JPH0773871A - Bipolar plate for lead-acid battery - Google Patents

Abstract

PURPOSE:To lengthen the life of a lead-acid battery by using a bipolar plate in which a conductive oxide layer and a dense PbO2 layer are formed on a positive active material side of a base and a lead layer on a negative active material side. CONSTITUTION:A bipolar plate for lead-acid battery is manufactured by forming a conductive oxide layer 2, a dense alpha-PbO2 layer 3, a beta-PbO2 layer 4 on a positive active material 5 side of a base made of a corrosion resistant metal such as Ti, and a lead or lead alloy layer 6 on a negative active material 7 side. The dense PbO2 layer preferably has a ratio of micropores whose pore size is 10mum or less to the total volume of 10% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved electrode plate for a bipolar lead acid battery.

[0002]

2. Description of the Related Art Conventional lead-acid batteries are
After stacking the positive and negative plates and separators, forming a strap for connecting the electrode plates and the inter-cell connecting column that is integrated with the strap into an electrode plate group and inserting it into the battery case The inter-cell connecting columns are welded by electric resistance welding or the like, and the cells are connected in series to form a battery having a predetermined voltage. Therefore, parts such as straps for connecting the electrode plates and connecting pillars between cells are required, resulting in a large number of parts and processes, large internal resistance, difficulty in weight reduction and improvement in volumetric efficiency. Had a problem. A bipolar lead-acid battery has been proposed as one method for solving such a problem.

A bipolar lead acid battery is constructed by sequentially laminating a bipolar electrode plate and a separator. The substrate used for the bipolar electrode plate has functions of electrical connection between cells, isolation of an electrolytic solution, and retention of an active material. Therefore, in the bipolar lead-acid battery, parts such as straps and inter-cell connecting columns used in the conventional lead-acid battery are eliminated, so that the internal resistance is low and high volume efficiency can be obtained.

At present, a lead or lead alloy sheet is used as the base of the bipolar plate. However, since the specific gravity of lead alloy is as large as about 11 g / cm ³ , there is a drawback that the weight of the battery becomes heavy. Furthermore, when the lead alloy is placed at the positive electrode potential, the reaction of gradually converting lead to lead dioxide occurs and is corroded. When the lead or lead alloy sheet used for the bipolar electrode plate is corroded and penetrates the substrate, the positive electrode and negative electrode active materials formed on both sides of the substrate are short-circuited, and the function as the bipolar electrode plate is completely lost. For these reasons, there is a demand for a bipolar electrode plate that is lightweight and has excellent corrosion resistance.

Further, the current bipolar electrode plate is different from the conventional paste type electrode plate in which the active material is held in the lattice by filling the active material on the both surfaces of the flat sheet. However, if the volume of the active material changes due to charge and discharge, the active material may easily come off, the contact between the active material and the substrate may be poor, and the life may be shortened.

[0006]

The present invention is to solve the above-mentioned problems of the bipolar electrode plate, which uses a substrate made of a corrosion-resistant metal, one side of which is a positive electrode active material and the other side of which is a negative electrode active material. In a lead-acid battery bipolar plate formed of a substance, a conductive oxide layer and a dense PbO ₂ layer are formed on the positive electrode active material side of the substrate, and a lead layer or a dense PbO ₂ layer is formed on the negative electrode active material side of the substrate. It is characterized in that a lead alloy layer is formed.

As the corrosion-resistant metal, titanium, zirconium, niobium, tantalum, tungsten, or a base alloy thereof can be used because it is lighter than the lead alloy and has excellent corrosion resistance.

The structure of the bipolar electrode plate is such that a conductive oxide layer and a dense PbO ₂ layer are formed on the positive electrode active material side of a substrate made of a corrosion-resistant metal, the positive electrode active material is provided thereon, and the negative electrode active material side is provided. A lead or lead alloy layer is formed and a negative electrode active material is provided thereon. This manufacturing method will be described step by step using the case where titanium is used for the substrate as an example.

Since the passivation film is formed on the surface of the titanium substrate in the air, it is necessary to remove the passivation film as a pretreatment. As a removing method, for example, there is a method of polishing the surface of the substrate with a wire brush or the like, and then performing an etching treatment in boiling hydrochloric acid. By doing so, almost all the passive film on the titanium surface can be removed.

Then, a conductive oxide layer is formed on the surface of one surface of the titanium substrate from which the passivation film has been removed, which is the positive electrode active material side. Since the high corrosion resistance of titanium is due to the passivation film formed on the surface, it is necessary to form a film in place of the passivation film on the titanium surface in order to use it as a current collector. The role of this coating is to electrically connect the titanium substrate and the PbO ₂ layer and to prevent the formation of a passive coating on the titanium surface due to the oxidation action of PbO ₂ . Oxides of tin, antimony, titanium, tantalum, palladium, platinum and the like are suitable for this film because they have conductivity.

The type of the oxide film may be a single type, but the conductivity can be increased by doping another type of metal oxide or superposing different types of oxides. For example, tin oxide doped with antimony, a composite oxide of tantalum and titanium, a tin oxide layer and a palladium oxide layer overlaid, and the like can be used.

The thickness of the oxide film is about 0.1 to 10 μm, preferably about 1 μm. This is because if the thickness is too thin, a passive film is likely to be formed, and if it is too thick, the conductivity decreases.

The oxide film can be produced by a thermal decomposition method or the like. For example, a solution obtained by dissolving tin tetrachloride and antimony trichloride in a predetermined amount in a solvent such as propanol is applied to a titanium substrate and baked at about 500 ° C., so that the surface of titanium is doped with antimony tin oxide (SnO ₂ -Sb
₂ O ₃ ) is formed. The thickness of the oxide layer is
It can be controlled by the number of firings.

Next, a PbO ₂ layer is formed on the conductive oxide layer. The PbO ₂ layer can be formed by pressing a mixture of PbO ₂ powder and a binder, forming by electrodeposition, etc., but the electrodeposition is generally performed. The crystal structure of PbO ₂ includes α type and β type.
The α type is more prone to deterioration than the β type, but has a characteristic of less electrodeposition strain. On the other hand, the β type has a characteristic that it is less likely to deteriorate but has a large electrodeposition strain. If there is electrodeposition strain, the electrodeposition layer is likely to crack, and the electrode is likely to deteriorate.

The electrodeposition of α-PbO ₂ can be carried out by applying an electric current in an alkaline bath containing lead ions. The electrodeposition of β-PbO ₂ can be performed, for example, by energizing in a lead nitrate bath.

The function required for the PbO ₂ layer is that it has electronic conductivity and is electrochemically inactive. That is, in the positive electrode of the lead storage battery, it is required that the electrodeposited PbO ₂ layer is not discharged even when the active material is discharged. When the electrodeposited PbO ₂ layer is discharged, PbSO ₄ having a larger molecular volume than PbO ₂ is formed and the electrode is destroyed.

The reactivity of the PbO ₂ layer is affected by the crystallinity and porosity of PbO ₂ . The crystallinity is considered to be almost constant when it is produced by electrodeposition. Therefore, the relationship between porosity and reactivity was investigated. Α, β-P of various porosities can be obtained by changing the current density, solution concentration, temperature, etc. during electrodeposition.
bO ₂ was prepared on a titanium substrate on which a tin oxide film was formed, and used as an electrode. Generally, by increasing the current density, decreasing the solution concentration, or lowering the temperature, the electrodeposition becomes non-uniform and the porosity increases. Each P
The thickness of the bO ₂ layer was about 100 μm.

With respect to these electrodes, the potential scanning was repeated to examine the reactivity. Since the range of potential scanning is set to be the same as the potential of the positive electrode of the lead storage battery during charging and discharging, it can be regarded as simulating the charge / discharge cycle test of the lead storage battery. The reactivity was evaluated by the amount of electricity on the reducing side at the 500th cycle. It can be said that as the amount of reduced electricity increases, the number of reactions in which PbO ₂ changes to PbSO ₄ increases, that is, discharge is more likely. The test conditions are shown below.

Test electrode: Titanium electrode Counter electrode: Pure lead plate Reference electrode: Hg / Hg ₂ SO ₄ scanning range: 0.6-1.8 V Scanning speed: 1 V / min Electrolyte: Specific gravity 1.30 H ₂ SO ₄ Temperature: 25 ° C. The vertical axis represents the amount of reduced electricity at the 500th cycle as an index of reactivity, and the horizontal axis represents porosity. The porosity indicates the ratio of pores having a diameter of 10 μm or less in the volume. Both α and β-PbO _{2 have a} porosity of 10
%, The reactivity rapidly increases, and α-PbO
_The increase rate was almost constant at 20% or more for ₂ and 25% or more for β-PbO ₂ . When both α and β-PbO ₂ were 10% or less, the reactivity was small and the difference was small, but when 10% or more, α-PbO ₂ was higher in reactivity. It is considered that the reaction of PbO ₂ has a higher reactivity as the sulfate ion is more likely to diffuse because the sulfate ion is involved, that is, the higher the porosity.
From these results, it was found that when the porosity of both α and β-PbO ₂ was 10% or less, the reactivity was low and a PbO ₂ layer which was not easily broken even when used on the positive electrode side of the lead storage battery was obtained.

With respect to the PbO ₂ layer, either α or β-PbO ₂ may be used as long as the porosity is 10% or less, but in order to reduce the electrodeposition strain as a whole, α-
It is preferable to alternately stack PbO ₂ layers and β-PbO ₂ . If the thickness of the PbO ₂ layer is too thin, electrode breakage easily occurs, and if it is too thick, electrical resistance and internal strain increase, so the thickness of the α-PbO ₂ layer is about 5-100 μm, β
A suitable thickness of the -PbO ₂ layer is about 5-100 μm.

Next, a lead layer or a lead alloy layer is formed on the surface of the substrate on the side of the negative electrode active material. The formation method is thermal evaporation, sputtering,
A physical method such as ion plating or a chemical method such as plating or chemical vapor deposition is possible. Thickness of lead layer or lead alloy layer is 1-100μ
m is suitable. For example, when a lead layer is formed by electroplating, the positive electrode surface can be sealed and the negative electrode surface can be plated with lead by energizing in a lead borofluoride bath.

A bipolar electrode plate is completed by applying a paste-like positive electrode / negative electrode active material, which is usually used in a lead battery, on each surface of the base material thus produced and forming the base material. An example of the structure of the bipolar electrode plate of the present invention is shown in FIG. 1 is a corrosion resistant metal substrate such as titanium, 2 is a conductive oxide layer, 3 is an α-PbO ₂ layer, 4 is β-PbO ₂
Layer 5 is a positive electrode active material, 6 is a lead or lead alloy layer, and 7 is a negative electrode active material.

FIG. 3 shows an example of a substrate for a bipolar electrode plate. This is a base body 1 made of a corrosion-resistant metal sheet, an uneven portion 8 that is a portion having a hemispherical unevenness formed by machining on the sheet, and an inter-cell isolation portion 9 that is a portion that is embedded in a resin or the like to isolate cells. The conductive oxide layer and the PbO ₂ layer are formed on the positive electrode active material-filled surface 10, which is one surface of the uneven portion, and the lead oxide or PbO ₂ layer is formed on the other surface. A lead alloy layer is formed.

FIG. 4 is a base body having a rectangular parallelepiped unevenness, and FIG.
Is a substrate having wavy unevenness. Since the bases shown in FIGS. 3, 4 and 5 are filled with the positive and negative electrode active materials in the irregularities, the active material is removed more than the conventional bipolar electrode plate having a structure in which the active material is applied to a flat sheet. And peeling is less likely to occur.
Moreover, since the surface area of the current collector is greatly increased by making it uneven, the current density at the time of charging / discharging is reduced, and the utilization factor of the active material is improved and the voltage loss is also reduced.

[0025]

Example: A vertical width of 50 mm made of JIS type 2 titanium,
A sheet with a width of 50 mm and a thickness of 0.05 mm has a diameter of 1 m.
A substrate as shown in FIG. 3 in which hemispherical irregularities of m and a height of 0.5 mm were formed was produced. The size of the uneven part is 40 in width
The width was 40 mm. Concavo-convex formation is 1 mm in diameter
Steel balls were spread at equal intervals, and the sheet was pressed thereon. Also, for comparison, a similar substrate was prepared using a sheet of lead-calcium-tin alloy having the same size.

This substrate was polished with a wire brush until it had a metallic luster, and then immersed in 25% boiling hydrochloric acid for 1 hour for etching.

First, an oxide layer and P are formed on the surface filled with the positive electrode active material.
A bO ₂ layer was formed. The formation of the oxide layer on the titanium substrate is carried out by coating solutions of tin tetrachloride, antimony trichloride, titanium tetrachloride, tantalum pentachloride, etc., alone or in mixture, and then baking the solutions.

To form the antimony-doped tin oxide, a solution of 0.1 mol of tin tetrachloride, 0.03 mol of antimony trichloride and a small amount of hydrochloric acid in propanol is used. In order to form a titanium-tantalum complex oxide, a solution of 0.1 M titanium tetrachloride and tantalum pentachloride and a small amount of hydrochloric acid in propanol is used.

After immersing the titanium substrate in each solution, the substrate was rotated at about 200 rpm. By doing so, the excess liquid was scattered and the solution could be applied thinly and uniformly on the substrate. Then, as preliminary drying, it was left at 50 ° C. for about 1 hour. At this time, the surface filled with the negative electrode active material was sealed with an acid resistant tape so that the solution was not applied to this surface.

The firing was performed as follows. The substrate on which the solution has been applied and dried is placed in an electric furnace in an oxidizing atmosphere,
After 10 minutes at 0 ° C, the temperature was raised to 500 ° C, kept at 500 ° C for 30 minutes, and then gradually cooled. Water is removed at 140 ° C, and oxides are generated at 500 ° C. Solution coating and firing were repeated several times until the thickness of the oxide layer was about 1 μm.

Next, a PbO ₂ layer was formed on the titanium substrate on which the oxide layer was formed. The electrodeposition of α-PbO ₂ is carried out in a 4 to 5N sodium hydroxide solution saturated with lead hydroxide,
The current was applied at a temperature of 40 to 50 ° C. and a current density of 5 to 10 mA / cm ² . The electrodeposition of β-PbO ₂ was carried out at a temperature of 70 to 40 in a 30 to 40 wt% lead nitrate solution in which the pH was kept around 4.
It was performed by energizing at 80 ° C. and a current density of 50 to 100 mA / cm ² . Α and β-P formed under these conditions
The porosity of bO ₂ was 10% or less. This time,
The thickness of the α and β-PbO ₂ layers was about 50 μm.

Next, a lead layer was formed on the surface filled with the negative electrode active material. The formation was performed by electroplating. The electrodeposition bath is an aqueous solution containing 40% by volume of lead borofluoride, 5% by volume of hydrofluoric acid, 2% by weight of boric acid and 0.04% by weight of gelatin. Seal the positive electrode active material filled surface with corrosion resistant tape and
Approximately 10μ in thickness when energized at 30 ℃ / current density of 30mA / cm ^2.
m lead layer was formed.

As shown in FIG. 6, the oxide layer and the PbO ₂ layer forming surface of the substrate on which the irregularities are formed are filled with the positive electrode active material paste, and the other lead layer forming surface is filled with the negative electrode active material paste. The bipolar electrode plate 12 was used.

A bipolar battery is shown in FIGS. FIG. 7 shows the case where a base body having irregularities is used, and FIG. 8 shows the case where a flat base body having no irregularity processing is used. These consist of 5 bipolar plates and 2 end plates,
It is a structure in which cells are connected in series and is a bipolar sealed lead acid battery having a nominal voltage of 12 V and a nominal capacity of 3 Ah.

The end plate is filled with a positive or negative electrode active material only on one side. As the separator 13, a separator made of fine glass fibers and holding an electrolytic solution (hereinafter simply referred to as a separator) was used. Bipolar electrode plates and separators were alternately laminated, and the periphery of the inter-cell isolation portion 9 was solidified with resin to form a resin frame 16 so that the electrolytic solution did not move between cells. At this time, a liquid injection port 17 for injecting an electrolytic solution was provided at the top of each cell. An exhaust valve 18 is attached to this hole after the electrolyte is injected. After injecting the electrolytic solution, ordinary battery case formation was performed, and an exhaust valve was attached to complete the bipolar battery of the present invention.

Various capacity tests and life tests were conducted on the batteries thus manufactured. The battery contents are shown in Table 1.

[0037]

[Table 1]

Only the oxide film was formed on the positive electrode side to form PbO ₂
A battery using a bipolar electrode without forming a layer is (N
o. 1) When conducting constant current energization for battery case formation, the voltage increased abnormally and formation could not be performed. This is probably due to the formation of a passive film on the titanium surface. It can be said that the oxide film alone is insufficient for preventing the formation of the passive film on the positive electrode side of the lead storage battery.

A battery using a titanium-based bipolar electrode plate having an oxide film and a PbO ₂ layer formed on the positive electrode side (N
o. In Nos. 2 to 6), the battery case formation could be performed without any abnormality as in the case of the conventional battery (No. 7, 8) using the lead alloy-based bipolar electrode plate.

As an initial capacity test, 25 ° C., 0.2 CA
Discharge and -15 ° C-5CA discharge were performed. Each discharge duration and the voltage at the 5th second at 5CA discharge are set to N
o. Table 2 shows the results of comparison when 8 (conventional product) was set to 100.

[0041]

[Table 2]

A titanium substrate having no irregularities (No.
5) and the lead alloy substrate (No. 8) were compared, the titanium substrate had smaller discharge capacity and voltage, but this is probably because the electric resistance of titanium is about twice that of the lead alloy. Be done.

Regarding the discharge capacity and the voltage, the lead alloy substrate (No. 7) having the irregularities was the largest. This is considered to be because the contact surface area between the active material and the substrate was increased by forming the unevenness, the utilization ratio of the active material was improved, and the electric resistance was reduced.

25 ° C. of a battery (No. 2, 3, 4, 6) using a bipolar electrode plate having a titanium substrate with irregularities,
The 0.2 CA discharge capacity was almost the same as that of the battery (No. 8) using the lead alloy base bipolar electrode plate having no unevenness. Further, the discharge capacity at 5 CA and the voltage at the 5th second were slightly improved. This is because the increase in electric resistance due to the use of titanium was offset by the formation of the unevenness.

A life test was conducted on these batteries under the following conditions, and the test results are shown as No. Table 3 shows a comparison between 8 (conventional product) and 100.

Discharge: 0.75 A × 3 hours Charge: 0.54 A × 5 hours Temperature: 40 ° C. Life judgment: 0.2 CA (0.6 A) Capacity is 80% of the initial value
Life when

[0047]

[Table 3]

The life performance of the product of the present invention was very excellent.
The number of cycles of the batteries (No. 2, 3, 4, 6) using the bipolar electrode plate in which the titanium base material is formed with irregularities is the same as that of the battery using the lead alloy base bipolar plate in which the unevenness is not formed (No. 8). ) Was 7.8-9.5 times. 4 even for a battery (No. 5) that uses a titanium substrate with no irregularities
It had double the life performance.

On the other hand, in the lead alloy substrate having irregularities (No. 7), the irregularities can prevent the active material from falling off or peeling off, so that the life performance can be improved to some extent, but the substrate itself. Has corroded and leaked between cells, resulting in the end of life.

It is considered that the reason why the battery using the bipolar electrode plate of the present invention has a long life is that the corrosion of the substrate is suppressed.

[0051]

As described in detail above, in a bipolar electrode plate for a lead storage battery in which a positive electrode active material is formed on one surface and a negative electrode active material is formed on the other surface using a substrate made of a corrosion resistant metal,
A bipolar electrode plate for a lead storage battery in which a conductive oxide layer and a dense PbO ₂ layer are formed on the positive electrode active material side of the substrate, and a lead layer or a lead alloy layer is formed on the negative electrode active material side of the substrate. Since a bipolar lead acid battery having excellent life performance can be obtained by using, the industrial value thereof is extremely great.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the porosity and the reactivity of a PbO ₂ layer.

FIG. 2 is a sectional structural view showing an example of a bipolar electrode plate according to the present invention.

FIG. 3 is a view showing a substrate having hemispherical irregularities.

FIG. 4 is a view showing a base body having a rectangular parallelepiped unevenness.

FIG. 5 is a view showing a base body having wavy unevenness.

FIG. 6 is a diagram showing an example of a bipolar electrode plate.

FIG. 7 is a diagram showing a battery using a bipolar electrode plate.

FIG. 8 is a diagram showing a battery using a bipolar electrode plate.

[Explanation of symbols]

1 Corrosion-Resistant Metal Base 2 Conductive Oxide Layer 3 α-PbO ₂ 4 β-PbO ₂ 5 Positive Electrode Active Material 6 Lead or Lead Alloy Layer 7 Negative Electrode Active Material 8 Irregularities 9 Cell Separation Area 10 Positive Electrode Active Material Filled Surface 11 Negative Electrode Active material filled surface 12 Bipolar electrode plate 13 Separator 14 Positive electrode terminal 15 Negative electrode terminal 16 Resin frame 17 Liquid injection port 18. Exhaust valve

Claims (5)

[Claims] 1. A bipolar electrode plate for a lead storage battery, comprising a substrate made of a corrosion-resistant metal and having a positive electrode active material formed on one surface and a negative electrode active material formed on the other surface, wherein the positive electrode active material side of the substrate is electrically conductive. A bipolar electrode plate for a lead storage battery, characterized in that a conductive oxide layer and a dense PbO ₂ layer are formed, and a lead layer or a lead alloy layer is formed on the negative electrode active material side of the substrate. 2. The bipolar electrode plate for a lead storage battery according to claim 1, wherein the substrate made of a corrosion resistant metal is titanium, zirconium, niobium, tantalum, tungsten or a base alloy thereof. 3. The dense PbO ₂ layer is α-PbO ₂ or β-PbO ₂ , or α-PbO ₂ and β-PbO ₂
The bipolar electrode plate for a lead storage battery according to claim 1, wherein the bipolar plates are alternately laminated. 4. The lead-acid battery bipolar plate according to claim 1, wherein the dense PbO ₂ layer has 10% or less of pores having a diameter of 10 μm or less in a volume thereof. 5. The lead-acid battery bipolar plate according to claim 1, wherein the active material layer-forming surface of the substrate is provided with irregularities.