Lead-acid battery

Abstract

A microporous acid-resistant resin separator has a total pore volume ratio of 55% or more and less than 75%. A negative electrode plate is made of an electrode material containing a bisphenol condensate. Thereby, a lead-acid battery can be obtained, which reduces the softening of a positive electrode material and has excellent low-temperature high rate discharge performance.

Claims

1. A lead-acid battery comprising: a positive electrode plate; a negative electrode plate; and a microporous resin separator, wherein the separator has a total pore volume ratio of 55% or more and less than 75%, and the negative electrode plate is made of a negative electrode material containing 0.075 mass % or more and less than 0.2 mass % of a bisphenol condensate.

2. The lead-acid battery according to claim 1, wherein the electrode material of the negative electrode plate contains 0.10 mass % or more and less than 0.2 mass % of the bisphenol condensate.

3. The lead-acid battery according to claim 1, wherein the electrode material of the negative electrode plate contains 0.075 mass % or more and less than 0.175 mass % of the bisphenol condensate.

4. The lead-acid battery according to claim 1, wherein the electrode material of the negative electrode plate contains 0.10 mass % or more and less than 0.175 mass % of the bisphenol condensate.

5. The lead-acid battery according to claim 1, wherein the separator has a total pore volume ratio of 65% or more and less than 75%.

6. The lead-acid battery according to claim 1, wherein the positive electrode plate includes a current collector having four sides each having a frame.

7. The lead-acid battery according to claim 1, wherein the electrode material of the negative electrode plate contains a carbon-based material.

8. The lead-acid battery according to claim 1, wherein the negative electrode material of the negative electrode plate substantially contains no polycarboxylic acid compound.

9. The lead-acid battery according to claim 1, wherein the lead-acid battery is used for a charge control vehicle or an idling stop vehicle.

10. A charge control vehicle or an idling stop vehicle comprising the lead-acid battery according to claim 1.

11. The lead-acid battery according to claim 1, wherein the negative electrode material comprises 0.025 mass % or less of lignin.

12. The lead-acid battery according to claim 1, wherein the negative electrode material comprises no lignin.

13. The lead-acid battery according to claim 1, wherein the negative electrode material comprises 0.1 to 0.4 mass % of carbon black.

14. The lead-acid battery according to claim 1, wherein a molecular weight of the bisphenol condensate is about 4,000 to about 250,000.

15. The lead-acid battery according to claim 1, wherein the negative electrode material comprises less than 0.005% of a polycarboxylic acid compound.

16. The lead-acid battery according to claim 1, wherein the negative electrode material comprises carbon black, barium sulfate, and a synthetic fiber reinforcing material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a positive electrode plate and a separator in Examples.

(2) FIG. 2 shows the distribution of samples with respect to the total pore volume ratio of the separator and a bisphenol condensate.

(3) FIG. 3 is a photograph showing a difference between the softening situation of a positive active material in the case of lignin and the softening situation of a positive active material in the case of the bisphenol condensate.

(4) FIG. 4 is a characteristic diagram showing low-temperature high rate discharge performance and regenerative charge accepting performance with respect to the total pore volume ratio of the separator.

(5) FIG. 5 is a characteristic diagram showing low-temperature high rate discharge performance and regenerative charge accepting performance with respect to the content of the bisphenol condensate.

(6) FIG. 6 is a characteristic diagram showing the transition of low-temperature high rate discharge performance with respect to the number of charge-discharge cycles.

(7) FIG. 7 is a characteristic diagram showing the transition of regenerative charge accepting performance with respect to the number of charge-discharge cycles.

(8) FIG. 8 shows the amount of oil contained in the separator with respect to the total pore volume ratio of the separator.

MODE FOR CARRYING OUT THE INVENTION

(9) Hereinafter, a best mode for carrying out the present invention will be shown. When the present invention is carried out, Examples can be appropriately changed in accordance with the common knowledge of those skilled in the art and disclosure of prior art.

EXAMPLES

(10) Carbon black (0.2 mass % in a negative active material), a condensate containing bisphenol A as a skeleton and having a sulfone group (hereinafter, referred to as bisphenol condensate, average molecular weight: about 8,000, 0.025 mass % to 0.20 mass % in the negative active material), barium sulfate (0.5 mass % in the negative active material), and a synthetic resin fiber of a reinforcing material (0.05 mass % in the negative active material) were added to a lead powder obtained by a ball mill method. Sulfuric acid was added thereto, and these were mixed to produce a paste. An expanded grid (current collector) made of a PbCaSn alloy was filled with the paste, and dried and cured to produce an unformed negative electrode plate. The bisphenol condensate may contain bisphenol A as a skeleton, or bisphenol F or S or the like as a skeleton. Alternatively, a mixture thereof may be used as a skeleton.

(11) The negative electrode current collector may have any shape or composition. The barium sulfate and the synthetic resin fiber are unrelated to the present invention. The lead powder may be of any type.

(12) A synthetic resin fiber of a reinforcing material (0.1 mass % in a positive active material) was added to a lead powder obtained by a ball mill method. Sulfuric acid was added thereto, and these were mixed to produce a paste. An expanded grid (current collector) made of a PbCaSn alloy was filled with the paste, and dried and aged to produce an unformed positive electrode plate. A positive electrode current collector preferably has four sides each having a frame, as shown in FIG. 1. Four polyethylene separators containing polyethylene and oil and having total pore volume ratios of 45 to 55%, 55 to 65%, 65 to 75%, and 75 to 85% were prepared. The negative electrode plate was wrapped with the polyethylene separators. For example, the total pore volume ratio of 55-65% represents a total pore volume ratio of 55% or more and less than 65%.

(13) The positive electrode plate which has four sides each having a frame and the polyethylene separator are shown in FIG. 1. Numeral number 2 designates a positive electrode plate, and numeral number 4 designates a current collector (grid) thereof. The positive electrode plate includes an upper frame 6, a lower frame 7, and right and left vertical frames 8. Crosspieces 10 are disposed in vertical and horizontal directions therebetween. Numeral number 11 designates a lug, and numeral number 12 designates a leg. The circumference of the crosspieces 10 is filled with a positive active material 14. The four sides each have a frame. The positive electrode current collector may be an expanded grid having no vertical frame 8 although it is inferior in life performance. The negative electrode current collector may be obtained by casting or punching, or may be an expanded grid.

(14) A separator 20 contains an acid-resistant synthetic resin such as polyethylene and oil, and is microporous. Numeral number 21 designates a bag-like base. The base is opened in an upper direction and closed in other three directions. The base has a thickness of 0.2 mm, for example. Numeral number 22 designates a rib having a height of 0.8 mm, for example. The thickness of the base 21, the height of the rib 22, the pitch of the rib, and the like may set in accordance with a predetermined method. In Examples, the negative electrode plate is wrapped with the separator 20, and the rib 22 faces to the positive electrode plate 2 side. However, the separator 20 is not limited thereto, and the electrode plate does not need to be wrapped with the separator 20. The material contained in the separator only needs to be a resin having acid resistance, and is not limited to polyethylene.

(15) A water-soluble polymer formed of a bisphenol condensate having a sulfonic acid group (hereinafter, merely referred to as a bisphenol condensate) is represented by the chemical formula such as ((OH)(RSO.sub.3H)Ph-X-Ph(OH)(RSO.sub.3H)CH.sub.2-)n (1) or ((OH)(RSO.sub.3H)Ph-X-Ph(OH)CH.sub.2)n (2), wherein X is a SO.sub.2 group, an alkyl group or the like, but two phenyl groups may be bonded directly without including X. In the formulae (1) and (2), two phenyl groups per monomer are contained in the main chain of the bisphenol condensate. One of the two phenyl groups may be contained in a main chain, and the other may be contained in a side chain. The monomer may contain bisphenol and sodium phenolsulfonate. In the above example, dehydration-condensation with formaldehyde CH.sub.2O is used, and a monomer is polymerized via a methylene group CH.sub.2CH.sub.2. However, the condensation reaction may be carried out with any compound.

(16) Bisphenol S with X being a SO.sub.2 group, bisphenol A with X being C(CH.sub.3).sub.2, and bisphenol F with X being a CH.sub.2 group provide the equivalent result. The formula (1) type or the formula (2) type or the like may be used. The bisphenol condensate may have any molecular weight, for example, about 4000 to about 250,000. The influence of the molecular weight is small. From the point that the bisphenol condensate is a water-soluble polymer containing an aromatic ring, the bisphenol condensate is similar to lignin sulfonic acid often added to the negative active material. However, from the point that the bisphenol condensate does not have a carboxy group, a methoxy group, an ether bonding part, and an alcoholic hydroxyl group, and from the point that the bisphenol condensate has a single unit structure, the bisphenol condensate is different from the lignin sulfonic acid.

(17) R and R are proper alkyl groups such as methylene groups. A sulfonic acid group SO.sub.3H may be directly bonded to a phenyl group without being bonded via the alkyl group. Furthermore, the sulfonic acid group is a functional group for increasing the water solubility of a polymer, and a copolymer of bisphenol S having no sulfonic acid group and sodium phenol methylene sulfonate or the like may be used. Hydrogen of the SO.sub.3H group may be replaced by proper cations such as Na+ ions, and particularly alkali metal ions in the negative active material. Furthermore, for example, a RSO.sub.3H group, a RSO.sub.3H group, and a CH.sub.2 group are in ortho positions with respect to an OH group of a phenyl group (Ph). The bisphenol monomers are mutually bonded via the CH.sub.2 group with which dehydration-condensation has been carried out. Many commercially available bisphenol condensates have two sulfonic acid groups per monomer, but the bisphenol condensate may have any number of sulfonic acid groups per monomer.

(18) Five negative electrode plates and four positive electrode plates were stored in a polypropylene container, and sulfuric acid was added thereto. These were subjected to container formation. The formation may be performed by any technique. The storage battery was discharged at a constant current of 250 A at 15 C., and a time until a terminal voltage was decreased to 1 V/cell was measured as low-temperature high rate discharge performance. Subsequently the state of the storage battery was adjusted to 90% of a charge rate, and the storage battery was then charged for 15 seconds at 2.4 V/cell (restricted current: 100 A) at 0 C. The amount of the charged electricity for 15 seconds was measured as charge accepting performance. Furthermore, the cycle of discharge at a discharge current of 25 A for 4 minutes at 40 C. and charge at a charge voltage of 2.47 V/cell at a restricted current of 25 A for 10 minutes was repeated, and the low-temperature high rate discharge performance and the charge accepting performance were measured per 480 cycles. The number of cycles for decreasing the 30 second terminal voltage at low-temperature high rate discharge to 1.2 V/cell was obtained by interpolation, and defined as a life. The pollution of the container was evaluated based on whether a solution level can be visually recognized from the outside of the container after 1440 cycles. Softening was caused in the storage battery in which the container was remarkably polluted, to increase the amount of the positive active material separated from the current collector.

(19) The main cause of the pollution of the container was carbon black to which oil adheres. This can be inferred as follows. The oil added in order to exhibit the acid resistance of the separator, and the carbon added to the negative electrode eluted into sulfuric acid during energization. The oil and the carbon adhered to the container wall near the solution level due to the compatibility (lipophilicity) of the oil, carbon, and container material. When the pollution adheres to the container wall near the solution level, the electrolyte solution level cannot be confirmed from the outside of the container. When an indicator is provided, the pollution adheres to the indicator, which stops the function of the indicator. This disables electrolyte solution level adjustment during water addition, which causes solution spill and solution loss.

(20) When the solution level was not able to be confirmed even in one cell, the pollution of the container was evaluated as x.

(21) The content of the bisphenol condensate in the negative active material and the total pore volume ratio of the polyethylene separator of each of the samples are shown in FIG. 2. Numbers in FIG. 2 are the sample numbers. The content of the bisphenol condensate is in units of mass %, but it is merely represented by % in the diagram.

(22) Photographs of FIG. 3 show the situation of the softening of a positive active material in a storage battery (No. 4) in which a negative active material contains 0.2 mass % of lignin, and the situation of the softening of a positive active material in a storage battery containing 0.075 mass % (No. 10), 0.125 mass % (No. 13) or 0.175 mass % (No. 15) of a bisphenol condensate. These photographs were obtained by photographing the disassembled storage battery after 1440 cycles. In the case of lignin, the positive active material was softened, and the positive active material was remarkably separated from the grid. The positive active material was slightly softened in the case of the bisphenol condensate of any content, as compared with the case of lignin.

(23) FIG. 4 shows the relation between the total pore volume ratio of the separator and the initial value of the low-temperature high rate discharge performance or the initial value of the regenerative charge accepting performance when the content of the bisphenol condensate is 0.075 mass % and 0.19 mass %. Since the highest performance was obtained at the volume ratio of about 70%, the total pore volume ratio is preferably 55% or more and less than 75%, and most preferably 65% or more and less than 75%. In order to improve the low-temperature high rate discharge performance, it is important to improve the flow properties of the electrolyte solution in the separator. The highest performance obtained at the volume ratio of about 70% shows that the oil in the separator has an adverse influence on the low-temperature high rate discharge performance or the like.

(24) FIG. 5 shows the relation between the content of the bisphenol condensate and the low-temperature high rate discharge performance or the regenerative charge accepting performance. The total pore volume ratio of the separator is 65 to 75%. When the content of the bisphenol condensate was 0.2 mass %, the regenerative charge accepting performance was remarkably deteriorated, and thus it is necessary to set the content to be less than 0.2 mass %. When the content was less than 0.05 mass %, the low-temperature high rate discharge performance was not enough.

(25) Table 1 shows the results when lignin was used. Table 2 shows the results when the bisphenol condensate was used. When lignin is used and the total pore volume ratio of the separator is set to 65% or more, the container is easily polluted, and thus it is difficult to set the total pore volume ratio to 65% or more. On the other hand, it is found that the change of lignin to the bisphenol condensate improves the low-temperature high rate discharge performance and the regenerative charge accepting performance, and decreases the pollution of the container. The total pore volume ratio of the separator is preferably 55% or more and less than 75%. When the low-temperature high rate discharge performance is important, the content of the bisphenol condensate is preferably increased within the range of 0.075 mass % or more and less than 0.2 mass %. When the regenerative charge accepting performance is important, the content of the bisphenol condensate is preferably decreased within the range. Apart from this, when the bisphenol condensate was used, the softening of the positive active material was also decreased. Furthermore, evaluations on whether various kinds of performances reach the practical range are added to Table 2.

(26) TABLE-US-00001 TABLE 1 No. 1 No. 2 No. 3 No. 4 No. 5 Total pore volume ratio of 65-75 45-55 55-65 65-75 75-85 separator/% Presence or absence of NA positive electrode vertical frame rib Kind of organic shrink-resistant Lignosulfonic acid agent Additive amount/% 0.175 0.2 Initial low-temperature high 161 140 158 165 160 rate/sec Initial regenerative charge 297 260 275 292 280 acceptance/Asec Evaluation of container pollution X X X after 1440 cycles Symbols and X represent good and poor, respectively.

(27) TABLE-US-00002 TABLE 2 No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Total pore volume 65-75 45- 55- 65- 75- 65- 65- 65- 65- 45- 55- 65- 75- 55- 65- 65- ratio of separator/% 55 65 75 85 75 75 75 75 55 65 75 85 65 75 75 Presence or absence N/A A of positive electrode vertical frame rib Kind of organic shrink-resistant agent Bisphenol condensate Additive amount/% 0.025 0.050 0.075 0.100 0.125 0.15 0.175 0.190 0.200 0.100 Initial low- 150 161 152 168 175 170 179 183 186 188 166 183 191 174 196 195 196 temperature high rate/sec Evaluation of low- x x x temperature high rate Initial regenerative 412 405 365 382 402 387 400 366 350 330 280 298 315 285 270 286 405 charge acceptance/Asec Regenerative x x x x evaluation Evaluation of x x x container pollution after 1440 cycles Overall evaluation x x x x x x x x Number of life cycles 1630 2120 Symbols and x represent good and poor, respectively.

(28) The corrosion of the positive electrode current collector was likely to be promoted when the bisphenol condensate was used, due to a decrease in a hydrogen generation overvoltage in the negative electrode. Then, when the positive electrode current collector having the expanded grid having no vertical frame (sample 12) was compared with the positive electrode current collector having the grid having a vertical frame (sample 22), it was found that the life performance is remarkably improved by providing the vertical frame.

(29) FIG. 6, FIG. 7, and Table 3 show how the low-temperature high rate discharge performance and the regenerative charge accepting performance change with the number of cycles. The samples containing the bisphenol condensate (samples 10, 12, 14, and 22) have higher durability than those of the samples containing lignin (samples 4 and 6). It is found that the provision of the vertical frame rib in the positive electrode current collector (sample 22) allows the low-temperature high rate discharge performance to be maintained at a higher value than that in the case where the vertical frame rib is not provided (sample 12).

(30) TABLE-US-00003 TABLE 3 Cycle No. 4 No. 6 No. 10 No. 12 No. 14 No. 22 Low- 0 165 150 175 179 186 196 temperature 480 46 78 92 100 114 135 high rate 960 33 55 71 78 93 116 discharge 1440 13 40 56 65 81 105 performance 1920 90 (sec) Regenerative 0 292 412 402 400 350 405 charge 480 165 220 250 255 280 258 accepting 960 121 165 180 225 250 232 performance 1440 85 155 165 200 220 212 (Asec) 1920 192

DESCRIPTION OF REFERENCE SIGNS

(31) 2 positive electrode plate 4 current collector 6 upper frame 7 lower frame 8 vertical frame 10 crosspiece 11 lug 12 leg 14 positive active material 20 separator 21 base 22 rib