JPH0531270B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a maintenance-free lead-acid battery that is capable of absorbing oxygen gas generated in the positive electrode plate in the negative electrode plate despite having a sufficient amount of flowing electrolyte, and does not require special expensive parts. The purpose of this project is to provide a maintenance-free lead-acid battery that has high performance, long life, and is extremely inexpensive without adding any additional components. There have been many proposals regarding maintenance-free lead batteries. A typical example is the use of the so-called oxygen cycle, in which the electrolyte volume is made to be the same as or less than the pore volume of the electrode group to make it non-fluid, and the oxygen gas generated from the positive electrode plate is recombined with the negative electrode plate at the end of charging. There are some that are made airtight by doing this. A similar technique is one in which the electrolyte is made into a colloid and hermetically sealed. These sealed lead batteries do not have a flowing electrolyte, so there is no leakage of electrolyte, so lead batteries can be used in any position, and their gas absorption efficiency is high, making them completely maintenance-free lead batteries. You can say that. However, in these types of lead batteries, the amount of liquid injected is limited so that the flowing electrolyte is exhausted, so the amount of electrolyte is smaller than the amount of active material in the positive and negative electrode plates, and the battery capacity is limited by this amount. Limited by the amount of sulfuric acid in the electrolyte. In addition, the electrolyte may evaporate during use, oxygen gas generated at the end of charging may escape to the outside, or air may enter the battery from the outside and the oxygen gas in the air may react with the negative electrode plate, causing the negative electrode plate to A valve is required to prevent self-discharge. Furthermore, special measures are required for the terminal section to improve leakage resistance. At the same time, the battery case is required to have sufficient internal pressure resistance to withstand the opening pressure of the valve, so the material for the battery case is limited and the wall thickness of the battery case must be thick. For these reasons, it is extremely difficult to apply this method to large-capacity lead-acid batteries having large end-side surface areas. In order to compensate for the shortcoming of this electrolyte being small,
For example, as shown in U.S. Pat. No. 4,119,772, a structure in which an absorbent material for retaining electrolyte is placed around the electrode group has been proposed, but even with this structure, a valve is still required. There is. By the way, the present inventors have conducted repeated research on a method of applying a separator formed into a sheet shape mainly made of glass fibers having an average fiber diameter of 1 μm or less, as disclosed in Japanese Patent Publication No. 5813/1983. As a result, this separator can be used not only for conventional sealed lead batteries with a non-fluidized electrolyte, but also for lead batteries that have a sufficient amount of fluid electrolyte under certain conditions. It has been found that the oxygen gas generated from the separator moves toward the negative electrode plate in the separator without escaping to the upper part of the electrode group, and can be recombined by the negative electrode plate. This is because the separator is flexible and has a lot of fluff, so it adheres extremely closely to the surface of the electrode plate, and the pores on it are small, so there is a large resistance for oxygen gas to escape to the top of the electrode group. Rather, it is thought that this is because it moves obliquely in the thickness direction and reaches the negative electrode plate. In order to confirm the above phenomenon, we studied gas absorption in the presence of a flowing electrolyte and found that such gas absorption occurs when the following conditions are met. a) The separator must have enough flexibility and compressibility to come into close contact with the positive and negative electrode plates without leaving large gaps between itself and the irregularities of the active material on the surfaces of the positive and negative electrode plates. (b) The substantial maximum pore diameter of the separator itself is larger than the substantial maximum pore diameter of the void on the surface that is in close contact with the positive and negative electrode plates. c The pore diameter of the separator itself is small. That is, the maximum pore diameter of the material is 100μ or less, more preferably 40μ or less. By meeting the above conditions, the oxygen gas generated at the positive electrode plate is moved in the thickness direction of the separator and reaches the negative electrode plate, rather than escaping from the interface between the separator and the positive electrode plate to the upper part of the electrode group. be able to. Among the separators used in the above research, the reinforced fiber separator (JIS C2312) has no flexibility and is too rigid, so oxygen gas escapes outside the electrode group through the gap between the positive electrode plate and the separator, causing gas absorption. There isn't. The same result can be obtained even if a separator such as a microporous rubber separator or Daramitsu (trade name: manufactured by WR Grace) is used. On the other hand, when a sheet made of glass fiber with an average fiber diameter of 19μ, which has been conventionally used as a glass mat for lead-acid batteries, is used as a separator, the maximum pore diameter is 500μ.
The holes are so coarse that even if they can be brought into close contact with the surfaces of the positive and negative electrode plates, oxygen gas will escape to the upper part of the electrode group through the coarse holes, so that no gas absorption will take place. Furthermore, if the pore diameter is large, the oxygen gas bubbles themselves become large, which causes electrical resistance, and the discharge characteristics of the battery are also unfavorable. On the other hand, a sheet formed mainly of glass fibers with a fiber diameter of 1 μm or less, as shown in Japanese Patent Publication No. 55-5813, was able to absorb the gas described above. In addition, as described in U.S. Pat. No. 4,233,379, 30 to 80% pearlite and
It consists of 20-70% glass fiber, the particle size of pearlite is 3-100μ, and the fiber diameter of glass fiber is 3-100μ.
0.3 to 1.0 μ, as shown in Japanese Patent Publication No. 57-500040, 15 to 75% pearlite and 20
It consists of ~70% glass fiber and 5~20% acid-insoluble thermoplastic fiber, and the pearlite particle size is 3~3.
100μ and the fiber diameter of the glass fiber is 0.3 to 1.0μ, fibrillar synthetic fibers with a freeness of 350 c.c. or less, as shown in Japanese Patent Application Laid-Open No. 56-99968.
90% or more and 1m ² /g or more (fiber diameter approximately 2μ or less)
Paper made by mixing 10% or less of glass fiber with a specific surface area of
WO81/03397 Publication (Special Publication No. 57-500627)
Acicular acid-resistant inorganic material with a diameter of 0.1 to 5.5μ and a specific gravity greater than 2.46 g/cc, as shown in 10
~90% glass fiber with a fiber diameter of 10μ or less and a synthetic fiber binder of 10% or less can be used. Furthermore, as a result of further research by the present inventors, it has been found that in order to further improve the gas absorption rate in such lead batteries, it is better to provide through holes in the separator in its thickness direction. That is, by providing the through holes, the oxygen gas generated in the positive electrode plate moves through the through holes in the thickness direction and reaches the negative electrode plate more easily than through the separator and escapes to the upper part. However, when a separator provided with such a through hole is used, there is a risk of a short circuit between the positive and negative electrode plates. The present invention overcomes this problem by allowing a sufficiently flowing electrolyte to exist up to the top of the pole group,
In a lead-acid battery in which the negative electrode plate has an oxygen gas absorption function, a sheet-shaped material mainly made of glass fiber with a fiber diameter of 1 μm or less is used, and a pore size larger than the maximum diameter of the material and with a diameter of 30 to 2500 μm is added to the material. In addition to providing a through hole, a separator is formed by stacking a plurality of sheets with the through holes shifted in the material, and the separator is placed between the positive and negative electrode plates so as to be in close contact with the positive and negative electrode plates. It is something to do. The present invention will be explained below by means of examples and tests conducted using the examples. Comparative example A grid made of Pb-Ca alloy with a width of 103 mm and a height of 113 mm was used, and the thickness was 1.8 mm according to the conventional processing method.
A positive electrode plate with a thickness of 1.4 mm and a negative electrode plate with a thickness of 1.4 mm were prepared.
It consists of 80% by weight of glass fibers with an average fiber diameter of 0.5μ and 20% by weight of glass fibers with an average fiber diameter of 13μ, and the dimensions are 133mm in width, 240mm in length, and 0.5mm in thickness under a load of 20Kg/ ^dm2 . Two sheets of a certain material were stacked together to form a separator, the separator was bent into a U-shape, and a positive electrode plate was sandwiched inside the separator. The four positive electrode plates and five negative electrode plates sandwiched between these separators are stacked, the gap between the positive and negative electrode plates is adjusted to 1 mm, and a strap connecting the ears and a pole column rising from the strap are formed to form a pole group. Created. The electrode group was housed in each of six cells without a saddle in a battery case made of polyolefin, and the cells were connected in accordance with a conventional method, and then a battery case lid made of polyolefin was joined to the battery case by heat welding. The pole was protruded from the through hole of the battery case lid to seal the gap. Next, inject an electrolytic solution consisting of sulfuric acid with a specific gravity of 1.30d to a height that sufficiently immerses the electrode group, and tighten the exhaust plug with an exhaust port.
NS40Z type lead battery A was obtained. A partially cutaway front view of this is shown in FIG. In the drawing, 1 is a positive electrode plate, 2 is a negative electrode plate, 3 is a separator, and 4 and 5 are respective separator materials. Also, 6 is a strap, 7 is a pole, 8 is a battery case,
Reference numeral 9 indicates an inter-cell connection portion, 10 indicates a battery case lid, 11 indicates an electrolytic solution, 12 indicates an exhaust plug, and 13 indicates an exhaust port. This lead battery A and the NS40Z type lead battery B, which uses a grid made of a conventional Pb-Ca alloy and an embossed Umicron separator (our product name)
A comparative test was conducted. This lead battery B has an electrode group formed by bending the Yumicron separator into a U-shape, sandwiching a negative electrode plate in between, and overlapping this and a positive electrode plate, and also has an electrode group formed by overlapping the positive electrode plate with the negative electrode plate sandwiched between the Umicron separators, and the electrolyte. The specific gravity was 1.26d. These lead batteries were tested as specified in JIS-D5301, and their 20 hour rate capacity and
The duration and voltage at 5 seconds of rapid discharge with a discharge current of 150 A at -15°C were determined. Furthermore, these lead batteries were charged for 100 hours at 10.5A,
The gas absorption rate was determined from this weight loss. The results are shown in Table 1.

[Table] Gas absorption rate is calculated by subtracting the reduced weight from the theoretical liquid loss amount calculated when charging a lead-acid battery under the same conditions, and this value is expressed as a percentage when the theoretical liquid loss amount is 100. This is the value. The following can be seen from the results in Table 1. Lead battery A
Compared to lead battery B, it has the same low-rate discharge capacity characteristics in terms of initial performance, and furthermore, in terms of low-temperature high-rate discharge characteristics, the discharge duration is the same, but the discharge voltage characteristics are very superior. This is thought to be because the separator has a high porosity of 80-97% and an extremely low electrical resistance. It is also seen that lead battery A has gas absorption properties. In addition, these lead batteries are JIS-D5301 and SAE
Figures 2 and 3 respectively show the change in capacity and the change in voltage at 30 seconds with respect to the number of charges and discharges when an alternate charge/discharge test was conducted under the conditions of -J240a. In addition, in Figures 2 and 3, lead batteries are used.
Aa is a lead battery A in which water was appropriately refilled within the range of its appropriate electrolyte level, a lead battery An was not refilled at all, and lead batteries Ba and Bn were lead batteries B in which water was refilled. It shows what has been done and what has not been done. The following can be seen from Figures 2 and 3. In other words, lead battery A has better lifespan characteristics than lead battery B, regardless of whether or not water is refilled. This is thought to be to prevent it from falling off. It can also be seen that lead battery A has gas absorption performance and exhibits excellent performance even without fluid replacement. Example A separator material was formed by making through holes in the same material as the separator material used for lead battery A using a device as shown in FIG. In other words, an endless belt 1 with a rubber sheet attached to the upper surface on which the material 14 is moved.
5, and a through hole was made with a blade 17 provided on the roll 16. The through hole is 15mm x 1.00mm on its larger side and on its smaller side.
It had a rectangular shape measuring 15 mm x 0.05 mm. The number of through holes was one per 5 mm square of the material. The two sheets of separator material were placed one on top of the other so that the cut directions of the through holes were perpendicular to each other, and the separator was placed so that the side with the larger through hole faced the positive electrode plate. A lead battery C according to the present invention was obtained by forming an electrode group. When a test similar to Test 1 was conducted on lead battery C, the results shown in Table 2 were obtained.

[Table] In other words, in the lead battery according to the present invention, the amount of electrolyte needs to be added to the extent that the electrode group is sufficiently immersed. This is because when the electrolyte level becomes too low, unlike in conventional sealed lead batteries, there is no flowing electrolyte and the negative electrode plate is exposed. This is because it absorbs even oxygen from the air and self-discharge progresses. Therefore, in the lead-acid battery of the present invention, it is necessary to have an electrolytic solution that flows sufficiently to leak, rather than in an amount that would leave the negative electrode plate half dry. However, a flowing electrolyte is not required in excess. In other words, in conventional non-maintainable automotive lead batteries, approximately 200 c.c.
However, since the lead battery according to the present invention has gas absorption performance, this amount of electrolyte can be reduced to 1/2.
Alternatively, it is possible to reduce the amount to less than that, making it possible to make the battery smaller and lighter, and it is also possible to improve the weight efficiency and volumetric efficiency of a non-maintainable lead battery. Furthermore, the lead battery according to the present invention does not necessarily require a valve, and even if the electrolyte decreases due to causes other than water electrolysis, water can be easily replenished if necessary. In the lead battery according to the present invention, the narrower the gap between the positive and negative electrode plates, the higher the gas absorption.
If it is narrower than 0.4 mm, there is a risk of a short circuit between the positive and negative electrode plates, so it is better to make it wider than 0.4 mm.
The gap between the positive and negative electrode plates is determined depending on the required capacity and gas absorption efficiency, but the upper limit is usually about 3 mm. By the way, a separator made by stacking a plurality of separator materials is extremely effective in preventing short circuits. At this time, it is more effective to overlap the separator materials while shifting the positions of the through holes. In principle, it will be effective if the size of the through-hole in the separator material used in the lead-acid battery of the present invention is larger than the maximum hole diameter of the material of the separator material before the through-hole is provided. By the way, for example, the maximum pore diameter of the separator material shown in Japanese Patent Publication No. 55-5813 is 34μ.
It can be seen that providing a through hole larger than this hole diameter is effective for gas absorption. However, the maximum hole diameter here is not a direct through hole;
From this, it was found that if the diameter of the direct through-hole mechanically provided in the separator material used in the lead-acid battery of the present invention is about 30 μm, the ventilation resistance will be reduced and the effect of improving the gas absorption efficiency will be recognized. However, if the through hole is too large, for example larger than 2500 μm, there is a risk of short circuit between the positive and negative electrode plates, which is not preferable. This point can be summarized as follows. In other words, the size of the through-hole must be such that any circle with a diameter of 30μ or less can pass through it, but it cannot pass through any circle with a diameter of 2500μ or more.
In other words, it is necessary that all the line segments partitioned by the through hole passing through any point of the through hole have a diameter of 30μ or more, and at least one of them must have a diameter of 2500μ or less. Based on this idea, the shape of the through hole may be an elongated shape such as a rectangle with a short side width of 30 to 2500 μm.In fact, such a shape makes it easier to take up a larger area of the through hole, so oxygen gas is more effective in reaching the negative electrode plate. In the separator material for lead batteries according to the present invention, by bringing the surface with particularly large through holes into contact with the positive electrode plate, it is possible to collect oxygen gas generated on the positive electrode plate and make it reach the negative electrode plate in a large amount, thereby improving the gas absorption rate. It is extremely advantageous. As described above, the lead battery according to the present invention can easily have a gas absorption function, has high performance, a long life, and is inexpensive, and does not require a sealed structure.
It has high industrial value as it can be used for various purposes such as automobiles and stationary applications.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of an embodiment of the present invention and a comparative example, and Figs. 2 and 3 show a lead-acid battery A according to a comparative example and a conventional lead-acid battery B, respectively, according to the JIS standard.
Figure 4 is a graph showing the change in capacity versus the number of charges and discharges and the change in voltage at 30 seconds when an alternate charge/discharge test was conducted under the conditions of D5301 and SAE-J240a. FIG. 2 is a front view showing an example of an opening method. DESCRIPTION OF SYMBOLS 1... Positive electrode plate, 2... Negative electrode plate, 3... Separator, 4, 5... Separator material, 11... Electrolyte solution.

Claims (1)

[Claims] 1. In a sheet-shaped material mainly made of glass fibers with a fiber diameter of 1 μm or less, through-holes larger than the maximum pore diameter of the material and with a diameter of 30 to 2,500 μm are provided, and the positions of the through-holes in the material are shifted. A separator is formed by stacking a plurality of electrodes, and the separator is interposed between the positive and negative electrode plates, and the closely spaced electrode group is housed in a battery case, and the electrolyte level in the battery case is sufficiently higher than that of the electrode group. 1. A lead battery, characterized in that a flowing electrolytic solution is present, and the negative electrode plate has an oxygen gas absorption function.