Liquid lead-acid battery

Abstract

To provide a novel technology capable of improving a positive electrode use rate of a liquid type lead storage battery which has a positive electrode plate having a positive electrode mixture, including a positive electrode active substance, held on a current collector plate without spoiling durability of the positive electrode mixture.SOLUTION: A liquid type lead storage battery comprises a battery container 41 having a cell chamber, an electrode plate group 1 housed in the cell chamber, and an electrolyte injected into the cell chamber, and the electrolyte is diluted sulfuric acid. The electrode plate group has pluralities of positive electrodes 10 and negative electrodes 20 arranged alternately, and a separator arranged between the positive electrodes 10 and negative electrodes 20, wherein the positive electrode plates 10 have a positive electrode mixture, including positive electrode active substance, held on current collectors, and the positive electrode active substance includes tetragonal lead dioxide; and a c-axial lattice constant c and an a-axial lattice constant a of the tetragonal lead dioxide satisfy 0.6822≤c / a≤0.6830, and a lattice volume of the tetragonal lead dioxide is 83.25 Å3 to 83.38 Å3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A typical 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 is a current collector holding a positive electrode mixture containing a positive electrode active material, and the negative plate is 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, with the spread of idle-stop vehicles, there has been a demand for even higher performance flooded lead-acid batteries. In particular, increasing the utilization rate of the positive electrode active material (hereinafter also referred to as "positive electrode utilization rate") not only increases discharge capacity but also enables a reduction in the amount of lead used, thereby achieving weight reduction and cost reduction. Therefore, research and development into this field is being conducted by those skilled in the art using various approaches. One known method for increasing the positive electrode utilization rate is to reduce the density of the positive electrode mixture containing the positive electrode active material. By reducing the density of the positive electrode mixture, the pore volume of the positive electrode mixture increases, which increases the contact between the active material and the electrolyte, thereby improving the positive electrode utilization rate.

[0004] The positive electrode active material expands and contracts repeatedly with each charge and discharge because the volume per molecule differs between lead dioxide in the charged state and lead sulfate in the discharged state. As this expansion and contraction continues, the bonds between the particles in the positive electrode mixture gradually break down, causing it to become fluid (soften) and eventually fall off the positive electrode plate. If the density of the positive electrode mixture decreases, this phenomenon (softening and falling off of the positive electrode mixture) becomes more likely to progress, which can significantly reduce the lifespan of flooded lead-acid batteries. Therefore, methods have been proposed to prevent this softening and falling off of the positive electrode mixture, maintaining durability while improving the positive electrode utilization rate.

[0005] Patent Document 1 describes a positive electrode for a flooded lead-acid battery in which the amount of tribasic lead sulfate in the unformed active material is 25 to 30 mass %, the amount of metallic lead is less than 5 mass %, and the active material density is 3.8 × 10 3 kg / m 3 It states that the following shall be done. Patent Document 2 describes a method of preparing a paste by kneading lead powder containing 10 to 20% by weight of minium, water, and dilute sulfuric acid, and then applying the paste to a grid at a packing density of 4.3 to 5.3 g / mL. Patent Document 3 describes that tetrabasic lead sulfate with large crystal grain size is formed in the active material layer of a paste-type positive electrode plate in an unformed state, and then the plate is formed into a chemical compound to extend the battery life, and that carbon powder is added to improve the utilization rate of the active material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4376514 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-198041 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-229920 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, in the method of increasing the positive electrode utilization rate by decreasing the density of the positive electrode mixture, decreasing the density leads to decreased durability, so measures such as the use of additives are essential, and there is room for improvement in the method of achieving both improved durability of the positive electrode mixture and improved positive electrode utilization rate. An object of the present invention is to provide a new technology that can improve the positive electrode utilization rate without impairing the durability of a positive electrode mixture in a flooded lead-acid battery having a positive electrode plate in which a positive electrode mixture containing a positive electrode active material is held on a current collector plate. [Means for solving the problem]

[0008] In order to solve the above problems, one aspect of the present invention provides a flooded lead-acid battery having the following features (a) to (c). (a) A battery comprising a battery case having a cell chamber, a plate assembly housed in the cell chamber, and an electrolyte injected into the cell chamber. The electrolyte is dilute sulfuric acid. The plate assembly has 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 is a positive electrode mixture containing a positive electrode active material held by a current collector. (b) the positive electrode active material includes tetragonal lead dioxide; (c) the lattice constant c in the c-axis direction of the tetragonal lead dioxide and the lattice constant a in the a-axis direction satisfy the relationship 0.6822≦c / a≦0.6830, and the lattice volume of the tetragonal lead dioxide is 83.25 Å 3 More than 83.38Å 3 The following is the result. The space group of tetragonal lead dioxide is P42 / mnm, and the lattice constant is defined as a = b ≠ c. Although the c / a value is used in this specification, it can also be interpreted as c / b because the lattice constants a and b have the same value. The structural volume is expressed as a × b × c. [Effects of the Invention]

[0009] According to the present invention, by adjusting the lattice constant ratio and lattice volume of the tetragonal lead dioxide contained in the positive electrode active material to fall within specific ranges, it becomes possible to improve the positive electrode utilization rate without impairing the durability of the positive electrode mixture. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a partial cross-sectional view showing the structure of a flooded lead-acid battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] 1, the flooded lead-acid battery of this embodiment includes a plate assembly 1 in which a plurality of positive electrode plates 10 and negative electrode plates 20 are alternately stacked with ribbed separators 30 interposed therebetween. The plate assembly 1 is housed in a cell chamber of a battery case 41 together with an electrolyte (not shown) so that the stacking direction is along the horizontal direction (i.e., so that the plate surfaces of the positive electrode plates 10 and negative electrode plates 20 are along the vertical direction), and is immersed in the electrolyte within the cell chamber of the battery case 41. That is, the flooded lead-acid battery of this embodiment has a plate pack 1 and a battery case 41 equipped with a cell chamber that houses the plate pack 1 together with an electrolyte, with one plate pack 1 housed in one cell chamber, and the number of positive plate plates 10 constituting the plate pack 1 being equal to or less than the number of negative plate plates 20. The number of positive plate plates 10 may be the same as the number of negative plate plates 20, or may be greater than the number of negative plate plates 20.

[0013] 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 tab portions 11 continuous with the lattice portion, and the positive electrode mixture is held in the lattice portion. The positive electrode active material includes tetragonal lead dioxide, and the lattice constant c in the c-axis direction of this tetragonal lead dioxide and the lattice constant a in the a-axis direction satisfy the relationship 0.6822≦c / a≦0.6830, and the lattice volume of this tetragonal lead dioxide is 83.25 Å. 3 More than 83.38Å 3 The following is the result. 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 active material containing metallic lead. The negative electrode current collector has a rectangular lattice portion and tabs 21 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 respective lattice portions and are present on both plate surfaces of the lattice portions.

[0014] The positive electrode current collector constituting the positive electrode plate 10 is formed by gravity casting using a Pb-Sn alloy. The negative electrode current collector constituting the negative electrode plate 20 is formed by continuous casting using a Pb-Ca alloy. Other manufacturing methods for the positive electrode current collector and the negative electrode current collector include a punching method using a rolled lead alloy plate and an expanding method using a rolled lead alloy plate. The separator 30 is a porous film made of, for example, resin, glass fiber, or the like, and may have pleated ribs protruding perpendicular to the base surface formed on a flat base (film).

[0015] The lugs 11 of the multiple positive plates 10 are connected by a positive electrode strap 13, and the lugs 21 of the multiple negative plates 20 are connected by a negative electrode strap 23. The positive electrode strap 13 is connected to one end of a positive electrode terminal 15, and the negative electrode strap 23 is connected to one end of a negative electrode terminal 25. The other ends of the positive electrode terminal 15 and the negative electrode terminal 25 penetrate a lid 43 that closes the opening of a battery case 41, and are exposed to the outside of the case body of the flooded lead-acid battery, which is made up of the battery case 41 and the lid 43. The electrolyte contains dilute sulfuric acid and aluminum ions of 20 mmol / L or more and 200 mmol / L or magnesium ions of 25 mmol / L or more and 250 mmol / L or less, and the sulfuric acid concentration of the electrolyte is 1280 g / L or more and 1300 g / L or less (specific gravity at 20°C is 1.28 or more and 1.30 or less).

[0016] In the flooded lead-acid battery of this embodiment, the lattice constant ratio and lattice volume of the tetragonal lead dioxide contained in the positive electrode active material are within the above-mentioned specific ranges, thereby achieving both excellent durability of the positive electrode mixture and excellent positive electrode utilization. Furthermore, by including 20 mmol / L to 200 mmol / L of aluminum ions or 25 mmol / L to 250 mmol / L of magnesium ions in the dilute sulfuric acid electrolyte, charge acceptance is improved compared to when these ions are not included, and sulfation, which is a cause of deterioration of the positive and negative electrode plates, can be suppressed. [Example]

[0017] <Preparation of test battery> As flooded lead-acid batteries having the same structure as the flooded lead-acid battery of the embodiment, two flooded lead-acid batteries each of Samples No. 1 to No. 10 were fabricated. Specifically, a JIS B20-sized battery case with a single cell compartment was prepared, and a single electrode plate group was placed in the cell compartment to fabricate a flooded lead-acid battery (operating voltage: 2 V, rated capacity: 32 Ah) with a single cell compartment. Samples 1 to 10 of the flooded lead-acid batteries all had the same configuration, except for the positive electrode paste used. First, JIS standard B20 size current collector plates made of Pb—Sn alloy were prepared as positive and negative current collector plates. Next, the grid portion of the positive electrode current collector plate was filled with a positive electrode paste prepared by the following method for each sample, and then subjected to a drying and aging process to obtain a pre-chemically formed positive electrode plate.

[0018] The positive electrode paste used in No. 1 was prepared in the following manner. First, 2000 g of lead powder, primarily composed of lead monoxide, was mixed with 325 g of water and 150 g of sulfuric acid with a specific gravity of 1.37. Next, the resulting mixture was mixed with the necessary additives, as in conventional methods, and mixed together to obtain a positive electrode mixture paste. The positive electrode paste used in No. 2 was prepared in the same manner as No. 1, except that the amount of water added was 350 g and the amount of sulfuric acid added was 175 g. The positive electrode paste used in No. 3 was prepared in the same manner as No. 1, except that the amount of water added was 275 g. The positive electrode paste used in No. 4 was prepared in the same manner as No. 1, except that the amount of sulfuric acid added was 200 g. The positive electrode paste used in No. 5 was prepared in the same manner as No. 1, except that the amount of sulfuric acid added was 225 g.

[0019] The positive electrode paste used in No. 6 was prepared in the same manner as No. 1, except that the amount of water added was 300 g and the amount of sulfuric acid added was 175 g. The positive electrode paste used in No. 7 was prepared in the same manner as No. 1, except that the amount of sulfuric acid added was 175 g. The positive electrode paste used in No. 8 was prepared in the same manner as No. 1, except that the amount of water added was 300 g and the amount of sulfuric acid added was 200 g. The positive electrode paste used in No. 9 was prepared in the same manner as No. 1, except that the amount of water added was 275 g and the amount of sulfuric acid added was 200 g. The positive electrode paste used in No. 10 was prepared in the same manner as No. 1, except that the amount of water added was 275 g and the amount of sulfuric acid added was 225 g.

[0020] The grid-shaped portion of the negative electrode current collector was filled with lead paste prepared by a conventional method using the following composition. The composition for the negative electrode active material paste was a mixture of lead powder, cut polyester fiber, carbon black, lignin, and barium sulfate. After filling, the negative electrode was subjected to conventional processing to obtain a pre-chemically formed negative electrode plate. Next, the unformed negative electrode plates were placed in a polyethylene separator bag, and seven separators containing unformed negative electrode plates and six unformed positive electrode plates were alternately stacked to obtain two stacks for each sample. Next, the lugs of the unformed positive electrode plates and the lugs of the unformed negative electrode plates of the stacks were welded together with a gas burner, respectively, to obtain two electrode plate groups for each sample.

[0021] Next, the cell chamber of the prepared battery (space volume: 706.86 cm3 After placing one electrode group in the container, 370 mL (enough to completely immerse the electrode group) of electrolyte, made of dilute sulfuric acid with a specific gravity of 1.23 and containing 32 g / L of aluminum sulfate, was added. The aluminum ion concentration in this electrolyte was 93.5 mmol / L (= 32 / 342.14 = 0.0935 mol / L). Next, the battery container was formed with a charging quantity of electricity of 230% of the theoretical capacity of the positive electrode, to obtain two flooded lead-acid batteries No. 1 to No. 10.

[0022] <Identifying the crystal structure of the positive electrode active material> Each fully charged flooded lead-acid battery was immediately disassembled. First, the positive electrode plate located in the center of the stack was washed with water and dried. The positive electrode mixture was then peeled off from the grid-like portion. The peeled positive electrode mixture was then crushed in a mortar to a particle size of 3 μm or less to obtain a powder sample. The resulting powder sample was loaded into a vanadium sample holder. This sample holder was transported to the measurement room of the J-PARC High Intensity Proton Accelerator Research Complex in Tokai, Ibaraki Prefecture, and set on the beamline BL20 (iMATERIA). Neutron diffraction measurements were performed with a maximum measurement d value of 5 Å and a maximum diffraction intensity exceeding at least 10,000 counts.

[0023] The obtained diffraction data were subjected to Rietveld analysis using z-Rietveld software to determine the lattice constant ratio (c / a) and lattice volume (V) of the tetragonal lead dioxide contained in the positive electrode active material. This analysis was performed until the reliability factor Rwp, which represents the difference between the analytical value and the measured value, was 10% or less, assuming that the positive electrode active material contains a mixture of two phases of lead dioxide: tetragonal and orthorhombic. Diffraction data can be obtained using a commonly used powder X-ray diffractometer. However, to avoid the effects of sample holder packing and preferred crystal orientation, it is preferable to use a transmission method with a Debye-Scherrer optical system or a neutron beam, which is less susceptible to the effects of orientation.

[0024] <Test to check the positive electrode utilization rate (the utilization rate of the positive electrode active material)> Using another one of the resulting flooded lead acid batteries, a test was carried out to examine the positive electrode utilization rate by the following method. In accordance with JIS D 5301, each flooded lead-acid battery was placed in a water tank at 25°C and discharged at a constant current of 5 hours until the end voltage reached 10.5 V. The discharge capacity at which 10.5 V was reached was divided by the theoretical capacity, and the result was multiplied by 100 to obtain the positive electrode utilization rate (%) of each flooded lead-acid battery.

[0025] <Durability test> In accordance with the heavy-load life test described in JIS D 5301 9.5 (b), fully charged flooded lead-acid batteries were discharged to 40% depth of discharge in 1 hour at an ambient temperature of 40°C, and then charged at a 10-hour rate current to 125% of the discharge capacity. This cycle was repeated 24 times. The 25th cycle was used as a reference discharge, where the batteries were discharged to an end voltage of 10.2 V and then charged at a 10-hour rate current to 140% of the discharge capacity. After 25 cycles, the flooded lead-acid batteries were removed and the electrolyte lost during the 25th cycle was replenished. This charge-discharge cycle test was continued until the discharge capacity at the 25th cycle was less than 50% of the 5-hour rate capacity of each flooded lead-acid battery. The number of cycles up to that point was considered the battery's life.

[0026] These test results are shown in Table 1, along with the positive electrode composition of each flooded lead-acid battery (the mixture of water and sulfuric acid in the paste, the lattice constant ratio c / a of tetragonal lead dioxide, and the lattice volume V).

[0027] [Table 1]

[0028] The results in Table 1 reveal the following: The lattice constant ratio c / a of the tetragonal lead dioxide contained in the positive electrode active material is 0.6822 or more and 0.6830 or less, and the lattice volume V is 83.25 Å 3 More than 83.38Å 3The No. 2, No. 4, No. 6 to No. 9 flooded lead-acid batteries, which met both of the following criteria, had a positive electrode utilization rate of 44.0% or more and a lifespan of 120 cycles or more, demonstrating high durability of the positive electrode mixture and high positive electrode utilization rate. In addition, the lattice constant ratio c / a is 0.6824 or more and 0.6827 or less, and the lattice volume V is 83.25 Å 3 More than 83.38Å 3 The No. 4 and No. 6 to No. 8 flooded lead-acid batteries, which met both of the following criteria, had a positive electrode utilization rate of 45.0% or more and a lifespan of 123 cycles or more, demonstrating higher durability of the positive electrode mixture and positive electrode utilization rate.

[0029] In contrast, the lattice constant ratio c / a is between 0.6822 and 0.6830, and the lattice volume V is 83.25 Å. 3 More than 83.38Å 3 The No. 1, No. 3, No. 5, and No. 10 flooded lead-acid batteries that did not satisfy any of the following conditions did not satisfy either a positive electrode utilization rate of 44.0% or more or a lifespan of 120 cycles or more, and were inferior in either the durability of the positive electrode mixture or the positive electrode utilization rate. From the above, the lattice constant ratio c / a is between 0.6822 and 0.6830, and the lattice volume V is 83.25 Å. 3 More than 83.38Å 3 It was confirmed that by using a positive electrode active material containing tetragonal lead dioxide that satisfies both of the following conditions, the positive electrode utilization rate can be improved without impairing the durability of the positive electrode mixture. [Explanation of symbols]

[0030] 1 Plate group 10 Positive electrode plate 11 Positive electrode current collector lug 13 Positive strap 15 Positive terminal 20 negative electrode plate 21 Lug of negative electrode current collector 23 Negative electrode strap 25 Negative terminal 30 Separator 41 Battery case 43 Lid

Claims

1. a battery case having a cell chamber, a plate group housed in the cell chamber, and an electrolyte solution poured into the cell chamber, the electrolyte solution being dilute sulfuric acid; 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; The positive electrode plate is a current collector plate that holds a positive electrode mixture containing a positive electrode active material, the positive electrode active material includes tetragonal lead dioxide, The lattice constant c in the c-axis direction and the lattice constant a in the a-axis direction of the tetragonal lead dioxide satisfy the relationship of 0.6822≦c / a≦0.6830, and the lattice volume of the tetragonal lead dioxide is 83.25 Å 3 83.38Å or more 3 The following is a flooded lead-acid battery:

2. 2. The flooded lead-acid battery according to claim 1, wherein the lattice constant c in the c-axis direction and the lattice constant a in the a-axis direction of said tetragonal lead dioxide satisfy the relationship 0.6824≦c / a≦0.6827.

3. 3. The flooded lead-acid battery according to claim 1, wherein the electrolyte contains dilute sulfuric acid and aluminum ions of 20 mmol / L or more and 200 mmol / L or less, or magnesium ions of 25 mmol / L or more and 250 mmol / L or less.

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