JPS5822862B2 - alkaline battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the separator for alkaline batteries, and uses a high quality regenerated cellulose membrane to improve the shelf life of the battery.
The purpose is to significantly improve cycle life.

Conventionally, regenerated cellulose membranes, so-called cellophane, have often been used as separators for silver oxide-zinc alkaline batteries, nickel-zinc alkaline batteries, and the like.

Cellophane that is industrially manufactured is usually used for packaging, and its transparency and ease of packaging pose problems.

However, transparency is not necessary for a battery; rather, the purpose is to obtain an alkaline battery with good performance by using a regenerated cellulose membrane that is highly durable in an alkaline electrolyte and has little negative impact on the battery.

The regenerated cellulose membrane, which is a common industrial product mentioned above, is made from wood pulp, and the degree of polymerization of the final product is 300.
It is of a certain degree.

FIG. 1 is a diagram showing a conventional production process of a regenerated cellulose membrane, in which the degree of polymerization of the raw material pulp cellulose is several thousand or more, or the degree of polymerization is lowered to 300 by aging the alkali cellulose or by other steps subsequent thereto.

The reason for this is that if the degree of polymerization is too high to maintain the strength and flexibility of packaging cellophane (regenerated cellulose membrane), the performance will deteriorate.

On the other hand, recycled cellulose with a high degree of polymerization has better alkali resistance and is better for use in batteries.
If it exceeds this level, it will lack flexibility and become brittle, making it impossible to incorporate it into a battery.

The present invention eliminates the above-mentioned conventional drawbacks, and is characterized by using a regenerated cellulose membrane made from fluff (linters) and having a degree of polymerization of 400 to 600 as a separator.

The cellulose membrane according to the present invention replaces wood pulp with fluff (
The regenerated cellulose membrane produced using this material has high α-cellulose purity.
It has excellent alkali resistance and has excellent flexibility and strength even at a high degree of polymerization.

Histologically, fluff is an extension of the epidermal cells of cotton tree seeds, and is called lint (LINT).

The short (about 5 cm) fluff that remains after removing the long fluff fibers used in the production of genuine cotton cloth is called a linter.

With a degree of polymerization of about 300, there is not much difference from conventional regenerated cellulose membranes, but when the degree of polymerization reaches 400, conventional regenerated cellulose membranes lack flexibility and become brittle, whereas the membranes according to the present invention are stiff and resistant to the above-mentioned problems. The performance is even better and a noticeable difference can be seen.

However, as the degree of polymerization reached 600, the viscosity of the piece course increased, and beyond this point, the viscosity became extremely high, making mechanical operation impossible.

From the above results, it was experimentally found that a degree of polymerization of 400 to 600 is optimal.

The above degree of polymerization indicates the size of the molecules constituting the regenerated cellulose membrane, and generally speaking, as the degree of polymerization increases, the hardness of the membrane decreases. It was particularly easy to break when drying, and could not withstand operations such as winding and packaging the product, making it practically impossible to manufacture it.

On the other hand, the degree of polymerization using linter pulp as raw material is 40.
0's regenerated cellulose membrane was stiff and strong and withstood light during product winding and packaging.

The reason for this is that the α-cellulose content in the linter is higher than that of wood, resulting in a strong film.

2M is a manufacturing process diagram of a regenerated cellulose membrane according to an embodiment of the present invention.

Figure 2 is similar to Figure 1, but the bleaching step is omitted.

Bleaching is usually an oxidative bleaching process that turns into saran powder, so when this bleach-treated regenerated cellulose membrane is incorporated into a battery as a separator, it accelerates the oxidative deterioration of the separator that occurs inside the battery. I found out something that I didn't like.

Therefore, in the present invention, it is preferable to use an unbleached regenerated cellulose membrane.

However, in order to reduce the influence of residual sulfur during the manufacturing process, it is also possible to perform a somewhat weaker bleaching process.

The degree of polymerization is adjusted to 400-600 in the step of aging the linter with alkali cellulose.

In addition, the softener used in the regenerated cellulose membrane is an alcohol such as ethylene glycol or glycerin, which dissolves relatively quickly in an alkaline electrolyte, oxidizes the anode active material, and becomes various anions 1, which improves battery performance. have an unfavorable effect on

However, in batteries that undergo photodischarge for a relatively long period of time, the presence of a softener prevents the regenerated cellulose membrane itself from being oxidized and deteriorates due to oxidation instead of the regenerated cellulose membrane acting as a separator. was found to extend.

The optimum value varies depending on how the battery is used.If the softener content exceeds 4%, the oxidation reaction products will increase and affect the battery performance, but in the range of 0 to 3%, the 1b-L filter , - We have experimentally discovered that it has the ability to prolong special missions.

Example 1 A conventional regenerated cellulose membrane and a regenerated cellulose membrane according to the present invention were incorporated into a silver oxide-zinc alkaline battery as a separator, and a photodischarge cycle test was conducted.

The assembled battery has a capacity of 5AH, number of separators is 3,
It consists of 4 anode plates and 5 cathode plates.

The test results are shown in Table 1. From the test results in Table 1, it can be seen that the product of the present invention is superior to the conventional product.

Among the products of the present invention, those using Linter's regenerated cellulose membrane with 2% softener had good low rate photodischarge performance, and those without added softener had good high rate photodischarge performance.

As described above, the present invention can use a separator made of a regenerated cellulose membrane suitable for battery performance, and has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a process diagram for manufacturing a conventional regenerated cellulose membrane, and FIG. 2 is a process diagram for manufacturing a regenerated cellulose membrane used in the present invention.

Claims (1)

[Claims] 1. Polymerization degree of 400 to 60 using fluff (linter) as a raw material
An alkaline storage battery characterized in that a regenerated cellulose membrane of No. 0 is used as a separator. 2 0 to 3% by weight of the softener contained in the regenerated cellulose membrane
An alkaline storage battery according to claim 1. 3. The alkaline storage battery according to claim 1, wherein the regenerated cellulose membrane is not bleached.