JP2001143755A - Non-aqueous electrolyte secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control precipitation of a lithium metal into a negative electrode in guide charging prohibiting deterioration of discharging capacity in the case of discharging at high efficiently. SOLUTION: A positive electrode is constituted so that a porosity of polymer electrolyte is included in the inner part of a positive electrode and a negative electrode is constituted so that it includes the porosity of polymer electrolyte integrated with its surface. It is constituted so that the porosity of polymer is not charged into the inner part of the negative pole. A solvent extracting method forms the porosity of polymer electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Currently, commercially available lithium secondary batteries include a positive electrode composed of a transition metal composite oxide such as lithium cobalt oxide, a negative electrode composed of a carbon-based material such as graphite, a separator such as polyethylene and polypropylene, and ethylene carbonate. Li in the mixed solvent of carbonate
Lithium salts such as PF ₆ is made of used and dissolved organic electrolyte, in order to more stable ones batteries, poor chemical reactivity instead of combustible organic electrolyte Attempts have been made to use solid polymer electrolytes.

Recently, attempts have been made to use a gel-like polymer electrolyte obtained by wetting or swelling a polymer with an organic electrolyte to improve conductivity.
Further, in order to improve the diffusion rate of lithium ions, for example, JP-A-8-195220 and JP-A-9-25
As described in Japanese Patent No. 9923, a battery excellent in high-rate charge / discharge characteristics and safety is obtained by using a gel-like porous polymer electrolyte as a separator or by supporting it in electrode pores. It has been proposed to produce

[0004]

The use of a gel-like porous polymer electrolyte involves the formation of a large number of pores in a conductive gel-like polymer electrolyte, and the retention of an electrolyte in these pores by lithium. The purpose of the present invention is to improve the diffusion rate of ions, and by using this as a separator, it can also serve as a separator and reduce the amount of electrolytic solution held in the battery, allowing it to be supported in electrode pores. Thus, the amount of the electrolyte held in the electrode holes can be reduced. Further, the diffusion rate of lithium ions equivalent to that of the electrolytic solution can be maintained, and high-rate charge / discharge characteristics can be secured.

When such a gel-like porous polymer electrolyte is used, in order to reduce the amount of the electrolyte solution in the battery, the pores of the positive electrode and the negative electrode are filled with the porous polymer electrolyte, and the separator is used. It is preferable to use this porous polymer electrolyte.

[0006] Further, regardless of whether a porous polymer electrolyte is used as a separator, if a gap is formed at the boundary between the separator and the electrode, this space becomes a space where no ionic medium is present, and the reaction is hindered. In order to prevent this, it is necessary to inject an excessive amount of electrolyte so that the electrolyte is also held in this gap. It is preferable to form a porous polymer layer to improve the adhesion to the separator.

[0007] However, although the above-described structure can reduce the amount of the electrolyte and reduce the heterogeneous reaction, there is still a problem that lithium metal is deposited on the negative electrode during rapid charging. In addition, a new problem arises in that a battery having a significantly reduced discharge capacity occurs when high-rate discharge is performed.

An object of the present invention is to solve such a problem.

[0009]

A non-aqueous electrolyte secondary battery according to the present invention is a battery having a porous polymer electrolyte in an electrode, wherein a positive electrode has a porous polymer electrolyte therein,
The negative electrode is characterized by having a porous polymer electrolyte integrated on its surface.

In the battery of the present invention, the filling ratio of the porous polymer provided in the inside of the positive electrode differs from that in the inside of the negative electrode, so that the inside of the positive electrode is more polarized. If the upper limit of the battery voltage at the time of charging is controlled to a predetermined value, the negative electrode does not have a lithium potential or a potential lower than that, and the electrolytic deposition of lithium on the negative electrode is suppressed. For this reason, it becomes possible to manufacture a battery in which lithium electrolytic deposition does not occur even when rapid charging is performed.

Further, in the battery of the present invention, the porous polymer electrolyte integrally formed on the surface of the electrode is formed only on the surface of the negative electrode. In this case, the discharge capacity is prevented from being reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be further described by describing embodiments of the battery of the present invention.

The non-aqueous electrolyte battery of the present invention is characterized in that the electrode is provided with a porous polymer electrolyte. The term "porous polymer electrolyte" refers to a polymer electrolyte having pores formed by, for example, a solvent extraction method. And FIG.
As shown in FIG. 10, when a three-dimensional network structure having a large number of holes is formed in the form of a film, or when formed in a small hole inside an electrode, only a part thereof is viewed as a hole. When a thread-like polymer is stretched around (in this case, it can be seen that a structure having a large number of active material particles incorporated in a film having a three-dimensional network)
Various forms are shown depending on the place where the holes are formed and the method of forming the holes. Therefore, when the formed polymer electrolyte is viewed, it may be felt that it is not enough to express the porosity. Can be referred to as a polymer electrolyte, and, when functionally represented, have a number of pores or voids to allow the polymer to retain an electrolyte that facilitates the transfer of ions (e.g., With such a structure, lithium ions can move in the electrolytic solution, and lithium ions can move in the matrix constituting the polymer.) It can also be referred to as a polymer electrolyte.

FIGS. 10 and 11 show a porous polymer membrane obtained by applying a solvent for dissolving a polymer on a glass substrate using a solvent extraction method and then immersing the glass substrate in an aqueous alcohol solution. FIG. 10 is an electron micrograph of the cross section of the film, and FIG. 11 is an electron micrograph of the film surface.

The polymer electrolyte may be one in which the polymer itself has ion conductivity, or one in which the polymer is immersed or swelled by being immersed in an electrolytic solution to have ion conductivity. Is also good.

Preferably, a polymer that becomes ionic conductive when wet or swells is used. As a material thereof, for example, polyvinylidene fluoride (P
VdF), polyethers such as polyvinyl chloride, polyacrylonitrile, polyethylene oxide, and polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, and polyvinyl acetate ,
Polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, or their inducers can be used alone or as a mixture.

Further, a polymer obtained by copolymerizing various monomers constituting the above polymer, for example, a vinylidene fluoride / hexafluoropropylene copolymer (P (V
dF / HFP)) can also be used. As the polymer provided inside the positive electrode or on the surface of the negative electrode, a polymer having flexibility capable of changing its shape following volume expansion and contraction of the active material due to charge and discharge is preferable.

As a method of performing the porosity treatment, a method of forming a through-hole by irradiating ultraviolet rays, a method of forming a through-hole with a sword or the like, a solvent extraction method, or the like can be used, and a method by a solvent extraction method is preferable.

In the solvent extraction method, a solvent a
A method for obtaining a porous polymer by using a solvent a for extraction to extract a solvent a from a polymer solution a ′, wherein the polymer solution a ′ in which the polymer is dissolved is insoluble in the polymer, and the solvent a By immersing in a solvent b which is compatible with the polymer solution a ′, the solvent a of the polymer solution a ′ is extracted, and a portion where the solvent a of the polymer is removed becomes a pore, and a porous polymer is formed. is there. Then, in this solvent extraction method, a through hole having a circular opening can be formed in the polymer.

As the solvent a for dissolving the polymer, for example, dimethylformamide, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and other carbonic esters, dimethyl ether, diethyl ether, ethyl methyl ether And ethers such as tetrahydrofuran, dimethylacetamide, 1-methyl-pyrrolidinone, n-methyl-2-pyrrolidone and mixtures thereof. As the solvent b for extracting the solvent a in the polymer solution, a solvent b that is compatible with the solvent a is selected according to the solvent a. For example, water, alcohol, acetone, or a mixed solution thereof can be used.

Next, the battery of the present invention is characterized in that a porous polymer electrolyte is provided inside the positive electrode. Here, the inside of the positive electrode means a gap existing in the outermost layer of the positive electrode, It shows a gap existing between the positive electrode active material particles. Then, the amount of the porous polymer electrolyte provided in the positive electrode is adjusted such that the polarization during charging occurs preferentially in the positive electrode as compared with the amount of the porous polymer electrolyte provided in the negative electrode.

For example, in the simplest case, no porous polymer is provided inside the negative electrode (in this case, however, as described later, the porous polymer may enter into the inside to some extent. Is also good.).

When a porous polymer is provided inside the negative electrode, the amount of the polymer entering the inside is adjusted by, for example, changing the concentration of the polymer solution, and the amount of the porous polymer electrolyte occupying the pore volume of the positive electrode is adjusted. Avo volume ratio
A> B when 1% and the volume ratio of the porous polymer electrolyte to the pore volume of the negative electrode are Bvol%.

In this case, if the volume ratio is B ≧ 0.
A value of 4 A is preferable because the amount of the electrolytic solution can be effectively reduced while suppressing a decrease in the high-rate discharge characteristics. The volume of the polymer electrolyte is a net volume, which is a volume calculated by dividing the weight of the polymer provided inside the electrode by the specific gravity of the polymer. Further, in the description of the claims of the present application, that the porous polymer electrolyte is provided inside the positive electrode means that the porous polymer is not positively formed on the positive electrode surface, which will be described later. In addition, there is a great effect on preventing the capacity from being reduced during high-rate discharge.

When the battery of the present invention is a lithium secondary battery
For example, as a positive electrode active material, for example, insertion and extraction of lithium
Can be used, for example, LiCo
O_Two, LiNiO_Two, LiMn_TwoO_Four, Li_TwoMn_TwoO_Four, M
nO_Two, FeO_Two, V_TwoO_Five, V ₆O₁₃, TiO_Two, TiS_Two
The composition formula Li_xMO_TwoOr Li_yM_TwoO_Four
(Where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2)
Oxides, oxides with tunnel-like holes, layers
Metal chalcogenides having a like structure can be used.

Also, LiNi _0.80 Co _0.20 O ₂ , LiNi _0.80 Co _0.17
An inorganic compound in which a part of the transition metal M is substituted with another element, such as Al _0.03 O _2, can also be used. Moreover,
For example, an organic compound such as a conductive polymer such as polyaniline can be used. In addition, regardless of an inorganic compound or an organic compound, the above-mentioned various active materials can be mixed and used.

In order to produce a positive electrode used in the battery of the present invention using these active materials, for example, the following method is used. Particles of the positive electrode active material of the type shown above,
A conductive agent such as acetylene black, a binder such as polyvinylidene fluoride, and a paste formed by kneading a dispersion medium such as NMP are applied on a metal foil such as aluminum,
The positive electrode body is manufactured by drying and applying this treatment to both surfaces of the metal foil.

Next, the electrode body is immersed in a polymer solution obtained by dissolving a polymer selected from the above-mentioned materials in a solvent a, and the polymer solution is carried inside the electrode body. When the electrode body is immersed in the polymer solution, the polymer solution penetrates into the voids inside the electrode. At this time, other methods for penetrating the polymer solution into the electrode include a vacuum impregnation method and a screen printing method. Alternatively, a method in which a polymer solution is applied to the electrode surface by a doctor blade method or the like, and the polymer solution is permeated into the electrode by osmotic pressure may be used.

Next, the excess polymer solution carried on the electrode surface is removed by passing the electrode through a roller or the like, and then immersed in the above-mentioned solvent b which is a solvent for extracting the solvent a for dissolving the polymer. The pores existing between the active material particles in the outermost layer of the electrode and the active material particles inside the electrode are occupied by the porous polymer electrolyte.

According to such a method, the polymer may remain on the surface of the active material particles in the outermost layer, and strictly speaking, it cannot be said that the porous polymer is also formed on the surface of the positive electrode. Can obtain a positive electrode having no porous polymer formed on the surface. Even if the porous polymer remains on the surface by such a method, this is not a problem if the amount is small. Further, after a porous polymer electrolyte is provided inside the electrode, the positive electrode is dried at a high temperature to remove water from the electrode.

Next, the positive electrode is pressed to have a predetermined thickness. The porosity of the positive electrode after pressing is preferably 20 to 40% excluding the volume occupied by the porous polymer electrolyte. It is preferable that the positive electrode be subjected to a press treatment after the porous polymer electrolyte is provided inside the electrode, and from this, it is better that the porous polymer electrolyte does not exist on the surface before pressing. This is because if a large amount of the porous polymer electrolyte remains on the surface, it becomes non-porous due to the pressing and blocks the ion passage on the electrode surface. Further, the battery of the present invention is characterized in that it has a negative electrode provided with a porous polymer electrolyte integrated on its surface, and such a negative electrode is produced, for example, as follows.

When the battery of the present invention is a lithium secondary battery, the negative electrode active material may be, for example, Al, Si, Pb,
Alloy of lithium with Sn, Zn, Cd, etc., LiFe ₂ O ₃
Transition metal composite oxides such as transition metal oxides such as WO _2, MoO _2, coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, graphitizable carbon such as pyrolytic vapor grown carbon fiber Heat-treated products of non-graphitizable carbon, such as fired products of phenolic resin, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, and fired furfuryl alcohol resin, natural graphite, artificial graphite,
Graphitized MCMB, graphitized mesophase pitch-based carbon fiber, a graphitic material such as graphite whisker, or a carbon material composed of a mixture thereof, lithium nitride, or metal lithium, or a mixture thereof,
Particularly, a carbon material is preferable.

Then, the particles of the negative electrode active material as described above,
A paste made by mixing a binder such as polyvinylidene fluoride and a dispersion medium such as NMP is applied on a metal foil such as copper and dried, and this process is performed on both sides of the metal foil to form the negative electrode body. To manufacture.

Next, the negative electrode body is pressed to a predetermined thickness. The porosity of the negative electrode after pressing is 20 to 40.
% Is preferable.

Next, a polymer solution is applied on the surface of the negative electrode. The coating thickness is adjusted by passing the negative electrode between a doctor blade and a roller having a constant width. Next, the negative electrode is immersed in the solvent b, which is an extraction solvent of the solvent a for dissolving the polymer, to form a porous polymer electrolyte on the negative electrode surface, and this treatment is performed on both surfaces of the negative electrode.

As a method for forming a porous polymer electrolyte on the negative electrode surface, the polymer solution is held on the negative electrode surface by a screen printing method or a vacuum impregnation method, and the polymer solution is held on the negative electrode surface by passing through a roller having a predetermined width. It is also possible to use another method such as a method of forming a porous polymer electrolyte on the surface of the negative electrode by setting the thickness of the polymer solution to a predetermined thickness and then immersing the polymer solution in the extraction solvent b.

[0037] As a method of the porous treatment, a polymer is dissolved in a solvent in which the polymer is dissolved or a mixture in which the polymer is dispersed in a solvent in which the polymer is not dissolved is sprayed on the surface of the negative electrode by spraying, and the solvent is evaporated to be porous. It is also possible to use a method, etc., in this case,
A porous polymer electrolyte membrane composed of fine particles is formed on the negative electrode surface. In addition, when the solution in which the polymer is dissolved is sprayed on the electrode, the solvent can be further extracted and the polymer can be subjected to a perforation treatment. When a spray is used, the solution is applied to the negative electrode surface by the spraying time. It is possible to adjust the thickness of the polymer solution.

The thickness of the porous polymer electrolyte formed on the surface of the negative electrode may be any thickness that can prevent short-circuiting when no porous polymer electrolyte membrane or separator is used between the positive and negative electrodes. Is preferably 35 μm or less.

By the above-described method, a porous polymer electrolyte integrated with the surface, which is different from that obtained when a separately prepared porous polymer electrolyte membrane is attached to the surface, is formed.

When the battery electrolyte is reduced, the charge / discharge characteristics are significantly deteriorated when a gap is present between the electrode and the separator. However, in the present invention, a porous polymer electrolyte is provided on the negative electrode surface, Since there is almost no gap between the battery and the separator, a battery having good charge / discharge characteristics can be obtained.

In the present invention, the negative electrode having the porous polymer electrolyte formed integrally on the surface thereof means that the positive electrode is preferentially polarized even if the porous polymer is carried inside the negative electrode. It means that there is only an amount that does not hinder, preferably it is good that the porous polymer is not positively supported inside the negative electrode, in this case, specifically, the volume of the porous polymer in the electrode However, it is good to be 2% or less, more preferably 1% or less of the pore volume of the negative electrode.

The pore volume of the electrode described in the present application is determined by the density of the electrode mixture calculated from the respective densities of the active material, the binder, and the conductive auxiliary agent and the outer shape (length, width, and thickness) of the electrode. It is calculated from the apparent volume based on the dimensions and its weight. Similarly, the pore volume of the separator is also calculated from the density, apparent volume, and weight of a material such as a polymer used for the separator.

A positive electrode used in the battery of the present invention;
The negative electrode can be prepared as described above, but when the battery of the present invention is to be further excellent in stability, in the battery of the present invention, the positive electrode or the negative electrode is
It is assumed to include active material particles having a polymer formed on the surface thereof in advance.

That is, even when an electrode is manufactured by the above-described method, the polymer is formed on the surface of the active material particles in the electrode, but the active material on which the polymer is formed in advance is formed. By using the material particles, the type and amount of the polymer formed on the surface can be freely adjusted.For example, by increasing the surface on which the polymer is formed, the direct contact between the active material and the electrolytic solution can be adjusted. The area is reduced and the battery is safer.

The type of the polymer formed on the surface may be selected variously depending on what kind of properties are imparted by the formation of the polymer. Examples of the polymer include a polymer, a porous polymer, a polymer electrolyte, and a porous polymer. Electrolytes,
These mixtures can be used, and as the form, it is particularly preferable to form a porous polymer, and more preferable that the polymer finally becomes a porous polymer electrolyte similar to the above.

This is because the porous polymer allows lithium ions to diffuse through the electrolyte solution in the pores, thereby providing a battery having excellent charge / discharge characteristics. This is because the use of a porous polymer electrolyte allows lithium ions to be diffused even in the polymer matrix, so that a battery having more excellent charge / discharge characteristics can be obtained.

The active material particles having a polymer formed on the surface means that the polymer is provided on at least a part of the surface of the active material particles. May be such that the polymer is present in the gaps. The amount of the polymer formed on the surface is sufficient if the ratio of the polymer to the weight of the active material particles on which the polymer is formed is 4 wt% or less.

Examples of the polymer formed on the surface include polyethers such as polyethylene oxide and polypropylene oxide, polyolefins such as polyethylene and polypropylene, polyvinylidene fluoride, polyacrylonitrile, polyvinylidene chloride, polymethyl methacrylate, and polymethyl acrylate. , Polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, and derivatives thereof can be used alone or in combination. Further, a polymer obtained by copolymerizing various monomers constituting the above polymer may be used.

Examples of a method for producing active material particles having a polymer formed on the surface in advance include the following.
A method in which the active material holding the polymer solution is directly dried to evaporate a solvent that dissolves the polymer, the active material holding the polymer solution a ′ is immersed in the solvent b, and the polymer is subjected to a porous treatment. Take out the active material with the polymer,
After drying, or a polymer solution containing the active material
There is a method in which the solvent b is added to a ′, the active material having the polymer subjected to the porous treatment is taken out, and then dried. The positive electrode and the negative electrode produced as described above are, for example, laminated or stacked and wound, or laminated with a porous polymer electrolyte membrane or separator interposed between the positive and negative electrodes, Alternatively, these are stacked and wound, placed in a battery case such as a cylindrical, square, or aluminum laminate bag, and an electrolyte for a lithium secondary battery is injected to obtain a battery.

In the case where the polymer has ion conductivity due to wetting or the like, the porous polymer electrolyte provided inside the electrode and on the electrode surface is wetted or swollen by the electrolyte when the electrolyte is injected. Then, the non-aqueous electrolyte secondary battery according to the present invention is completed.

When a porous polymer electrolyte membrane is used, such a membrane material may be a polymer material which becomes ionic conductive when wetted or swelled by the above-mentioned electrolytic solution, and is preferably used. , PVdF,
Polymers such as polyvinyl chloride, polyacrylonitrile, polyethylene oxide, and polypropylene oxide, or derivatives of these alone or as a mixture, and further, a polymer obtained by copolymerizing various monomers constituting the above polymer An electrolyte such as P (VdF / HFP) can be used.

When a separator is used, for example, a polyolefin microporous membrane such as a polypropylene microporous membrane or a polyethylene microporous membrane can be used.

Incidentally, the porous polymer electrolyte membrane and the separator may be used simultaneously. (Here, the “separator” is, for example, an insulating film such as polypropylene or polyethylene provided with a large number of micropores or a nonwoven fabric, which is a so-called ordinary separator. The major difference from the porous polymer electrolyte membrane is that the insulating film portion has no ionic conductivity.) As the electrolytic solution, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ -Butyrolactone, sulfolane, dimethylsulfoxide, acetonitrile, dimethylformamide, dimethylacetamide,
Polar solvents such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, and methyl acetate;
Alternatively, a mixture thereof can be used.

The salt contained in the electrolytic solution may be L
_{iPF 6, LiBF 4, LiAsF 6} , LiClO 4, Li
SCN, LiI, LiCF ₃ SO ₃ , LiCl, LiB
r, a lithium salt such as LiCF ₃ CO ₂ , or a mixture thereof can be used.

The amount of the electrolyte injected is the positive electrode, the negative electrode, and the separator (excluding when no separator is used).
Of the total pore volume (excluding the porous polymer electrolyte component)
It is preferably 20% or less and 10% or more, and at least the amount that can follow the expansion and contraction of the electrode volume in accordance with the electrode material is good. Preferably, it is based on the pore volume of the positive electrode and the separator. It is preferable to inject an amount calculated as 30 to 100%.

[0056]

EXAMPLES The present invention will be further described below with reference to examples. As [unipolar test positive electrode active material, LiNi _0.86 Co _0.14 0
Using No. ₂ , a positive electrode was produced as follows.

First, LiNi _0.86 Co _{0.140 2} particles 4
8.7 wt%, acetylene black 2.7 wt%, PV
A mixture of 3.3 wt% of DF and 45.3 wt% of NMP was applied to both surfaces of an aluminum foil, dried at 90 ° C. to evaporate NMP, and a positive electrode body was prepared. The porosity of the positive electrode body was 68%.

Next, a polymer solution in which 8% by weight of P (VdF / HFP) was dissolved in NMP was prepared, and the electrode body was immersed in the polymer solution to carry the polymer solution on the electrode body. Then, after removing the polymer solution excessively adhering to the electrode surface through a roller, the electrode body is immersed in a 0.001M phosphoric acid aqueous solution (which has an advantage that corrosion of aluminum can be prevented) to extract NMP. Was.
The electrode was taken out, dried at 130 ° C., and then pressed. The thickness of the positive electrode after pressing was 170 μm. The porosity of the electrode excluding the porous polymer electrolyte is 3
It was 0%. The total weight of the active material and the conductive additive filled per unit area was 21 mg / cm ² .

The porosity of the electrode depends on the active material, the binder,
It is calculated from the mixture density of the electrode calculated from the respective densities of the conductive assistants, the apparent volume calculated from the outer dimensions (length, width, thickness) of the electrode, and the weight of the electrode. The same applies to the following.

Next, graphite was used as a negative electrode active material, and a negative electrode was produced as follows. A mixture of 81 wt% of graphite, 9 wt% of PVdF, and 10 wt% of NMP is applied to both sides of a copper foil having a thickness of 14 μm.
Dry at 0 ° C. to evaporate the NMP to prepare a negative electrode body,
Next, a polymer solution in which 8 wt% of P (VdF / HFP) was dissolved in NMP was prepared, and the electrode body was immersed in the polymer solution to carry the polymer solution on the electrode body. Then, after removing the polymer solution excessively attached to the electrode surface through a roller, the electrode body is immersed in a 0.001 M phosphoric acid aqueous solution and
The extraction of MP was performed.

The electrode was taken out, dried at 130 ° C., and then pressed. The thickness of the negative electrode after pressing is 1
It was 95 μm. The porosity of the negative electrode was 35%. The weight of the active material filled per unit area of the negative electrode is 13 mg.
/ Cm ² .

The positive electrode and the negative electrode prepared as described above were immersed in a polymer solution in which 20% by weight of P (VdF / HFP) was dissolved in NMP, and the polymer solution was carried on the electrode surface. Since the viscosity of the polymer solution was high, the polymer solution hardly entered the inside of the electrode. Next, the thickness of the polymer solution carried on the electrode surface was set to 40 μm by passing the negative electrode holding the polymer solution while adjusting the gap between the rollers to a predetermined size. Further, these electrodes were immersed in ion-exchanged water to extract NMP, to form a porous polymer electrolyte layer on the surface of each electrode, and vacuum-dried at 120 ° C. to remove residual moisture. As a result, the thickness of the porous polymer electrolyte layer formed on the electrode surface was 10 μm.

The porous surface produced as described above
For the positive electrode and the negative electrode on which the conductive polymer electrolyte layer was formed,
Use lithium metal for the counter electrode and the reference
Of carbonate and diethyl carbonate (volume 1:
1) 1M LiClO as solvent _FourUsing dissolved electrolyte
A monopolar test was performed using a glass beaker cell.

As a result, it was found that a large difference was caused between the positive electrode and the negative electrode in the change of the discharge capacity per unit weight when the discharge current density was changed. That is, in the case of the negative electrode, as shown in FIG. 1 and FIG. 2, the degree of decrease in the discharge capacity when the discharge current density is increased depends on the negative electrode in which both the inside and the surface of the negative electrode do not support the porous polymer electrolyte. Did not change compared to.

On the other hand, as shown in FIGS. 3 and 4, in the case of the positive electrode, the discharge capacity when the discharge current density was increased was larger than that of the positive electrode in which neither the inside nor the surface carried the porous polymer electrolyte. It was found that the degree of the decrease was significantly large.

In the case where the porous polymer electrolyte layer is not formed on the electrode surface, such a phenomenon does not occur. In the case of the positive electrode, the porous polymer electrolyte layer is formed on the surface, so that the high-rate discharge is performed. It is considered that the characteristics deteriorate.

From these facts, it was found that when a porous polymer electrolyte layer is formed on the electrode surface, it is better to form it on the negative electrode surface.

FIG. 1 shows the relationship between the discharge current density and the discharge capacity of a negative electrode having no porous polymer electrolyte layer on the surface, and FIG. 2 shows the negative electrode having a porous polymer electrolyte layer on the surface. FIG. 3 is a diagram showing the relationship between the discharge current density and the discharge capacity of the positive electrode having no porous polymer electrolyte layer on the surface, and FIG. FIG. 5 is a diagram showing a relationship between a discharge current density and a discharge capacity of a positive electrode carrying a conductive polymer electrolyte. The unit of the current is m as shown in the figure.
A / cm ² .

Example 1 The following battery was manufactured using LiCoO ₂ as the positive electrode active material and graphite as the negative electrode active material.

The positive electrode was manufactured as follows. First, Li
CoO ₂ 48.7 wt%, acetylene black 2.7 wt
%, 3.3 wt% of PVdF, and 45.3 wt% of NMP are mixed to obtain a width of 20 mm, a length of 480 mm, and a thickness of 20 mm.
It was applied on both sides of a μm aluminum foil, dried at 90 ° C., and NMP was evaporated to prepare a positive electrode body. The porosity of the positive electrode body was 70%.

Next, a polymer solution in which 16% by weight of P (VdF / HFP) was dissolved in NMP was prepared, and the polymer solution was filled in the positive electrode holes by vacuum impregnation. After removing excess polymer solution adhering to the electrode surface through a roller, the positive electrode was immersed in ion-exchanged water to extract NMP. The electrode was taken out, dried at 130 ° C., and then pressed. The thickness of the positive electrode after pressing was 210 μm.

When the obtained positive electrode was observed with an electron microscope, a structure was observed in which a large number of active material particles were incorporated into a film having a three-dimensional network, and a filament was stretched in the pores. The thread was found to be the above polymer by DSC analysis. Electron micrographs are shown in FIGS. FIG. 5 is a cross section before pressing, FIG. 6 is a surface before pressing,
FIG. 7 is a cross-section after pressing. The porosity of the electrode excluding the porous polymer electrolyte was 30%. The total weight of the active material and the conductive additive filled per unit area is 29 mg /
cm ² .

Next, the production of the negative electrode will be described. Graphite 81wt%, PVdF9wt%, NMP10w
A mixture of t% was applied to both sides of a copper foil having a thickness of 14 μm, dried at 90 ° C. to evaporate NMP, and thereby a negative electrode body was prepared. Next, the electrode was flat-pressed. The thickness of the negative electrode after pressing was 160 μm. The porosity of the negative electrode was 20%. The weight of the active material filled per unit area of the negative electrode is 1
It was 3 mg / cm ² .

Next, the negative electrode is immersed in a polymer solution in which 20 wt% of P (VdF / HFP) is dissolved in NMP, and the polymer solution is supported on the surface of the negative electrode. Next, the negative electrode holding the polymer solution was passed through a roller, and the thickness of the polymer solution supported on the negative electrode surface was set to 80 μm.

Next, the negative electrode was immersed in ion-exchanged water to extract NMP, thereby forming a porous polymer electrolyte on the negative electrode surface.

Next, the negative electrode having a porous polymer electrolyte formed on its surface was vacuum-dried at 120 ° C. to remove residual moisture. The thickness of the porous polymer electrolyte formed on the negative electrode surface was 25 μm. The shape of the porous polymer layer formed on the negative electrode surface was similar to that shown in FIGS.

The positive electrode and the negative electrode completed through the above-described steps are superposed and wound to form a wound electrode plate group.
The cylindrical battery was assembled by inserting it into a stainless case having a height of 47.0 mm and a height of 47.0 mm. Thereafter, a mixed (volume 1: 1) electrolytic solution of ethylene carbonate containing 1M LiPF ₆ and diethyl carbonate was added, and finally an aging treatment was performed at 60 ° C. for 48 hours to obtain a battery (X) having a nominal capacity of 800 mAh according to the present invention. ) Was prepared.

[Comparative Example 1] Next, as a comparative example, a battery was prepared in which the porous polymer electrolyte was not provided inside the positive electrode, the porous polymer electrolyte was provided inside the negative electrode, and the porous polymer electrolyte was provided integrally on the negative electrode surface. did.

The positive electrode was manufactured as follows. LiCoO ₂ 4
8.7 wt%, acetylene black 2.7 wt%, PV
A mixture of 3.3 wt% of DF and 45.3 wt% of NMP was applied to both sides of an aluminum foil having a width of 20 mm, a length of 480 mm and a thickness of 20 μm, dried at 90 ° C., and dried at 90 ° C.
Was evaporated to prepare a positive electrode body. Then, it was pressed. The thickness of the positive electrode after pressing was 210 μm. The porosity of the electrode was 30%. The total weight of the active material and the conductive auxiliary filled per unit area was 29 mg / cm ² .

Next, the production of the negative electrode will be described. Graphite 81wt%, PVdF9wt%, NMP10w
A mixture of t% was applied to both sides of a copper foil having a thickness of 14 μm, dried at 90 ° C. to evaporate NMP, and thereby a negative electrode body was prepared. The porosity of the negative electrode body was 70%.

Next, a polymer solution in which 16% by weight of P (VdF / HFP) was dissolved in NMP was prepared, and the polymer solution was filled in the pores of the negative electrode by vacuum impregnation. After removing excess polymer solution adhering to the electrode surface through a roller, the negative electrode was immersed in a large amount of ion-exchanged water to extract NMP.
The electrode was taken out, dried at 130 ° C., and the electrode was flat-pressed. The thickness of the negative electrode after pressing was 160 μm. The porosity of the negative electrode excluding the porous polymer electrolyte was 20%. The weight of the active material filled per unit area of the negative electrode is 1
It was 3 mg / cm ² .

Next, the negative electrode is immersed in a polymer solution in which P (VdF / HFP) containing 20 wt% of NMP is dissolved, and the polymer solution is supported on the surface of the negative electrode. Next, the thickness of the polymer solution supported on the surface of the negative electrode was set to 80 μm by passing the negative electrode holding the polymer solution through a roller.

Next, the negative electrode was immersed in ion-exchanged water to extract NMP, thereby forming a porous polymer electrolyte on the negative electrode surface. Next, the negative electrode having a porous polymer electrolyte formed on its surface was vacuum-dried at 120 ° C. to remove residual moisture. The thickness of the porous polymer electrolyte formed on the negative electrode surface was 25 μm.

The positive electrode and the negative electrode completed through the above-described steps were stacked and wound to form a wound electrode plate group, and the subsequent steps were the same as in the above-described example to prepare a battery (Y).

Comparative Example 2 As a comparative example, a battery was prepared in which a porous polymer electrolyte was provided inside the positive electrode and the negative electrode, and a porous polymer electrolyte was integrally provided on the negative electrode surface. The positive electrode was manufactured through the same steps as in the above example,
The negative electrode was manufactured through the same steps as in the comparative example. These positive and negative electrodes are stacked and wound to form a wound electrode group,
The subsequent steps were the same as in the above example, and a battery (Z) was prepared.

[Investigation of Amount of Lithium Dendrite Precipitated on Negative Electrode Surface] Using the above-described battery, the following test was conducted to investigate the amount of lithium dendrite formed on the negative electrode surface. First, batteries (X), (Y) and (Z) are
The battery was charged with a current of mA to 4.2 V, followed by a constant voltage of 4.2 V for 2 hours. Next, it was completely discharged by discharging to 2.75 V at a current of 0.2 CmA. This was performed at room temperature for 20 cycles. The discharged batteries were disassembled, and the amount of lithium dendrite deposited on the surface of the negative electrode plate was examined.
Table 1 shows the results.

[0087]

[Table 1]

From this result, the amount of dendrite deposited on the negative electrode surface was the largest in the battery (Y). Battery (Y)
It is conceivable that the rate of polarization of the negative electrode during charging is higher than that of the positive electrode, so that the electrode reaches the electrolytic deposition potential of lithium, and the deposited metallic lithium becomes dendrites after several cycles. On the other hand, in the battery (Z), although the amount of electrolytic deposition of lithium was reduced during charging, the battery (X)
Further suppressed the electrolytic deposition of lithium as much as possible. By providing a porous polymer electrolyte only in the positive electrode inside the electrode, the potential control during charging is controlled by the positive electrode, and by forming the porous polymer electrolyte integrally on the negative electrode surface, even when high-rate charging is performed It is considered that since the diffusion distribution of lithium ions can be made uniform, electrolytic deposition was prevented.

Comparative Example 3 A battery of a comparative example was manufactured in the same manner as in the above example except that the porous polymer electrolyte was not used. The same positive electrode as the positive electrode body in the above example was pressed without immersion in the polymer solution to obtain an electrode having a thickness of 210 μm and a porosity of 30%. The total weight of the active material and the conductive additive filled per unit area is 29 mg
/ Cm ² . 8 and 9 show electron micrographs of the obtained positive electrode. FIG. 8 is a cross section before pressing, and FIG. 9 is a cross section after pressing.

The negative electrode is the same as the negative electrode before immersion in the polymer solution in the above-described embodiment, and the thickness of the negative electrode after pressing is 1
60 μm, the porosity is 20%, and the total weight of the active material and the conductive auxiliary filled per unit area of the negative electrode is 13 mg / cm ^2.
Met.

Next, a porous polymer electrolyte membrane (thickness: 25 μm, porosity: 40 μm) was placed between the positive electrode and the negative electrode thus produced.
%, Made of P (VdF / HFP)) to form a wound electrode group, and a comparative battery (F) having a nominal capacity of 800 mAh was prepared in the same manner as the battery of Example 1 described above.

[Relationship Between Injected Amount and Discharge Capacity] The difference in charge / discharge capacity depending on the injected amount was examined for the battery X of the example and the battery F of the comparative example. The positive electrode constituting the battery, the negative electrode, and the pore volume of the porous polymer electrolyte formed on the negative electrode surface for preventing short circuit between the positive and negative electrodes change with charging and discharging,
At the time of charging, the positive electrode and the negative electrode expand, so that the volume of pores is larger than at the time of assembly.

Therefore, the amount of liquid injected is the charged volume volume (the positive electrode volume, the negative electrode volume, the pore volume of the porous polymer electrolyte formed on the negative electrode surface, the positive electrode volume, (Total pore volume of the porous polymer membrane or porous polymer electrolyte membrane provided between the negative electrodes)
120%. Then, at room temperature, 1 CmA (800 mA
The battery was charged to 4.2 V with the current of A), subsequently charged for 2 hours at a constant voltage of 4.2 V, and then discharged to 2.75 V with a current of 1.5 CmA (1600 mA). FIG. 12 shows the change in the discharge capacity with respect to the change in the injection amount.

From these results, in the comparative example battery (F) (△ in the figure), when the injection amount was smaller than 120%, the discharge capacity at a high rate of 1.5 CmA sharply decreased. In the battery X (□ in the figure) according to the invention, the discharge capacity did not decrease so much even when the liquid amount was reduced. From this, it was found that the battery of the present invention was a battery in which the deterioration of the high-rate discharge performance was suppressed even if the electrolyte solution was reduced due to the use of the battery.

[Examples 2 and 3] LiNi _0.80 Co _0.17 Al _0.03 O ₂ previously provided with a polymer was used as a positive electrode active material, and graphite previously provided with a polymer was used as a negative electrode active material. An example for a battery is shown.

The positive electrode was manufactured as follows. A solution obtained by dissolving 1 wt% of P (VdF / HFP) in 99 wt% of N-methyl-2-pyrrolidone (NMP) was mixed with LiNi _0.80 Co _0.17 Al _0.03 O ₂ kept in a vacuum, and the excess was filtered by suction filtration. P (VdF / HF
The PMP NMP solution was removed. Thereafter, drying was performed at 120 ° C., and LiNi _0.80 Co _0.17 Al _0.03 O ₂ coated with P (VdF / HFP)
Was manufactured. Next, this LiNi _0.80 Co _0.17 Al _0.03 O ₂ 48.7
wt%, acetylene black 2.7 wt%, PVDF
A mixture of 3.3 wt% and 45.3 wt% of NMP is applied to both sides of an aluminum foil having a width of 20 mm, a length of 480 mm and a thickness of 20 μm, and dried at 90 ° C. to evaporate the NMP to prepare a positive electrode body. did. The porosity of the positive electrode body was 68%.

Next, the electrode body was immersed in a polymer solution in which 8 wt% of P (VdF / HFP) was dissolved in NMP, and the polymer solution was carried on the electrode body. After the polymer solution excessively attached to the electrode surface was completely removed through a roller, the electrode body was immersed in a 0.001 M phosphoric acid aqueous solution to extract NMP. The electrode was taken out, dried at 130 ° C., and then pressed. The thickness of the positive electrode after pressing was 170 μm. The porosity of the electrode excluding the porous polymer electrolyte was 30%. The total weight of the active material and the conductive additive filled per unit area was 21 mg / cm ² .

Next, the production of the negative electrode will be described. 1% by weight of P (VdF / HFP) is added to graphite kept in vacuum
The solution dissolved in 99 wt% of MP was mixed, and excess NMP solution of P (VdF / HFP) was removed by suction filtration. Thereafter, drying was performed at 100 ° C. to produce graphite coated with P (VdF / HFP). 81% by weight of this graphite,
A mixture of 9 wt% of PVdF and 10 wt% of NMP was applied to both surfaces of a copper foil having a thickness of 14 μm, dried at 90 ° C. to evaporate the NMP, thereby preparing a negative electrode body. Next, the electrode was flat-pressed. The thickness of the negative electrode after pressing was 195 μm. The porosity of the negative electrode was 35%. The total weight of the active material and the conductive auxiliary filled per unit area of the negative electrode is 13
mg / cm ² .

Next, the negative electrode is immersed in a polymer solution in which P (VdF / HFP) containing 20 wt% of NMP is dissolved, and the polymer solution is carried on the surface of the negative electrode. Next, by passing the negative electrode holding the polymer solution by changing the gap between the rollers, the thickness of the polymer solution to be supported on the negative electrode surface is 80,
It was 40 μm. Next, this negative electrode was immersed in ion-exchanged water to extract NMP, thereby forming a porous polymer electrolyte on the negative electrode surface.

Next, the negative electrode having a porous polymer electrolyte formed on its surface was vacuum dried at 120 ° C. to remove residual moisture. The thickness of the porous polymer electrolyte formed on the negative electrode surface was 25 and 10 μm, respectively. A 25 μm porous polymer electrolyte membrane was formed into a negative electrode (A), 10 μm
The film formed with the film m is referred to as a negative electrode (B).

The positive electrode and the negative electrode (A) completed through the above-described steps are superposed and wound to form a wound electrode plate group, which is inserted into a stainless case having a bottom diameter of 15 mm and a height of 47.0 mm to form a cylinder. The battery was assembled. Then, 1M 1M Li
A mixed (volume 1: 1) electrolyte solution of ethylene carbonate containing PF ₆ and diethyl carbonate was added.
Aging treatment at 48 ° C for 48 hours, nominal capacity 800m
Ah, a battery (C) of Example 2 of the present invention was prepared.

A groove is dug in the stainless steel case (a so-called non-return type safety valve). When the internal pressure of the battery rises, a crack is formed in the groove to release gas inside the battery, and the battery case is ruptured. I did not do it.

Next, a porous polymer electrolyte membrane (having a thickness of 15 μm) was placed between the positive electrode and the negative electrode (B) completed through the above steps.
m, porosity 40%, made of P (VdF / HFP)) to form a wound electrode plate group, which has a bottom diameter of 15 mm,
The cylindrical battery was assembled by inserting it into a stainless steel case having a height of 47.0 mm. Thereafter, a mixed electrolyte (volume 1: 1) of ethylene carbonate containing 1 M of 1 M LiPF ₆ and diethyl carbonate was added, and finally, aging treatment was performed at 60 ° C. for 48 hours to obtain a nominal capacity of 800 mAh according to the present invention. Battery No. 3 (D) was prepared.

In the above embodiment, a cylindrical battery case is used. However, the present invention is not limited to this, and a rectangular case, an aluminum laminate case, or the like may be used.

Example 4 A positive electrode was manufactured as follows. To LiNi _0.80 Co _0.17 Al _0.03 O ₂ kept in vacuum, P (VdF / HFP)
1% by weight of N-methyl-2-pyrrolidone (NMP) 99
The solution dissolved in wt% was mixed, and excess NMP solution of P (VdF / HFP) was removed by suction filtration. Then, it was further immersed in water, and the water was removed by suction filtration.
LiNi coated with porous P (VdF / HFP)
_0.80 Co _0.17 Al _0.03 O ₂ was produced.

Thereafter, the same processing as in the battery of Example 2 is performed to complete the positive electrode. Electron micrographs of the surface of the positive electrode active material particles are shown in FIGS. FIG. 13 is a partial photograph of the particle surface after polymer coating, and FIG. 14 is a particle surface photograph before polymer coating.

The negative electrode was manufactured as follows. 1% by weight of P (VdF / HFP) is added to graphite kept in vacuum by NMP
The solution dissolved in 99 wt% was mixed, and excess NMP solution of P (VdF / HFP) was removed by suction filtration. Then, it was further immersed in water, and the water was removed by suction filtration.
Drying was performed at 0 ° C. to produce graphite covered with a porous P (VdF / HFP) film. Thereafter, the negative electrode is completed in the same manner as in the battery of Example 2 except that the method of forming the porous polymer electrolyte membrane formed on the negative electrode surface is changed.

The formation of the porous polymer electrolyte on the negative electrode surface was performed as follows. First, NMP 20 wt% P (V
dF / HFP) is applied. Next, the mesh was removed from the negative electrode plate, and the negative electrode carrying the polymer solution on the electrode surface was immersed in water to extract NMP, thereby forming a porous polymer electrolyte on the negative electrode surface. This treatment was performed on both surfaces of the negative electrode. The thickness of the porous polymer electrolyte membrane formed on the negative electrode surface was 25 μm.

Using the above-mentioned positive electrode and the above-mentioned negative electrode, the same processing as in the above-mentioned Example 1 is performed, and a nominal capacity of 800 m
A battery A of Example 4 of the present invention was prepared.

Comparative Example 4 For comparison, a conventional battery was manufactured using LiNi _0.80 Co _0.17 Al _0.03 O ₂ as the positive electrode active material and graphite as the negative electrode active material. The positive electrode was manufactured as follows. First, LiNi _0.80 Co _0.17
Al _0.03 O ₂ 48.7 wt%, acetylene black 2.7 w
t%, 3.3 wt% of PVDF, and 45.3 wt% of NMP were mixed to obtain a mixture having a width of 20 mm, a length of 480 mm, and a thickness of 2 mm.
It was applied to both sides of a 0 μm aluminum foil, dried at 90 ° C., and NMP was evaporated to prepare a positive electrode body. The porosity of the positive electrode body was 68%.

Thereafter, a flat plate press was performed. The thickness of the positive electrode after pressing was 170 μm. The porosity of the electrode excluding the porous polymer electrolyte was 30%. The total weight of the active material and the conductive additive filled per unit area is 2
It was 1 mg / cm ² .

Next, the production of the negative electrode will be described. Graphite 81wt%, PVdF9wt%, NMP10w
A mixture of t% was applied to both surfaces of a copper foil having a thickness of 14 μm, dried at 90 ° C. to evaporate NMP, and a negative electrode body was prepared. Next, the electrode was flat-pressed. The thickness of the negative electrode after pressing was 195 μm. The porosity of the negative electrode was 35%. The total weight of the active material and the conductive additive filled per unit area of the negative electrode was 13 mg / cm ² .

Next, a porous polymer electrolyte membrane (thickness 25 μm, porosity 40 μm) was placed between the positive electrode and the negative electrode thus produced.
%, Made of P (VdF / HFP)) to form a wound electrode group, which was inserted into a stainless case having a bottom diameter of 15 mm and a height of 47.0 mm to assemble a cylindrical battery. Then, a mixture of ethylene carbonate containing 1 M of 1 M LiPF ₆ and diethyl carbonate (volume 1:
1) An electrolytic solution was added, and finally aging treatment was performed at 60 ° C. for 48 hours to prepare a battery (F) of a comparative example having a nominal capacity of 800 mAh.

[Charge / Discharge Characteristics] The difference in charge / discharge characteristics depending on the amount of liquid injected was investigated. The pore volume of the porous polymer electrolyte formed on the positive electrode, the negative electrode, and the negative electrode surface for preventing short circuit between the positive electrode and the negative electrode constituting the battery changes with charging and discharging. In the above embodiment, the positive electrode and the negative electrode expand at the time of charging, so that the pore volume is larger than at the time of assembly. Therefore, the amount of liquid injected is the pore volume in the charged state where the pore volume is the largest (positive pore volume, negative electrode pore volume, pore volume of the porous polymer electrolyte formed on the negative electrode surface, and between the positive electrode and the negative electrode). (Total pore volume of the porous polymer membrane or the porous polymer electrolyte membrane) provided in (1) above.

The battery (C) according to the present invention thus produced,
The batteries (D) and (E) and the battery (F) of the comparative example were charged at room temperature with a current of 1 CmA (800 mA) to 4.2 V, and then charged at a constant voltage of 4.2 V for 2 hours, and then 1.5 CmA.
(1600 mA) and discharged to 2.75V. FIG. 2 shows the change in the discharge capacity with respect to the change in the injection amount.

From these results, in the battery (F) of the comparative example, when the injection amount was smaller than 120%, the discharge capacity at a high rate of 1.5 CmA was sharply reduced. ), (D) and (E) showed large discharge capacities even when the liquid volume was reduced.

[Safety Test] The following safety tests were performed using the manufactured batteries. The batteries (C), (D), (E) and the conventionally known batteries (F) according to the invention are charged at room temperature to 4.3 V with a current of 1 CA, followed by a constant voltage of 4.3 V for 2 hours. 3m after charging
The nail was pierced by piercing the battery. Table 2 shows the results.

[0118]

[Table 2] From these results, the batteries (C), (D),
(E) was found to be a battery with higher safety than the battery (F) of the comparative example, and in the present invention, it was clear that the smaller the amount of the electrolyte, the better the safety of the battery. It became. In addition, as a result of performing the same test on the battery of Example 1, it was found that the batteries of Examples 2, 3, and 4 had a larger number of batteries in which the safety valve did not operate, and the polymer was formed on the surface in advance. It was found that the battery using the active material was more excellent in safety.

In the above embodiment, a part of the surface of the active material was covered with a porous polymer electrolyte, and a positive electrode having a porous polymer electrolyte inside the electrode and a part of the surface of the active material were covered with a porous polymer electrolyte. A battery was fabricated by coating with a polymer electrolyte and interposing a porous polymer electrolyte membrane between a negative electrode having a porous polymer electrolyte on the electrode surface, but instead of the porous polymer electrolyte membrane, Similar results were obtained when a separator made of polypropylene or the like was used.

In the present invention, the porous polymer electrolyte or the polymer electrolyte is provided on a part of the surface of the active material particles of both the positive electrode and the negative electrode, but only the active material surface of at least one of the positive electrode and the negative electrode is provided. However, excellent results were obtained as in the above example.

Further, the material provided on the surface of at least one of the active material particles of the positive electrode and the negative electrode may be simply a polymer, and the battery according to the present invention manufactured using an active material having polypropylene on at least one of the active material particles, The battery according to the present invention, which was manufactured using an active material provided with porous polypropylene on at least one of the active material particle surfaces, also showed excellent results as in the above-described example. The charge and discharge characteristics of the batteries (C), (D), and
Although the battery was slightly inferior to (E) and (B), it had better characteristics than the battery (F) of the comparative example.

[0122]

According to the present invention, in the battery using the porous polymer electrolyte, the rapid charging performance and the high rate discharging performance can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between discharge current density and discharge capacity of a negative electrode having no porous polymer electrolyte layer carried on its surface.

FIG. 2 is a view showing the relationship between discharge current density and discharge capacity of a negative electrode having a porous polymer electrolyte layer carried on its surface.

FIG. 3 is a diagram showing a relationship between a discharge current density and a discharge capacity of a positive electrode having no porous polymer electrolyte layer carried on its surface.

FIG. 4 is a view showing a relationship between a discharge current density and a discharge capacity of a positive electrode having a porous polymer electrolyte supported on a surface thereof.

FIG. 5 is a cross-sectional electron micrograph of the positive electrode of Example before pressing.

FIG. 6 is a surface electron micrograph of the positive electrode of Example before pressing.

FIG. 7 is a cross-sectional electron micrograph of the positive electrode of Example after being pressed.

FIG. 8 is a cross-sectional electron micrograph of a comparative positive electrode without using a porous polymer electrolyte before pressing.

FIG. 9 is a cross-sectional electron micrograph of a comparative positive electrode after pressing without using a porous polymer electrolyte.

FIG. 10 is an electron micrograph of a cross section of a porous polymer film.

FIG. 11 is an electron micrograph of the surface of a porous polymer film.

FIG. 12 is a diagram showing a change in discharge capacity with respect to a change in injection volume.

FIG. 13 is a partial electron micrograph of the particle surface after polymer coating.

FIG. 14 is a partial electron micrograph of the particle surface before polymer coating.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5H003 AA01 BB12 BB32 BC01 BC04 BC05 5H014 AA02 AA07 CC01 CC04 EE02 5H029 AJ02 AJ05 AK02 AK03 AK05 AL01 AL02 AL03 AL06 AL12 AL19 AM02 AM03 AM04 AM05 AM07 AM16 BJ02 BJ08 DJ09 DJ13 DJ16 EJ12 HJ12

Claims (2)

[Claims] 1. A battery comprising an electrode and a porous polymer electrolyte, wherein the positive electrode has a porous polymer electrolyte therein, and the negative electrode has an integral porous polymer electrolyte on its surface. Characteristic non-aqueous electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode or the negative electrode contains active material particles having a polymer formed on the surface thereof in advance.