JPH06349486A - Negative electrode plate for lead-acid battery - Google Patents

Abstract

PURPOSE:To improve charge acceptability and reduce the mass of a negative electrode current collector by setting the mass of the current collector except for the current collecting lug sections of the negative electrode current collector to a specific value or below against the negative electrode active material mass, and adding a conducting additive such as carbon having a specific value or above against the negative electrode active material mass into the negative electrode active material. CONSTITUTION:A negative electrode plate is constituted of a current collector and a negative electrode active material. The main negative electrode active material is spongy metal lead. The ratio of the negative electrode active material against the mass of the current collector except for the current collecting lug sections of the negative electrode current collector is set to 25% or below. Carbon of 0.5% or above against the negative electrode active material mass is added into the negative electrode active material. When a sealed lead-acid battery is manufactured with the negative electrode plate and a positive electrode plate thus formed, little lead sulfate is accumulated after a prescribed cycle test, and the charge acceptability is improved. The average grain size of the added carbon is preferably set to 100mum or below.

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 for a lead storage battery, and more particularly to an improvement of a thin negative electrode plate.

[0002]

2. Description of the Related Art In recent years, it has become an urgent development task to increase the energy density and improve the life performance of lead acid batteries which have been increasingly used in electric vehicles and the like. There is.

In order to increase the energy density of the lead storage battery, it is necessary to improve the discharge performance and reduce the mass of the lead storage battery. In order to improve the discharge performance, the thickness of the positive and negative electrode plates used in lead-acid batteries is reduced to increase the geometric surface area of the positive and negative electrode plates, and positive,
It is known that it is effective to improve the utilization rate of the negative electrode active material. Further, in order to reduce the mass of the storage battery, it is conceivable to reduce the mass of the portion of the storage battery component that does not contribute to power generation.

Here, the current collector should be the most lightweight, but if the mass of the current collector is reduced, the life performance deteriorates.
This is mainly due to the deterioration of the corrosion resistance of the positive electrode current collector, but at the same time, the life performance of the negative electrode plate also deteriorates due to the following reasons.

The negative electrode plate of a lead storage battery comprises a current collector and a negative electrode active material, and the negative electrode active material is spongy metallic lead. Therefore, the fully charged negative electrode plate can be discharged even if the negative electrode current collector has a very small mass because it has conductivity.

However, since lead sulfate, which is a discharge product of a negative electrode of a lead storage battery, does not have electrical conductivity, in order to charge the negative electrode plate after discharging, the entire negative electrode active material is charged through the negative electrode current collector to a potential of charging. Need to be applied. Here, when the mass of the negative electrode current collector is small, the current density of the negative electrode current collector is high, and only the portion close to the current collector can be charged, that is,
The phenomenon that lead sulfate accumulates on the negative electrode plate occurs.

This phenomenon becomes more remarkable as the negative electrode active material becomes thinner and the utilization rate of the negative electrode active material improves. As a result of studying this problem, the ratio of the mass of the negative electrode active material to the mass of the negative electrode current collector excluding the current collecting ears (hereinafter, referred to as current collector / active material amount ratio) is 0. It was found that the battery could not be charged when it was 25 or less.

[0008]

The present invention increases the conductivity of a negative electrode active material in a discharged state by increasing the amount of a conductive material such as carbon, which has been conventionally added to the negative electrode active material. As a result, it is possible to completely charge the negative electrode current collector even when the mass of the negative electrode current collector is reduced.

[0009]

[Function] The added conductive material such as carbon improves the conductivity of the negative electrode active material after discharging, improves the charge acceptability of the negative electrode active material, and does not impair the performance, and a large mass is conventionally required. The required mass of the negative electrode current collector can be reduced.

[0010]

Example: Five positive electrode plates having a thickness of 2.5 mm and a thickness of 1.0
Capacity of about 20 Ah / 3h by combining 6 mm negative plates
An R-2V sealed lead acid battery was manufactured. At this time, the current collector / active material amount ratio of the negative electrode plate was variously changed from 0.025 to 0.5. These negative electrode plates were filled with a negative electrode active material in which the amount of carbon added was changed in 0.1% increments with respect to the mass of the negative electrode active material. However, when the amount of carbon added exceeded 5% at this time, plastering during paste was not possible.

The results of investigating the amount of lead sulfate accumulated in the negative electrode active material by disassembling these sealed lead-acid batteries after three cycles of the capacity test are shown in FIG. The amount of carbon added is 0.4
It can be seen that the amount of lead sulfate accumulated sharply increases when the current collector / active material amount ratio becomes 0.25 or less when the ratio is less than%. However, when the amount of carbon added was 0.5% or more, lead sulfate hardly accumulated.

A life test was carried out using a part of these batteries. All the current collector / active material amount ratios of the batteries used in the life test were set to 0.25, and the addition amount of carbon in the negative electrode active material was set to three points of 0%, 0.2%, and 0.5%. The life test condition at this time was 0.1 CA after discharging for 3 hours at 0.25 CA.
The test was carried out in constant temperature water at 30 ° C. The result is shown in FIG. When the amount of carbon added was 0% and 0.2%, the capacity decreased early, but when it was 0.5%, the life performance was 300 cycles or more. The cause of the life at this time was the accumulation of lead sulfate in the negative electrode active material. Further, as a conductive additive other than carbon, polyaniline, carbon fiber and the like were also examined, but similar results were obtained.

Next, the average particle size of the added carbon was examined. At this time, the total amount of carbon added to the negative electrode active material was 0.5%. At this time, the average particle diameter of carbon was set to four points of 50, 100, 200 and 500 μm. FIG. 3 shows the results of disassembling these sealed lead acid batteries after 3 cycles of the capacity test and investigating the amount of lead sulfate accumulated in the negative electrode active material. Average particle size of carbon is 200μm
In the above cases, the amount of lead sulfate accumulated was considerably large, but when the average particle size was 100 μm or less, lead sulfate hardly accumulated.

[0014]

EFFECTS OF THE INVENTION In a negative electrode plate for a lead storage battery, when the mass of the current collector excluding the current collecting ears of the negative electrode current collector is 25% or less of the mass of the negative electrode active material, Improving the conductivity of the negative electrode active material after discharge and the charge acceptance of the negative electrode active material by adding 0.5% or more of a conductive additive such as carbon to the mass of the negative electrode active material, and impairing the performance. The mass of the negative electrode current collector, which has conventionally required a large mass, can be reduced, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the current collector / negative electrode active material amount ratio and the lead sulfate accumulation amount in the negative electrode active material.

FIG. 2 is a diagram showing the life performance when the amount of carbon added is changed.

FIG. 3 is a diagram showing the relationship between the current collector / negative electrode active material amount ratio and the lead sulfate accumulation amount in the negative electrode active material.

Claims (2)

[Claims] 1. The mass of the current collector excluding the current collecting ears of the negative electrode current collector is 25% or less with respect to the mass of the negative electrode active material, and the mass of the negative electrode active material is relative to the mass of the negative electrode active material. 0.5% or more of a conductive additive such as carbon is added to the negative electrode plate for a lead storage battery. 2. The negative electrode plate for a lead storage battery according to claim 1, wherein when the conductive additive is carbon, the average particle diameter of carbon is 100 μm or less.