the like. In particular,
A microporous membrane made of polyethylene and polypropylene or a microporous membrane obtained by combining these is used.

The shape of the current collector of the electrode is not particularly limited, but a foil shape, a mesh shape, a mesh shape such as expanded metal, or the like is used. As a material used for the positive electrode current collector 1, for example, aluminum, stainless steel, nickel, or the like is preferably used. As a material used for the negative electrode current collector 4, for example, copper, stainless steel, nickel, or the like is preferably used.

The material for forming the battery can 9 is as follows.
Examples include iron, nickel, stainless steel, and aluminum. If electrochemical corrosion occurs in the non-aqueous electrolyte during operation of the battery using these, plating may be performed.

[0097]

EXAMPLES Next, in order to confirm the effects of the present invention, the following experiments were conducted. In this experimental example, the heat of wetting of the negative electrode material used for the negative electrode was changed to change the heat of FIG.
A non-aqueous electrolyte battery as shown in (1) was manufactured, and these characteristics were investigated.

<Production of Sample> First, a negative electrode material was produced.

(Sample 1) To 100 parts by weight of needle coke as a filler, 50 parts by weight of petroleum pitch as a binder were added, mixed at about 100 (° C.), and compression-molded with a press to obtain a carbon molded body. Was obtained. A carbon material molded body obtained by heat-treating this precursor at 1000 (° C) or less is further impregnated with a binder pitch melted at 200 (° C) or less, and treated at 1000 (° C).
The pitch impregnation / firing process was repeated several times. Thereafter, the carbon molded body was heat-treated in an inert atmosphere at a maximum of 3000 (° C.) to obtain a graphite molded body. And the thing which grind | pulverized this graphite molded object was used as sample 1.

(Sample 2) The pitch impregnation / firing step was repeated several times in the same manner as in Sample 1 described above, followed by pulverization to remove fine particles by classification. This powder was heat-treated in an inert atmosphere at a maximum of 3000 (° C.) to obtain a graphite sample powder, which was designated as Sample 2.

(Sample 3) Acenaphthylene was heat-treated at 430 (° C.) for 10 hours in an inert atmosphere to obtain 530
(° C.) to obtain semi-coke. Thereafter, the semi-coke is heat-treated at 1100 (° C.) in an inert atmosphere,
This was heat-treated in an inert atmosphere at a maximum of 3000 (° C.). The heat-treated product was pulverized to prepare a sample, which was designated as Sample 3.

(Sample 4) Semi-coke was obtained in the same manner as in Sample 3 described above, heat-treated at 1100 (° C.) in an inert atmosphere, pulverized, and fine particles were removed by classification. This powder was heat-treated in an inert atmosphere at a maximum of 3000 (° C.) to obtain a graphite sample powder, which was designated as Sample 4.

(Sample 5) Petroleum pitch in an inert atmosphere 4
What was heat-treated at 10 (° C) for 20 hours was heated to 550 (° C) to obtain semi-coke. Thereafter, the semi-coke was heat-treated at a maximum of 1200 (° C.), and this was heat-treated at a maximum of 3000 (° C.) in an inert atmosphere. The heat-treated product was pulverized to prepare a sample, which was designated as Sample 5.

(Sample 6) Semi-coke was obtained in the same manner as in the above-mentioned sample 5, heat-treated at a maximum of 1200 (° C.), and then pulverized to remove fine particles by classification. This powder is heat-treated in an inert atmosphere at a maximum of 3000 (° C.)
A graphite sample powder was obtained, and this was designated as Sample 6.

(Sample 7) Acenaphthylene was heat-treated in an inert atmosphere at 400 (° C.), and matrix organic matter was removed with a solvent to obtain mesophenous microspheres (mesocarbon microbeads, hereinafter referred to as MCMB). This M
After heat-treating the CMB particles in an inert atmosphere at 1000 (° C.) or less, the CMB particles are heated in an inert atmosphere to a maximum of 3000.
A heat treatment was performed at (° C.) to prepare a sample, which was designated as Sample 7.

(Sample 8) MCMB particles as a carbon precursor were obtained in the same manner as in Sample 7, and pressed so that the average of the deformation rate (volume change rate of the powder filling) of the particles was 0.5. To obtain a precursor of a carbon molded body. A carbon material molded body obtained by heat-treating this precursor at 1000 (° C.) or less was heat-treated at a maximum of 3000 (° C.) in an inert atmosphere to obtain a graphitized molded body. This was ground to obtain a graphite sample powder, which was designated as Sample 8.

(Sample 9) MCMB particles were obtained in the same manner as in Sample 7, and the deformation rate of the particles (volume change rate of the powder filling)
Was compression-molded with a press so that the average was 0.5, to obtain a precursor of a carbon molded body. The precursor was pulverized to remove fine particles by classification, and then heat-treated at 1000 (° C.) or lower to obtain a carbon material. This powder is heat-treated at a maximum of 3000 (° C.) in an inert atmosphere to produce a graphite sample powder,
This was designated as Sample 9.

(Sample 10) MCMB was performed in the same manner as in Sample 7.
Particles were obtained and compression-molded by a press so that the average of the deformation rate (volume change rate of the powder filling) of the particles was 0.5 to obtain a precursor of a carbon molded body. 1000% of this precursor
A heat treatment was performed at (° C.) or lower to obtain a molded carbon material. After the carbon material molded body was pulverized to remove fine particles by classification, the powder was heat-treated at a maximum of 3000 (° C.) in an inert atmosphere to produce a graphite sample powder, which was designated as Sample 10.

(Sample 11) A graphite sample powder was prepared in the same manner as in Sample 9, except that the average of the deformation rate (volume change rate of the powder filling) of the MCMB particles was 0.1. 11 was set.

(Sample 12) A graphite sample powder was prepared in the same manner as in Sample 9, except that the average of the deformation rate (volume change rate of the powder filling) of the MCMB particles was 0.3. It was set to 12.

(Sample 13) A graphite sample powder was prepared in the same manner as in Sample 9, except that the average of the deformation rate (volume change rate of the powder filling) of the MCMB particles was 0.7. 13.

(Sample 14) A graphite sample powder was prepared in the same manner as in Sample 9, except that the average of the deformation rate of the MCMB particles (volume change rate of the powder filling) was 0.8. It was set to 14.

(Sample 15) The pitch produced by reacting naphthalene and HF / BF ₃ at 250 (° C.) and 8 (hr) in an autoclave was mixed at 380 (° C.) in an inert atmosphere at 380 (° C.).
0 (hr) and heat-treated to 540 (° C.)
I got semi-coke. Thereafter, the semi-coke was heat-treated in an inert atmosphere at 1100 (° C.) and then heat-treated in an inert atmosphere at a maximum of 3000 (° C.). The heat-treated product was pulverized into a sample, which was referred to as Sample 15.

(Sample 16) Semi-coke was obtained in the same manner as in Sample 15, and the fine particles of this semi-coke were removed by classification to produce a graphite material sample powder.

(Sample 17) Semi-coke was obtained in the same manner as in Sample 15, which was heat-treated at 1100 (° C.) in an inert atmosphere, pulverized, and fine particles were removed by classification. This powder was heat-treated at a maximum of 3000 (° C.) in an inert atmosphere to obtain a graphite sample powder, which was designated as Sample 17.

(Sample 18) Semi-coke was obtained in the same manner as in Sample 15, crushed, fine particles were removed by classification, and then heat-treated at 1100 (° C.) to obtain a carbon material. This powder was heat-treated at a maximum of 3000 (° C.) in an inert atmosphere to obtain a graphite material sample powder, which was designated as Sample 18.

(Sample 19) The pitch used in Sample 15 was heat-treated in an inert atmosphere at 410 (° C.) for 20 (hr),
After cooling, compression molding was performed with an isostatic press. This was heated to 540 (° C.) in an inert atmosphere and then pulverized to remove fine particles by classification. Then, in an inert atmosphere,
A heat treatment was performed at 100 (° C.), and a heat treatment was further performed at a maximum of 3000 (° C.) in an inert atmosphere to produce a graphite sample powder.

(Sample 20) A natural graphite produced in China was washed with hydrochloric acid to prepare a sample from which impurities were removed.
And

(Sample 21) A sample was prepared by removing the fine particles of the sample 20 by classification.

(Sample 22) The petroleum pitch was kept at 425 (° C.) in an inert atmosphere for 5 (hr), and the softening point was 220
(° C.) petroleum mesophase pitch was obtained. At this time,
The mesophase content was 92 (%). The obtained petroleum-based mesoface pitch was spun at 320 (° C.) using a circular discharge hole to obtain a precursor fiber. Then 260
(° C.), 3000 in an inert atmosphere
The sample was heat-treated at (° C.) and pulverized to prepare a sample.

(Sample 23) The precursor fiber of Sample 22 was infusibilized at 260 (° C.) and then pulverized to remove fine particles by classification. Then, 1100 in an inert atmosphere
(° C) or less and up to 3 in inert atmosphere
A heat treatment was performed at 000 (° C.) to obtain a graphite material sample powder.

(Sample 24) Temperature 1100 of Sample 22
Fibrous carbon obtained by calcining at (° C.) was pulverized, and fine particles were removed by classification. Then up to 30 in an inert atmosphere
Heat treatment was performed at 00 (° C.) to obtain a graphite material sample powder.

(Sample 25) The precursor fiber of Sample 22 was infusibilized at 260 ° C., pulverized to remove fine particles by classification, and compression-molded by a hydrostatic press. Thereafter, carbonization was performed at 1,000 (° C.) or less in an inert atmosphere, and heat treatment was performed at a maximum of 3000 (° C.) in an inert atmosphere to obtain a graphite material sample powder.

Subsequently, these negative electrode materials, Samples 1 to 2
X-ray parameters, bulk density, average particle size and particle size distribution of 5,
Heat of wetting, volume and volume loss were measured.

The above X-ray parameters were measured by the powder X-ray diffraction method (Gakushin method), the bulk density was measured by the method described above, and the average particle size and particle size distribution were measured by the laser diffraction method. . The methods for measuring the heat of wetting, capacity and capacity loss are described below.

First, a method of measuring the heat of wetting will be described. The graphite material sample powder to be a sample was vacuum-dried and then vacuum-injected into a special glass ampule. On the other hand, the solvent was similarly sealed in a glass ampoule. These were set on a multi calorie meter MMC-551 (model name) manufactured by Tokyo Riko Co., Ltd., and measured under the following conditions. That is, 1 g of each sample was used as a sample, and propylene carbonate 22 was used as a solvent.
(Cc) and set the sample under vacuum drying conditions to 200 (° C).
× 3 (hr), the measurement temperature was 23 (° C.), the stirring was performed at a rotation speed of 60 (rpm), and the data sampling interval was 1 (sec).

A method for measuring one of the capacitance and the capacitance loss will be described.
The measurement of the capacity and the capacity loss of the graphite material sample powder was performed by preparing a test cell. First, a graphite material sample powder was heated in an argon atmosphere at a heating rate of about 30 (° C./min) and an ultimate temperature of 600 ° C.
(° C.) and a pre-heat treatment is performed under the condition that the ultimate temperature holding time is 1 hour. The pre-heat treatment is performed immediately before the preparation of the negative electrode mix described below.

Then, the preheat-treated graphite material sample powder, 10 (wt%) equivalent of polyvinylidene fluoride as a binder, and dimethylformamide as a solvent are mixed and dried to prepare a negative electrode mix. Then, 37 (mg) of the mixture thus adjusted was collected,
A working electrode is formed by molding into a pellet having a diameter of 15.5 (mm) together with the Ni mesh.

Then, the produced working electrode is incorporated in a test cell having the following cell structure, and the capacity and the capacity loss per 1 g of the carbon material are measured. The test cell is a coin-shaped cell having a diameter of 20 (mm) and a thickness of 2.5 (mm), using lithium metal as a counter electrode, using a polypropylene porous membrane as a separator, and using an electrolytic cell. As a liquid, a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (in a volume ratio of 1:
1) LiPF ₆ dissolved at a concentration of 1 (mol / 1000 cc) was used.

In measuring the capacity and the capacity loss, doping / dedoping (charging / dedoping) lithium into the carbon material was performed.
Discharge: Strictly speaking, in this test method, the process of doping lithium into the carbonaceous material is discharge, not charge, and the process of undoping is charge, not discharge. For convenience, the doping process is referred to as charging, and the undoping process is referred to as discharging. ) Was performed under the following conditions. The charging condition (lithium doping condition) was a constant current of 1 (mA) per cell and a constant voltage of zero (mV) (L
i / Li ⁺ ) and zero (μA).
One discharge condition (lithium de-doping condition) was a constant current of 1 (mA) per cell and the terminal voltage was cut off voltage 1.5.
(V).

The capacity per 1 g of carbon material was calculated from the amount of discharge electricity when charging and discharging were performed under such conditions. In addition, capacity loss was determined by subtracting the amount of discharged electricity from the amount of charged electricity. Regardless of the carbon material used, the amount of discharge electricity is smaller than the amount of charge electricity in the initial charge and discharge. This is because the carbon material usually has a quantity of electricity that is not discharged even when charged. Here, the electric capacity which is not discharged even if charged is defined as capacity loss for convenience. The value of the capacity loss is also important in evaluating the negative electrode material.

Next, a negative electrode 6 was prepared using the above-mentioned samples 1 to 25 as negative electrode materials.

That is, 90 parts by weight of each of the above samples and 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed to prepare a negative electrode mixture. ) To prepare each negative electrode mixture.

Subsequently, a negative electrode current collector 4 having a thickness of 10 μm
m), a strip-shaped copper foil is prepared, and each of the negative electrode mixtures is uniformly applied to both surfaces of the negative electrode current collector 4 and dried, and then compression molded at a constant pressure to form negative electrode mixture layers 5a and 5b. The negative electrode 6 using each negative electrode mixture was formed.

Subsequently, a positive electrode 3 was produced. First, a positive electrode active material was produced. That is, lithium carbonate 0.5 (mo
l) and 1 (mol) of cobalt carbonate were mixed, and this mixture was fired in air at a temperature of 900 (° C) for 5 (hr).
X-ray diffraction measurement was performed on the obtained material.
It coincided well with the peak of LiCoO ₂ registered in the PDS file.

This LiCoO ₂ is pulverized, and a LiCO ₂ having a cumulative 50 (%) particle size of 15 (μm) obtained by a laser diffraction method is obtained.
oO ₂ powder. And this LiCoO ₂ powder 95
Parts by weight and 5 parts by weight of lithium carbonate powder, 91 parts by weight of this mixture, 6 parts by weight of graphite as a conductive agent,
A positive electrode mixture was prepared by mixing 3 parts by weight of polyvinylidene fluoride as a binder, and dispersed in N-methylpyrrolidone to prepare a slurry (paste) to prepare a positive electrode mixture.

Subsequently, as the positive electrode current collector 1, a thickness of 20 (μ
m), the above-described positive electrode mixture is uniformly applied to both surfaces of the positive electrode current collector 1, dried, and then compression-molded at a constant pressure to form the positive electrode mixture layers 2a and 2b. Was formed.

Next, a negative electrode 6 using each of the above negative electrode mixtures was prepared.
And the positive electrode 3 were combined to assemble a battery. That is, each of the negative electrode 6 and the positive electrode 3 is laminated via a separator 7 which is a microporous polypropylene film having a thickness of 25 (μm), and then wound many times to form a wound electrode body having an outer diameter of 18 (mm). Formed.

The wound electrode body was housed in a nickel-plated iron battery can 9. Further, insulating plates 8 are arranged on both upper and lower surfaces of the wound electrode body, and a positive electrode lead 12 made of aluminum is led out of the positive electrode current collector 1 and is attached to the battery cover 10.
The negative electrode lead 13 made of nickel was led out of the negative electrode current collector 4 and welded to the battery can 9.

Subsequently, 1 (mol / 100) of LiPF ₆ was placed in an equal volume mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in the battery can 9.
(0 cc) was injected. Then
The battery can 9 is caulked through a sealing gasket 11 which also covers the surface with asphalt and also insulates, thereby fixing the current interrupting thin plate 14 having the current interrupting mechanism, the PTC element 16 and the battery lid 10, and sealing the battery. To maintain the nature,
Twenty-five types of cylindrical non-aqueous electrolyte secondary batteries according to the type of the negative electrode mixture having a diameter of 18 (mm) and a height of 65 (mm) were obtained.

The 25 types of batteries produced as described above were charged at a maximum charging voltage of 4.2 (V) and a charging current of 1 (A) at 3
(Hr) Charge, 2.5 (V) at current 0.7 (A)
To discharge capacity C-1. Thereafter, the battery was charged at 1 (A) with a maximum charging voltage of 4.2 (V) at a charging current of 3 (h).
r) The battery was charged and stored for one month in an atmosphere at a temperature of 45 (° C.). Here, the battery was discharged at a current of 0.7 (A) to 2.5 (V), and the capacity C-2 was measured. And C-1 to C-2
Was subtracted by C-1 to determine the self-discharge rate. Tables 1 and 2 also show the types and characteristics of the negative electrode materials used and the self-discharge rate in the case of a battery. Also,
FIG. 4 shows the relationship between the heat of wetting of the negative electrode material and the self-discharge rate obtained from these results. In FIG. 4, the horizontal axis represents the self-discharge rate, and the vertical axis represents the heat of wetting.

[0142]

[Table 1]

[0143]

[Table 2]

As is clear from the results shown in Tables 1 and 2 and FIG. 4, in the battery in which the heat of wetting of the negative electrode material is 1100 (mJ / g) or less, the self-discharge rate of the battery is 25 (%) or less. The capacity to discharge can be maintained even after being exposed to a severe environment such as high temperature such as storage for one month in an atmosphere at a temperature of 45 (° C), and high reliability is ensured. Was confirmed.

[0145]

As described above, the battery according to the present invention has a pair of electrodes facing each other, and an electrolyte phase is interposed between them. Since at least one of the electrodes is formed using an electrode material having a wetting heat of 1100 (mJ / g) or less, self-discharge during storage and storage is suppressed, and self-discharge characteristics after exposure to high temperatures or the like are reduced. It is greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a battery according to the present invention.

FIG. 2 is a perspective view showing an example of a powder shape of a graphite material.

FIG. 3 is a perspective view showing another example of the powder shape of a graphite material.

FIG. 4 is a characteristic diagram showing a relationship between a self-discharge rate and heat of wetting.

[Explanation of symbols]

1 positive electrode current collector, 2a, 2b positive electrode mixture layer, 3 positive electrode,
4 negative electrode current collector, 5a, 5b negative electrode mixture layer, 6 negative electrode,
7 separator, 12 positive electrode lead, 13 negative electrode lead

Claims (9)

[Claims] 1. A battery comprising a pair of electrodes facing each other and an electrolyte phase interposed therebetween, wherein at least one of the pair of electrodes has a heat of wetting of 11 or more.
A battery formed by using an electrode material of 00 (mJ / g) or less. 2. One of the pair of electrodes is formed by using an electrode material having a heat of wetting of 1100 (mJ / g) or less, and the electrode serves as a negative electrode. The battery according to 1. 3. The battery according to claim 2, wherein the negative electrode is made of a material containing a carbon material that can be doped with and dedoped with lithium. 4. The battery according to claim 1, wherein the electrolyte phase is a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent. 5. The battery according to claim 1, wherein the electrolyte phase contains a non-aqueous solvent and an electrolyte salt in a polymer compound matrix. 6. The method according to claim 1, wherein one of the pair of electrodes is a negative electrode made of a material containing lithium, and the other is a positive electrode made of a material containing a metal composite oxide. battery. 7. One of the pair of electrodes is a negative electrode made of a material containing a lithium-doped and undoped carbon material, and the other is a positive electrode made of a material containing a transition metal composite oxide containing lithium. The battery according to claim 1, wherein: 8. The battery according to claim 7, wherein the carbon material is a non-graphitizable carbon material. 9. The battery according to claim 7, wherein the carbon material is a graphite material.