JPH09147841A - Negative electrode plate for lead acid battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode plate for a lead acid battery and its manufacturing method wherein a sulfation phenomenon is hard to occur. SOLUTION: This negative electrode plate for the lead acid battery is such that an active material paste, which comprizes lead powder particles 3 wherein a layer composed of carbon particles or graphite particles 2 and of liquid glass is attached to the surfaces of a group of active material particles into which a plurality of active material particles 1 are aggregated, is filled in a current collecting body. A manufacturing method therefor is such that what is obtained by suspending the carbon particles or the graphite particles 2 in the water glass solution is kneaded together with the lead powder 3 added thereto and then dried, resulting in obtaining powder. An active material paste is made by kneading the powder together with dilute sulfuric acid added thereto and the paste is filled in the current collecting body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode plate used in a lead storage battery used in the fields of communication, emergency power supply, portable equipment and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A conventional negative electrode plate for a lead storage battery is prepared by adding lignin to metallic lead particles (lead powder) to prepare an active material paste.
It is prepared by filling a current collector with this paste. If the lead storage battery prepared using the negative electrode plate for lead storage battery is left for a long period of time, the dissolution and precipitation of lead sulfate is repeated by a thermal cycle, and a lead sulfate crystal having no conductivity gradually grows. Finally, a sulfation phenomenon occurs where the battery cannot be charged. This phenomenon is especially common in sealed lead-acid batteries,
It is a cause of short life. As a countermeasure against this, conventionally, a carbon powder is mixed with an active material to produce a negative electrode plate.
However, the lead-acid battery using such a negative electrode plate gradually loses its effect as charging and discharging are repeated.
The short life due to the sulfation phenomenon could not be prevented.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a negative electrode plate for a lead storage battery in which sulfation phenomenon hardly occurs and a method for manufacturing the same. is there.

[0004]

In order to achieve the above object, the present invention is to bind a film of carbon or graphite particles having excellent conductivity to the surface of an active material particle group with water glass. The particle size of the carbon or graphite particles is preferably 0.3 to 1.0 μm. In addition, the method of the present invention is a method in which lead powder is added to a product obtained by suspending carbon particles or graphite particles in a water glass solution, kneaded, and dried to obtain a powder, and then dilute sulfuric acid is added to the powder. It is characterized by kneading and kneading to prepare an active material paste, and then filling the current collector with the paste.

[0005]

As shown in FIG. 2, the lead powder particles 3 of the conventional active material paste to which the carbon or graphite powder is added have the carbon or graphite particles 2 mechanically formed in the active material particle group in which a plurality of active material particles 1 are aggregated. However, some of the particles 2 did not come into contact with the active material particle group. However, in the active material paste of the present invention, as shown in FIG. 1, since the carbon or graphite particles 2 are bound to the active material particle group by water glass, the discharge reaction on the binding surface is unlikely to occur, and Suppresses the coarsening of lead sulfate crystals. Further, even if the crystal of lead sulfate is coarsened, the carbon or graphite particles 2 are taken into the crystal, so that the conductivity is maintained.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (Embodiment 1) Carbon particles having an average particle diameter of 0.3 [mu] m are added to a water glass solution to prepare a suspension containing 20 to 40% of solid content, and the suspension has carbon particles based on lead powder.
It was mixed with lead powder so as to contain 0 mass% and dried. The drying was performed at 200 ° C., which is higher than usual, for 1 hour in order to ensure the solidification of the binder water glass. Dried lead powder was made into powder, and water and sulfuric acid were added thereto by a conventional means and kneaded to obtain an active material paste. This paste was filled in a current collector, and after aging and drying steps, chemical conversion was carried out by a usual method to produce a negative electrode plate.

In the negative electrode plate thus obtained, as shown in FIG. 1, carbon particles 2 are attached to the surface of the secondary particle group in which a plurality of active material particles 1 are aggregated. Since the carbon particles 2 form a kind of network structure by the binder, even if the lead sulfate crystal particles become coarse due to the dissolution and precipitation due to the thermal cycle, the network is not easily broken and therefore the conductivity is not easily lost. .

(Embodiments 2 and 3) Average particle size 1.0
And negative electrode plates of Embodiments 2 and 3 were produced in the same manner as in Embodiment 1, except that carbon particles of 5.0 μm and 5.0 μm were added to the water glass. Next, the batteries A to C were assembled using the negative electrode plates of Embodiments 1 to 3, a discharge capacity test was carried out, and the ratio of lead sulfate in the active material after discharge and the discharge time were investigated. The test condition is ambient temperature 50
C., a low rate discharge of 1/128 C (C is the value of the rated capacity for 10 hours) is performed until the cutoff voltage reaches 0 V, and the proportion of lead sulfate is investigated. ．
The battery was charged until the amount of electricity corresponded to 5 times, and then a discharge capacity test was performed at a rate of 5 hours, and each time until the final voltage reached 1.7 V was measured. Table 1 shows the results.

(Embodiments 4 to 6) Average particle diameter 0.3,
Negative electrode plates of Embodiments 4 to 6 were produced in the same manner as in Embodiment 1 except that graphite particles of 1 and 5 μm were added to water glass. Next, Batteries D to F were assembled using the negative electrode plates of Embodiments 4 to 6, the same discharge capacity test as Batteries A to C was performed, and the ratio of lead sulfate and the discharge time were investigated. Table 1 shows the results.

(Conventional embodiment) Carbon particles having an average particle diameter of 0.3 μm were added to 2.0 mass% of lead powder and mixed, and then water and diluted sulfuric acid were added and kneaded to prepare an active material paste. Then, this paste was filled in a current collector similar to that of Embodiment 1 to fabricate a negative electrode plate having the same structure as the conventional one. Next, using this negative electrode plate, a battery G similar to that of Embodiment 1 was assembled, a discharge test similar to batteries A to F was performed, and the proportion of lead sulfate and the discharge time were investigated. Table 1 shows the results.

[0011]

[Table 1]

It can be seen from Table 1 that the product of the present invention has a smaller proportion of lead sulfate than the conventional product and is excellent in discharge capacity. Therefore, according to the present invention, the sulfation phenomenon is less likely to occur and the charge recovery performance is superior to the conventional products.

When the average particle size of the carbon or graphite according to the present invention is less than 0.3 μm, the retention of sulfuric acid is deteriorated, the fluidity of the paste is lowered, and the filling becomes difficult. Alternatively, if graphite cannot be added and the average particle size is larger than 1.0 μm, the discharge capacity becomes substantially the same as that of the conventional product, so the average particle size is preferably 0.3 to 1.0 μm. Further, the present invention is not limited to the embodiment, and the addition ratio and the average particle diameter can be variously changed depending on the application of the battery.

[0014]

As described above, according to the present invention, (1) it is possible to prevent the crystal of lead sulfate having conductivity from being coarsened even by repeated dissolution and precipitation of lead sulfate, and to prevent the sulfation phenomenon. The short life of lead acid batteries can be prevented. (2) Further, even if lead sulfate coarsens, the coarse lead sulfate is taken into the fine network of the active material and the carbon or graphite layer, so that the electrical conductivity of the active material layer is maintained even after discharge, and lead The charge acceptance of the storage battery is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic view of lead powder particles according to the present invention.

FIG. 2 is a schematic view of a conventional lead powder particle.

[Explanation of symbols]

 1 Active material particles 2 Carbon or graphite particles 3 Lead powder particles

Claims (3)

[Claims] 1. Lead powder particles (3) having a layer of carbon particles or graphite particles (2) and water glass attached to the surface of an active material particle group in which a plurality of active material particles (1) are aggregated. A negative electrode plate for a lead storage battery, characterized in that a current collector is filled with an active material paste 2. The negative electrode plate for a lead storage battery according to claim 1, wherein the carbon particles or the graphite particles have a particle diameter of 0.3 to 1.0 μm. 3. Lead powder is added to a product obtained by suspending carbon particles or graphite particles in a water glass solution and kneaded, and then dried to obtain a powder. Then, dilute sulfuric acid is added to the powder and kneaded. A method for producing a negative electrode plate for a lead storage battery, which comprises: producing an active material paste by filling the current collector with the paste.