KR20010046461A - The gel electrolyte for a sealed lead storage battery - Google Patents

Abstract

PURPOSE: A gel electrolyte of closed-type lead acid battery is provided, which simplifies its manufacturing process of the lead acid battery, stabilizes its structure and improves the life performance of the battery. CONSTITUTION: The gel electrolyte of closed-type lead acid battery is prepared by mixing sulfuric acid with silica such as Deggusa Aerosil 200 having a particle specific area of 200 square meter/gram with stirring at a high speed of not less than 2,000 revolution per minute, further contains 0.1-0.5 wt.% of starch as a binding agent.

Description

Gel electrolyte for sealed lead acid batteries {THE GEL ELECTROLYTE FOR A SEALED LEAD STORAGE BATTERY}

The present invention relates to a gel electrolyte for a sealed lead acid battery, and more particularly to a gel electrolyte for a sealed lead acid battery containing a binder that stabilizes the three-dimensional structure of the gel and facilitates the filling into the battery.

The electrolyte of a large industrial hermetic lead acid battery that is commonly used includes an electrolyte in which a sulfuric acid electrolyte is impregnated with an absorptive glass mat (hereinafter referred to as AGM), or a gel electrolyte in which silica is dispersed in a sulfuric acid electrolyte.

The microporous AGM absorbs the electrolyte by capillary force to lower the fluidity of the electrolyte, thereby preventing layer separation, and the gel electrolyte disperses the fine silica powder in sulfuric acid electrolyte to solidify it so that the hydroxyl groups on the surface of the silica powder are hydrogen They combine to form a three-dimensional structure and form hydrogen bonds with sulfuric acid to effectively prevent layer separation.

In general, AGM is used more than gel electrolyte because of its simple process and relatively good performance, but when used for a long time, specific gravity difference occurs, and especially in large batteries, the specific gravity difference rate due to gravity is high. It is not suitable for the communication battery or UPS (Uninterrupted Power Supply) battery using the above.

Therefore, in large industrial batteries or applications requiring long life, gel electrolytes which are excellent in inhibiting layer separation and may contain a relatively large amount of sulfuric acid are mainly used.

In general, the gel electrolyte used in lead acid batteries is a mixture of sulfuric acid and silica, which maintains a low viscosity similar to the liquid state at the beginning of mixing, but forms a three-dimensional network structure by hydrogen bonding and gradually increases in viscosity as time passes. To gel. However, the gel electrolyte formed by mixing only silica and sulfuric acid is a shrinkage phenomenon of the gel during the solidification process, and many cracks and pores occur with phase separation such as water generation, and the gel structure collapses into a liquid state, which causes the gel to lose its properties. do. Therefore, a high molecular substance containing a large amount of oxygen or nitrogen capable of strong hydrogen bonding with the hydroxyl group on the silica surface is added as a binder.

The binder has two roles, firstly, to inhibit phase separation so that no phase other than the gel phase is present in the electrolyte, and secondly, to increase the mechanical stability of the gel while reducing the amount of silica used by enhancing the bonding strength between the silica. will be. In general, the larger the molecular weight of the binder, the more oxygen or nitrogen capable of bonding with hydroxyl groups on the silica surface, thus forming a more stable three-dimensional network structure.

Conventionally, polyethylene glycol (PEG) (US Pat. No. 3,776,779), polyacrylamide (PAA) (US Pat. No. 4,937,156), pectin (US Pat. Nos. 3,271,199 and 3,328,208) and the like are mainly used as binders. These binders contain a large amount of nitrogen or oxygen groups to hydrogen bond between silica and silica to form a three-dimensional stable gel structure.

However, the binder was expensive and solidified with a sharp increase in the concentration of the gel electrolyte immediately after the binder was added, making it impossible to uniformly inject into the cell in a short time. Therefore, the injection of this non-uniform gel electrolyte deteriorated the capacity of the battery and the battery life performance.

Accordingly, the present invention provides a gel electrolyte for a sealed lead acid battery containing a binder which allows the gel electrolyte to form a more stable three-dimensional network structure, and maintains a low viscosity for a relatively long time to facilitate injection into the battery. For the purpose of

FIG. 1 shows the results of viscosity changes over time of gel electrolytes containing 0.1 wt%, 0.2 wt% and 0.5 wt% starch, and gel electrolytes containing 0.1 wt% and 0.2 wt% PEG.

PEG means polyethylene glycol # 400 by Aldrich.

The present invention is a gel electrolyte characterized by containing starch as a binder in a gel electrolyte for sealed lead acid batteries.

Hereinafter, the present invention will be described in detail.

In general, when the binder is mixed with the gel electrolyte, a three-dimensional structure of the gel is formed within a short time, and the viscosity of the gel electrolyte is rapidly increased to prevent flow into the very narrow space between the electrodes filled in the precursor, so that complete and uniform filling is achieved. It becomes impossible. Therefore, after adding the binder, the gel electrolyte is stirred at a high speed (> 1,000 rpm) to collapse the three-dimensional structure of the gel electrolyte until the injection of the gel electrolyte, or else the binder is delayed as much as possible and the sulfuric acid is dissolved within 1 minute. Equipment should be provided to inject.

In order to solve this problem, it is necessary to select a binder having a property of maintaining a low viscosity for a relatively long time even after addition to the gel electrolyte.

Therefore, in the present invention, a binder composed of starch having a high molecular weight and containing a large amount of oxygen is preferable. The starch is a readily available starch, and also contains a large amount of hydroxyl groups to sufficiently hydrogen bond with the silica in the gel electrolyte to stabilize the gel electrolyte.

In addition, the present invention is a gel electrolyte containing 0.01 to 0.5% by weight of the starch relative to the weight of the gel electrolyte as a binder, preferably 0.1 to 0.2% by weight. The starch content in the gel electrolyte may vary depending on the molecular weight of the starch, but is preferably limited to the above range in order to maintain a low viscosity for a relatively long time while forming a stable three-dimensional network structure after the addition.

Hereinafter, the present invention will be described in detail with reference to the following examples, but is not limited thereto.

Example

Example 1

Silica and sulfuric acid with Deggusa Aerosil 200 having a particle surface area of 200 m ² / g were mixed at 2000 rpm or more to break down the mass structure of silica and have a uniform distribution of silica in sulfuric acid. When the three-dimensional structure of the silica collapsed by high speed agitation and became a liquid, 0.1 wt% of starch was added to prepare a gel electrolyte.

Example 2

It was prepared in the same manner as in Example 1 except that 0.2% by weight of starch was added.

Example 3

It was prepared in the same manner as in Example 1 except that 0.5% by weight of starch was added.

Comparative Example 1

Except for adding 0.1% by weight of polyethylene glycol # 400 (hereinafter referred to as PEG) manufactured by Aldrich, it was prepared in the same manner as in Example 1.

Comparative Example 2

Except that the PEG 0.2% by weight was prepared in the same manner as in Example 1.

Test Example

Examples 1 to 3, Comparative Examples 1 and 2 of the gel electrolyte and water using a spindle-type viscosity meter of Brookfield, Inc., the spindle inserted in the gel electrolyte or water at a temperature of 24 ° to 26 ° C The viscosity was measured while rotating at 50 rpm. 1 to 3, Comparative Examples 1 and 2 and the results of the viscosity measurement with time of water are shown in FIG.

As shown in FIG. 1, Example 1 exhibited a viscosity very similar to that of water, and the liquid phase was maintained. In Example 2, the viscosity was maintained until 360 seconds after starch was added, and the viscosity gradually increased. It was. In comparison, in the case of using the PEG of Comparative Example 1 and Comparative Example 2, the solidifying machine started to proceed immediately after the injection of the electrolytic cell. Example 3 using 0.5% by weight of starch showed a sharp increase in viscosity after 120 seconds after addition of starch, but a viscosity increase was less than that of Comparative Example 2 using 0.2% by weight of PEG.

In conclusion, even when a small amount of starch is added as a binder in the preparation of the gel electrolyte, the rate of viscosity change over time is slower than other binders, and thus the gel can be easily injected into the battery because the viscosity can be maintained for a relatively long time. In addition, it can be seen that the viscosity change rate is faster than the case where no binder is added at all to form a more stable three-dimensional network structure.

The gel electrolyte for sealed lead acid batteries containing starch according to the present invention has four major advantages. First, it is possible to form a more stable three-dimensional network structure than a gel consisting of only silica and sulfuric acid. Second, phase separation can be prevented by forming a more stable three-dimensional network structure. Third, it maintains a low viscosity for a relatively long time compared to other binders, which facilitates gel mixing and injection. Fourth, starch is easy to obtain and inexpensive.

Due to the above advantages, it is possible to simplify the manufacturing process of the lead acid battery using the gel electrolyte, and to stabilize the structure of the gel electrolyte, thereby improving the life performance of the battery.

Claims (2)

A gel electrolyte for sealed lead acid batteries, wherein the gel electrolyte contains starch as a binder. The gel electrolyte according to claim 1, wherein the content of the binder is 0.01% by weight to 0.5% by weight based on the weight of the gel electrolyte.