Nickel-hydrogen storage battery

Abstract

The invention provides a nickel-hydrogen storage battery capable of reducing DC internal resistance. This nickel-hydrogen storage battery is provided with: a positive electrode obtained by filling a foamed nickel substrate with a positive electrode active material mainly composed of nickel hydroxide; a negative electrode containing a hydrogen storage alloy as a negative electrode active material; a separator for separating the positive electrode from the negative electrode; and an electrolyte solution. A plurality of protrusions are formed on the surface of the skeleton of the foamed nickel substrate. The value K / D obtained by dividing the particle diameter K of the nickel hydroxide by the protruding height of the protrusions on the skeleton surface of the foamed nickel substrate is in the range of 3.8-5.8. The value K / D obtained by dividing the particle diameter K of the nickel hydroxide by the interval D between the protrusions on the skeleton surface of the foamed nickel substrate is in the range of 0.8-1.5.

Description

Technical Field

[0001] The present invention relates to a nickel-hydrogen storage battery. Background Art

[0002] Conventionally, as a nickel-hydrogen storage battery, for example, a nickel-hydrogen storage battery shown in Patent Document 1 has been known. Such a nickel-hydrogen storage battery includes a positive electrode containing a positive electrode active material mainly composed of nickel hydroxide, a negative electrode containing a hydrogen storage alloy as a negative electrode active material, a separator, and an electrolytic solution. Prior Art Documents Patent Documents

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-67683 Summary of the Invention Problems to be Solved by the Invention

[0004] In addition, for the above nickel-hydrogen storage battery, generally, the smaller the DC internal resistance, the better the performance. Therefore, a nickel-hydrogen storage battery capable of further reducing the DC internal resistance is desired. Means for Solving the Problems

[0005] A nickel-hydrogen storage battery according to an aspect of the present disclosure is a nickel-hydrogen storage battery including a positive electrode in which a positive electrode active material mainly composed of nickel hydroxide is filled into a foamed nickel substrate, a negative electrode containing a hydrogen storage alloy as a negative electrode active material, a separator that separates the positive electrode and the negative electrode, and an electrolytic solution, wherein a plurality of convex portions are formed on a surface of a skeleton of the foamed nickel substrate, and a value obtained by dividing a particle diameter of the nickel hydroxide by a protruding height of the convex portions on the surface of the skeleton of the foamed nickel substrate is in a range of 3.8 or more and 5.8 or less, and a value obtained by dividing the particle diameter of the nickel hydroxide by a distance between the convex portions on the surface of the skeleton of the foamed nickel substrate is in a range of 0.8 or more and 1.5 or less.

[0006] Generally, for a nickel-hydrogen storage battery, it can be said that the smaller the DC internal resistance, the better the performance. Therefore, the present inventors have found that in a nickel-hydrogen storage battery, by changing a value obtained by dividing a particle diameter of nickel hydroxide by a protruding height of convex portions on a surface of a skeleton of a foamed nickel substrate and a value obtained by dividing the particle diameter of nickel hydroxide by a distance between the convex portions on the surface of the skeleton of the foamed nickel substrate, the DC internal resistance changes.

[0007] That is, the present inventors have found that by designing the positive electrode such that the value obtained by dividing the particle diameter of nickel hydroxide by the protruding height of the convex portions on the skeleton surface of the foamed nickel substrate is in the range of 3.8 or more and 5.8 or less, and the value obtained by dividing the particle diameter of nickel hydroxide by the interval between the convex portions on the skeleton surface of the foamed nickel substrate is in the range of 0.8 or more and 1.5 or less, the DC internal resistance of the nickel-metal hydride storage battery is reduced. Therefore, according to the above configuration, the DC internal resistance of the nickel-metal hydride storage battery can be reduced.

[0008] In the above nickel-metal hydride storage battery, the value obtained by dividing the particle diameter of the above nickel hydroxide by the protruding height of the above convex portions on the skeleton surface of the above foamed nickel substrate is in the range of 4.3 or more and 5.5 or less, and the value obtained by dividing the particle diameter of the above nickel hydroxide by the interval between the above convex portions on the skeleton surface of the above foamed nickel substrate is in the range of 0.9 or more and 1.3 or less.

[0009] The present inventors have found that by designing the positive electrode such that the value obtained by dividing the particle diameter of nickel hydroxide by the protruding height of the convex portions on the skeleton surface of the foamed nickel substrate is in the range of 4.3 or more and 5.5 or less, and the value obtained by dividing the particle diameter of nickel hydroxide by the interval between the convex portions on the skeleton surface of the foamed nickel substrate is in the range of 0.9 or more and 1.3 or less, the DC internal resistance of the nickel-metal hydride storage battery is further reduced. Therefore, according to the above configuration, the DC internal resistance of the nickel-metal hydride storage battery can be further reduced. Advantages of the Invention

[0010] The present invention has the effect of being able to reduce the DC internal resistance of the nickel-metal hydride storage battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a cross-sectional view of an electrode group of a nickel-metal hydride storage battery according to an embodiment. Figure 2 is an enlarged schematic view of a foamed nickel substrate. Figure 3 is Figure 2 an enlarged view of part A in Figure 4 is a graph showing the relationship between the ratio of the DC internal resistance to the comparative example and the value obtained by dividing the particle diameter of nickel hydroxide by the protruding height of the convex portions on the skeleton surface of the foamed nickel substrate. Figure 5 is a graph showing the relationship between the ratio of the DC internal resistance to the comparative example and the value obtained by dividing the particle diameter of nickel hydroxide by the interval between the convex portions on the skeleton surface of the foamed nickel substrate. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment will be described below with reference to the drawings. <Nickel-metal hydride storage battery 11> As shown Figure 1 in Figure 1 , the nickel-metal hydride storage battery 11 of the present embodiment is a battery module housed in a battery pack of a nickel-metal hydride storage battery for driving mounted on a vehicle such as an electric vehicle. Each battery module includes a battery case having a plurality (for example, eight) electrolytic cells.

[0013] An electrode group 14 including a positive electrode plate 12 constituting a positive electrode and a negative electrode plate 13 constituting a negative electrode as battery elements is housed in the battery case. A battery cell is formed by further filling an electrolyte 15 in the battery case. A plurality of battery cells are connected in series and power is input and output through external terminals.

[0014] <Electrode group 14> As shown Figure 1 in Figure 1 , the electrode group 14 of the nickel-metal hydride storage battery 11 is constituted by alternately laminating a plurality of rectangular positive electrode plates 12 and a plurality of rectangular negative electrode plates 13 with a separator 16 interposed therebetween. The positive electrode plate 12 and the negative electrode plate 13 of the electrode group 14 each include a positive electrode lead-out portion 17 and a negative electrode lead-out portion 18 formed by protruding from side portions in the plane direction of the electrode plate and on opposite sides.

[0015] A positive electrode current collector plate 19 is joined to the side edge of the positive electrode lead-out portion 17 by spot welding or the like. On the other hand, a negative electrode current collector plate 20 is joined to the side edge of the negative electrode lead-out portion 18 by spot welding or the like. The separator 16 disposed between the positive electrode plate 12 and the negative electrode plate 13 is impregnated with the electrolyte 15.

[0016] <Positive electrode plate 12> As shown Figures 1 to 3 in Figures 1 to 3 , the positive electrode plate 12 includes a foamed nickel substrate 21 as a substrate made of a porous material. The foamed nickel substrate 21 is manufactured by, for example, nickel-plating a foamed urethane. A positive electrode composite material is filled in the foamed nickel substrate 21. The positive electrode composite material includes a positive electrode active material mainly composed of nickel hydroxide, a conductive material, a thickening material, a binder material, and the like.

[0017] As shown Figure 2 and Figure 3 in Figure 3 , a plurality of convex portions 23 are formed on the surface of the skeleton 22 of the foamed nickel substrate 21. The skeleton 22 is a portion other than the pores 24 of the porous material constituting the foamed nickel substrate 21. Since the surface of the skeleton 22 of the foamed nickel substrate 21 is made of nickel, the plurality of convex portions 23 are also made of nickel. The particle size K of nickel hydroxide is, for example, in the range of 5.0 μm or more and 15.0 μm or less. For example, the particle size K of nickel hydroxide is an average particle size, which means the median diameter (D50) in the frequency distribution measured by the laser diffraction method.

[0018] <Negative electrode plate 13> As shown Figure 1As shown, in the negative electrode plate 13, the negative electrode composite material is coated on a substrate made of a metal porous body such as a punched metal. The negative electrode composite material contains a hydrogen storage alloy as a negative electrode active material, a thickening material, and a binder material. The hydrogen storage alloy is an alloy that reversibly stores and releases hydrogen.

[0019] <Separator 16> As Figure 1 shown, the separator 16 is composed of a non-woven fabric of an olefin resin such as polypropylene, or a material obtained by subjecting it to a hydrophilic treatment such as sulfonation as needed. The separator 16 has a function of isolating the positive electrode plate 12 and the negative electrode plate 13 to prevent short circuit. The separator 16 further has a function of retaining the electrolyte 15 and causing a reaction in the electrode. The electrolyte 15 is an alkaline aqueous solution having potassium hydroxide as a main component of the solute.

[0020] <Relationship between the foamed nickel substrate 21 and nickel hydroxide in the positive electrode plate 12> As Figures 1 to 5 shown, in the nickel-metal hydride battery 11, by changing the value K / H obtained by dividing the particle diameter K of nickel hydroxide (the main component of the positive electrode active material) by the protrusion height H of the protrusions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21, and the value K / D obtained by dividing the particle diameter K of nickel hydroxide by the interval D between the protrusions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21, the DC internal resistance (DC-IR) changes. Generally, the smaller the DC internal resistance, the better the performance of the nickel-metal hydride battery 11. For example, the protrusion height H of the protrusions 23 and the interval D between the protrusions 23 are average values, and are obtained by image analysis of an electron microscope photograph.

[0021] Figure 4 is a graph showing the relationship between the ratio R of the DC internal resistance to the comparative example when an existing nickel-metal hydride battery is used as a comparative example and the above value K / H. Figure 4 In the graph of, the open circle P1 represents the comparative example, the above value K / H is 3.6, and the above ratio R is 100%. Figure 4 In the graph of, the case where the above ratio R is less than 100% is the solid circles Q1 to Q6.

[0022] Figure 4 In the graph of, at the solid circle Q1, the above value K / H is 3.8 and the above ratio R is 99.3%, at the solid circle Q2, the above value K / H is 4.3 and the above ratio R is 98.4%, at the solid circle Q3, the above value K / H is 4.7 and the above ratio R is 98.7%, at the solid circle Q4, the above value K / H is 5.1 and the above ratio R is 98.4%, at the solid circle Q5, the above value K / H is 5.5 and the above ratio R is 98.4%, and at the solid circle Q6, the above value K / H is 5.8 and the above ratio R is 99.5%.

[0023] Therefore, according to Figure 4 In the nickel-metal hydride storage battery 11, with reference to the figure, in order to reduce the DC internal resistance, it is preferable that the above value K / H is in the range of not less than the solid circle Q1 and not more than the solid circle Q6, that is, the above value K / H is in the range of 3.8 or more and 5.8 or less. In this case, the above ratio R is in the range of 98.4% or more and 99.5 or less. In addition, according to Figure 4 In the nickel-metal hydride storage battery 11, with reference to the figure, in order to reduce the DC internal resistance, it is more preferable that the above value K / H is in the range of not less than the solid circle Q2 and not more than the solid circle Q5, that is, the above value K / H is in the range of 4.3 or more and 5.5 or less. In this case, the above ratio R is in the range of 98.4% or more and 98.7% or less.

[0024] Figure 5 The figure shows the relationship between the ratio R of the DC internal resistance to the comparative example when the existing nickel-metal hydride storage battery is used as a comparative example and the above value K / D. Figure 5 In the figure, the open circle P2 represents the comparative example, the above value K / D is 1.8, and the above ratio R is 100%. Figure 5 In the figure, the cases where the above ratio R is less than 100% are the solid circles Q7 to Q11.

[0025] Figure 5 In the figure, at the solid circle Q7, the above value K / D is 0.8 and the above ratio R is 99.0%; at the solid circle Q8, the above value K / D is 0.9 and the above ratio R is 98.6%; at the solid circle Q9, the above value K / D is 1.0 and the above ratio R is 98.6%; at the solid circle Q10, the above value K / D is 1.3 and the above ratio R is 98.9%; at the solid circle Q11, the above value K / D is 1.5 and the above ratio R is 99.7%.

[0026] Therefore, according to Figure 5 In the nickel-metal hydride storage battery 11, with reference to the figure, in order to reduce the DC internal resistance, it is preferable that the above value K / D is in the range of not less than the solid circle Q7 and not more than the solid circle Q11, that is, the above value K / D is in the range of 0.8 or more and 1.5 or less. In this case, the above ratio R is in the range of 98.6% or more and 99.7% or less. In addition, according to Figure 5 In the nickel-metal hydride storage battery 11, with reference to the figure, in order to reduce the DC internal resistance, it is more preferable that the above value K / D is in the range of not less than the solid circle Q8 and not more than the solid circle Q10, that is, the above value K / D is in the range of 0.9 or more and 1.3 or less. In this case, the above ratio R is in the range of 98.6% or more and 98.9% or less.

[0027] <Function of the Embodiment> In the nickel-metal hydride storage battery 11, the positive electrode plate 12 is configured such that the above value K / H is in the range of 3.8 or more and 5.8 or less, and the above value K / D is in the range of 0.8 or more and 1.5 or less. Thus, in the nickel-metal hydride storage battery 11, compared with the comparative example, the DC internal resistance is reduced, and thus the performance is better than that of the comparative example.

[0028] <Effect of the Embodiment> According to the embodiment described in detail above, the following effects are exhibited. (1) The nickel-metal hydride storage battery 11 includes a positive electrode in which a positive electrode active material mainly composed of nickel hydroxide is filled in a foamed nickel substrate 21, a negative electrode including a hydrogen storage alloy as a negative electrode active material, a separator 16 that separates the positive electrode and the negative electrode, and an electrolytic solution 15. A plurality of convex portions 23 are formed on the surface of the skeleton 22 of the foamed nickel substrate 21. The value K / H obtained by dividing the particle diameter K of nickel hydroxide by the protruding height H of the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21 is in the range of 3.8 or more and 5.8 or less. The value K / D obtained by dividing the particle diameter K of nickel hydroxide by the interval D between the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21 is in the range of 0.8 or more and 1.5 or less.

[0029] Generally, for the nickel-metal hydride storage battery 11, it can be said that the smaller the DC internal resistance, the better the performance. Therefore, the present inventors found that in the nickel-metal hydride storage battery 11, by changing the value K / H obtained by dividing the particle diameter K of nickel hydroxide by the protruding height H of the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21, and the value K / D obtained by dividing the particle diameter K of nickel hydroxide by the interval D between the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21, the DC internal resistance changes.

[0030] That is, the present inventors found that by designing the positive electrode such that the value K / H obtained by dividing the particle diameter K of nickel hydroxide by the protruding height H of the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21 is in the range of 3.8 or more and 5.8 or less, and the value K / D obtained by dividing the particle diameter K of nickel hydroxide by the interval D between the convex portions 23 on the surface of the skeleton 22 of the foamed nickel substrate 21 is in the range of 0.8 or more and 1.5 or less, the DC internal resistance of the nickel-metal hydride storage battery 11 is reduced. Therefore, according to the above configuration, the DC internal resistance of the nickel-metal hydride storage battery 11 can be reduced. Therefore, it is possible to contribute to the improvement of the performance of the nickel-metal hydride storage battery 11.

[0031] (2) In the nickel-metal hydride storage battery 11, the above value K / H is in the range of 4.3 or more and 5.5 or less, and the above value K / D is in the range of 0.9 or more and 1.3 or less. The present inventor has found that by designing the positive electrode such that the above value K / H is in the range of 4.3 or more and 5.5 or less, and the above value K / D is in the range of 0.9 or more and 1.3 or less, the DC internal resistance of the nickel-metal hydride storage battery 11 can be further reduced. Therefore, according to the above configuration, the DC internal resistance of the nickel-metal hydride storage battery 11 can be further reduced. Therefore, it is possible to further contribute to the improvement of the performance of the nickel-metal hydride storage battery 11.

[0032] <Modified Example> The above-described embodiment can be implemented with the following modifications. In addition, the above-described embodiment and the following modified examples can be implemented in combination with each other within a technically non-contradictory range.

[0033] · In the nickel-metal hydride storage battery 11, it is not necessarily required that the above value K / H is in the range of 4.3 or more and 5.5 or less and the above value K / D is in the range of 0.9 or more and 1.3 or less. · In the nickel-metal hydride storage battery 11 of the present embodiment, the vehicle drive battery module has been described as an example, but it is not limited to the battery use, and in addition to aircraft and ships, it can also be used for stationary use.

Claims

1. A nickel-metal hydride storage battery comprising a positive electrode formed by filling a foamed nickel substrate with a positive electrode active material mainly composed of nickel hydroxide, a negative electrode containing a hydrogen storage alloy as a negative electrode active material, a separator separating the positive electrode from the negative electrode, and an electrolyte, wherein: A plurality of convex portions are formed on the surface of the skeleton of the foamed nickel substrate. The value obtained by dividing the particle size of the nickel hydroxide by the protrusion height of the protrusions on the skeleton surface of the foamed nickel substrate is in the range of 3.8 to 5.

8. The value obtained by dividing the particle diameter of the nickel hydroxide by the interval between the protrusions on the surface of the skeleton of the foamed nickel substrate is in the range of 0.8 to 1.

5.

2. The nickel-metal hydride storage battery according to claim 1, characterized in that: The value obtained by dividing the particle size of the nickel hydroxide by the protrusion height of the convex portion on the skeleton surface of the foamed nickel substrate is in the range of 4.3 to 5.

5. The value obtained by dividing the particle diameter of the nickel hydroxide by the interval between the protrusions on the surface of the skeleton of the foamed nickel substrate is in the range of 0.9 to 1.3.

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