JP4999309B2 - Alkaline storage battery - Google Patents

Description

  The present invention relates to an alkaline storage battery, and more particularly to an alkaline storage battery that is used for a device that performs charge control using a battery voltage when performing rapid charging at 1C or higher.

Alkaline storage batteries, including nickel-cadmium storage batteries, have expanded their use in power tools, automated guided vehicles (hereinafter referred to as AGV), hybrid automobiles (hereinafter referred to as HEV), and the like with the recent market expansion. Accordingly, higher capacity and quick charging performance of storage batteries are desired. There are various quick charge control methods. For example, when the battery voltage reaches a predetermined voltage (end-of-charge voltage, etc.), fast charge is stopped or the charge current is reduced. -ΔV detection method that stops rapid charging when the voltage drops, battery temperature detection method that detects battery temperature change with a thermistor, etc., and stops rapid charging, detects SOC due to the balance of charge and discharge electricity, and exceeds a certain value In this case, an SOC detection method for stopping the rapid charging when it becomes, and a composite detection method combining two or more of them are used.

In recent years, AGV, HEV, and the like, which are rapidly spreading, use a battery voltage detection method frequently because the battery temperature is remarkably increased when the battery voltage reaches a predetermined voltage, and the battery performance is greatly deteriorated. At this time, in consideration of the balance between the battery's discharge output performance and charge acceptance performance, charging is controlled so that the battery does not become fully charged, and charging and discharging with a large current are frequently repeated in a partially charged state. Often to do. In the alkaline storage battery mainly used for such applications, a nickel electrode plate using nickel hydroxide as an active material is used for the positive electrode plate.

When this nickel electrode plate is charged, the nickel hydroxide as the active material becomes β-type nickel oxyhydroxide. However, when the battery is overcharged beyond the theoretical capacity, γ-type nickel oxyhydroxide is generated. So far, this γ-type nickel oxyhydroxide has been thought to be generated when the battery is overcharged, but it can be generated even if it is rapidly charged by partial charge and discharge in applications such as AGV and HEV. I know that it will be done. The cause is considered to be that there is variation in the formation of the conductive network in the electrode plate, and the rapid charging current is concentrated in a good part of the conductive network, and the active material in that part is overcharged. β-type nickel oxyhydroxide becomes β-type nickel hydroxide by discharge, while γ-type nickel oxyhydroxide becomes α-type nickel hydroxide. When a large amount of γ-type nickel oxyhydroxide or α-type nickel hydroxide is produced, the volume changes due to the expansion of the crystal unit volume, resulting in low density, easy deformation of the electrode and exfoliation from the current collector, and battery life. Cause a decline. In addition, this γ-type nickel oxyhydroxide has a high charge transfer resistance and causes a memory effect of the storage battery and an increase in charge polarization. The increase in charge polarization causes a problem that the charge amount decreases in the battery voltage detection method. For this reason, while charging and discharging are frequently repeated, charging becomes insufficient, resulting in capacity reduction.

Therefore, rapid charging of 1C or more including a negative electrode of a plastic bonded electrode that does not contain metallic nickel in the active material and an electrolyte solution of an alkaline aqueous solution having a molar concentration of more than 7M and 14M or less is performed, and a voltage based on the polarization of the negative electrode is obtained. In an alkaline storage battery that includes detecting a change to control charging (Patent Document 1), a positive electrode having an active material mainly composed of nickel hydroxide, a negative electrode, a separator, and an alkaline electrolyte, The surface of the substance is coated with a solid solution of cobalt hydroxide, nickel hydroxide, and at least one hydroxide selected from the group of Y, Al, Mn, and lanthanoid elements, and the alkaline electrolyte is coated with an alkaline electrolyte. At least potassium hydroxide is added in a molar ratio of 3 to 50% with respect to the total alkali (Patent Document 2).

Japanese Patent No. 3558082 JP 2004-235086 A

Patent Literature 1 and Patent Literature 2 have been proposed as alkaline storage batteries with improved rapid charging characteristics. However, if these batteries are repeatedly charged and discharged frequently, the capacity is reduced. Further, when a high concentration electrolyte solution proposed in Patent Document 1 and a non-sintered cadmium negative electrode plate are combined, the solubility of cadmium increases, and migration tends to occur, resulting in a short life.

Under such circumstances, it is desired to provide an alkaline storage battery that can withstand repeated repeated rapid charging and improve the battery life by optimizing the electrolyte composition.

The present invention is an alkaline storage battery that is rapidly charged with a current of 1 CA or more and is charged when the battery voltage reaches a predetermined voltage, and is a non-sintered cadmium negative electrode plate containing a nickel positive electrode plate and indium or an indium compound And an alkaline aqueous electrolyte containing lithium hydroxide and mainly potassium hydroxide and sodium hydroxide , and 0.2 to 0.7 M lithium hydroxide is added to the electrolytic solution. the total molar concentration of the electrolyte solution in the following 7M least 5M, the molar concentration ratio of potassium hydroxide and sodium hydroxide is 1: 1 to 3: characterized in that it is 1.

The γ-type nickel oxyhydroxide of the nickel positive electrode plate produced by repeated partial charge and discharge by rapid charge has variations in the formation of the conductive network in the electrode plate as described above, and the rapid charge current is good for the conductive network. This is thought to be because the active material in this part is overcharged. The aqueous potassium hydroxide solution has less resistance than the aqueous sodium hydroxide solution, and potassium has less intercalation between nickel hydroxide layers. When sodium hydroxide is added here, intercalation between nickel hydroxide layers increases. However, if the amount is large, the resistance increases. Therefore, by changing the molar concentration ratio of potassium hydroxide and sodium hydroxide in the electrolyte from 1: 1 to 3: 1, the dispersion of the conductive network in the electrode plate and the charging efficiency are improved. It is thought that generation is suppressed. Further, if the amount of sodium hydroxide is larger than the amount of potassium hydroxide such that the molar concentration ratio of the electrolytic solution is 1: 2, the memory effect tends to occur.
When the molar concentration of the electrolytic solution is less than 5M, the amount of OH ⁻ ions necessary for the rapid charge reaction is insufficient, and the charge polarization increases.
Further, lithium hydroxide is generally used to improve the charging efficiency of the positive electrode, and 0.2 to 0.7 M lithium hydroxide is added to the electrolyte. However, when the amount of lithium hydroxide added is large, the ion concentration in the electrolytic solution increases and the battery life is shortened, for example, the liquid resistance is increased.

In addition, by adding indium or an indium compound to the negative electrode plate, the utilization rate can be improved and the capacity can be increased. However, a non-sintered cadmium negative electrode plate to which indium or an indium compound is added, and water that is commonly used as an electrolyte solution are used. When a storage battery using an aqueous potassium oxide solution is rapidly charged at 1 CA or more, the charge polarization behavior appears prominently in the middle of charging, and this is caused by the fact that the non-sintered cadmium negative electrode plate to which indium is not added is discharged. Β-type cadmium hydroxide has a small particle size, but by adding indium to the negative electrode plate, cadmium into which indium has entered becomes larger in particle size, and cadmium into which indium has not entered has a smaller particle size. Thus, cadmium having a different particle size is present in the active material, so that charge polarization behavior occurs. Therefore, by adding a certain amount of sodium hydroxide which becomes γ-type cadmium hydroxide having a relatively large particle size at the time of discharging, the molar concentration ratio of the electrolyte is 3: 1 or less regardless of whether or not indium enters. It is considered that the variation in diameter can be reduced, and the charging polarization behavior appearing in the middle of charging is suppressed.

The present invention can suppress the formation of γ-type nickel oxyhydroxide on the nickel positive electrode plate by optimizing the electrolyte composition, and further uses a non-sintered negative electrode plate containing indium or an indium compound. By doing so, it is possible to suppress the charge polarization behavior, endure frequent repeated quick charge, and improve the battery life.

After preparing a sintered positive electrode plate and a non-sintered negative electrode plate to which indium or an indium compound is added by a known method, the positive electrode plate and the negative electrode plate are alternately laminated via a separator, The current collector was welded, and then the current collector and the pole column were joined by welding to produce an electrode plate group. The electrode plate group is inserted into a battery case, and an appropriate amount of each of an alkaline aqueous solution of potassium hydroxide and sodium hydroxide having a predetermined composition is injected to produce a sealed prismatic nickel-cadmium alkaline storage battery.

(Manufacture of positive electrode plate)
A sintered substrate obtained by sintering metallic nickel powder into a nickel-plated porous sheet is impregnated with a nickel nitrate aqueous solution containing cobalt nitrate, and a series of steps of heat treatment, alkali treatment, water washing and drying are repeated a predetermined number of times, An approximately predetermined amount was obtained. Then, impregnated with a cadmium nitrate aqueous solution of a predetermined concentration, heat treated, alkali treated, washed with water and dried to give cadmium hydroxide to the surface of the active material, cut to a predetermined size, and fired with a design capacity of 3.4 Ah. A sintered nickel positive electrode plate was produced.
(Manufacture of negative electrode plate)
Next, cadmium oxide and metal cadmium in an amount equivalent to about 20% precharge are used as the main active material, and an active material paste to which a predetermined amount of indium is added is applied to a nickel-plated porous sheet, dried, and a predetermined dimension. And a non-sintered cadmium negative electrode plate having a design capacity of 5.8 Ah was produced.
(Battery assembly, electrolyte preparation and formation)
Then, 24 of these sintered nickel positive plates and 25 of non-sintered cadmium negative plates were alternately stacked via a 0.2 mm thick separator, and then the ears of the same polarity plate were collected. Then, the current collector and the pole column were joined together by welding to prepare an electrode plate group. This is housed in a metallic battery case, and after injecting a predetermined amount of an alkaline aqueous electrolyte solution having a molar concentration and a molar concentration ratio, the metallic battery case is sealed, and a rectangular sealed nickel nickel alloy with a nominal capacity of 60 Ah is sealed. Cadmium storage batteries were produced respectively. The electrolyte is mainly composed of potassium hydroxide and sodium hydroxide, and a small amount of lithium hydroxide (the addition amount of lithium hydroxide is about 10 g / l: 0.5 M, hereinafter, the addition amount of lithium hydroxide is about 10 g. / L), the total molar concentration of the electrolyte is 6M, and the molar concentration ratio of potassium hydroxide and sodium hydroxide is 1: 1 (invention product 1), 2: 1 (invention product 2), 3: 1 (Invention product 3).

The nominal capacity of 60 Ah was the same as in Example 1 except that the molar concentration ratio of potassium hydroxide and sodium hydroxide was 2: 1 and the total molar concentration of the electrolyte was 5 M and 7 M, respectively (Products 4 and 5 of the present invention). Each of the square sealed nickel-cadmium storage batteries was prepared.

(Comparative Example 1)
A square sealed nickel-cadmium storage battery having a nominal capacity of 60 Ah was prepared in the same manner as in Example 1 except that potassium hydroxide was not added to the electrolyte and the total molar concentration of the electrolyte was 6M.
(Comparative Example 2)
A square sealed nickel-cadmium storage battery with a nominal capacity of 60 Ah was prepared in the same manner as in Example 1 except that the molar concentration ratio of potassium hydroxide and sodium hydroxide was 5: 1 and the total molar concentration of the electrolyte was 6M. did.
(Comparative Examples 3 and 4)
The nominal capacity of 60 Ah was the same as in Example 1 except that the molar concentration ratio of potassium hydroxide and sodium hydroxide was 2: 1 and the total molar concentration of the electrolyte was 4 M and 8 M, respectively (Comparative Examples 3 and 4). Each of the square sealed nickel-cadmium storage batteries was produced.
(Comparative Example 5)
A square sealed nickel-cadmium storage battery having a nominal capacity of 60 Ah was prepared in the same manner as in Example 1 except that the molar concentration of the potassium hydroxide aqueous solution was 7 M and sodium hydroxide was not added.
Table 1 shows the molar concentration ratio, the electrolytic solution molar concentration, and the total electrolytic solution molar concentration of Examples 1 to 5 and Comparative Examples 1 to 5.

(Quick charge cycle test)
A cycle life test of each of the square sealed nickel-cadmium storage batteries prepared above was performed as follows. First, as activation charge / discharge, 150% charge was performed with a constant current of 0.1 CA, and discharge was performed with a current of 0.2 CA until the storage battery voltage became 1.0 V, and activation charge / discharge was performed.
Then, after performing activation charge / discharge, as a rapid charge cycle test, a constant current charge of 5.5 Hr was performed at a current of 0.2 CA, and each of the square sealed nickel-cadmium storage batteries was fully charged. Then, a cycle test in which the battery was discharged at a current of 0.2 CA for 5 minutes and charged to 1.56 V at a current of 3 CA was repeated for 90 days. The test was conducted at an ambient temperature of 25 ± 5 ° C. FIG. 1 shows the transition characteristics of the end-of-discharge voltage during the cycle of the quick charge cycle test.

Comparative Example 1 is A, Invention Product 1 is B, Invention Product 2 is C, Invention Product 3 is D, Comparison Example 2 is E, Comparison Example 3 is F, Invention Product 4 is G, Invention Product 5 The characteristics are shown in the figure as H, Comparative Example 4 as I, and Comparative Example 5 as J. As shown in FIG. 1, none of the present invention products 1 to 3, present invention products 4 and 5 and Comparative Example 4 indicated by B, C, D, G, H and I show almost no decrease in the end-of-discharge voltage. The charge / discharge cycle test was successfully performed for 90 days, whereas in Comparative Examples 1-2 and 5 shown by A, E, and J, the end-of-discharge voltage decreased early, and the charge / discharge cycle test could be performed halfway I'm gone. The inventive products 1 to 3 (B, C, D), the inventive product 5 (H), and Comparative Example 4 (I) are the production of γ-type nickel oxyhydroxide in the positive electrode plate and the charge polarization behavior due to indium in the negative electrode plate. It is thought that this has been achieved. On the other hand, as a result of measuring the potential behavior of the electrode plates of Comparative Examples 1 and 2 (A, E) and Comparative Example 5 (J) in which the end-of-discharge voltage decreased early, as a result of measuring the potential behavior of the electrode plate, In Comparative Example 1 (A), the charge polarization of the positive electrode was large, and thus it is considered that γ-type nickel oxyhydroxide was generated and the charge amount was reduced. Comparative Examples 2, 5 (E, I) were Charge polarization behavior due to indium appeared on the negative electrode at an earlier stage than the predetermined charge, the battery voltage increased, and the charge stopped earlier than the predetermined charge amount. In addition, although the product 4 (G) of the present invention showed a somewhat unstable behavior with the end-of-discharge voltage increasing and decreasing, it was possible to continue the 90-day charge / discharge cycle test. In Comparative Example 3 (F), the end-of-discharge voltage did not decrease early, but the upper and lower ends of the end-of-discharge voltage were large and could not be sustained for 90 days. In the product 4 (G) of the present invention and the comparative example 3 (F), the end-of-discharge voltage was increased and unstable behavior was observed because the charge start polarization of the negative electrode increased at the portion where the end-of-discharge voltage decreased. Therefore, it is considered that the amount of OH ⁻ ions necessary for the quick charge reaction is insufficient.

(Rapid charge / discharge life test)
Next, a rapid charge / discharge life test was performed on the prepared square sealed nickel-cadmium storage battery. First, as activation charge / discharge, a constant current charge of 150% with a current of 0.1 CA, and a discharge with a current of 0.2 CA up to a voltage of 1.0 V, each of the present invention products 2, 4, 5 and Comparative Examples 3, 4 This was performed on a rectangular sealed nickel-cadmium storage battery. Then, after the activation charge / discharge, as a quick charge life test, first, a constant current charge of 5.5 Hr was performed with a current of 0.2 CA, and each of the square sealed nickel-cadmium storage batteries was fully charged. Then, a rapid charge / discharge life test was conducted by repeating the cycle of discharging at 3 CA current for 2 minutes and charging to 1.6 V at 3 CA current. The discharge capacity was confirmed every 2,000 times. The discharge capacity was confirmed by discharging the battery voltage to 1.0 V with a current of 0.2 CA, and then performing a constant current charge of 5.5 Hr with a current of 0.2 CA. The ambient temperature was an active overcharge test at 25 ± 5 ° C. and a rapid charge / discharge life test at 20 ± 5 ° C. In addition, the quick charge life test was conducted until each battery reached the end of its life even after exceeding 40,000 cycles. FIG. 2 shows discharge characteristics in the rapid charge / discharge life test. The vertical axis represents the capacity maintenance ratio in which each discharge capacity is shown as a ratio with the rated capacity being 100. The horizontal axis is the number of cycles.

As in FIG. 1, the product of the present invention 2 is C, the product 4 of the present invention is G, the product of the present invention 5 is H, the comparative example 3 is F, and the comparative example 4 is I. As shown in FIG. 2, the inventive product 2 (C), the inventive product 4 (G), the inventive product 5 (H) and the comparative example 3 (F) exceeded 40,000 cycles. 4 (I) could not exceed 40,000 cycles. Further, the product 5 (H) of the present invention and the comparative example 4 (I) suddenly reached the end of their lives. As a result of disassembling and investigating each battery that had reached the end of its life, it was confirmed that an internal short circuit occurred due to migration of cadmium in the product 5 (H) and Comparative Example 4 (I) that suddenly reached the end of life. From this, it was confirmed that migration of cadmium tends to occur as the molar concentration of the electrolytic solution increases.

As described above, from the results of the quick charge cycle life test and the quick charge / discharge life test , 0.2 to 0.7 M lithium hydroxide is added to the electrolyte solution, and the total molar concentration of the electrolyte solution is 5 M or more and 7 M or less. By making the molar concentration ratio of potassium hydroxide and sodium hydroxide 1: 1 to 3: 1, the formation of γ-type nickel oxyhydroxide on the nickel positive electrode plate can be suppressed, and indium or an indium compound is added. By using the included non-sintered negative electrode plate, it is possible to suppress the charge polarization behavior, withstand repeated frequent rapid charging, and to improve the battery long life.

Transition of end-of-discharge voltage in the quick charge cycle of the present invention. Transition of discharge capacity maintenance rate in the rapid charge / discharge life test of the present invention.

Claims (1)

An alkaline storage battery that is rapidly charged with a current of 1 CA or more and is charged when the battery voltage reaches a predetermined voltage, a nickel positive electrode plate, a non-sintered cadmium negative electrode plate containing indium or an indium compound, An alkaline aqueous electrolyte containing potassium hydroxide and sodium hydroxide , and 0.2 to 0.7 M lithium hydroxide is added to the electrolytic solution. An alkaline storage battery having a total molar concentration of 5 M or more and 7 M or less and a molar concentration ratio of potassium hydroxide and sodium hydroxide of 1: 1 to 3: 1.