JPH10270024A - Method for producing positive electrode plate for non-aqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an electrode plate for a non-aqueous electrolyte battery which is excellent in high energy density and high rate discharge characteristics. The method for producing a positive electrode plate for a non-aqueous electrolyte battery according to the present invention is a method for producing nickel hydroxide having a spherical shape and / or a shape approximate to a spherical shape, the surface of which mainly contains particles mainly composed of curved surfaces. A method for producing a positive electrode plate for a non-aqueous electrolyte battery, comprising a step of chemically or electrochemically oxidizing a powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a positive electrode plate having an extremely high energy density.

[0002]

2. Description of the Related Art Particles of a positive electrode active material, nickel hydroxide, are directly applied together with a binder to an active material support such as a nickel mesh or a sponge-like porous nickel having a three-dimensionally continuous structure. The positive electrode plate for an alkaline battery can achieve a high capacity and has a very simple manufacturing method, is capable of a continuous process, and is economically advantageous. In this case, the energy density of the positive electrode plate varies greatly depending on the shape and size of the particles of the nickel hydroxide powder used.

According to JP-A-60-131765, the energy density is improved by filling a nickel hydroxide powder having a spherical or nearly spherical particle shape into an active material support such as a sponge-like nickel porous body. It is stated that a positive electrode plate for an alkaline battery can be obtained. In order to easily fill the sponge-like nickel porous body with the paste-like active material, it is desirable that the active material particles used are somewhat smaller.The smaller the particle size of the active material is compared to the pore size of the porous body, the more the porous material skeleton It is considered that the paste is easily filled because the resisting force is small.

However, as the particle size of the active material decreases, the specific surface area increases, and the amount of liquid adsorbed on the particle surface increases. Therefore, in order to obtain a paste having the same viscosity, the smaller the particle size, the smaller the particle size. Requires a lot of liquid,
The content of the active material particles in the paste will decrease.

[0005] Therefore, even if the paste is easily filled in the porous body, the actual energy density is not improved. Here, by forming the nickel hydroxide particles into a spherical or spherical shape, it is possible to suppress an increase in the specific surface area due to a decrease in the particle diameter, and to provide a positive electrode plate for an alkaline battery with improved energy density. I can do that.

On the other hand, in a non-aqueous electrolyte battery such as a lithium battery, a metal foil such as aluminum or copper is used as a current collector, and an active material is suitably used together with a conductive additive such as acetylene black and a binder such as a fluorine-containing polymer. Generally, an electrode is produced by forming a paste using a suitable solvent and applying the mixture on a current collector.

Since the ionic conductivity of the non-aqueous electrolyte is inferior to that of the aqueous electrolyte, the thickness of the active material mixture layer of the electrode plate is usually several tens to improve the high rate discharge characteristics.
A method of making it as thin as 100 μm is used. However, as the active material mixture layer becomes thinner, the amount of the current collector with respect to a certain amount of the battery active material increases, and as a result, the relative amount of the active material in the entire battery decreases, so that the energy density of the battery decreases. I will be forced.

[0008]

As described above, in a non-aqueous electrolyte battery such as a lithium battery, the thickness of the active material mixture layer of the electrode plate is set to several tens in order to improve high rate discharge characteristics.
In many cases, a very thin method of 0 to 100 μm is used. However, as the active material mixture layer becomes thinner, the amount of the current collector with respect to a certain amount of the battery active material increases, and as a result, the relative amount of the active material in the whole battery decreases, so that the energy density of the battery decreases. Invite. Accordingly, there is a need for a method of manufacturing an electrode for a non-aqueous electrolyte battery that improves high-rate discharge characteristics without lowering the energy density.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a manufacturing method for eliminating such disadvantages and improving the energy density of a positive electrode plate for a non-aqueous electrolyte battery. And a step of chemically or electrochemically oxidizing nickel hydroxide mainly containing particles whose surface is mainly composed of a curved surface. Preferably, it is characterized by using nickel hydroxide containing cobalt,
More preferably, the average particle size of the nickel hydroxide is 1 to
The thickness is 100 μm.

In addition, the present invention is characterized in that the nickel hydroxide is held on a conductive porous body having a three-dimensional structure.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a method for producing a positive electrode plate having an extremely high energy density. The present invention has a spherical shape and / or a shape approximate to a spherical shape,
The method further comprises a step of chemically or electrochemically oxidizing nickel hydroxide mainly containing particles whose surface is mainly composed of a curved surface. The shape approximate to a sphere here means a shape close to a sphere, a chicken egg, a substantially chicken egg, a rugby ball, and a substantially rugby ball.

Thus, an electrode plate having high energy density, high rate discharge characteristics, and excellent charge / discharge cycle characteristics can be manufactured. At this time, by using nickel hydroxide powder containing cobalt, the cycle characteristics can be made good and the discharge characteristics can be made very uniform.

Further, the average particle size of nickel hydroxide is set to 1
An electrode plate having an excellent balance between the high-rate discharge characteristics and the energy density can be obtained by selecting from the range of 100 μm.

[0014] In addition, when the nickel hydroxide to be used is held in a conductive porous body having a three-dimensional structure, the energy density of the electrode plate can be further increased.

In the present invention, the active material includes a host material capable of inserting and extracting lithium ions.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method according to the present invention will be described below in detail with reference to an embodiment.

The positive electrode plate according to the present invention was manufactured as follows.

First, a mixed powder of 80 parts of nickel hydroxide powder having a spherical shape and a particle shape similar thereto, 10 parts of carbonyl nickel powder, and 10 parts of cobalt powder obtained by hydrogen reduction of cobalt oxalate was treated with an aqueous solution of carboxymethyl cellulose. This paste is filled into a sponge-like nickel porous body having an average pore diameter of 0.3 mm, a porosity of 96%, and a thickness of 1.7 mm, and dried at 80 ° C. for 1 hour.

Next, after being immersed in a fluororesin dispersion, dried again at 80 ° C. for 1 hour and pressed at a pressure of 500 kg / cm 2 to obtain a positive electrode plate A according to the present invention.

The nickel hydroxide powder having a spherical shape and / or a particle shape similar thereto can be obtained by various methods. Here, when producing nickel hydroxide by a neutralization reaction, fine water serving as a nucleus is used. It was produced by dispersing nickel oxide particles and allowing a reaction to proceed gradually to grow uniform crystals around the nucleus. (5
(See FIG. 5 (a) which is an explanatory view of the particle shape of the nickel hydroxide according to the present invention when observed by SEM at × 00.) For comparison, the particle surface is not mainly composed of a curved surface and is usually used. Using the obtained nickel hydroxide powder (see FIG. 5 (b), which is an explanatory diagram of the conventional nickel hydroxide particles when observed by SEM at 500 times magnification), a conventional positive electrode plate B produced in the same manner as above was obtained. Was.

Nickel hydroxide powder having a spherical shape and a particle shape similar to a sphere, 5 wt% of acetylene black as a conductive material, 5 wt% of polyvinylidene difluoride and 3 wt% of n-methyl-2-pyrrolidole as a binder Was mixed in a dry room to form a paste, and then applied and dried on a stainless steel foil of a current collector to obtain a positive electrode plate A ′ according to the present invention.

In addition, a commonly used nickel hydroxide powder, 5 wt% of acetylene black as a conductive material, 5 wt% of polyvinylidene difluoride as a binder and n-methyl-
A mixture with 3 wt% of 2-pyrrolidol was mixed in a dry room to form a paste, and then applied and dried on a stainless steel foil of a current collector to produce a conventional positive electrode plate B ′.

The positive plates A, B, A 'and B' were anodized in a 5 M aqueous sodium hydroxide solution, washed with water and dried. One positive electrode plate thus obtained and two lithium metal plates of the same size as the counter electrode,
100 ml of a mixed solvent of ethylene carbonate and diethyl carbonate containing 1 M lithium perchlorate in the electrolyte
Was used to produce a test battery.

For the measurement of the potential of the positive electrode, a metallic lithium reference electrode was used. These batteries were subjected to constant current discharge at 25 ° C. at various current densities to 1.5 V.

The average particle diameter of the nickel hydroxide powder used for producing the positive plates A and B is 1 μm to 120 μm.
FIG. 1 shows a change in the amount of the kneading liquid necessary to obtain a paste having a viscosity suitable for filling when the pressure is changed to.

FIG. 1 shows that the positive electrode plate according to the present invention requires a smaller amount of kneading liquid than the conventional method.
This is because the particle shape is spherical and nearly spherical,
It is considered that the specific surface area is extremely small.

The average particle diameter of the nickel hydroxide powder used for producing the positive plates A, B, A ′ and B ′ is 1 μm.
FIG. 2 shows a change in the energy density obtained from the filling amount in the case where the energy density is changed to 120 μm.

FIG. 2 shows that the energy density is significantly improved as compared with the conventional method.

Particularly, when the particle diameter is small, the difference from the conventional method is large. The reason is considered as follows.

That is, when nickel hydroxide powder having an average particle diameter of about 100 μm is used, the paste cannot be sufficiently filled in the porous body due to the large particles. In the case of using conventional nickel hydroxide powder, when the particle size is reduced to about 70 μ, the paste is easily filled, so that the energy density is slightly improved, but when the particle size is further reduced, the specific surface area of the particles increases. The amount of kneading liquid increases,
The energy density drops significantly.

On the other hand, when a nickel hydroxide powder having a spherical or nearly spherical particle shape is used as in the present invention, the specific surface area is extremely small even if the particle diameter is reduced to about 25 to 70 μm. Since the size is small, the effect that the paste can be easily filled is larger than the decrease in the content of the active material particles caused by the increase in the amount of the kneading liquid due to the decrease in the particle size, so that the energy density is considered to be improved. Can be At this time, when the nickel hydroxide powder is held on a conductive porous body having a three-dimensional structure such as the sponge-like nickel porous body used in A, the paste is applied to A ′ formed by applying the paste on the current collector. It is confirmed that the energy density is further improved.

Next, for the positive electrodes A, A ′ and B ′ using nickel hydroxide particles having an average particle diameter of 70 μm, changes in the energy density of the electrodes when the discharge current density is changed are shown in FIG.

FIG. 3 shows that the positive electrode plate according to the present invention has a higher energy density because the volume ratio of the active material in the electrode plate is higher than that of the conventional method.
Further, it can be seen that the dependency of the energy density of the electrode plate on the discharge current density, that is, the high-rate discharge characteristic is at the same level as that of the conventional method. As described with reference to FIG.
Also in this case, the positive electrode plate A in which the nickel hydroxide powder is held on a conductive porous body having a three-dimensional structure, such as a sponge-like nickel porous body, is obtained by applying the paste on the current collector. It was found that the energy density and the high-rate discharge characteristics were further improved as compared with A ′.

FIG. 4 shows the change in the discharge capacity retention rate of the positive plates A and A 'according to the present invention and the positive plate B' according to the conventional method as the charge / discharge cycle progresses.

As shown in FIG. 4, the positive plates A and A 'according to the present invention are shown.
It can be seen that is superior in the charge / discharge cycle characteristics to the positive electrode plate B 'according to the conventional method. This is because the particle shape of nickel hydroxide used for the positive electrode plate according to the present invention is spherical or / and approximate to spherical, and the crystal growth direction is diverse, so that the volume of the active material accompanying charge / discharge is increased. This is considered to be because the action of expansion and contraction can be dispersed in all directions. This makes it possible to suppress the pulverization of the active material, which is one of the causes of cycle deterioration, and is considered to have contributed to the improvement of charge / discharge cycle characteristics.

On the other hand, the nickel hydroxide powder used for the positive electrode plate B 'according to the conventional method has a shape in which crystals grow in a specific direction, and the effect of volume expansion and contraction of the active material due to charging and discharging is limited only to the specific direction. You will receive it in a concentrated manner. As a result, the active material is liable to be pulverized, and it is considered that the discharge capacity is more greatly reduced as the charge / discharge cycle proceeds.

In fact, when the test electrode was disassembled after 500 cycles, the positive electrode plate B 'was confirmed to be finely divided in the active material. However, the active materials of the positive electrode plates A and A' were different from those at the start of the cycle test. The particle shape was maintained. In this case,
Positive electrode plate A in which nickel hydroxide powder is held on a conductive porous body having a three-dimensional structure such as a sponge-like nickel porous body is compared with A 'obtained by applying paste on a current collector. Thus, the charge / discharge cycle characteristics are further improved.

[0038]

According to the method for producing a positive electrode plate for a non-aqueous electrolyte battery according to the present invention, there is provided a method for producing a positive electrode plate having a spherical shape and / or a shape approximate to a spherical shape, the surface of which mainly contains particles mainly composed of curved surfaces. The method further comprises a step of chemically or electrochemically oxidizing the nickel oxide powder.

As a result, an electrode plate having a high energy density, a high rate discharge characteristic and an excellent charge / discharge cycle characteristic can be manufactured. At this time, by using nickel hydroxide powder containing cobalt, the cycle characteristics can be made good and the discharge characteristics can be made very uniform.

Further, the average particle size of nickel hydroxide is set to 1
By selecting the electrode plate within the range of 100 μm, it is possible to obtain an electrode plate having an excellent balance between high-rate discharge characteristics and energy density.

In addition, by holding nickel hydroxide to be used in a conductive porous body having a three-dimensional structure, the energy density of the electrode plate can be further increased.

As described above, according to the present invention, the energy density of the positive electrode plate for a non-aqueous electrolyte battery can be remarkably improved, and the deterioration of high rate discharge characteristics and charge / discharge cycle characteristics can be suppressed. Although the sponge-like nickel porous body was used as the active material support in the examples of the present invention, the same effect can be obtained when the active material powder is applied using a nickel mesh or a porous nickel plate as the active material support. Is obtained.

Therefore, the industrial value of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the average particle size of nickel hydroxide used in positive plates A and B and the amount of kneading liquid necessary for pasting.

FIG. 2 is a view showing the relationship between the average particle size of nickel hydroxide used in positive electrode plates A, A ′, B and B ′ and discharge current density.

FIG. 3 is a diagram showing the relationship between the discharge current density and the energy density of the positive electrodes A, A ′ and B ′.

FIG. 4 is a diagram showing the relationship between the number of charge / discharge cycles in the positive plates A, A ′ and B ′ and the discharge capacity retention of the active material.

[Procedure amendment]

[Submission date] May 28, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the average particle size of nickel hydroxide used in positive plates A and B and the amount of kneading liquid necessary for pasting.

FIG. 2 is a diagram showing the relationship between the average particle size of nickel hydroxide used in positive electrode plates A, A ′, B and B ′ and energy density.

FIG. 3 is a diagram showing the relationship between the discharge current density and the energy density of the positive electrodes A, A ′ and B ′.

FIG. 4 is a diagram showing the relationship between the number of charge / discharge cycles in the positive plates A, A ′ and B ′ and the discharge capacity retention of the active material.

FIG. 5 is an explanatory view showing a particle shape of nickel hydroxide according to the present invention and a particle shape of nickel hydroxide according to a conventional example.

Claims (4)

[Claims] 1. A method for chemically or electrochemically oxidizing nickel hydroxide having a spherical shape and / or a shape close to a spherical shape, the surface of which is mainly composed of particles mainly composed of curved surfaces. A method for producing a positive electrode plate for a non-aqueous electrolyte battery, comprising: 2. The method for producing a positive electrode plate for a non-aqueous electrolyte battery according to claim 1, wherein nickel hydroxide containing cobalt is used. 3. The method for producing a positive electrode plate for a non-aqueous electrolyte battery according to claim 1, wherein nickel hydroxide having an average particle diameter of 1 to 100 μm is used. 4. The method according to claim 1, wherein the nickel hydroxide is held in a conductive porous body having a three-dimensional structure.
4. The method for producing a positive electrode plate for a non-aqueous electrolyte battery according to 2 or 3.