JP2002358964A - Manufacturing method of lithium nickelate having porous polymer on particle surface and non-aqueous electrolyte secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of lithium nickelate having a porous polymer on the particle surface that is used for a positive electrode of a non-aqueous secondary battery, which is superior in discharge performance and cycle performance at a high rate. SOLUTION: In the manufacturing method of lithium nickelate having a porous polymer on the particle surface, a process for mixing lithium nickelate particles and a polymer solution, a process for dipping the mixture of lithium nickelate particles and the polymer solution in the alcohol water solution having an alcohol concentration of 30 wt.% or more, and a process for drying the mixture so obtained are employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing lithium nickel oxide and a nonaqueous electrolyte secondary battery using the same.

[0002]

2. Description of the Related Art Due to the rapid development of portable electronic devices, there is an urgent need for higher performance batteries for power supplies. One of the batteries is a metal lithium secondary battery. Lithium exhibits the lowest potential among metals and has a low specific gravity, so that the battery has a high energy density. However, the repetition of charge and discharge causes precipitation of lithium dendrites, so that a sufficient cycle life was not obtained. In addition, there is a problem in safety because the dentite causes an internal short circuit.

Therefore, a lithium ion secondary battery in which graphite, carbon, or the like is used as a negative electrode active material has been devised. As the positive electrode active material, lithium cobalt oxide, lithium nickel oxide, or the like is used. Since these positive electrode active materials have low electron conductivity, they are applied to a current collector such as aluminum together with a conductive agent such as acetylene black. Therefore, the battery is an active material,
It is composed of various materials such as a conductive agent, a binder, a current collector, and a separator. However, there is a problem that the distribution of the electrolyte becomes non-uniform because the wettability of these materials with the electrolyte is different. As a result, the current distribution becomes non-uniform, and particularly the cycle performance thereof is lowered.

Therefore, it has been considered to make the distribution of the electrolytic solution uniform by allowing a porous polymer electrolyte to be present in the holes of the positive and negative electrode plates (JP-A-9-259923).
The characteristic of the porous polymer electrolyte is that by impregnating the porous polymer with the organic electrolyte, the polymer portion is wetted or swelled with the electrolyte, so that not only in the electrolyte present in the pores, That is, lithium ions can move quickly in the polymer. Conventionally, an electrode plate provided with a porous polymer has been manufactured as follows. The active material, the conductive agent, the binder, and the organic solvent are mixed to form a paste, and the paste is applied to a current collector and dried to produce an electrode plate having a mixture layer. . Thereafter, the electrode plate is immersed in the polymer solution to impregnate the mixture layer with the solution. However, since the solution hardly penetrates into the layer, the distribution of the polymer in the electrode plate becomes uneven. Therefore, it was difficult to make the distribution of the electrolyte solution uniform.

In order to solve this problem, a technique has been devised in which a porous polymer electrolyte is previously applied to the surface of the active material particles (EP 10774498). In this method, a porous polymer is attached to the surface of the active material particles or the pores thereof in advance, and then the active material powder, a conductive agent, a binder, and an organic solvent are mixed to form a paste, The electrode plate is manufactured by applying and drying the paste on a current collector. Therefore, the distribution of the polymer in the electrode plate can be made uniform.

In the electrode plate to which this technique is applied, the distribution of the electrolyte in the vicinity of the active material particles can be remarkably uniformed, so that the cycle performance can be expected to be improved. Heretofore, a solvent extraction method has been mainly used for the production method.

A method for producing an active material powder in which a porous polymer is applied to the particle surface will be described below. First, the polymer solution is attached to the surface of the active material particles by dispersing the active material powder in the polymer solution. Next, the active material provided with the polymer solution is immersed in an extraction solvent to disperse the active material powder. Finally, the powder is dried. At this time, since the solvent of the polymer solution is removed by the extraction solvent, the portion becomes a hole. As the extraction solvent,
Those that are incompatible with the polymer and that are compatible with the solvent of the polymer solution have been used.

Hitherto, water has been mainly used as an extraction solvent because it is easily available, easily purified, and inexpensive. EP 1077498 states that it is possible to use lithium nickelate as the positive electrode active material and alcohol as the extraction solvent. However, the content was insufficient.

[0009]

In recent years, since higher energy densities of lithium ion secondary batteries have been further required, lithium nickel oxide is expected as a positive electrode active material thereof. This is because the active material has a high capacity and is inexpensive. However, when a lithium nickelate powder having a porous polymer on the particle surface is manufactured by a conventional method using water as an extraction solvent, a non-aqueous electrolyte secondary battery using the same as a positive electrode at a high rate. There was a problem that the discharge performance deteriorated.

In JP-A-2000-149926, Li
Immersing an electrode plate using Ni _1-x M _x O ₂ (M represents an element selected from the group consisting of metal, fluorine, phosphorus and boron, and satisfying 0 ≦ x ≦ 0.5) in alcohol; A technique has been disclosed that suppresses a decrease in the discharge capacity. In that case, when the positive plates of LiNi _1-x M _x O ₂ and other lithium nickelate are immersed in water,
There is no description that the reduction of the discharge performance at the high rate is suppressed. However, there has been a problem that the discharge performance of lithium nickel oxide powder at a high rate is reduced.

Further, in a method in which a lithium nickelate positive electrode plate is manufactured and then a porous polymer is applied to the holes of the electrode plate, sufficient cycle performance cannot be obtained even when alcohol is used as an extraction solvent. Was. In addition, the lithium cobalt oxide powder did not cause a problem such as a decrease in discharge performance at a high rate.

According to the present invention, when a lithium nickelate powder having a porous polymer on the particle surface is manufactured by immersing the powder in water, the discharge performance of a positive electrode plate using the powder at a high rate is improved. In order to solve the above-described problem of lowering, an object of the present invention is to provide a method for producing lithium nickelate having a porous polymer on the particle surface for significantly improving the discharge performance of a nonaqueous electrolyte secondary battery. I do.

[0013]

According to the first aspect of the present invention,
The present invention relates to a method for producing lithium nickelate having a porous polymer on the particle surface, comprising the steps of mixing lithium nickelate particles and a polymer solution, and mixing the mixture of the lithium nickelate particles and the polymer solution with an alcohol concentration of 3
A step of immersing in a 0 wt% or more aqueous alcohol solution;
And drying the obtained mixture.

According to the first aspect of the present invention, the high-rate discharge performance and cycle performance of a nonaqueous electrolyte secondary battery using lithium nickelate having a porous polymer on the particle surface for its positive electrode plate are remarkably improved. .

According to a second aspect of the present invention, in the method of the first aspect, in the step of mixing the lithium nickelate particles and the polymer solution, the lithium nickelate powder is dispersed in the polymer solution. .

According to the second aspect of the present invention, since the porous surface of the particles of the lithium nickel oxide powder can be uniformly provided with the porous polymer, the discharge performance of the nonaqueous electrolyte secondary battery using the same as the positive electrode at a high rate can be improved. A third aspect of the present invention, in which the cycle performance is greatly improved, comprises a step of immersing a mixture of lithium nickelate particles and a polymer solution in an aqueous alcohol solution in the production method according to the first or second aspect. It is characterized in that lithium nickelate is dispersed in an aqueous alcohol solution.

According to the third aspect of the present invention, lithium nickelate particles having a porous polymer on the surface are less likely to agglomerate. Cycle performance is greatly improved.

The invention according to claim 4 is the invention according to claim 1, 2, or 3.
The above-described lithium nickelate having a porous polymer on the particle surface is a powder having an average particle size of 0.1 μm or more and 50 μm or less.

According to the fourth aspect of the present invention, since the lithium nickelate provided with the porous polymer on the particle surface is uniformly applied to the current collector, the height of the nonaqueous electrolyte secondary battery using the electrode plate is increased. The discharge performance at the rate and the cycle performance are remarkably improved. The invention of claim 5 is the invention of claim 1, 2, 3, or 4.
In the above-mentioned production method, the alcohol is ethyl alcohol.

According to the fifth aspect of the present invention, since the handling of ethyl alcohol is easy, the production cost can be reduced, and the discharge performance and cycle of a non-aqueous electrolyte secondary battery using this as a positive electrode at a high rate. The performance is good.

According to a sixth aspect of the present invention, there is provided the first and second aspects.
A lithium nickelate provided with a porous polymer on the particle surface according to 3, 4 or 5 is used for a positive electrode plate for a non-aqueous electrolyte secondary battery.

According to the sixth aspect of the invention, the high-rate discharge performance and cycle performance of the positive electrode plate for a non-aqueous electrolyte secondary battery are significantly improved.

According to a seventh aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery using the positive electrode plate according to the sixth aspect. According to the invention of claim 7, the discharge performance and the cycle performance at a high rate of the nonaqueous electrolyte secondary battery are significantly improved.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing lithium nickelate having a porous polymer on the particle surface according to the present invention comprises the steps of mixing lithium nickelate particles with a polymer solution (mixing step); It is characterized by passing through a step of immersing a mixture of particles and a polymer solution in an aqueous alcohol solution having an alcohol concentration of 30 wt% or more (extraction step) and a step of drying the obtained mixture (drying step).

As the mixing step, 1) a method of immersing lithium nickelate particles in the polymer solution, 2) a method of spraying the polymer solution on the lithium nickelate particles, 3) a method of mixing the lithium nickelate particles and the polymer solution There is.

In the step of mixing the lithium nickelate particles and the polymer solution (mixing step), the polymer solution and the lithium nickelate particles are stirred, or the polymer solution containing the lithium nickelate particles is vibrated or fluidized. Preferably, lithium nickelate powder is dispersed in the polymer solution. At the time of this dispersion, the average particle size of the lithium nickelate particles is preferably 1 mm or less, and more preferably 100 μm or less. Further, the polymer solution and the lithium nickelate particles may be heated. Further, after the mixing step, it is preferable to filter the polymer solution from the mixture of the lithium nickelate particles and the polymer solution.

In the step of immersing the mixture of the lithium nickelate particles and the polymer solution in an aqueous alcohol solution (extraction step), the mixture of the lithium nickelate particles and the polymer solution is mixed with the aqueous alcohol solution. As the mixing method, for example, 1) a method in which a mixture of a polymer solution and lithium nickelate particles is immersed in an aqueous alcohol solution, and 2) a method in which an aqueous alcohol solution is sprayed on a mixture of the polymer solution and lithium nickelate particles are used. it can.

Here, the alcohol concentration of the aqueous alcohol solution is preferably 30 wt% or more and 100 wt% or less, more preferably 50 wt% or more and 100 wt% or less, and more preferably 70 wt% or more and 100 wt% or less.
It is preferably set to t% or less. The “alcohol aqueous solution having an alcohol concentration of 30 wt% or more” includes pure water-free alcohol (alcohol 100 wt%). Here, the alcohol concentration of the alcohol aqueous solution is defined as (weight of alcohol / (weight of alcohol + weight of water)) × 100 (wt%). In the present invention,
By adding inexpensive water to the alcohol, the cost of the extraction solvent can be reduced.

In the extraction step, the mixture of lithium nickelate particles and the polymer solution and the aqueous alcohol solution are stirred, or the alcohol aqueous solution containing the mixture of the lithium nickelate particles and the polymer solution is vibrated or fluidized, It is preferable to disperse lithium nickelate provided with a polymer solution in an aqueous alcohol solution. At the time of this dispersion, the average particle size of the lithium nickelate particles is preferably set to 1 mm or less.
m or less.

The alcohol aqueous solution and the lithium nickelate particles may be heated. Further, after the extraction step, it is preferable to filter the aqueous alcohol solution from the mixture of the lithium nickelate particles and the polymer solution.

In the drying step, the lithium nickelate particles containing the polymer are dried. The drying temperature is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher. Further, it is preferable that the gas in the drying chamber is flowing. Further, drying in a reduced pressure atmosphere is preferred. After the drying step, it is preferable to sieve lithium nickelate having a porous polymer on the surface of the particles, and it is preferable to form the particles into a powder.

Further, the present invention is characterized in that the lithium nickelate having a porous polymer on the particle surface is a powder having an average particle diameter of 0.1 μm or more and 50 μm or less. 0.1
When a positive electrode plate using lithium nickelate having an average particle size smaller than μm is manufactured, the discharge capacity of the positive electrode plate is reduced because a large amount of a conductive agent and a binder are used. Further, when a positive electrode plate using lithium nickelate having an average particle size of more than 50 μm is manufactured, the active material is not uniformly applied to the current collector, so that the high-rate discharge performance of the positive electrode plate is reduced. In the present invention, in order to improve the discharge capacity of the positive electrode plate and the discharge performance at a high rate, it is preferable that the average particle diameter is 1 μm or more and 20 μm or less. The average particle size is measured by a laser diffraction / scattering type particle size distribution analyzer.

[0033] The amount of porous polymer present on the surface of the lithium nickelate particles can be adjusted by repeating each of these steps or by controlling the concentration of the polymer solution.

Here, the content of the porous polymer in the lithium nickelate provided with the porous polymer on the particle surface is represented by (weight of the porous polymer / (weight of the porous polymer + weight of the lithium nickelate) )) × 100 (unit: wt)
%).

When the content of the porous polymer present on the surface of the lithium nickelate particles is too low, the porous polymer cannot sufficiently absorb the electrolytic solution. When the lithium nickelate is used for the battery, the charge / discharge cycle performance is hardly improved. Also, when the content of the porous polymer is too high, the porous polymer inhibits the movement of lithium ions, so that a sufficiently high discharge performance cannot be obtained.
Therefore, the content of the porous polymer present on the surface of the lithium nickelate particles is preferably set to 0.01 wt% to 5 wt%.

Further, in order to provide a porous polymer uniformly on the surface of lithium nickelate particles, it is necessary to maintain a uniform polymer solution between particles of the active material. For example, when the viscosity of the polymer solution is high, the solution hardly penetrates into the active material particles and the powder thereof, so that the surface or pores thereof are not uniformly coated with the polymer. Therefore, since the distribution of the electrolyte near the active material is not uniform, a sufficient effect on improving the cycle performance cannot be obtained. Therefore, the viscosity of the polymer solution is desirably 20 mPa · s or less, and more desirably 10 mPa · s or less.

Further, in order to uniformly maintain the polymer solution on the surface of the lithium nickelate particles, the method further includes a step of placing the lithium nickelate particles having the polymer solution at a certain pressure and then increasing the pressure. Is preferred. For example, it is preferable to leave lithium nickelate particles provided with the polymer solution at a pressure of 50 Torr or less, preferably 1 Torr or less, and then return the pressure to atmospheric pressure.

In the present invention, the porous polymer is used not only on the surface of the lithium nickelate particles but also on the surface thereof.
It may be held in pores inside the particles.

Specific examples of the alcohol used in the extraction step of the present invention include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and ethylene glycol. Among them, ethyl alcohol is particularly preferred because the discharge performance at a high rate becomes particularly good and handling is relatively easy.

The lithium nickelate of the present invention is not particularly limited. As a typical example, there is one obtained by partially replacing LiNiO ₂ and nickel with another element. Specifically, LiNi _0.80 Co _0.20 O ₂ , LiNi
_0.80 Al _0.20 O ₂ , LiNi _0.80 Co
_0.17 Al _0.03 O ₂ . Further, the present invention is effective even if these lithium nickelates are contained in other active materials. For example, a mixture with lithium cobaltate, lithium manganate and the like can be mentioned.

The porous polymer of the present invention becomes a porous polymer electrolyte by containing an organic electrolyte. In the case of the porous polymer electrolyte, lithium ions can move not only in the organic electrolytic solution in the pore portion but also in the polymer portion when the polymer portion wets or swells with the organic electrolytic solution. Further, it is preferable that the porous polymer forms a network structure, and that the porous polymer forms a three-dimensional network structure. In addition, the porosity of the porous polymer of the present invention is 40 to 90%.
Desirably, it is 75%.

As the porous polymer of the present invention, those having flexibility capable of coping with expansion and contraction of the volume of the active material due to charge and discharge are preferable, and the polymer needs to be wetted or swelled with the electrolytic solution. Specifically, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polymethyl methacrylate (PMMA), polyvinyl fluoride, polyvinyl chloride, polyvinylidene chloride, Polymethyl acrylate,
Polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene terephthalate, polyhexamethylene adipamide, polycaprolactam, polyvinyl alcohol, polyurethane, polyethylene imine, polycarbonate, polytetrafluoroethylene,
Polyethylene, polypropylene, polybutadiene, polystyrene, polyisoprene, carboxymethylcellulose, methylcellulose and derivatives thereof can be used alone or in combination. Further, a combination of monomers constituting these polymers can be used. Specifically, vinylidene fluoride /
Hexafluoropropylene copolymer (P (VdF / H
FP)), styrene-butadiene rubber, ethylene propylene rubber, styrene-based elastomer, fluorine-based elastomer, olefin-based elastomer, and the like. Among these, PVdF, P (VdF / HF
It is preferable to use P), PAN, PEO, PPO, PMMA and derivatives thereof alone or in combination. Furthermore, polymers containing fluorine are most preferred. Polymers containing fluorine, such as PVdF and P (VdF / HFP), are more electrochemically stable than other polymers, so when lithium nickelate with the same is applied to a lithium ion secondary battery, its performance Is significantly improved.

The solvent for the polymer solution used in the present invention may be any solvent that can dissolve the polymer. Specifically, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, carbonates such as ethyl methyl carbonate, dimethyl ether, diethyl ether, ethyl methyl ether,
Ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone and acetone, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone,
-Methyl-pyrrolidinone and the like.

As a solvent for the electrolytic solution of the non-aqueous electrolyte secondary battery of the present invention, an aprotic solvent is preferable. Specifically, ethylene carbonate, propylene carbonate,
Butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyl Tetrahydrofuran, 1,3-dioxolan, methyl acetate, N
-Methyl-2-pyrrolidone, 4-methyl-1,3-dioxolane, N-methylpyrrolidine, ethyl methyl ketone, methyl propionate, acetone, diethyl ether, ethyl methyl ether, dimethyl ether or the like, or a mixture thereof is used May be.

Further, as a salt to be contained in the electrolytic solution, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCl
O ₄ , LiSCN, LiI, LiCF ₃ SO ₃ , Li
C ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC
1, lithium salts such as LiBr and LiCF ₃ CO ₂ , or mixtures thereof are preferred.

As the negative electrode active material of the nonaqueous electrolyte secondary battery of the present invention, for example, Al, Si, Pb, Sn, Zn, C
alloys of lithium with d, etc., transition metal composite oxides such as LiFe ₂ O ₃ , transition metal oxides such as WO ₂ and MoO ₂ , carbon materials such as graphite and carbon, Li
_{3-x M x} N (provided that, M is a transition metal, 0 ≦ x ≦ 0.
8) and the like, and lithium metal and the like, and a mixture thereof may be used. Examples of carbon materials include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, easily graphitizable carbon such as pyrolytic vapor-grown carbon fibers, phenol resin fired bodies, polyacrylonitrile-based carbon fibers, Isotropic carbon, non-graphitizable carbon such as fired furfuryl alcohol resin, natural graphite, artificial graphite, graphitized MC
There is a graphitic material such as MB, graphitized mesophase pitch-based carbon fiber, graphite whisker, or a mixture thereof.

The current collectors of the positive electrode plate and the negative electrode plate
Any of iron, copper, aluminum, stainless steel, nickel and the like may be used. Further, the shape may be any of a sheet, a foam, a sintered porous body, an expanded lattice, and the like, and furthermore, a hole having an arbitrary shape in the current collector may be formed.

[0048]

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

Example 1 First, 10 g of P (Vd
F / HFP) was dissolved in 990 g of N-methyl-2-pyrrolidone (NMP) to prepare a polymer solution. The viscosity of this solution was 6.4 mPa · s. Here, this P
(VdF / HFP) The molar ratio between VdF and HFP is Vd
F: HFP = 95: 5, and this polymer was used in Examples unless otherwise specified. Next, lithium nickelate having a porous polymer on the particle surface was manufactured. 800 g of lithium nickelate (LiNi _0.85
Co _0.15 O ₂ , average particle size 11.51 μm) and 400
g of the above polymer solution. Thereafter, these were mixed under a reduced pressure of 0.1 Torr to hold the polymer solution between the lithium nickelate particles (mixing step). Next, the excess PV is filtered by suction filtration.
The dF solution was removed from the mixture.

Further, lithium nickelate provided with the polymer solution was immersed in ethyl alcohol (extraction step).
Then, the mixture was stirred to disperse the lithium nickelate powder provided with the polymer, and then, the alcohol was filtered from the mixture. Thereafter, drying was performed at 100 ° C. (drying step) to obtain lithium nickelate particles having a porous polymer on the particle surface. The lithium nickelate was in powder form. The average particle size is 11.58.
μm. Calculated from the change in the weight of the lithium nickel oxide particles at the start and after the drying step, the content of the porous polymer electrolyte was 0.1 wt%.

Next, ten nonaqueous electrolyte secondary batteries using lithium nickelate having a porous polymer on the particle surface as a positive electrode were manufactured.

The positive electrode plate was manufactured as follows. Lithium nickelate with porous polymer on particle surface 5
5 wt%, acetylene black 2 wt%, PVdF4w
t% and NMP39wt% are mixed to form a paste, and the paste is 100 mm wide, 600 mm long, and 20 μm thick.
m of aluminum foil on both sides and dried at 100 ° C. Thereafter, the thickness of the electrode plate was reduced from 270 μm to 165 μm by pressing, and then cut into a size of 26 mm in width and 495 mm in length.

The negative electrode plate was made of graphite 50 wt%, PV
A paste was prepared by mixing 5 wt% of dF and 45 wt% of NMP, and this paste was applied to both sides of a copper foil having a width of 100 mm, a length of 600 mm and a thickness of 10 μm, and dried at 100 ° C. After that, the thickness of the electrode plate was reduced from 250 μm to 195 μm by pressing,
It was cut to a size of 27 mm in width and 450 mm in length.

Next, these positive / negative electrode plates and a thickness of 25
A polyethylene separator having a thickness of 2 μm and a width of 29.5 mm was wound, and then inserted into an aluminum case having a height of 48.0 mm, a width of 29.2 mm, and a thickness of 5.0 mm. further,
An electrolyte obtained by adding 1 mol / l of LiPF ₆ to a mixture of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was injected. At this point, the porous polymer on the surface of the lithium nickelate particles becomes a porous polymer electrolyte. Thus, the battery (A) of the present invention having a nominal capacity of 740 mAh was manufactured. The battery case was provided with a non-return type safety valve.

Next, in the above extraction step, lithium nickelate having a porous polymer on the particle surface was produced by using an ethyl alcohol aqueous solution instead of ethyl alcohol. At this time, 10, 20, 3
Aqueous solutions with ethyl alcohol concentrations of 0, 40, 50, 60, 70, 80 and 90 wt% were used. In the obtained lithium nickelate, the content of the porous polymer was 0.1% by weight. Their average particle size is 1
It was 1.56-11.165 μm. Using these lithium nickelate powders, batteries were manufactured in the same manner as in the above method.

Further, as a comparative example, lithium nickelate having a porous polymer on the particle surface was manufactured by using deionized water as the extraction solvent in the above extraction step, and the lithium nickelate was used. Thus, a conventionally known battery (B) was manufactured.

Next, these batteries were tested under the following conditions. 3. At 25 ° C. and 740 mA current.
After charging to a voltage of 2 V, the battery was subsequently charged at a voltage of 4.2 V for 2 hours. Next, at a constant current of 1480 mA, 2.
Discharged to a voltage of 75V. This discharge current corresponds to high-rate discharge. FIG. 1 shows the relationship between the concentration of ethyl alcohol as the extraction solvent in the extraction step and the discharge capacity of the battery. The data of each cell in FIG. 1 was an average value of 10 cells.

FIG. 1 shows that the discharge performance at a high rate is improved by setting the concentration of ethyl alcohol as the extraction solvent to 30 wt% or more. Further, it was found that the discharge performance at a high rate was significantly improved by setting the concentration to 70 wt% or more.

Comparative Example 1 Next, a non-aqueous electrolyte secondary battery having a porous polymer only in the holes of the positive electrode plate was manufactured as a comparative battery. First, a positive electrode plate was manufactured in the same manner as in Example 1 using lithium nickelate having no porous polymer on the particle surface. Thereafter, before pressing, a porous polymer was applied to the holes of the positive electrode plate by the following method. First, 6 wt% of P (VdF / HF
By immersing the positive electrode plate in the NMP solution of P),
The polymer solution was impregnated into the holes of the electrode plate. Thereafter, excess polymer solution on the surface of the plate was removed by passing the plate between rollers. Furthermore, NMP was extracted by immersing the positive electrode plate in ethyl alcohol to form a porous polymer electrolyte in the holes of the electrode plate. After that, the thickness of the electrode plate was reduced from 270 μm to 165 μm by pressing, and then the width 2
It was cut into a size of 6 mm and length of 495 mm.

Using this positive electrode plate, a conventionally known battery (C) having a nominal capacity of 740 mAh was manufactured in the same manner as in Example 1. Next, the cycle performance of this battery and the battery (A) according to the present invention manufactured using ethyl alcohol in Example 1 were compared. The test was performed under the following conditions. At 25 ° C., the battery was charged at a current value of 740 mA to a voltage value of 4.2 V, and then charged at a voltage value of 4.2 V for 2 hours. Next, the battery was discharged at a current value of 740 mA to a voltage value of 2.75 V. This was repeated 300 times. The result is shown in FIG. As is clear from FIG. 2, the battery (A) of the present invention is different from the conventionally known battery (C).
It was found that the cycle performance was superior to that of.

Comparative Example 2 A conventionally known battery (C) was manufactured by using deionized water instead of ethyl alcohol when a conventionally known battery (C) was manufactured. The tests of the batteries (A), (B), (C) and (D) were performed under the following conditions. At 25 ° C., the battery was charged with a current of 740 mA to a voltage of 4.2 V, and subsequently charged with a voltage of 4.2 V for 2 hours. Next, the battery was discharged to a voltage of 2.75 V at a constant current of 1480 mA. This discharge current corresponds to high-rate discharge. FIG. 3 shows these discharge curves. It was found that the battery (A) according to the present invention exhibited excellent high rate discharge performance.

Example 2 Next, the effects of alcohols other than ethyl alcohol were examined. Here, methyl alcohol, isopropyl alcohol, and ethylene glycol were used. In the same manner as in Example 1, lithium nickel oxide powder having a porous polymer on the particle surface was produced, and ten non-aqueous electrolyte batteries using these powders were produced. Their average particle size is 11.58-11.
It was 70 μm.

Next, these batteries were tested under the same conditions as in Example 1. Table 1 shows the results. Note that the data of each cell in Table 1 was also an average value of 10 cells. As a result, it was found that the use of various alcohols as the extraction solvent significantly improved the performance. In particular, ethyl alcohol was effective for the improvement.

[0064]

[Table 1]

[0065]

According to the present invention, there is provided a method for producing lithium nickelate having a porous polymer on the surface of a particle.
An aqueous solution having an alcohol concentration of t% or more is used. In a non-aqueous electrolyte secondary battery obtained by this manufacturing method and using lithium nickelate having a porous polymer on the particle surface as a positive electrode, the discharge performance and the cycle performance at a high rate are different from those of the conventional one. It is significantly better in comparison.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of ethyl alcohol and the discharge capacity of a non-aqueous electrolyte secondary battery.

FIG. 2 is a diagram comparing the cycle performance of a battery (A) according to the present invention and a conventionally known battery (C).

FIG. 3 is a diagram comparing the high-rate discharge performance of a battery (A) according to the present invention and conventionally known batteries (B), (C) and (D).

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Claims (7)

[Claims] 1. A step of mixing lithium nickelate particles and a polymer solution, a step of immersing the mixture of the lithium nickelate particles and the polymer solution in an aqueous alcohol solution having an alcohol concentration of 30% by weight or more, and the obtained mixture. And a step of drying the powder. The method for producing lithium nickelate having a porous polymer on the surface of particles. 2. The method according to claim 1, wherein, in the step of mixing the lithium nickelate particles and the polymer solution, the lithium nickelate powder is dispersed in the polymer solution. Of producing lithium nickelate. 3. The method according to claim 1, wherein in the step of immersing the mixture of the lithium nickelate particles and the polymer solution in an aqueous alcohol solution, lithium nickelate provided with a polymer is dispersed in the aqueous alcohol solution. A method for producing lithium nickelate having a porous polymer on the surface of particles. 4. The lithium nickelate according to claim 1, wherein the powder has an average particle diameter of 0.1 μm or more and 50 μm or less. 5. The method for producing lithium nickelate according to claim 1, wherein the alcohol is ethyl alcohol. 6. A positive electrode plate for a non-aqueous electrolyte secondary battery, comprising using lithium nickelate having a porous polymer on the particle surface according to claim 1, 2, 3, 4, or 5. 7. A non-aqueous electrolyte secondary battery using the positive electrode plate according to claim 6.