JPH0760681B2 - Method for producing nickel positive electrode - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a nickel hydroxide positive electrode for a battery, more specifically, an alkaline battery having nickel as a positive electrode, a nickel hydride alloy battery, a nickel hydrogen battery, a nickel cadmium battery, a nickel iron battery, The present invention relates to a method for producing a nickel hydroxide positive electrode used in a nickel zinc battery or the like.

In this specification, the terms "%" and "parts" mean "wt%" and "parts by weight", respectively.

[0003]

2. Description of the Related Art Nickel positive electrodes for batteries are roughly classified into "sintering type" products and "paste type" products. Among these, the paste-type nickel positive electrode has advantages that it is easier to reduce the weight, a high-capacity battery can be obtained, and the manufacturing cost is lower than that of the sintered nickel positive electrode.

At present, the paste type nickel positive electrode is mainly used in the form of using a sponge-like metal porous body or a fibrous metal porous body as an electrode substrate. A paste type nickel positive electrode using such a metal porous support is generally prepared by adding a thickener, a binder and the like to nickel hydroxide powder which is an active material and further adding a cobalt compound, cobalt or the like as a conductive auxiliary material. Add metal powder,
After forming a paste together with water, the paste is filled into a metal porous support, dried, and pressure-molded,
Being manufactured. The conductive auxiliary material is added to obtain the same performance as that of the sintered nickel positive electrode, and by this addition, a conductive coating film of cobalt or a cobalt compound is formed on the surface of the nickel hydroxide particles, and It is believed that the utilization rate will improve. However, the paste-type nickel positive electrode using such a metal porous support has a drawback in that it has a large electric resistance due to its structure and a large degree of capacity reduction when discharged with a large current. In addition, the pasted nickel positive electrode has a drawback that the positive electrode active material falls off due to external vibration, repeated charge / discharge cycles, etc., and the battery capacity gradually decreases. However, the problem of this active material falling off is that the active material is firmly held in the structure of the paste type nickel battery (cylindrical battery, etc.) in which the electrodes are tightly adhered and fixed to each other, such as the sealed type. So it wasn't a big deal.

With the increasing interest in the global environment in recent years,
Electric cars are gaining attention. When using the above-mentioned paste-type nickel battery as a stacked type prismatic battery that is usually used as a power source for electric vehicles, the mechanical strength of the paste-type nickel battery can be improved under severe operating conditions such as external vibration and repeated charging and discharging. The problem that the capacity of the battery is gradually decreased cannot be ignored, mainly due to the loss of the positive electrode active material caused by the low strength.

[0006]

Therefore, the present invention is to provide a paste type nickel positive electrode in an alkaline nickel battery which exhibits excellent durability even under severe use conditions as a power source for electric vehicles. The main purpose is.

[0007]

The present inventor has conducted research in view of the current state of the art as described above, and as a result, the nickel active material used in the production of the paste-type nickel positive electrode was previously prepared by using a nickel salt solution. When the treatment is carried out or the nickel active material is filled in the metal porous support which is the positive electrode substrate and then treated with the nickel salt solution, the problems of the prior art are substantially eliminated or significantly It was found to be reduced to.

[0008] That is, the present invention provides the following method for producing a nickel positive electrode: 1 In producing a nickel positive electrode, nickel hydroxide is the main component and contains a conductive material, a conductive auxiliary material and a binder. A solution containing a nickel salt is added to a nickel active material to prepare a nickel active material paste, which is filled in a metal porous support, dried, pressure-molded, and then subjected to chemical conversion treatment. Method for producing nickel positive electrode. 2. When manufacturing a nickel positive electrode, a liquid component is added to a nickel active material containing nickel hydroxide as a main component and containing a conductive material, a conductive auxiliary material and a binder to prepare a nickel active material paste, A method for producing a nickel positive electrode, which comprises filling a porous support, drying, impregnating a solution containing a nickel salt, drying, press-molding, and then performing a chemical conversion treatment.

In the following, the invention of the above item 1 is referred to as the first invention of the present application, the invention of the above item 2 is referred to as the second invention of the present application,
Both inventions are collectively referred to as the present invention.

The nickel active material itself used in the present invention is no different from known materials.

As the nickel hydroxide component, for example, cadmium (about 1 to 10%), cobalt (0.3 to 5%)
Degree), zinc (about 0.5 to 8%), and magnesium (about 0.5 to 8%) within the above range, and the tap density is about 1.5 to 2.3 g / ml. The following is exemplified.

Other components used in the nickel active material include conductive materials, conductive aids, and binders. As the conductive material, nickel powder (for example, “Nickel powder # 255” released by Inco), cobalt powder (for example, “Cobalt mesh powder Co-E”, released by MHI Corporation) Graphite powder (S.E.)
(Sold by C company) etc. are exemplified, and it is used in a ratio of about 3 to 10% of the weight of the nickel active material.
As the conductive aid, metallic cobalt and cobalt oxide,
Examples of cobalt compounds such as cobalt hydroxide are used in a proportion of about 3 to 10% by weight of the nickel active material. As the binder, polytetrafluoroethylene (P
TFE), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc. are exemplified, and they are used in a ratio necessary to give each component a necessary viscosity.

In the present invention, the known positive electrode substrate may be used as it is. Examples of such a substrate include a foam substrate made of nickel, copper, etc., a sintered porous substrate, a metal fiber substrate, a porous body obtained by plating a base material such as iron with nickel, copper, etc., a metal-based porous body such as punching metal, etc. A substrate may be used.

In the first invention of the present application, a nickel salt solution is blended when the above nickel active material is formed into a paste. Examples of such a nickel salt include inorganic nickel salts such as nickel sulfate, nickel nitrate, nickel halide and nickel sulfamate, and organic nickel salts such as nickel acetate and nickel citrate. As a solvent for making a solution, water or an organic solvent such as alcohol or acetone can be used alone or in an appropriate mixture. Such a nickel salt solution is not only useful for chemical conversion treatment of the nickel active material, but also functions as a binder for forming a paste. When forming the paste, in order to evenly disperse the nickel active material,
If necessary, alcohols such as ethanol, surfactants, and known dispersants such as sodium hexametaphosphate can be appropriately added. The water content in the paste is
Although not particularly limited, it is usually about 30 to 200%.

In the first invention of the present application, the porous positive electrode substrate is filled with the paste obtained as described above, and then dried.
Press molding. At this time, it is desirable to perform drying until the water content becomes about 2 to 20%, more preferably about 8 to 30%, and then press molding. If it is excessively dried, the subsequent press molding process may become difficult. The pressure during press molding is not particularly limited, but is usually about 200 to 5000 kg / cm ² ,
More preferably, it is about 300 to 1000 kg / cm ² . The positive electrode substrate after pressure molding can be dried and, if necessary, dipped in the solution of the above-mentioned binder and dried in order to more effectively prevent the active material from falling off.

In the first invention of the present application, the positive electrode substrate press-molded as described above is then immersed in an alkaline solution,
Chemical conversion treatment. Examples of the alkaline solution include a solution containing at least one alkali metal hydroxide such as sodium hydroxide, potassium hydroxide and lithium hydroxide.
The chemical conversion treatment uses an alkali metal hydroxide solution having an alkali concentration of about 1 to 12 M, more preferably about 4 to 8 M, and a treatment temperature of about 0 to 120 ° C., more preferably about 40 to 90 ° C. It is carried out by immersing the positive electrode substrate molded in an aqueous solution for 1 hour or more, more preferably for 3 to 12 hours.

In the second invention of the present application, water or a mixture of water and alcohol is added to the same nickel active material as described above to form a paste, which is filled in a porous positive electrode substrate and dried to obtain a water content. After adjustment and pressure molding, impregnation with the same nickel salt solution as used in the first invention of the present application,
dry. Water content in paste, drying conditions after filling,
The pressure molding conditions and the like are the same as in the case of the first invention of the present application. Next, the molded positive electrode substrate is immersed in an alkaline solution and subjected to chemical conversion treatment in the same manner as in the first invention of the present application.

In the second invention of the present application, a nickel salt solution is impregnated prior to pressure molding of a porous positive electrode substrate which is filled with a paste and dried, and then dried and molded, and again impregnated with the nickel salt solution. Let it dry. In this case, the amount of nickel salt impregnated can be increased to further improve the performance of the nickel positive electrode.

The nickel positive electrode thus obtained is used in an alkaline battery, a nickel hydride battery, a nickel hydride battery, a nickel cadmium battery, a nickel iron battery, a nickel zinc battery or the like which uses nickel as a positive electrode.
used.

[0020]

According to the present invention, the nickel salt solution used for filling the nickel active material into the porous metal support is solidified through the drying step, and the nickel salt also functions as a binder. Since it exhibits, it is possible to prevent the active material filled in from dropping off during the subsequent electrode manufacturing process.

Further, during the chemical conversion treatment step, the nickel salt in the filled active material is chemically changed to generate new nickel hydroxide in the voids between the filled nickel hydroxide particles, Since the adhesion between the filled nickel hydroxide particles and the added conductive material or porous metal support is improved,
The electrical resistance is reduced and the mechanical strength of the nickel electrode itself produced is also improved.

As a result, the degree of capacity reduction during high-current discharge is small, the active material does not drop off due to repeated charging / discharging cycles, external vibration, etc., has excellent durability, and has stable characteristics. It is possible to produce a nickel positive electrode that also has the advantages of a mold.

[0023]

EXAMPLES Examples, comparative examples and test examples are shown below,
The features of the present invention will be further clarified. Example 1 After 84 parts of nickel hydroxide powder, 10 parts of nickel mesh powder as a conductive material and 16 parts of cobalt mesh powder as a conductive auxiliary material were dry-mixed, 100 parts of a 1: 1 mixture of pure water and ethanol was added. And kneaded to prepare a paste. Next, the obtained nickel hydroxide paste was filled in a nickel felt substrate as a positive electrode substrate and dried.

Next, the positive electrode substrate processed as described above was impregnated with a 30% nickel nitrate aqueous solution and dried at 80 ° C. to remove excess water to adjust the water content to 10%, and then 500 kg / cm. Press molding was performed at a pressure of ² .

Then, the pressed positive electrode substrate is again subjected to 20%.
An aqueous nickel nitrate solution was impregnated and dried at 80 ° C. to prepare a predetermined paste type nickel positive electrode. Furthermore, in order to prevent the active material from falling off, this positive electrode is made to contain 4% of PTFE.
After being dipped in the liquid containing it, it was dried at 80 ° C.

Next, the above positive electrode substrate was immersed in a 6M aqueous potassium hydroxide solution at 80 ° C. for 4 hours to perform a chemical conversion treatment.

The nickel positive electrode, which has been subjected to the above-mentioned treatment, is reused again.
After completely dried at 0 ° C., laminated with a nickel-hydrogen storage alloy negative electrode through a hydrophilic polypropylene separator to form an electrode group, the electrode group was housed in an outer container, and a 6M potassium hydroxide-1M lithium hydroxide electrolytic solution was added. After injection, an open nickel hydride battery was assembled. Example 2 After 84 parts of nickel hydroxide powder, 10 parts of nickel mesh powder as a conductive material and 6 parts of cobalt mesh powder as a conductive auxiliary material were dry mixed, a 1: 1 mixture 60 of a 30% nickel nitrate aqueous solution and ethanol 60 Parts were added and kneaded to prepare a paste. Next, the obtained nickel hydroxide paste was filled in a nickel felt substrate as a positive electrode substrate and dried at 80 ° C. to remove excess water to a water content of 10%, and then 500 kg / cm 2.
Press molding was performed at a pressure of ² .

Next, the pressed positive electrode substrate was dried at 80 ° C. to prepare a predetermined paste type nickel positive electrode. Next, in order to prevent the active material from falling off, this positive electrode substrate was immersed in a liquid containing 4% of PTFE and then dried at 80 ° C.

Next, the above positive electrode substrate was immersed in a 6 M aqueous potassium hydroxide solution at 80 ° C. for 4 hours to perform a chemical conversion treatment.

The positive electrode which has been subjected to the above treatment is completely dried again at 80 ° C., laminated with a nickel-hydrogen storage alloy negative electrode through a hydrophilic polypropylene separator to prepare an electrode group, which is then housed in an outer container, An open type nickel hydride battery was assembled by injecting a 6M potassium hydroxide-1M lithium hydroxide electrolytic solution. Comparative Example 1 A nickel hydroxide paste was prepared in the same manner as in Example 1, the positive electrode substrate was filled with the obtained paste, and then the same treatment as in Example 1 was sequentially performed without impregnation with a nickel salt solution. Then, an open-type nickel hydride battery having the same dimensions as in Example 1 was assembled. Test Example 1 With respect to the open-type nickel metal hydride batteries obtained in Examples 1 and 2 and Comparative Example 1, as a capacity test, 0.1 CmA and 150% charge were performed at 20 ° C., and 0.8 V was applied at 0.1 CmA. Discharge was performed as the final voltage, and the same operation was repeated 5 times. Furthermore, only the charging condition is 0.15CmA
, 0.3CmA, 0.5CmA and discharging under the same conditions to measure the active material utilization rate. Then, the theoretical capacity per 1g of nickel hydroxide was set to 298mAh and the result was calculated. The ratio is shown in FIG. 1 as the utilization rate.

As is apparent from FIG. 1, Example 1 and Example 2 in which a nickel salt solution was used during the production of the nickel positive electrode.
In the battery of No. 1, the active material utilization rate reached about 90%, whereas in the battery of Comparative Example 1 in which the nickel salt solution was not used during the production of the nickel positive electrode, the active material utilization rate remained at a low value of about 70%. ing. Test Example 2 With respect to the open nickel hydride batteries obtained in Examples 1 and 2 and Comparative Example 1, respectively, as a high rate discharge test,
Charge at 150% at 0.5CmA at 20 ° C, measure the capacity at a discharge current of 0.2CmA with a final voltage of 0.8V, and further, under the same charging conditions, with a final voltage of 0.8V to determine the discharge current. The capacity was measured by discharging from 1 CmA to 3 CmA.

The results are shown in FIG. 2 as a ratio to the capacity at 0.2 CmA discharge.

As is apparent from FIG. 2, the battery of Example 2 using the nickel salt solution when forming the positive electrode active material into a paste was larger than the battery of Comparative Example 1 using no nickel salt solution. The degree of capacity reduction during current discharge is particularly small,
It is clear that it exhibits excellent high rate discharge characteristics.

The battery of Example 1 in which the positive electrode substrate was filled with the paste and then impregnated with the nickel salt solution showed a smaller degree of capacity decrease than the battery of Comparative Example 1 in which the nickel salt solution was not used. Is clear. Test Example 3 With respect to the open-type nickel hydride batteries obtained in Examples 1 and 2 and Comparative Example 1, respectively, a life test of 20
Charging for 3 hours at 0.5CmA charging current at ℃,
The discharge current was 0.5 CmA with 0.8 V as the final voltage, and the difference between the initial discharge time and the discharge time after 100 cycles was measured.

The results are shown in FIG. 3 as a graph of discharge time vs. discharge voltage.

As is apparent from FIG. 3, Examples 1 and 2
In the battery obtained in 1., almost no decrease in capacity (shortening of discharge time) was observed, whereas in the battery of Comparative Example 1, the decrease in capacity reached about 50%. In particular, it is apparent that the battery of Example 2 has a very small decrease in capacity.

Further, in the batteries of Examples 1 and 2, almost no active material dropped out in the electrolytic solution was observed even after the test, whereas in the battery of Comparative Example 1, the active material dropped out in the electrolytic solution. A large amount of the active material was found. From this,
In the batteries of Example 1 and Example 2, it is considered that the fall of the battery capacity is suppressed by preventing the active material from falling off.

[Brief description of drawings]

FIG. 1 is a graph showing the active material utilization rate after charge / discharge cycles under predetermined conditions for the open-type nickel metal hydride batteries obtained in Examples 1 and 2 and Comparative Example 1, respectively.

[Fig. 2] The open-type nickel metal hydride batteries obtained in Examples 1 and 2 and Comparative Example 1 were each charged under a constant charge condition after a charge / discharge cycle under predetermined conditions, and the discharge current was changed from 0.2 CmA to 3 Cm. The graph shows the change in capacity when changed to 0.0 CmA as a ratio (%) to the capacity when discharged at 0.2 CmA under the same charge condition.

FIG. 3 is a graph comparing the initial discharge time with the discharge time after 100 cycles under the same conditions for the open-type nickel metal hydride batteries obtained in Examples 1 and 2 and Comparative Example 1, respectively.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Koichi Mori, 80 Nakane-cho, Soka-shi, Saitama (72) Inventor Hajime Kashima 42-16 Itsukishin-machi, Noda-shi, Chiba

Claims (2)

[Claims] 1. When manufacturing a nickel positive electrode, a nickel active material paste is prepared by adding a solution containing a nickel salt to a nickel active material containing nickel hydroxide as a main component and containing a conductive material, a conductive aid and a binder. Is prepared, filled in a metal porous support, dried, pressure-molded, and then subjected to chemical conversion treatment, to obtain a nickel positive electrode. 2. A nickel active material paste is prepared by adding a liquid component to a nickel active material containing nickel hydroxide as a main component and containing a conductive material, a conductive auxiliary material and a binder in the production of a nickel positive electrode. A method for producing a nickel positive electrode, characterized in that the porous metal support is filled with this, dried, impregnated with a solution containing a nickel salt, dried, pressure-molded, and then subjected to chemical conversion treatment.