阅读说明：本技术 碱性干电池 (Alkaline dry cell ) 是由 高桥康文 樟本靖幸 福井厚史 于 2018-10-29 设计创作，主要内容包括：碱性干电池具备：电池外壳；收纳于电池外壳内的中空圆筒形的正极；配置于正极的中空部内的负极；配置于正极与负极之间的分隔件；和,包含于正极、负极和分隔件中的电解液。在正极与电池外壳的内表面之间具备：包含具有聚氧乙烯基的化合物作为主要成分的层。(The alkaline dry battery comprises: a battery case; a hollow cylindrical positive electrode housed in the battery case; a negative electrode disposed in the hollow portion of the positive electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolytic solution contained in the positive electrode, the negative electrode, and the separator. The battery includes, between a positive electrode and an inner surface of a battery case: a layer containing a compound having a polyoxyethylene group as a main component.)

1. An alkaline dry battery comprising:

a battery case;

a hollow cylindrical positive electrode housed in the battery case;

a negative electrode disposed in the hollow portion of the positive electrode;

a separator disposed between the positive electrode and the negative electrode; and the combination of (a) and (b),

an electrolytic solution contained in the positive electrode, the negative electrode, and the separator,

the battery includes, between the positive electrode and an inner surface of the battery case: a layer containing a compound having a polyoxyethylene group as a main component.

2. The alkaline dry battery according to claim 1, wherein 50% or more of the area of the inner surface of the battery case that contacts the positive electrode is covered with the layer.

3. The alkaline dry battery according to claim 1 or 2, wherein the compound contains at least 1 selected from the group consisting of polyethylene glycol, and a surfactant having the polyoxyethylene group.

4. The alkaline dry battery according to any one of claims 1 to 3, wherein the amount of the compound contained in the layer is 0.5mg/cm²The above.

5. The alkaline dry battery according to any one of claims 1 to 4, wherein the layer further comprises a particulate conductive material.

6. The alkaline dry battery according to any one of claims 1 to 5, wherein the layer further contains 10 parts by mass or more and 80 parts by mass or less of a binder.

7. The alkaline dry battery according to any one of claims 1 to 5, wherein a recess is formed in a surface of the positive electrode facing the battery case.

Technical Field

The present invention relates to improvement of discharge performance of an alkaline dry battery in a low-temperature environment.

Background

Alkaline dry batteries (alkaline manganese dry batteries) have a larger capacity than manganese dry batteries and can take out a large current, and therefore, they are widely used. The alkaline dry battery comprises: a battery case; a hollow cylindrical positive electrode housed in the battery case; a negative electrode disposed in the hollow portion of the positive electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolytic solution contained in the positive electrode, the negative electrode, and the separator. The electrolyte solution uses an aqueous solution of potassium hydroxide or the like, and has good viscosity and ion conductivity at room temperature around 20 ℃.

Patent document 1 discloses the following: a conductive layer is formed on the inner surface of a battery case by using a coating material, which contains 100 parts by mass of a resin having rubber elasticity, 50-100 parts by mass of a plasticizer, 5-50 parts by mass of a crosslinking reagent, and 20-200 parts by mass of a particulate conductive material. Carbon materials are used as the conductive materials. Polyethylene glycol (PEG) and the like are used as the plasticizer. The PEG content in the conductive layer formed using the above coating material is at most about 50 mass%.

Disclosure of Invention

When an alkaline dry battery is discharged in a low-temperature environment, there is a problem that the discharge time becomes very short. The alkaline dry battery described in patent document 1 also has low discharge performance in a low-temperature environment. This is because an aqueous solution of potassium hydroxide or the like used in an electrolytic solution of an alkaline dry battery has good viscosity and ion conductivity in a room temperature environment of around 20 ℃, and conversely, the viscosity is greatly increased and the ion conductivity is reduced in a low temperature environment of 0 ℃. Namely, this is because: in a low-temperature environment, the viscosity of the electrolyte increases greatly, the electrolyte (water) is less likely to circulate to the outer periphery of the positive electrode (battery case side), the outer periphery of the positive electrode cannot be effectively utilized, the polarization of the positive electrode increases during discharge (particularly at the end of discharge), and the discharge ends early.

Further, when the conductive layer covering the inner surface of the battery case contains a carbon material having water repellency, there is also a problem that the electrolyte solution is less likely to circulate to the outer peripheral portion of the positive electrode. The conductive layer described in patent document 1 contains a carbon material and has water repellency because the amount of PEG is small.

One aspect of the present disclosure relates to an alkaline dry battery including: a battery case; a hollow cylindrical positive electrode housed in the battery case; a negative electrode disposed in the hollow portion of the positive electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte solution contained in the positive electrode, the negative electrode, and the separator, wherein a layer containing a compound having a polyoxyethylene group as a main component is provided between the positive electrode and the inner surface of the battery case.

According to the present disclosure, an alkaline dry battery excellent in discharge performance in a low-temperature environment can be provided.

Drawings

Fig. 1 is a front view of an alkaline dry battery in accordance with an embodiment of the present invention, partially in section.

Fig. 2 is a sectional view of a positive electrode pellet having a concave portion on the outer peripheral surface.

Detailed Description

An alkaline dry battery according to an embodiment of the present invention includes: a battery case; a hollow cylindrical positive electrode housed in the battery case; a negative electrode disposed in the hollow portion of the positive electrode; a separator disposed between the positive electrode and the negative electrode; an electrolyte contained in the positive electrode, the negative electrode, and the separator. A layer containing a compound having a polyoxyethylene group (hereinafter, referred to as a hydrophilic material) as a main component is provided between the positive electrode and the inner surface of the battery case. In this specification, a layer containing a hydrophilic material as a main component is referred to as a hydrophilic layer.

By disposing the hydrophilic layer between the positive electrode and the inner surface of the battery case, even when the viscosity of the electrolyte increases in a low-temperature environment, the electrolyte (water) is easily circulated to the outer peripheral portion of the positive electrode (battery case side), and can be effectively used for the outer peripheral portion of the positive electrode during discharge. This improves the discharge performance in a low-temperature environment. In addition, even when a carbon material having water repellency is present between the positive electrode and the inner surface of the battery case, the electrolyte solution easily circulates to the outer peripheral portion of the positive electrode.

The hydrophilic layer contains a hydrophilic material as a main component. The main component here means the content M of the hydrophilic material in the hydrophilic layer_aIs 60% by mass or more. Content M of hydrophilic material_aRefers to the mass ratio of the hydrophilic material in the hydrophilic layer. Content M of hydrophilic material_aPreferably 80% by mass or more, more preferably 90% by mass or more.

The content M of the hydrophilic material in the hydrophilic layer is set to promote circulation of the electrolyte solution to the outer peripheral portion of the positive electrode_bPreferably 0.5mg/cm²Above, more preferably 3mg/cm²The above. The content M of the hydrophilic material_bMeans that the inner surface of the battery case is 1cm per²The quality of the hydrophilic material coated thereon.

Content M of the above hydrophilic material_aAnd content M_bThe measurement can be performed by the following method.

The battery constituent material (positive electrode and the like) housed in the battery case is taken out from the battery case. A layer covering the inner surface of the battery case and the outer peripheral surface of the positive electrode pellet (hereinafter, referred to as a covering layer) was collected. When the boundary between the cover layer and the positive electrode mixture is unclear, a region having a thickness of 500 μm from the inner surface of the battery case or the outermost periphery of the positive electrode pellet is collected as the cover layer. The components of the positive electrode mixture and the electrolyte were removed from the collected cover layer, and a sample was obtained. Measuring mass M of sample₁. Further, the mass M of the hydrophilic material contained in the sample is measured by thermogravimetry/differential thermal analysis (TG/DTA)₂. Will M₂/M₁× 100 as content M_a. The area of the region where the cover layer was collected was defined as an area C₁. Will be provided withM₂/C₁× 100 as content M_b. Liquid chromatography-mass spectrometry (LC/MS) is used to identify the molecular structure of a component (hydrophilic material) contained in a sample.

The distribution state of the hydrophilic material in the battery can be confirmed by the following method or the like.

The cross section of the positive electrode pellet taken out after the battery was disassembled was exposed, and analysis by time of flight secondary ion mass spectrometry (TOF-SIMS) was performed with a region having a thickness of 500 μm from the outermost periphery of the positive electrode pellet as a coating layer. The change in the distribution of the radiation direction was detected as a fragment of polyoxyethylene group as a hydrophilic group.

From the viewpoint of promoting circulation of the electrolytic solution to the outer peripheral portion of the positive electrode, 50% or more of the region of the inner surface of the battery case in contact with the positive electrode is preferably covered with the hydrophilic layer. More preferably, 75% or more of the area of the inner surface of the battery case in contact with the positive electrode is covered with the hydrophilic layer.

The hydrophilic material preferably contains at least 1 selected from the group consisting of polyethylene glycol, and a surfactant having a polyoxyethylene group. Among them, the hydrophilic material more preferably contains polyethylene glycol, because it has excellent hydrophilicity, and is easily applied to the inner surface of the battery case, and a hydrophilic layer is easily formed.

The average molecular weight of the polyethylene glycol is preferably 200 or more and 6000 or less. In the above case, a film of a hydrophilic material can be easily formed on the inner surface of the battery case without using an organic solvent. From the viewpoint of further improving the discharge performance under a low-temperature environment, the average molecular weight of the polyethylene glycol is more preferably 200 or more and 1000 or less.

As the surfactant having a polyoxyethylene group, an organic surfactant may be added between the positive electrode and the battery case. The surfactant is considered to have the following effects: a hydrophilic film is easily formed on the boundary surface between the positive electrode and the battery case, and the back-permeation of the positive electrode during storage and discharge is improved. Preferred surfactants include organic phosphate ester surfactants, polyoxyethylene alkyl ethers, amphoteric surfactants, sulfonated organic acid surfactants, sulfated organic acid surfactants, hexyloxydiphenylsulfonic acid, and combinations of any 2 or more thereof. Among them, nonionic surfactants having a polyoxyethylene group such as polyoxyethylene alkyl ether are more preferable.

The repetition number of the oxyethylene group constituting the polyoxyethylene group as the hydrophilic group of the surfactant is, for example, 5 or more and 136 or less, preferably 9 or more and 100 or less.

From the viewpoint of reducing the internal resistance (contact resistance of the positive electrode and the battery case), the hydrophilic layer preferably further contains a particulate conductive material. In the above case, the hydrophilic layer may be a layer (mixed film) in which a hydrophilic material and a conductive material are mixed. The hydrophilic layer may be composed of a layer (conductive film) containing a conductive material covering the inner surface of the battery case and a layer (hydrophilic film) containing a hydrophilic material formed on the surface of the conductive film. In the case where pores are formed in the conductive film, a part of the hydrophilic film may be incorporated into the pores.

For example, a carbon material is used as the conductive material. In the case of using a carbon material having water repellency, the hydrophilic layer contains a large amount of hydrophilic material, and therefore, the movement of water in the electrolytic solution to the outer peripheral portion of the positive electrode is sufficiently promoted. Examples of the carbon material include graphite and carbon black. From the viewpoint of reducing the internal resistance, the conductive material preferably contains, for example, 60 parts by mass or more and 75 parts by mass or less of graphite and 40 parts by mass or more and 25 parts by mass or less of carbon black. The average particle diameter of the conductive material is, for example, 30nm or more and 100nm or less.

The hydrophilic layer contains at least a hydrophilic material, and may further contain a conductive material and a binder as needed. The hydrophilic layer is formed by applying a predetermined coating material to the inner surface of the battery case, for example. The coating material may contain a conductive material and a solvent as necessary.

The hydrophilic layer may contain 10 parts by mass or more and 80 parts by mass or less of a binder, for example, 15 parts by mass or more and 60 parts by mass or less, from the viewpoint of viscosity adjustment at the time of coating and fixability after coating. As the binder, butadiene acrylonitrile, styrene butadiene, polyvinyl butyral, or the like can be used.

Alternatively, a conductive film may be formed by applying a conductive coating material to the inner surface of the battery case, and a hydrophilic coating material may be applied to the surface of the conductive film to form a hydrophilic film. The conductive coating material contains, for example, a conductive material, a binder, and a solvent.

Preferably, a concave portion is formed on a surface (outer circumferential surface) of the positive electrode facing the battery case. By holding the electrolyte solution by the concave portion formed on the outer peripheral surface of the positive electrode, the utilization rate of the outer peripheral portion of the positive electrode can be further improved, and the discharge performance under a low-temperature environment can be further improved. The recess is preferably formed along the axial direction of the cylindrical positive electrode. In the arrangement, from the viewpoint of preventing the pellet from disintegrating, it is preferable that the plurality of recesses are not formed on the diagonal line in the cross section perpendicular to the axial direction of the cylindrical positive electrode. In addition, from the viewpoint of improving the utilization rate of the positive electrode by retaining the electrolyte, a concave portion may be formed not only on the outer peripheral surface but also on the bottom portion of the pellet.

The alkaline dry battery of the present embodiment will be described in detail below with reference to the drawings. The present invention is not limited to the following embodiments. In addition, the present invention can be modified as appropriate within a range not departing from the scope of the present invention. Further, the present invention can be combined with other embodiments.

Fig. 1 is a front view of an alkaline dry battery according to an embodiment of the present invention, with a cross-sectional view taken along a half-cut. Fig. 1 shows an example of a cylindrical battery having an inside-out type structure. As shown in fig. 1, the alkaline dry battery includes: a hollow cylindrical positive electrode 2; a gel-like negative electrode 3 disposed in the hollow portion of the positive electrode 2; a separator 4 disposed therebetween; and an electrolyte (not shown) contained in the bottomed cylindrical battery case 1 having a positive electrode terminal as well. An alkaline aqueous solution is used for the electrolyte. A hydrophilic layer 10 is formed between the positive electrode 2 and the inner surface of the battery case 1.

The positive electrode 2 is disposed in contact with the inner wall of the battery case 1 through the hydrophilic layer 10. The positive electrode 2 includes manganese dioxide and an electrolyte. The hollow portion of the positive electrode 2 is filled with a gel-like negative electrode 3 through a separator 4. The negative electrode 3 generally contains an electrolyte and a gelling agent in addition to a negative electrode active material containing zinc.

The separator 4 is a bottomed cylindrical shape and contains an electrolytic solution. The separator 4 is composed of a cylindrical separator and a base paper. The separator 4 is disposed along the inner surface of the hollow portion of the positive electrode 2, and separates the positive electrode 2 from the negative electrode 3. Thus, the separator disposed between the positive electrode and the negative electrode is a cylindrical separator. The base paper is disposed at the bottom of the hollow portion of the positive electrode 2, and separates the negative electrode 3 from the battery case 1.

The opening of the battery case 1 is sealed by a sealing unit 9. The sealing unit 9 is composed of a gasket 5, a negative electrode terminal plate 7 serving as a negative electrode terminal, and a negative electrode current collector 6. The negative electrode current collector 6 is inserted into the negative electrode 3. The negative electrode current collector 6 has a nail-like shape having a head portion and a body portion, the body portion is inserted into a through hole provided in the central cylindrical portion of the gasket 5, and the head portion of the negative electrode current collector 6 is welded to a flat portion in the central portion of the negative electrode terminal plate 7. The opening end of the battery case 1 is fastened to the flange of the peripheral edge of the negative electrode terminal plate 7 via the outer peripheral end of the gasket 5. The outer surface of the battery case 1 is covered with an exterior label 8.

The alkaline dry battery will be described in detail below.

(cathode)

Examples of the negative electrode active material include zinc and zinc alloy. The zinc alloy may include at least one selected from the group consisting of indium, bismuth, and aluminum from the viewpoint of corrosion resistance. The zinc alloy contains 0.01 to 0.1 mass% of indium and 0.003 to 0.02 mass% of bismuth, for example. The content of aluminum in the zinc alloy is, for example, 0.001 to 0.03 mass%. From the viewpoint of corrosion resistance, the content of elements other than zinc in the zinc alloy is preferably 0.025 to 0.08 mass%.

The negative electrode active material is usually used in a powdery form. The average particle diameter (D50) of the negative electrode active material powder is, for example, 100 to 200 μm, preferably 110 to 160 μm, from the viewpoint of the filling property of the negative electrode and the diffusibility of the electrolyte in the negative electrode. In the present specification, the average particle diameter (D50) refers to a median particle diameter in a volume-based particle size distribution. The average particle diameter can be determined, for example, by a laser diffraction/scattering particle distribution measuring apparatus.

The negative electrode can be obtained, for example, by mixing a negative electrode active material powder containing zinc, a gelling agent, and an electrolytic solution. As the gelling agent, known gelling agents used in the field of alkaline dry batteries can be used without particular limitation, and for example, water-absorbent polymers and the like can be used. Examples of such gelling agents include polyacrylic acid and sodium polyacrylate. The amount of the gelling agent added is, for example, 0.5 to 2.5 parts by mass per 100 parts by mass of the negative electrode active material.

In the negative electrode, a surfactant such as a polyoxyethylene-group-containing compound or a phosphate ester may be added for adjusting viscosity or the like. Among them, phosphate esters or alkali metal salts thereof are preferable. From the viewpoint of dispersing the surfactant more uniformly in the negative electrode, the surfactant is preferably added to the electrolyte solution used in advance when the negative electrode is produced.

In the negative electrode, a compound containing a metal having a high hydrogen overvoltage such as indium or bismuth may be added as appropriate for improving corrosion resistance. In order to suppress the growth of dendrites such as zinc, a small amount of silicic acid compound such as silicic acid or its potassium salt may be added to the negative electrode as appropriate.

(negative electrode collector)

Examples of the material of the negative electrode current collector inserted into the gel-like negative electrode include metals and alloys. The negative electrode current collector preferably contains copper, and may be made of an alloy containing copper and zinc, such as brass. The negative electrode current collector may be subjected to plating treatment such as tin plating, if necessary.

(Positive electrode)

The positive electrode usually contains a conductive agent and an electrolyte in addition to manganese dioxide as a positive electrode active material. The positive electrode may further contain a binder as necessary.

As manganese dioxide, electrolytic manganese dioxide is preferred. The crystal structure of manganese dioxide includes α -type, β -type, γ -type, η -type, λ -type, and ramsdellite-type.

Manganese dioxide is used in the form of powder. The average particle diameter (D50) of manganese dioxide is, for example, 25 to 60 μm from the viewpoint of ensuring the filling property of the positive electrode and the diffusibility of the electrolyte solution in the positive electrode.

From the viewpoint of formability and suppression of positive electrode swelling, the BET specific surface area of manganese dioxide may be, for example, 20 to 50m²(ii) a range of/g. The BET specific surface area is obtained by measuring and calculating the surface area using the BET formula, which is a theoretical formula for adsorption of a monolayer. The BET specific surface area can be measured, for example, by a specific surface area measuring apparatus based on a nitrogen adsorption method.

Examples of the conductive agent include carbon black such as acetylene black, and conductive carbon materials such as graphite. As the graphite, natural graphite, artificial graphite, or the like can be used. The conductive agent may be in the form of a fiber or the like, and is preferably in the form of a powder. The average particle diameter (D50) of the conductive agent is, for example, 3 to 20 μm.

The content of the conductive agent in the positive electrode is, for example, 3 to 10 parts by mass, preferably 5 to 9 parts by mass, based on 100 parts by mass of manganese dioxide.

The positive electrode can be obtained, for example, as follows: the positive electrode material mixture is obtained by pressure molding a positive electrode material mixture containing a positive electrode active material, a conductive agent, an alkaline electrolyte, and, if necessary, a binder into a pellet form. The positive electrode mixture may be once formed into a sheet or a pellet, classified as necessary, and then press-molded into a pellet form.

After the pellets are contained in the battery case, secondary pressurization can be performed by a predetermined tool so as to be in close contact with the inner wall of the battery case.

(spacer)

Examples of the material of the separator include cellulose and polyvinyl alcohol. The separator may be a nonwoven fabric mainly composed of fibers of the above-mentioned materials, or may be a microporous film such as cellophane or polyolefin film. Nonwoven fabrics may also be used in combination with the microporous film. Examples of the nonwoven fabric include a nonwoven fabric obtained by blending mainly cellulose fibers and polyvinyl alcohol fibers, and a nonwoven fabric obtained by blending mainly rayon fibers and polyvinyl alcohol fibers.

The separator 4 in the bottomed cylindrical shape of fig. 1 is composed of, for example, a cylindrical separator and a base paper. The separator having a bottomed cylindrical shape is not limited to this, and a separator having a known shape used in the field of alkaline dry batteries may be used. The separator may be formed of 1 sheet, and a plurality of sheets may be stacked as long as the sheet constituting the separator is thin. The cylindrical separator may be formed by winding a thin sheet a plurality of times.

The total thickness of the separator is, for example, 200 to 300 μm. The separator preferably has the above-described thickness as a whole, and a plurality of sheets may be stacked to have the above-described thickness as long as the sheet constituting the separator is thin.

(electrolyte)

The electrolyte is contained in the positive electrode, the negative electrode, and the separator. As the electrolytic solution, for example, an alkaline aqueous solution containing potassium hydroxide is used. The concentration of potassium hydroxide in the electrolyte is preferably 30 to 50 mass%. The electrolyte may further contain zinc oxide. The concentration of zinc oxide in the electrolyte is, for example, 1 to 5 mass%.

(Battery case)

For example, a bottomed cylindrical metal case is used as the battery case. For example, a nickel-plated steel plate is used for the metal case.