lead-acid battery

Abstract

DEPCT67 What is provided is a lead-acid battery with excellent high-temperature resistance and... The reduction of moisture in the electrolyte of the lead-acid battery of this invention can be suppressed. This includes the battery enclosure which contains the cell chamber and the group of electrode plates arranged within that cell chamber. Electrolyte is injected into the cell chamber, which contains a group of electrode plates including the anode and catheter plates. A number of negative electrodes are arranged alternately, and a separator is placed between the electrode plates. Positive and negative electrode plates; positive electrode plates include a positive electrode mixture containing a positively functioning material. and the positive electrode current collector plate (11) with a grid section (110) that holds the mixture. The anode and the anode current collector plate (11) are made of lead alloy. Containing 0.035% by mass or more and 0.08% by mass or less of Ca 0.50% by mass or Greater than and 1.0% by mass or less than Sn0.003% by mass or greater than and 0.035%. By mass or less, Ag is greater than 0% by mass and 0.02% by mass or less of Bi. Balanced with lead and unavoidable impurities;

Description

lead acid battery

[0001] The present invention relates to a lead-acid battery.

[0002] A typical lead-acid battery, a flooded lead-acid battery, includes a battery case with a cell chamber, a plate assembly housed in the cell chamber, and an electrolyte injected into the cell chamber. The plate assembly includes multiple positive and negative plates arranged alternately, and a separator disposed between the positive and negative plates. The positive plate has a positive electrode mixture containing a positive electrode active material held on a current collector. The negative plate has a current collector holding a negative electrode mixture containing a negative electrode active material. Dilute sulfuric acid is used as the electrolyte. Such flooded lead-acid batteries are widely used as automobile batteries, etc.

[0003] In recent years, the temperature inside automobile engine compartments has risen significantly due to an increase in equipment and designs that eliminate unnecessary space. Therefore, flooded lead-acid batteries for automobiles are used in environments where corrosion and growth (deformation due to grid expansion) of the positive electrode grid are likely to occur, and measures to extend their lifespan are strongly required. Furthermore, flooded lead-acid batteries for automobiles are often used in an overcharged state. When used in an overcharged state, water in the electrolyte is electrolyzed, and the generated hydrogen and oxygen gases are released to the outside of the battery through the vent, resulting in a decrease in the water content of the electrolyte.

[0004] Patent Document 1 describes the alloy composition of the positive current collector plate constituting a maintenance-free lead-acid battery (requiring no maintenance such as water replenishment, or only once or only occasionally, or preferably not at all, throughout the expected life of the battery). It also discloses the use of a positive grid made of a lead alloy containing 0.025 to 0.06 mass % Ca, 0.3 to 0.7 mass % Sn, and 0.015 to 0.045 mass % Ag to provide a maintenance-free lead-acid battery that can be used as an automotive SLI battery (a battery used for starting, lighting, and ignition) and has a sufficient service life (good corrosion resistance of the positive current collector plate) even when exposed to a relatively high-temperature environment.

[0005] The positive electrode current collector of a maintenance-free lead-acid battery has conventionally been formed from a Pb-Ca alloy, and the positive electrode current collector is formed using a lead alloy to which alloying elements such as Sn, Ag, Ba, Cu, Bi, Se, etc. are added depending on the application. In particular, it is known that the use of a lead alloy to which Sn or Ag is added greatly improves the corrosion resistance and creep resistance of the positive electrode current collector.

[0006] Patent Document 2 discloses the use of a positive electrode grid (positive electrode current collector plate) made of a lead alloy containing 0.05 to 0.085 mass% Ca, 1.2 to 2.0 mass% Sn, 0.002 to 0.02 mass% Bi, 0.0001 to 0.002 mass% Ag, and 0.005 to 0.03 mass% Al to obtain a lead-acid battery with a long life at high temperatures. It also discloses that by setting the alloy components within the above ranges, a grid with excellent workability (strength) can be obtained.

[0007] In addition to flooded lead-acid batteries, valve-regulated lead-acid batteries (VRLABs) are also known as lead-acid batteries. VRLABs have a sealed structure containing an electrolyte and a laminate. The laminate consists of alternatingly arranged positive and negative plates and a separator between the positive and negative plates. The electrolyte is either impregnated into the glass fiber mat separator or made immobile by gelation. VRLABs are often used as backup power sources for communications, power, disaster prevention, and other applications, and require less frequent maintenance. Therefore, minimizing the loss of electrolyte moisture is more important than with flooded lead-acid batteries, and batteries are designed to prevent premature end of life due to electrolyte moisture loss, or so-called "depletion."

[0008] The mechanism by which water loss in the electrolyte occurs in valve-regulated lead-acid batteries is as follows: During charging, valve-regulated lead-acid batteries generate oxygen gas from the positive electrode plate through the electrolysis of water. This oxygen gas is absorbed by the negative electrode plate due to the oxygen gas absorption capacity of the negative electrode active material. Water is then generated from the absorbed oxygen gas, which prevents the oxygen gas generated from the positive electrode plate from being released outside the battery. However, if the amount of oxygen gas generated in the positive electrode plate exceeds the oxygen gas absorption capacity of the negative electrode active material, the oxygen gas inside the battery is released outside the battery through the control valve, causing a loss of water in the electrolyte.

[0009] U.S. Patent No. 5,298,350 Japanese Patent No. 6406457

[0010] However, the lead-acid batteries described in Patent Documents 1 and 2 have room for improvement in terms of achieving both high-temperature durability and maintenance-free characteristics (reduction in water content of the electrolyte is suppressed, eliminating the need for water replenishment) as lead-acid batteries used under harsh conditions such as high-temperature environments. An object of the present invention is to provide a lead-acid battery that is excellent in high-temperature durability and can suppress reduction in water content of the electrolyte.

[0011] To solve the above problems, a first aspect of the present invention provides a lead-acid battery having the following configurations (1) and (2): (1) An electrolytic solution and a laminate, the laminate including a plurality of alternatingly arranged positive and negative electrode plates and a separator disposed between the positive and negative electrode plates, the positive electrode plate including a positive electrode mixture containing a positive electrode active material and a positive electrode current collector including a grid portion in which the positive electrode mixture is held. (2) The positive electrode current collector is formed of a lead alloy containing Ca in the range of 0.035% by mass to 0.08% by mass, Sn in the range of 0.50% by mass to 1.0% by mass, Ag in the range of 0.003% by mass to 0.035% by mass, Bi in the range of more than 0.02% by mass to 0.02% by mass, and the remainder being lead and unavoidable impurities.

[0012] A second aspect of the present invention provides a lead-acid battery having the above configuration (1) and the following configuration (3): (3) the positive electrode current collector plate is formed of a lead alloy containing Ca in the range of 0.035% by mass to 0.07% by mass, Sn in the range of 0.55% by mass to 0.9% by mass, Ag in the range of 0.010% by mass to 0.030% by mass, Bi in the range of 0.0001% by mass to 0.010% by mass, and the balance being lead and unavoidable impurities. A third aspect of the present invention provides a lead-acid battery having the above configuration (1) and the following configuration (4). (4) The positive electrode current collector plate is formed of a lead alloy containing Ca in the range of 0.035% by mass or more and 0.06% by mass or less, Sn in the range of 0.60% by mass or more and 0.8% by mass or less, Ag in the range of 0.015% by mass or more and 0.025% by mass or less, Bi in the range of 0.0005% by mass or more and 0.005% by mass or less, and the remainder being lead and unavoidable impurities.

[0013] A fourth aspect of the present invention provides a lead-acid battery having the above configuration (1) and the following configuration (5): (5) The positive electrode current collector plate is formed of a lead alloy containing Ca in the range of 0.035% by mass to 0.08% by mass, Sn in the range of 0.50% by mass to 1.0% by mass, Ag in the range of 0.003% by mass to 0.035% by mass, Bi in the range of more than 0.02% by mass to 0.02% by mass, Ba in the range of more than 0% by mass to 0.001% by mass, and the balance being lead and unavoidable impurities. A fifth aspect of the present invention provides a lead-acid battery having the above configuration (1) and the following configuration (6). (6) The positive electrode current collector plate is formed of a lead alloy containing Ca in the range of 0.035% by mass or more and 0.07% by mass or less, Sn in the range of 0.55% by mass or more and 0.9% by mass or less, Ag in the range of 0.010% by mass or more and 0.030% by mass or less, Bi in the range of 0.0001% by mass or more and 0.010% by mass or less, Ba in the range of more than 0 and 0.001% by mass or less, and the remainder being lead and unavoidable impurities.

[0014] A sixth aspect of the present invention provides a lead-acid battery having the above configuration (1) and the following configuration (7): (7) The positive electrode current collector plate is formed of a lead alloy containing Ca in the range of 0.035% by mass to 0.06% by mass, Sn in the range of 0.60% by mass to 0.8% by mass, Ag in the range of 0.015% by mass to 0.025% by mass, Bi in the range of 0.0005% by mass to 0.005% by mass, Ba in the range of more than 0% by mass to 0.001% by mass, and the remainder being lead and unavoidable impurities. When the lead-acid battery of any of the first to sixth aspects of the present invention is a flooded lead-acid battery, the above configuration (1) has the following configuration (11): (11) The lead-acid battery includes a battery case having a cell chamber, a plate pack housed in the cell chamber, and an electrolyte injected into the cell chamber. The electrode plate group includes a plurality of positive electrode plates and negative electrode plates arranged alternately, and separators arranged between the positive electrode plates and the negative electrode plates.

[0015] The lead-acid battery of the present invention is expected to have both high durability at high temperatures and a high effect of suppressing water loss in the electrolyte.

[0016] 1 is a partial cross-sectional view showing the structure of a lead-acid battery according to an embodiment of the present invention; FIG. 2 is a plan view showing a positive electrode current collector plate constituting the lead-acid battery according to an embodiment of the present invention;

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. In the following embodiments, technically preferable limitations are imposed for carrying out the present invention, but these limitations are not essential requirements for the present invention.

[0018] 1 , the flooded lead-acid battery of this embodiment includes a battery case 41 having a cell chamber, a plate assembly 1 housed in the cell chamber, a positive electrode terminal 14, a negative electrode terminal 24, an electrolyte (not shown) poured into the cell chamber, and a lid 43 fixed to the battery case 41 to close the top of the cell chamber. The plate assembly 1 includes a stack made up of a plurality of alternately arranged positive electrode plates 10 and negative electrode plates 20 and separators 30 disposed between the positive electrode plates 10 and the negative electrode plates 20, a positive electrode strap 13 connecting the positive electrode plates 10 of the stack, and a negative electrode strap 23 connecting the negative electrode plates 20 of the stack.

[0019] One electrode plate pack 1 is housed in one cell chamber, and the number of positive electrode plates 10 constituting the stack of the electrode plate pack 1 is equal to or less than the number of negative electrode plates 20. The number of positive electrode plates 10 may be the same as or greater than the number of negative electrode plates 20. The positive electrode plate 10 includes a positive electrode current collector and a positive electrode mixture containing a positive electrode active material. The positive electrode current collector has a rectangular lattice portion and ears 12 continuous with the lattice portion, and the positive electrode mixture is held in the lattice portion. The negative electrode plate 20 includes a negative electrode current collector and a negative electrode mixture containing a negative electrode active material. The negative electrode current collector has a rectangular lattice portion and ears 22 continuous with the lattice portion, and the negative electrode mixture is held in the lattice portion. The positive electrode mixture and the negative electrode mixture are filled in the openings of the grid portions of the positive electrode current collector plate and the negative electrode current collector plate, and cover the plate surfaces of the grid portions.

[0020] The stack of electrode plate pack 1 is placed in battery case 41 with the plate surfaces of the grid-like portions of positive electrode plates 10 and negative electrode plates 20 aligned vertically within battery case 41. The material and manufacturing method of positive electrode current collector plate 11 constituting positive electrode plate 10 will be described in detail later. The negative electrode current collector plate constituting negative electrode plate 20 is formed by continuous casting using a Pb—Ca—Sn alloy. Separator 30 is a porous film made of, for example, resin, glass, or the like, and may have pleated ribs protruding perpendicular to the base surface formed on a flat base (film).

[0021] The lugs 12 of the multiple positive electrode plates 10 are connected by positive electrode straps 13, and the lugs 22 of the multiple negative electrode plates 20 are connected by negative electrode straps 23. One end of a positive electrode terminal 14 is connected to the top of the positive electrode strap 13, and one end of a negative electrode terminal 24 is connected to the top of the negative electrode strap 23, with the other ends of the positive electrode terminal 14 and negative electrode terminal 24 penetrating a lid 43 that closes the opening of a battery case 41 and being exposed to the outside of a case body consisting of the battery case 41 and the lid 43. The electrolyte is dilute sulfuric acid with a specific gravity of 1.28 to 1.30 (calculated at 20°C).

[0022] [Regarding the Positive Electrode Plate] The positive electrode plate 10 has a positive electrode current collector plate 11 having a shape shown in FIG. 2 . The positive electrode current collector plate 11 has a rectangular lattice portion 110 and lugs 12 protruding from above the lattice portion 110. The lattice portion 110 has frame ribs forming the four sides of the rectangle and a plurality of inner ribs connected to the frame ribs and located inside the frame ribs. The frame ribs include an upper frame rib 111 located above the lattice portion 110 and extending in a horizontal direction (X direction) perpendicular to the stacking direction (Y direction) of the laminate and the up-down direction (Z direction) of the battery case; a lower frame rib 112 located below the lattice portion 110 and extending in the horizontal direction; and a pair of vertical frame ribs 113, 114 extending vertically in the up-down direction (Z direction) of the battery case. The multiple inner ribs include multiple vertical inner ribs 115 extending from each position of the upper frame rib toward the lower frame rib, and multiple horizontal inner ribs 116 connecting the pair of vertical frame ribs 113, 114. Furthermore, all openings 117 of the lattice portion 110 are filled with a positive electrode mixture, and a layer made of the positive electrode mixture exists on the entire front and back surfaces of the lattice portion 110. In other words, the positive electrode mixture is held in the lattice portion 110.

[0023] [Regarding the manufacturing method of the positive electrode current collector plate] Examples of manufacturing methods for the positive electrode current collector plate include a casting method using a mold, an expanding method for processing a rolled substrate, or a punching method. However, when a rolled substrate made of a Pb-Ca-Sn alloy (a lead alloy containing Ca and Sn as alloy components) is rolled, aging, overaging, and recrystallization occur competitively. Therefore, when a positive electrode current collector plate made of a Pb-Ca-Sn alloy is obtained by processing a rolled substrate (one that has a rolled texture), corrosion is likely to occur, and the mechanical strength is reduced due to corrosion, making it prone to deformation due to elongation of the lattice-shaped portion. In contrast, a positive electrode current collector plate obtained by a casting method is less likely to deform due to elongation of the lattice-shaped portion. Therefore, it is preferable that the positive electrode current collector plate made of a Pb-Ca-Sn alloy is obtained by a casting method, that is, one that does not have a rolled texture (no rolled texture exists). Examples of casting methods include gravity casting and continuous casting.

[0024] [Regarding the material of the positive electrode current collector plate] The positive electrode current collector plate 11 is manufactured by a casting method and is formed of a lead alloy containing 0.035% by mass to 0.08% by mass of Ca, 0.50% by mass to 1.0% by mass of Sn, 0.003% by mass to 0.035% by mass of Ag, more than 0.02% by mass to 0.02% by mass of Bi, more than 0% by mass to 0.001% by mass of Ba, and the remainder being lead and unavoidable impurities. The effects of each alloy component contained in the lead alloy are described below.

[0025] <Ca (Calcium)> The inclusion of calcium in the lead alloy forming the positive electrode current collector improves the mechanical strength of the positive electrode current collector. Specifically, when the positive electrode current collector is manufactured by a casting method using a lead alloy, calcium refines the crystal grains, thereby improving the mechanical strength of the manufactured positive electrode current collector. Furthermore, if the calcium content is too low, casting defects may occur. On the other hand, if the calcium content is too high, the required corrosion resistance may not be obtained. If the calcium content is in the range of 0.035% by mass to 0.08% by mass, the required performance in terms of both mechanical strength and corrosion resistance can be obtained. Furthermore, the Ca content is preferably in the range of 0.035% by mass to 0.07% by mass, and more preferably in the range of 0.035% by mass to 0.06% by mass.

[0026] <Sn (Tin)> The inclusion of tin in the lead alloy forming the positive electrode current collector plate improves the mechanical strength and corrosion resistance of the positive electrode current collector plate. Furthermore, increasing the oxygen generating overvoltage of the positive electrode current collector plate can suppress the generation of oxygen gas from the positive electrode plate due to water electrolysis. As a result, the loss of water content in the electrolyte can be suppressed. If the tin content is too low, these effects are not achieved. On the other hand, if the Sn content is too high, costs increase. A tin content of 0.50% by mass or more and 1.0% by mass or less ensures the required performance in terms of mechanical strength, corrosion resistance, oxygen generating overvoltage, and cost. Furthermore, the Sn content is preferably in the range of 0.55% by mass or more and 0.90% by mass or less, and more preferably in the range of 0.60% by mass or more and 0.80% by mass or less.

[0027] <Ag (Silver)> The inclusion of silver in the lead alloy forming the positive electrode current collector plate improves the mechanical strength, corrosion resistance, and creep resistance of the positive electrode current collector plate. If the silver content is too low, these effects are not exerted. On the other hand, if the silver content is too high, the oxygen generating overvoltage of the positive electrode current collector plate decreases, oxygen gas generation from the positive electrode plate due to water electrolysis becomes significant, and costs increase. If the silver content is in the range of 0.003% by mass or more and 0.035% by mass or less, required performance can be obtained in terms of all of the mechanical strength, corrosion resistance, creep resistance, oxygen generating overvoltage, and cost. In addition, the Ag content is preferably in the range of 0.010% by mass or more and 0.030% by mass or less, and more preferably in the range of 0.015% by mass or more and 0.025% by mass or less.

[0028] <Bi (Bismuth)> The inclusion of bismuth in the lead alloy forming the positive electrode current collector plate improves the creep resistance of the positive electrode current collector plate. If the bismuth content is too low, this effect is not achieved. On the other hand, if the bismuth content is too high, the oxygen generating overvoltage of the positive electrode current collector plate decreases, and oxygen gas generation from the positive electrode plate due to water electrolysis becomes significant. If the Bi content is in the range of more than 0 (= 0.0000 mass%) and 0.02 mass% or less, the required performance in terms of both creep resistance and oxygen generating overvoltage can be obtained. In addition, the bismuth content is preferably in the range of 0.0001 mass% to 0.010 mass%, and more preferably in the range of 0.0005 mass% to 0.005 mass%.

[0029] <Ba (Barium)> The inclusion of barium in the lead alloy forming the positive electrode current collector plate improves the mechanical strength and corrosion resistance of the positive electrode current collector plate. If the barium content is too low, these effects are not exerted. On the other hand, if the barium content is too high, costs increase. If the Ba content is in the range of more than 0 (= 0.000 mass%) and 0.001 mass% or less, the effects of improving the mechanical strength and corrosion resistance can be obtained while suppressing costs.

[0030] [Operations and Effects] The flooded lead-acid battery of the embodiment uses a positive electrode current collector plate 11 manufactured by a casting method and formed of a lead alloy containing 0.035% by mass to 0.08% by mass of Ca, 0.50% by mass to 1.0% by mass of Sn, 0.003% by mass to 0.035% by mass of Ag, more than 0.02% by mass to 0.02% by mass of Bi, more than 0% by mass to 0.001% by mass of Ba, with the remainder being lead and unavoidable impurities. This achieves both high high-temperature durability and a high suppression effect of water loss in the electrolyte, while also reducing costs. Note that the same operations and effects as flooded lead-acid batteries can be obtained with valve-regulated lead-acid batteries.

[0031] [Preparation of Test Batteries] Several flooded lead-acid batteries with the same structure as the flooded lead-acid battery of the embodiment were fabricated, each with a 5-hour rate capacity of 36 Ah, a B24 size, and a nominal voltage of 12 V, but using positive current collector plates made of different materials (lead alloy compositions). The battery case had six cell compartments. All batteries had the same configuration except for the positive current collector plate. First, positive current collector plates No. 1 to No. 30 were fabricated by gravity casting using lead alloys with alloy compositions shown in Table 1. During this process, a casting defect occurred in the positive current collector No. 2. Specifically, the collector was deformed when transported to the next process after casting, making it unable to maintain its shape. All positive current collector plates except No. 2 were usable.

[0032] Next, a negative electrode current collector plate having substantially the same shape as the positive electrode current collector plate 11 was produced by continuous casting using a lead alloy containing 0.09% by weight of Ca, 0.4% by weight of Sn, 0.001% by weight of Ag, and 0.005% by weight of Bi, with the remainder being lead and unavoidable impurities. Next, a positive electrode mixture paste was produced by kneading lead powder containing lead monoxide as the main component with water and dilute sulfuric acid, followed by further mixing and kneading with necessary additives (i.e., by a conventional method). A negative electrode mixture paste was also produced by kneading lead powder containing lead monoxide as the main component with water and dilute sulfuric acid, followed by further mixing and kneading with necessary additives (i.e., by a conventional method). The resulting positive electrode mixture paste was uniformly applied and filled over the entire surface of the grid-shaped portion of the positive electrode current collector plate, and then preheated, dried, and aged and dried by conventional methods to produce a positive electrode plate (before chemical conversion). The obtained negative electrode mixture paste was uniformly applied and filled onto the entire surface of the grid-shaped portion of the negative electrode current collector plate, and then preheating and drying and aging were carried out in a conventional manner to prepare a negative electrode plate (before chemical conversion).

[0033] Next, for each sample, the pre-chemically treated negative electrode plates were placed in a polyethylene separator bag, and seven separators containing pre-chemically treated negative electrodes and six pre-chemically treated positive electrodes were alternately stacked to obtain a laminate. Next, using a cast-on-strap (COS) casting machine, straps, intermediate poles, and terminal poles were formed on the pre-chemically treated positive and negative electrodes of each laminate to obtain a plate assembly. Six of these plate assemblies were prepared for each sample and placed in each cell chamber of a battery case. The pre-chemically treated lead-acid batteries (No. 1, No. 3, No. 4, No. 5, No. 6, No. 7, No. 8, No. 9, No. 10, No. 11, No. 12, No. 13, No. 14, No. 15, No. 16, No. 17, No. 18, No. 19, No. 20, No. 21, No. 22, No. 23, No. 24, No. 25, No. 26, No. 27, No. 28, No. 29, No. 30) were assembled by the usual process of resistance welding the intermediate poles between adjacent cell chambers, heat welding the battery case to the lid, injecting electrolyte into each cell chamber through each inlet, and sealing the inlet with a plug or other suitable means. The electrolyte was injected by injecting dilute sulfuric acid with a specific gravity of 1.250 (equivalent at 20°C) into each cell chamber. Thereafter, the container was subjected to formation so that the specific gravity of the electrolyte after the formation was 1.285 (converted value at 20° C.), thereby obtaining two lead-acid batteries for each of No. 1 and No. 3 to No. 30.

[0034] [Measurement of lead alloy composition] One of the two lead-acid batteries obtained was disassembled, and the alloy composition of the positive electrode current collector plate (after chemical formation) was measured. Specifically, first, the electrode plate group was removed from the cell chamber (third cell chamber) two cells away from the cell chamber (first cell chamber) containing the electrode plate group having the positive electrode terminal pole, and the disassembly was performed. The positive electrode plate disposed on the fourth cell chamber side was removed. Next, the edge of the positive electrode current collector plate was cut from the removed positive electrode plate, and the surface of the edge was polished to produce a metallic glossy surface. Next, this polished edge was used as a sample and quantitative analysis was performed using a conventionally known method using a solid-state optical emission spectrometer (OES: "PDA-7000" manufactured by Shimadzu Corporation).

[0035] [Testing and Evaluation] The remaining one of the two lead-acid batteries was used to evaluate high-temperature durability by a light-load life test specified in "JIS D 5301:2019" at 75°C. Specifically, each lead-acid battery was placed in a water bath at 75°C and repeatedly discharged (discharge current 25.0±0.1 A for 240±1 seconds) and charged (14.80±0.03 V for 600±1 seconds). Every 480 cycles, the amount of electrolyte loss (amount of water lost in the electrolyte) was measured, and purified water was replenished in an amount equal to the amount of electrolyte loss. For life assessment, each lead-acid battery was continuously discharged for 30 seconds at the rated cold cranking current. The end of life was determined when the voltage at 30 seconds was 7.2 V or less. The mass of the battery was measured every 480 cycles, and the amount of electrolyte loss was calculated as the mass loss from the pre-test. The cumulative amount of liquid loss (the sum of the amounts of liquid loss calculated every 480 cycles) was then measured after 1,920 cycles. For batteries that reached the end of their life before the number of cycles (number of repeated discharges and charges) reached 1,920, the cumulative amount of liquid loss was not measured.

[0036] The results of these tests, along with the composition of the lead alloy forming the positive electrode current collector plate of each lead-acid battery and the cost of that lead alloy, are shown in Table 1. The cost of the lead alloy was judged as "◎" if it was the same as or 1.05 times or less than the cost of the lead alloy used in No. 1, "◯" if it was 1.05 times or more but less than 1.08 times, "△" if it was 1.08 times or more but less than 1.10 times, and "×" if it was 1.10 times or more.

[0037] Furthermore, the required high-temperature durability test results were evaluated as follows: for less than 2000 cycles, an "X" was given; for 2000 to 4000 cycles, an "O" was given; and for more than 4000 cycles, an "◎" was given. The electrolyte loss characteristics (whether electrolyte loss was suppressed) were evaluated as follows: for a cumulative electrolyte loss of 350 g or less at 1920 cycles, an "◎" was given; for more than 350 g but less than 400 g, an "O" was given; and for 400 g or more, an "X" was given. An overall evaluation based on the test results was performed as follows: if all evaluations were "◎," an "◎" was given. If any of the high-temperature durability, electrolyte loss characteristics, and cost were evaluated as "○," an "○" was given. If any of the high-temperature durability, electrolyte loss characteristics, and cost were evaluated as "△," an "△" was given. If any of the high-temperature durability, electrolyte loss characteristics, and cost were evaluated as "×," an "X" was given.

[0038]

[0039] The results in Table 1 reveal the following. <No. 1> The lead-acid battery No. 1 is a conventional example used as a cost benchmark. In a light-load life test at 75°C (a test to evaluate high-temperature durability), the battery life was 1,920 cycles and the cumulative electrolyte loss was 400 g. In the lead-acid battery No. 1, the calcium content of the lead alloy forming the positive current collector plate was 0.090% by mass, which is greater than the upper limit of the calcium content of the lead alloy (hereinafter referred to as the "first lead alloy") forming the positive current collector plate of the lead-acid battery of the first embodiment. Furthermore, the tin content of the lead alloy forming the positive current collector plate was 1.10% by mass, which is greater than the upper limit of the tin content of the first lead alloy. Furthermore, the lead alloy forming the positive current collector plate did not contain silver, an essential component of the first lead alloy. Furthermore, the bismuth content of the lead alloy forming the positive current collector plate was 0.0200 mass%, which is higher than the upper limit of the bismuth content of the lead alloy (hereinafter referred to as the "second lead alloy") forming the positive current collector plate of the lead-acid battery of the second embodiment. As described above, the lead-acid battery No. 1 had a positive current collector plate with a lead alloy containing more calcium than the first lead alloy and no silver, resulting in insufficient corrosion resistance of the positive current collector plate, and a slightly higher bismuth content (more than the second lead alloy), resulting in insufficient performance in suppressing electrolyte loss.

[0040] <No. 2> The positive current collector plate of No. 2 was formed from a lead alloy in which the contents of tin, silver, bismuth, and barium among the alloy components were within the ranges of the lead alloy (hereinafter referred to as the "fifth lead alloy") that forms the positive current collector plate of the lead-acid battery of the fifth embodiment, and the calcium content was lower than the lower limit of the calcium content of the lead alloy (hereinafter referred to as the "fourth lead alloy") that forms the positive current collector plate of the lead-acid battery of the fourth embodiment. The positive current collector plate of No. 2 was formed from a lead alloy in which the calcium content was 0.030 mass%, which was lower than the lower limit of the calcium content of the fourth lead alloy, and it is believed that this was the reason for the casting defects.

[0041] <Nos. 3 to 8> In the lead-acid batteries Nos. 3 to 8, the lead alloy forming the positive current collector plate has the same tin, silver, and bismuth contents within the ranges of the lead alloy forming the positive current collector plate of the lead-acid battery of the third embodiment (hereinafter referred to as the "third lead alloy") and the lead alloy forming the positive current collector plate of the lead-acid battery of the sixth embodiment (hereinafter referred to as the "sixth lead alloy"), but the barium content is 0.001% by mass (within the range of the sixth alloy) or 0.000% by mass (within the range of the third alloy), and the calcium content is different (within the range of the first and fourth alloys).

[0042] Lead-acid batteries No. 3 to No. 8 exhibited excellent high-temperature durability of over 2,500 cycles and particularly excellent electrolyte loss characteristics, with a cumulative electrolyte loss of less than 350 g. Furthermore, compared to battery No. 1, the lead alloy forming the positive current collector plate had a higher silver content but lower calcium and tin contents, thereby reducing manufacturing costs. Since tin is particularly expensive, reducing the tin content by about half significantly reduced material costs. Lead-acid batteries No. 3, No. 5 to No. 8 had lead alloys forming the positive current collector plate with the same tin, silver, bismuth, and barium contents (within the sixth alloy range) but different calcium contents within the fourth alloy range. The calcium content of the lead alloy forming the positive current collector plate of battery No. 7 was outside the sixth alloy range, while the calcium content of the lead alloy forming the positive current collector plate of battery No. 8 was outside the fifth alloy range.

[0043] Among the lead-acid batteries No. 3, No. 5 to No. 8, No. 3, No. 5, and No. 6 had positive current collector plates formed of lead alloys containing not only tin, silver, bismuth, and barium, but also calcium within the range of the sixth alloy, and thus exhibited particularly excellent high-temperature durability of 4,000 cycles or more and particularly excellent liquid loss characteristics with a cumulative liquid loss of 350 g or less. Furthermore, when comparing No. 4 and No. 5, which differ only in the barium content of the lead alloy forming the positive current collector plate, the lead-acid battery No. 5, which had a positive current collector plate formed of a lead alloy containing 0.001% by mass of barium, had better high-temperature durability than the lead-acid battery No. 4, which had a positive current collector plate formed of a lead alloy containing no barium (0.000% by mass).

[0044] <No. 5, No. 9 to No. 15> In the lead-acid batteries No. 5 and No. 9 to No. 14, the lead alloy forming the positive current collector plate has a calcium, silver, bismuth, and barium content within the range of the fourth alloy, but a different tin content. In the lead-acid battery No. 15, the lead alloy forming the positive current collector plate has a calcium, bismuth, and barium content within the range of the fourth alloy, but a silver and tin content outside the range of the fourth alloy. Of the lead-acid batteries No. 5, No. 9 to No. 15, the lead-acid batteries No. 5 and No. 10 to No. 14 have positive current collector plates formed from lead alloys whose calcium, silver, bismuth, and barium content as well as tin content are within the range of the fourth alloy, thereby achieving excellent high-temperature durability of more than 3,000 cycles and excellent liquid loss characteristics with a cumulative liquid loss of less than 400 g. The lead-acid battery No. 15 had a significantly higher manufacturing cost because the tin content of the alloy forming the positive electrode current collector was higher than the upper limit of the fourth alloy.

[0045] Among the lead-acid batteries No. 5 and No. 10 to No. 14, the lead-acid batteries No. 5 and No. 12 to No. 14 have positive current collector plates formed of a lead alloy in which the calcium, silver, bismuth, and barium contents are within the range of the sixth alloy and the tin content is within the range of 0.060 mass% to 1.0 mass%, thereby achieving even better high-temperature durability of 4,000 cycles or more and particularly excellent liquid loss characteristics with a cumulative liquid loss of 350 g or less. Among the lead-acid batteries No. 5 and No. 12 to No. 14, the lead-acid batteries No. 5 and No. 12 have positive current collector plates formed of a lead alloy in which the contents of not only calcium, silver, bismuth, and barium but also tin are within the range of the sixth alloy, thereby achieving lower costs than the lead-acid batteries No. 13 and No. 14 and achieving particularly excellent high-temperature durability of 4,500 cycles or more, which is higher than the lead-acid batteries No. 13 and No. 14. In other words, by having a positive electrode current collector plate formed of a lead alloy within the range of the sixth alloy, cost reduction effects, particularly excellent high temperature durability, and excellent liquid reduction characteristics were obtained.

[0046] <No. 5, No. 16 to No. 23> In the lead-acid batteries No. 5, No. 16 to No. 23, the lead alloy forming the positive current collector plate has a calcium, tin, bismuth, and barium content within the range of the fourth alloy, but a different silver content. Of the lead-acid batteries No. 5, No. 16 to No. 23, the lead-acid batteries No. 5, No. 19 to No. 22 have a positive current collector plate formed from a lead alloy whose calcium, tin, bismuth, and barium content as well as silver content are within the range of the fourth alloy, thereby achieving excellent high-temperature durability of more than 3,000 cycles and particularly excellent liquid loss characteristics with a cumulative liquid loss of 350 g or less.

[0047] Among the lead-acid batteries No. 5 and No. 19 to No. 22, the lead-acid batteries No. 5, No. 19, and No. 20 had positive current collector plates formed of a lead alloy containing not only calcium, tin, bismuth, and barium but also silver within the range of the sixth alloy, thereby achieving particularly excellent high-temperature durability of 4,500 cycles or more and significant cost reduction effects. Furthermore, the lead-acid batteries No. 5, No. 20 to No. 22 had positive current collector plates formed of a lead alloy containing calcium, tin, bismuth, and barium within the range of the sixth alloy and a silver content within the range of 0.020% by mass to 0.035% by mass, thereby achieving significantly excellent high-temperature durability of 4,800 cycles or more.

[0048] <No. 5, No. 24 to No. 30> In the lead-acid batteries No. 5 and No. 24 to No. 30, the lead alloy forming the positive current collector plate has calcium, tin, silver, and barium contents within the range of the fifth alloy, but a different bismuth content. Of the lead-acid batteries No. 5 and No. 24 to No. 30, the lead-acid batteries No. 5 and No. 25 to No. 29 have positive current collector plates formed from lead alloys whose calcium, tin, silver, and barium contents are within the range of the fifth alloy and whose bismuth contents are within the range of the fourth alloy, thereby achieving excellent high-temperature durability of 3,500 cycles or more and excellent liquid loss characteristics with a cumulative liquid loss of less than 400 g. Of the lead-acid batteries No. 5 and No. 25 to No. 29, the lead-acid batteries No. 5, No. 26, and No. 27 had positive electrode current collector plates formed from a lead alloy containing not only calcium, tin, silver, and barium, but also bismuth within the range of the sixth alloy, and therefore achieved particularly excellent high-temperature durability of more than 4,500 cycles, significant cost reduction effects, and particularly excellent liquid loss characteristics with a cumulative liquid loss of 350 g or less.

[0049] In manufacturing No. 24 lead-acid battery, the positive electrode current collector was formed using a lead alloy obtained by completely removing Bi from a commercially available lead alloy (containing trace amounts of Bi). This bismuth removal process is costly, resulting in high costs. Furthermore, No. 24 lead-acid battery is an example using a positive electrode current collector made of the lead alloy described in Patent Document 1, and its high-temperature durability was short at 1,917 cycles. When the battery was disassembled after the test, significant growth was confirmed in the grid-like portion of the positive electrode current collector. Therefore, it is believed that the short life was caused by the positive electrode mixture falling off the grid-like portion of the positive electrode current collector.

[0050] REFERENCE SIGNS LIST 1 electrode plate group 10 positive electrode plate 11 positive electrode current collector plate 12 ear portion of positive electrode current collector plate 110 grid portion of positive electrode current collector plate 111 upper frame 112 lower frame 113 vertical frame 114 vertical frame 115 vertical inner frame 116 horizontal inner frame 117 opening 13 positive electrode strap 14 positive electrode terminal 20 negative electrode plate 22 ear portion of negative electrode current collector plate 23 negative electrode strap 24 negative electrode terminal 30 separator 41 battery case 43 lid

Claims

DEPCT671. Lead-acid battery assembled with: electrolyte and laminate components, where the laminate components include a number of positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes a positive electrode mixture with positive working material and a positive electrode collector plate with a grid component that holds the positive electrode mixture and the positive electrode collector plate. The positive electrode mixture and the positive electrode collector plate are constructed from a lead alloy containing 0.035% by mass or more and 0.08% by mass or less of Ca, 0.50% by mass or more and 1.0% by mass or less of Sn, 0.003% by mass or more and 0.035% by mass or less of Ag, more than 0% by mass and 0.02% by mass or less of Bi, and a balance with lead and unavoidable impurities.2.A lead-acid battery consists of: the electrolyte and the laminate component, where the laminate component includes a number of positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes an anode mixture with positive working material and an anode collector plate with a grid component that holds the anode mixture. The anode mixture and the anode collector plate are constructed from a lead alloy containing 0.035% by mass or more and 0.07% by mass or less of Ca, 0.55% by mass or more and 0.9% by mass or less of Sn, 0.010% by mass or more and 0.030% by mass or less of Ag, 0.0001% by mass or more and 0.010% by mass or less of Bi, and a balance with lead and unavoidable impurities.A lead-acid battery consists of: the electrolyte and the laminate component, where the laminate component includes a number of positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes an anode mixture with positive working material and an anode collector plate with a grid component that holds the anode mixture. The anode mixture and the anode collector plate are constructed from a lead alloy containing 0.035% by mass or more and 0.06% by mass or less of Ca, 0.60% by mass or more and 0.8% by mass or less of Sn, 0.015% by mass or more and 0.025% by mass or less of Ag, 0.0005% by mass or more and 0.005% by mass or less of Bi, and a balance with lead and unavoidable impurities.A lead-acid battery consists of: the electrolyte and the laminate component, where the laminate component includes a number of positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes an anode mixture with positive working material and an anode collector plate with a grid component that holds the anode mixture. The anode mixture and the anode collector plate are constructed from a lead alloy containing 0.035% by mass or more and 0.08% by mass or less of Ca, 0.50% by mass or more and 1.0% by mass or less of Sn, 0.003% by mass or more and 0.035% by mass or less of Ag, greater than 0% by mass and 0.02% by mass or less of Bi, greater than 0% by mass and 0.001% by mass or less of Ba, and a balance with unavoidable lead and impurities.A lead-acid battery consists of: the electrolyte and the laminate component, where the laminate component includes a number of positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes an anode mixture with positive working material and an anode collector plate with a grid component that holds the anode mixture. The anode mixture and the anode collector plate are constructed from a lead alloy containing 0.035% by mass or more and 0.07% by mass or less of Ca, 0.55% by mass or more and 0.9% by mass or less of Sn, 0.010% by mass or more and 0.030% by mass or less of Ag, 0.0001% by mass or more and 0.010% by mass or less of Bi, greater than 0% by mass and 0.001% by mass or less of Ba, and a balance with lead and unavoidable impurities.6.A lead-acid battery consists of: an electrolyte and a laminate component, where the laminate component includes several positive and negative electrode plates arranged alternately and a separator arranged between the positive and negative electrode plates. The positive electrode plate includes a positive electrode mixture with a positive working material and a positive electrode collector plate with a grid section that holds the positive electrode mixture. Both the positive electrode mixture and the positive electrode collector plate are made from a lead alloy.

7. Lead-acid batteries under any one of the claims 1 to 6 in which the anode collector plates are obtained by casting;

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