JPH0837008A - Paste type lead acid battery - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a paste-type lead acid battery having excellent initial performance and life performance. [Structure] A paste-type lead storage battery, wherein anisotropic graphite having a thickness of 5 to 80 µm is added to a positive electrode active material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lead type lead acid battery.

[0002]

2. Description of the Related Art Generally, lead-acid batteries often have a long life due to deterioration of the positive electrode plate. As a method for improving the life performance, there is a method of increasing the thickness of the positive electrode plate or increasing the density of the positive electrode active material. is there. However, a lead storage battery using such a positive electrode plate has inferior initial performance. On the other hand, if the positive electrode active material density is reduced to secure sufficient initial performance, it will have a short life. It was extremely difficult to obtain a paste type lead acid battery with good performance.

Therefore, in JP-B-63-57912, JP-A-58-123659, JP-A-61-176062 and the like, anisotropic graphite is added to a positive electrode plate having a large electrode plate thickness and a high active material density. A method has been proposed in which the initial performance is improved and the life performance is maintained as it is.

Graphite is a layered material in which planes of hexagonal netting of carbon atoms are stacked. The layers are strongly bound to each other by covalent bonds, while the planes are bound by van der Waals' weak force. It's just This is why graphite exhibits anisotropy (physical properties differ between the direction along the plane of the layer and the direction perpendicular to the plane of the layer), and various substances easily penetrate into the layers to form graphite intercalation compounds. Is.

As one of such graphite intercalation compounds, there is a graphite acid sulfate intercalation compound having hydrogen sulfate ions and sulfuric acid molecules as intercalating substances. This is obtained by chemically oxidizing highly anisotropic graphite in sulfuric acid using an oxidizing agent or electrochemically oxidizing it in sulfuric acid (anodic oxidation). At this time, the layer planes stacked at intervals of 3.35 angstroms spread to 7.98 angstroms, and the graphite expanded.

[0006] Here, in the case of graphite or isotropic graphite in which the crystal layer structure is not sufficiently developed, the expansion direction is not constant, so that it is damaged as the intercalation compound is generated and eventually collapses. On the other hand, graphite having a highly anisotropic layer structure expands only in a certain direction, and a stable graphite acid sulfate intercalation compound is obtained. Therefore, if a positive electrode plate in which graphite having a large anisotropy is added to the positive electrode active material is used,
An increase in the porosity of the active material can be expected accordingly.

In order to obtain the above-mentioned effects, it is necessary to use anisotropic graphite having a sufficiently large particle size.
It has been confirmed that those having a thickness of about 50 to 1200 μm are good. However, even if anisotropic graphite having these particle sizes is used, a sufficient effect may not be obtained.

Generally, the anisotropic graphite having the above grain size is not commercially available as a synthetic product, and the commercially available products mainly as natural flake graphite are used as they are or 2000
It is used after heat treatment at about ℃ to increase the anisotropy. These producing countries include China, Ukraine, Brazil, Madagascar, etc., but their characteristics seem to differ depending on the producing country and the vein.

[0009]

The present invention solves the above problems and is characterized in that anisotropic graphite having a thickness of 5 to 80 μm is added to the positive electrode active material, which results in excellent performance. The present invention provides a paste type lead storage battery having the same.

[0010]

EXAMPLES The present invention will be described below based on examples.

Commercially available anisotropic graphite has a particle size of 150 to 1200.
After classifying to μm, stratification according to thickness is performed, and Table 1
Anisotropic graphite having a thickness shown in was obtained. The thickness of anisotropic graphite is the thickness in the C-axis direction. 1 wt.% Of the above anisotropic graphite was added to ordinary lead powder having an oxidation degree of 75% and the balance metallic lead.
% Added. Then, the above mixed lead powder was kneaded with dilute sulfuric acid by a known method to prepare a positive electrode paste having a paste density of about 4.3 g / cm ³ . This paste was filled in a lead alloy grid with a thickness of 3 mm, aged, and then combined with a negative electrode plate having a sufficiently large capacity to give a nominal capacity of 90 Ah (5 hour rate).
The battery of was produced. A separator with a glass mat is used as a separator, and the glass mat is brought into contact with the positive electrode plate,
The degree of compression of the electrode plate group was set to 40 kg / dm ² . The prepared battery was subjected to battery case formation to obtain a lead storage battery having an electrolyte specific gravity of 1.280.

[0012]

[Table 1]

Table 2 shows the initial performance and positive electrode active material characteristics of the battery. The initial capacity tended to increase as the thickness of the anisotropic graphite increased, but the discharge capacity of the battery (No. 1) using anisotropic graphite having a thickness of less than 5 μm was remarkably small. Since the amount of graphite remaining in the positive electrode active material and the pore volume of the positive electrode active material after forming the battery case of this battery are significantly smaller than the others, anisotropic graphite having a thickness of less than 5 μm disappears due to anodization. It was found that the expansion effect of the active material due to the formation of the graphite acid sulfate intercalation compound was small.

[0014]

[Table 2]

The results of subjecting the above battery to a charge / discharge cycle life test are shown in FIG. The life test condition is discharge 22.
5A × 3h, charging 16.2A × 5h, temperature 30 ° C. in water tank. As a result of this test, it was found that when anisotropic graphite having a thickness of 80 μm or more was used (No. 6), the life performance was remarkably reduced. The softening of the positive electrode active material of this battery is remarkable,
It is considered that when anisotropic graphite having too large a thickness is used, the volume increase when it becomes a graphite acid sulfate intercalation compound is too large, and the bond between the active material particles is impaired, and the capacity is reduced early.

From the above, it was found that the optimum thickness of anisotropic graphite to be added to the positive electrode active material is 5 to 80 μm.

[0017]

As described above in the examples, the lead-acid battery according to the present invention is excellent in initial performance and life performance,
Its industrial value is enormous.

[Brief description of drawings]

FIG. 1 is a diagram comparing charge / discharge cycle life performance.

Claims (1)

[Claims] 1. A paste-type lead-acid battery, wherein anisotropic graphite having a thickness of 5 to 80 μm is added to the positive electrode active material.