Diaper accumulator

Abstract

Lead-acid battery including: a positive plate electrode (1) with a positive electrode mesh (1a) and a positive, active electrode material (1b); a negative plate electrode (2) with a negative electrode mesh (2a) and a negative active electrode material (2b); a plate electrode group (4) comprising the positive plate electrode (1), the negative plate electrode (2), and a separator (3) placed between the positive plate electrode (1) and the negative plate electrode (2); a battery casing (5) containing a plurality of cell chambers (5a), each of which contains the plate electrode group (4) and an electrolyte; and a lid (6) which closes an opening of the battery housing (5); The ratio P / N of the mass P of the positive, active electrode material (1b) to the mass N of the negative, active electrode material (2b) is between 1.25 or more and 1.65 or less. the negative electrode network (2a) contains bismuth in an amount of 1 ppm or more and 300 ppm or less.

Description

[Technical field]

[0001] The present invention relates to a lead-acid battery for vehicle starters. [State of the art]

[0002] In lead-acid vehicle starters, a lead-acid battery intended for installation in a vehicle with an idle stop system is to be thoroughly discharged to a relatively low state of charge (SOC), and therefore durability against repeated deep discharges is necessary. Patent 1 discloses a technique for optimizing the weight ratio between positive and negative active electrode material based on the results of a life cycle test after over-discharging batteries. Patent 2 also discloses a technique for optimizing the weight ratio between positive and negative active electrode material to improve life cycle characteristics under practical idle stop conditions.The optimal range of the P / N ratio of the mass P of the positive, active electrode material to the mass N of the negative, active electrode material is between 0.77 and 1.43 in patent specification 1 and between 0.91 and 1.43 in patent specification 2. CN 104 282 910 A discloses the use of bismuth as an additive to a negative electrode in a lead-acid battery. JP 2004 087 248 A describes a lead-acid battery in which a mass ratio of a negative, active electrode material to a positive, active electrode material of 0.75 and above, and less than 0.9, is set.

[0003] The JP 2003 051 334 A is a lead-acid battery in which carbon is added to the negative, active electrode material. [Bibliography][Patent Specifications] [PTL 1] Japanese publication of patent publication No. JP 2006 114 417 A [PTL 2] Japanese Patent Publication No. JP 5 587 523 B1 [Summary of the invention][Technical problem]

[0004] In recent years, vehicles with idle stop systems have become increasingly popular, and consequently, cases sometimes arise where the lead-acid batteries installed in these vehicles are subjected to harsher conditions than originally anticipated during development. Under such conditions, it is frequently observed that the life cycle characteristics cannot be sufficiently maintained, even when the techniques described in patents 1 and 2 are applied, if the battery is actually installed in a vehicle and subjected to repeated deep discharges.

[0005] The present invention is made with regard to the above-mentioned problem and aims to create a highly reliable lead-acid battery which can sufficiently maintain its life cycle properties even when operating under the comparatively harsh conditions of an idle stop control. [Solution to the task]

[0006] One aspect of the present invention relates to a lead-acid battery comprising: a positive plate electrode with a positive electrode mesh and a positive active electrode material; a negative plate electrode with a negative electrode mesh and a negative active electrode material; a plate electrode assembly comprising the positive plate electrode, the negative plate electrode, and a separator placed between the positive and negative plate electrodes; a battery casing comprising a plurality of cell compartments, each containing the plate electrode assembly and an electrolyte; and a lid closing an opening of the battery casing. The mass-to-mass ratio (P / N) of the positive active electrode material to the negative active electrode material is between 1.25 or more and 1.65 or less.The negative electrode network contains bismuth in amounts of 1 ppm or more and 300 ppm or less.

[0007] In a preferred embodiment, the P / N ratio is 1.43 or more and 1.65 or less.

[0008] In a preferred embodiment, the P / N ratio is 1.25 or more and 1.43 or less, and the active, negative electrode material contains carbon in an amount of 0.10 wt.% or more and 0.45 wt.% or less.

[0009] In a preferred embodiment, the liquid level of the electrolyte is above an upper edge of the plate electrode group. [Advantageous effects of the invention]

[0010] According to the present invention, it is possible to create a highly reliable lead-acid battery which can sufficiently maintain its life cycle properties, even when operating under comparatively harsh conditions of an idle stop control. [Brief description of the drawings] [ Fig. 1] Schematic, general view of a lead-acid battery of the present invention. [ Fig. 2] Illustration of an example of an essential part of the lead-acid battery of the present invention. [Description of the embodiment]

[0011] One embodiment of the present invention is described below with reference to the drawings.

[0012] Fig. Figure 1 is a schematic, general view of a lead-acid battery of the present invention, and Fig.Figure 2 illustrates an example of a negative plate electrode, which is an essential part of the lead-acid battery of the present invention. A plurality of plate electrode groups 4, each comprising a positive plate electrode 1, a negative plate electrode 2, and an intermediate separator 3, are enclosed in a battery housing 5, which contains a plurality of cell chambers 5a and an electrolyte (not shown). The opening of the battery housing 5 is closed with a cover 6. The positive plate electrode 1 comprises a positive electrode mesh 1a and a positive, active electrode material 1b. The negative plate electrode 2 comprises a negative electrode mesh 2a and a negative, active electrode material 2b.

[0013] The present invention comprises two features. The first is that the ratio P / N of the mass P of the positive active electrode material 1b to the mass N of the negative active electrode material 2b is between 1.25 or more and 1.65 or less. The second is that the negative electrode mesh 2a contains bismuth in an amount of 1 ppm or more and 300 ppm or less.

[0014] Regarding the problem associated with the idle stop control, patent specification 1 stipulates that the lead-acid battery is over-discharged, while patent specification 2 stipulates that the lead-acid battery is subjected to repeated, rapid charging and comparatively thorough discharging. On the other hand, an increasing number of vehicles with an idle stop system employ a control method in which a regenerative current is generated during braking and similar events, and the lead-acid battery is charged with this current. To achieve more efficient charging with the generated current, it is desirable to keep the state of charge (SOC) of the lead-acid battery relatively low (so that it is not fully charged).Under such conditions, even by using configurations as disclosed in patent specification 1 or 2, which are optimized to fully charge a battery for a short moment using a controller, sufficient battery power cannot be achieved.

[0015] Especially when the battery is charged and discharged under conditions where the state of charge (SOC) is below 100%, a phenomenon called acid stratification occurs. This means that the concentration of sulfate ions in the electrolyte is lower in the upper layer than in the lower layer. If this occurs in the upper layer, where the sulfate ion concentration is relatively depleted, it is unlikely that lead sulfate will be formed as a discharge product (it is difficult to continue discharging). Conversely, in the lower layer, where the sulfate ion concentration is relatively high, it is unlikely that sulfate ions will be released from the lead sulfate (it is difficult to continue charging). Because of this imbalance, where lead sulfate is deposited in excess in the lower layer, the overall discharge reaction is slowed down.This results in a deterioration of the life cycle characteristics. Stratification is prevented when the electrolyte is mixed with the gas produced by electrolyte hydrolysis (gas generation), which occurs in the final stage of charging. However, under conditions where the state of charge (SOC) is deliberately kept below 100%, charging cannot progress to the final stage, and the aforementioned effect cannot be expected.

[0016] To solve this problem, the present invention applies the features mentioned above.

[0017] The first characteristic is that the mass-to-noise ratio (P / N) of the positive active electrode material 1b to the mass-to-mass (N) of the negative active electrode material 2b is between 1.25 or more and 1.65 or less. Typically, the P / N ratio is set below 1.25 to ensure charging power while maintaining the predetermined battery capacity. However, if charging is controlled as described above, keeping the state of charge (SOC) relatively low (not achieving a full charge), the SOC can drop significantly during the frequent charging and discharging cycles in the idle stop control, despite the expected improvement in charging efficiency due to the absence of overcharging. This leads to a degradation mode in which the positive active electrode material 1b softens and detaches from the positive plate electrode 1.This charging control method requires a new design concept: significantly increasing the amount of positive active electrode material 1b relative to the negative active electrode material 2b. This prevents stress on the positive active electrode material 1b during periods of low state of charge (SOC) and thus avoids the separation of the positive active electrode material from the positive plate electrode 1 due to softening. Intensive studies revealed that this effect is particularly pronounced when the P / N ratio is set to 1.25 or higher. However, setting the P / N ratio above 1.65 leads to insufficient charging due to a lack of negative active electrode material 2b and, conversely, to a deterioration of the life cycle characteristics.

[0018] Although the aforementioned effect, obtained through the first feature, is already outstanding when the P / N ratio is above 1.43, it can also be outstanding when the P / N ratio is 1.25 or more and 1.43 or less, by adding carbon to the negative, active electrode material 2b in an amount of 0.10 wt% or more and 0.45 wt% or less. The carbon, which does not participate in charging or discharging and is uniformly distributed over the surface of the negative plate electrode 2, allows gas generation by hydrolysis to be achieved simultaneously with the charging reaction. This, in conjunction with the effect obtained by adding an appropriate amount of bismuth to the negative electrode mesh, can further mix the electrolyte more vigorously and enhance the elimination of stratification. As a result, the charging / discharging reaction at the positive plate electrode 1 can proceed homogeneously.Therefore, although the battery is configured to have a P / N ratio of 1.25 or higher and 1.43 or lower—that is, configured such that, in the event of a loss of reaction homogeneity at the positive plate electrode 1, the battery reaches a state of charge (SOC) range where the positive active electrode material 1b becomes locally softened—it can be controlled so that it does not reach an SOC range where the positive active electrode material 1b becomes locally softened. It is also noted that if the amount of carbon contained in the negative active electrode material 2b is below 0.10 wt%, the aforementioned effect is insufficient; and if it is above 0.45 wt%, hydrolysis proceeds somewhat excessively, and the amount of electrolyte is reduced, resulting in a slight deterioration of the life cycle characteristics.

[0019] The second characteristic is that the negative electrode lattice 2a contains bismuth in amounts of 1 ppm or more and 300 ppm or less. The presence of an appropriate amount of bismuth in the negative electrode lattice 2a reduces the hydrogen overpotential, and hydrogen gas tends to be generated despite a state of charge (SOC) below 100%, thus facilitating electrolyte diffusion. This eliminates stratification. To achieve this effect, it is necessary to contain bismuth in the negative electrode lattice 2a in an amount of 1 ppm or more. However, if the amount exceeds 300 ppm, the hydrogen overpotential is reduced too much, and electrolyte hydrolysis occurs excessively, resulting in a significant reduction of the electrolyte.This accelerates the corrosion of the strip-shaped current collectors (strips) exposed above the electrolyte of the positive and negative plate electrodes 1 and 2, which conversely causes a deterioration of the life cycle properties.

[0020] According to the present invention, configured to include the two features described above, it is possible to create a lead-acid battery which sufficiently demonstrates its life cycle characteristics even when repeatedly charged and discharged under SOC conditions below 100%.

[0021] The effect of the present invention is outstanding in a lead-acid battery for a vehicle starter, particularly in a liquid-type lead-acid battery in which the liquid level of the electrolyte is above an upper edge of the plate electrode group 4.

[0022] In the present invention, the mass ratio P / N of the positive active electrode material 1b to the mass N of the negative active electrode material 2b and the mass ratio of the carbon contained in the negative active electrode material 2b are defined such that a state of charge (SOC) of 100% is assumed. In particular, the mass ratio of the present invention relates to a mass ratio in a lead-acid battery that is deliberately charged before installation in a vehicle or in a starting state for a vehicle starter until the SOC reaches 100% (for example, using an additional power source).

[0023] The effects of the present invention will now be described with reference to the examples. (1) Production of the lead-acid battery

[0024] A lead-acid battery of size D26L, as described in JIS D5301, was manufactured in the present example as a lead-acid battery with cell chambers 5a, each of which accommodates seven positive plate electrodes 1 and eight negative plate electrodes 2, the negative plate electrodes 2 being each enclosed in bag-shaped polyethylene separators 3.

[0025] The positive plate electrode 1 was obtained by forming a lead oxide powder with sulfuric acid and purified water to produce a precursor paste of positive active electrode material 1b, and the paste was filled into a positive electrode mesh 1a (spread mesh) of lead alloy sheet (thickness: 1.1 mm) comprising calcium.

[0026] The negative plate electrode 2 was obtained by: Adding carbon and an organic additive to lead oxide powder and forming the powder with sulfuric acid and purified water to produce a precursor paste of the negative active electrode material 2b; and filling the paste into a negative electrode mesh 2a (spread mesh) of lead alloy sheet (thickness: 1.1 mm) comprising calcium and, depending on the condition, bismuth.

[0027] The mass ratio of the bismuth contained in the negative electrode mesh 2a was varied as shown in Table 1. Similarly, the mass ratio of the carbon covering the negative active electrode material 2b and the ratio P / N of the mass P of the positive active electrode material 1b to the mass N of the negative active electrode material 2b were varied as shown in Table 1, with the SOC set to 100%.

[0028] The obtained positive and negative plate electrodes 1 and 2 were aged and dried. Subsequently, the negative plate electrodes 2 were each placed in a bag-shaped polyethylene separator 3 and stacked alternately on top of the positive plate electrodes 2 to form a plate electrode assembly 4 comprising seven positive plate electrodes and eight negative plate electrodes 2, stacked alternately with a separator 3 in between. Each plate electrode assembly 4 was placed in one of the six cell chambers 5, which were separated by a partition, and the six cells were directly connected. An electrolyte, consisting of dilute sulfuric acid with a density of 1.28 g / cm³, was then added. 3 It involves injecting substances to carry out a chemical reaction. A lead-acid battery was manufactured in this way. (2) Life characteristics

[0029] The manufactured lead-acid batteries were evaluated by the steps below after the SOC was set to 90%. A. Subjecting a battery to a discharge at 45 A for 59 seconds B. Subjecting a battery to a discharge at 300 A for 1 second C. Subjecting a battery to charging at a constant voltage of 14.0 V for 60 seconds with a maximum current limited to 100 A D. After 3600 repetitions of a charge-discharge cycle, consisting of A, B and C, performed in this order, the battery is subjected to a refreshing charge, i.e., a charge at a constant voltage of 14.0 V for 30 minutes with a maximum current limited to 50 A. E. After the battery has rested for 48 hours, reset the SOC to 90%.

[0030] Steps A to E above were repeated, and when the discharge voltage fell below 7.2 V, the battery was considered to be at the end of its service life. Based on this assessment, a decision was made every 3600 cycles whether or not to continue the test. The number of cycles performed before the decision was made not to continue is shown in Table 1, along with the composition conditions. [Table 1] battery P / N ratio Bismuth negative electrode network (ppm) Carbon in negative, active electrode material (wt%) Life cycle characteristics A-1 1,21 150 0,05 46800 A-2 1,25 150 0,05 68400 A-3 1,34 150 0,05 72000 A-4 1,43 150 0,05 72000 A-5 1,45 150 0,05 82800 A-6 1,55 150 0,05 100800 A-7 1,65 150 0,05 79200 A-8 1,69 150 0,05 50400 B-1 1,55 0,5 0,05 50400 B-2 1,55 1 0,05 68400 B-3 1,55 10 0,05 79200 B-4 1,55 50 0,05 93600 B-5 1,55 150 0,05 100800 B-6 1,55 200 0,05 93600 B-7 1,55 250 0,05 82800 B-8 1,55 300 0,05 72000 B-9 1,55 330 0,05 50400 C-1 1,25 150 0,05 68400 C-2 1,25 150 0,10 79200 C-3 1,25 150 0,30 93600 C-4 1,25 150 0,45 79200 C-5 1,25 150 0,50 72000 D-1 1,34 150 0,05 72000 D-2 1,34 150 0,10 82800 D-3 1,34 150 0,30 93600 D-4 1,34 150 0,45 82800 D-5 1,34 150 0,50 72000 E-1 1,43 150 0,05 72000 E-2 1,43 150 0,10 82800 E-3 1,43 150 0,30 93600 E-4 1,43 150 0,45 82800 E-5 1,43 150 0,50 68400 F-1 1,45 150 0,05 82800 F-2 1,45 150 0,10 90000 F-3 1,45 150 0,30 93600 F-4 1,45 150 0,45 86400 F-5 1,45 150 0,50 79200

[0031] A comparison was made between batteries A-1 to A-8. Battery A-1 had a P / N ratio of less than 1.25, and battery A-8 had a P / N ratio greater than 1.65, and both exhibited inferior life-cycle characteristics. These batteries were disassembled, and it was observed that: in battery A-1, the positive, active electrode material 1b had softened and separated; and in battery A-8, charging had not progressed sufficiently. This indicates that the P / N ratio should be approximately 1.25 or greater and 1.65 or less, and preferably greater than 1.43 and 1.65 or less.

[0032] A comparison was made between batteries B-1 to B-9. Battery B-1, in which the amount of bismuth contained in the negative electrode network 2a was less than 1 ppm, and battery B-9, in which the amount of bismuth was more than 300 ppm, both exhibited inferior life cycle characteristics. These batteries were disassembled, and it was observed that: in battery B-1, electrolyte stratification was severe; and in battery B-9, the electrolyte was extremely reduced. This indicates that the amount of bismuth contained in the negative electrode network 2a is appropriately 1 ppm or more and 300 ppm or less.

[0033] Based on the evaluation of the results of batteries A-1 to A-8 together with batteries B-1 to B-9, it is understood that the P / N ratio and the amount of bismuth contained in the negative electrode network 2a should be adjusted to the appropriate range.

[0034] Batteries C-1 to C-5 were configured such that, while the P / N ratio was kept constant at 1.25 and the amount of bismuth in the negative electrode mesh 2a was kept constant at 150 ppm, the amount of carbon in the negative active electrode material 2b was varied from 0.05 wt% to 0.50 wt%. Batteries D-1 to D-5 were configured in the same manner as batteries C-1 to C-5, except that the P / N ratio was kept constant at 1.34. Batteries E-1 to E-5 were configured in the same manner as batteries C-1 to C-5, except that the P / N ratio was kept constant at 1.43. Batteries F-1 to F-5 were configured in the same manner as batteries C-1 to C-5, except that the P / N ratio was kept constant at 1.45. Comparisons were made among these batteries.

[0035] When the P / N ratio is in the range of 1.25 to 1.43, and carbon is present in the negative active electrode material 2b in an amount of 0.10 wt% or more and 0.45 wt% or less, better life cycle properties are achieved than when carbon is present in the negative active electrode material 2b in an amount of 0.05 wt%. This is presumably because the addition of an appropriate amount of carbon facilitates gas generation by hydrolysis and therefore eliminates stratification. However, increasing the amount of carbon in the negative active electrode material 2b to more than 0.45 wt% does not lead to better life cycle properties. This is presumably because hydrolysis proceeds somewhat excessively, which tends to reduce the electrolyte.

[0036] The above trend is only observed when the P / N ratio is in the range of 1.25 to 1.43. This is presumably due to the following reason: When the P / N ratio is 1.25 or higher and 1.43 or lower, the battery, upon loss of reaction homogeneity at the positive plate electrode 1, reaches a state of charge (SOC) region where the positive, active electrode material 1b softens locally. In this region, the effect achieved by adding an appropriate amount of carbon to the negative, active electrode material 2b becomes noticeable. When the P / N ratio exceeds 1.43, the battery can remain relatively far from the SOC region where the positive, active electrode material 1b softens locally.

[0037] Although the present invention has been described by preferred embodiments, these should not be interpreted as limiting the scope of the invention, and various variations are possible. For example, the positive electrode network 1a, like the negative electrode network 2a, can contain bismuth in an amount of 1 ppm or more and 300 ppm or less. [Industrial applicability]

[0038] The present invention is useful in lead-acid batteries for installation in vehicles with an idle stop system. [List of reference symbols] 1 positive plate electrode 1a positive electrode network 1b positive, active electrode material 2 negative plate electrode 2a negative electrode network 2b negative, active electrode material 3 Separator 4 plate electrode group 5 battery cases 5a Cell chamber 6 lids

Claims

[1] Lead-acid battery comprising: a positive plate electrode (1) with a positive electrode mesh (1a) and a positive, active electrode material (1b); a negative plate electrode (2) with a negative electrode mesh (2a) and a negative active electrode material (2b); a plate electrode group (4) comprising the positive plate electrode (1), the negative plate electrode (2), and a separator (3) placed between the positive plate electrode (1) and the negative plate electrode (2); a battery casing (5) containing a plurality of cell chambers (5a), each of which contains the plate electrode group (4) and an electrolyte; and a lid (6) which closes an opening of the battery housing (5); The ratio P / N of the mass P of the positive, active electrode material (1b) to the mass N of the negative, active electrode material (2b) is between 1.25 or more and 1.65 or less. the negative electrode network (2a) contains bismuth in an amount of 1 ppm or more and 300 ppm or less. [2] Lead-acid battery according to claim 1, wherein the P / N ratio is 1.43 or more and 1.65 or less. [3] Lead-acid battery according to claim 1, wherein the P / N ratio is 1.25 or more and 1.43 or less, and the active, negative electrode material (2b) contains carbon in an amount of 0.10 wt.% or more and 0.45 wt.% or less. [4] Lead-acid battery according to claim 1, wherein the liquid level of the electrolyte is above an upper edge of the plate electrode group (4).

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