JP2007273367A - Lead-acid storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-acid storage battery for an automobile degraded little in charge receiving performance even in a degraded state. <P>SOLUTION: Sodium ligninsulfonate with a molecular weight of 55,000-65,000 and with the content of organic sulfur of ≥5.5 wt.%, and carbon black made from heavy oil as raw material with a specific surface area of 1,200-1,300 m<SP>2</SP>/g and DBP oil absorption of 450-550 ml/g, are added together as an additive in a negative electrode active substance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to improvement in maintainability of charge acceptance performance of a lead storage battery.

  Today, lead-acid batteries are widely used as inexpensive and reliable batteries for automobiles and industries. For automobiles, a usage form such as a so-called idling stop vehicle (hereinafter abbreviated as an ISS vehicle), in which engine start and stop, which have been widespread in recent years, is repeated. In an ISS vehicle, frequent engine start-up and short charging are repeated many times, so that the vehicle is always in a state of insufficient charging. For this reason, coarse lead sulfate that is difficult to reduce by normal charging is generated and accumulated on the negative electrode plate. For this reason, the battery performance is deteriorated at an early stage. In order to solve such a problem, an additive for improving charge acceptance performance as shown in Document 1 has been considered.

  Additives such as lignin and carbon added to the negative electrode active material of lead-acid batteries are thought to play a role in preventing contraction of the electrode plate active material and improving conductivity mainly during the charge / discharge reaction. The mechanism reaction has not been elucidated yet. Probably, when lead sulfate, which is a discharge product, is reduced and deposited as metallic lead during charging, lignin covers the metallic lead and suppresses crystal growth to produce fine crystals with a reaction area effective for charging and discharging. It is thought that. It is considered that this active material refinement effect increases the reaction area during charging and discharging, and is effective in improving charge acceptance performance. Therefore, lignin and carbon may bring out a synergistic effect depending on the combination.

JP-A-11-250913

  In a usage pattern in which frequent engine start-up and short charging are repeated many times, such as in an ISS car, the lead storage battery is in a reactive state, and thus is likely to be hotter than in a normal usage pattern. When charging and discharging are repeated at such a high temperature state, the active material such as lignin added to the negative electrode plate active material is decomposed into carbon dioxide and water due to oxidation of the active carboxyl group and the like. As a result, the effect of refining the active material of lignin is reduced at an early stage, so that the charge acceptance performance is also lowered at an early stage.

  In view of the above-mentioned case, the present invention proposes an optimal combination of lignin and carbon that hardly deteriorates the charge acceptance performance even when the charge / discharge cycle is repeated under high temperature conditions. In addition, we propose the optimum amount of each lignin and carbon combination.

In order to solve the problems as described above, in the present invention, sodium lignin sulfonate having a molecular weight of 50,000 to 65,000 and an organic sulfur content of 5.5% by weight or more as the lignin of the negative electrode active material of the lead-acid battery Salt was added. This lignin exists more stably with respect to acids than conventional lignins, and the degradation of lignin itself is relatively small even when charging and discharging are repeated. Carbon that can make this lignin work most effectively is carbon black made from heavy oil with a specific surface area (by the BET method) of 1200 to 1300 m ² / g and a DBP oil absorption of 450 to 550 ml / g. Added. By adding these additives together to the negative electrode active material of the lead storage battery, it is possible to provide an excellent lead storage battery with a small decrease in charge acceptance performance even in a deteriorated state as compared with conventional lead storage batteries.

  According to the present invention, it is possible to prevent an early decrease in charge acceptability when the lead storage battery is deteriorated, and as a result, it is possible to extend the life of the battery even in a usage form such as an ISS car.

  Hereinafter, specific examples of the present invention will be described. In addition, this embodiment is one aspect | mode, In the range which does not change the summary, it can change suitably and can implement.

  Examples of the present invention will be described below.

  The negative electrode plate is shown in Table 1 while adding 1% of lead powder and 13% by weight of diluted sulfuric acid (specific gravity 1.26 / 20 ° C conversion) to lead powder and 12% by weight of water to lead powder. Lignin and carbon were added. The amount added at this time is 0.2% by weight for lignin and carbon. Carbons having a DPB oil absorption of 550 ml / g in Table 1 are difficult to manufacture and costly, so they were not included in the test. As additives other than the above, 0.06% by weight of cut fiber and 1.0% by weight of barium sulfate were added and kneaded to prepare a negative electrode paste. 45 g of this negative electrode paste was filled into an expanded current collector (Ca: 0.05%, Sn: 0.5%, balance: Pb) having a thickness of 0.6 mm, and the temperature was 50 ° C. and the humidity was 95% according to the usual method. After being left to mature for 18 hours in this atmosphere, it was dried in an atmosphere at a temperature of 25 ° C. and a humidity of 40% to obtain an unformed negative electrode plate.

  The positive electrode plate is based on 1 kg of lead powder and a cut fiber of 0.01% by weight with respect to the lead powder, and 13% by weight of dilute sulfuric acid (specific gravity 1.26 / 20 ° C conversion) and the lead powder. A positive electrode paste was prepared by kneading with 12% by weight of water. This positive electrode paste was filled into a positive electrode current collector (Ca: 0.05%, Sn: 0.5%, balance: Pb) made of a cast grid, and an atmosphere having a temperature of 50 ° C. and a humidity of 95% was prepared according to a normal method. The plate was left to mature for 18 hours, and then dried in an atmosphere at a temperature of 25 ° C. and a humidity of 40% to obtain an unformed positive electrode plate.

  The above-mentioned non-formed electrode plate is assembled in a structure of two positive electrodes / one negative electrode, inserted into a battery case, poured into dilute sulfuric acid, and formed into a battery case. Produced.

  The average molecular weight of lignin was measured by chromatography. In addition, when lignin having a molecular weight of 65000 or more is used as an additive in the negative electrode, the initial input performance is extremely deteriorated, so it was excluded from the examination here.

  The charge acceptance performance was evaluated as follows.

  The 2V single plate battery produced by the above method was fully charged (6.0 Ah), then left in air at 25 ° C. for 6 hours, discharged at a constant current of 0.2 C, and charged to 90%. It was discharged to become. After that, using a power supply device, constant voltage charging was performed at 2.33 V (corresponding to 14.0 V in a 12 V battery, limited current 30 A), and a current value at 5 seconds was measured. It can be said that the higher the current value, the easier the charging current can be and the better the charge acceptance.

Next, the charging / discharging cycle for the single plate based on the JIS light load test as shown in FIG. 1 was repeated for 2 weeks (960 cycles) to deteriorate the electrode plate. The degree of electrode plate deterioration at this time is estimated to be about 30,000 km travel when mounted on an actual vehicle and used from the results of previous experiments. Then, when the initial charge acceptance performance and the charge acceptance performance at the time of deterioration were obtained, the remaining rate of the charge acceptance performance was calculated. The residual rate is expressed by the following formula.
Residual rate (%) = (Charge acceptability at deterioration / initial charge acceptability) × 100

FIG. 2 shows the remaining rate of charge acceptance performance in each specification. The combination with the highest residual rate has a molecular weight of 50000-65000, a sodium lignin sulfonate having a sulfur content of 5.5% by weight or more, a specific surface area of 1200-1300 m ² / g, and a DBP oil absorption of 450-550 ml / It was a combination with carbon black made from heavy oil as a raw material. In other combinations, it was similar to the conventional product. This result was obtained, and the amount of lignin and carbon added was examined in detail using this lignin and carbon combination.

In FIG. 3, lignin having a molecular weight of 50000-65000, a sulfur content of 5.5% by weight, a heavy oil having a specific surface area of 1200-1300 m ² / g and a DBP oil absorption of 450-550 ml / g are used as raw materials. The remaining rate of charge acceptance performance is shown when carbon black is combined and the amount of lignin and carbon black added is changed. It can be seen that when the amount of lignin added is 0.1 to 0.6 wt% and the amount of carbon is 0.2 to 1.2 wt%, the charge acceptance performance is the highest, and the additive amount is effective in improving charge acceptability. If lignin is added more than this, the input performance will deteriorate. Further, when carbon is added more than this, the filling of the paste is hindered, and the active material becomes brittle after chemical conversion and easily falls off.

  Next, in order to investigate the influence on the discharge performance by increasing the lignin, FIG. 4 shows the test results based on the JIS low temperature high rate discharge test (−15 ° C., 30 A discharge) when changing the amount of lignin. From this figure, it can be seen that if the amount of lignin added is less than 0.1% by weight, the high rate discharge performance at a low temperature is below the JIS standard, so that the amount added must be 0.1% by weight or more.

  From the above results, the lignin amount was 0.1 to 0.6% by weight and the carbon black amount was 0.2 to 1.2% by weight as the optimum addition amount.

  The proposed combination of lignin and carbon is superior in maintaining battery chargeability when the battery deteriorates, and is also suitable as a battery for ISS cars.

It is a charging / discharging cycle diagram based on a JIS light load test. It is the figure which showed the maintainability of charge acceptance property when adding together the lignin from which molecular weight and organic sulfur content differ, and the carbon from which specific surface area and DBP oil absorption differ. It is the figure which showed the residual rate of the charge acceptance performance when changing the lignin addition amount by this invention, and the carbon addition amount. It is the figure which showed the relationship between the amount of lignin addition based on the JIS low temperature high rate discharge test by this invention, and duration.

Claims (3)

In the additive for the negative electrode active material of the lead-acid battery, the molecular weight is 50,000 to 65,000, the organic sulfur content is 5.5% by weight or more, and the specific surface area is 1200 to 1300 m ² / g. A lead storage battery comprising a combination of carbon black made from heavy oil having a DBP oil absorption of 450 to 550 ml / g. The lead acid battery according to claim 1, wherein the amount of carbon added in the negative electrode active material is 0.2 to 1.2 wt% with respect to the amount of the negative electrode active material. The lead acid battery according to claim 1, wherein the amount of lignin added in the negative electrode active material is 0.1 to 0.6% by weight based on the amount of the negative electrode active material.

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