Cylindrical alkaline storage battery

Abstract

The present application provides an alkaline storage battery which exhibits excellent battery characteristics over a wide temperature range. In the alkaline storage battery (10) of the present application, a wound electrode group is divided into a first portion (I) containing the outermost portion of each of a positive electrode (1) and a negative electrode (2), and a second portion (II) which is more inward than the first portion (I). The first portion (I) contains the outermost portion of the positive electrode (1) and a portion from a position b1 of the negative electrode opposite a position a1 of the innermost portion of the outermost portion of the positive electrode (1) to the outermost end b2 of the negative electrode. (1) The capacity per unit area N1 of the negative electrode (2) of each of the first portion (I) and the second portion (II) satisfies N2 > N1. (2) The capacity Pa of the positive electrode (1) and the capacity Na of the negative electrode (2) of the entire first portion, and the capacity Pb of the positive electrode (1) and the capacity Nb of the negative electrode (2) of the entire second portion satisfy 1.04 ≤ Na / Pa ≤ 1.26 and 1.80 ≤ Nb / Pb ≤ 2.22.

Description

Technical Field

[0001] This application relates to cylindrical alkaline batteries. Background Technology

[0002] Alkaline batteries, for example, include an electrode assembly, an alkaline electrolyte, and a metal battery casing (outer can) housing them. The electrode assembly comprises a positive electrode, a negative electrode, and a spacer disposed between them. In nickel-metal hydride (NiMH) batteries, a type of alkaline battery, nickel oxides containing nickel hydroxyl oxide and nickel hydroxide are primarily used as the positive electrode active material, and a hydrogen storage alloy is used as the negative electrode active material. From the viewpoint of improving the performance of alkaline batteries, various improvements have been attempted to the electrode assembly or its constituent elements.

[0003] Patent Document 1 discloses a cylindrical battery comprising an electrode assembly, an electrolyte, a bottomed cylindrical battery casing containing the electrode assembly and the electrolyte and having an opening, and a sealing plate for sealing the opening. The electrode assembly is formed by winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped first spacer between the positive and negative electrodes.

[0004] The aforementioned negative electrode comprises a negative electrode current collector and negative electrode active material layers formed on the two surfaces of the aforementioned negative electrode current collector.

[0005] The aforementioned negative electrode includes a thin-walled portion disposed in a region with a length L3 from the outer end of the aforementioned negative electrode, a tapered portion adjacent to the aforementioned thin-walled portion, and a main body portion other than the above.

[0006] The thickness t of the negative electrode active material layer on the outer peripheral side of the main body is described above. 1o The thickness t of the negative electrode active material layer on the outer peripheral side of the aforementioned thin-walled portion 3o Satisfying t 1o >t 3o ,

[0007] The thickness t of the negative electrode active material layer on the outer periphery of the aforementioned conical portion 2o It decreases in size at an angle from the main body side toward the thin-walled side.

[0008] In the above-mentioned electrode assembly, the outer end of the positive electrode is sandwiched between the first spacer and overlaps with the conical portion, and a second spacer is also included between the outer end of the positive electrode and the conical portion.

[0009] Patent Document 2 discloses a nickel-hydrogen battery for backup power, which has a positive electrode mainly composed of nickel hydroxide, a negative electrode mainly composed of hydrogen storage alloy powder, a spacer and an alkaline electrolyte. It is a battery that is maintained by intermittent charging. The theoretical capacity ratio of the positive electrode to the negative electrode is 1:1.5 to 1:2.0, and the amount of alkaline electrolyte is 1.7 to 3.5 g per Ah relative to the theoretical capacity of the positive electrode.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: International Publication No. 2017 / 09219

[0013] Patent Document 2: Japanese Patent Application Publication No. 11-329481 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] For alkaline batteries, excellent battery characteristics are sometimes required over a wide temperature range.

[0016] Methods for solving problems

[0017] One aspect of this application relates to a cylindrical alkaline battery comprising a wound electrode assembly and an alkaline electrolyte, and a cylindrical casing housing them.

[0018] In the aforementioned electrode assembly, the negative electrode, the positive electrode, and the spacer between the positive and negative electrodes are wound into a spiral shape. The negative electrode comprises a hydrogen storage alloy capable of electrochemically absorbing, storing, and releasing hydrogen.

[0019] The aforementioned electrode assembly is divided into a first part, which includes the outermost portions of both the positive and negative electrodes, and a second part, which is located further inward than the first part.

[0020] In the aforementioned electrode assembly, the outermost portion of the negative electrode is located further outward than the outermost portion of the positive electrode.

[0021] Part 1 above includes:

[0022] (i) the outermost peripheral portion of the aforementioned positive electrode; and

[0023] (ii) The portion from position b1 of the negative electrode, which is opposite to the innermost circumferential side of the outermost circumferential portion of the positive electrode and separated by the spacer, to the outermost end b2 of the negative electrode.

[0024] (1) The capacity N1 per unit area of ​​the negative electrode in the first part and the capacity N2 per unit area of ​​the negative electrode in the second part satisfy N2 > N1.

[0025] (2) The capacity Pa of the positive electrode of the whole in the first part, the capacity Pb ​​of the positive electrode of the whole in the second part, the capacity Na of the negative electrode of the whole in the first part, and the capacity Nb of the negative electrode of the whole in the second part satisfy 1.04≤Na / Pa≤1.26 and 1.80≤Nb / Pb≤2.22.

[0026] Invention Effects

[0027] According to this application, it is possible to provide an alkaline rechargeable battery that exhibits excellent battery characteristics. Attached Figure Description

[0028] Figure 1 This is a partially exploded perspective view schematically illustrating one embodiment of a cylindrical alkaline storage battery.

[0029] Figure 2 This is a cross-sectional schematic diagram illustrating the first and second parts of the coiled electrode assembly in the open state.

[0030] Figure 3 This is a cross-sectional schematic diagram used to illustrate a wound electrode assembly. Detailed Implementation

[0031] For alkaline batteries, excellent discharge characteristics are required, such as the ability to discharge smoothly even at low temperatures (e.g., -20°C). To ensure excellent discharge characteristics at low temperatures, increasing the hydrogen equilibrium pressure is advantageous. However, if the hydrogen equilibrium pressure is increased, hydrogen gas is easily generated when the battery is exposed to high temperatures (e.g., when the battery is stored at high temperatures), and the internal pressure of the battery tends to increase. If the internal pressure of the battery increases, electrolyte leakage occurs. Therefore, high-temperature storage characteristics and low-temperature discharge characteristics tend to be inversely related and are usually difficult to achieve simultaneously. Thus, for example, it is difficult to ensure excellent battery characteristics (high-temperature storage characteristics and low-temperature discharge characteristics, etc.) in alkaline batteries over a wide temperature range, such as -30°C to +105°C.

[0032] (Technical 1) In view of the above, the cylindrical alkaline battery of this application includes a wound electrode assembly and an alkaline electrolyte, and a cylindrical casing housing them. In the electrode assembly, a negative electrode, a positive electrode, and a spacer between the positive and negative electrodes are wound into a spiral shape. The negative electrode includes a hydrogen storage alloy capable of electrochemically absorbing and releasing hydrogen. The electrode assembly is divided into a first portion including the outermost peripheral portions of both the positive and negative electrodes, and a second portion further to the inner periphery than the first portion. In the electrode assembly, the outermost peripheral portion of the negative electrode is located further to the outer periphery than the outermost peripheral portion of the positive electrode. The first portion includes:

[0033] (i) the outermost peripheral portion of the aforementioned positive electrode; and

[0034] (ii) The portion from the position b1 of the negative electrode opposite the position a1 of the outermost peripheral portion of the positive electrode, which is separated from the spacer mentioned above, to the outermost end b2 of the negative electrode.

[0035] Furthermore, regarding cylindrical alkaline batteries,

[0036] (1) The capacity N1 per unit area of ​​the negative electrode in the first part and the capacity N2 per unit area of ​​the negative electrode in the second part satisfy N2 > N1.

[0037] (2) The capacity Pa of the positive electrode of the whole in the first part, the capacity Pb ​​of the positive electrode of the whole in the second part, the capacity Na of the negative electrode of the whole in the first part, and the capacity Nb of the negative electrode of the whole in the second part satisfy 1.04≤Na / Pa≤1.26 and 1.80≤Nb / Pb≤2.22.

[0038] In this application, in the cylindrical alkaline battery, as described above, for the first and second portions of the electrode assembly, N2 > N1, and the Na / Pa ratio and Nb / Pb ratio are set to specific ranges. This ensures high discharge characteristics at low temperatures (e.g., temperatures below 0°C (above -30°C and below 0°C, etc.)) and excellent high-temperature storage characteristics. More specifically, by setting 1.04 ≤ Na / Pa and 1.80 ≤ Nb / Pb, the discharge reaction in the negative electrode proceeds easily, resulting in excellent low-temperature discharge characteristics. Furthermore, by satisfying 1.04 ≤ Na / Pa ≤ 1.26 and 1.80 ≤ Nb / Pb ≤ 2.22, when storing the battery at high temperatures (e.g., temperatures above 80°C (above 80°C and below 120°C, etc.)), the generated hydrogen gas can be readily absorbed, and due to the adequate remaining space within the battery, the internal pressure of the battery can be absorbed. N2 > N1, and based on the aforementioned Na / Pa ratio and Nb / Pb ratio, more hydrogen is readily absorbed by the second part. Therefore, even when a relatively large amount of hydrogen is generated during high-temperature battery storage, the increase in internal battery pressure can be suppressed. Thus, in this application, excellent battery characteristics (more specifically, low-temperature discharge characteristics and high-temperature storage characteristics) are obtained over a wide temperature range.

[0039] (Technology 2) In (Technology 1) above, the hydrogen balance pressure of the aforementioned hydrogen storage alloy at 45°C can be 0.73 MPa or more and 1.51 MPa or less. By using a hydrogen storage alloy with a hydrogen balance pressure within this range, compared to cases where the Na / Pa ratio and Nb / Pb ratio are outside the aforementioned range, the rise in internal battery pressure can be suppressed even when the battery is stored at high temperatures for a longer period of time. It should be noted that, in this specification, the hydrogen balance pressure at 45°C refers to the hydrogen balance pressure when the hydrogen storage capacity H / M of the hydrogen storage alloy is 0.5.

[0040] (Technology 3) In (Technology 1) or (Technology 2) above, the negative electrode may comprise a mixture selected from AB5 type hydrogen storage alloy, A2B7 type hydrogen storage alloy, and A5B. 19 At least one of the following types of hydrogen storage alloys.

[0041] (Technology 4) In any of (Technology 1) to (Technology 3) above, the negative electrode of the first part may include a portion that is thinner than the negative electrode of the second part. In this case, it is easy to ensure excellent battery characteristics over a wide temperature range, and it is easy to reduce the diameter of the electrode assembly, thus making it easier to achieve high battery capacity.

[0042] (Technology 5) In any of (Technology 1) to (Technology 3) above, the thickness of the negative electrode in the first part can be the same as the thickness of the negative electrode in the second part. In this case, excellent battery characteristics can also be ensured over a wide temperature range.

[0043] Including (Technique 1) to (Technique 5) described above, the alkaline storage battery of this application will be described in more detail below. At least one of the constituent elements selected from the following description can be arbitrarily combined with at least one of (Technique 1) to (Technique 5) mentioned above in relation to the alkaline storage battery of this application, as long as they can be technically combined.

[0044] [Alkaline storage battery]

[0045] The alkaline battery of this application includes a wound electrode assembly and an alkaline electrolyte, as well as a cylindrical casing that houses them.

[0046] (Electrode assembly)

[0047] In the electrode assembly, the negative electrode, the positive electrode, and the spacer between the positive and negative electrodes are wound into a spiral shape, wherein the negative electrode contains a hydrogen storage alloy capable of electrochemically absorbing and releasing hydrogen.

[0048] The electrode assembly is divided into a first part containing the outermost portions of both the positive and negative electrodes, and a second part located further inward than the first part. Within the electrode assembly, the outermost portion of the negative electrode is positioned further inward than the outermost portion of the positive electrode.

[0049] Figure 2 This is a schematic diagram illustrating parts 1 and 2 with the electrode assembly in the open state. Figure 2 This is a schematic cross-sectional view of the outermost part of the wound electrode assembly and its surrounding parts cut along the length of each electrode. Figure 3 This is a cross-sectional schematic diagram used to illustrate the electrode assembly (wound electrode assembly). Figure 3 This is a schematic cross-sectional view when cut along a direction perpendicular to the winding axis of the wound electrode assembly.

[0050] Figure 2 This is a diagram used to illustrate Part 1. Figure 2 and Figure 3 It is not merely intended to illustrate specific implementation methods. Figure 2 and Figure 3 The description and constituent elements can be arbitrarily combined with the constituent elements described in this specification. Figure 2 and Figure 3 The description following this description is for the purpose of explaining the cylindrical alkaline storage battery of this application, and is not limited to it. Figure 2 and Figure 3 The implementation method.

[0051] like Figure 3As shown, in the wound electrode assembly, the negative electrode 1 and the positive electrode 2 are wound into a spiral shape, separated by a spacer 3. In the electrode assembly, the outermost portion of the negative electrode 1, separated by the spacer 3, also exists outside the outermost portion of the positive electrode 2. The spacer 3 can be further arranged outside the outermost portion of the negative electrode 1. In this case, opening the portion of each electrode assembly containing its outermost portion is equivalent to... Figure 2 .

[0052] exist Figure 2 In this electrode assembly, Part I includes: (i) the outermost peripheral portion 2a of the positive electrode 2; and (ii) the portion extending from position b1 of the negative electrode 1, which is opposite to the innermost peripheral side of the positive electrode 2, separated by the spacer 3, to the outermost end b2 of the negative electrode 1. Part I may also include: (iii) the portion of the spacer 3 that is opposite to the negative electrode 1 between positions b1 and b2. This portion of the spacer 3 opposite to the negative electrode 1 may be the portion between the positive electrode 2 and the negative electrode 1, or it may be this portion and a portion located further outward than the outermost peripheral portion of the negative electrode 1. The portion of the electrode assembly outside Part I is Part II.

[0053] In the cylindrical alkaline battery of this application, (1) N2 > N1, and (2) 1.04 ≤ Na / Pa ≤ 1.26 and 1.80 ≤ Nb / Pb ≤ 2.22. This ensures high discharge performance at low temperatures and excellent high-temperature storage characteristics. In other words, excellent battery characteristics can be obtained over a wide temperature range.

[0054] The N1, N2, Na, Nb, Pa, and Pb values ​​related to the capacity of the negative and positive electrodes are determined from the negative and positive electrodes taken from the battery using the following steps.

[0055] First, for the positive and negative electrodes, calculate the mass ratio of Part 1 to Part 2 respectively.

[0056] Remove the positive electrode mixture from the positive electrode plate and determine the amount of nickel hydroxide it contains. For example, dissolve the positive electrode mixture in hydrochloric acid and determine the Ni concentration in the solution using inductively coupled plasma (ICP) luminescence spectrophotometry. Calculate the mass of nickel hydroxide in the positive electrode based on this Ni concentration. Calculate the mass ratio of nickel hydroxide in each part based on the mass ratio of this nickel hydroxide and the mass ratio of the first and second parts of the positive electrode. Calculate the positive electrode capacities Pa and Pb for each part based on the mass ratio of nickel hydroxide in the first and second parts and the theoretical capacity of nickel hydroxide, 289 mAh / g.

[0057] Remove the negative electrode mixture from the negative electrode plate and determine the electrode capacity of the negative electrode. For example, mix the removed negative electrode mixture with nickel powder at a mass ratio of 1:1. Use a tablet forming machine (10 mm inner diameter) at a pressure of 10 tf / cm². 2 The resulting mixture (≈980 MPa) is pressurized to 1 g for 5 minutes to produce granules. The granules are held in place by a nickel mesh, and spot-welded around the mesh and the nickel leads are also spot-welded to create an electrode containing the negative electrode compound. This electrode, along with a sintered nickel electrode as a counter electrode, is immersed in a 7 mol / L potassium hydroxide aqueous solution to form a battery with a limited negative electrode capacity. The battery is charged for 16 hours in a constant temperature bath at 25°C, for example, at a current of 30 mA / g per 1 g of negative electrode compound. After a 10-minute pause, it is discharged at a current of 60 mA / g per 1 g of negative electrode compound until it reaches -0.5 V relative to the mercury oxide electrode. The electrode capacity per 1 g of negative electrode compound is determined based on this discharge capacity. Then, based on this capacity and the mass ratio of Part 1 to Part 2, the capacities per unit area of ​​each part, N1 and N2, are determined.

[0058] Na is obtained by multiplying N1 by the area of ​​the first part. Nb is obtained by multiplying N2 by the area of ​​the second part.

[0059] (negative electrode)

[0060] The negative electrode may include, for example, a negative electrode binder layer. The negative electrode may include a core material and a negative electrode binder layer attached to the core material.

[0061] As a negative electrode core material, known core materials can be cited. For example, a conductive substrate can be cited as a negative electrode core material. The substrate can be sheet-like. The substrate can be a porous substrate with multiple through holes, or a substrate without through holes. Examples of porous substrates include perforated metal, sintered metal powder, expanded metal mesh, and metal mesh (nickel mesh, etc.).

[0062] Materials that can be used to form the core material include iron or iron alloys (such as stainless steel), nickel or its alloys, etc. The core material can be plated as needed.

[0063] The negative electrode adhesive layer is formed, for example, at least on the surface of the core material. The negative electrode adhesive layer can be formed on one surface or both surfaces of the sheet-like core material. In the case of a porous core material, the negative electrode adhesive layer can be formed by filling the pores of the core material with the negative electrode adhesive. The negative electrode adhesive layer can be formed by shaping the negative electrode adhesive or by adhering the negative electrode adhesive to the core material.

[0064] The negative electrode binder comprises powder of a hydrogen storage alloy that serves as the negative electrode active material and is capable of electrochemically absorbing, storing, and releasing hydrogen. It may also contain a dispersion medium. Furthermore, known components used in negative electrode binders, such as binders, conductive agents, and thickeners, may be added as needed. Specifically, the negative electrode binder layer can be formed, for example, by coating the core material with the negative electrode binder, removing the dispersion medium by drying, and applying pressure in the thickness direction.

[0065] As a hydrogen storage alloy, for example, a material can be used that can absorb and store hydrogen generated electrochemically in an alkaline electrolyte during charging, and can easily release the absorbed hydrogen during discharge. Hydrogen storage alloys known in the field of nickel-metal hydride batteries can also be used.

[0066] The preferred hydrogen storage alloy contains Ni and Mg. In addition to these elements, it may also contain at least one element selected from the 4th to 6th periods of Groups 2 to 6 of the periodic table (including lanthanides), the 4th period of Groups 7 to 9 and 11 to 12, and the 3rd to 5th periods of Groups 13 to 14.

[0067] Hydrogen storage alloys preferably contain the elements Ln, Ni, and Al. In addition to these elements, they may also contain Mg, and may also contain at least one element M (selected from V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Ga, Zn, Sn, In, Cu, Si, P, and B). Element Ln is selected from at least one element from Group 3 and Group 4 of the periodic table. Element Ln is preferably selected from at least one element from Y, the lanthanides, Zr, and Ti (especially at least one element selected from La, Ce, Pr, Nd, Sm, and Zr). Element Ln may contain La and elements other than La (such as Ce), and may also contain Nd.

[0068] In a hydrogen storage alloy containing elements Ln, Ni, Al, and, if necessary, Mg, the molar ratio x of Mg in the total Ln and Mg can be 0 ≤ x ≤ 0.20 or less, or 0 ≤ x ≤ 0.15 or less. When the hydrogen storage alloy contains Mg, the lower limit of the above range for x can be 0 < x. The molar ratio y of Ni relative to the total Ln and Mg can be 2.5 ≤ y ≤ 5.0 or 3.0 ≤ y ≤ 4.5. The molar ratio α of Al relative to the total Ln and Mg can be 0.01 ≤ α ≤ 0.45 or 0.10 ≤ α < 0.40.

[0069] When the hydrogen storage alloy contains element M, the molar ratio z of element M to the total of elements Ln and Mg is 0.01≤z≤0.8, preferably 0.1≤z≤0.75.

[0070] Element M preferably contains at least Co, and may also contain Mn. The molar ratio z1 of Co relative to the total of elements Ln and Mg can be, for example, 0.10 ≤ z1 ≤ 0.70 or 0.10 ≤ z1 ≤ 0.60. The molar ratio z2 of Mn relative to the total of elements Ln and Mg can be 0.10 ≤ z2 ≤ 0.50 or 0.20 ≤ z2 ≤ 0.40.

[0071] Hydrogen storage alloys can be of various types, such as AB2, AB3 (CeNi3), AB5 (LaNi5, MmNi5 (Mm represents mixed rare earth metals), A2B7 (Ce2Ni7), and A5B. 19 The anode may contain at least one crystal structure selected from these crystal structures. From the viewpoint of easily obtaining higher high-temperature storage characteristics, the anode may contain a crystal structure selected from AB5 type hydrogen storage alloy, A2B7 type hydrogen storage alloy, and A5B... 19 At least one of the following types of hydrogen storage alloys.

[0072] The hydrogen balance pressure of the hydrogen storage alloy at 45°C can be 0.45 MPa or higher, or 0.73 MPa or higher. From the viewpoint of easily ensuring higher low-temperature discharge characteristics, a hydrogen balance pressure of 0.73 MPa or higher is preferred for the hydrogen storage alloy at 45°C. In this case, excellent discharge performance can be ensured even at extremely low temperatures such as -30°C. The hydrogen balance pressure of the hydrogen storage alloy at 45°C can be 1.82 MPa or lower, or 1.51 MPa or lower. From the viewpoint of obtaining higher high-temperature storage characteristics, a hydrogen balance pressure of 1.51 MPa or lower is preferred for the hydrogen storage alloy at 45°C.

[0073] The hydrogen balance pressure of the hydrogen storage alloy at 45°C can be above 0.45 MPa (or above 0.73 MPa) and below 1.82 MPa, or above 0.45 MPa (or above 0.73 MPa) and below 1.51 MPa.

[0074] As the dispersion medium, known media can be used, such as water, organic media, and mixtures thereof. Examples of organic media include alkanols such as ethanol and isopropanol; aliphatic ketones such as acetone; aliphatic nitriles such as acetonitrile; ethers such as diethyl ether and tetrahydrofuran; and N-methyl-2-pyrrolidone. Although it also depends on the types of other components contained in the negative electrode binder, the dispersion medium preferably contains at least water.

[0075] Examples of adhesives include resin materials (thermoplastic resins, thermosetting resins, etc.), such as rubbery materials like styrene-butadiene copolymer rubber (SBR); polyolefin resins such as polyethylene and polypropylene; fluoropolymers such as PTFE, tetrafluoroethylene copolymers, polychlorotrifluoroethylene, and chlorotrifluoroethylene copolymers (e.g., copolymers with olefins such as ethylene), polyvinylidene fluoride, and vinylidene fluoride copolymers; acrylic resins such as ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-methyl acrylate copolymers, and their Na-ion crosslinks. Adhesives can be used alone or in combination of two or more.

[0076] The amount of binder can be more than 0.01 parts by mass and less than 5 parts by mass, or more than 0.05 parts by mass and less than 2 parts by mass, relative to 100 parts by mass of hydrogen storage alloy powder.

[0077] Various electronically conductive materials can be used as conductive agents. Examples of conductive agents include graphite (natural graphite (flake graphite, etc.), artificial graphite, expanded graphite, etc.), carbon black (acetylene black, Ketjen black, etc.), conductive fibers (carbon fiber, metal fiber, etc.), metal powders (copper powder, etc.), and organic conductive materials (polyphenylene derivatives, etc.). Conductive agents can be used alone or in combination of two or more.

[0078] The amount of conductive agent can be 0.01 parts or more and 5 parts or less, or 0.05 parts or more and 2 parts or less, relative to 100 parts by mass of hydrogen storage alloy powder.

[0079] Conductive agents can be added to the negative electrode mixture and used in combination with other components. Alternatively, conductive agents can be pre-coated onto the surface of the hydrogen storage alloy powder. Coating with conductive agents can be performed using known methods, such as coating the surface of the hydrogen storage alloy powder with the conductive agent, attaching a dispersion containing the conductive agent to the surface of the hydrogen storage alloy powder and allowing it to dry, or mechanically coating using methods such as mechanochemical coating. Furthermore, these coating methods can be combined.

[0080] Thickeners impart viscosity to negative electrode mixtures (slurries or pastes). The type of thickener can be appropriately selected based on factors such as the type of dispersion medium. Examples of thickeners include carboxymethyl cellulose (CMC) and its modified forms (including salts such as Na salts), cellulose derivatives such as methyl cellulose; acrylic resins or their salts containing acrylic or methacrylic acid units, such as polyacrylic acid and polymethacrylic acid; saponifications of polymers containing vinyl acetate units, such as polyvinyl alcohol; and polyepoxides, such as polyethylene oxide. These thickeners can be used alone or in combination of two or more.

[0081] When the dispersion medium contains water, it is preferable to use a component with hydrophilic groups such as carboxyl groups (or their salts), hydroxyl groups, or polyoxyethylene units in the above-mentioned thickener.

[0082] The amount of thickener can be more than 0.01 parts by mass and less than 5 parts by mass, or more than 0.05 parts by mass and less than 1 part by mass, relative to 100 parts by mass of hydrogen storage alloy powder.

[0083] In this application, the Na / Pa ratio and Nb / Pb ratio are set to specific ranges. These ratios can be adjusted, for example, by adjusting the filling amount of the electrode mixture in the first and second parts, or by adjusting the thickness of the electrodes. For example, the thickness of the negative electrode in the first part can be less than the thickness of the negative electrode in the second part. The thickness of the negative electrode in the first part can be the same as the thickness of the negative electrode in the second part. In this case, the Na / Pa ratio and Nb / Pb ratio can be adjusted by adjusting the filling amount of the negative electrode mixture in the first and second parts.

[0084] (positive electrode)

[0085] As the positive electrode, for example, the positive electrode of a known alkaline battery (such as the positive electrode of a known nickel-metal hydride battery).

[0086] The positive electrode can comprise a core material and an active material or active material layer attached thereto. Alternatively, the positive electrode can be obtained by sintering active material powder, or it can be a non-sintered positive electrode.

[0087] The positive electrode can be formed, for example, by attaching a positive electrode mixture (slurry or paste-like positive electrode mixture) containing at least a positive electrode active material to a core material. More specifically, the positive electrode can be formed by coating a core material with a positive electrode mixture, removing the dispersion medium by drying, and then calendering.

[0088] As the positive electrode core material, known core materials can be used. Examples of positive electrode core materials include porous substrates (such as nickel foam, sintered nickel plates, etc.) formed of nickel or nickel alloys. When using a porous substrate as the positive electrode core material, a positive electrode agent is filled into the pores of the positive electrode core material.

[0089] As positive electrode active materials, nickel compounds such as nickel hydroxide and nickel hydroxyl oxide (specifically, nickel oxides) are used. One positive electrode active material can be used alone, or two or more can be used in combination.

[0090] Positive electrode mixtures, whether in slurry or paste form, typically contain a dispersion medium. The dispersion medium can be selected from those exemplified for negative electrode mixtures.

[0091] The positive electrode mixture can be supplemented with known components used in the positive electrode (conductive agent, binder, etc.) as needed.

[0092] Examples of binders include hydrophilic or hydrophobic polymers, and can also be selected from binders and thickeners exemplified for negative electrode binders. A single binder can be used, or two or more can be used in combination. The amount of binder relative to 100 parts by mass of the positive electrode active material can be 0.1 parts by mass or more and 10 parts by mass or less, or 0.5 parts by mass or more and 7 parts by mass or less.

[0093] As a conductive agent, one can select from conductive agents exemplified for negative electrode mixtures, or use conductive cobalt oxides such as cobalt hydroxide or gamma-type cobalt hydroxyoxide. A single conductive agent can be used, or two or more can be used in combination. The amount of conductive agent relative to 100 parts by mass of the positive electrode active material can be 0.1 parts by mass or more and 10 parts by mass or less, or 0.5 parts by mass or more and 5 parts by mass or less.

[0094] Positive electrode mixtures may contain known additives, such as zinc oxide, zinc hydroxide, and other metal compounds (oxides, hydroxides, etc.).

[0095] (spacer)

[0096] There are no particular limitations on the spacer; known spacers used in alkaline batteries (such as nickel-metal hydride batteries) can be used. Examples of spacer shapes include microporous membranes, nonwoven fabrics, and woven fabrics. The spacer can be formed from an insulating material. Examples of spacer materials include polyolefin resins (polyethylene, polypropylene, etc.) and polyamide resins.

[0097] (Alkaline electrolyte)

[0098] As an alkaline electrolyte, an aqueous solution containing an alkaline solute is used, for example. Examples of solutes include alkali metal hydroxides such as lithium hydroxide, potassium hydroxide, and sodium hydroxide. A single solute may be used, or two or more may be used in combination.

[0099] The concentration of alkaline solute in the alkaline electrolyte can be above 3 mol / L and below 10 mol / L, or above 5 mol / L and below 9 mol / L. The specific gravity of the alkaline electrolyte can be above 1.03 and below 1.55, or above 1.11 and below 1.32.

[0100] Figure 1This is a partially exploded perspective view schematically showing the structure of an alkaline battery 10. The alkaline battery 10 includes a battery casing 4, and a wound electrode assembly and an alkaline electrolyte (not shown) housed within the battery casing 4. The battery casing 4 is a bottomed cylindrical casing. The electrode assembly is formed by winding the negative electrode 1, the positive electrode 2, and the spacer 3 into a spiral shape, with a spacer 3 positioned between the negative electrode 1 and the positive electrode 2. The negative electrode 1 contains a hydrogen storage alloy capable of electrochemically absorbing and releasing hydrogen.

[0101] The opening of the battery casing 4 is sealed by a sealing body 7 and an insulating gasket 8. The sealing body 7 contains the positive terminal 5 and a safety valve 6. The positive terminal 2 is electrically connected to the sealing body 7 via a positive current collector 9.

[0102] In the wound electrode assembly, the outermost periphery is the negative electrode 1, and the surface of the negative electrode 1 can be exposed through the spacer 3. The battery casing 4 can be electrically connected to the negative electrode 1. In this case, the battery casing 4 functions as the negative terminal. Through these configurations, current collection performance can be improved.

[0103] In the cylindrical alkaline battery of this application, N2 > N1, and 1.04 ≤ Na / Pa ≤ 1.26 and 1.80 ≤ Nb / Pb ≤ 2.22 are satisfied. This ensures excellent battery characteristics over a wide temperature range. More specifically, it achieves excellent high-temperature storage characteristics while maintaining high low-temperature discharge characteristics of the alkaline battery.

[0104] [Example]

[0105] The cylindrical alkaline storage battery of this application is described in detail below based on embodiments and comparative examples, but this application is not limited to the following embodiments.

[0106] Example 1 and Comparative Example 1

[0107] Make an AA-type cylindrical nickel-metal hydride battery with a rated capacity of 1200mAh according to the following steps.

[0108] (1) Production of the positive electrode

[0109] Fabricate a non-sintered nickel cathode according to the following steps.

[0110] First, nickel hydroxide powder containing 2.5% by mass of zinc and 1.0% by mass of cobalt, as a co-precipitating component, was added to an aqueous solution of cobalt sulfate. While stirring the resulting mixture, an aqueous solution of sodium hydroxide (1 mol / L) was slowly added dropwise to adjust the pH to 11, and stirring was continued for a specified time. The precipitate was filtered from the resulting mixture. The filtered precipitate was washed with water and then vacuum dried to obtain a powder in which nickel hydroxide particles were coated with 5% by mass of cobalt hydroxide.

[0111] To 1 part by weight of the powder obtained above, 10 parts by weight of an aqueous sodium hydroxide solution (sodium hydroxide concentration: 48% by weight) were added. The resulting mixture was heated at 85°C for 8 hours with stirring, then washed with water and dried at 65°C. Through this heat treatment, a portion of the cobalt hydroxide in the cobalt hydroxide-containing layer on the surface of the nickel hydroxide particles was converted to cobalt hydroxyl oxide by high valence, and sodium was introduced. Composite particles with a coating layer containing cobalt hydroxyl oxide and 1% by weight of sodium formed on the surface of the nickel hydroxide particles were obtained.

[0112] A positive electrode slurry is prepared by adding 25 parts by mass of an aqueous solution containing CMC (CMC concentration: 0.2% by mass) as a binder to 100 parts by mass of a mixed powder of 100% by mass of the obtained composite particles and 2% by mass of zinc oxide.

[0113] The obtained positive electrode slurry was filled into nickel foam (area density (weight per unit area) of approximately 360 g / m³) which served as the positive electrode core material. 2 The material is filled into pores (approximately 1.2 mm thick) and dried. The dried material is then rolled to a thickness of 0.5 mm, and then cut to the specified size, thus obtaining a 1200 mAh strip-shaped positive electrode.

[0114] (2) Fabrication of the negative electrode

[0115] A mixture was prepared by mixing 100 parts by weight of hydrogen storage alloy powder, 0.2 parts by weight of carboxymethyl cellulose (thickener), 0.2 parts by weight of Ketjen black (conductive material), and 0.5 parts by weight of styrene-butadiene rubber (binder). The hydrogen storage alloy utilizes La, whose main phase has an AB5-type crystal structure. 0.679 Ce 0.297 Zr 0.024 Ni 4.425 Co 0.146 Mn 0.219 Al 0.398 A hydrogen storage alloy (Alloy F, with a hydrogen balance pressure of 1.12 MPa at 45°C when the hydrogen storage capacity H / M = 0.5) was prepared. Water was added to the resulting mixture and further mixed to prepare a negative electrode paste.

[0116] Next, a negative electrode paste is applied to both sides of the negative electrode current collector to form a coating film. The negative electrode current collector is a perforated iron metal plated with nickel. After the obtained coating film is dried, it is pressed together with the negative electrode current collector to form a negative electrode paste layer. In Comparative Example 1, the negative electrode paste layer is formed with substantially the same filling amount in the entire negative electrode. In Example 1, the filling amount of the negative electrode paste is changed in Part 1 and Part 2 so that the Na / Pa ratio and Nb / Pb ratio are the values ​​shown in Table 1. A strip-shaped negative electrode is thus obtained. In addition, in Example 1 and Comparative Example 1, (Na + Nb) / (Pa + Pb) is equal.

[0117] (3) Manufacturing of nickel-metal hydride batteries

[0118] The fabricated positive and negative electrodes are wound together with a spacer to create a wound body (electrode assembly). The positive and negative electrodes are then overlapped such that N2 > N1, and Na / Pa and Nb / Pb are the values ​​shown in Table 1. The spacer is made of sulfonated polypropylene nonwoven fabric.

[0119] Next, the wound body and alkaline electrolyte are housed in the battery casing. It should be noted that, as the alkaline electrolyte, an aqueous solution containing potassium hydroxide at a concentration of 6.6 mol / L and sodium hydroxide at a concentration of 0.5 mol / L was used.

[0120] Next, the opening of the battery casing is sealed using a gasket and a sealing body. At this point, the porous nickel foam (positive current collector) is electrically connected to the sealing body (positive terminal) via a positive lead. Additionally, the outermost surface of the negative electrode, exposed from the spacer, is electrically connected to the battery casing (negative terminal). Thus, a cylindrical nickel-metal hydride battery is manufactured.

[0121] (4) Activation of nickel-metal hydride batteries

[0122] The fabricated nickel-metal hydride battery was charged at room temperature (25°C) with a charging current of 0.1 It (120 mA) for 16 hours, then stopped for 1 hour. Next, it was discharged at a discharging current of 0.2 It (240 mA) until the termination voltage reached 1.0 V, then stopped for 1 hour. This charge-discharge cycle was repeated 5 times at room temperature (25°C) to activate the nickel-metal hydride battery.

[0123] (5) Evaluation

[0124] (a) High-temperature preservation characteristics

[0125] After activation, nickel-metal hydride batteries are subjected to high-temperature storage tests, and leakage is checked at specified intervals.

[0126] This high-temperature storage test is a test of alternating charging and storage (intermittent charging and storage) of nickel-metal hydride batteries. Specifically, the nickel-metal hydride batteries are charged to 120% of their rated capacity at 0.1 It in an atmosphere at 20°C, and then stored at 105°C for 30 hours. This charging and storage process is repeated alternately during the test period.

[0127] The results are shown in Table 1. In Table 1, E1 represents Example 1 and C1 represents Comparative Example 1.

[0128] [Table 1]

[0129]

[0130] As shown in Table 1, in Example 1, no leakage was detected even after the battery was stored at a high temperature of 105°C for 330 hours. In contrast, in Comparative Example 1, where the Na / Pa ratio and Nb / Pb ratio were the same, leakage was detected after 210 hours of storage. Thus, in examples where N2 > N1 and Na / Pa and Nb / Pb are within specific ranges, the storage time for which leakage was suppressed was very long compared to the comparative examples.

[0131] Example 2 and Comparative Example 2

[0132] Hydrogen storage alloys use an AB5-type crystal structure as the main phase and possess La 0.699 Ce 0.301 Ni 4.404 Co 0.147 Mn 0.356 Al 0.286 A hydrogen storage alloy composed of alloy (Alloy D, with a hydrogen balance pressure of 0.88 MPa at 45°C when the hydrogen storage capacity H / M = 0.5). The Na / Pa ratio and Nb / Pb ratio were adjusted as shown in Tables 2 and 3, respectively, by adjusting the filling amount of the negative electrode paste in Parts 1 and 2, and by adjusting the overlap position of the positive and negative electrodes during electrode assembly. Otherwise, the negative electrode was fabricated in the same manner as in Example 1, and a cylindrical nickel-metal hydride battery was fabricated using the fabricated negative electrode. The nickel-metal hydride battery was activated in the same manner as in Example 1.

[0133] Then, the activated nickel-metal hydride batteries were subjected to the high-temperature storage test described in (a) above, and the low-temperature discharge characteristics described in (b) below were evaluated. It should be noted that in the high-temperature storage test, the case with no leakage at 210 hours of storage time was evaluated as A, and the case with leakage was evaluated as B.

[0134] (b) Low-temperature discharge characteristics

[0135] The activated nickel-metal hydride batteries were charged at 0.1 It (120 mA) for 15 hours at 25°C. After charging, the batteries were left to stand at -20°C for 3 hours and then discharged at 2 It (2400 mA). The discharge time was calculated, and the low-temperature discharge characteristics were evaluated according to the following criteria. It should be noted that the evaluation of the low-temperature discharge characteristics was performed on 5 batteries in each example, and the average value was calculated.

[0136] A: It can discharge for more than 10 minutes.

[0137] B: Discharge time is less than 10 minutes.

[0138] The evaluation results of high-temperature storage characteristics are shown in Table 2, and the evaluation results of low-temperature discharge characteristics are shown in Table 3. In each table, the ratios falling within the ranges of 1.04≤Na / Pa≤1.26 and 1.83≤Nb / Pb≤2.22 are considered examples, and the ratios of at least one of them falling outside the above ranges are considered comparative examples.

[0139] [Table 2]

[0140]

[0141] As shown in Table 2, high high-temperature preservation characteristics were obtained within the range of 1.04 ≤ Na / Pa ≤ 1.26 and 1.83 ≤ Nb / Pb ≤ 2.22 (Example). When at least one of the Na / Pa ratio and Nb / Pb ratio was outside the above range, leakage occurred at an earlier stage compared to the Example, resulting in poor high-temperature preservation characteristics.

[0142] [Table 3]

[0143]

[0144] As shown in Table 3, high low-temperature discharge characteristics can be obtained within the range of 1.04 ≤ Na / Pa ≤ 1.26 and 1.83 ≤ Nb / Pb. In other words, in the embodiments in Table 2 that exhibit excellent high-temperature storage characteristics, high low-temperature discharge characteristics can be ensured.

[0145] Examples 3-11 and Comparative Examples 3-11

[0146] The hydrogen storage alloy used showed the hydrogen balance pressure in Table 4 when the hydrogen storage capacity H / M = 0.5 at 45°C. In addition, the negative electrode was fabricated in the same manner as in Example 1 or Comparative Example 1, and a cylindrical nickel-metal hydride battery was fabricated using the fabricated negative electrode. The nickel-metal hydride battery was activated in the same manner as in Example 1. For the activated nickel-metal hydride battery, a high-temperature storage test was conducted in the same manner as described in (a) above to determine the storage time until leakage suppression was confirmed. The high-temperature storage test was conducted for 330 hours.

[0147] In Table 4, C3 to 11 are Comparative Examples 3 to 11, and E3 to E11 are Examples 3 to 11. The alloy composition of the main phase of each hydrogen storage alloy is also shown in Table 4.

[0148] [Table 4]

[0149]

[0150] As shown in Table 4, even when using alloys with the same hydrogen equilibrium pressure, the examples with specific ranges for Na / Pa ratio and Nb / Pb ratio exhibit longer leakage suppression storage time compared to comparative examples where either the Na / Pa ratio or Nb / Pb ratio is outside the range. From the viewpoint of easily ensuring higher high-temperature storage characteristics, the hydrogen equilibrium pressure of the hydrogen storage alloy at 45°C is preferably 1.51 MPa or less.

[0151] Furthermore, for Examples 3-11 and Comparative Examples 3-11, the low-temperature discharge characteristics were evaluated according to the situation described in (b) above. Specifically, the charged battery was left to stand at -30°C for 3 hours, and then discharged at 2It (2400mA) to determine the discharge time. The results showed that, from the viewpoint of easily ensuring superior low-temperature discharge characteristics, the hydrogen balance pressure at 45°C is preferably 0.73MPa or higher.

[0152] Example 12 and Comparative Example 12

[0153] A negative electrode with a thickness of less than that of the second part is fabricated. At this time, the Na / Pa ratio and Nb / Pb ratio are adjusted as shown in Table 5. Otherwise, the negative electrode is fabricated in the same manner as in Example 1, and a cylindrical nickel-metal hydride battery is fabricated using the fabricated negative electrode. The nickel-metal hydride battery is activated in the same manner as in Example 1.

[0154] Then, the high-temperature storage characteristics described in (a) above were evaluated for the activated nickel-metal hydride batteries. The results are shown in Table 5. In Table 5, E12 is the example and C12 is the comparative example.

[0155] [Table 5]

[0156]

[0157] Even when the thickness of the negative electrode in section 1 is less than that in section 2, high high-temperature storage characteristics (E12) can be obtained as shown in Table 5 by keeping the Na / Pa ratio and Nb / Pb ratio within a specific range. By reducing the thickness of the negative electrode in section 1, the diameter of the electrode assembly can be reduced, thus enabling higher capacity alkaline batteries.

[0158] It should be noted that in the alkaline battery of this application, when comparing the performance of the embodiments and comparative examples, by keeping the ratio of the total capacity Nt of the negative electrode to the total capacity Pt of the positive electrode in the electrode assembly, Nt / Pt, consistent in both embodiments and comparative examples, the superior performance of the battery in the embodiments can be particularly significantly demonstrated. For example, in the above embodiments and comparative examples, the ratio Nt / Pt is 1.701. It should be noted that in the alkaline battery of this application, the above ratio Nt / Pt is not limited to 1.701.

[0159] Industrial availability

[0160] The alkaline battery of this application exhibits excellent battery characteristics over a wide temperature range. Therefore, the alkaline battery possesses high reliability and is suitable as a power source for various devices, in addition to being a replacement for dry cell batteries. However, the applications of alkaline batteries are not limited to this.

[0161] Explanation of reference numerals in the attached figures

[0162] 1: Negative electrode

[0163] 2: Positive electrode

[0164] 3: Spacer

[0165] 4: Battery casing

[0166] 7: Sealing body

[0167] 8: Insulating gaskets

[0168] 9: Positive current collector

[0169] 10: Alkaline batteries

[0170] Part 1

[0171] II: Part 2

[0172] 2a: The outermost part of the positive electrode in the electrode assembly

Claims

1. A cylindrical alkaline storage battery comprising a wound electrode assembly and an alkaline electrolyte, and a cylindrical casing housing them. In the electrode assembly, a negative electrode, a positive electrode, and a spacer between the positive and negative electrodes are wound into a spiral shape. The negative electrode comprises a hydrogen storage alloy capable of electrochemically absorbing and releasing hydrogen. The electrode assembly is divided into a first portion containing the outermost circumference of both the positive and negative electrodes, and a second portion further inward than the first portion. In the electrode assembly, the outermost portion of the negative electrode is located further outward than the outermost portion of the positive electrode. The first part includes: (i) the outermost peripheral portion of the positive electrode; and (ii) The portion from position b1 of the negative electrode opposite to position a1 of the outermost peripheral portion of the positive electrode, which is separated from the spacer by the innermost peripheral side, to the outermost end b2 of the negative electrode. (1) The capacity N1 per unit area of ​​the negative electrode in the first part and the capacity N2 per unit area of ​​the negative electrode in the second part satisfy N2 > N1. (2) The capacity Pa of the positive electrode of the first part as a whole, the capacity Pb ​​of the positive electrode of the second part as a whole, the capacity Na of the negative electrode of the first part as a whole, and the capacity Nb of the negative electrode of the second part as a whole satisfy 1.04≤Na / Pa≤1.26 and 1.80≤Nb / Pb≤2.

22.

2. The cylindrical alkaline storage battery according to claim 1, wherein, The hydrogen storage alloy has a hydrogen equilibrium pressure of 0.73 MPa or higher and 1.51 MPa or lower at 45°C.

3. The cylindrical alkaline storage battery according to claim 1 or 2, wherein, The negative electrode comprises a hydrogen storage alloy selected from AB5 type, A2B7 type, and A5B. 19 At least one of the following types of hydrogen storage alloys.

4. The cylindrical alkaline storage battery according to claim 1 or 2, wherein, The negative electrode in the first part includes a portion that is thinner than the negative electrode in the second part.

5. The cylindrical alkaline storage battery according to claim 1 or 2, wherein, The thickness of the negative electrode in the first part is the same as the thickness of the negative electrode in the second part.

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