JP7478877B1 - Flooded lead-acid battery - Google Patents

Abstract

[Problem] To prevent damage to a separator when growth occurs in a positive electrode plate and the plate curves, without changing the separator designs or the number of plates constituting a laminate from the specified values. [Solution] In a self-weight deflection test in which one end 20a in the width direction of a negative electrode plate 20 is fixed, the deflection amount h [mm], the dimension L [mm] in the width direction of the unfixed part of the negative electrode plate 20, and the mass W [g] of the unfixed part of the negative electrode plate 20 satisfy 0.0009≦h/(L×W)≦0.0048. [Selected Figure] Figure 4

Description

The present invention relates to a flooded lead-acid battery.

A flooded lead-acid battery, which is a typical lead-acid battery, comprises a battery case with a cell chamber, a group of electrodes housed in the cell chamber, and an electrolyte injected into the cell chamber. The group of electrodes has a laminate that includes multiple positive and negative plates arranged alternately, and separators arranged between the positive and negative plates.

The positive electrode plate has a positive electrode current collector including a lattice portion, a positive electrode mixture (a mixture including a positive electrode active material) held by the lattice portion, and a layer of the positive electrode mixture is formed on both plate surfaces of the lattice portion. The negative electrode plate has a negative electrode current collector including a lattice portion, and a negative electrode mixture (a mixture including a negative electrode active material) held by the lattice portion, and a layer of the negative electrode mixture is formed on both plate surfaces of the lattice portion.
The positive electrode plate has a positive electrode current collector including a lattice portion, a positive electrode ear protruding upward from the lattice portion in the vertical direction of the battery case, and a positive electrode mixture (a mixture containing a positive electrode active material) held by the lattice portion, and the negative electrode plate has a negative electrode current collector including a lattice portion, a negative electrode ear protruding upward from the lattice portion in the vertical direction of the battery case, and a negative electrode mixture held by the lattice portion.

The positive electrode ear is positioned in a position offset to one side from the center in the width direction of the grid portion (a direction perpendicular to both the up-and-down direction of the battery case and the stacking direction of the laminate), and the negative electrode ear is positioned in a position offset to the other side from the center in the width direction of the grid portion. The electrode plate group further has a positive electrode strap and a negative electrode strap that respectively connect the ears of the multiple positive and negative electrode plates. Dilute sulfuric acid is used as the electrolyte. Such flooded lead-acid batteries are widely used as automobile batteries, etc.

In many cases, the positive electrode current collector plate used in lead-acid batteries for automobiles is a rolled plate made of a lead alloy that has been processed by the expanding or punching method (expanded product, punched product). This is because this method allows the current collector plate to be produced continuously, and is therefore superior in terms of productivity and cost compared to the casting method.
However, in the case of expanded and punched products in which the positive current collector plate is made of a rolled plate of a lead alloy, it is known that the positive plate undergoes expansion of the lattice-shaped portion due to corrosion (so-called "growth"). It is known that the higher the temperature, the more the growth progresses. When growth occurs, the positive plate bends, which puts stress on the separator, which may damage the separator. In particular, the corners of the positive plate on the side that is not connected by the strap in the width direction are likely to bend significantly.

If the separator is damaged, the positive and negative plates may come into contact with each other, causing a short circuit, which may lead to a rapid decrease in the capacity of the lead-acid battery and shorten its lifespan.
In order to prevent the early end of life due to the above reasons, it has been proposed to provide a rib on the surface of the separator facing the positive electrode plate to prevent the separator from being damaged (see, for example, Patent Document 1). Patent Document 1 describes that the separator is made of polyethylene with an average molecular weight of 1.5 million to 2.2 million, the thickness of the base sheet is 0.10 mm or more and 0.22 mm or less, and the height of the rib is 0.4 mm or more.

On the other hand, in lead-acid batteries for automobiles, the plate group must be stored in a battery case of a fixed size, so there is an upper limit to the thickness of the laminate. Also, to improve the performance of lead-acid batteries, it is necessary to increase the number of plates that make up the laminate to increase the electrode reaction area, thereby increasing the amount of electrolyte held by the mixture and the efficiency of the electrode reaction.

JP 2004-259522 A

If the thickness of the separator is reduced, the number of plates constituting the stack can be increased, but as mentioned above, if the positive plate is curved due to growth, the separator becomes more susceptible to damage. On the other hand, if the separator is made thicker or has high ribs to make the entire separator, including the ribs, thicker, the separator becomes less susceptible to damage, but as mentioned above, reducing the number of plates constituting the stack is not preferable in terms of battery performance.
An object of the present invention is to suppress damage to the separator when growth occurs in the positive electrode plate and the positive electrode plate is curved, without changing the various separator designs or the number of electrode plates constituting the laminate from the specified values.

The inventors of the present invention completed this invention by focusing on the rigidity of the negative plate, rather than the various separator designs or the number of plates that make up the stack, as a technical concept for preventing separator damage when growth occurs in the positive plate and it curves.

A first aspect of the present invention for solving the above-mentioned problems is a flooded lead-acid battery having the following configurations (1) to (3).
(1) A battery case having a cell chamber, a plate group housed in the cell chamber, and an electrolyte injected into the cell chamber. The plate group has a laminate including a plurality of alternatingly arranged positive and negative plates, and a synthetic resin separator arranged between the positive and negative plates. The positive plate has a positive current collector including a lattice portion, a positive ear protruding from the lattice portion in the upper direction of the battery case, and a positive mixture (a mixture containing a positive active material) held by the lattice portion. The negative plate has a negative current collector including a lattice portion, a negative ear protruding from the lattice portion in the upper direction of the battery case, and a negative mixture (a mixture containing a negative active material) held by the lattice portion. The positive electrode lug is disposed at a position offset to one side from the center of the width direction of the lattice portion (a direction perpendicular to both the up-down direction of the battery case and the stacking direction of the stack), and the negative electrode lug is disposed at a position offset to the other side from the center of the width direction of the lattice portion. The electrode plate group further has a positive electrode strap and a negative electrode strap that connect the lugs of the positive electrode plates and the negative electrode plates, respectively.

(2) The positive electrode current collector plate is an expanded or punched product made of a rolled plate made of a lead alloy.
(3) The amount of deflection h [mm] in a self-weight deflection test in which one end of the negative plate in the width direction is fixed, the dimension L [mm] in the width direction of the unfixed portion of the negative plate, and the mass W [g] of the unfixed portion of the negative plate satisfy 0.0009≦h/(L×W)≦0.0048.

The flooded lead-acid battery of the present invention can suppress separator damage caused by growth and deformation of the positive electrode plate without changing the separator design or the number of plates that make up the stack from the specified values.

FIG. 2 is a diagram illustrating the flooded lead-acid battery of the embodiment, showing a state in which the lid is removed from the battery case. FIG. 2 is a partial cross-sectional view of the flooded lead-acid battery according to the embodiment. FIG. 2 is a front view showing a negative electrode current collector plate constituting the flooded lead-acid battery of the embodiment. FIG. 1 is a diagram illustrating a self-weight deflection test.

The following describes embodiments of the present invention, but the present invention is not limited to the embodiments described below. In the embodiments described below, technically preferable limitations are imposed for implementing the present invention, but these limitations are not essential requirements for the present invention.

[Overall battery configuration]
As shown in Fig. 1, the flooded lead-acid battery of the embodiment has a monoblock-type battery case 1 and six electrode plate groups 3. The shape of the battery case 1 is a rectangular parallelepiped, and the battery case 1 has a pair of first walls 11 formed on a pair of long sides of a rectangle forming a bottom surface, and a pair of second walls 12 formed on a pair of short sides. The interior of the battery case 1 is divided into six cell chambers 4 by five partition walls 13 parallel to the second walls 12.
One electrode group 3 is disposed in each of the six cell chambers 4, and an electrolyte is poured into each cell chamber 4. The electrolyte is dilute sulfuric acid with a specific gravity of 1.28 to 1.30 (calculated at 20°C). As shown in Fig. 1, the direction in which the cell chambers 4 are arranged is the X direction, and the direction perpendicular to this is the Y direction.

As shown in FIG. 2, each electrode plate group 3 has a laminate 6. The laminate 6 is composed of a plurality of alternatingly arranged positive electrode plates 10 and negative electrode plates 20, and a separator 30 arranged between the positive electrode plates 10 and the negative electrode plates 20. The number of positive electrode plates 10 constituting the laminate 6 may be the same as the number of negative electrode plates 20, or may be greater than the number of negative electrode plates 20. In this example, the number of positive electrode plates 10 and negative electrode plates 20 is the same.

The positive electrode plate 10 is composed of a positive electrode current collector and a positive electrode mixture (a mixture containing a positive electrode active material). The positive electrode current collector has a rectangular lattice portion and an ear protruding from one side of the rectangle that forms the lattice portion, and the positive electrode mixture is held in the lattice portion. In FIG. 2, the lattice portion holding the positive electrode mixture is indicated by the reference numeral 101, and the ear of the positive electrode plate 10 is indicated by the reference numeral 120. The ear 120 of the positive electrode plate 10 is disposed at a position shifted to one side from the center of the width direction of the lattice portion (the direction perpendicular to the paper surface of FIG. 2). The positive electrode plate 10 will be described in detail later.

The negative electrode plate 20 is composed of a negative electrode current collector and a negative electrode mixture (a mixture containing a negative electrode active material). The negative electrode current collector has a rectangular lattice portion and an ear protruding from one side of the rectangle that forms the lattice portion, and the negative electrode mixture is held in the lattice portion. In FIG. 2, the lattice portion holding the negative electrode mixture is indicated by the reference numeral 201, and the ear of the negative electrode plate 20 is indicated by the reference numeral 220. The ear 220 of the negative electrode plate 20 is disposed at a position shifted from the center of the width direction of the lattice portion (the direction perpendicular to the paper surface of FIG. 2) to the other side. The negative electrode plate 20 will be described in detail later.

The separator 30 is made of porous polyethylene and is a ribbed separator with a flat base and ribs that protrude in a pleated manner from the surface of the base on the positive electrode side. The thickness of the base is 0.15 mm to 0.25 mm, the protruding height of the ribs is 0.4 mm to 0.6 mm, the width of the ribs is 0.1 mm to 0.4 mm, and the spacing between the ribs is 2 mm to 10 mm.

Each electrode plate group 3 further has a positive electrode strap 71, a negative electrode strap 72, and a positive electrode intermediate electrode column 71a and a negative electrode intermediate electrode column 72a that respectively rise from the positive electrode strap 71 and the negative electrode strap 72. The positive electrode strap 71 and the negative electrode strap 72 connect the lugs 120 of the multiple positive electrode plates 10 and the lugs 220 of the multiple negative electrode plates 20 that constitute the stack 6 at different positions in the width direction of the positive electrode plates 10 and the negative electrode plates 20 (the direction that becomes the Y direction when inserted into the cell chamber).
The electrode plate groups 3 arranged in the cell chambers at both ends in the cell arrangement direction each have a positive electrode terminal pole 8 and a negative electrode terminal pole 9 which serve as external terminals. The positive electrode terminal pole 8 and the negative electrode terminal pole 9 are formed on a positive electrode strap 71 and a negative electrode strap 72 via small pieces 71b and 72b, respectively.

Each electrode plate group 3 is housed in the cell chamber 4 with the stacking direction of the laminate 6 aligned along the X direction and with the plate surfaces of the positive electrode plates 10 and the negative electrode plates 20 aligned along the up-down direction of the cell chamber 4 .
The positive intermediate pole 71a and the negative intermediate pole 72a of adjacent cell chambers 4 are resistance-welded to electrically connect adjacent cells in series. In addition, the tops of all cell chambers 4 are closed by fixing a lid (not shown) to the battery case 1. The positive terminal pole 8 and the negative terminal pole 9 penetrate the lid and are exposed to the outside.

[Regarding positive and negative electrodes]
[Method of manufacturing positive and negative electrode plates]
The positive electrode mixture and the negative electrode mixture are filled in the openings of each lattice part and are also present in layers on both plate surfaces of the lattice part. The positive electrode mixture and the negative electrode mixture are formed on the lattice part of each current collector plate, for example, as follows.
First, necessary additives (polypropylene fiber, polyethylene fiber, conductive carbon, etc.) are added to the lead powder, mixed by dry mixing, and then water is added and kneaded to obtain a water paste. Sulfuric acid is added to the water paste and kneaded to prepare a positive electrode paste and a negative electrode paste. At this time, organic shrink-proofing agents such as lignin, which are often used as additives for negative electrodes, are water-soluble and may be added at the same time as water. Next, the obtained positive electrode paste and negative electrode paste are filled into the openings of each lattice-shaped part, and then preheating, aging, and drying processes are performed to obtain a positive electrode plate and a negative electrode plate before chemical formation. Furthermore, a flooded lead-acid battery is assembled using these, and then chemical formation is performed to form a positive electrode mixture and a negative electrode mixture in each lattice-shaped part.

[Positive current collector plate]
The positive current collector constituting the positive plate 10 is an expanded or punched product made of a rolled plate made of a lead alloy. The thickness of the positive current collector is 0.7 mm or more and 1.1 mm or less. The horizontal side of the rectangle forming the lattice part of the positive current collector is longer than the vertical side.
[Negative electrode current collector]
The negative electrode current collector constituting the negative electrode plate 20 is formed by a continuous casting method using a lead alloy (such as a Pb-Ca-Sn alloy). The negative electrode current collector constituting the negative electrode plate 20 may be an expanded product or a punched product made of a rolled plate made of a lead alloy.

As shown in FIG. 3 , the negative electrode current collector 21 is composed of a rectangular lattice portion 210 and tab portions 220 .
3, in the negative electrode current collector 21 of the embodiment, the lattice portion 210 has a frame rib forming the four sides of a rectangle, and a plurality of middle ribs connected to the frame ribs and located inside the frame ribs. In addition, the horizontal sides of the rectangle forming the frame rib are longer than the vertical sides.
The frame bones include an upper frame bone 211 located on the upper side of the lattice portion 210 and extending horizontally, a lower frame bone 212 located on the lower side of the lattice portion 210 and extending horizontally, a left frame bone 213 located on the left side of the lattice portion 210 and extending vertically, and a right frame bone 214 located on the right side of the lattice portion 210 and extending vertically.

The ear portion 102 protrudes upward from a position shifted toward the right frame bone 214 from the longitudinal center of the upper frame bone 211. The multiple middle bones are composed of 16 vertical middle bones 216 connecting the upper frame bone 211 and the lower frame bone 212, and 10 horizontal middle bones 217 connecting the left frame bone 213 and the right frame bone 214. The vertical middle bones 216 extend parallel to the left frame bone 213 and the right frame bone 214. The horizontal middle bones 217 extend parallel to the upper frame bone 211 and the lower frame bone 212. The cross-sectional areas of the upper frame bone 211, the left frame bone 213, and the right frame bone 214 are larger than the cross-sectional areas of the vertical middle bones 216 and the horizontal middle bones 217.
The thickness of the negative electrode current collector 21 is preferably 0.7 mm or more and 1.1 mm or less.

[Negative electrode plate]
The dimension of the negative electrode plate 20 in the width direction (the direction perpendicular to both the up-down direction of the battery case and the stacking direction of the stack, the direction perpendicular to the paper surface of FIG. 1) is L0 [mm].
4, a self-weight deflection test is performed to measure the amount of deflection h [mm] of the negative electrode plate 20. That is, one end 20a in the width direction of the negative electrode plate 20 (the side farther from the ear portion 220) is placed on a support stand 82 placed on a stand 81, and a weight 83 is placed and fixed on top of it, and the amount of deflection h due to the weight is measured.
The measured deflection amount h, the widthwise dimension L [mm] of the portion of the negative electrode plate 20 where the weight 83 is not placed (the portion that is not fixed), and the mass W [g] of the portion of the negative electrode plate 20 where the weight 83 is not placed satisfy 0.0009≦h/(L×W)≦0.0048...(1).
Since "h/(L x W)" in equation (1) is the amount of deflection h divided by the mass W and dimension L of the negative electrode plate, this index does not depend on the mass and dimension L of the negative electrode plate.

<Method for making the negative electrode plate satisfy formula (1)>
The mechanical strength of the negative electrode plate depends on the mechanical strength of the lattice part of the negative electrode current collector, the binding strength between the negative electrode mixtures, and the adhesion between the lattice part and the negative electrode mixture.

<Method 1: Mechanical strength of the grid part of the negative electrode current collector>
The mechanical strength of the lattice part of the negative electrode current collector can be controlled mainly by the lattice design (whether the ribs are a simple vertical and horizontal lattice, or whether the vertical ribs are inclined rather than vertical, etc.), for example, by the presence or absence of an outer frame, and by regarding the ribs as "beams" or "ribs" and adjusting and arranging them in the extension direction, cross-sectional shape, and number.
In addition, the mechanical strength of the lattice-shaped portion of the negative current collector can also be controlled by the composition of the lead alloy forming the negative current collector (the content of Ca and Sn), the aging method of the alloy after casting, and the mass (amount of lead) per negative current collector, thickness, and outer dimensions.

<Method 2: Adhesion between negative electrode mixtures>
The binding strength between the negative electrode mixtures varies depending on the type and content of the additives contained in the negative electrode mixture. When preparing the negative electrode paste, adding polypropylene fibers or polyethylene fibers as an additive can increase the binding strength between the negative electrode mixtures and increase the mechanical strength of the negative electrode plate. On the other hand, when preparing the negative electrode paste, adding conductive carbon as an additive can reduce the cohesion of the particles in the paste, thereby reducing the binding strength between the negative electrode mixtures and decreasing the mechanical strength of the negative electrode plate.
The mechanical strength of the negative electrode plate can also be controlled by changing the density of the negative electrode mixture itself, the filling amount of the negative electrode mixture, the thickness of the layer formed on the plate surface of the lattice-shaped portion, the composition of the negative electrode mixture, and the state of the crystal grains (the content of tetrabasic lead sulfate, the degree of crystal growth, etc.).

<Method 3: Adhesion between the lattice portion and the negative electrode mixture>
The adhesion between the lattice portion and the negative electrode mixture can be controlled, for example, by changing the moisture content of the negative electrode paste used in manufacturing the negative electrode current collector plate, or by changing the temperature, humidity, and time of the preheating step and the aging step after filling the paste in the manufacturing process. It can also be controlled by bending the negative electrode plate after the aging and drying steps by hand or machine to cause cracks in the negative electrode mixture layer.
Furthermore, the adhesion between the negative electrode mixture and the grid-shaped portion can be controlled by changing the particle size of the lead particles through the current value during formation. Also, the surface roughness of the grid-shaped portion can be controlled by changing the physical processing conditions such as the roughness of the mold surface, matte finish, chemical etching, and sandblasting during the casting process in the production of the negative electrode current collector.

In addition, when the negative electrode current collector plate is an expanded product or a punched product made of a rolled plate made of a lead alloy, if the above-mentioned method of generating cracks is adopted as a method of controlling adhesion, there is a risk that the product will become defective if the adhesion is too low. Therefore, in such a case, it is necessary to adjust the moisture content of the negative electrode paste and the temperature and humidity and time of the preheating process and the aging process after filling the paste so that the adhesion does not decrease too much.
Methods 2 and 3 are methods for controlling the mechanical strength of the negative electrode plate in the process of forming a negative electrode mixture on the lattice-shaped portion of the negative electrode current collector plate, and therefore are methods that make it easier to control the mechanical strength of the negative electrode plate than method 1, which controls the mechanical strength of the negative electrode current collector plate.

[Action, effect]
By the negative plate 20 of the flooded lead-acid battery of the above embodiment satisfying formula (1) (the index "h/(L×W)" relating to the mechanical strength of the negative plate 20 being 0.0009 or more and 0.0048 or less), the negative plate 20 can appropriately deform following the curvature of the positive plate 10, and stress due to the curvature of the positive plate can be made less likely to be applied to the separator 30. Accordingly, damage to the separator due to growth of the positive plate 10 is prevented, and short circuits due to the damage to the separator can be suppressed.

In addition, the negative electrode plate 20 bends to be able to tolerate the curvature of the positive electrode plate 10, thereby suppressing damage to the separator. This allows the use of a separator with a small dimension in the thickness direction, making it possible to increase the number of electrode plates constituting the laminate 6 compared to the case where a separator with a large dimension in the thickness direction is used. As a result, the battery reaction area of the flooded lead-acid battery can be increased, and the amount of electrolyte held by the negative electrode mixture and the efficiency of the electrode reaction can be improved.
In other words, by setting the rigidity of the negative plate to a value that allows for the bending of the positive plate when the flooded lead-acid battery is in use, and preventing the separator from being damaged when in use, it becomes possible to use a separator with a small dimension in the thickness direction, and therefore it becomes possible to increase the number of plates that make up the stack 6.

Therefore, according to the flooded lead-acid battery of this embodiment, improved life performance can be expected, particularly as a lead-acid battery for automobiles that are expected to be used in high-temperature regions where growth is likely to occur, or as a lead-acid battery equipped with a thin positive electrode current collector.
In contrast, in a flooded lead-acid battery that differs from the flooded lead-acid battery of the above embodiment only in that the index "h/(L×W)" is less than 0.0009, when used under the above conditions, the negative plate 20 is less likely to deform in accordance with the curvature of the positive plate 10, and stress due to the curvature of the positive plate is more likely to be applied to the separator 30. As a result, it is difficult to prevent damage to the separator, and it cannot be expected to suppress short circuits caused by separator damage.

In addition, when a flooded lead-acid battery differs from the flooded lead-acid battery of the above embodiment only in that the index "h/(L×W)" exceeds 0.0048, the amount of deformation of the negative plate 20 following the curvature of the positive plate 10 is too large when used under the above conditions, resulting in insufficient adhesion between the negative electrode mixture and between the negative electrode current collector and the negative electrode mixture. As a result, the conductivity of the negative plate becomes insufficient, which may lead to poor potential distribution and poor discharge characteristics with large currents.

[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 of Samples No. 1 to No. 24 having the configurations shown below were fabricated.
The flooded lead-acid batteries of Samples No. 1 to No. 12 were B24 size flooded lead-acid batteries with a nominal voltage of 12 V, and all had the same configuration except for the configuration of the negative electrode plate.
The flooded lead-acid batteries of samples No. 13 to No. 24 were flooded lead-acid batteries with a D23 size and a nominal voltage of 12 V, and all had the same configuration except for the configuration of the negative electrode plate.

[No.1 to No.12]
<Production of positive electrode plate before chemical formation>
A positive electrode current collector plate was manufactured by carrying out a slab casting step, a rolling step, and a punching step in this order.
First, a slab casting process was carried out in the following manner.
A block of lead alloy containing 0.06% by mass Ca, 1.6% by mass Sn, 0.02% by mass Al, and the remainder being lead and unavoidable impurities was prepared and melted by heating to obtain a molten metal. The molten metal was poured between two opposing metal rolls and cooled by the metal rolls to obtain a lead alloy slab.

Next, the obtained lead alloy slab was passed between a pair of upper and lower rolling rolls to carry out a rolling process at a rolling reduction of 90%, thereby obtaining a rolled sheet having a width of 320 mm and a thickness of 1.0 mm.
Next, the obtained rolled sheet was put into a press molding machine and punched in the thickness direction to obtain a positive electrode current collector plate having ears extending upward from the upper frame of the lattice-shaped portion. The dimensions of the lattice-shaped portion are 110 mm in the direction in which the ears extend (height), 105 mm in the direction perpendicular thereto (width), and 1.0 mm in thickness. The dimensions of the ears are 10 mm in width and 15 mm in height. The ears extend from between the center and end of the lattice-shaped portion in the width direction.
A positive electrode paste prepared by a normal method was filled into the grid-like portion of the obtained positive electrode current collector plate, and the plate was aged and dried by a normal method to obtain a positive electrode plate (positive electrode filled plate) before chemical formation.

<Production of negative electrode plate before chemical conversion>
A negative electrode current collector having an ear extending upward from the upper frame of the lattice-shaped portion was obtained by continuous casting using a lead alloy containing 0.09% by mass Ca, 0.4% by mass Sn, 0.02% by mass Al, and the remainder being lead and unavoidable impurities. The dimensions of the lattice-shaped portion are 100 mm in the direction in which the ear extends (height), 100 mm in the direction perpendicular thereto (width), and 0.8 mm in thickness. The dimensions of the ear are 10 mm in width and 15 mm in height. The ear extends from between the center and end of the lattice-shaped portion in the width direction.
The bones of the lattice portion of the obtained negative electrode current collector plate were composed of 16 vertical bones approximately perpendicular to the upper frame bone and 7 horizontal bones approximately perpendicular to the vertical bones.

The grid-shaped portion of the obtained negative electrode current collector was filled with 55 g of a negative electrode paste prepared by the following method, and then heat treatment before aging was performed at 400° C. or 300° C. Next, after aging at 40° C. and a relative humidity of 90%, drying was performed at 60° C. to obtain a negative electrode filled plate (negative electrode plate before chemical formation) for each sample.
The negative electrode paste was prepared by adding water and sulfuric acid to lead powder and kneading the mixture to obtain a water paste, and then adding acetylene black (AB) or ketjen black (KB) as conductive carbon to the water paste in a ratio of 0.2 parts by mass per 100 parts by mass of lead powder, and kneading the mixture.

<Preparation of electrode plate group before chemical formation>
As the separator, a porous polyethylene separator with vertical ribs (340G manufactured by Entec Asia Co., Ltd.) was selected, and a pouch-shaped separator was prepared with the vertical rib side facing outward.
One negative electrode packing plate for each sample was placed in the pouch-shaped separator. Seven pouch-shaped separators containing negative electrode packing plates and six positive electrode packing plates were alternately stacked to prepare six stacks for each sample.
Next, using a cast-on-strap (COS) type casting device, straps, intermediate poles, and terminal poles were formed on the positive electrode packing plates and negative electrode packing plates of the six stacks obtained for each sample, thereby obtaining six electrode plate groups for each sample.

<Battery assembly>
Next, the six electrode plates obtained for each sample were placed in six cell compartments of a monoblock type battery container made of polypropylene.
Next, the intermediate poles between adjacent cell chambers were resistance-welded, and the battery case and the lid were heat-welded in a conventional manner. An electrolyte solution consisting of dilute sulfuric acid with a specific gravity of 1.250 (calculated at 20°C) was then poured into each cell chamber through each of the electrolyte injection holes in the lid. The electrolyte injection holes were then sealed to assemble an unformed flooded lead-acid battery.
The positive and negative packed plates were then converted into positive and negative plates by conventional container formation to complete a flooded lead acid battery.

[No.13 to No.24]
<Production of positive electrode plate before chemical formation>
A positive electrode current collector plate was manufactured by carrying out a slab casting step, a rolling step, and a punching step in this order.
First, a slab casting process was carried out in the following manner.
A block of lead alloy containing 0.06% by mass Ca, 1.6% by mass Sn, 0.02% by mass Al, and the remainder being lead and unavoidable impurities was prepared and melted by heating to obtain a molten metal. The molten metal was poured between two opposing metal rolls and cooled by the metal rolls to obtain a lead alloy slab.

Next, the obtained lead alloy slab was passed between a pair of upper and lower rolling rolls to carry out a rolling process at a rolling reduction of 90%, thereby obtaining a rolled sheet having a width of 320 mm and a thickness of 1.0 mm.
Next, the obtained rolled sheet was put into a press molding machine and punched in the thickness direction to obtain a positive electrode current collector plate having an ear portion extending upward from the upper frame of the lattice portion. The dimensions of the lattice portion are 116 mm in the direction in which the ear portion extends (height), 137 mm in the direction perpendicular thereto (width), and 1.0 mm in thickness. The dimensions of the ear portion are 10 mm in width and 15 mm in height. The ear portion extends from between the center and the end of the lattice portion in the width direction.
A positive electrode paste prepared by a normal method was filled into the grid-like portion of the obtained positive electrode current collector plate, and the plate was aged and dried by a normal method to obtain a positive electrode plate (positive electrode filled plate) before chemical formation.

<Production of negative electrode plate before chemical conversion>
A negative electrode current collector plate having an upper edge extending upward from the upper frame of the lattice-shaped portion was obtained by continuous casting using a lead alloy containing 0.09% by mass Ca, 0.4% by mass Sn, 0.02% by mass Al, and the remainder being lead and unavoidable impurities. The dimensions of the lattice-shaped portion are 115 mm in the direction in which the edge extends (height), 135 mm in the direction perpendicular thereto (width), and 0.8 mm in thickness. The dimensions of the edge are 10 mm in width and 15 mm in height. The edge extends from between the center and end of the lattice-shaped portion in the width direction.

The bones of the lattice portion of the obtained negative electrode current collector plate were composed of 16 vertical bones approximately perpendicular to the upper frame bone and 10 horizontal bones approximately perpendicular to the vertical bones.
The grid-shaped portion of the obtained negative electrode current collector was filled with 75 g of a negative electrode paste prepared by the following method, and then heat treatment before aging was performed at 400° C. or 300° C. Next, after aging at 40° C. and a relative humidity of 90%, drying was performed at 60° C. to obtain a negative electrode plate (negative electrode filled plate) before chemical conversion.
The negative electrode paste was prepared by adding water and sulfuric acid to lead powder and kneading the mixture to obtain a water paste, and then adding acetylene black (AB) or ketjen black (KB) as conductive carbon to the water paste in a ratio of 0.2 parts by mass per 100 parts by mass of lead powder, and kneading the mixture.

<Preparation of electrode plate group before chemical formation>
Pre-chemical electrode plate assemblies were prepared in the same manner as Nos. 1 to 12, except that the dimensions of the pouch-shaped separator were changed to match the dimensions of the negative electrode packing plates of Nos. 12 to 24.
<Battery assembly>
Batteries were assembled in the same manner as No. 1 to No. 12, except that the dimensions of the battery container used were changed to match the dimensions of the electrode plate assemblies of No. 12 to No. 24.

[Measurement of self-weight deflection]
One of the obtained sample flooded lead acid batteries was disassembled to measure the amount of deflection h of the negative electrode plate due to its own weight.
Specifically, the plate assembly was first removed from the cell chamber (third cell chamber) next to the cell chamber (first cell chamber) in which the plate assembly having the positive terminal pole was housed, and disassembled, and the negative plate housed in the pouch-shaped separator located in the center of the plate assembly was removed, washed with water, and dried. Next, the mass W0 [g] of the washed and dried negative plate was measured.

Next, the amount of deflection h [mm] of the negative plate whose mass was measured was measured by the method shown in Fig. 4. At that time, one end 20a of the negative plate 20 in the width direction (the side farther from the ear 220) having a length L equivalent to 15% of the width L0 [mm] of the negative plate 20 was placed on a support stand 82, and a weight 83 was placed and fixed on top of the end. The distance from the height of the support stand 82 to the height of the tip of the deformed negative plate 20 (the degree of sagging of the tip of the plate) was measured and used as the amount of deflection h of the negative plate.
The index "h/(L×W)" was calculated using the measured deflection amount h, the widthwise dimension L [mm] of the part of the negative electrode plate 20 where the weight 83 is not placed (the part that is not fixed), and the mass W [g] (= 0.15×W0) of the part of the negative electrode plate 20 where the weight 83 is not placed.
The amount of deflection was measured on both one surface and the opposite surface of the negative electrode plate 20, and the value of the larger amount of deflection was used.

[Evaluation of Battery Characteristics]
<Check for separator damage and adhesion>
Using the remaining one of the obtained sample flooded lead-acid batteries, a light load life test was carried out according to JIS D 5301. However, in order to increase the corrosion rate of the substrate, that is, to make the positive electrode plate in a state in which growth is facilitated, the test temperature was changed from 41°C to 75°C, and the discharge time was also changed from 240 seconds to 120 seconds, which is half the time.
Specifically, in a 75°C water bath environment, 25A discharge for 2 minutes and CC-CV charging (14.8V, maximum charging current 25A) for 10 minutes were repeated, and the batteries were left for 56 hours after each 480 cycles. After leaving the batteries, they were continuously discharged for 30 seconds at 310A for No. 1 to 12 and 590A for No. 13 to 24, and the voltage at 30 seconds was checked. This was counted as one set, and the voltage at 30 seconds after 8 sets was recorded as "battery performance". After recording, the batteries were disassembled and the condition of all the separators was visually inspected.

<Criteria>
If the 30-second voltage after the above 8 sets is 7.2 V or higher, it satisfies the predetermined standard (3800 cycles, which is the required number of cycles for model 80D23L), and therefore the battery performance can be determined to be good.
If even one separator is found to be torn as a result of visual inspection, the separator is deemed to have failed. Severely torn separators are considered to have caused a micro-short circuit.
If the 30-second voltage after the 8th set was 7.2 V or higher and the separator condition was also good, the overall evaluation was judged to be pass (◯), and if at least either of these was poor, the overall evaluation was judged to be fail (×).
These results are shown in Table 1 together with the negative electrode plate configuration and manufacturing conditions.

From the results in Table 1, it can be seen that with the negative plate configuration and test conditions used this time, the negative plate index "h/(L×W)" must be greater than or equal to 0.0009 and less than or equal to 0.0048, in other words, "{h/(L×W)}×1000" must be greater than or equal to 0.9 and less than or equal to 4.8, in order to pass the overall evaluation, and that if this is not satisfied, the overall evaluation will be failed.
In addition, in Nos. 1, 2, 13, 14, 17, and 18, in which the index “h/(L×W)” exceeded 0.0048, no separator tear occurred. However, in Nos. 7, 11, 12, and 23, in which the voltage at 30 seconds after 8 sets was less than 7.2 V and less than 0.0009, separator tear occurred.

In particular, in No. 23, a short circuit was observed before the 8th set, so the voltage at 30 seconds after the 8th set could not be measured. This is thought to be due to a break in the separator, which caused a micro-short circuit.
In addition, in No. 11, the voltage at 30 seconds after the eighth set was less than 7.2V.
As can be seen from the above, with the negative plate configuration and test conditions used in this study, the negative plate index "h/(L x W)" satisfies the range of 0.0009 to 0.0048, so that a specified battery performance can be maintained while preventing damage to the separator when growth occurs in the positive plate and the plate curves.

REFERENCE SIGNS LIST 10 Positive electrode plate 101 Lattice portion holding positive electrode mixture 120 Ear portion of positive electrode current collector plate 20 Negative electrode plate 201 Lattice portion holding negative electrode mixture 21 Negative electrode current collector plate 210 Lattice portion of negative electrode current collector plate 211 Upper frame 212 Lower frame 213 Left frame 214 Right frame 216 Vertical center frame 217 Horizontal center frame 220 Ear portion of negative electrode current collector plate 30 Separator 1 Battery case 4 Cell chamber 3 Plate group 6 Laminate 71 Positive electrode strap 8 Positive electrode terminal pole 72 Negative electrode strap 9 Negative electrode terminal pole

Claims (2)

The battery includes a battery case having a cell chamber, a plate group housed in the cell chamber, and an electrolyte injected into the cell chamber;
The electrode plate group has a laminate including a plurality of positive electrode plates and negative electrode plates arranged alternately, and a separator made of a synthetic resin arranged between the positive electrode plates and the negative electrode plates,
The positive electrode plate includes a positive electrode current collector including a lattice portion, a positive electrode lug protruding upward from the lattice portion in the up-down direction of the battery case, and a positive electrode mixture held by the lattice portion,
The negative electrode plate includes a negative electrode current collector including a lattice portion, a negative electrode lug protruding upward from the lattice portion in the up-down direction of the battery case, and a negative electrode mixture held by the lattice portion,
the positive electrode ear portion is disposed at a position shifted to one side from the center of the width direction of the lattice portion, and the negative electrode ear portion is disposed at a position shifted to the other side from the center of the width direction of the lattice portion,
The electrode plate group further includes a positive electrode strap and a negative electrode strap that connect the lugs of the positive electrode plates and the negative electrode plates, respectively,
The positive electrode current collector plate is an expanded or punched product made of a rolled plate made of a lead alloy,
A flooded lead-acid battery in which the amount of deflection h [mm] in a self-weight deflection test in which one end of the negative plate in the width direction is fixed, the dimension L [mm] in the width direction of the unfixed portion of the negative plate, and the mass W [g] of the unfixed portion of the negative plate satisfy 0.0009≦h/(L×W)≦0.0048. the positive electrode current collector is formed of a lead alloy having a calcium (Ca) content of 0.035 mass% or more and 0.1 mass% or less, a tin (Sn) content of 0.4 mass% or more and 2.2 mass% or less, and the remainder being lead and unavoidable impurities;
2. The flooded lead-acid battery according to claim 1, wherein the thickness of the positive electrode current collector is 0.7 mm or more and 1.1 mm or less.

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