JPH0450713B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention uses a negative electrode gas absorption method that controls the gas generated during charging to only oxygen gas, and eliminates this oxygen gas by causing a direct reaction with lead, which is a charging product of the negative electrode. This relates to sealed storage batteries. Conventional Structure and Problems This type of lead-acid battery is mainly used as an emergency power source for telephones, communication, operation, emergency lighting, memory backup, etc. The principles of sealing lead-acid batteries are shown in equations (1) and (2) below. Pb＋1/2O ₂ +H ₂ SO ₄ →PbSO ₄ +H ₂ O …(1) PbSO ₄ +2H ⁺ +2e→H ₂ SO ₄ +Pb …(2) When the positive electrode plate becomes fully charged, oxygen gas is generated from the positive electrode. . This oxygen gas is absorbed by lead, the negative electrode active material, and reacts with sulfuric acid, the electrolyte, to form lead sulfate (Equation (1)). The amount that this lead sulfate is charged and changes to lead (equation (2)) is balanced with the amount that lead absorbs oxygen gas and changes to lead sulfate (equation (1)), so it is necessary to seal the storage battery. fulfilled. The current flowing through the battery after full charge is primarily used to compensate for gas absorption reactions and self-discharge. Conventionally, when a constant voltage charging method is used for a long period of time, such as trickle charging or float charging, a phenomenon has been observed in which the electrolyte decreases over time and the charging current increases. This is thought to be due to an increase in the surface area of the negative electrode plate involved in the oxygen gas absorption reaction due to liquid reduction, and an increase in self-discharge due to an increase in the specific gravity of the electrolyte, which increases the charging current. In particular, the negative electrode plate (the negative electrode plate used on the outermost side of the electrode plate group) accounts for about 60% of the gas absorption, and is the main reason for the increase in charging current. An increase in charging current more than necessary promotes corrosion of the positive electrode grid and shortens battery life. A cross-sectional view of a conventional negative electrode plate is shown in FIG. 1, and both sides of the electrode plate are covered with an active substance 1 made of spongy lead, and oxygen gas is actively absorbed on both sides. In addition, the gas absorption ratio between the side of the negative electrode plate facing the positive electrode and the side facing the battery case wall or partition wall is approximately 1:3. It can be seen that the ratio of the gas absorption reaction on the partition wall side is high. In addition, in FIG. 1, 2 indicates a frame bone, and 3 indicates a middle bone. In a conventional sealed lead-acid battery of negative electrode absorption type in which a rib is provided inside the battery case, the surface of the negative end plate facing the battery case wall side or the partition wall side is entirely capable of absorbing gas. There are also negative electrode absorption type sealed lead-acid batteries that do not have ribs inside the battery case, and negative electrode absorption type sealed lead acid batteries that use a spacer such as synthetic resin between the negative electrode plate and the rib inside the battery case. However, it is impossible to finish the negative electrode plate surface like a mirror.
Non-uniform expansion and contraction of the negative electrode active material occurs during use. Therefore, there are many gaps between the battery case walls, partition walls, spacers, etc., and since this type of battery has a very small amount of liquid, the passage of gas is also active, and oxygen gas is absorbed. The amount also increases, and in fact gas absorption occurs over the entire surface, accelerating the increase in charge current. This increase in charging current has the problem of accelerating corrosion of the positive electrode grid and shortening battery life. Purpose of the Invention The present invention suppresses corrosion of the positive electrode grid when performing constant voltage charging for a long period of time, such as trickle charging or float charging, by suppressing the increase in charging current caused by the increase in the gas absorption area at the negative electrode. The purpose is to extend the life of storage batteries. Structure of the Invention That is, in order to achieve the above object, the present invention covers most or the entire surface of the negative electrode plate that does not face the positive electrode plate with lead or a lead alloy in order to suppress the oxygen gas absorption reaction at the negative electrode plate. It is characterized by covering the negative electrode active material with a film to prevent unnecessary supply of oxygen gas to the negative electrode active material. In addition, if the entire outer surface of the negative electrode plate, which is most likely to come into contact with oxygen gas, is covered with a lead or lead alloy film, the paste-like active material may fall off or peel off during manufacturing, so the film and lattice backbone may Through-holes are provided at the joints in areas that do not affect gas absorption, and the paste-like active materials in adjacent lattice sections are continuously bonded to prevent them from falling off or peeling off. DESCRIPTION OF EXAMPLES Hereinafter, details of the present invention will be explained with reference to examples. FIG. 2 shows the battery configuration in the example. A cover 5 is glued to the battery case 4 in the figure.
A safety valve 6 is provided in the recessed portion corresponding to each cell, and a cover 7 is adhered onto the recessed portion. The cover 7 is provided with a plurality of gas exhaust holes 8. The cover 5 is also provided with terminals 9, 9'. The electrode plate group 10 is housed in each cell chamber of the battery case, and ribs 11 are provided on the inner surface of the battery case (same as the partition wall).
A plurality of electrode plates are provided vertically to apply appropriate group pressure to the electrode plate group 10. The negative electrode plates 12 are located on both the left and right sides of each electrode plate group 10. In order to make the electrolyte non-fluid, methods such as impregnating the separator with the amount that can be impregnated with the electrolyte or gelling it are taken.
Furthermore, methods such as using a separator and a gelled electrolytic solution in combination are also adopted. Next, the grid used for the negative electrode plate will be explained with reference to FIGS. 3 and 4. The lattice shown in FIG. 3 consists of frame bones 2,
Lead or lead alloy film 1 covering the backbone 3 and one side of the grid
3 are integrally formed. This lattice may be manufactured by casting, forging, or the like. This negative electrode plate is easy to manufacture if it has a relatively low paste filling density, but as the paste filling density increases, the filling properties deteriorate, and cavities are formed and the paste often falls off. However, the effect of suppressing gas absorption reactions is large. For this reason, the grid shown in FIG. 3 was improved as shown in FIG. 4 as a grid for the negative end plate that can be filled with any paste filling density. This is membrane 13
A through hole 14 is provided at the joint between the backbone 3 and the backbone 3 to allow air to escape during paste filling, and to integrate the paste filled into adjacent lattice sections to prevent the paste from falling off during manufacturing. be. The through hole 14 may be provided only in either the longitudinal midrib shown in B or the lateral midrib shown in C, or of course may be provided in both. In addition, the ratio of the total area of the through holes to the surface area of one side of the negative electrode plate is determined from the relationship with the charging current as shown in Figure 5.
It is desirable to keep it below 30%. A 6V, 3Ah battery was used as the test battery, and the values at 20 months are shown. Using the negative end plate created in this way, 20
A battery with a time rate capacity of 12Ah was created and an accelerated life test using a trickle charge method was conducted. The configuration of the negative electrode plate is as shown in Fig. 3 and Fig. 4, and the total area of the through holes 14 is 10%, 20%, 30%, and 50% of the surface area of one side of the electrode plate.
Create each one, and the electrode plate group configuration is positive electrode plate 3.
There were four negative electrode plates. Trickle charging method accelerated life test
2.30V/cell, maximum charging current 500mA, temperature 40±5
It was carried out for 20 months at ℃. Figure 6 shows the change in charging current and capacity over time. Changes gradually appeared after 6 months, and by the 20th month, it was confirmed that the product of the present invention was sufficiently effective. In Fig. 6, a is a conventional product without a membrane, b is a product with a pore area ratio of 50% according to the present invention, and c is a product with a pore area ratio of 50%.
indicates 30%, d indicates 20%, e indicates 10%, and f indicates 0%. In addition, g indicates the capacitance change of the conventional product a, and h indicates the capacitance change of the present invention products b to f as a range. As described above, it can be seen that by using the negative electrode plate of the present invention, it is possible to suppress the increase in charging current and extend the life. The following table shows the relationship between the charge current increase rate and capacity after 18 months of use.

[Table] All batteries are shown as the average value of 10 batteries, the current increase rate is determined from the 18th month charging current/initial charging current, and the pore area ratio is the total pore area/electrode plate piece. It was calculated by multiplying the area by 100. Effects of the Invention As described above, the present invention suppresses the oxygen gas absorption reaction by forming a lead or lead alloy film on one side of the negative electrode plate that does not face the positive electrode plate, so that it is possible to suppress an increase in the charging current. Lifespan can be extended. Furthermore, if a through hole is provided in a part of the joint between the lead or lead alloy membrane and the lattice frame, there is no need for a spacer etc. to be interposed between the battery case wall or partition wall, and it is possible to connect the ribbed battery case. It is easy to insert the electrode plate group, and the gel electrolyte can also be quickly injected. Further, there is an advantage that the paste-like active materials in adjacent lattice sections can be continuously connected by the through holes, and it is also possible to prevent the active materials from falling off or peeling off.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional negative end plate, Figure 2 is a sectional view showing a conventional negative end plate;
The figure is a partially cutaway perspective view of a sealed lead-acid battery according to an embodiment of the present invention, FIG. 3A is a front view of the negative end plate of the lead-acid battery of the present invention, and FIG. -Cross-sectional view along line B', Figure 4A
is an explanatory diagram of the negative end plate filled with paste-like active material, B is a cross-sectional view along the C-C' line in A,
C is a cross-sectional view taken along the line D-D' in A, FIG. 5 is a diagram showing the relationship between the ratio of the total area of the through holes to the area of the negative electrode plate and the charging current, and FIG. 6 is a diagram showing trickle charging. FIG. 3 is a diagram showing the relationship between capacity and charging current in an accelerated life test of the method. 2...Frame bone, 3...Middle bone, 10...Pole plate group, 1
1...Rib, 12...Negative end plate, 13...Lead or lead alloy film, 14...Through hole.

Claims (1)

[Scope of Claims] 1. A sealed lead-acid battery in which the entire surface of one side of the negative end plate in the electrode plate group that does not face the positive electrode plate is covered with a film of lead or lead alloy. 2. The sealed lead-acid battery according to claim 1, wherein the lead or lead alloy film is integrally formed with the grid. 3 Sealed lead-acid batteries in which 70% or more of the area of the negative end plate in the electrode plate group, on one side not facing the positive electrode plate, is covered with a lead or lead alloy film, and the remaining 30% or less area is provided with a through hole. . 4. The sealed lead acid battery according to claim 3, wherein the lead or lead alloy film is formed integrally with the grid.