JPH10284045A - Manufacture of porous polymer electrolyte and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of enhancing high rate discharge property of a battery at low temperature, safety, and the capacity by increasing the utilization factor of an active material by perforating a polymer by elongation to obtain a specified range of porosity, and wetting or swelling the polymer with an electrolyte. SOLUTION: Porosity is limited to 10-80%. A polymer preferably contains polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and a monomer constituting these polymers. A battery having a positive electrode retaining an electrolyte of 30-95 volume % of the pore volume, a negative electrode, and a porous polymer electrolyte is obtained. Since ions can be passed through not only an electrolyte on the pores but also the inside of the polymer electrolyte, high rate charge/discharge is made possible. Since tensile strength is increased and thickness of a film is made thin by elongation, the amount of an active material can be increased. Local pressure increase caused by vaporization of the electrolyte by heat is suppressed by gas in the vicinity of an electrode. By omitting a safety element of the battery, cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art A battery using a non-aqueous electrolytic solution and using an alkali metal for the negative electrode can be a high-voltage battery of 3 V or more. However, secondary batteries have the drawback that short-circuiting is likely to occur due to dendritic deposition of alkali metal during charging, and the life is short, and it is difficult to ensure safety due to high reactivity of alkali metal. It is. Therefore, for example, in a lithium battery, instead of metallic lithium, a carbon-based negative electrode such as graphite or carbon in which dendrites of metallic lithium are unlikely to be used is used, and lithium cobaltate or lithium nickelate is used for a positive electrode, so-called lithium. Ion batteries have been devised and used as high energy density batteries.
However, when the utilization rate of the carbon-based negative electrode increases and intercalation progresses, the electrolytic solution evaporates due to heat generated by a short circuit or the like, and when the internal pressure of the battery rapidly increases, lithium in the negative electrode and carbon Reacts with lithium to generate lithium carbide and generate heat. As a result, the internal pressure of the battery rapidly rises, and there is a problem in safety. Therefore, the utilization rate of the carbon-based negative electrode is currently limited to less than 60% (Li _X C ₆ , 0 ≦ x <0.6) in consideration of safety. There was a problem that it could not be obtained.

In a lithium battery and a lithium ion battery (hereinafter collectively referred to as a lithium battery), most of the amount of lithium ions involved in an electrode reaction in a charge / discharge reaction is based on lithium ions dissolved in an electrolyte. However, since the lithium ions released from the active material of the electrode move in the electrolytic solution and reach the counter electrode, the moving distance of the lithium ion is long. In addition, while the transport numbers of protons and hydroxide ions in an aqueous battery show a value close to 1, the transport numbers of lithium ions in an electrolyte in a lithium battery at room temperature are usually 0.5. As described below, the moving speed of ions in the electrolyte is governed by the concentration diffusion of ions, and the diffusion speed of ions is slow because the organic electrolyte has higher viscosity than the aqueous solution. Therefore, the lithium-based battery has a problem that the charge-discharge performance at a high rate is inferior to that of the aqueous-based battery.

[0004] In the lithium battery, a microporous membrane such as polyethylene or polypropylene is used as a separator. As a method for producing the microporous organic polymer film, a wet method and a stretching method are mainly used. In the wet method, a liquid obtained by dissolving an organic polymer in a liquid and spreading it in a sheet shape is immersed in a liquid tank to remove the liquid in which the organic polymer has been dissolved. The microporous organic polymer membrane having circular or elliptical holes is applied to a sealed nickel cadmium battery. The stretching method is a method for producing a microporous film in which a directional hole is formed in a film by stretching an organic polymer film, and is widely applied to secondary batteries. In addition, there is a method for producing a microporous organic polymer film by adding fine particles such as salt and starch into an organic polymer to form a sheet, and then dissolving and removing the fine particles in a liquid. There is also a method of manufacturing a microporous organic polymer film in which an organic polymer is dissolved in a liquid at a high temperature and cooled to solidify the organic polymer and then remove the liquid. In addition, a separator is provided with a battery safety mechanism by utilizing a shutdown effect in which pores are closed by melting of a microporous organic polymer film due to heat. With this mechanism, even when the battery generates heat and enters a dangerous state, it is possible to insulate between the positive electrode and the negative electrode, and further suppress the reaction between the positive electrode and the negative electrode.

[0005] Non-aqueous batteries, unlike lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and the like, which use an aqueous solution for the electrolyte, use a flammable organic electrolyte for the electrolyte, thus enabling safe use of the battery. Because of the safety problems, safety valves, protection circuits, PTC elements, etc.
It is necessary to provide various safety elements, and there is a problem that the cost is high.In addition, since the utilization rate of the active material is limited, the energy density of the battery is higher than expected from the theoretical capacity of the active material. Is also greatly reduced. Therefore, it has been attempted to improve the safety of the battery by using a solid polymer electrolyte having less chemical reactivity instead of the organic electrolyte. Also, application of solid polymer electrolytes has been attempted for the purpose of flexibility of battery shape, simplification of manufacturing process, reduction of manufacturing cost, and the like.

As the polymer electrolyte, many studies have been made on complexes of polyethers such as polyethylene oxide and polypropylene oxide with alkali metal salts. But,
Polyether is difficult to obtain high ionic conductivity while maintaining sufficient mechanical strength, and since the conductivity is greatly affected by temperature, sufficient conductivity cannot be obtained at room temperature. Attempts have been made to use a comb-type polymer having an ether in the side chain, a copolymer of a polyether chain and another monomer, a polysiloxane or polyphosphazene having a polyether in the side chain, a crosslinked product of a polyether, and the like.

[0007] In a polymer electrolyte in which a salt is dissolved, such as a polyether-based polymer electrolyte, both cations and anions move, and the cation transport number at room temperature is usually 0.5 or less. Therefore, -SO ^3- or -COO ^- by combining a polymer electrolyte having an anionic group such as, but attempts have been made to the transference number of the cation and 1, it is bound to anionic groups strongly cation Therefore, the ionic conductivity was very low, and it was very difficult to use it for batteries.

Further, it has been attempted to produce a gel polymer electrolyte by wetting or swelling the polymer with an electrolytic solution, and to apply the gel polymer electrolyte to a non-aqueous battery. Polymers used in the gel polymer electrolyte include polyacrylonitrile, polyvinyl sulfone, polyvinyl chloride, polyvinylidene fluoride, polyvinyl pyrrolidinone, and the like. Attempts have also been made to reduce the crystallinity of the polymer by using a copolymer of vinylidene fluoride and hexafluoropropylene, and to improve the conductivity by facilitating wetting or swelling with an electrolytic solution. Also,
Attempts have also been made to produce a polymer membrane by drying a latex such as nitrile rubber, styrene-butadiene rubber, polybutadiene, polyvinylpyrrolidone, etc., and wetting or swelling it with an electrolyte solution. In the production of a polymer electrolyte using this latex, two types of polymers are mixed, and a polymer phase that does not easily penetrate the electrolyte and maintains strong mechanical strength, and a polymer that easily permeates the electrolyte and exhibits high ionic conductivity A polymer membrane that provides mechanical strength and ionic conductivity by using a mixed system with a phase has been proposed.

Further, in order to enhance the mechanical strength of the polymer electrolyte membrane and improve the ease of handling, a solid electrolyte in which the polymer electrolyte is filled in the pores of the polyolefin microporous membrane, an ionic conductivity improvement and An organic polymer electrolyte containing an inorganic solid electrolyte powder for the purpose of increasing the cation transport number has also been reported.

As described above, various organic polymer separators and polymer electrolytes have been proposed. However, there is no functional membrane that essentially overcomes the problem that the ion diffusion rate is slow. The performance was not sufficient as compared with the aqueous battery.

[0011]

The problem of the organic electrolyte solution is that the conductivity of ions is extremely low as compared with that of an aqueous solution, and the diffusion rate thereof is low. There was a point.

A conventional nonaqueous electrolyte battery using an organic electrolyte solution uses polyethylene or polypropylene, which does not swell or wet with the electrolyte solution, as a separator. Therefore,
Since the separator does not absorb the electrolyte and spread the electrolyte uniformly throughout the electrode, the electrolyte does not spread evenly throughout the battery if the amount of electrolyte injected into the battery is small. However, sufficient battery performance was not obtained. Therefore, in order to obtain sufficient battery performance, it is necessary to inject a large amount of the electrolytic solution, and as a result, the electrolyte and the pores of the electrode and the separator and the gap between the electrode and the separator are all occupied by the electrolytic solution. Was. Therefore, when a safety test such as nail penetration is performed, there is no gas that acts as a cushion against local pressure rise near the electrode, and heat is generated at the internal short-circuit point, causing vaporization of the electrolyte near the electrode. The pressure suddenly increases locally, and the reaction that is the starting point of the exothermic chain reaction is likely to occur, and the safety is reduced. Therefore,
In order to improve the safety of the battery, it is necessary to limit the utilization rate of the active material, which limits the capacity of the battery, and also requires various safety elements to increase the cost. there were.

In a conventional non-aqueous electrolyte battery using a solid electrolyte, the diffusion rate of ions in the solid electrolyte is much lower than that of an organic electrolyte, so that the supply of lithium ions required for an electrode reaction is not sufficient. However, when charging and discharging at a high rate and charging and discharging at a low temperature are performed, sufficient battery performance cannot be obtained.

The present invention has been made in view of the above problems, and is a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery in which pores are formed in a polymer by stretching. By using the porous polymer electrolyte according to the present invention, the charge / discharge at a high rate is good even at a low temperature, and it is possible to manufacture a battery that is more safe than a conventional energy density battery, and the active material It is possible to increase the capacity of the battery by improving the utilization factor and to reduce the cost of the battery by omitting the safety element.

[0015]

The object of the present invention is achieved by the following invention.

A first aspect of the present invention is a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, wherein pores are formed in the polymer by stretching.

A second invention which is a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, wherein the polymer having holes formed by stretching is wetted or swelled with an electrolytic solution.

According to the first or second aspect of the present invention, there is provided a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, wherein the porosity of the polymer is made 10% to 80% by stretching. Third invention.

According to the first, second or third aspect of the present invention, the polymer which forms pores by stretching comprises, as its components, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and various monomers constituting the organic polymer. A fourth invention which is a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, comprising at least one of the copolymers contained therein.

The porous polymer according to the first, second, third or fourth invention is provided with a positive electrode, a negative electrode or a porous polymer electrolyte holding an electrolytic solution having a volume of 30% to 95% of the pore volume. A fifth invention, which is a non-aqueous electrolyte battery comprising an electrolyte.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional liquid electrolyte nonaqueous battery, a porous polymer membrane such as polypropylene or polyethylene is used as a separator. Is secured. In this case, the separator is an insulator in ionic conduction, and becomes an obstacle when charging and discharging at a high rate. Further, in a battery using a conventional polymer electrolyte having no pores as an electrolyte, the diffusion of ions in the electrolyte is further slowed down, so that there is a disadvantage that the charge / discharge performance is significantly reduced. In the non-aqueous electrolyte battery using the porous polymer electrolyte according to the present invention, ions can pass not only in the electrolyte solution in the pores but also in the polymer electrolyte, which is higher than that of a conventional liquid electrolyte non-aqueous battery. Charge and discharge at a high rate becomes possible. Further, in the non-aqueous electrolyte battery using the porous polymer electrolyte according to the present invention, a passage through which ions are rapidly diffused by the electrolyte solution in the pores is secured, so that a conventional high-pressure battery having no communication hole is provided. The charge / discharge at a higher rate becomes better than the molecular electrolyte battery.

In the present invention, a porous polymer electrolyte is produced by subjecting a polymer membrane to a porous treatment by stretching. Microporous polymers produced by the stretching method have through holes instead of random holes, so the ion movement path is shortened when ions pass through the pores of the polymer, and ions can be efficiently collected. You can move. Therefore, by using a porous polymer electrolyte perforated by a stretching method instead of a separator, by a wet method, a method using a foaming agent, a method of bonding powder or a method of depositing a solid in a polymer, A battery excellent in charge / discharge characteristics at a high rate and at a low temperature as compared with the case where a polymer electrolyte having random holes is used can be obtained. In addition, since the porous polymer membrane according to the present invention has a high tensile strength in order to perform a stretching treatment, it is possible to manufacture a battery using a thinner polymer membrane than a polymer membrane obtained by another method. it can. Therefore, the non-aqueous electrolyte battery using the porous polymer electrolyte according to the present invention,
By filling the positive and negative electrode active materials by that much, a high energy density battery is obtained. In the present invention, when a polymer is swelled or wetted with an electrolytic solution to form an electrolyte,
Even when the amount of liquid injected into the battery is small, since the polymer absorbs the electrolyte, the electrolyte is evenly distributed over the entire electrode. Therefore, by allowing the battery to retain a smaller amount of electrolyte than the amount of electrolyte sufficient to occupy all of the pores, such as the pores of the porous polymer electrolyte and the electrodes, the porous polymer Even in the case where a gas portion is left in the hole of the electrolyte or in the hole of the electrode, sufficient battery performance can be obtained by spreading the electrolyte over the entire electrode. Therefore, when a safety test such as nail penetration is performed, a gas that serves as a cushion against local pressure rise is present near the electrode, and the heat generated at the internal short-circuit location evaporates the electrolyte near the electrode. Even in this case, the local increase in pressure is greatly reduced, and the reaction that is the starting point of the exothermic chain reaction is unlikely to occur, and the safety is improved. Therefore, it is possible to improve the utilization rate of the active material, which has been limited in order to improve the safety of the battery, so that the battery can have a high capacity, and various safety elements can be omitted. Costs can be reduced because it becomes possible.

In the present invention, a porous polymer electrolyte is produced by subjecting a polymer film to a porous treatment by stretching. The microporous polymer produced by the stretching method is formed with through holes instead of random holes, so the gas movement path becomes shorter when the gas passes through the holes of the polymer, and the gas is efficiently evacuated. You can move. Therefore, when a battery safety test such as nail penetration is performed, since the local pressure rise is quickly mitigated, even if the electrolytic solution in the vicinity is vaporized due to heat generation at the internal short-circuit location, The local pressure rise is greatly alleviated, and the reaction that is the starting point of the exothermic chain reaction is less likely to occur, thereby improving the safety. Therefore, it is possible to improve the utilization rate of the active material, which has been limited in order to improve the safety of the battery, so that the battery can have a high capacity, and various safety elements can be omitted. Costs can be reduced because it becomes possible.

[0024]

【Example】

(Embodiment 1) Hereinafter, the present invention will be described using preferred embodiments.

The fabrication of the positive electrode will be described. First, 70% by weight of lithium cobaltate, 6% by weight of acetylene black
%, Polyvinylidene fluoride (PVDF) 9Wt
%, N-methyl-2-pyrrolidone (NMP) 15 Wt%
Was applied on a stainless sheet having a width of 20 mm, a length of 480 mm, and a thickness of 20 μm, and dried at 150 ° C. to evaporate NMP. After the above operation was performed on both sides of the stainless steel sheet, it was pressed to obtain a positive electrode. The thickness of the positive electrode after pressing was 170 μm, and the weight of the active material, the conductive agent, and the binder filled per unit area was 23 μg / cm ² .

The negative electrode was manufactured as follows. Graphite 81Wt%, PVDF9Wt%, NMP10Wt%
Was applied onto a nickel sheet having a thickness of 14 μm, and dried at 150 ° C. to evaporate NMP. After performing the above operation on both sides of the nickel sheet,
Pressing was performed to obtain a negative electrode. The thickness of the negative electrode after pressing is 1
It was 90 μm.

Next, a porous PVDF membrane was produced by a stretching method as follows. PVD with a molecular weight of about 60,000
After the molten film of F is solidified by cooling in a casting drum, it is longitudinally stretched at a speed difference between a slow drive roll and a fast drive roll while preheating to a stretching temperature through a heating roll, and then heated again to a stretching temperature. A biaxially stretched PVDF film having a through hole by a tenter method was manufactured by expanding the width by a clip sandwiching both ends and stretching the film laterally. When manufacturing a PVDF film by the stretching method,
By changing the stretching tension and temperature, the porosity can be 10%, 21%, 30%, 38%, 49%, 60%,
Eight types of PVDF with a thickness of 30 μm of 72% and 80%
A film was made.

The thus prepared PVDF porous polymer membrane, the positive electrode and the negative electrode were stacked and wound to a height of 47.0 m.
m, a width of 22.2 mm and a thickness of 6.4 mm were inserted into a stainless steel case to assemble a prismatic battery. Inside the battery, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 and 1 mo
2.5 g of an electrolytic solution to which 1 / l of LiPF ₆ was added was added by vacuum injection, and the PVDF porous polymer was swollen with the electrolytic solution to obtain a porous polymer electrolyte. Thus, the battery (A) of Example 1 using the present invention and having a nominal capacity of about 400 mAh was manufactured. Battery (A) has a porosity of 10
%, 21%, 30%, 38%, 49%, 60%, 72%
And 80% of each PVDF membrane were used to produce eight types. In the battery according to the present invention, by using PVDF having different molecular weights, the wettability or swelling of the electrolytic solution can be controlled.

As Comparative Example 1, the nominal capacity was the same as that of Example 1 except that a polypropylene membrane having a thickness of 30 μm and a porosity was used instead of the porous polymer electrolyte membrane. A known battery B having a capacity of about 400 mAh was manufactured. Battery B was manufactured with five types of polypropylene membranes having porosity of 10%, 35%, 53%, 66% and 80%, respectively.

Comparative Example 2 has the same structure as that of Example 1 except that a PVDF membrane formed by a dry method is used instead of the PVDF porous polymer membrane.
A conventionally known battery C of about mAh was manufactured. The polymer film formed by the dry method has few or no communication holes, but does not mean that it does not exist at all. The method for producing the dry PVDF film is as follows. 12 g of polyvinylidene fluoride (PVDF) powder having a molecular weight of 60,000 was dissolved in 88 g of NMP. The solution was spread thinly on polyethylene-coated silica paper and dried at 85 ° C. for 1 hour to obtain a 30 μm-thick PVDF by a dry method.
A membrane was made. No pores were observed on the surface by SEM.

Using these batteries A, B and C, -2
At 0 ° C., the battery was charged to 4.1 V with a current of 1 CA, subsequently charged for 2 hours at a constant voltage of 4.1 V, and then discharged to 2.5 V at a current of 1 CA.

FIG. 1 is a diagram showing the relationship between the discharge capacity of these batteries and the porosity of the polymer electrolyte or separator of the used lithium ion battery. From the figure, it can be seen that the battery A using the present invention has a porosity of the polymer electrolyte of 10% to 80%.
It can be understood that the battery B shows a better discharge capacity than the conventionally known battery B using a polypropylene membrane instead of a polymer electrolyte.

Further, in the polymer electrolyte and the separator, when the porosity is increased, there is a problem that an internal short-circuit and a fall of the active material occur. Therefore, the battery A using the present invention, in which the porosity of the polymer electrolyte is 10%,
The significance of the present invention can be understood from the fact that the separator exhibited a discharge capacity superior to that of the battery B having a porosity of 80%.

Example 2 A porous polymer film having a porosity of 35% was produced by a stretching method using polyvinyl chloride (PVC) having a molecular weight of about 44,000 instead of PVDF, and an electrolyte was injected. A battery D using the present invention of Example 2 was manufactured in the same manner as the battery A using the present invention of Example 1 except that the amount was changed. Battery D was manufactured in five types with different electrolyte injection volumes, and the battery symbols were D-1, D-2,
D-3, D-4 and D-5.

As a comparative example, the present invention is different from the present invention except that a porous polypropylene membrane having a porosity of 35% was used in place of the porous PVDF membrane as a short-circuit prevention membrane between the positive electrode and the negative electrode. A known battery E having a nominal capacity of about 400 mAh was manufactured in the same manner as the battery D using. The amount of electrolyte injected into the battery was set to the minimum necessary for exhibiting sufficient battery performance.

Using the battery D using the present invention and the conventionally known battery E, at 25 ° C., 1 CA
The battery was charged to a constant voltage of 4.1 V for 2 hours, and then discharged to 2.5 V at a current of 2 CA. As a result of these tests, the battery D using the present invention and the conventionally known battery E all show the same discharge capacity regardless of the amount of liquid injected into the battery D, and there is a difference in the battery performance. Did not.

After the above-described charge / discharge test, the battery D using the present invention and the conventionally known battery E were disassembled, and the positive electrode,
As a result of measuring the amount of electrolyte retained by the negative electrode and the porous PVC film or separator between the positive and negative electrodes, in each battery, the positive electrode, the negative electrode, and the porous PVC film or separator occupy the pore volume. The volume ratios of the electrolytes were all the same within the error range. Table 1 shows the results.

[0038]

[Table 1] In addition, the following safety comparison test was performed using the battery D using the present invention and the conventionally known battery E. Using these batteries, the battery was charged to 4.5 V at a current of 1 CA at room temperature, followed by charging at a constant voltage of 4.5 V to 2 V.
After charging for an hour, a nail having a diameter of 3 mm was pierced by penetrating the battery. Table 1 shows the results.

From these results, it was found that the battery D using the present invention
Can be said to be a battery having better safety than the conventionally known battery E. In the battery using the present invention, the positive electrode, the negative electrode, and the porous PVC between the positive and negative electrodes
It can be said that the smaller the amount of the electrolyte held by the membrane, the better the safety of the battery.

In the above embodiment, polyvinylidene fluoride or polyvinyl chloride is used as the polymer of the polymer electrolyte. In addition to this, polyacrylonitrile and a copolymer of vinylidene fluoride and hexafluoropropylene may be used. The same battery fabrication, charge / discharge test and safety test were carried out using the same, but all showed the same results as those obtained when polyvinylidene fluoride or polyvinyl chloride was used.

In the above embodiment, polyvinylidene fluoride or polyvinyl chloride is used as the polymer of the polymer electrolyte. However, the present invention is not limited to this, and polyethers such as polyethylene oxide and polypropylene oxide, and polyethers are used. Acrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol,
Polymethacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, or a derivative thereof may be used alone or as a mixture. In addition, a copolymer having various monomers constituting the organic polymer in the structure may be used.

In the battery of the above embodiment, a PVDF membrane or a PVC membrane made porous by a biaxial stretching method using a tenter method was used as a porous polymer electrolyte. Is not limited thereto, and may be uniaxial stretching or a stretching method using a tube method.

In the battery of the above embodiment, a porous polymer electrolyte was used as a short-circuit preventing film between the positive electrode and the negative electrode. It may be held in at least one of the holes or on the surface.

In the battery of the above embodiment, a mixed solution of EC and DEC is used as the non-aqueous electrolyte. However, the present invention is not limited to this. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate Carbonate, γ-butyrolactone,
Sulfolane, dimethyl sulfoxide, acetonitrile,
Dimethylformamide, dimethylacetamide, 1,2
A polar solvent such as -dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

In the above embodiment, LiPF ₆ is used as a salt to be contained in the non-aqueous electrolyte.
In addition, LiBF ₄ , LiAsF ₆ , LiClO ₄ ,
LiSCN, LiI, LiCF ₃ SO ₃ , LiCl, L
A lithium salt such as iBr or LiCF ₃ CO ₂ or a mixture thereof may be used.

Further, in the above embodiment, LiC was used as the compound capable of inserting and extracting an alkali metal as a positive electrode material.
Although oO ₂ was used, it is not limited to this.
In addition, as the inorganic compound, the composition formula Li _X MO
₂ or LiyM ₂ O ₄ where M is a transition metal and 0 ≦ x
.Ltoreq.1, 0.ltoreq.y.ltoreq.2), a composite oxide, an oxide having tunnel-like vacancies, and a metal chalcogenide having a layered structure can be used. As a specific example, LiC
oO ₂ , LiNiO ₂ . LiMn ₂ O ₄ , Li ₂ Mn ₂
O ₄ , MnO ₂ , FeO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , Ti
O ₂ , TiS _{2 and the} like can be mentioned. Examples of the organic compound include a conductive organic polymer such as polyaniline. Furthermore, regardless of inorganic compounds or organic compounds,
The above various active materials may be used in combination.

Further, in the above embodiment, graphite is used as a compound as a negative electrode material. In addition, alloys of lithium with Al, Si, Pb, Sn, Zn, Cd, etc., LiFe ₂ O _3, etc. Transition metal composite oxide,
Transition metal oxides such as MoO ₂ and tin oxide, carbonaceous materials such as graphite and carbon, lithium nitride such as Li ₅ (Li ₃ N), or metallic lithium foil, or a mixture thereof may be used.

[0048]

According to the conventional liquid electrolyte non-aqueous battery, a porous polymer membrane such as polypropylene or polyethylene is used as a separator, and an ion conduction path is secured by holding the electrolyte in the pores. doing. In this case, the separator is an insulator in ionic conduction, and becomes an obstacle when charging and discharging at a high rate.
Further, in a battery using a conventional polymer electrolyte having no pores as an electrolyte, the diffusion of ions in the electrolyte is further slowed down, so that there is a disadvantage that the charge / discharge performance is significantly reduced. In the porous polymer electrolyte according to the present invention, ions can pass not only in the electrolyte solution in the pores but also in the polymer electrolyte, and charge and discharge at a higher rate than conventional liquid electrolyte nonaqueous batteries can be performed. It becomes possible. In addition, in the porous polymer electrolyte according to the present invention, a passage through which ions are rapidly diffused by the electrolyte solution in the pores is secured, so that the porous polymer electrolyte has a higher efficiency than the conventional polymer electrolyte battery having no communication holes. Charging / discharging becomes good.

In the present invention, a porous polymer electrolyte is produced by subjecting a polymer film to a porous treatment by stretching. Microporous polymers produced by the stretching method have through holes instead of random holes, so the ion movement path is shortened when ions pass through the pores of the polymer, and ions can be efficiently collected. You can move. Therefore, by using a porous polymer electrolyte perforated by a stretching method instead of a separator, by a wet method, a method using a foaming agent, a method of bonding powder or a method of depositing a solid in a polymer, A battery excellent in charge / discharge characteristics at a high rate and at a low temperature as compared with the case where a polymer electrolyte having random holes is used can be obtained. In addition, since the porous polymer film according to the present invention has a high tensile strength in order to perform a stretching treatment, it is possible to manufacture a battery using a thinner polymer film as compared with a polymer film obtained by another method. A high energy density battery can be obtained by filling a large amount of the positive and negative electrode active materials.

In the present invention, when the polymer is swelled or wetted with the electrolyte to form an electrolyte, the polymer absorbs the electrolyte even when the amount of liquid injected into the battery is small.
The electrolyte spreads evenly over the entire electrode. Therefore, by allowing the battery to retain a smaller amount of electrolyte than the amount of electrolyte sufficient to occupy all of the pores, such as the pores of the porous polymer electrolyte and the electrodes, the porous polymer Even in the case where a gas portion is left in the hole of the electrolyte or in the hole of the electrode, sufficient battery performance can be obtained by spreading the electrolyte over the entire electrode. Therefore, when a safety test such as nail penetration is performed, a gas that serves as a cushion against local pressure rise is present near the electrode, and the heat generated at the internal short-circuit location evaporates the electrolyte near the electrode. Even in this case, the local increase in pressure is greatly reduced, and the reaction that is the starting point of the exothermic chain reaction is unlikely to occur, and the safety is improved. Therefore, it is possible to improve the utilization rate of the active material, which has been limited in order to improve the safety of the battery, so that the battery can have a high capacity, and various safety elements can be omitted. Costs can be reduced because it becomes possible.

In the present invention, a porous polymer electrolyte is produced by subjecting a polymer membrane to a porous treatment by stretching the polymer membrane. The microporous polymer produced by the stretching method is formed with through holes instead of random holes, so the gas movement path becomes shorter when the gas passes through the holes of the polymer, and the gas is efficiently evacuated. You can move. Therefore, when a safety test such as nail penetration is performed, since the local pressure rise is quickly mitigated, even if the electrolytic solution in the vicinity is vaporized due to heat generation at the internal short-circuit location, local Pressure rise is greatly reduced, and the reaction that is the starting point of the exothermic chain reaction is less likely to occur, and the safety is improved. Therefore, it is possible to improve the utilization rate of the active material, which has been limited in order to improve the safety of the battery, so that the battery can have a high capacity, and various safety elements can be omitted. Costs can be reduced because it becomes possible.

[Brief description of the drawings]

FIG. 1 is a view showing a relationship between porosity and discharge capacity in a battery A using the present invention in Example 1 and comparative batteries B and C.

Claims (5)

[Claims] 1. A method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, wherein pores are formed in the polymer by stretching. 2. A method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery, wherein a polymer having holes formed by stretching is wetted or swelled with an electrolytic solution. 3. The method according to claim 1, wherein the porosity of the polymer is adjusted to 10% or more and 80% or less by stretching.
The method for producing a porous polymer electrolyte for a nonaqueous electrolyte battery according to the above. 4. A polymer having pores formed by stretching as at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and a copolymer having various monomers constituting the organic polymer in its structure. 3. The method according to claim 1, further comprising:
Or a method for producing a porous polymer electrolyte for a non-aqueous electrolyte battery according to item 3. 5. The method according to claim 1, further comprising a positive electrode, a negative electrode or a porous polymer electrolyte holding an electrolytic solution having a volume of 30% to 95% of the pore volume. A non-aqueous electrolyte battery comprising a porous polymer electrolyte.