JPH04212263A - Separator material for cell and cell with the separator - Google Patents

Abstract

PURPOSE:To eliminate any process imparting electrolyte affinity by using thermally fusible high polymers which is not soluble in a specified electrolyte, and thereby dispersing material which is soluble in the specified electrolyte and concurrently imparts electrolyte affinity, to the thermally weldable high polymers. CONSTITUTION:Thermally fusible high polymers which are not soluble in a specified electrolyte 1 are used as main material for a separator 3 combining a negative electrode 2 with a positive electrode 6, and material which is soluble in the specified electrolyte 1 and imparts electrolyte affinity to the thermally fusible high polymers, is dispersed into the aforesaid main material, so that material for the separator is thereby formed. When the material thus formed for the separator is immersed in the specified electrolyte 1, soluble material dissolves in the electrolyte so as to be formed into the porous body composed of non-soluble high polymeric skeletons which is suitable for the separator 3 where electrolyte affinity is thereby imparted to its surface. This thereby eliminates any process imparting electrolyte affinity, thereby making it possible to assemble a cell by a dry process.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery separator material and a battery using the separator material.

0002

2. Description of the Related Art Materials such as felt made of glass fiber, cellulose paper, and nonwoven fabric made of polypropylene are used for battery separators. These materials are inherently porous and have properties unique to separators, such as liquid permeability, air permeability, and liquid retention, and are used as battery separators after being cut to fit the battery shape.

[0003] Also, for example, in sealed lead-acid batteries, a mat-like separator with improved separator strength is used, which is effective in freeing the installation direction of the battery, ensuring liquid retention, and maintaining the strength of the separator. is demonstrated. This has a structure in which inorganic particles such as alumina are supported inside glass fiber felt.

Furthermore, when a battery is manufactured by winding a spiral electrode using a separator material formed into a sheet, compressive deformation and tearing of the separator occur when winding the electrode, and the electrode In order to prevent compressive deformation and tearing of the separator due to expansion due to charging and discharging, as well as an increase in internal resistance and internal short circuit due to a decrease in the amount of liquid retained, for example, It has been considered to use a separator material having a high electrolyte retention ability, which is made by incorporating titanium oxide having a specific primary particle size, crystal form, and specific surface area into a separator base material made of a nonwoven fabric such as a nonwoven fabric.

On the other hand, in a secondary battery using a hydrogen storage alloy as a negative electrode, the hydrogen storage alloy is pulverized due to volume fluctuations of the negative electrode hydrogen storage alloy during charge/discharge cycles; This caused deterioration of battery characteristics due to falling off from the battery and failure of current collection. As a method to solve this problem, a battery is constructed by heat-sealing a negative electrode made of a hydrogen-absorbing alloy to a heat-fusible resin sheet, and making the hydrogen-absorbing alloy side of this two-layer negative electrode face the separator. Or, a hydrogen storage alloy and a heat-fusible resin are mixed to form a negative electrode.
There is a method of constructing a battery using the separator described above.

[0006]

[Problems to be Solved by the Invention] Some conventional separator materials have poor electrolyte affinity, and especially when glass fiber felt or polypropylene nonwoven fabric is used, these materials are difficult to mix with the electrolyte. In order to make the battery work properly, it is necessary to impart electrophilicity through treatment such as boiling in an electrolyte or treatment with a surfactant, and then
It had to be used as a separator. For this reason, an extra step is required to impart electrolyte affinity, and furthermore, because of the need to go through this step, the electrode and separator must be assembled in the presence of an electrolyte, and each assembly process line is There was the disadvantage that it was a wet type and was exposed to electrolyte. In addition, a battery using the above-mentioned separator has a problem in that as the battery is repeatedly charged and discharged, the effect of the electrolyte-imparting treatment is weakened, resulting in a decrease in battery capacity.

In addition, in the case of batteries using conventional hydrogen storage alloys, it is difficult to make electrical contact between the container and the electrode with the negative electrode using a heat-fusible sheet, and it is difficult to make electrical contact between the container and the electrode. There is a problem in negative electrodes produced by this method that the capacity density per volume decreases, and a new structure has been desired to prevent the deterioration of characteristics due to the pulverization of the hydrogen storage alloy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a battery separator material that can solve the problems of the conventional separators described above.

[0009] Another object of the present invention is to provide a separator material for a battery that can provide a separator that is less deformed in the thickness direction in response to compressive stress.

A further object of the present invention is to provide a battery in which the electrolyte affinity of the separator does not deteriorate and the battery capacity does not decrease even after repeated charging and discharging.

Another object of the present invention is to provide a battery using a hydrogen storage alloy as a negative electrode, which has a high capacity density and is free from deterioration in characteristics due to pulverization of the hydrogen storage alloy.

0012

[Means for Solving the Problems] The battery separator material of the present invention is a molded material made of a mixture of a polymeric material that is insoluble in a predetermined electrolytic solution and a material that is soluble in the electrolytic solution. The molded body is characterized in that the insoluble polymer material serves as a skeleton of the molded body.

[0013] Furthermore, the battery separator material of the present invention, which has reduced deformation due to compressive stress, is characterized in that inorganic powder particles that are insoluble in the predetermined electrolytic solution are dispersed in the separator material. shall be.

The battery of the present invention is characterized in that it has as a separator a porous body mainly made of an insoluble polymer material, which is obtained by removing the soluble material inside the separator material by dissolving it in an electrolytic solution. do. Note that removing the soluble material does not necessarily mean that the soluble material is completely removed, and the separator material initially has a porosity of 0.
It is sufficient if the state changes from a state in which it was porosity to a state in which it has porosity.

The battery of the present invention is characterized in that the negative electrode active material is made of a hydrogen storage alloy, and the hydrogen storage alloy and the separator are bonded together.

The separator material of the present invention can be obtained by, for example, mixing an insoluble polymer material, a soluble material, and an inorganic powder in a predetermined ratio to form a molded body using the insoluble polymer material as a skeleton. Manufactured by. To make a molded body,
High frequency heat fusion method, laser heat fusion method, ultrasonic fusion method,
A pressure welding method, spin casting method, spray casting method, etc. can be used. For example, if you mix a powder of a heat-fusible non-soluble polymer material and a powder of a soluble material and mold the mixture while applying heat, the powder of the non-soluble polymer material will fuse to each other and the powder will become non-soluble. Soluble polymer material powder 3
A separator material having the dimensional combination as a skeleton is formed.

For molding, a molding device shown in the schematic diagram of FIG. 14 or a roll molding device shown in the schematic diagram of FIG. 15 can be used. The mold apparatus shown in FIG. 14 includes a mold 11, an upper punch 13, and a lower punch 14, and a heater 12 is installed in the mold 11. Note that instead of heating using the heater 12 installed, heating may be performed using a hot plate or the like. The roll forming apparatus shown in FIG. 15 consists of two rolls 17 and 18.
The mixed material 16 is put into the small gap between 18,
It is formed into a film shape by rolling. At this time, roll 17
, 18, the heat-fusible insoluble polymer material powder is fused. Note that if the powder of the insoluble polymer material is pressable, it can be molded without heating.

[0018]Furthermore, the ultrasonic welding apparatus shown in the schematic diagram of FIG. 16 can also be used to similarly form by welding. This device utilizes a phenomenon in which particles of powder are thermally fused together due to friction caused by ultrasonic vibrations. The ultrasonic fusion device shown in FIG. 16 includes a vibrator 19, a booster horn 20, a horn 21, and a pedestal 22, and the ultrasonic vibrations generated by the horn 21 are amplified by the booster horn 20. This ultrasonic vibration is transmitted from above to the mixture on the pedestal 22 which is pressed by the vibrator 19, and the powder of the insoluble polymeric material having thermal fusibility is fused to form a separator material.

In addition, at least one of the insoluble polymeric material and the soluble material is dissolved in a specific solvent, and inorganic powder is dispersed, and the spin casting method shown in the explanatory diagram of FIG. 17 or the explanatory diagram of FIG. It can be molded into a film using the spray casting method shown below. In this case, it is preferable to dissolve at least the non-soluble polymer material. In this method, a film-like molded body made of a film-like skeleton of an insoluble polymer material is formed by evaporating the solvent. In the spin casting method shown in FIG. 17, 24 is a spin coater, and 23 is a liquid supply device, in which inorganic powder is dispersed in a mixed solution or dispersion solution of an insoluble polymer material and a soluble material. Solution 27 is filled. In the spray casting method shown in FIG. 18, 25 is a tank containing the same solution 27 as above.
26 is a stirring rod, 28 is a liquid supply pump, 29 is a nozzle, 31
is a developing table, and 30 indicates a formed film obtained by this apparatus.

Examples of materials used for the separator material of the present invention include the following. Examples of non-soluble polymer materials include heat-adhesive polyethylene, polypropylene,
Polytetrafluoroethylene and various substituted products thereof are used, and among these, polyethylene, polypropylene, ethylene-propylene copolymers with polar groups introduced, modified polyolefins such as ionomers, and polytetrafluoroethylene are highly insoluble. Modified polyolefins having maleic anhydride as a substituent are particularly preferred because of their good adhesion between molecular materials and with inorganic powders.
It is preferable because it has high adhesive strength. On the other hand, when used in an aqueous electrolyte, non-soluble polymer materials that can be dissolved into a solution or paste form include nitrocellulose, acrylonitrile, which dissolves in non-aqueous solvents but not in aqueous solutions.
Examples include styrene resins, and when used in nonaqueous electrolytes, there are polyethylene glycols, polyvinyl alcohols, cellulose derivatives, etc.

Examples of soluble materials include polymers such as cellulose derivatives such as carboxymethylcellulose, sodium carboxymethylcellulose, and methylcellulose, agar, starch, and polyvinyl alcohol, and other organic substances such as adipic acid, stearic acid, and glutamic acid. and its salts. In the case of an aqueous electrolyte, basic oxides such as Li2 O4, Na2 O, and K2 O, and basic hydroxides such as LiOH, NaOH, and KOH are used as inorganic substances, and in the case of a non-aqueous electrolyte, LiCl
O4, LiBF4, etc. are used.

The mixing ratio of the insoluble polymer material and the soluble material can be varied within the range of 10 to 90% for the former and 90 to 10% for the latter, but preferably 20 to 60% for each.
%, preferably 80 to 40%. This ratio greatly affects the properties of the separator formed, and its appropriate value varies greatly depending on the materials used, especially the properties of the former.

[0023] As the inorganic powder, inorganic beads such as glass beads, alumina beads, and silica beads, and white alumina carborundum used in abrasives are used. When using these inorganic powders, the base polymer, which is a mixture of an insoluble polymer material and a soluble material to be dispersed and supported, is generally formed into a thin sheet. In particular, it is preferable to use particles having a particle size of 10 to 100 μm. Also,
When mixing, it is better to use particles with a particle size distribution within the above particle size range than to use particles with the same particle size in order to maintain the adhesive strength of the base polymer. This allows the separator made of the base polymer to be more resistant to compressive stress, and to ensure the amount of liquid retained by maintaining porosity. The amount of this inorganic powder mixed is 10 to 4 parts by weight per 100 parts by weight of the insoluble polymer material in the base polymer.
0 parts by weight is preferred. This is because if the mixed amount is less than the above range, the separator's resistance to compressive stress will be significantly reduced, and if it is larger than the above range, the soluble material will be dissolved by the electrolyte, and the separator made of the insoluble polymer material that remains will be left behind. This is because the mechanical strength of the material decreases.

[0024] Furthermore, it is preferable to use inorganic beads as the powder. Inorganic beads have a nearly perfect spherical shape and are well dispersed in the base polymer. For example, even when formed into a thin film separator material with a thickness of about 30 μm, inorganic beads are uniformly dispersed. This is because the adhesive force between the powders of the non-soluble polymer material is less likely to be locally reduced.

[0025]

[Operation] When the battery separator material of the present invention is immersed in a predetermined electrolytic solution, the soluble material dissolves into the electrolytic solution, forming a porous body consisting of a skeleton of an insoluble polymer material. Therefore, the structure is suitable for battery separators. The porosity of this porous body is easily controlled by the mixing ratio of the non-soluble polymeric material and the soluble material. At the same time, due to the action of the soluble material, the surface of the obtained porous body is given electrolyte-philicity. Therefore, if the battery separator material of the present invention is made of a material suitable for the electrolyte of the assembled battery, this separator material can be used in the same way as a normal separator to assemble the battery, and the electrolyte can be supplied during the process. In the process, the soluble material is eluted and comes to act as a regular separator. Then, after all the constituent elements such as electrodes and separator materials are assembled into the battery container, the electrolytic solution is injected for the first time in the final step, so that the assembly process can be carried out in a dry manner. Of course, it is also possible to make the separator in advance from the separator material before assembly into the battery.

[0026] Further, the electrolytic lyophilicity imparted to the porous body obtained from the battery separator material of the present invention is not lost during use as a battery, and furthermore, the soluble material can be mixed with a suitable polymer or inorganic material. (For example, LiOH in the case of an alkaline secondary battery) can improve the charge/discharge cycle life of the battery and the utilization rate of the electrode active material. Therefore, a battery having a separator obtained from the separator material of the present invention has excellent battery characteristics such as cycle characteristics and capacity density.

Furthermore, by dispersing inorganic powder in the separator material, the resistance of the separator to deformation in the thickness direction due to compressive stress can be increased. Therefore, by maintaining the porosity, the amount of liquid retained can be ensured, and an increase in internal resistance can be suppressed. On the other hand, by improving resistance to compressive stress, internal short circuits due to dielectric breakdown of the separator,
Furthermore, heat generation and fire of the battery due to rapid abnormal discharge can be prevented.

[0028] In addition, in a battery in which a hydrogen storage alloy serving as a negative electrode active material is bound to a separator obtained from the separator material of the present invention, the separator binds to the negative electrode active material,
It prevents pulverization during charging and discharging, prevents internal short circuits due to collapse and falling off of the negative electrode, and improves charge-discharge cycle characteristics. The battery of the present invention is assembled by integrating the negative electrode with the separator material of the present invention by a method such as fusion bonding or pressure bonding, and then combining it with the positive electrode. The soluble material dissolves into the electrolyte, and the negative electrode and porous separator are bonded together to form a battery with an integrated structure. Note that the negative electrode and the separator material may be integrated together when the separator material is molded, or may be performed after the molding, and the same method as in the case of molding the separator material can be used. Furthermore, before assembling a battery, a hydrogen storage alloy and a separator material may be bonded together using an electrolytic solution, and then the battery may be assembled using this.

[0029]

【Example】

Example 1 Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram explaining the assembly process of the battery of the present invention, in which 1 is an electrolytic solution, 2 is a negative electrode, 3 is a separator material, 3' is a separator, 4 is a positive electrode can, and 5 is a material for sealing the battery container. 6 is a positive electrode, 7A and 7B are current collectors, 8 is a negative electrode lid, and 9 is a hole.

First, 10 parts by weight of heat-fusible polyethylene and 5 parts by weight of sodium carboxymethylcellulose, which are the materials for the separator material of the present invention, are mixed. Next, after collecting 60 mg of the mixed separator material,
The separator material according to the present invention was prepared by putting it into the molding die 11 of the molding device shown in FIG. 14 and pressing at 120° C. and 100 kgw/cm 2 for about 30 seconds. At this time, the mold 11 having an inner diameter of 20 mm was used.

Next, TiNi, which is the material of the negative electrode, was put into a pressure container (not shown) and heated to 300°C.
Release and absorb gaseous hydrogen at atmospheric pressure, 0.1 Torr
The mixture was gradually cooled to 25° C. while being degassed. After that, 2
Gaseous hydrogen was stored overnight at 5°C and 1 atm.
2 g of TiNi, which is this hydrogen storage alloy, was put into the mold 11 (inner diameter 18 mm) shown in Fig. 1, and then a 100 mesh N
A wire mesh was put in, press-molded from above at 700 kgw/cm2, and taken out to prepare a negative electrode. The negative electrode capacity at this time was 150 mAh. Next, electrochemical conversion treatment is performed in an alkaline aqueous solution such as potassium hydroxide aqueous solution,
A sintered nickel electrode (outer diameter 18 mm) with a capacity of 100 mAh was cut to a predetermined size and charged to prepare a positive electrode.

The negative electrode 2 and positive electrode 6 produced as described above are combined with the separator material 3 in a sandwich manner, placed in the positive electrode can 4 lined with the current collector 7A, and the electrolyte 1 is supplied (Fig. 1(a)). As the electrolytic solution, 300 μl of a 30 wt % potassium hydroxide aqueous solution was used. After this, the current collector 7B,
The negative electrode cover 8 is placed on it and sealed by caulking (FIG. 1(b)). Note that the current collectors 7A and 7B may be welded together to the positive electrode can 4 and the negative electrode lid 8, respectively, or one of them may be welded to the positive electrode can 4 and the negative electrode lid 8, respectively. Moreover, the positive and negative electrodes may be directly welded to the container without using these current collectors 7A and 7B.

In the thus assembled battery, the carboxymethyl cellulose sodium in the separator material 3 swells inside the battery, and a part of it is dissolved in the electrolytic solution to form pores 9, and the separator material 3 becomes heat-fusible. The separator 3' is made of a three-dimensional porous material mainly made of polyethylene, resulting in a battery having a separator with excellent electrolyte permeability and excellent ionic conductivity (FIG. 1(c)). FIG. 2 shows the discharge curve of the battery obtained in this example as it cycles.

Example 2 Heat-fusible polyethylene 10 was used as the material for the separator material.
parts by weight, 5 parts by weight of sodium carboxymethyl cellulose, and inorganic powder component white alumina (WA-#50
0.0, average particle size 34.0 μm), 2 parts by weight of this separator material was mixed, and 60 mg was taken out, and then placed in the mold 11 of the mold device shown in FIG. 14. A battery was produced in the same manner as in Example 1, except that a separator material was produced by pressing and molding at 120° C. and 100 kgw/cm 2 for about 30 seconds.

In the thus assembled battery, the carboxymethylcellulose sodium in the separator material swells inside the battery, and a portion of it is dissolved in the electrolyte, causing the separator material to contain heat-fusible polyethylene in which white alumina is dispersed. The battery has a separator mainly composed of a three-dimensional porous body, which has excellent electrolyte permeability and excellent ionic conductivity. Further, by dispersing white alumina, it becomes difficult to cause a decrease in liquid retention due to a decrease in the thickness of the separator material and a decrease in battery characteristics due to a decrease in porosity due to compressive stress during the caulking process.

FIG. 3 shows the discharge curve of the battery of this example as it cycles. Comparing the battery of this example with the battery of Example 1, it can be seen that the battery of this example has a larger discharge capacity for each cycle and a higher electrode utilization rate.

Comparative Example 1 Same as Examples 1 and 2 except that a polypropylene nonwoven fabric punched into a circular shape with an outer diameter of 20 mm was subjected to an alkali boiling treatment and used as a separator that was given electrophilicity. A battery was fabricated using the same method. That is, the battery produced in this example was the same as in Example 1 except for the separator part.
It has a similar structure. FIG. 4 shows the discharge curve of the battery of this comparative example as it cycles. Comparing the batteries of Example 1 and Example 2 with the battery of this comparative example, the batteries of Example 1 and Example 2 have a larger discharge capacity for each cycle and a higher electrode utilization rate. I understand that.

Example 3 10 parts by weight of heat-fusible polyethylene and 5 parts by weight of sodium carboxymethylcellulose, which are materials for the separator of the present invention, are mixed. Next, after taking 60 mg of the mixed separator material, it was put into the molding mold 11 of the molding device shown in FIG.
Temporary molding is performed by pressing at kgw/cm2 for 30 seconds. At this time, the molding die 11 has an inner diameter of 20 mm.
I used the one from

Next, TiNi, which is the material of the negative electrode, was put into a pressure container (not shown) and heated to 300°C.
Release and absorb gaseous hydrogen at atmospheric pressure, 0.1 Torr
The mixture was gradually cooled to 25° C. while being degassed. After that, 2
It was stored overnight under conditions of 5°C and 1 atm to produce a hydrogen storage alloy. 2 g of TiNi, which became the hydrogen storage alloy, was put into the mold 11 containing the above-mentioned temporarily formed separator material according to the present invention, press-molded from above at 700 kgw/cm2, taken out and cooled. In this way, a separator material in which the separator material and the negative electrode were bound and integrated was prepared. The capacity of this negative electrode was 150 mAh.

Furthermore, this integrated separator material is
In combination with the same positive electrode as used in Example 1, a battery was produced in the same manner as in Example 1. This battery differs from Example 1 in that the negative electrode and separator material are bonded together and that the negative electrode does not contain a Ni wire mesh.

FIG. 5 shows the discharge curve of the battery of this example as it cycles.

The battery of this example has the same initial discharge capacity as the battery of example 1, but the capacity decreases less with cycling. This is because the negative electrode hydrogen storage alloy is prevented from falling off from the electrode due to volume fluctuations associated with charge/discharge cycles, and from generating poor current collection due to pulverization. Furthermore, compared to the battery of Example 1, the battery of Example 3 does not require a Ni wire gauze for holding the hydrogen storage alloy of the negative electrode, so the volumetric capacity density of the negative electrode can be increased.

Example 4 As materials for the separator, 10 parts by weight of heat-fusible polyethylene, 5 parts by weight of sodium carboxymethyl cellulose, and white alumina (WA-#500, average particle size 34
．． 0 μm), 2 parts by weight of this separator material was mixed, and 60 mg of the separator material was taken out, and then placed in the mold 11 of the molding device shown in FIG.
A battery was produced in the same manner as in Example 3, except that the separator material was temporarily molded by pressing and molding at 0 kgw/cm2 for about 30 seconds.

FIG. 6 shows the discharge curve of the battery of this example as it cycles.

Comparing the battery of Example 3 with the battery of this example, it can be seen that the battery of this example has a larger discharge capacity for each cycle and a higher electrode utilization rate. Also, compared to the battery of Example 3, the battery of this example has
The battery has a large capacity, and its capacity decreases little with cycles.

The battery of this example differs from the battery of example 2 in that the negative electrode and separator material are fixed together and that the negative electrode does not contain a Ni wire mesh. The battery of this example has the same initial discharge capacity as the battery of example 2, but the decrease in capacity due to cycling is less. Furthermore, since the battery of this example does not require a Ni wire mesh for holding the hydrogen storage alloy of the negative electrode, the capacity density of the negative electrode can be increased.

Example 5 10 parts by weight of heat-fusible polytetrafluoroethylene and 4 parts by weight of polyvinyl alcohol, which are materials for a separator material, are mixed. Next, this mixed separator material is placed between hot rolling forming rolls 17 and 18 heated to 260° C. of the roll forming apparatus shown in FIG. 15 to produce a sheet-like separator material. In this example, a separator material with a maximum width of 20 cm was continuously produced using a hot rolling forming roll with a width of 20 cm.

Next, TiNi, which is the material of the negative electrode, was put into a pressure container (not shown) and heated to 300°C.
Gaseous hydrogen at 0 atm is released and absorbed, and at the same temperature, 0.
A hydrogen storage alloy was prepared by degassing overnight under the condition of 1 Torr. This hydrogen storage alloy, TiNi, was molded into wires with a wire diameter of 0.1 mm and a
A negative electrode is prepared by processing into a sheet integrated with a 00 mesh Ni wire mesh.

Further, as a positive electrode, a sheet-shaped sintered nickel electrode is prepared which has been subjected to electrochemical conversion treatment in an alkaline aqueous solution such as a potassium hydroxide aqueous solution to bring it into a discharge state. Note that the capacity of the positive electrode was 500 mAh, and the capacity of the negative electrode was 800 mAh.

[0050] The above negative electrode, separator material, and positive electrode were stacked in this order, wound up in a spiral shape, and installed in a battery container, and a 30 wt % potassium hydroxide aqueous solution as an electrolyte was supplied.
I sealed it and assembled an AA nickel metal hydride battery.

[0051] Inside the battery of this example, the polyvinyl alcohol in the separator material swells, and a part of it is dissolved and eluted into the electrolyte (potassium hydroxide aqueous solution) to form heat-fusible polytetrafluoroethylene. The separator is mainly made of a three-dimensional porous material. Normally, polytetrafluoroethylene has poor compatibility with electrolytes, etc., but in the case of the separator material of the present invention, this tendency was small and was not observed. Moreover, this separator provided a battery having a separator with excellent electrolyte permeability and excellent ionic conductivity.

FIG. 7 shows the discharge curve of this example.

An additional 100 batteries of this example were manufactured and the rate of cycle failure was tested. The column of Example 5 in Table 1 shows the number of defects that occurred every 100 cycles in the battery of this example. The term "defective" as used herein refers to an abnormal open circuit voltage, an abnormal discharge voltage, an abnormal charge voltage, or a case where the discharge capacity is reduced to 50% or less compared to the initial capacity.

Example 6 As materials for the separator material, 10 parts by weight of heat-fusible polytetrafluoroethylene, 4 parts by weight of polyvinyl alcohol, and glass beads (average particle size 24 μm, particle size range 15 to
40 μm), and after mixing the materials of this separator material, it was placed between 20 cm wide hot rolling forming rolls 17 and 18 heated to 260° C. of the roll forming apparatus shown in FIG. A battery was produced in the same manner as in Example 5, except that a sheet-like separator material was produced.

[0055] In the battery of this example, like the battery of Example 5, the polyvinyl alcohol in the separator material swells inside the battery, and a part of it is dissolved and eluted into the electrolyte (potassium hydroxide aqueous solution). Then, the separator becomes a three-dimensional porous body mainly made of heat-fusible polytetrafluoroethylene in which glass beads are dispersed. Further, the separator material of the battery of this example, like the battery of Example 5, had a separator with excellent electrolyte affinity, electrolyte permeability, and ionic conductivity.

FIG. 8 shows the discharge curve of the battery of this example as it cycles.

[0057] Similarly to Example 5, 10 extra batteries were added.
0 pieces were produced and the incidence of cycle failure was tested. The results are shown in the column of Example 6 in Table 1.

[0058] Comparing the battery of Example 5 with the battery of this example, the discharge curve shows that the battery of this example has a larger discharge capacity for each cycle and a higher electrode utilization rate. I understand. Furthermore, from Table 1, it can be seen that the incidence of defects is lower in the battery of this example than in the battery of example 5. This is because the battery of this example has an increased thickness of the separator compared to the battery of Example 5 due to compressive stress during the electrode winding process and changes in electrode thickness due to charging and discharging reactions.
This is because there is little decrease in liquid retention capacity due to the decrease in porosity or deterioration of battery characteristics due to decrease in porosity.

Comparative Example 2 In place of the separator of Example 5, an AA nickel-metal hydride battery was fabricated using a 40 mm wide polypropylene nonwoven fabric that had been given electrophilic properties by an alkali boiling process as a separator. . This battery has the same structure as Example 5 except for the separator portion.

FIG. 9 shows the discharge curve of the battery of Comparative Example 2.

In addition, 100 extra batteries of this comparative example were manufactured and tested for cycle failure rate in the same manner as in Example 5. The results are shown in the Comparative Example 2 column of Table 1.

Comparing the batteries of Examples 5 and 6 with the battery of this comparative example, the discharge curves show that the batteries of Examples 5 and 6 have a larger discharge capacity at each cycle, and the electrode It can be seen that the usage rate is high. Also, Table 1
It can be seen from this that the batteries of Examples 5 and 6 have a lower failure rate than the battery of this comparative example.

Example 7 The separator material used in Example 5 was heated to 260° C. in the roll molding device shown in FIG.
7 and 18 and subjected to the same treatment as in Example 5.
Ni is uniformly dispersed onto the separator material formed into a sheet, and this is then placed between another hot rolling forming roll heated to 260°C to form a sheet consisting of the separator material and TiNi. A separator material sheet to which a negative electrode was bound was produced. Using this, an AA type nickel-metal hydride battery similar to that in Example 5 was produced. The battery of this example differs from the battery of example 5 in that the negative electrode and the separator are bonded together and that the negative electrode does not contain a Ni wire mesh.

FIG. 10 shows the discharge curve of the battery of this example.

[0065] Furthermore, the battery of this example has an extra 1
00 pieces were produced, and the cycle failure rate was tested in the same manner as in Example 5. The results are shown in the column of Example 7 in Table 1. Comparing the battery of this example with the battery of example 5 using discharge curves, it is found that although the initial discharge capacity is the same, the battery of this example shows less decrease in capacity due to cycling. Further, from Table 1, it can be seen that the battery of this example has a lower incidence of defects than the battery of Example 5.

Furthermore, this embodiment does not require a Ni wire gauze for holding the hydrogen storage alloy of the negative electrode, so the volumetric capacity density of the negative electrode can be increased.

Example 8 The separator material used in Example 6 was heated to 260° C. in the roll molding device shown in FIG.
7 and 18 and subjected to the same treatment as in Example 6.
Ni is uniformly dispersed onto the separator material formed into a sheet, and this is then placed between another hot rolling forming roll heated to 260°C to form a sheet consisting of the separator material and TiNi. A separator material sheet to which a negative electrode was bound was produced. Using this, an AA type nickel-metal hydride battery similar to that in Example 6 was produced. FIG. 11 shows the discharge curve of the battery of this example.

In addition, 100 extra batteries J of this example were manufactured, and the number of defects per cycle was tested in the same manner as in Example 5. The results are shown in the column of Example 8 in Table 1.

[0069] Comparing the battery of Example 7 and the battery of this example from the discharge curve, it was found that the battery of this example had a larger discharge capacity for each cycle and a higher electrode utilization rate. I understand. Further, when the battery of this example is compared with the battery of example 8 according to Table 1, it can be seen that the battery of this example has a lower failure rate.

Furthermore, the battery of this example differs from the battery of Example 6 in that the negative electrode and the separator are bonded together and that the negative electrode does not contain a Ni wire mesh, but the discharge curves show that Then, although the initial discharge capacity is the same, the decrease in capacity due to cycling is smaller in this example. Furthermore, since the battery of this example does not require a Ni wire mesh for holding the hydrogen storage alloy of the negative electrode, the volumetric capacity density of the negative electrode can be increased.

Example 9 After mixing 10 parts by weight of modified polypropylene having maleic anhydride as a substituent and 3 parts by weight of polyvinyl alcohol, which are the materials for the separator material of the present invention, the mixed material for the separator material was prepared as shown in the figure. A sheet-like separator material was produced by putting the mixture between hot rolling molding rolls 17 and 18 heated to 180° C. of the roll molding apparatus shown in No. 15. In this example, a separator material with a maximum width of 20 cm was continuously produced using a roll with a width of 20 cm.

Next, TiNi, which is the material of the negative electrode, was put into a pressure container (not shown) and heated to 300°C.
Release and absorb gaseous hydrogen at atmospheric pressure, same temperature, 0.1
A hydrogen storage alloy was prepared by degassing overnight under Torr conditions. This hydrogen storage alloy TiNi was processed into a sheet shape integrated with a 100 mesh Ni wire gauze having a wire diameter of 0.1 mm using a rolling roll to prepare a negative electrode.

Further, as a positive electrode, a sheet-shaped sintered nickel electrode was prepared which had been subjected to electrochemical conversion treatment in an alkaline aqueous solution such as a potassium hydroxide aqueous solution to bring it into a discharge state. Note that the capacity of the positive electrode was 500 mAh, and the capacity of the negative electrode was 800 mAh.

[0074] The above negative electrode, separator material, and positive electrode were stacked in this order, rolled up into a spiral shape, and installed in a battery container, and a 30 wt % potassium hydroxide aqueous solution as an electrolyte was supplied.
I sealed it and assembled an AA nickel metal hydride battery.

Inside this battery, as in Example 5, the polyvinyl alcohol in the separator material swells, and a portion of it is dissolved and eluted into the electrolyte (potassium hydroxide aqueous solution).
The separator is a three-dimensional porous material mainly made of modified polypropylene. According to this example, the battery has a separator with high electrolyte affinity, excellent electrolyte permeability, and excellent ionic conductivity.

FIG. 12 shows the discharge curve of the battery of this example.

In addition, 100 additional batteries were manufactured and tested for cycle failure rate in the same manner as in Example 5. The results are shown in the column of Example 9 in Table 1.

This example differs from Example 5 in that modified polypropylene having maleic anhydride as a substituent was used instead of polytetrafluoroethylene as the insoluble polymer material. Comparing this example with Example 6, it can be seen that the capacity of each cycle is larger in this example, and the utilization rate of the electrode is higher. Furthermore, when comparing this example and Example 5 from Table 1, it can be seen that the incidence of defects is lower in this example.

Example 10 As materials for the separator material, 10 parts by weight of modified polypropylene having maleic anhydride as a substituent, 3 parts by weight of polyvinyl alcohol, and glass beads (average particle size 24 μm) were used.
m, particle size range: 15 to 40 μm), and then the mixed separator material was heated to 180° C. in the roll forming apparatus shown in FIG. 15 using hot rolling forming rolls 17 and 18 with a width of 20 cm. A battery was produced in the same manner as in Example 9, except that a sheet-like separator material having a maximum width of 20 cm was produced by inserting the material between the two. FIG. 13 shows the discharge curve of the battery of this example.

Furthermore, 100 extra batteries were manufactured and tested for cycle failure rate in the same manner as in Example 5. The results are shown in the column of Example 10 in Table 1.

Comparing the battery of Example 9 and the battery of this example using discharge curves, it is found that the battery of this example has a larger discharge capacity at each cycle and a higher electrode utilization rate. Recognize. Further, from Table 1, when comparing the present invention and Example 9, it can be seen that the incidence of defects is lower in the present invention.

Furthermore, compared to the separator material of Battery K of Example 9, the separator material of this example has a lower thickness due to compressive stress during the electrode winding process and changes in electrode thickness due to charging and discharging reactions. We were able to fabricate an excellent battery with little decrease in liquid holding capacity due to increase/decrease in porosity or deterioration of battery characteristics due to decrease in porosity.

As shown above, in the batteries of the present example and comparative example, heat fusion was used to mold the separator material and to bond the negative electrode and the separator material. It is also possible to bind and integrate them simultaneously with molding by a method such as spin casting or the like. Note that the solution includes a paste-like solution.

In the batteries of this example and comparative example, only TiNi was used as the negative electrode active material, but other hydrogen storage alloys such as LaNi5 and MmNi5 (MmNi5), which are a type of rare earth alloy, were shown. : mischmetal, a mixture of several kinds of lanthanoids) and its Ni and La
, Mm is replaced with various transition elements (for example, LaNi3.5Co0.7Al0.8 and MmNi2.0
Co2.2Al0.8), ZrV alloy, TiCo, etc. can also be used.

[0085] Generally, the positive electrode mixture, which is the main component of the positive electrode, includes a positive electrode active material, a conductive agent, and a binder. In some cases, punched metal or nickel wire mesh, which is a nickel-plated iron plate, may be included as an internal conductor. Examples of the positive electrode active material include manganese dioxide,
Oxidizing agents such as nickel oxide, tungsten trioxide, lead dioxide, and molybdenum trioxide may be used, but manganese dioxide and the nickel oxide used in this example are preferred. Further, the above-mentioned conductive agent is an electronically conductive substance added to ensure electronic conductivity in the mixture. Examples include acetylene black, artificial graphite, graphite, carbon black, nickel powder, etc., with graphite and nickel powder being preferred. Furthermore, the binder is a substance added to improve the binding properties and moldability of the two powders. Examples include carboxymethylcellulose, polytetrafluoroethylene, salts of carboxymethylcellulose, polyvinyl alcohol, polyethylene, agar, methylcellulose, and the like. The conductive agent and the binder are mixed in the positive electrode mixture in an amount of 3 to 20% by weight.

[0086]

[Table 1]

[0087]

[Effects of the Invention] According to the battery separator material of the present invention,
This eliminates the need for a step to impart electrolyte properties, making it possible to assemble the battery in a dry manner.

Furthermore, according to the present invention, it is possible to obtain a separator material that does not lose its electrolytic properties even after repeated charging and discharging, so that a battery with high electrode utilization, high capacity density, and excellent cycle characteristics can be obtained. can be created.

When inorganic powder is dispersed in the battery separator material of the present invention, the resistance of the separator to compressive stress is improved and the porosity is maintained. Thereby, the amount of liquid retained is ensured, and an increase in internal resistance is suppressed. Furthermore, by improving the resistance to compressive stress, it is possible to prevent a reduction in the thickness of the separator and the resulting heat generation and ignition due to internal short circuits due to dielectric breakdown and rapid abnormal discharge. Furthermore, since it has excellent mechanical strength, a large-area separator can be easily produced.

On the other hand, according to the battery in which the negative electrode and separator material of the present invention are bonded, it is possible to prevent changes in battery characteristics due to pulverization of the hydrogen storage alloy, and the electrical connection of the negative electrode to the container can be prevented. It is also possible to increase the capacity density of the negative electrode, making it possible to produce an excellent battery. Furthermore, large-area electrodes can be easily produced, and large-capacity batteries can also be easily produced.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a battery assembly process according to Example 1.

FIG. 2 is a diagram showing a discharge curve of a battery according to Example 1.

FIG. 3 is a diagram showing a discharge curve of a battery according to Example 2.

FIG. 4 is a diagram showing a discharge curve of a battery according to Comparative Example 1.

FIG. 5 is a diagram showing a discharge curve of a battery according to Example 3.

FIG. 6 is a diagram showing a discharge curve of a battery according to Example 4.

FIG. 7 is a diagram showing a discharge curve of a battery according to Example 5.

FIG. 8 is a diagram showing a discharge curve of a battery according to Example 6.

9 is a diagram showing a discharge curve of a battery according to Comparative Example 2. FIG.

FIG. 10 is a diagram showing a discharge curve of a battery according to Example 7.

FIG. 11 is a diagram showing a discharge curve of a battery according to Example 8.

FIG. 12 is a diagram showing a discharge curve of a battery according to Example 9.

FIG. 13 is a diagram showing a discharge curve of a battery according to Example 10.

FIG. 14 is a schematic configuration diagram of a molding device for molding the separator material of the present invention.

FIG. 15 is a schematic configuration diagram of a roll forming apparatus for forming the separator material of the present invention.

FIG. 16 is a schematic configuration diagram of an ultrasonic welding device for molding the separator material of the present invention.

FIG. 17 is an explanatory diagram for explaining a spin casting method for molding the separator material of the present invention.

FIG. 18 is an explanatory diagram for explaining a spray casting method for molding the separator material of the present invention.

[Explanation of symbols]

1　Electrolyte solution 2 Negative electrode 3 Separator material 3’ separator 4 Positive electrode

Claims (4)

[Claims] 1. A molded body comprising a mixture of a polymer material that is insoluble in a predetermined electrolyte solution and a material that is soluble in the electrolyte solution, wherein the insoluble polymer material is A separator material for a battery, characterized in that the material serves as a skeleton of the molded body. 2. A battery separator material, characterized in that the battery separator material according to claim 1 is dispersed with inorganic powder particles having no solubility in an electrolytic solution. 3. A separator comprising a porous body mainly made of an insoluble polymer material, which is obtained by removing the soluble material inside the battery separator material according to claim 1 or 2 by dissolving it in an electrolytic solution. A battery characterized by: 4. The battery according to claim 3, wherein the negative electrode active material is made of a hydrogen storage alloy, and the hydrogen storage alloy and the separator are bonded together.