Electrode group and zinc battery

Abstract

A zinc battery 1 comprises an electrode group 10. The electrode group 10 comprises alternately layered negative electrodes 12 and positive electrodes 14. The negative electrodes 12 include negative electrodes A1–A3 as first through third negative electrodes counted from one end side in the layering direction of the negative electrodes 12 and the positive electrodes 14 of the electrode group 10, and the negative electrodes A1–A3 include negative electrode materials a11, a12, a21, a22, a31, and a32 that contain an active material that includes zinc, the mass of the active material of the negative electrode A2 being greater than the mass of the active material of the negative electrode A3.

Description

Electrode group and zinc battery

[0001] The present disclosure relates to an electrode group, a zinc battery, and the like.

[0002] Known zinc batteries include nickel-zinc batteries, air-zinc batteries, and silver-zinc batteries. For example, nickel-zinc batteries are aqueous batteries that use an aqueous electrolyte such as a potassium hydroxide solution, and are therefore highly safe. Furthermore, due to the combination of zinc electrodes and nickel electrodes, they are known to have a high electromotive force for an aqueous battery. Furthermore, nickel-zinc batteries have excellent input / output performance and low cost, and therefore are being considered for use in industrial applications (e.g., backup power sources) and automotive applications (e.g., hybrid vehicles). Known negative electrodes for zinc batteries include, for example, negative electrodes manufactured using a mixture composition containing zinc oxide, a binder, a conductive additive, a water-soluble polymer, and a solvent (see, for example, Patent Document 1 below).

[0003] JP 2019-160793 A

[0004] Zinc batteries are required to have excellent life performance.

[0005] An object of one aspect of the present disclosure is to provide an electrode group that enables a zinc battery having excellent life performance to be obtained.An object of another aspect of the present disclosure is to provide a zinc battery having excellent life performance.

[0006] The present disclosure relates to the following items [1] to

[22] , etc. [1] An electrode group including negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as first to third negative electrodes counting from one end side in a stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode A2 is greater than the mass of the active material in negative electrode A3. [2] The electrode group according to item [1], wherein the negative electrode A1 is located at the one end side in a stacking direction of the negative electrodes and the positive electrodes in the electrode group. [3] The electrode group according to [1] or [2], wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode B2 is greater than the mass of the active material in negative electrode B3. [4] The electrode group according to [3], wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes. [5] An electrode group including a negative electrode and a positive electrode stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as first to third negative electrodes counting from one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of negative electrode A2 is greater than the mass of negative electrode A3. [6] The electrode group according to [5], wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes. [7] The electrode group according to [5] or [6], wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 have a negative electrode material containing an active material containing zinc, and the mass of the negative electrode B2 is greater than the mass of the negative electrode B3. [8] The electrode group according to [7], wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.[9] An electrode group including negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as first to third negative electrodes counting from one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes A1 to A3 contain a negative electrode material containing zinc, and the average thickness of the negative electrode A2 is greater than the average thickness of the negative electrode A3.

[10] The electrode group according to [9], wherein the negative electrode A1 is located at the one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

[11] The electrode group according to [9] or

[10] , wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 contain a negative electrode material containing zinc, and the average thickness of the negative electrode B2 is greater than the average thickness of the negative electrode B3.

[12] The electrode group according to

[11] , wherein the negative electrode B1 is located at the other end in a stacking direction of the negative electrodes and the positive electrodes in the electrode group.

[13] An electrode group including negative electrodes and positive electrodes stacked on each other, the negative electrodes include negative electrodes A1 to A3 as first to third negative electrodes counting from one end in a stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrode A2 has a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode A3, the negative electrode A3 has a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode A2, the negative electrode material of the negative electrode A2 and the negative electrode A3 contain an active material containing zinc, and the average thickness of the negative electrode material of the negative electrode A2 is greater than the average thickness of the negative electrode material of the negative electrode A3.

[14] The electrode group according to

[13] , wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrode and the positive electrode.

[15] The electrode group according to

[13] or

[14] , wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrode B2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B3, the negative electrode B3 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B2, the negative electrode material of the negative electrode B2 and the negative electrode B3 contain an active material containing zinc, and the average thickness of the negative electrode material of the negative electrode B2 is greater than the average thickness of the negative electrode material of the negative electrode B3.

[16] The electrode group according to

[15] , wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

[17] An electrode group including negative electrodes and positive electrodes stacked on each other, the negative electrodes including negative electrode A1 and negative electrode A2 as first and second negative electrodes counting from one end side in a stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrode A1 having a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode A2, the negative electrode A2 having a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode A1, the negative electrode material of negative electrode A1 and the negative electrode A2 containing an active material containing zinc, the average thickness of the negative electrode material of negative electrode A2 being greater than the average thickness of the negative electrode material of negative electrode A1.

[18] The electrode group according to

[17] , wherein the negative electrode A1 is located at the one end side in the stacking direction of the negative electrodes and the positive electrodes in the electrode group.

[19] The electrode group according to

[17] or

[18] , wherein the negative electrodes include negative electrode B1 and negative electrode B2 as first and second negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrode B1 has a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode B2, the negative electrode B2 has a current collector and a negative electrode material arranged on a surface of the current collector facing the negative electrode B1, the negative electrode material of negative electrode B1 and the negative electrode B2 contain an active material containing zinc, and the negative electrode material of negative electrode B2 has an average thickness greater than the average thickness of the negative electrode material of negative electrode B1.

[20] The electrode group according to

[19] , wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

[21] A zinc battery comprising the electrode group according to any one of [1] to

[20] .

[22] The zinc battery according to

[21] , which is a nickel-zinc battery.

[0007] According to one aspect of the present disclosure, it is possible to provide an electrode group that can obtain a zinc battery having excellent life performance. According to another aspect of the present disclosure, it is possible to provide a zinc battery having excellent life performance.

[0008] FIG. 1 is a schematic cross-sectional view showing an example of a zinc battery.

[0009] In this specification, numerical ranges indicated using "to" indicate a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. A numerical range "A or greater" means a range exceeding A and A. A numerical range "A or less" means a range less than A and A. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. In numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. The term "layer" encompasses structures that are formed over the entire surface as well as structures that are formed only partially when observed in a plan view. "(Meth)acrylic" refers to at least one of acrylic and its corresponding methacrylic. In this specification, "average thickness" refers to the average value of thicknesses at nine locations, including the center of the object and eight locations surrounding the center on the periphery of the object when viewed from a direction perpendicular to the main surface of the object. If the object is rectangular, the eight locations surrounding the center on the periphery of the object can be four corners of the object and four intermediate locations between adjacent corners. The total thickness of the object can be obtained using a micrometer. The thickness of some components constituting the object can be obtained by observing the cross section of the object and measuring the thickness of some of the components.

[0010] Hereinafter, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments and can be implemented in various modifications within the scope of the present disclosure.

[0011] The electrode group according to this embodiment (including the electrode groups according to the first to fifth embodiments described below; the same applies hereinafter) comprises a negative electrode and a positive electrode stacked on top of each other. As described below, the electrode group according to this embodiment can be used as an electrode group for a zinc battery by using a negative electrode material containing an active material containing zinc. The electrode group according to this embodiment may be either before or after chemical formation.

[0012] In the electrode group according to the first embodiment, the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, and negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode A2 is greater than the mass of the active material in negative electrode A3.

[0013] In the electrode group according to the second embodiment, the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, and negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of negative electrode A2 is greater than the mass of negative electrode A3.

[0014] In the electrode group according to the third embodiment, the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, and negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the average thickness of negative electrode A2 is greater than the average thickness of negative electrode A3.

[0015] In the electrode group according to the fourth embodiment, the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, negative electrode A2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A3, negative electrode A3 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A2, the negative electrode material of negative electrode A2 and the negative electrode material of negative electrode A3 contain an active material containing zinc, and the average thickness of the negative electrode material of negative electrode A2 is greater than the average thickness of the negative electrode material of negative electrode A3.

[0016] In the electrode group according to the fifth embodiment, the negative electrodes include negative electrode A1 and negative electrode A2 as the first and second negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, negative electrode A1 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A2, negative electrode A2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A1, the negative electrode material of negative electrode A1 and the negative electrode material of negative electrode A2 contain an active material containing zinc, and the average thickness of the negative electrode material of negative electrode A2 is greater than the average thickness of the negative electrode material of negative electrode A1.

[0017] The electrode group according to this embodiment may satisfy the requirements of only one of the first to fifth embodiments, or may satisfy the requirements of multiple of the first to fifth embodiments.

[0018] The electrode group according to this embodiment can provide excellent life performance in a zinc battery. In the evaluation method described in the Examples below, the electrode group according to this embodiment can provide a cycle count of, for example, more than 100 (preferably, 105 or more, 108 or more, 110 or more, 112 or more, 115 or more, etc.), assuming that the cycle count when only a reference negative electrode is used as the negative electrode is 100. The reason for the excellent life performance is not clear, but, based on the findings of the present inventors, it is speculated as follows. However, the reason is not limited to the following.

[0019] In zinc batteries, oxygen gas can be generated at the positive electrode during charging (e.g., overcharging). As oxygen gas migrates within the battery and is absorbed by the negative electrode, the metallic zinc produced at the negative electrode during the charging reaction is oxidized to produce zinc oxide. While oxygen gas can be absorbed by each negative electrode in the battery, there is little space within the electrode group, where the electrodes tend to be densely stacked. Meanwhile, for the negative electrodes A1 to A3, which are the first to third negative electrodes counting from one end of the electrode group in the stacking direction of the negative and positive electrodes, the negative electrodes closer to the end are subjected to a smaller group pressure, and therefore the group pressure of negative electrode A2 is smaller than that of negative electrode A3. In this case, because the group pressure of negative electrode A2 is smaller than that of negative electrode A3, it is easier to ensure a space in negative electrode A2 through which oxygen gas can migrate. Therefore, oxygen gas is more likely to reach and be absorbed by negative electrode A2 than by negative electrode A3. Furthermore, because the group pressure is likely to cause a gas absorption reaction at the outer periphery of the negative electrode, deterioration due to localized reactions is likely to progress in negative electrode A2, which is prone to oxygen gas absorption. As a result, negative electrode A2 is susceptible to deterioration due to gas absorption reactions in addition to deterioration due to charge-discharge reactions, and therefore, with repeated charge-discharge cycles, dendrite growth, shape change, and the like occur, which tends to reduce life performance. Furthermore, since the group pressure of negative electrode A2 is smaller than that of negative electrode A3, zinc elution from negative electrode A2 is greater, and therefore, with repeated charge-discharge cycles, dendrite growth, shape change, and the like tend to reduce life performance.

[0020] In contrast, in the electrode group according to the first embodiment, the mass of the active material in the negative electrode A2 is greater than the mass of the active material in the negative electrode A3. This means that the negative electrode A2, which is prone to deterioration, contains more active material than the negative electrode A3, thereby preventing the negative electrode A2 from deteriorating and reducing its lifespan. In the electrode group according to the second embodiment, the mass of the negative electrode A2 is greater than the mass of the negative electrode A3. This means that mechanical stress is more effectively distributed in the negative electrode A2, which is prone to deterioration, than in the negative electrode A3. This improves physical durability and maintains structural stability during charge / discharge cycles, preventing the negative electrode A2 from deteriorating and reducing its lifespan. In the electrode group according to the third embodiment, the average thickness of the negative electrode A2 is greater than the average thickness of the negative electrode A3. This means that the oxygen gas diffusion path is longer in the negative electrode A2, which is prone to deterioration, than in the negative electrode A3. This prevents excessive charge / discharge reactions from occurring, thereby preventing the negative electrode A2 from deteriorating and reducing its lifespan. In the electrode group according to the fourth embodiment, the average thickness of the negative electrode material of negative electrode A2 is greater than the average thickness of the negative electrode material of negative electrode A3, and therefore the diffusion path of oxygen gas is longer in negative electrode A2, which is prone to deterioration, than in negative electrode A3, and therefore excessive charge / discharge reactions are suppressed, thereby suppressing deterioration of negative electrode A2 and a decrease in life performance.

[0021] In the case of the first and second negative electrodes A1 and A2 counting from one end of the stacking direction of the negative electrodes and positive electrodes in the electrode group, when the negative electrode A1 is located at one end of the stacking direction of the negative electrodes and positive electrodes in the electrode group, the surface of the negative electrode A1 at that end is less likely to contribute to the charge-discharge reaction. Furthermore, when the negative electrode A1 is not located at one end of the stacking direction of the negative electrodes and positive electrodes in the electrode group (when the positive electrode is located at one end of the stacking direction of the negative electrodes and positive electrodes in the electrode group), the surface of the positive electrode located at that end is less likely to contribute to the charge-discharge reaction, resulting in a decrease in the reactivity of the entire positive electrode, and consequently, a decrease in the reactivity of the negative electrode A1. In these cases, excessive charge-discharge reaction occurs in the negative electrode A2 relative to the negative electrode A1, which tends to deteriorate the negative electrode A2. Therefore, repeated charge-discharge cycles tend to cause dendrite growth, shape changes, and other problems, which can reduce the lifespan.

[0022] In contrast, in the electrode group according to the fifth embodiment, the average thickness of the negative electrode material of negative electrode A2 is greater than the average thickness of the negative electrode material of negative electrode A1, and therefore the diffusion path of oxygen gas is longer in negative electrode A2, which is prone to deterioration, than in negative electrode A1. This prevents excessive charge / discharge reactions from occurring, thereby preventing negative electrode A2 from deteriorating and reducing its life performance.

[0023] The electrode group according to this embodiment includes multiple negative electrodes, and the negative electrodes and positive electrodes may be stacked alternately. Each of the multiple negative electrodes may have a negative electrode material containing an active material containing zinc. The negative electrode materials of the multiple negative electrodes may contain the same active material or different active materials. The number of negative electrodes may be 5 or more, 6 or more, 7 or more, or 8 or more, from the viewpoint of easily achieving high capacity. In the electrode group according to the fifth embodiment, the number of negative electrodes may be 3 or more, or 4 or more. The number of negative electrodes may be 25 or less, 20 or less, 18 or less, 15 or less, 14 or less, 12 or less, 11 or less, 10 or less, 9 or less, or 8 or less, from the viewpoint of easily suppressing accelerated deterioration due to differences in electrode group pressure between electrodes located at one end of the electrode group and electrodes located at the center. From these viewpoints, the number of negative electrodes may be 3 to 25, 3 to 15, 3 to 10, 5 to 25, 5 to 15, 5 to 10, 7 to 25, 7 to 15, or 7 to 10. The number of negative electrodes may be more than the number of positive electrodes, may be the same as the number of positive electrodes, or may be less than the number of positive electrodes. The number of negative electrodes may be more than the number of positive electrodes from the viewpoint that deterioration caused by the negative electrodes can be easily suppressed by increasing the capacity ratio of the negative electrodes to the positive electrodes.

[0024] The electrode group according to this embodiment includes a positive electrode, and may include multiple positive electrodes. The positive electrode materials of the multiple positive electrodes may contain the same active material or different active materials. The number of positive electrodes may be 4 or more, 5 or more, 6 or more, or 7 or more, from the viewpoint of easily achieving high capacity. In the electrode group according to the fifth embodiment, the number of positive electrodes may be 2 or more, or 3 or more. The number of positive electrodes may be 24 or less, 19 or less, 17 or less, 14 or less, 13 or less, 11 or less, 10 or less, 9 or less, 8 or less, or 7 or less, from the viewpoint of easily suppressing accelerated deterioration due to differences in electrode group pressure between electrodes located at one end of the electrode group and electrodes located at the center. From these viewpoints, the number of positive electrodes may be 2 to 24, 2 to 14, 2 to 9, 4 to 24, 4 to 14, 4 to 9, 6 to 24, 6 to 14, or 6 to 9.

[0025] The negative electrode can have a current collector and a negative electrode material (e.g., a negative electrode material layer) supported on the current collector, or can have a current collector and a negative electrode material (e.g., a negative electrode material layer) disposed on at least one of one surface and the other surface of the current collector, or can have a current collector and a negative electrode material (e.g., a negative electrode material layer) disposed on one surface of the current collector, and a negative electrode material (e.g., a negative electrode material layer) disposed on the other surface of the current collector. The negative electrode located at at least one of one end and the other end in the stacking direction of the negative electrodes and positive electrodes in the electrode group may have a negative electrode material on one surface and the other surface of the current collector, or may have a negative electrode material on one of the one surface and the other surface of the current collector. For example, the negative electrode located at one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes may have a negative electrode material on one side of the current collector, whichever is closer to the other end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. The negative electrode located at the other end of the electrode group in the stacking direction of the negative electrodes and positive electrodes may have a negative electrode material on one side of the current collector, whichever is closer to the one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. The negative electrode located between two positive electrodes may have a negative electrode material on one side of the current collector, whichever is closer to the one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. If the current collector has an opening (for example, if the current collector is a punched metal), the opening may be filled with a negative electrode material. That is, the negative electrode may have a negative electrode material (e.g., a negative electrode material layer) arranged on at least one side of the current collector and a negative electrode material filled in the current collector.

[0026] The electrode group according to this embodiment includes negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side of the electrode group in the stacking direction of the negative electrodes and positive electrodes (hereinafter sometimes referred to as "one end side of the electrode group"), and negative electrodes B1 to B3 as the first to third negative electrodes counting from the other end side of the electrode group in the stacking direction of the negative electrodes and positive electrodes (hereinafter sometimes referred to as "the other end side of the electrode group"). Negative electrode A1 is disposed between a current collector and the surface of the current collector on the one end side of the electrode group. a negative electrode A2 has a current collector, a negative electrode material (e.g., a negative electrode material layer) a11 arranged on the surface of the current collector facing the negative electrode A2 (the surface of the current collector on the other end side of the electrode group); a negative electrode A2 has a current collector, a negative electrode material (e.g., a negative electrode material layer) a21 arranged on the surface of the current collector facing the negative electrode A1, and a negative electrode material (e.g., a negative electrode material layer) a22 arranged on the surface of the current collector facing the negative electrode A3 (the surface of the current collector on the other end side of the electrode group); a negative electrode A3 has a current collector, a negative electrode material (e.g., a negative electrode material layer) a21 arranged on the surface of the current collector facing the negative electrode A1, and a negative electrode material (e.g., a negative electrode material layer) a22 arranged on the surface of the current collector facing the negative electrode A3 (the surface of the current collector on the other end side of the electrode group). a negative electrode B1 has a current collector, a negative electrode material (e.g., a negative electrode material layer) a31 arranged on the surface of the current collector facing the negative electrode A2, and a negative electrode material (e.g., a negative electrode material layer) a32 arranged on the surface of the current collector on the other end side of the electrode group; a negative electrode B1 has a current collector, a negative electrode material (e.g., a negative electrode material layer) b11 arranged on the surface of the current collector on the other end side of the electrode group, and a negative electrode material (e.g., a negative electrode material layer) b12 arranged on the surface of the current collector facing the negative electrode B2 (the surface of the current collector on one end side of the electrode group); a negative electrode material (e.g., a negative electrode material layer) b21 arranged on the surface of the current collector facing the negative electrode B1, and a negative electrode material (e.g., a negative electrode material layer) b22 arranged on the surface of the current collector facing the negative electrode B3 (the surface of the current collector on one end side of the electrode group), and the negative electrode B3 may have a current collector, a negative electrode material (e.g., a negative electrode material layer) b31 arranged on the surface of the current collector facing the negative electrode B2, and a negative electrode material (e.g., a negative electrode material layer) b32 arranged on the surface of the current collector on one end side of the electrode group.

[0027] Fig. 1 is a schematic cross-sectional view showing an example of a zinc battery according to this embodiment. The zinc battery 1 of Fig. 1 includes an electrode group 10. The electrode group 10 includes a plurality of negative electrodes 12 and a plurality of positive electrodes 14 that are alternately stacked. In Fig. 1, components other than the negative electrodes 12 and the positive electrodes 14 (separators, etc.) are not shown.

[0028] The electrode group 10 includes negative electrodes A1 to A4 as the first to fourth negative electrodes 12 counting from one end side (the left end side in FIG. 1 ) in the stacking direction (the left-right direction in FIG. 1 ) of the negative electrodes 12 and the positive electrodes 14 in the electrode group 10, and includes negative electrodes B1 to B4 as the first to fourth negative electrodes 12 counting from the other end side (the right end side in FIG. 1 ) in the stacking direction (the left-right direction in FIG. 1 ) of the negative electrodes 12 and the positive electrodes 14 in the electrode group 10. Negative electrode A1 is located at one end (the left end side in FIG. 1 ) in the stacking direction of the negative electrodes 12 and the positive electrodes 14, and negative electrode B1 is located at the other end (the right end side in FIG. 1 ) in the stacking direction of the negative electrodes 12 and the positive electrodes 14.

[0029] Negative electrode A1 has a current collector C, a negative electrode material a11 arranged on a surface of the current collector C on one end side of the electrode group 10 (left side in FIG. 1 ), and a negative electrode material a12 arranged on a surface of the current collector C on the negative electrode A2 side. Negative electrode A2 has a current collector C, a negative electrode material a21 arranged on a surface of the current collector C on the negative electrode A1 side, and a negative electrode material a22 arranged on a surface of the current collector C on the negative electrode A3 side. Negative electrode A3 has a current collector C, a negative electrode material a31 arranged on a surface of the current collector C on the negative electrode A2 side, and a negative electrode material a32 arranged on a surface of the current collector C on the negative electrode A4 side (the surface on the other end side (right side in FIG. 1 ) of the electrode group 10). Negative electrode B1 has a current collector C, a negative electrode material b11 arranged on the surface of current collector C on the other end side of the electrode group 10 (right side in FIG. 1 ), and a negative electrode material b12 arranged on the surface of current collector C on the negative electrode B2 side. Negative electrode B2 has a current collector C, a negative electrode material b21 arranged on the surface of current collector C on the negative electrode B1 side, and a negative electrode material b22 arranged on the surface of current collector C on the negative electrode B3 side. Negative electrode B3 has a current collector C, a negative electrode material b31 arranged on the surface of current collector C on the negative electrode B2 side, and a negative electrode material b32 arranged on the surface of current collector C on the negative electrode B4 side (the surface on one end side of electrode group 10 (left side in FIG. 1 )).

[0030] In the electrode groups according to the first to fourth embodiments, the negative electrodes include negative electrodes A1 to A3 (negative electrode A1, negative electrode A2, and negative electrode A3) as the first to third negative electrodes counting from one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. From the viewpoint of easily obtaining a high energy density, negative electrode A1 may be located at one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. Alternatively, a positive electrode may be located at one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes, and negative electrode A1 may be adjacent to the positive electrode located at that end without being located at that end in the stacking direction of the negative electrodes and positive electrodes.

[0031] In the electrode groups according to the first to fourth embodiments, the negative electrodes may include negative electrodes B1 to B3 (negative electrode B1, negative electrode B2, and negative electrode B3) as the first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. When the number of negative electrodes is five, negative electrode A3 and negative electrode B3 are the same negative electrode. From the viewpoint of easily obtaining a high energy density, negative electrode B1 may be located at the other end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. Alternatively, a positive electrode may be located at the other end of the electrode group in the stacking direction of the negative electrodes and positive electrodes, and negative electrode B1 may be adjacent to the positive electrode located at the other end without being located at the other end of the stacking direction of the negative electrodes and positive electrodes.

[0032] In the electrode group according to the first embodiment, from the viewpoint of obtaining excellent life performance, negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode A2 is greater than the mass of the active material in negative electrode A3. In the electrode group according to the first embodiment, from the viewpoint of easily obtaining excellent life performance, negative electrodes B1 to B3 may have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode B2 may be greater than the mass of the active material in negative electrode B3.

[0033] In the electrode group according to the second embodiment, from the viewpoint of obtaining excellent life performance, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the negative electrode A2 is greater than the mass of the negative electrode A3. In the electrode group according to the second embodiment, from the viewpoint of easily obtaining excellent life performance, the negative electrodes B1 to B3 may have a negative electrode material containing an active material containing zinc, and the mass of the negative electrode B2 may be greater than the mass of the negative electrode B3.

[0034] In the electrode group according to the third embodiment, from the viewpoint of obtaining excellent life performance, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the average thickness of the negative electrode A2 is greater than the average thickness of the negative electrode A3. In the electrode group according to the third embodiment, from the viewpoint of easily obtaining excellent life performance, the negative electrodes B1 to B3 may have a negative electrode material containing an active material containing zinc, and the average thickness of the negative electrode B2 may be greater than the average thickness of the negative electrode B3.

[0035] In the electrode group according to the fourth embodiment, from the viewpoint of obtaining excellent life performance, the negative electrode A2 has a current collector and a negative electrode material (e.g., a negative electrode material layer) a22 arranged on the surface of the current collector facing the negative electrode A3, the negative electrode A3 has a current collector and a negative electrode material (e.g., a negative electrode material layer) a31 arranged on the surface of the current collector facing the negative electrode A2, the negative electrode material a22 of the negative electrode A2 and the negative electrode material a31 of the negative electrode A3 contain an active material containing zinc, and the average thickness of the negative electrode material a22 of the negative electrode A2 is greater than the average thickness of the negative electrode material a31 of the negative electrode A3. From the viewpoint of easily obtaining excellent life performance, the electrode group according to the fourth embodiment may be configured such that the negative electrode B2 has a current collector and a negative electrode material (e.g., a negative electrode material layer) b22 arranged on the surface of the current collector facing the negative electrode B3, the negative electrode B3 has a current collector and a negative electrode material (e.g., a negative electrode material layer) b31 arranged on the surface of the current collector facing the negative electrode B2, the negative electrode material b22 of the negative electrode B2 and the negative electrode material b31 of the negative electrode B3 contain an active material containing zinc, and the average thickness of the negative electrode material b22 of the negative electrode B2 is greater than the average thickness of the negative electrode material b31 of the negative electrode B3.

[0036] In the electrode group according to the fifth embodiment, the negative electrodes include negative electrode A1 and negative electrode A2 as the first and second negative electrodes counting from one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes. Negative electrode A1 may be located at one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes, from the viewpoint of easily obtaining a high energy density. Alternatively, a positive electrode may be located at one end of the electrode group in the stacking direction of the negative electrodes and positive electrodes, and negative electrode A1 may be adjacent to the positive electrode located at that end without being located at the end of the stacking direction of the negative electrodes and positive electrodes.

[0037] In the electrode group according to the fifth embodiment, the negative electrodes may include negative electrode B1 and negative electrode B2 as the first and second negative electrodes counting from the other end of the stacking direction of the negative electrodes and positive electrodes in the electrode group. When the number of negative electrodes is three, negative electrode A2 and negative electrode B2 are the same negative electrode. From the viewpoint of easily obtaining a high energy density, negative electrode B1 may be located at the other end of the stacking direction of the negative electrodes and positive electrodes in the electrode group. Alternatively, a positive electrode may be located at the other end of the stacking direction of the negative electrodes and positive electrodes in the electrode group, and negative electrode B1 may be adjacent to the positive electrode located at the other end without being located at the other end of the stacking direction of the negative electrodes and positive electrodes.

[0038] In the electrode group according to the fifth embodiment, from the viewpoint of obtaining excellent life performance, the negative electrode A1 has a current collector and a negative electrode material (e.g., a negative electrode material layer) a12 arranged on the surface of the current collector facing the negative electrode A2, the negative electrode A2 has a current collector and a negative electrode material (e.g., a negative electrode material layer) a21 arranged on the surface of the current collector facing the negative electrode A1, the negative electrode material a12 of the negative electrode A1 and the negative electrode material a21 of the negative electrode A2 contain an active material containing zinc, and the average thickness of the negative electrode material a21 of the negative electrode A2 is greater than the average thickness of the negative electrode material a12 of the negative electrode A1. From the viewpoint of easily obtaining excellent life performance, the electrode group according to the fifth embodiment may be configured such that the negative electrode B1 has a current collector and a negative electrode material (e.g., a negative electrode material layer) b12 arranged on the surface of the current collector facing the negative electrode B2, the negative electrode B2 has a current collector and a negative electrode material (e.g., a negative electrode material layer) b21 arranged on the surface of the current collector facing the negative electrode B1, the negative electrode material b12 of the negative electrode B1 and the negative electrode material b21 of the negative electrode B2 contain an active material containing zinc, and the average thickness of the negative electrode material b21 of the negative electrode B2 is greater than the average thickness of the negative electrode material b12 of the negative electrode B1.

[0039] In the first to fourth embodiments, the mass ratio R1 of the active material of negative electrode A3 to the active material of negative electrode A2 (A3 / A2), the mass ratio of the active material of negative electrode B3 to the active material of negative electrode B2 (B3 / B2), the mass ratio of the active material of negative electrode A3 to the active material of negative electrode A1 (A3 / A1), or the mass ratio of the active material of negative electrode B3 to the active material of negative electrode B1 (B3 / B1) may be in the following ranges depending on the configuration of each embodiment. From the viewpoint of easily obtaining excellent life performance, the mass ratio R1 may be 1.00 or less, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.90 or less, 0.89 or less, or 0.88 or less, or may be 0.87 or less, 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.78 or less, 0.77 or less, or 0.76 or less. From the viewpoint of easily obtaining excellent life performance, the mass ratio R1 may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, or 0.88 or more, or may be 0.89 or more, 0.90 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, 0.97 or more, or 0.98 or more. From these viewpoints, the mass ratio R1 is 0.50 to 1.00, 0.50 or more and less than 1.00, 0.50 to 0.95, 0.50 to 0.90, 0.50 to 0.85, 0.75 to 1.00, 0.75 or more and less than 1.00, 0.75 to 0.95, 0.75 to 0.90, 0.75 to 0.85, 0.85 to 1.00, 0.85 or more and less than 1.00, 0.85 to 0.95, 0.85 to 0.90, 0.90 to 1.00, 0.90 or more and less than 1.00, 0.90 to 0.95, 0.95 to 1.00, or 0.95 or more and less than 1.00.

[0040] In a fifth embodiment, the mass of the active material in at least one selected from the group consisting of negative electrode A1 and negative electrode A2 may be equal to, smaller than, or greater than the mass of the active material in negative electrode A3. In the fifth embodiment, the mass of the active material in negative electrode A1 may be smaller than the mass of the active material in negative electrode A3, from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the mass of the active material in at least one selected from the group consisting of negative electrode B1 and negative electrode B2 may be equal to, smaller than, or greater than the mass of the active material in negative electrode B3. In the fifth embodiment, the mass of the active material in negative electrode B1 may be smaller than the mass of the active material in negative electrode B3, from the viewpoint of easily obtaining excellent life performance.

[0041] In the first to fourth embodiments, the mass of the active material in negative electrode A2 may be equal to the mass of the active material in negative electrode A1, may be smaller than the mass of the active material in negative electrode A1, or may be larger than the mass of the active material in negative electrode A1. In the first to fourth embodiments, the mass of the active material in negative electrode A2 may be equal to or larger than the mass of the active material in negative electrode A1, from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the mass of the active material in negative electrode A2 may be equal to or larger than the mass of the active material in negative electrode A1, from the viewpoint of easily obtaining excellent life performance.

[0042] The mass of the active material in the negative electrode means the total mass of the active material contained in the negative electrode. The mass of the active material in the negative electrode can be calculated, for example, by measuring the mass of the negative electrode material peeled and recovered from the negative electrode and multiplying the mass of the negative electrode material by the ratio of zinc obtained by qualitative analysis using ICP optical emission spectrometry (for example, Agilent Technologies, product name: Agilent 5100).

[0043] In the first to fourth embodiments, the mass ratio R2 of the negative electrode A3 to the negative electrode A2 (A3 / A2), the mass ratio of the negative electrode B3 to the negative electrode B2 (B3 / B2), the mass ratio of the negative electrode A3 to the negative electrode A1 (A3 / A1), or the mass ratio of the negative electrode B3 to the negative electrode B1 (B3 / B1) may be in the following ranges depending on the configuration of each embodiment. From the viewpoint of easily obtaining excellent life performance, the mass ratio R2 may be 1.00 or less, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.90 or less, 0.89 or less, or 0.88 or less, or may be 0.87 or less, 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.78 or less, 0.77 or less, or 0.76 or less. From the viewpoint of easily obtaining excellent life performance, the mass ratio R2 may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, or 0.88 or more, or may be 0.89 or more, 0.90 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, 0.97 or more, or 0.98 or more. From these viewpoints, the mass ratio R2 is 0.50 to 1.00, 0.50 or more and less than 1.00, 0.50 to 0.95, 0.50 to 0.90, 0.50 to 0.85, 0.75 to 1.00, 0.75 or more and less than 1.00, 0.75 to 0.95, 0.75 to 0.90, 0.75 to 0.85, 0.85 to 1.00, 0.85 or more and less than 1.00, 0.85 to 0.95, 0.85 to 0.90, 0.90 to 1.00, 0.90 or more and less than 1.00, 0.90 to 0.95, 0.95 to 1.00, or 0.95 or more and less than 1.00.

[0044] In the fifth embodiment, the mass of at least one selected from the group consisting of negative electrode A1 and negative electrode A2 may be equal to, smaller than, or larger than the mass of negative electrode A3. In the fifth embodiment, the mass of negative electrode A1 may be smaller than the mass of negative electrode A3 from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the mass of at least one selected from the group consisting of negative electrode B1 and negative electrode B2 may be equal to, smaller than, or larger than the mass of negative electrode B3. In the fifth embodiment, the mass of negative electrode B1 may be smaller than the mass of negative electrode B3 from the viewpoint of easily obtaining excellent life performance.

[0045] In the first to fourth embodiments, the mass of negative electrode A2 may be equal to, smaller than, or larger than the mass of negative electrode A1. In the first to fourth embodiments, the mass of negative electrode A2 may be equal to, smaller than, or larger than the mass of negative electrode A1, from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the mass of negative electrode A2 may be equal to, or larger than the mass of negative electrode A1, from the viewpoint of easily obtaining excellent life performance.

[0046] The mass of the negative electrode means the total mass of the components constituting the negative electrode (negative electrode material and current collector), and does not include the strap.

[0047] Ratio R3 may be in the following ranges depending on the configuration of each embodiment, as the ratio of the average thickness of negative electrode A3 to the average thickness of negative electrode A2 (A3 / A2), the ratio of the average thickness of negative electrode B3 to the average thickness of negative electrode B2 (B3 / B2), the ratio of the average thickness of negative electrode A3 to the average thickness of negative electrode A1 (A3 / A1), or the ratio of the average thickness of negative electrode B3 to the average thickness of negative electrode B1 (B3 / B1). From the viewpoint of easily obtaining excellent life performance, the ratio R3 may be 1.00 or less, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.90 or less, 0.89 or less, or 0.88 or less, or may be 0.87 or less, 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.78 or less, 0.77 or less, or 0.76 or less. From the viewpoint of easily obtaining excellent life performance, the ratio R3 may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, or 0.88 or more, or may be 0.89 or more, 0.90 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, 0.97 or more, or 0.98 or more. From these viewpoints, the ratio R3 may be 0.50 to 1.00, 0.50 or more and less than 1.00, 0.50 to 0.95, 0.50 to 0.90, 0.50 to 0.85, 0.75 to 1.00, 0.75 or more and less than 1.00, 0.75 to 0.95, 0.75 to 0.90, 0.75 to 0.85, 0.85 to 1.00, 0.85 or more and less than 1.00, 0.85 to 0.95, 0.85 to 0.90, 0.90 to 1.00, 0.90 or more and less than 1.00, 0.90 to 0.95, 0.95 to 1.00, or 0.95 or more and less than 1.00.

[0048] In the fifth embodiment, the average thickness of at least one selected from the group consisting of negative electrode A1 and negative electrode A2 may be equal to, smaller than, or greater than the average thickness of negative electrode A3. In the fifth embodiment, the average thickness of negative electrode A1 may be smaller than the average thickness of negative electrode A3 from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the average thickness of at least one selected from the group consisting of negative electrode B1 and negative electrode B2 may be equal to, smaller than, or greater than the average thickness of negative electrode B3. In the fifth embodiment, the average thickness of negative electrode B1 may be smaller than the average thickness of negative electrode B3 from the viewpoint of easily obtaining excellent life performance.

[0049] In the first to fourth embodiments, the average thickness of negative electrode A2 may be equal to, smaller than, or larger than the average thickness of negative electrode A1. In the first to fourth embodiments, the average thickness of negative electrode A2 may be equal to or larger than the average thickness of negative electrode A1, from the viewpoint of easily obtaining excellent life performance. In the fifth embodiment, the average thickness of negative electrode A2 may be equal to or larger than the average thickness of negative electrode A1, from the viewpoint of easily obtaining excellent life performance.

[0050] The average thickness of the negative electrode is the average value of the thicknesses of the negative electrode and the positive electrode in the stacking direction in the electrode group.

[0051] The ratio R4, which is the ratio of the average thickness of the negative electrode material a31 to the average thickness of the negative electrode material a22 (a31 / a22) or the ratio of the average thickness of the negative electrode material b31 to the average thickness of the negative electrode material b22 (b31 / b22), may be in the following range depending on the configuration of each embodiment. From the viewpoint of easily obtaining excellent life performance, the ratio R4 may be 1.00 or less, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.90 or less, 0.89 or less, 0.88 or less, or 0.87 or less, or may be 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.78 or less, 0.77 or less, 0.76 or less, 0.75 or less, 0.73 or less, or 0.71 or less. From the viewpoint of easily obtaining excellent life performance, the ratio R4 may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.71 or more, 0.73 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, or 0.87 or more, or may be 0.88 or more, 0.89 or more, 0.90 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, or 0.97 or more. From these viewpoints, the ratio R4 may be 0.50 to 1.00, 0.50 or more and less than 1.00, 0.50 to 0.95, 0.50 to 0.90, 0.50 to 0.85, 0.75 to 1.00, 0.75 or more and less than 1.00, 0.75 to 0.95, 0.75 to 0.90, 0.75 to 0.85, 0.85 to 1.00, 0.85 or more and less than 1.00, 0.85 to 0.95, 0.85 to 0.90, 0.90 to 1.00, 0.90 or more and less than 1.00, 0.90 to 0.95, 0.95 to 1.00, or 0.95 or more and less than 1.00.

[0052] As the ratio of the average thickness of the negative electrode material a12 to the average thickness of the negative electrode material a21 (a12 / a21), or the ratio of the average thickness of the negative electrode material b12 to the average thickness of the negative electrode material b21 (b12 / b21), the ratio R5 may be in the following range depending on the configuration of each embodiment. From the viewpoint of easily obtaining excellent life performance, the ratio R5 may be 1.00 or less, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.90 or less, 0.89 or less, 0.88 or less, or 0.87 or less, or may be 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.78 or less, 0.77 or less, 0.76 or less, 0.75 or less, 0.73 or less, or 0.71 or less. From the viewpoint of easily obtaining excellent life performance, the ratio R5 may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.71 or more, 0.73 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, or 0.87 or more, or may be 0.88 or more, 0.89 or more, 0.90 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, or 0.97 or more. From these viewpoints, the ratio R5 may be 0.50 to 1.00, 0.50 or more and less than 1.00, 0.50 to 0.95, 0.50 to 0.90, 0.50 to 0.85, 0.75 to 1.00, 0.75 or more and less than 1.00, 0.75 to 0.95, 0.75 to 0.90, 0.75 to 0.85, 0.85 to 1.00, 0.85 or more and less than 1.00, 0.85 to 0.95, 0.85 to 0.90, 0.90 to 1.00, 0.90 or more and less than 1.00, 0.90 to 0.95, 0.95 to 1.00, or 0.95 or more and less than 1.00.

[0053] The average thickness of the negative electrode material is the average value of the thickness of the negative and positive electrodes in the electrode group in the stacking direction. When the current collector has an opening (for example, when the current collector is a punched metal), the distance between the opening surface (the end surface of the opening facing the negative electrode material) and the surface of the negative electrode material opposite the current collector can be used as the thickness of the negative electrode material.

[0054] From the viewpoint of easily obtaining excellent life performance, the mass of at least one selected from the group consisting of negative electrode A1, negative electrode A2, and negative electrode A3 may be in the following range: The mass of at least one selected from the group consisting of negative electrode B1, negative electrode B2, and negative electrode B3 may be in the following range: The mass of the negative electrode may be 0.10 g or more, 0.50 g or more, 1.00 g or more, 1.50 g or more, 2.00 g or more, 2.50 g or more, or 3.00 g or more. The mass of the negative electrode may be 20.00 g or less, 15.00 g or less, 12.00 g or less, 10.00 g or less, 9.50 g or less, 9.00 g or less, 8.50 g or less, 8.00 g or less, 7.50 g or less, 7.00 g or less, 6.50 g or less, 6.00 g or less, 5.50 g or less, 5.00 g or less, 4.50 g or less, 4.00 g or less, or 3.50 g or less. From these viewpoints, the mass of the negative electrode may be 0.10 to 20.00 g, 0.10 to 12.00 g, 0.10 to 5.00 g, 1.00 to 20.00 g, 1.00 to 12.00 g, 1.00 to 5.00 g, 2.00 to 20.00 g, 2.00 to 12.00 g, or 2.00 to 5.00 g.

[0055] The mass per unit area of ​​at least one electrode selected from the group consisting of negative electrode A1, negative electrode A2, and negative electrode A3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The mass per unit area of ​​at least one electrode selected from the group consisting of negative electrode B1, negative electrode B2, and negative electrode B3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The mass per unit area of ​​the negative electrode is 0.010 g / cm ２ Above, 0.030g / cm ２ Above, 0.050g / cm ２ Above, 0.080g / cm ２ Above, 0.100g / cm ２ Above, 0.120g / cm ２ or more, or 0.150 g / cm ２ The mass per unit area of ​​the negative electrode may be 1.000 g / cm or more. ２ Below, 0.800g / cm ２ Below, 0.600g / cm ２ Below, 0.500g / cm ２Below, 0.450g / cm ２ Below, 0.400g / cm ２ Below, 0.350g / cm ２ Below, 0.300g / cm ２ Below, 0.250g / cm ２ or less, or 0.200 g / cm ２ From these viewpoints, the mass per unit area of ​​the negative electrode may be 0.010 to 1.000 g / cm ２ ,0.010~0.500g / cm ２ ,0.010~0.300g / cm ２ ,0.050~1.000g / cm ２ ,0.050~0.500g / cm ２ ,0.050~0.300g / cm ２ ,0.100~1.000g / cm ２ ,0.100~0.500g / cm ２ , or 0.100 to 0.300 g / cm ２ It may be.

[0056] The mass of the negative electrode active material in at least one selected from the group consisting of negative electrodes A1, A2, and A3 may be in the following ranges from the viewpoint of easily obtaining excellent life performance. The mass of the negative electrode active material in at least one selected from the group consisting of negative electrodes B1, B2, and B3 may be in the following ranges from the viewpoint of easily obtaining excellent life performance. The mass of the negative electrode active material may be 0.10 g or more, 0.50 g or more, 1.00 g or more, 1.50 g or more, or 2.00 g or more. The mass of the negative electrode active material may be 20.00 g or less, 15.00 g or less, 12.00 g or less, 10.00 g or less, 8.00 g or less, 7.00 g or less, 6.00 g or less, 5.50 g or less, 5.00 g or less, 4.50 g or less, 4.00 g or less, 3.50 g or less, 3.00 g or less, or 2.50 g or less. From these viewpoints, the mass of the negative electrode active material may be 0.10 to 20.00 g, 0.10 to 10.00 g, 0.10 to 5.00 g, 0.50 to 20.00 g, 0.50 to 10.00 g, 0.50 to 5.00 g, 1.00 to 20.00 g, 1.00 to 10.00 g, or 1.00 to 5.00 g.

[0057] The mass per unit area of ​​the negative electrode active material in at least one selected from the group consisting of negative electrodes A1, A2, and A3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The mass per unit area of ​​the negative electrode active material in at least one selected from the group consisting of negative electrodes B1, B2, and B3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The mass per unit area of ​​the negative electrode active material is 0.001 g / cm ２ Above, 0.005g / cm ２ Above, 0.010g / cm ２ Above, 0.030g / cm ２ Above, 0.050g / cm ２ Above, 0.080g / cm ２ or more, or 0.100 g / cm ２ The mass per unit area of ​​the negative electrode active material may be 1.000 g / cm or more. ２ Below, 0.800g / cm ２ Below, 0.600g / cm ２ Below, 0.500g / cm ２ Below, 0.450g / cm ２ Below, 0.400g / cm ２ Below, 0.350g / cm ２ Below, 0.300g / cm ２ Below, 0.250g / cm ２ Below, 0.200g / cm ２ or less, or 0.150 g / cm ２ From these viewpoints, the mass per unit area of ​​the negative electrode active material may be 0.001 to 1.000 g / cm ２ ,0.001~0.500g / cm ２ ,0.001~0.300g / cm ２ ,0.010~1.000g / cm ２ ,0.010~0.500g / cm ２ ,0.010~0.300g / cm ２ ,0.050~1.000g / cm ２ ,0.050~0.500g / cm ２ , or 0.050 to 0.300 g / cm ２ It may be.

[0058] The mass ratio of the negative electrode active material in at least one selected from the group consisting of negative electrodes A1, A2, and A3 to the negative electrode current collector (negative electrode active material / current collector) may be within the following range, from the viewpoint of easily obtaining excellent life performance. The mass ratio of the negative electrode active material in at least one selected from the group consisting of negative electrodes B1, B2, and B3 to the negative electrode current collector (negative electrode active material / current collector) may be within the following range, from the viewpoint of easily obtaining excellent life performance. The mass ratio may be 0.01 or more, 0.05 or more, 0.10 or more, 0.50 or more, 1.00 or more, more than 1.00, 1.20 or more, 1.50 or more, 1.80 or more, 2.00 or more, or 2.20 or more. The mass ratio may be 10.00 or less, 8.00 or less, 6.00 or less, 5.00 or less, 4.50 or less, 4.00 or less, 3.50 or less, 3.00 or less, or 2.50 or less. From these viewpoints, the mass ratio may be 0.01 to 10.00, 0.01 to 5.00, 0.01 to 3.00, 0.10 to 10.00, 0.10 to 5.00, 0.10 to 3.00, 1.00 to 10.00, 1.00 to 5.00, or 1.00 to 3.00.

[0059] The average thickness of at least one electrode selected from the group consisting of negative electrode A1, negative electrode A2, and negative electrode A3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The average thickness of at least one electrode selected from the group consisting of negative electrode B1, negative electrode B2, and negative electrode B3 may be in the following range from the viewpoint of easily obtaining excellent life performance. The average thickness of the negative electrode may be 0.010 mm or more, 0.050 mm or more, 0.100 mm or more, 0.150 mm or more, 0.200 mm or more, 0.250 mm or more, 0.300 mm or more, 0.350 mm or more, or 0.400 mm or more. The average thickness of the negative electrode may be 5.000 mm or less, 4.000 mm or less, 3.000 mm or less, 2.000 mm or less, 1.000 mm or less, 0.800 mm or less, 0.600 mm or less, 0.550 mm or less, 0.500 mm or less, or 0.450 mm or less. From these viewpoints, the average thickness of the negative electrode may be 0.010 to 5.000 mm, 0.010 to 1.000 mm, 0.010 to 0.600 mm, 0.050 to 5.000 mm, 0.050 to 1.000 mm, 0.050 to 0.600 mm, 0.100 to 5.000 mm, 0.100 to 1.000 mm, or 0.100 to 0.600 mm.

[0060] The average thickness of at least one material selected from the group consisting of negative electrode material a11, negative electrode material a12, negative electrode material a21, negative electrode material a22, negative electrode material a31, and negative electrode material a32 may be in the following range, from the viewpoint of easily obtaining excellent life performance. The average thickness of at least one material selected from the group consisting of negative electrode material b11, negative electrode material b12, negative electrode material b21, negative electrode material b22, negative electrode material b31, and negative electrode material b32 may be in the following range, from the viewpoint of easily obtaining excellent life performance. The average thickness of the negative electrode material may be 0.010 mm or more, 0.030 mm or more, 0.050 mm or more, 0.080 mm or more, 0.100 mm or more, 0.120 mm or more, 0.130 mm or more, 0.140 mm or more, or 0.150 mm or more. The average thickness of the negative electrode material may be 3.000 mm or less, 2.000 mm or less, 1.000 mm or less, 0.800 mm or less, 0.600 mm or less, 0.500 mm or less, 0.400 mm or less, 0.350 mm or less, 0.300 mm or less, 0.250 mm or less, or 0.200 mm or less. From these viewpoints, the average thickness of the negative electrode material may be 0.010 to 3.000 mm, 0.010 to 1.000 mm, 0.010 to 0.500 mm, 0.050 to 3.000 mm, 0.050 to 1.000 mm, 0.050 to 0.500 mm, 0.100 to 3.000 mm, 0.100 to 1.000 mm, or 0.100 to 0.500 mm.

[0061] The ratio of the average thickness of at least one material selected from the group consisting of negative electrode material a12, negative electrode material a21, negative electrode material a22, negative electrode material a31, and negative electrode material a32 to the average thickness of the negative electrode current collector (negative electrode material / current collector) may be within the following range, from the viewpoint of easily obtaining excellent life performance. The ratio of the average thickness of at least one material selected from the group consisting of negative electrode material b11, negative electrode material b12, negative electrode material b21, negative electrode material b22, negative electrode material b31, and negative electrode material b32 to the average thickness of the negative electrode current collector (negative electrode material / current collector) may be within the following range, from the viewpoint of easily obtaining excellent life performance. The average thickness ratio may be 0.01 or more, 0.05 or more, 0.10 or more, 0.30 or more, 0.50 or more, 0.80 or more, 1.00 or more, more than 1.00, 1.20 or more, 1.30 or more, 1.40 or more, or 1.50 or more. The average thickness ratio may be 10.00 or less, 8.00 or less, 6.00 or less, 5.00 or less, 4.50 or less, 4.00 or less, 3.50 or less, 3.00 or less, 2.50 or less, 2.00 or less, 1.80 or less, or 1.60 or less. From these perspectives, the average thickness ratio may be 0.01 to 10.00, 0.01 to 5.00, 0.01 to 3.00, 0.10 to 10.00, 0.10 to 5.00, 0.10 to 3.00, 1.00 to 10.00, 1.00 to 5.00, or 1.00 to 3.00.

[0062] The negative electrode current collector forms a conductive path for current from the negative electrode material. Examples of the current collector's shape include a flat plate and a sheet. The current collector may be a three-dimensional mesh structure composed of foam metal, expanded metal, punched metal, or a metal fiber felt. The current collector may be composed of a conductive and alkali-resistant material. Examples of such materials include materials that are stable even at the reaction potential of the negative electrode (e.g., materials with a redox potential higher than the reaction potential of the negative electrode, or materials that form a protective coating such as an oxide film on the substrate surface in an alkaline aqueous solution to stabilize the substrate). Furthermore, at the negative electrode, a side reaction occurs in which the electrolyte decomposes, generating hydrogen gas. Materials with a high hydrogen overvoltage tend to suppress the progression of such side reactions. Examples of materials that can be used for the current collector include zinc, lead, tin, copper, brass, steel, and nickel. The current collector may be a substrate (e.g., copper, brass, steel, or nickel) with at least a portion of its surface coated with a metal material (e.g., zinc, lead, tin, or the like).

[0063] The negative electrode material contains an active material containing zinc (hereinafter referred to as "negative electrode active material"). Examples of negative electrode active materials include metallic zinc, zinc oxide, and zinc hydroxide. The negative electrode active material may contain one of these components alone or a plurality of components. The negative electrode material may contain metallic zinc in a fully charged state, and may contain zinc oxide and zinc hydroxide in an end-of-discharge state. That is, the negative electrode material may contain at least one selected from the group consisting of metallic zinc particles, zinc oxide particles, and zinc hydroxide particles.

[0064] From the viewpoint of easily obtaining excellent life performance, the content of the negative electrode active material may be within the following ranges based on the total mass of the negative electrode materials contained in the negative electrode or the total mass of each negative electrode material (negative electrode materials a11, a12, a21, a22, a31, a32, b11, b12, b21, b22, b31, b32, etc.) arranged on at least one of one surface and the other surface of the current collector. The content of the negative electrode active material may be 50% by mass or more, more than 50% by mass, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 82% by mass or more, 85% by mass or more, 88% by mass or more, or 90% by mass or more. The content of the negative electrode active material may be 100% by mass or less, less than 100% by mass, 99% by mass or less, 98% by mass or less, 95% by mass or less, 93% by mass or less, or 92% by mass or less. From these viewpoints, the content of the negative electrode active material may be 50 to 100% by mass, 50% by mass or more and less than 100% by mass, 50 to 98% by mass, 50 to 95% by mass, 80 to 100% by mass, 80% by mass or more and less than 100% by mass, 80 to 98% by mass, 80 to 95% by mass, 90 to 100% by mass, 90% by mass or more and less than 100% by mass, 90 to 98% by mass, or 90 to 95% by mass.

[0065] The negative electrode material may contain additives other than the negative electrode active material. Examples of additives include binders and conductive agents. The binder may contain a water-soluble compound, or may contain a compound that does not fall under the category of water-soluble compounds. A water-soluble compound is defined as a compound that dissolves in an amount of 0.1 g or more in 100 g of water (25°C). Examples of water-soluble compounds include polyvinyl polymers, poly(meth)acrylic polymers, polysaccharides, etc. Examples of compounds that do not fall under the category of water-soluble compounds include fluorine-based polymers (e.g., polytetrafluoroethylene (PTFE)), polyethylene, polypropylene, etc.

[0066] Examples of polyvinyl polymers include polyvinyl alcohol and polyvinylpyrrolidone. Examples of poly(meth)acrylic polymers include poly(meth)acrylic acid and salts of poly(meth)acrylic acid (e.g., alkali metal salts such as sodium salts). Examples of polysaccharides include cellulose polymers such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and salts thereof (e.g., alkali metal salts); alginic acid; alginates such as sodium alginate; starch; starch derivatives; and the like.

[0067] From the viewpoint of easily obtaining excellent discharge output performance, the binder may contain a polyvinyl polymer, may contain a polyvinyl polymer and a fluorine-based polymer, may contain polyvinyl alcohol, or may contain polyvinyl alcohol and PTFE.

[0068] The saponification degree of polyvinyl alcohol may be in the following ranges from the viewpoint of easily obtaining excellent life performance. The saponification degree may be 60.0 mol% or more, 65.0 mol% or more, 70.0 mol% or more, 75.0 mol% or more, 80.0 mol% or more, 85.0 mol% or more, 90.0 mol% or more, 95.0 mol% or more, 98.0 mol% or more, or 99.0 mol% or more. The saponification degree may be less than 100 mol%, 99.9 mol% or less, 99.5 mol% or less, or 99.0 mol% or less. From these viewpoints, the saponification degree may be 60.0 mol% or more but less than 100 mol%, 60.0 to 99.9 mol%, 60.0 to 99.5 mol%, 80.0 mol% or more but less than 100 mol%, 80.0 to 99.9 mol%, 80.0 to 99.5 mol%, 90.0 mol% or more but less than 100 mol%, 90.0 to 99.9 mol%, or 90.0 to 99.5 mol%. The saponification degree of polyvinyl alcohol is a value measured by a method in accordance with JIS K 6726:1994.

[0069] When the binder contains a water-soluble compound, the content of the water-soluble compound (binder) may be in the following ranges based on the total mass of the negative electrode material, from the viewpoint of easily obtaining excellent life performance. The content of the water-soluble compound may be 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, 0.8 mass% or more, or 1.0 mass% or more. The content of the water-soluble compound may be 20 mass% or less, 15 mass% or less, 10 mass% or less, 8.0 mass% or less, 5.0 mass% or less, 3.0 mass% or less, 2.0 mass% or less, or 1.0 mass% or less. From these viewpoints, the content of the water-soluble compound may be 0.01 to 20% by mass, 0.01 to 10% by mass, 0.01 to 5.0% by mass, 0.1 to 20% by mass, 0.1 to 10% by mass, 0.1 to 5.0% by mass, 0.5 to 20% by mass, 0.5 to 10% by mass, or 0.5 to 5.0% by mass. From the same viewpoint, the content of the compound group or compound included in the water-soluble compound (for example, the content of a polyvinyl polymer (for example, polyvinyl alcohol)) may also be in the above-mentioned range.

[0070] When the binder contains a compound that does not fall under the category of water-soluble compounds, the content of the compound (binder) that does not fall under the category of water-soluble compounds may be in the following ranges relative to 100 parts by mass of the negative electrode active material, from the viewpoint of easily obtaining excellent life performance. The content of the compound that does not fall under the category of water-soluble compounds may be 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 0.8 parts by mass or more, or 1.0 parts by mass or more. The content of the compound that does not fall under the category of water-soluble compounds may be 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, 8.0 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less. From these viewpoints, the content of compounds not corresponding to water-soluble compounds may be 0.01 to 20 parts by mass, 0.01 to 10 parts by mass, 0.01 to 5.0 parts by mass, 0.1 to 20 parts by mass, 0.1 to 10 parts by mass, 0.1 to 5.0 parts by mass, 0.5 to 20 parts by mass, 0.5 to 10 parts by mass, or 0.5 to 5.0 parts by mass. From the same viewpoint, the content of compounds or compounds included in compounds not corresponding to water-soluble compounds (for example, the content of a fluorine-based polymer (for example, PTFE)) may also be in the above-mentioned range.

[0071] The conductive agent may be a metal compound (e.g., a metal oxide) containing at least one metal selected from the group consisting of bismuth, indium, lead, cadmium, thallium, and tin. From the viewpoint of easily achieving excellent life performance, the conductive agent may contain a bismuth compound (a compound containing bismuth) or bismuth oxide.

[0072] From the viewpoint of easily obtaining excellent life performance, the content of the conductive agent may be in the following ranges relative to 100 parts by mass of the negative electrode active material. The content of the conductive agent may be 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 1.5 parts by mass or more, 2.0 parts by mass or more, 2.5 parts by mass or more, 3.0 parts by mass or more, 3.5 parts by mass or more, 4.0 parts by mass or more, 4.5 parts by mass or more, or 5.0 parts by mass or more. The content of the conductive agent may be 50 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, 9.0 parts by mass or less, 8.0 parts by mass or less, 7.0 parts by mass or less, 6.0 parts by mass or less, or 5.5 parts by mass or less. From these viewpoints, the content of the conductive agent may be 0.01 to 50 parts by mass, 0.01 to 20 parts by mass, 0.01 to 8.0 parts by mass, 0.1 to 50 parts by mass, 0.1 to 20 parts by mass, 0.1 to 8.0 parts by mass, 1.0 to 50 parts by mass, 1.0 to 20 parts by mass, or 1.0 to 8.0 parts by mass. From the same viewpoint, the content of the compound group or compound contained in the conductive agent (for example, the content of a bismuth compound (for example, bismuth oxide)) may also be in the above-mentioned range.

[0073] The positive electrode can have a current collector and a positive electrode material (e.g., a positive electrode material layer) supported on the current collector, or can have a current collector and a positive electrode material (e.g., a positive electrode material layer) disposed on at least one of one surface and the other surface of the current collector, or can have a current collector and a positive electrode material (e.g., a positive electrode material layer) disposed on one surface of the current collector, and a positive electrode material (e.g., a positive electrode material layer) disposed on the other surface of the current collector. A positive electrode located at at least one of one end and the other end in the stacking direction of the negative and positive electrodes in the electrode group may have a positive electrode material on one surface and the other surface of the current collector, or may have a positive electrode material on one of the one surface and the other surface of the current collector. For example, the positive electrode located at one end of the electrode assembly in the stacking direction of the negative electrodes and positive electrodes may have a positive electrode material on one side or the other side of the current collector, which is the side closest to the other end of the electrode assembly in the stacking direction of the negative electrodes and positive electrodes, and the positive electrode located at the other end of the electrode assembly in the stacking direction of the negative electrodes and positive electrodes may have a positive electrode material on one side or the other side of the current collector, which is the side closest to the one end of the electrode assembly in the stacking direction of the negative electrodes and positive electrodes. The positive electrode located between two negative electrodes may have a positive electrode material on one side or the other side of the current collector. If the current collector has an opening, the opening may be filled with a positive electrode material.

[0074] The positive electrode current collector forms a conductive path for current from the positive electrode material. Examples of the current collector's shape include a flat plate and a sheet. The current collector may be a three-dimensional mesh structure composed of foamed metal, expanded metal, punched metal, or a metal fiber felt. The current collector may be composed of a conductive and alkali-resistant material. Examples of such materials include materials that are stable even at the reaction potential of the positive electrode (e.g., materials with a redox potential higher than the reaction potential of the positive electrode, or materials that form a protective coating such as an oxide coating on the substrate surface in an alkaline aqueous solution to stabilize the substrate). Furthermore, at the positive electrode, a side reaction occurs in which the electrolyte decomposes, generating oxygen gas. Materials with a high oxygen overvoltage tend to suppress the progression of such side reactions. Examples of materials that can be used to construct the current collector include platinum, copper, brass, steel, and nickel. The current collector may be nickel foam, or a substrate (e.g., copper, brass, steel, etc.) with at least a portion of its surface coated with a metal material (e.g., nickel).

[0075] The positive electrode material contains a nickel-containing positive electrode active material, for example, in a nickel-zinc battery. Examples of the positive electrode active material include nickel oxyhydroxide (NiOOH) and nickel hydroxide. The positive electrode active material may contain one of these components alone or a plurality of components. The positive electrode material may contain nickel oxyhydroxide in a fully charged state and nickel hydroxide in an end-of-discharge state. That is, the positive electrode material may contain at least one selected from the group consisting of nickel oxyhydroxide and nickel hydroxide. The content of the positive electrode active material may be 50% by mass or more but less than 100% by mass, 60 to 99% by mass, or 80 to 95% by mass, based on the total mass of the positive electrode material.

[0076] The positive electrode material may contain additives other than the positive electrode active material. Examples of additives include binders, conductive agents, and expansion inhibitors (e.g., zinc oxide). Examples of binders include hydrophilic or hydrophobic polymers, such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), sodium polyacrylate (SPA), and fluorine-based polymers (e.g., polytetrafluoroethylene (PTFE)). The content of the binder may be, for example, 0.01 to 5 parts by mass per 100 parts by mass of the positive electrode active material. Examples of conductive agents include cobalt compounds (metallic cobalt, cobalt oxide, cobalt hydroxide, etc.) and yttrium compounds (e.g., yttrium oxide). The content of the conductive agent may be, for example, 1 to 20 parts by mass per 100 parts by mass of the positive electrode active material.

[0077] The electrode group according to this embodiment may include one or more separators disposed between the negative electrode and the positive electrode. That is, the negative electrode and the positive electrode may be adjacent to each other via one or more separators. The separator may be pouch-shaped, and at least one of the negative electrode and the positive electrode may be housed in the pouch-shaped separator.

[0078] Examples of materials constituting the separator include organic materials (e.g., resin materials) and inorganic materials. Examples of resin materials include polyamide-based polymers (e.g., polyamide), olefin-based polymers (e.g., polyolefin), and nylon-based polymers (e.g., nylon). Examples of inorganic materials include oxides such as alumina, titania, and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; and sulfates such as barium sulfate and calcium sulfate.

[0079] From the viewpoint of being easily hydrophilized, the separator may contain an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like, and may have been subjected to a surface treatment such as sulfonation treatment, fluorine gas treatment, acrylic acid graft polymerization treatment, corona discharge treatment, or plasma treatment.

[0080] The zinc battery according to this embodiment includes the electrode group according to this embodiment. In the zinc battery according to this embodiment, the plurality of positive electrodes and the plurality of negative electrodes may be connected to each other with straps. The zinc battery according to this embodiment may be either before or after chemical formation. Examples of zinc batteries (e.g., zinc secondary batteries) include nickel-zinc batteries (e.g., nickel-zinc secondary batteries) in which the positive electrode is a nickel electrode; air-zinc batteries (e.g., air-zinc secondary batteries) in which the positive electrode is an air electrode; and silver-zinc batteries (e.g., silver-zinc secondary batteries) in which the positive electrode is a silver oxide electrode. For example, the zinc battery according to this embodiment may be a nickel-zinc battery.

[0081] The zinc battery according to the present embodiment may include a battery case that houses the electrode group. The zinc battery according to the present embodiment may include an electrolyte. The electrolyte may be housed in the battery case.

[0082] The electrolytic solution may contain a solvent and an alkali metal hydroxide. Examples of the solvent include water (e.g., ion-exchanged water). Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, and lithium hydroxide. The alkali metal hydroxide may be ionized (dissociated) in the electrolytic solution (e.g., an aqueous solution) and may exist as a salt. The electrolytic solution may contain hydroxide ions and may contain alkali metal ions. From the viewpoint of easily obtaining excellent life performance, the alkali metal hydroxide may include at least one selected from the group consisting of potassium hydroxide and lithium hydroxide, and may include potassium hydroxide.

[0083] The content of the alkali metal hydroxide may be in the following ranges based on the total mass of the electrolyte solution, from the viewpoint of easily obtaining excellent life performance. The content of the alkali metal hydroxide may be 1 mass% or more, 5 mass% or more, 10 mass% or more, 15 mass% or more, 18 mass% or more, 20 mass% or more, 22 mass% or more, or 25 mass% or more. The content of the alkali metal hydroxide may be 50 mass% or less, 45 mass% or less, 40 mass% or less, 35 mass% or less, 32 mass% or less, 30 mass% or less, or 28 mass% or less. From these viewpoints, the content of the alkali metal hydroxide may be 1 to 50 mass%, 1 to 40 mass%, 1 to 30 mass%, 10 to 50 mass%, 10 to 40 mass%, 10 to 30 mass%, 20 to 50 mass%, 20 to 40 mass%, or 20 to 30 mass%. From the same viewpoint, the content of the compound group or compound included in the alkali metal hydroxide (for example, the content of potassium hydroxide, lithium hydroxide, etc.) may also be within the above-mentioned range.

[0084] The electrolyte may contain components other than the solvent and the alkali metal hydroxide, such as borate ions, surfactants, sugars, glyme compounds, potassium phosphate, potassium fluoride, potassium carbonate, sodium phosphate, sodium fluoride, zinc oxide, antimony oxide, and titanium dioxide.

[0085] The borate ions contained in the electrolyte may be borate ions derived from a boric acid compound (a compound containing boric acid ions). The boric acid compound may be ionized (dissociated) in the electrolyte, or may not be ionized (dissociated) in the electrolyte. The boric acid compound may contain at least one selected from the group consisting of boric acid and borate salts, from the viewpoint of easily obtaining excellent life performance and discharge output performance. Examples of borates include alkali metal borate salts (sodium borate, potassium borate, etc.), zinc borate, etc. The electrolyte may contain a boric acid compound, and may contain at least one selected from the group consisting of boric acid and borate salts, from the viewpoint of easily obtaining excellent life performance and discharge output performance.

[0086] The content of the boric acid compound may be in the following ranges based on the total mass of the electrolyte, from the viewpoint of easily obtaining excellent life performance and discharge output performance. The content of the boric acid compound may be 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, 0.8 mass% or more, or 1 mass% or more. The content of the boric acid compound may be 30 mass% or less, 20 mass% or less, 10 mass% or less, 8 mass% or less, 5 mass% or less, 3 mass% or less, 2 mass% or less, or 1 mass% or less. From these viewpoints, the content of the boric acid compound may be 0.01 to 30 mass%, 0.01 to 10 mass%, 0.01 to 3 mass%, 0.1 to 30 mass%, 0.1 to 10 mass%, 0.1 to 3 mass%, 0.5 to 30 mass%, 0.5 to 10 mass%, or 0.5 to 3 mass%.

[0087] Examples of surfactants include didodecyldimethylammonium bromide, tetradecyltrimethylammonium bromide, polyoxyethylene decyl ether, and polyoxyalkylene alkyl ether phosphate ester.

[0088] Examples of sugars include monosaccharides, disaccharides, trisaccharides, polysaccharides, etc. Examples of monosaccharides include glucose, fructose, galactose, arabinose, ribose, mannose, xylose, sorbose, rhamnose, fucose, ribodecose, and hydrates thereof. Examples of disaccharides include sucrose, maltose, trehalose, cellobiose, gentiobiose, lactose, melibiose, and hydrates thereof. Examples of trisaccharides include kestose, melezitose, gentianose, raffinose, and hydrates thereof. Examples of polysaccharides include cyclodextrins (e.g., γ-cyclodextrin), stachyose, etc.

[0089] Examples of glyme compounds include polyoxyethylene dimethyl ether, polyoxyethylene diethyl ether, polyoxyethylene dipropyl ether, polyoxyethylene dibutyl ether, polyoxyethylene dipentyl ether, polyoxyethylene dihexyl ether, polyoxyethylene diheptyl ether, polyoxyethylene dioctyl ether, and polyoxyethylene methyl ethyl ether.

[0090] The glyme compound may be a monoglyme compound such as monoglyme (also known as ethylene glycol dimethyl ether), ethylene glycol diethyl ether, ethylene glycol dipropyl ether, or ethylene glycol dibutyl ether; a diglyme compound such as diglyme (also known as diethylene glycol dimethyl ether), diethylene glycol diethyl ether, diethylene glycol dipropyl ether, or diethylene glycol dibutyl ether; a triglyme compound such as triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dipropyl ether, or triethylene glycol dibutyl ether; or a tetraglyme compound such as tetraglyme (also known as tetraethylene glycol dimethyl ether), tetraethylene glycol diethyl ether, tetraethylene glycol dipropyl ether, or tetraethylene glycol dibutyl ether. From the viewpoint of easily obtaining excellent life performance and high rate discharge performance, the glyme compound may include at least one selected from the group consisting of monoglyme compounds, diglyme compounds, triglyme compounds, and tetraglyme compounds, may include at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme, may include at least one selected from the group consisting of diglyme and triglyme, or may include diglyme.

[0091] From the viewpoint of easily obtaining excellent life performance and high-rate discharge performance, the content of the glyme compound may be in the following ranges based on the total mass of the electrolyte: 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, 0.8 mass% or more, or 1.0 mass% or more; and 20 mass% or less, 10 mass% or less, 8.0 mass% or less, 5.0 mass% or less, 3.0 mass% or less, 2.5 mass% or less, 2.0 mass% or less, 1.5 mass% or less, or 1.0 mass% or less. From these viewpoints, the content of the glyme compound may be 0.01 to 20% by mass, 0.01 to 10% by mass, 0.01 to 5.0% by mass, 0.1 to 20% by mass, 0.1 to 10% by mass, 0.1 to 5.0% by mass, 0.5 to 20% by mass, 0.5 to 10% by mass, or 0.5 to 5.0% by mass.

[0092] From the viewpoint of easily obtaining excellent life performance and high-rate discharge performance, the content of the glyme compound may be in the following ranges per 100 parts by mass of the alkali metal hydroxide: The content of the glyme compound may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 1.5 parts by mass or more, 2.0 parts by mass or more, 2.5 parts by mass or more, 3.0 parts by mass or more, or 3.5 parts by mass or more. The content of the glyme compound may be 30 parts by mass or less, 20 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 8.0 parts by mass or less, 6.0 parts by mass or less, 5.5 parts by mass or less, 5.0 parts by mass or less, 4.5 parts by mass or less, or 4.0 parts by mass or less. From these viewpoints, the content of the glyme compound may be 0.1 to 30 parts by mass, 0.1 to 10 parts by mass, 0.1 to 5.0 parts by mass, 1.0 to 30 parts by mass, 1.0 to 10 parts by mass, 1.0 to 5.0 parts by mass, 3.0 to 30 parts by mass, 3.0 to 10 parts by mass, or 3.0 to 5.0 parts by mass.

[0093] In the above explanation, an example of a nickel-zinc battery (e.g., a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode has been described, but the zinc battery may also be an air-zinc battery (e.g., an air-zinc secondary battery) in which the positive electrode is an air electrode, or a silver-zinc battery (e.g., a silver-zinc secondary battery) in which the positive electrode is a silver oxide electrode.

[0094] The air electrode of the air-zinc battery can be a known air electrode used in air-zinc batteries. The air electrode may include an air electrode catalyst, an electron conductive material, etc. The air electrode catalyst can be an air electrode catalyst that also functions as an electron conductive material.

[0095] The air electrode catalyst can be a catalyst that functions as a positive electrode in an air-zinc battery, and various air electrode catalysts that can utilize oxygen as a positive electrode active material can be used. Examples of air electrode catalysts include carbon-based materials (such as graphite) that have redox catalytic functions, metal materials (such as platinum and nickel) that have redox catalytic functions, and inorganic oxide materials (such as perovskite-type oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel oxide) that have redox catalytic functions. The shape of the air electrode catalyst is not particularly limited, but it may be, for example, particulate. The content of the air electrode catalyst in the air electrode may be 5 to 70 volume %, 5 to 60 volume %, or 5 to 50 volume % relative to the total volume of the air electrode.

[0096] The electron-conductive material may be a material that is electrically conductive and allows electron conduction between the air electrode catalyst and the separator. Examples of electron-conductive materials include carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black, and thermal black; graphites such as natural graphite (e.g., flake graphite), artificial graphite, and expanded graphite; conductive fibers such as carbon fiber and metal fiber; metal powders such as copper, silver, nickel, and aluminum; and organic electron-conductive materials such as polyphenylene derivatives. The electron-conductive material may be in the form of particles or other shapes. The electron-conductive material may be used in a form that provides a continuous phase in the thickness direction of the air electrode. For example, the electron-conductive material may be a porous material. The electron-conductive material may be in the form of a mixture or composite with the air electrode catalyst, or, as described above, may be an air electrode catalyst that also functions as an electron-conductive material. The content of the electronically conductive material in the cathode may be 10 to 80 vol %, 15 to 80 vol %, or 20 to 80 vol %, based on the total volume of the cathode.

[0097] The silver oxide electrode of the silver-zinc battery may be a known silver oxide electrode used in silver-zinc batteries, such as silver(I) oxide.

[0098] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0099] <Preparation of Negative Electrode> A tin-plated punched steel plate (opening ratio: 50%) was prepared as a negative electrode current collector. Next, zinc oxide (Mitsui Mining & Smelting Co., Ltd., general product), metallic zinc (Mitsui Mining & Smelting Co., Ltd., trade name: MA-ZB), polyvinyl alcohol (PVA, saponification degree: 99 mol%, Kuraray Co., Ltd., trade name: Poval 60-98), PTFE dispersion (Daikin Industries, Ltd., trade name: D-210C), bismuth oxide (Corefront Co., Ltd., trade name: 1710CY), and ion-exchanged water were mixed and kneaded to prepare a negative electrode material paste. At this time, the mass ratio of the solids (non-volatile contents) was adjusted to "zinc oxide: metallic zinc: PVA: PTFE: bismuth oxide = 75:16:3:1:5". The water content of the negative electrode material paste was adjusted to 20% by mass based on the total mass of the negative electrode material paste. Next, the negative electrode material paste was applied to the negative electrode material support portion of the negative electrode current collector, and then dried at 80°C for 30 minutes. Thereafter, the negative electrode material (dimensions of the negative electrode material support portion: length 5.0 cm × width 4.0 cm (area: 20.0 cm)) was obtained by pressure molding using a roll press. ２ An unformed negative electrode having a negative electrode material was obtained. In this negative electrode, the openings of the negative electrode current collector were filled with the negative electrode material, and the negative electrode material was formed on both sides of the negative electrode current collector, as shown in Figure 1. The mass and thickness of the negative electrode material were adjusted by adjusting the amount of negative electrode material paste used. The content of PVA was 1 mass% based on the total mass of the negative electrode material.

[0100] <Preparation of Positive Electrode> A positive electrode current collector was obtained by pressure molding a grid (porosity: 95%) made of foamed nickel. Next, cobalt-coated nickel hydroxide powder (manufactured by Gold Shine Energy Material Co., Ltd., trade name: Y6), carboxymethyl cellulose (CMC, manufactured by Weiyi Chemical (Suzhou) Co., Ltd., trade name: BH90-3), polytetrafluoroethylene (PTFE, manufactured by Daikin Industries, Ltd., trade name: D210-C), metal cobalt (manufactured by Nikkoshi Co., Ltd., trade name: EXTRA FINE), cobalt hydroxide (manufactured by Ise Chemical Industry Co., Ltd.), yttrium oxide (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd., reagent grade) and ion-exchanged water were mixed and kneaded to prepare a positive electrode material paste. At this time, the mass ratio of the solid content (non-volatile content) was adjusted to "nickel hydroxide: CMC: PTFE: metallic cobalt: cobalt hydroxide: yttrium oxide = 88.0: 0.3: 0.1: 10.3: 0.3: 1.0". The moisture content of the positive electrode material paste was adjusted to 27.5 mass% based on the total mass of the positive electrode material paste. Next, the positive electrode material paste was applied to the positive electrode material support portion of the positive electrode current collector and then dried at 80 ° C. for 30 minutes. Thereafter, by pressure molding using a roll press, an unformed positive electrode having a positive electrode material (dimensions of the positive electrode material support portion: length 5.0 cm x width 3.5 cm) was obtained.

[0101] <Preparation of Separator> A porous membrane (manufactured by Ube Industries, Ltd., product name: UP3355, air permeability: 440 sec / 100 mL) and a nonwoven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., product name: VL-100, air permeability: 0.3 sec / 100 mL, length 10 cm × width 3.5 cm) were prepared as separators. The porous membrane was previously hydrophilized with Triton-X100 (surfactant, product name: Sigma-Aldrich Japan G.K.). The hydrophilization treatment was performed by immersing the porous membrane in an aqueous solution containing 1% by mass of Triton-X100 for 24 hours and then drying at 25°C for 1 hour. A rectangular porous membrane was folded in half, and the folded portion was used as the bottom, and both sides were heat-sealed to form a bag (length 5.0 cm × width 4.2 cm). The air permeability is a value measured by a method according to JIS P 8117: 2009. The air permeability of the porous membrane is a value after hydrophilization treatment.

[0102] <Preparation of Electrolyte Solution> An electrolyte solution was prepared by mixing potassium hydroxide (KOH), lithium hydroxide (LiOH), boric acid, diglyme, and ion-exchanged water. Based on the total mass of the electrolyte solution, the content of potassium hydroxide was 25.0 mass%, the content of lithium hydroxide was 1.0 mass%, the content of boric acid was 1.0 mass%, the content of diglyme was 1.0 mass%, and the content of ion-exchanged water was 72.0 mass%.

[0103] <Preparation of nickel-zinc battery> Nickel-zinc batteries having the configuration of Fig. 1, such as negative electrodes A1 to A3, B1 to B3 (negative electrodes having negative electrode materials a11, a12, a21, a22, a31, a32, b11, b12, b21, b22, b31, b32, etc.), were prepared by the procedure described below. In each of Comparative Examples 1-1, 2-1, 3-1, 4-1, and 5-1, eight identical negative electrodes were used as reference negative electrodes. The mass of the negative electrode active material (Table 1), the mass of the negative electrode (Table 2), the average thickness of the negative electrode (Table 3), and the average thickness of the negative electrode material (Tables 4 and 5) of Comparative Examples 1-1, 2-1, 3-1, 4-1, and 5-1 are set to 100. In the Examples and other Comparative Examples in Table 1, negative electrodes having the mass of the negative electrode active material shown in Table 1 were used. In the Examples and other Comparative Examples in Table 2, negative electrodes having the mass shown in Table 2 were used. In the Examples and other Comparative Examples in Table 3, negative electrodes having the average thickness shown in Table 3 were used. In the Examples and other Comparative Examples in Tables 4 and 5, negative electrodes having negative electrode material with the average thickness shown in Tables 4 and 5 were used. The mass of the reference negative electrode was 3.1 g (0.17 g / cm ２ ), and the mass of the negative electrode active material in the reference negative electrode was 2.2 g (0.12 g / cm ２ ), and the mass of the negative electrode current collector of the reference negative electrode was 0.9 g (0.05 g / cm ２ The average thickness (total thickness) of the reference negative electrode was 0.410 mm, the average thickness of each negative electrode material of the reference negative electrode was 0.155 mm, and the average thickness of the negative electrode current collector of the reference negative electrode was 0.100 mm. The average thickness was the average value of the thicknesses at a total of nine locations on the measurement object.

[0104] First, an unformed negative electrode and an unformed positive electrode were housed in a bag-shaped porous membrane. The negative electrode housed in the bag-shaped porous membrane, the positive electrode housed in the bag-shaped porous membrane, and a nonwoven fabric were stacked, and then electrodes of the same polarity were connected with a strap to prepare an electrode group. In the electrode group, eight negative electrodes and seven positive electrodes were alternately stacked, and one nonwoven fabric was placed between the negative and positive electrodes (between the porous membrane on the negative electrode side and the porous membrane on the positive electrode side). After placing this electrode group in a battery case, a lid was attached to the top of the battery case. An electrolyte was poured into the battery case to obtain an unformed nickel-zinc battery. Subsequently, charging (chemical conversion) was performed at an ambient temperature of 25°C, 270 mA, and 12 hours to prepare a nickel-zinc battery with a rated capacity of 2700 mAh.

[0105] <Evaluation of Life Performance> The life performance of the nickel-zinc batteries in a high-temperature environment was evaluated according to the following procedure. The number of cycles for Comparative Examples 1-1, 2-1, 3-1, 4-1 and 5-1 was set to 100, and the results are shown in Tables 1 to 5.

[0106] A test was conducted in which the nickel-zinc battery was charged at an ambient temperature of 25°C at a constant voltage of 1.88 V at 369.6 mA (0.33 C) until the current value decayed to 56 mA (0.05 C), and then discharged at a constant current of 369.6 mA (0.33 C) until the battery voltage reached 1.1 V. The discharge capacity at the first cycle was defined as 100%, and the number of cycles at which the discharge capacity decreased to 70% was calculated.

[0107] The "C" represents the relative magnitude of the current when discharging the rated capacity from a fully charged state at a constant current, and means "discharge current value (A) / battery capacity (Ah)." For example, a current that can discharge the rated capacity in 1 hour is defined as "1 C," and a current that can discharge the rated capacity in 2 hours is defined as "0.5 C."

[0108]

[0109]

[0110]

[0111]

[0112]

[0113] 1...zinc battery, 10...electrode group, 12...negative electrode, 14...positive electrode, A1 to A4, B1 to B4...negative electrode, a11, a12, a21, a22, a31, a32, b11, b12, b21, b22, b31, b32...negative electrode material, C...current collector.

Claims

1. An electrode group comprising negative electrodes and positive electrodes stacked on top of each other, wherein the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode A2 is greater than the mass of the active material in negative electrode A3.

2. The electrode group according to claim 1, wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrode and the positive electrode.

3. The electrode group according to claim 1, wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 have a negative electrode material containing an active material containing zinc, and the mass of the active material in negative electrode B2 is greater than the mass of the active material in negative electrode B3.

4. The electrode group according to claim 3, wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrode and the positive electrode.

5. An electrode group comprising negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the mass of the negative electrode A2 is greater than the mass of the negative electrode A3.

6. The electrode group according to claim 5, wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

7. The electrode group according to claim 5, wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 have a negative electrode material containing an active material containing zinc, and the mass of the negative electrode B2 is greater than the mass of the negative electrode B3.

8. The electrode group according to claim 7, wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

9. An electrode group comprising negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as the first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrodes A1 to A3 have a negative electrode material containing an active material containing zinc, and the average thickness of the negative electrode A2 is greater than the average thickness of the negative electrode A3.

10. The electrode group according to claim 9, wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

11. The electrode group according to claim 9, wherein the negative electrodes include negative electrodes B1 to B3 as the first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrodes B1 to B3 have a negative electrode material containing an active material containing zinc, and the average thickness of negative electrode B2 is greater than the average thickness of negative electrode B3.

12. The electrode group according to claim 11, wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

13. An electrode group comprising negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrodes A1 to A3 as first to third negative electrodes counting from one end side in the stacking direction of the negative electrodes and the positive electrodes in the electrode group, the negative electrode A2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A3, the negative electrode A3 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A2, the negative electrode material of the negative electrode A2 and the negative electrode material of the negative electrode A3 contain an active material containing zinc, and the average thickness of the negative electrode material of the negative electrode A2 is greater than the average thickness of the negative electrode material of the negative electrode A3.

14. The electrode group according to claim 13, wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

15. The electrode group according to claim 13, wherein the negative electrodes include negative electrodes B1 to B3 as first to third negative electrodes counting from the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes, the negative electrode B2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B3, the negative electrode B3 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B2, the negative electrode material of negative electrode B2 and the negative electrode material of negative electrode B3 contain an active material containing zinc, and the average thickness of the negative electrode material of negative electrode B2 is greater than the average thickness of the negative electrode material of negative electrode B3.

16. The electrode group according to claim 15, wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

17. An electrode group comprising negative electrodes and positive electrodes stacked on each other, wherein the negative electrodes include negative electrode A1 and negative electrode A2 as first and second negative electrodes counting from one end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, the negative electrode A1 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A2, the negative electrode A2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode A1, the negative electrode material of the negative electrode A1 and the negative electrode material of the negative electrode A2 contain an active material containing zinc, and the average thickness of the negative electrode material of the negative electrode A2 is greater than the average thickness of the negative electrode material of the negative electrode A1.

18. The electrode group according to claim 17, wherein the negative electrode A1 is located at one end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

19. The electrode group according to claim 17, wherein the negative electrodes include negative electrode B1 and negative electrode B2 as first and second negative electrodes counting from the other end side in the stacking direction of the negative electrodes and positive electrodes in the electrode group, negative electrode B1 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B2, negative electrode B2 has a current collector and a negative electrode material arranged on the surface of the current collector facing the negative electrode B1, the negative electrode material of negative electrode B1 and the negative electrode material of negative electrode B2 contain an active material containing zinc, and the average thickness of the negative electrode material of negative electrode B2 is greater than the average thickness of the negative electrode material of negative electrode B1.

20. The electrode group according to claim 19, wherein the negative electrode B1 is located at the other end of the electrode group in the stacking direction of the negative electrodes and the positive electrodes.

21. A zinc battery comprising an electrode group according to any one of claims 1 to 20.

22. The zinc battery of claim 21, which is a nickel-zinc battery.

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