JPH0963637A - Manufacture of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a battery characteristic without extending process more than conventional one. SOLUTION: Roughly conforming the mesh of the sieve for sorting negative electrode active material powder and the mesh of the sieve for sorting the positive electrode active material powder will roughly conform the diameter of the thin hole of the negative electrode or the positive electrode made by using this powder or the diameter of median and the distribution to each other. Accordingly, the quantity of electrolyte contained in the negative electrode and that of the positive electrode roughly conforms to each other, and the drop of battery reaction by the shortage of electrolyte in the electrode on the side where the electrolyte is low can be prevented, and the battery performance improves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sealed hydrogen battery, and more particularly to improving the characteristics thereof.

[0002]

2. Description of the Related Art In an alkaline secondary battery such as a conventional nickel-hydrogen battery in which a hydrogen-absorbing alloy electrode is used as a negative electrode and nickel hydroxide is used as a positive electrode, coarse particles formed by a predetermined graining method have a predetermined mesh width. A negative electrode active material powder having a predetermined unimodal distribution with an average diameter separated by sieving is mixed with a thickener or binder made of an organic polymer material and water to preform or directly form a paste. , A negative electrode is formed by pressure bonding to a metal current collector, and coarse particles formed by a predetermined particle formation method are separated by a sieve of a predetermined mesh to obtain a positive electrode active material powder having an average diameter having a predetermined unimodal distribution characteristic. Preforming or directly forming a paste formed by mixing with a thickener or binder made of an organic polymer material and water,
It is manufactured by pressure-bonding to a metal current collector to form a positive electrode, and immersing the negative electrode and the positive electrode in an alkaline electrolyte in a battery case with a separator interposed therebetween.

[0003]

In the above secondary battery, charge / discharge is performed in the liquid-solid-gas coexisting state of the electrolyte, electrode and gas on the surface of the pores in the negative electrode and the positive electrode formed by solidifying the active material powder. However, in the case of the negative electrode and the positive electrode produced by the above-mentioned conventional method, the distribution amount (permeation amount) of the alkaline electrolyte in the electrode is
However, this may cause a shortage of the alkaline electrolyte to suppress the battery reaction and reduce the battery performance such as high rate discharge characteristics and cycle life.

The present invention has been made in view of the above problems, and it is a problem to be solved to realize improvement of battery characteristics without extending the process as compared with the conventional case.

[0005]

Means for Solving the Problems and Effects of the Invention A first constitution of the present invention is a thickener or binder made of an organic polymer material for a negative electrode active material powder selected through a sieve having a predetermined mesh width. And preforming a paste formed by mixing with water, or directly by pressure bonding to a metal current collector to form a negative electrode,
A positive electrode active material powder selected through a sieve having a predetermined mesh width is mixed with a thickener or binder made of an organic polymer material and water to preform a paste or directly to a metal current collector. In a method for manufacturing a secondary battery, which comprises forming a positive electrode by pressure bonding, and immersing the negative electrode and the positive electrode in an alkaline electrolytic solution in a battery case with a separator interposed therebetween, a porosity of the negative electrode and a void of the positive electrode. It is a method of manufacturing a secondary battery, which is characterized in that the porosity is substantially the same. The thickener is an additive for facilitating slurrying of the powder, and the binder is an additive for binding the powder. The thickener and the binder can be mixed with water in advance or can be mixed with the powder in a state of being dissolved in water.

Incidentally, the term "substantially the same porosity" as used in this configuration means that
When the porosity of the negative electrode (total volume of pores / volume of the negative electrode and positive electrode) is X and the porosity of the positive electrode is Y, the difference between the porosities is (XY), and The average porosity is ((X + Y)
/ 2), the variation of both porosities (2 (X
It means that the absolute value of −Y) / (X + Y)) is 0.5 or less, more preferably 0.2 or less.

However, the porosity can be measured, for example, by the following method. First, put the dry negative electrode (or positive electrode) in a container, inject a sufficient amount of the alkaline electrolyte solution pre-measured, leave it for a predetermined time (for example, 36 hours), and then measure the amount or weight of the remaining alkaline electrolyte solution. . This gives the amount of absorbed alkaline electrolyte, from which the porosity can be estimated. Alternatively, a dry negative electrode (or positive electrode) whose weight has been measured in advance is placed in a container, a sufficient amount of alkaline electrolyte is injected, and the mixture is allowed to stand for a predetermined time (for example, 36 hours), and then, the negative electrode that has absorbed the alkaline electrolyte (or The weight of the positive electrode) can be measured again, and the porosity can be estimated from the weight difference. In addition, the porosity of the negative electrode (or the positive electrode) can be estimated from the porosity of the metal current collector and the dry weight and specific gravity of the paste pressure-bonded thereto. That is, it is easy to measure the porosity of the electrode itself.

With this structure, it is possible to improve the battery characteristics without extending the process as compared with the conventional case. Explaining in detail, by making the porosities of both electrodes substantially the same, the alkaline electrolyte will penetrate into both electrodes uniformly and in an equal amount, and the battery reaction rate and reaction amount at the positive electrode and the battery reaction rate at the negative electrode Since the reaction amounts match, the battery performance such as high rate discharge characteristics, battery internal pressure characteristics, and cycle life can be improved as a whole.

Incidentally, as a method of making both coarse particles into particles, it is preferable to use the same means such as mechanical pulverization or rapid cooling. In this way, the distribution of the average diameters of both coarse particles before sieving can be made more consistent, so that the battery reaction rate and reaction amount at the positive electrode and the battery reaction rate and reaction amount at the negative electrode are This is more consistent, and the battery performance can be further improved.

A second structure of the present invention is further characterized in that, in the first structure, the mesh widths of the both screens are substantially the same. In this specification, the above-mentioned approximately coincidence means that the mesh width (average width of each gap of the sieve) of the sieve for selecting the negative electrode active material powder is A, and the mesh of the sieve for selecting the positive electrode active material powder is When the mesh width is B, the difference between both mesh widths is (AB), and the average of both mesh widths is ((A + B) / 2), the variation of both mesh widths (2 (A- It means that the absolute value of (B) / (A + B)) is 0.5 or less, preferably 0.2 or less.

In this configuration, the mode (median value) and distribution range of the particle size (powder diameter) of both active material powders can be made substantially the same as in the first configuration, so that they are formed on both poles. The average width (average cross-sectional area) of each of the pores can be made to substantially match, and the battery reaction rate and reaction amount at the positive electrode and the battery reaction rate and reaction amount at the negative electrode can be further made to match. As high rate discharge characteristics, battery internal pressure characteristics,
Battery performance such as cycle life can be improved.

A third structure of the present invention is that in the above-mentioned first structure, the mode of the diameter of the negative electrode active material powder and the mode of the diameter of the positive electrode active material powder are substantially matched. It has a feature. To be exact, the diameter of the powder means the average diameter of the powder. In this specification, the approximate match of the mode of the diameter is
The diameter a of the negative electrode active material powder and the diameter b of the positive electrode active material powder are respectively distributed in a unimodal shape (distribution shape with one peak), and the difference between the median values (modes) of both diameters is (a− b)
And the average of the median values of both diameters is ((a + b) /
2), the absolute value of the variation (2 (a−b) / (a + b)) of the median values of the two diameters is 0.5 or less,
It preferably means 0.2 or less.

According to this structure, since the mode values (median values) of the diameters of the negative electrode active material powder and the positive electrode active material powder are in good agreement, the diameter of the pores formed between these powders is the negative electrode. Since the positive electrode and the positive electrode are more matched, the battery characteristics are further improved. A fourth configuration of the present invention is characterized in that, in the first configuration, the mode of the diameter of the pores in the negative electrode and the mode of the diameter of the pores in the positive electrode are substantially matched. I am trying. To be precise, the diameter of the pores means the average diameter of the pores.

In the present specification, the term "substantially equal in diameter" means that the diameter c of the pores in the negative electrode and the diameter d of the pores in the positive electrode are distributed in a unimodal shape (a distribution shape with one peak). , The difference between the median values (mode values) of both diameters is (cd), and the average of the median values of both diameters is ((c + d) / 2), the median value of both diameters is Variation (2 (c-
This means that the absolute value of d) / (c + d)) is 0.5 or less, preferably 0.2 or less.

According to this structure, the mode values of the diameters of the pores of the negative electrode and the pores of the positive electrode match well, so that the battery characteristics are further improved. A fifth structure of the present invention is the same as the fourth structure, wherein 95% or more of the pores are distributed in a unimodal form within a range of 1500 angstroms or less. The difference between the mode value of the diameter and the mode value of the diameter of the pores of the negative electrode is set to 20 angstroms or less.

According to a sixth aspect of the present invention, in addition to the above-mentioned fourth aspect, 95% or more of the pores have a unimodal distribution in the range of 1000 angstroms or less.
The difference between the mode of the diameter of the pores of the positive electrode and the mode of the diameter of the pores of the negative electrode is 10 angstroms or less. In a seventh configuration of the present invention, further, in the fourth configuration, 95% or more of the pore diameters are distributed in a unimodal manner within a range of 500 angstroms or less, and the pores of the positive electrode are The difference between the mode value of the diameter and the mode value of the diameter of the pores of the negative electrode is 5 angstroms or less.

According to the above fifth to seventh configurations, since the mode (median value) of the diameters of the pores of the negative electrode and the pores of the positive electrode and the distribution range thereof are well matched, the battery characteristics are further improved. improves.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described based on the following examples.

[0019]

Example: The composition is MmNi _3.8 Co _0.75 Al _0.3 Mn
Hydrogen storage alloy powder of _0.35 (La / Mm = 0.6) was mechanically pulverized and screened with a sieve having a predetermined mesh width. Hydrogen storage alloy powder was selected as a thickening agent. Methyl cellulose (MC) with a degree of polymerization of about 50,000 was 1 wt%. An aqueous solution was added to the hydrogen storage alloy powder in an amount of 30 wt% and stirred to form a paste. next,
This paste is mixed with a foamed nickel current collector (575 g / m ² ).
Was filled in a roll, and dried at 70 to 80 ° C., and negative electrodes a, b, and c having a thickness of 0.6 mm were manufactured by a roll press. The negative electrode a was made of a hydrogen storage alloy powder having a sieve of 100 mesh and a diameter of 150 μm or less, and the negative electrode b was made of a hydrogen storage alloy powder of 200 mesh and a diameter of 75 μm or less. The negative electrode c is made of hydrogen storage alloy powder having a sieve of 330 mesh and a diameter of 50 μm or less.

Further, nickel hydroxide powder mechanically pulverized and screened with a sieve having a predetermined mesh width is used as a thickening agent for methyl cellulose (MC) having a degree of polymerization of about 50,000.
30 wt% aqueous solution of nickel hydroxide powder
t% was added and stirred to form a paste. Next, this paste was filled in a foamed nickel current collector (575 g / m ² ) and dried at 70 to 80 ° C., and the positive electrodes e, f, and g having a thickness of 0.6 mm were subjected to the same roll pressing as above. It was made. The positive electrode d was made of nickel hydroxide powder having a sieve of 100 mesh and a diameter of 150 μm or less, and the positive electrode e was made of nickel hydroxide powder of 200 mesh and a diameter of 75 μm or less. The positive electrode f is made of nickel hydroxide powder having a sieve of 330 mesh and a diameter of 50 μm or less.

Next, the pore distributions of the positive electrode and the negative electrode were measured using a nitrogen gas adsorption type BET measuring device, and then the polypropylene electrode was sandwiched and wound to form a sub-C size cylindrical electrode assembly. This is put in a cylindrical battery case, and 5 cc of 6 NKOH aqueous solution is injected and hermetically sealed, so that 9 types of batteries (101 to 109) in which the above negative electrodes a to c and positive electrodes d to f are combined are hermetically sealed. Five batteries were prepared for each. Battery 101 is a combination of negative electrode b and positive electrode d, battery 102 is a combination of negative electrode b and positive electrode e, battery 103 is a combination of negative electrode b and positive electrode f, and battery 104 is negative electrode a and positive electrode d. In combination with the battery 10
5 is a combination of negative electrode a and positive electrode e, battery 106 is a combination of negative electrode a and positive electrode f, battery 107 is a combination of negative electrode c and positive electrode d, and battery 108 is negative electrode c and positive electrode e.
And the battery 109 is a combination of the negative electrode c and the positive electrode f.

(Test 1) 100 of each battery 101-109
The result of examining the capacity retention rate ((remaining capacity / initial capacity) × 100%) after cycle charge / discharge is shown in FIG. However, the charging and discharging cycle was performed at 0.2c for 5.5 hours, and discharging was performed at 0.4c until the terminal voltage became 1V. The vertical axis of FIG. 1 is the average value of the capacity retention rates of the five batteries. From FIG. 1, it is possible to obtain an excellent capacity retention rate (cycle life) when the mesh widths of two types of sieves for selecting both powders are equal, and the capacity retention rate is better when the mesh width of the sieve is smaller. It was found that (cycle life) was obtained.

(Test 2) 100 of each battery 101-109
FIG. 2 shows the result of examining the capacity retention rate during high rate discharge after cycle charge and discharge. However, charging was carried out at 0.2c for 6 hours, and discharging was carried out at 3c until the terminal voltage reached 0.8V. The vertical axis of FIG. 2 is the average value of the capacity retention rates of the five batteries. From FIG. 2, an excellent capacity retention rate (cycle life) is obtained when the mesh widths of the two types of sieves for selecting both powders are equal, and the capacity retention rate is better when the mesh width of the sieve is smaller. It was found that (cycle life) was obtained.

(Test 3) 100 of each battery 101-109
FIG. 3 shows the results of examining the internal pressure of the battery at the end of charging after cycle charging / discharging. However, the charging and discharging cycle was performed at 0.2 c for 5.5 hours, and discharging was performed at 0.4 c until the terminal voltage became 1V. The vertical axis of FIG. 3 is the average value of the battery internal pressures at the end of charging of the five batteries. From FIG. 3, it was found that the increase in the battery internal pressure was small when the mesh widths of the two types of sieves for selecting both powders were equal, and that the smaller the mesh width of the sieve was, the less the increase in the battery internal pressure was.

Next, the distribution of the pores of the electrodes a to f is shown in FIGS. From these figures, it can be seen that the more consistent the pore distribution, the better the battery characteristics, and the smaller the pore diameter, the better the battery characteristics. It can be seen that in order to make the pore distributions uniform, the mesh width of the sieve of the negative electrode active material powder and the mesh width of the sieve of the positive electrode active material powder should be made as uniform as possible. For example, the mesh width (gap width) of the sieve for selecting the negative electrode active material powder is A, the mesh width of the sieve for selecting the positive electrode active material powder is B, and the difference between both mesh widths is (AB). The average of mesh width is ((A + B)
/ 2), the difference (AB) between the two mesh widths may be 50% or less, more preferably 20% or less of the average ((A + B) / 2). As described above, by making the mesh widths of both screens substantially the same, the mode of the diameter of the negative electrode active material powder and the mode of the diameter of the positive electrode active material powder and the distribution range thereof can be made substantially the same. As a result, the median values of the pore diameters in the negative electrode and the positive electrode formed by molding these powders and the distribution range thereof are well matched, and the amount of the electrolyte solution injected into the battery case penetrates uniformly and evenly. Thus, the battery reaction rate and reaction amount at the positive electrode and the battery reaction rate and reaction amount at the negative electrode are matched to improve battery performance such as high rate discharge characteristics, battery internal pressure characteristics, and cycle life as a whole.

In other words, the battery performance is achieved by making the mode values of the diameters of both active material powders and the distribution range substantially coincide with each other. By doing so, the mode and distribution range of the diameter of the pores formed between these powders will be more consistent between the negative electrode and the positive electrode, and the battery characteristics will be further improved. Further, in this example, the ratio of the thickener to the active material powder, the packing density of the paste in the foamed nickel porous body, and the pressure of the roll press were made to match between the negative electrode and the positive electrode. Thereby, the distribution of the pores of the negative electrode and the positive electrode can be better matched, and the battery performance can be further improved.

After all, 95% or more of the pores have a unimodal distribution in the range of 1500 angstroms or less, preferably 1000 angstroms or less, and more preferably 500 angstroms or less, and the pore size of the positive electrode. The difference between the mode and the mode of the pore size of the negative electrode is 25
If it is at most%, good battery characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a capacity maintenance ratio ((remaining capacity / initial capacity) × 100 of each battery 101 to 109 after 50 cycles of charge / discharge.
FIG.

FIG. 2 is a diagram showing a result of examining a capacity retention rate at high rate discharge after 50 cycles of charge / discharge of each of the batteries 101 to 109.

FIG. 3 is a diagram showing the battery internal pressure at the end of charging after 50 cycles of charging / discharging of each battery 101-109.

FIG. 4 is a diagram showing a distribution of pores of an electrode a.

FIG. 5 is a diagram showing a distribution of pores of an electrode b.

FIG. 6 is a diagram showing a distribution of pores of an electrode c.

FIG. 7 is a diagram showing a distribution of pores of an electrode d.

FIG. 8 is a diagram showing a distribution of pores of an electrode e.

FIG. 9 is a diagram showing a distribution of pores of an electrode f.

Claims (7)

[Claims] 1. A paste formed by mixing a negative electrode active material powder selected through a sieve having a predetermined mesh width with a thickener or binder made of an organic polymer material and water, or directly preforming the paste. , A negative electrode was formed by pressure bonding to a metal current collector, and the positive electrode active material powder selected through a sieve having a predetermined mesh width was mixed with a thickener or binder made of an organic polymer material and water. Preform the paste or directly,
In a method of manufacturing a secondary battery, which is formed by pressing a metal current collector to form a positive electrode, and immersing the negative electrode and the positive electrode in an alkaline electrolyte in a battery case with a separator interposed therebetween, the porosity of the negative electrode. And the porosity of the positive electrode are substantially equal to each other. 2. The method for producing a secondary battery according to claim 1, wherein the mesh widths of the both screens are substantially the same. 3. The method for producing a secondary battery according to claim 1, wherein the mode of the diameter of the negative electrode active material powder and the mode of the diameter of the positive electrode active material powder are made to substantially coincide with each other. 4. The method for producing a secondary battery according to claim 1, wherein the mode value of the diameter of the pores in the negative electrode and the mode value of the diameter of the pores in the positive electrode are substantially matched. 5. The diameter of 95% or more of the pores is unimodally distributed within a range of 1500 angstroms or less,
The method for manufacturing a secondary battery according to claim 4, wherein the difference between the mode value of the diameter of the pores of the positive electrode and the mode value of the diameter of the pores of the negative electrode is 20 angstroms or less. 6. 95% or more of the pore diameters are unimodally distributed within a range of 1000 angstroms or less,
The method for manufacturing a secondary battery according to claim 4, wherein the difference between the mode of the diameter of the pores of the positive electrode and the mode of the diameter of the pores of the negative electrode is 10 angstroms or less. 7. The diameter of 95% or more of the pores is distributed in a unimodal form within a range of 500 angstroms or less, and the mode of the diameter of the pores of the positive electrode and the pores of the negative electrode are The method for manufacturing a secondary battery according to claim 4, wherein the difference from the mode value of the diameter is 5 angstroms or less.