JP5574362B2 - Alkaline secondary battery - Google Patents

Description

  The present invention relates to an alkaline secondary battery such as a nickel-cadmium storage battery, and more particularly to an alkaline secondary battery including a non-sintered cadmium negative electrode having a cadmium active material applied to an electrode substrate.

  In recent years, alkaline secondary batteries represented by nickel-cadmium storage batteries have been widely used as power sources for driving electric tools and the like that require a large current. Here, in a nickel-cadmium storage battery, a nickel positive electrode using nickel hydroxide as a positive electrode active material, a cadmium negative electrode using cadmium hydroxide or metal cadmium as a negative electrode active material, and the nickel positive electrode and the cadmium negative electrode are isolated. It is comprised by the separator and the alkaline electrolyte which consists of potassium hydroxide aqueous solution.

  In the cadmium negative electrode described above, either a sintered cadmium negative electrode or a non-sintered cadmium negative electrode is used. Here, the sintered cadmium negative electrode is formed by applying a slurry containing nickel powder as a main raw material on a metal core made of punching metal, and sintering it in an inert atmosphere. It is made by impregnating cadmium. On the other hand, the non-sintered cadmium negative electrode is produced by directly applying an active material paste made of cadmium oxide and metal cadmium on a metal substrate made of punching metal.

By the way, in recent years, there has been a concern about an increase in the cost of the sintered cadmium negative electrode due to the rise in the price of nickel. For this reason, it can be used for power tool applications without using a nickel sintered substrate to reduce the amount of nickel used, and can be manufactured at a lower cost than a sintered cadmium negative electrode. The development of a non-sintered cadmium negative electrode became urgent. Therefore, in order to increase the capacity density of the non-sintered cadmium negative electrode, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-273416) proposes that the packing density of the active material be 3.4 g / cm ^3. It came to be.

JP 2007-273416 A

  However, as proposed in Patent Document 1, even if the capacity density of the non-sintered cadmium negative electrode is increased, it is required to be used in applications such as power tools for plugs as compared with the sintered cadmium negative electrode. There is a problem that this difference appears more conspicuously in a low temperature environment, particularly in the rate discharge characteristics. In this case, in order to obtain a high rate discharge characteristic under a low temperature environment, it is necessary to hold a large amount of alkaline electrolyte in the non-sintered cadmium negative electrode. Here, in a sealed state (under the condition of limiting the amount of electrolyte), if the negative electrode active material filling density is lowered to increase the amount of alkaline electrolyte retained in the non-sintered cadmium negative electrode, The discharge reaction at a low temperature will be improved.

However, even if the packing density of the active material of the non-sintered cadmium negative electrode is lowered, if the liquid retention rate of the separator to be combined is not constant during the charge / discharge reaction of the battery, electrolysis at the non-sintered cadmium negative electrode The liquid retention amount changed (decreased as the charge / discharge reaction was repeated), resulting in a problem that high-rate discharge characteristics at a low temperature as expected could not be obtained.
Therefore, the present invention has been made to solve the above-described problems, and uses a non-sintered cadmium negative electrode having an appropriate active material filling density and a separator having an appropriate tensile strength at a low temperature. It is an object of the present invention to provide an alkaline secondary battery having excellent high rate discharge characteristics.

In order to achieve the above object, the alkaline secondary battery of the present invention separates a non-sintered cadmium negative electrode having a cadmium active material applied to an electrode substrate, a positive electrode, and the non-sintered cadmium negative electrode and the positive electrode. And an alkaline electrolyte in the outer can, the separator has a tensile strength of 35 N / mm ² or more, and the non-sintered cadmium negative electrode has an active material filling density of 3.05 g / It is characterized by being less than ml.

Here, the tensile strength of a separator is mentioned as a physical property relevant to the maintenance of the liquid retention rate in a separator. This is because a separator having a high tensile strength is less susceptible to volume changes due to the expansion of the positive electrode during charge and discharge, and thus can maintain its thickness. For this reason, it is thought that the separator with high tensile strength can hold | maintain alkaline electrolyte stably. In this case, it was revealed that a high rate discharge characteristic at a low temperature can be obtained by using a separator having a tensile strength of 35 N / mm ² or more. In addition, when the tensile strength of the separator is increased to exceed 60 N / mm ² , the productivity decreases due to the increase in the thickness of the separator (occurrence of poor insertion into the outer can due to the excessive outer diameter of the winding body) The upper limit is preferably 60 N / mm ² .

On the other hand, in alkaline secondary batteries that are sealed by limiting the amount of injected alkaline electrolyte, reducing the filling density of the negative electrode active material reduces the amount of alkaline electrolyte retained in the non-sintered cadmium negative electrode. The discharge reaction at low temperature is improved. As a result of examining the packing density of the negative electrode active material, when a separator having a tensile strength of 35 N / mm ² or more is used, the packing density of the active material is 3.05 g / ml or less at a low temperature. It has become clear that high rate discharge characteristics can be obtained. Note that when the packing density of the active material is low such that it is less than 2.20 g / ml, the active material comes off. For this reason, the lower limit is desirably 2.20 g / ml.

  In the present invention, since a separator having an appropriate tensile strength and a non-sintered cadmium negative electrode having an appropriate active material filling density are used, an alkaline secondary having excellent high-rate discharge characteristics at low temperatures. A battery can be provided.

It is sectional drawing which shows the alkaline secondary battery of this invention typically. It is a graph which shows the relationship between the packing density (g / ml) of a negative electrode active material, and the high rate discharge capacity (mAh) in -10 degreeC.

  Next, an embodiment of the alkaline secondary battery of the present invention will be described in detail below based on FIG. 1 and FIG. 2, but the present invention is not limited to the following embodiment at all, and the gist thereof It is possible to carry out by appropriately changing within the range not changing.

1. Cadmium Negative Electrode Cadmium negative electrode 11 is formed by applying, drying and rolling a negative electrode active material paste composed of an active material mainly composed of cadmium oxide, a conductive agent and a binder on both surfaces of an electrode plate core 11a composed of a punching metal. It was immersed in an alkaline aqueous solution, subjected to a hydration treatment in which cadmium oxide was reacted with cadmium hydroxide, further dried and rolled to produce a predetermined packing density. Next, it is manufactured by cutting to a predetermined size. In addition, the electrode plate core 11a is exposed at the lower end portion of the cadmium negative electrode 11 after fabrication, and the electrode collector 11b is welded to the electrode plate core 11a that is exposed later.

  Here, the negative electrode x1 was applied, rolled and dried so that the packing density of the negative electrode active material was 2.85 g / ml. Similarly, the negative electrode x2 is applied, rolled and dried so that the packing density is 3.05 g / ml, and is applied, rolled and dried so that the packing density is 3.20 g / ml. Was negative electrode x3. In addition, although the cadmium negative electrode of a present Example has performed the hydration process, the cadmium negative electrode which does not perform a hydration process can also be used. In that case, the packing density of the negative electrode active material refers to the packing density after charging / discharging after the preparation of the alkaline secondary battery.

2. Nickel positive electrode The nickel positive electrode 12 is applied to the electrode plate core 12a so that a positive electrode active material mainly composed of nickel hydroxide has a predetermined packing density, dried, rolled to a predetermined thickness, It is produced by cutting so as to have a dimension of In addition, the electrode plate core body 12a is exposed at the upper end portion of the nickel positive electrode plate 12 after fabrication, and the cathode current collector 12b is welded to the exposed electrode plate core body 12a later.

3. Separator A nylon 13 non-woven fabric was cut to a predetermined size to produce a separator 13. In this case, the separator y1 was prepared so that the separator 13 had a tensile strength of 41 N / mm ² . Similarly, the tensile strength and the separator y2 to those made to be 35N / mm ^2, those tensile strength is produced so as to 24N / mm ² and a separator y3. The tensile strength of the separator 13 is measured as follows. That is, the tensile strength (N / mm ² ) when a 50 × 200 mm sample piece (separator) was gripped and the test piece was cut at a spacing of 100 mm and a tensile speed of 300 mm / min was measured.

4). Spiral electrode group A separator 13 made of a nonwoven fabric made of nylon is interposed between the cadmium negative electrode 11 and the nickel positive electrode 12, and a spiral electrode group is formed by winding in a spiral shape. In this case, the electrode plate core body 11a where the cadmium negative electrode 11 is exposed protrudes from the lower end portion of the separator 13, and the electrode plate core body 12a where the nickel positive electrode 12 is exposed protrudes from the upper end portion of the separator 13. After that, it is designed to be spirally wound. Note that a central portion of the spiral electrode group is provided with a space formed by removing the core shaft.

5. Sealed Nickel-Cadmium Storage Battery Next, a spiral electrode group is formed using the cadmium negative electrode 11 (x1, x2, x3) and the nickel positive electrode 12 manufactured as described above, and the separator 13 (y1, y2, y3). Each was produced. In this case, the cadmium negative electrode 11 (any one of x1, x2, and x3) and the nickel positive electrode 12 were wound in a spiral shape via the separator 13 (any one of y1, y2, and y3). Next, the negative electrode current collector 11b is resistance-welded to the electrode plate core 11a extending to the lower part of the spiral electrode group, and the positive electrode current collector 12b to the electrode plate core 12a extending to the upper part of the spiral electrode group. A spiral electrode body was produced by resistance welding.

  Next, after inserting the spiral electrode body into the bottomed cylindrical metal outer can 15 in which iron was plated with nickel, the negative electrode current collector 11b and the bottom of the metal outer can 15 were spot welded. On the other hand, a sealing body 17 composed of a positive electrode cap 17b and a lid body 17a is prepared, and the lead portion 12c provided on the positive electrode current collector 12b is brought into contact with the lid body bottom portion 17c so that the lid body bottom portion 17c and the lead portion 12c Welded.

  Thereafter, the vibration isolating ring 14 was inserted into the upper end surface of the spiral electrode body, and the upper outer peripheral surface of the outer can 15 was grooved to form an annular groove 15 a at the upper end portion of the vibration isolating ring 14. Thereafter, an electrolytic solution (potassium hydroxide (KOH) aqueous solution having a concentration of 30 mass%) is injected into the metal outer can 15, and the sealing body 17 is inserted into the annular groove 15 a of the outer can 15 via the sealing gasket 16. The nickel-cadmium storage battery 10 having a nominal capacity of 1200 mAh (A1, A2, A3, B1, B2, B3, C1, C2, C3) is mounted and the front end of the outer can 15 is caulked and sealed to the sealing body side. Were prepared.

Here, the separator 13 having a tensile strength of 41 N / mm ² was used, and the battery A1 was prepared using the negative electrode x1 (active material filling density was 2.85 g / ml), and the negative electrode x2 (active material filling). A battery A2 having a density of 3.05 g / ml) and a battery A3 having a negative electrode x3 (having an active material filling density of 3.20 g / ml) were used.

A separator 13 having a tensile strength of 35 N / mm ² and a negative electrode x1 (active material filling density of 2.85 g / ml) was used as battery B1, and negative electrode x2 (active material filling density). Manufactured with a negative electrode x3 (with an active material filling density of 3.20 g / ml) was referred to as a battery B3.

Further, a separator 13 having a tensile strength of 24 N / mm ² and a negative electrode x1 (active material filling density of 2.85 g / ml) was used as battery C1, and negative electrode x2 (active material filling density). Produced with the use of a negative electrode x3 (with an active material filling density of 3.20 g / ml) was designated as a battery C3.

5. Battery characteristics test Next, using each of the nickel-cadmium storage batteries A1 to A3, B1 to B3, and C1 to C3 produced as described above, each of these batteries was subjected to 1.2 A at room temperature (about 25 ° C.). When the battery voltage dropped by 10 mV after exceeding the peak voltage, charging was stopped (-ΔV method). Next, after resting for 3 hours in a temperature environment of −10 ° C., the battery was discharged with a discharge current of 10 A until the battery voltage became 0.8 V, and the discharge capacity at the time of 10 A discharge at −10 ° C. from the discharge time ( When the high rate discharge capacity at −10 ° C. was determined, the results shown in Table 1 below were obtained. Further, when the negative electrode active material packing density (g / ml) is plotted on the horizontal axis and the high-rate discharge capacity (mAh) at −10 ° C. is plotted on the vertical axis based on the results of Table 1, FIG. The results shown were obtained.

As is apparent from the results of Table 1 and FIG. 2, in the batteries C1, C2, and C3 using the separator y3 having a tensile strength of 24 N / mm ² , even if the negative electrode active material packing density is decreased, the temperature is −10 ° C. It can be seen that the high-rate discharge capacity does not increase. This is because when a separator with a weak tensile strength of 24 N / mm ² is used, the thickness cannot be maintained due to the influence of the volume change due to the positive electrode expansion during charging and discharging, and the alkaline electrolyte cannot be stably retained. It is thought that it was because of. As a result, it is considered that the high-rate discharge capacity at −10 ° C. did not increase despite the decrease in the packing density of the negative electrode active material.

On the other hand, in the batteries A1, A2, and A3 using the separator y1 having a tensile strength of 41 N / mm ² , the high rate discharge capacity at −10 ° C. tends to increase as the packing density of the negative electrode active material decreases. I understand that there is. Also in the batteries B1, B2, and B3 using the separator y2 having a tensile strength of 35 N / mm ² , the high rate discharge capacity at −10 ° C. tends to increase as the packing density of the negative electrode active material decreases. I understand that there is. This is because when a separator with high tensile strength is used, it becomes difficult to be affected by the volume change due to the expansion of the positive electrode during charging and discharging, so that the thickness can be maintained and the separator can stably hold the alkaline electrolyte. Thus, it is considered that as the filling density of the negative electrode active material decreases, the amount of the alkaline electrolyte solution of the non-sintered cadmium negative electrode increases, and the discharge reaction at a low temperature becomes better.

In this case, when a separator having a tensile strength of 35 N / mm ² or more is used, a high rate discharge characteristic at a low temperature can be obtained when the packing density of the negative electrode active material is 3.05 g / ml or less. It is. In addition, when the tensile strength of the separator is increased to exceed 60 N / mm ² , the productivity decreases due to the increase in the thickness of the separator (occurrence of poor insertion into the outer can due to the excessive outer diameter of the winding body) The upper limit is preferably 60 N / mm ² . Further, when the packing density of the active material is low, such as less than 2.20 g / ml, the active material comes off, so the lower limit is preferably 2.20 g / ml.

From the above results, in order to improve the high rate discharge characteristics at low temperature, it is necessary to use a separator having a tensile strength of 35 N / mm ² or more and to set the packing density of the negative electrode active material to 3.05 g / ml or less. It can be said. Desirably, the tensile strength of the separator is 35N / mm ² or more and 60N / mm ² or less, cadmium negative electrode packing density of the active material 2.20 g / ml or more, that preferably not more than 3.05 g / ml be able to.

  In the above-described embodiment, the example in which the present invention is applied to a nickel-cadmium storage battery has been described. However, the present invention is applicable to other alkaline storage batteries using cadmium as a negative electrode active material in addition to the nickel-cadmium storage battery. However, it is clear that the same effect can be obtained.

10, alkaline secondary battery, 11 cadmium negative electrode, 11a electrode plate core, 11b negative electrode current collector, 12 nickel positive electrode, 12a electrode plate core, 12b positive electrode current collector, 12c lead part, 13 · Separator, 14 · Anti-vibration ring, 15 · Metal outer can, 15a · Annular groove, 16 · Sealing gasket, 17 · Sealing body, 17a · Lid, 17b · Positive electrode cap, 17c · Bottom of lid

Claims (1)

An alkaline secondary battery comprising a cadmium negative electrode coated with a cadmium active material on an electrode substrate, a positive electrode, a separator separating these cadmium negative electrode and positive electrode, and an alkaline electrolyte in an outer can,
The separator 35N / mm ² or more, has a 60N / mm ² or less of the tensile strength,
The cadmium negative electrode has an active material filling density of 2.20 g / ml or more and 3.05 g / ml or less.

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