KR20030049115A - Method of manufacturing inorganic gel electrolyte for lead-acid battery by adding of binding agent and the electrolyte - Google Patents

Abstract

PURPOSE: Provided is a binder-added inorganic gel electrolyte for a sealed type lead storage battery, which is excellent in structural strength, charging capacity, and lifetime property. CONSTITUTION: The binder-added inorganic gel electrolyte is produced by mixing and dispersing silica in sulfuric acid solution at more than 2000rpm and then adding 0.001-1%(based on the weight of the electrolyte) of polyvinyl alcohol as a binder to the silica-sulfuric acid solution dispersion, wherein the polyvinyl alcohol has a molecular weight of more than 10000.

Description

Method of manufacturing inorganic gel electrolyte for lead acid battery with binder added and its electrolyte {Method of manufacturing inorganic gel electrolyte for lead-acid battery by adding of binding agent and the electrolyte}

TECHNICAL FIELD The present invention relates to a method for producing an electrolyte that can ionize when generated as an aqueous solution, to generate ions, and to lead an electric current, in particular, an inorganic gel electrolyte for lead acid battery containing a binder and an electrolyte thereof.

A lead acid battery is a battery that can be charged and discharged by oxidation and reduction of a positive electrode plate and a negative electrode plate made of lead and lead oxide in sulfuric acid as an electrolyte. Generally, the positive and negative plates of lead acid batteries are alternately arranged with separators separating the two plates. The spaces other than the plates and separators arranged in this way are filled with sulfuric acid as an electrolyte.

Lead acid battery is a stable technology with a long history of use, and has the advantages of low price, large capacity and easy recycling. However, when lead-acid batteries are used for charging and discharging, periodic replenishment is required, and there is a problem of corrosion and sulfation of the electrode plate due to the stratification phenomenon of sulfuric acid, which is an electrolyte, in large-scale, which leads to the life of the battery. This shortening creates a significant cost problem. In addition, there is a risk of explosion by the gas generated during overcharging.

As an alternative to this problem, sulfuric acid, which is an electrolyte, is included in an inorganic gel or an absorptive glass mat (AGM), but in the case of an absorbent glass mat, there is a problem of heat generation during use. Angry Particularly in the large industrial industry, gel electrolytes having excellent performance are mainly used because of less layering of sulfuric acid and relatively high sulfuric acid content.

Inorganic gels are generally prepared by gelling inorganic particles such as fumed silica or colloidal silicates in an aqueous sulfuric acid solution. In this case, the amount of gas generated is reduced by oxygen recombination, and the storage battery can be used in a sealed state, so that maintenance such as periodic addition of the electrolyte solution is unnecessary and the risk of explosion is small. In addition, since the stratification of the electrolyte is small, corrosion and sulfateization of the electrode plate are reduced, resulting in a longer lifetime. However, these inorganic gel electrolytes have problems such as low charge capacity life performance and gel cracking due to repeated charging and discharging, compared to sulfuric acid.

In general, it is known that the higher the proportion of inorganic particles in the inorganic gel, the higher the physical strength, such as reduced physical deformation such as cracking of the gel during use, while lowering the filling capacity.

In order to solve the problems of the inorganic gel electrolyte, a small amount of binder is used, which enhances the bond between the inorganic particles, thereby increasing the mechanical strength without lowering the filling capacity.

U.S. Patent No. 3,172,782 discloses a gel electrolyte comprising 3-10% by weight of silica.

U.S. Patent Nos. 3,271,199 and 3,328,208 disclose gels prepared by adding 0.3% by weight of pectin to 5-8% by weight of silica. Pectin also has the effect of inhibiting the oxidation of the cathode (US Pat. No. 3,271,199).

U.S. Patent No. 3,776,779 discloses a gel prepared by adding 0.0001 to 0.065% by weight of polyethylene glycol to 3 to 8.5% by weight of silica particles, wherein the molecular weight of polyethylene glycol used was 800 to 6000.

US Patent No. 4,937,156 and European Patent No. 325,672 disclose gels prepared by adding 0.1 to 1.0% by weight of polyacrylamide to 3-5% by weight of silica particles.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing an inorganic gel electrolyte for a lead acid battery, to which a binder added to have improved structural strength and an electrolyte thereof.

1 is a graph showing the storage modulus of the lead-acid inorganic gel electrolyte, (a) is a case prepared by adding polyvinyl alcohol having a molecular weight of 13,000 according to Examples 1 and 2 of the present invention, (b) is the present invention According to Example 3 was prepared by the addition of polyvinyl alcohol having a molecular weight of 124,000, (C) is a case where the proportion of silica according to Comparative Example 2 is 8% by weight and prepared without using an additive.

Figure 2 is a graph showing the electrical conductivity of the inorganic gel electrolyte for lead acid battery, (a) is a case prepared by adding polyvinyl alcohol having a molecular weight of 13,000 according to Example 1 of the present invention, (b) is According to Examples 1 and 2 was prepared by the addition of polyvinyl alcohol having a molecular weight of 124,000, (c) is a case in which the proportion of silica according to Comparative Example 2 is 8% by weight and prepared without using an additive.

A method for preparing an inorganic gel electrolyte for a lead acid battery containing a binder according to the present invention, which achieves the above object, is characterized in that polyvinyl alcohol having a molecular weight of 10,000 or more is added by 0.01 to 1% by weight of an electrolyte.

Since the binder plays a role of hydrogen bonding with the hydroxyl groups on the surface of the inorganic particles constituting the gel electrolyte to strengthen the bonding of the particles, the binder must include a functional group capable of hydrogen bonding. A binder containing an atom such as oxygen or nitrogen in a molecule is generally used for such a hydrogen bond.As the molecular weight of the binder increases, the number of inorganic particles that can form a bond in contact with the binder increases, so that a polymer binder is used a lot. .

For this reason, in the present invention, polyvinyl alcohol having a hydroxyl group per unit chain and having a relatively large number of hydroxyl groups compared to other additives was used as a binder.

However, binders of too high molecular weight may exceed the viscosity range of the gel suitable for the process, so it is necessary to use a binder in an appropriate range of molecular weights. In addition, when an excessively low molecular weight binder is used, the binder molecule may be adsorbed on the surface of a single particle rather than a plurality of inorganic particles, thereby increasing the dispersion stability between particles as opposed to the binding between particles.

Therefore, the molecular weight of the polyvinyl alcohol to be added is more than 10,000 is appropriate, in order to improve the structural strength of the desired level and the ease of the process, the addition amount is preferably 0.001 to 1% relative to the weight of the gel electrolyte.

On the other hand, since polyvinyl alcohol has a very low rate of dissolving in water at room temperature, the polyvinyl alcohol is dissolved in water at 80 ° C. before addition and then added to achieve uniform mixing in the gel electrolyte.

Hereinafter, the present invention has been described in detail with reference to Examples, but is not limited thereto.

Example 1

Aerosil 200 (Degussa), fumed silica, was mixed with an aqueous sulfuric acid solution at 2000 rpm or more to disperse the aggregated particles. At this time, the silica was mixed in a proportion of 6% by weight. A gel electrolyte was prepared by adding 0.1 wt% of polyvinyl alcohol having a molecular weight of 13,000 (aldrich) to the dispersion of silica-sulfuric acid solution thus mixed. Polyvinyl alcohol was previously prepared by dissolving in water at 80 ° C. and adding it.

Example 2

It was prepared in the same manner as in Example 1 except adding 0.2% by weight of polyvinyl alcohol.

Example 3

It was prepared in the same manner as in Example 1 except adding 0.05% by weight of polyvinyl alcohol having a molecular weight of 124,000.

Comparative Example 1

Aerosil 200, fumed silica, was mixed with an aqueous sulfuric acid solution at 2000 rpm or more to disperse the aggregated particles to prepare a gel electrolyte. At this time, the silica was mixed in a proportion of 6% by weight.

Comparative Example 2

It is the same as that of Comparative Example 1, except that the silica was mixed at a ratio of 8% by weight.

[Test Example]

In order to evaluate the structural strength of the gel electrolytes of Examples 1 to 3 and Comparative Examples 1 and 2, the storage modulus was measured at 25 ° C. through a dynamic oscillation test. Rheometrics ARES Fluid Rheometer was used for the measurement. The higher the storage modulus, the stronger the bond between the particles forming the gel electrolyte.

As a result of measuring the storage modulus, the gel electrolytes of Examples 1 to 3 showed higher storage modulus values than the gel electrolyte of Comparative Example 1 without adding polyvinyl alcohol, and the silica content was 2% by weight. The storage modulus of the gel electrolyte level was shown (FIG. 1). This means that the gel electrolyte added with polyvinyl alcohol has excellent structural strength equivalent to that of the gel electrolyte with no polyvinyl alcohol added and with a higher proportion of silica.

The electrical conductivity of the gel electrolyte of Examples 1 to 3 and Comparative Example 1 was measured. Frequency response analyzer was used for the measurement. The higher the electrical conductivity, the better the electrolyte of the battery.

2, the gel electrolytes of Examples 1 to 3 have higher electrical conductivity than the gel electrolyte of Comparative Example 2 without the addition of polyvinyl alcohol. (In Fig. 2, for ease of comparison, the electrical conductivity of sulfuric acid without silica was set to 100. Also, for reference, the electrical conductivity of a gel containing 8% silica was indicated by dotted lines.) In particular, Examples 1 and 3 gels containing the same amount of silica have an electrical conductivity almost equivalent to that of Comparative Example 1. This means that the polyelectrolyte added gel electrolyte has excellent structural strength equivalent to that of the polyelectrolyte without the addition of polyvinyl alcohol and a higher proportion of silica, but almost no change in electrical conductivity. In other words, the addition of a small amount of polyvinyl alcohol can achieve an improvement in structural strength without a decrease in electrical conductivity.

The gel electrolyte for a sealed lead acid battery manufactured by the present invention has an advantage of having structural strength superior to that of a polyelectrolyte-free gel electrolyte. As a result, even smaller proportions of silica make it possible to obtain the structural strength required as a gel electrolyte used in sealed lead acid batteries, thereby increasing the content of sulfuric acid corresponding thereto to achieve better charging capacity and longer life performance. .

Claims (5)

In preparing a gel electrolyte by mixing and dispersing silica in an aqueous solution of sulfuric acid, a binder is added to the mixed silica-sulfuric acid aqueous solution in which 0.001 to 1% of a molecular weight of 10,000 or more polyvinyl alcohol is added as a binder. A method for preparing an inorganic gel electrolyte for a lead acid battery. The method according to claim 1, wherein the binder is added at 2000 rpm or more. The method of claim 1, wherein the polyvinyl alcohol is dissolved in water and added. The method of claim 3, wherein the polyvinyl alcohol is dissolved after heating the water. An inorganic gel electrolyte for lead acid batteries, to which a binder prepared by the method of claim 1 is added.