JPH1167191A - Method for producing electrode for non-aqueous electrolyte battery and method for producing non-aqueous electrolyte battery - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Even when an electrode having a porous polymer is manufactured by immersing an electrode holding a polymer solution in water using aluminum as a current collector, even if the electrode is made of water, Corrosion is prevented, and deterioration in battery performance due to deterioration in current collection performance of the current collector is suppressed. SOLUTION: A method for producing an electrode for a non-aqueous electrolyte battery, comprising treating an electrode using aluminum as a current collector and holding a mixed solution containing a polymer with water containing phosphorus or a phosphorus compound. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an electrode for a non-aqueous electrolyte battery and a method for manufacturing 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.

A non-aqueous battery uses a flammable organic electrolyte for the electrolyte, unlike lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc., which use an aqueous solution for the electrolyte, thereby 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 due to the problem of the battery safety, the energy density of the battery is reduced. There is a problem that the value is much smaller than expected from the theoretical capacity. 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.

[0005] 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 ^-
It has also been attempted to synthesize a polymer electrolyte having an anion group such as described above and make the cation transport number one.
Since the cation is strongly bound to the anionic group, the ionic conductivity is very low, and it has been very difficult to use it for a battery.

Further, it has been attempted to produce a gel-like polymer electrolyte by wetting or swelling the polymer with an electrolytic solution, and to apply it 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 to 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.

In order to improve the safety of a non-aqueous electrolytic cell, it is important to reduce the amount of free electrolyte near the positive and negative electrode active materials. Therefore, applying a solid electrolyte instead of a free electrolyte solution in the holes of the positive and negative electrodes is extremely effective in improving the safety.

However, in a non-aqueous electrolyte battery such as a lithium battery and a lithium ion battery, most of the amount of lithium ions involved in the electrode reaction in the charge / discharge reaction is not lithium ions dissolved in the electrolyte, but instead of lithium ions. Since the lithium ions released from the active material move in the electrolyte and reach the counter electrode, the movement distance of the lithium ions is long. Moreover, while the transport numbers of protons and hydroxide ions in the aqueous battery show values close to 1, the transport numbers of lithium ions in the electrolyte of the nonaqueous electrolyte battery at room temperature are usually 0.5 or less. And the movement speed of the ions in the electrolyte is governed by the concentration diffusion of the ions. Therefore, when a solid electrolyte is used instead of the electrolyte in the pores of the electrode, the diffusion rate of ions in the electrolyte becomes very slow, so that the charge / discharge characteristics at a high rate are reduced, and practical use is not possible. There was a problem that battery performance could not be obtained.

In order to overcome such problems, the solid electrolyte in the electrode hole is made porous, and the high-rate charge / discharge characteristics of the battery are improved by rapid ion diffusion in the free electrolyte solution in the hole. Have been tried. In this case,
Since the amount of free electrolyte solution can be reduced by the amount of the polymer filled in the pores of the electrode, the battery is safer than a conventional battery that does not use a solid electrolyte. Sufficient battery performance is obtained by diffusion.

The solid electrolyte filled in the electrode hole changes its shape following the volume expansion and contraction of the active material due to charge and discharge.
Since it is necessary to have elasticity, a gel-like polymer obtained by swelling a polymer with an electrolytic solution is desirable. The most suitable method for producing a porous polymer is a solvent extraction method capable of forming uniform spherical pores. The solvent extraction method is to extract the solvent of the polymer solution by immersing the polymer solution in a solvent that is insoluble and compatible with the polymer, and removes the solvent from the solvent. Are porous and solidify the polymer. In this solvent extraction method, the solvent in which the polymer solution is immersed is water which is strong in polarity, compatible with many solvents, insoluble in many polymers, and inexpensive. In a non-aqueous electrolyte battery, it is not desirable that water is mixed into the battery, but the electrode is immersed in water and dried sufficiently, and after inserting the electrode into the battery case, the polymer is swollen by pouring the electrolyte. By making the porous polymer electrolyte, it is possible to manufacture a battery having a small water content and no problem in performance. However, in non-aqueous electrolyte batteries, the potential of the positive electrode is often very noble,
As the current collector, aluminum having excellent corrosion resistance to a noble potential is used. However, since aluminum is corroded by water, when the positive electrode is immersed in water, the electron conductivity of the aluminum surface is significantly reduced. Therefore, there is a problem that the battery performance is reduced due to the reduction in the current collection performance, and aluminum cannot be used substantially as a current collector. In particular, when the positive electrode active material is a transition metal composite oxide such as lithium cobalt oxide or lithium nickel oxide, alkali components such as lithium hydroxide and lithium carbonate used as a lithium source for the synthesis are included as residues. In addition, when the positive electrode is immersed in water, there is a problem that the water in the vicinity of the electrode becomes alkaline due to the elution of the alkali component, and the corrosion of aluminum, which is an amphoteric metal, is promoted.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and uses aluminum as a current collector and immerses an electrode holding a polymer solution in water to form a porous polymer. Even when an electrode provided is provided, the corrosion of aluminum due to water is prevented, and a decrease in battery performance due to a decrease in current collection performance of the current collector is suppressed.

[0013]

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

A method for manufacturing an electrode for a non-aqueous electrolyte battery, comprising treating an electrode using aluminum as a current collector and holding a mixed solution containing a polymer with water containing phosphorus or a phosphorus compound. A certain first invention.

A second invention according to the first invention, which is a method for producing an electrode for a non-aqueous electrolyte battery, wherein the concentration of phosphorus or a phosphorus compound is 1 × 10 ⁻⁷ to 1 mol / l.

A third invention according to the first or second invention, which is a method for producing an electrode for a non-aqueous electrolyte battery, wherein the phosphorus or phosphorus compound is phosphoric acid.

A fourth invention which is a method for manufacturing a non-aqueous electrolyte battery, comprising an electrode manufactured by using the invention of claim 1, 2 or 3.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION When a porous polymer is filled into a hole of an electrode using aluminum as a current collector by a solvent extraction method, when the electrode is immersed in water, the aluminum is corroded and electron conductivity is reduced. There is a problem that the battery performance is remarkably reduced, and the battery performance is lowered due to the lowered current collection performance. Therefore, aluminum could not be used substantially as a current collector. In the present invention, an electrode for a non-aqueous electrolyte battery is manufactured by treating an electrode using aluminum as a current collector and holding a mixed solution containing a polymer with water containing phosphorus or a phosphorus compound. According to the present invention,
Experiments have confirmed that even when an electrode using aluminum as the current collector is immersed in water, it is possible to significantly prevent a decrease in current collection performance due to corrosion of aluminum by water. It is presumed that the reason why the corrosion of aluminum is suppressed by using phosphorus or a phosphorus compound is that phosphorus or the phosphorus compound reacts with aluminum to form a phosphorus compound film on the surface. Therefore, by using the present invention, by immersing the electrode in water in the solvent extraction method, even if an electrode with a polymer having a spherical and uniform pores is manufactured, the current collector aluminum Thus, it is possible to suppress a decrease in current collection performance due to corrosion of the battery and obtain sufficient battery performance. Inexpensive water can be used as a solvent for immersing the electrode in the solvent extraction method, so that the manufacturing cost of the electrode can be reduced as compared with the case where another solvent is used.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.

Example 1 A non-aqueous electrolyte battery was manufactured according to the following procedure.

First, a method for manufacturing the positive electrode will be described. Lithium cobaltate 70Wt%, acetylene black 6W
t%, polyvinylidene fluoride (PVDF) 9Wt
%, N-methylpyrrolidone (NMP) 15 Wt% is mixed with a width of 100 mm, a length of 480 mm, and a thickness of 20 μm.
m on an aluminum foil, dried at 150 ° C.
The MP was evaporated. This operation was performed on both sides of the aluminum foil to produce a positive electrode having an active material layer on both sides. On both sides of this positive electrode, 4 Wt% of PVDF was
After applying a polymer paste dissolved in Wt% and leaving it to stand for 5 minutes and allowing it to permeate into the pores of the active material layer by osmotic pressure,
By passing between the rollers, it does not penetrate into the electrode,
The polymer paste attached to the electrode was removed. The positive electrode was immersed in a 1 × 10 ⁻³ mol / l phosphoric acid aqueous solution for 5 minutes, and the NMP in which the PVDF was dissolved was replaced with water to extract the PV in the electrode hole.
The DF was subjected to a communicating porous treatment and solidified. 100 electrodes
After drying at 30 ° C. for 30 minutes to remove water, pressing was performed to reduce the thickness of the electrode from 280 μm to 175 μm, and then cut into a size of 19 mm in width and 480 mm in length.

Next, a method for manufacturing the negative electrode will be described. Graphite 81Wt%, PVDF9Wt%, NMP10
Wt% mixed active material paste 80 mm wide and 5 mm long
It was applied on a copper foil having a thickness of 00 mm and a thickness of 14 μm, and dried at 150 ° C. to evaporate NMP. This operation was performed on both surfaces of the copper foil to produce a negative electrode having an active material layer on both surfaces. After that, press to make the electrode thickness 300μ
After thinning from m to 190 μm, it was cut into a size of 20 mm in width and 500 mm in length.

After winding these positive / negative electrode plates and a polyethylene separator having a thickness of 30 μm and a width of 22 mm, it was inserted into a stainless case having a height of 47.0 mm, a width of 22.2 mm and a thickness of 6.4 mm. Further, an electrolyte obtained by adding 1 mol / l of LiPF ₆ to a mixed solution of ethylene carbonate and dimethyl carbonate at a volume ratio of 1: 1 was injected to produce a battery (A) according to the present invention having a nominal capacity of 400 mAh. The battery case was provided with a non-return type safety valve.

A comparative battery (B) was manufactured in the same manner as the battery (A) except that the positive electrode was immersed in purified water containing no phosphoric acid.

Using the batteries (A) and (B), the following charge / discharge test was performed. The battery was charged to 4.1 V with a current of 400 mA, subsequently charged for 2 hours at a constant voltage of 4.1 V, left for 10 minutes, and then discharged to 2.75 V at a constant current of 800 mA. These discharge characteristics are shown in FIG.
Shown in From FIG. 1, it can be seen that the battery (A) according to the present invention shows much higher high-rate discharge characteristics than the comparative battery (B).

From these results, it can be seen that in the battery (A) according to the present invention, aluminum as the positive electrode current collector is less corroded and the current collecting performance of the positive electrode is superior to that of the comparative battery (B). it can. This is presumed to be because when the positive electrode was immersed in a phosphoric acid aqueous solution in the production of the battery (A), phosphoric acid formed a coating of a phosphorus compound on the surface of aluminum, so that aluminum corrosion by water was suppressed. Is done.

Example 2 In order to examine the effects of the present invention in detail, the concentration of the phosphoric acid aqueous solution was changed in the production of the positive electrode plate in Example 1, and the positive electrode (C) according to the present invention was changed.
Was manufactured and its surface resistance was measured. A positive electrode (D) of Comparative Example was produced in the same manner as the positive electrode (C) except that the positive electrode coated with the polymer paste was immersed in purified water containing no phosphoric acid. MCP-TESTER LORESTA-FP manufactured by Mitsubishi Yuka Co., Ltd. was used for measuring the surface resistance. In this surface measurement, two probes with a diameter of 2 mm are pressed against one surface of the electrode at a constant pressure at an interval of 8 mm.
The measurement was performed by measuring the resistance between the two probes. Since the current collector of the electrode has an overwhelmingly higher electron conductivity than the active material layer, in this method, the resistance from the electrode surface to the current collector is substantially measured. An increase in resistance can be detected. The surface resistance was measured before and after applying the polymer paste in which PVDF was dissolved in NMP to the positive electrode, and after applying the polymer paste to the positive electrode, immersing in water and drying at 100 ° C. for 30 minutes. In both cases. The difference between the values is shown in FIG. 2 as the amount of increase in the surface resistance. From this result, it can be said that the positive electrode (C) according to the present invention is an electrode excellent in current collecting performance, with significantly less corrosion of aluminum as the current collector than the positive electrode (D) of the comparative example. This is presumably because, when the positive electrode was immersed in the aqueous phosphoric acid solution, phosphoric acid formed a coating of a phosphorus compound on the surface of the aluminum, so that aluminum corrosion by water was suppressed.

From these results, it has been clarified that even at an extremely low phosphoric acid concentration of 10 ⁻⁷ mol / l, a tremendous effect can be obtained in preventing corrosion of aluminum. Although the effect can be obtained even when the phosphoric acid is strong, it is useless to make the concentration more than necessary in consideration of economy, so 1 mol / l or less is sufficient.

[Example 3] Surface resistance was measured in the same manner as in Example 2 for the positive electrode according to the present invention prepared in Example 1 using various phosphorus compounds instead of phosphoric acid. Table 1 shows the results.

[0030]

[Table 1] From Table 1, it can be seen that the same effect as in the case of phosphoric acid was produced also when a phosphorus compound other than phosphoric acid or phosphorus was used.

In the above embodiment, polyvinylidene fluoride is used as the polymer to be filled in the pores of the electrode. Alternatively, the following polymers may be used alone or in combination. Good: Polyethers such as polyethylene oxide and polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene imine, polybutadiene , Polystyrene, polyisoprene and derivatives thereof. Further, a polymer obtained by copolymerizing various monomers constituting the polymer may be used.

In the battery (A) according to the present invention, a mixed solution of ethylene carbonate and dimethyl carbonate is used as the non-aqueous electrolyte, but other solvents may be used: ethylene carbonate, propylene Carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
Polar solvents such as 2-methyltetrahydrofuran, dioxolan, methyl acetate and the like, and mixtures thereof.

In the battery (A) according to the present invention, LiPF ₆ is used as a lithium salt to be contained in the non-aqueous electrolyte. In addition, LiBF ₄ , LiAsF ₆ ,
LiClO ₄ , LiSCN, LiI, LiCF ₃ S
Lithium salts such as O ₃ , LiCl, LiBr, and LiCF ₃ CO ₂ and mixtures thereof may be used.

Further, in the above embodiment, LiCoO 2 was used as the compound capable of inserting and extracting lithium as the cathode material.
₂ was used, but is not limited to this. In addition, as the inorganic compound, the composition formula Li _x MO ₂ ,
Or Li _y M ₂ O ₄ (where M is a transition metal, 0 ≦ x
.Ltoreq.1, 0.ltoreq.y.ltoreq.2), a composite oxide, an oxide having tunnel-like holes, and a metal chalcogenide having a layered structure can be used. As a specific example, LiCo
O 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 , TiO
₂ , TiS _{2 and the} like. Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, in the fabrication of the battery of the first embodiment, graphite was used as a compound as a negative electrode material, but in addition, Al, Si, Pb, Sn, Zn, C
alloys of lithium with d and the like, transition metal composite oxides such as LiFe ₂ O ₃ , transition metal oxides such as MoO ₂ , carbonaceous materials such as graphite and carbon, lithium nitrides such as Li ₅ (Li ₃ N), An oxide of tin or silicon, or lithium metal foil, or a mixture thereof may be used.

[0036]

As described above, in the present invention,
An electrode for a non-aqueous electrolyte battery is manufactured by treating an electrode using aluminum as a current collector and holding a mixed solution containing a polymer with water containing phosphorus or a phosphorus compound.
Experiments have shown that the present invention can significantly prevent a decrease in current collection performance due to corrosion of aluminum by water even when an electrode using aluminum as the current collector is immersed in water. Therefore, by using the present invention, by immersing the electrode in water in the solvent extraction method, even if an electrode with a polymer having a spherical and uniform pores is manufactured, the current collector aluminum The deterioration of the current collection performance due to the corrosion of the battery can be significantly suppressed, and sufficient battery performance can be obtained. Inexpensive water can be used as a solvent for immersing the electrode in the solvent extraction method, so that the manufacturing cost of the electrode can be reduced as compared with the case where another solvent is used. Therefore, according to the present invention, a safe and high-performance non-aqueous electrolyte battery can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing high rate discharge characteristics of a battery (A) according to the present invention and a comparative battery (B) in Example 1.

FIG. 2 is a view showing the relationship between the phosphoric acid concentration and the surface resistance of the positive electrode (C) according to the present invention in Example 2 and the positive electrode (D) of the comparative example.

Claims (4)

[Claims] 1. A method for producing an electrode for a non-aqueous electrolyte battery, wherein an electrode containing aluminum as a current collector and holding a mixed solution containing a polymer is treated with water containing phosphorus or a phosphorus compound. Law. 2. The concentration of phosphorus or a phosphorus compound is 1 × 10 ^−7.
The method for producing an electrode for a non-aqueous electrolyte battery according to claim 1, wherein the amount is from 1 to 1 mol / l. 3. The method for producing an electrode for a non-aqueous electrolyte battery according to claim 1, wherein the phosphorus or the phosphorus compound is phosphoric acid. 4. A method for producing a non-aqueous electrolyte battery, comprising an electrode according to the method according to claim 1, 2 or 3.