WO2013132818A1 - アルカリ蓄電池用正極およびそれを用いたアルカリ蓄電池 - Google Patents
アルカリ蓄電池用正極およびそれを用いたアルカリ蓄電池 Download PDFInfo
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- H01M4/24—Electrodes for alkaline accumulators
- H01M4/32—Nickel oxide or hydroxide electrodes
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- H01M2300/00—Electrolytes
- H01M2300/0002—Aqueous electrolytes
- H01M2300/0014—Alkaline electrolytes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a positive electrode for an alkaline storage battery containing nickel oxide and an alkaline storage battery using the same.
- Alkaline storage batteries such as nickel cadmium storage batteries and nickel metal hydride storage batteries are used in various applications because of their high capacity. Particularly in recent years, the use of alkaline storage batteries is also envisaged in applications such as main power sources for electronic devices such as hybrid vehicles and portable devices, and backup power sources such as uninterruptible power supplies. In such applications, charging in a short time or charging in a wide temperature range including high temperatures is required. Therefore, high charging efficiency is required when charging in a wide temperature range.
- Alkaline storage batteries mainly use nickel oxide containing nickel oxyhydroxide and nickel hydroxide as the positive electrode active material. As shown in the following formula, nickel hydroxide is converted into nickel oxyhydroxide during charging, and nickel oxyhydroxide is converted into nickel hydroxide during discharging. In the alkaline storage battery, it has been proposed to use a positive electrode filled with the above-described nickel oxide at a high density from the viewpoint of increasing capacity and output.
- alkaline storage batteries are required to have high charging efficiency in a wide temperature range including high temperatures as their applications expand.
- use in a wide temperature range is assumed, so further improvement in charging efficiency at high temperatures is required.
- An object of the present invention is to provide a positive electrode for an alkaline storage battery capable of obtaining high charging efficiency in a wide temperature range including under high temperature and an alkaline storage battery using the same.
- One aspect of the present invention includes a positive electrode mixture including nickel oxide as a positive electrode active material, a first additive, and a second additive different from the first additive, and the nickel oxide includes The amount of residual sulfate ion SO 4 2- is 0.45% by mass or less, and the first additive is selected from the group consisting of ytterbium, indium, calcium, barium, beryllium, antimony, erbium, thulium, and lutetium.
- Another aspect of the present invention includes the positive electrode, a negative electrode containing a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte.
- the present invention relates to an alkaline storage battery.
- high charge efficiency can be obtained in a wide temperature range including high temperature in an alkaline storage battery. Therefore, it becomes possible to use an alkaline storage battery in a wide temperature range.
- 6 is a graph showing the relationship between the utilization rate of the positive electrode active material and the environmental temperature during charging in the nickel-metal hydride storage batteries A1 to A33 of Examples and Comparative Examples. 6 is a graph showing the relationship between the utilization rate of the positive electrode active material and the environmental temperature during charging in the nickel-metal hydride batteries B1 to B33 of Examples and Comparative Examples. 6 is a graph showing the relationship between the utilization rate of the positive electrode active material and the environmental temperature during charging in the nickel hydride storage batteries C1 to C33 of comparative examples.
- a positive electrode for an alkaline storage battery includes a positive electrode mixture including nickel oxide as a positive electrode active material, a first additive, and a second additive different from the first additive.
- the amount of sulfate ion SO 4 2- remaining in the nickel oxide is 0.45% by mass or less.
- the first additive is a first metal element, specifically, ytterbium (Yb), indium (In), calcium (Ca), barium (Ba), beryllium (Be), antimony (Sb), erbium. It is a compound containing at least one selected from the group consisting of (Er), thulium (Tm), and lutetium (Lu).
- the second additive is composed of a second metal element, specifically, titanium (Ti), vanadium (V), scandium (Sc), niobium (Nb), zirconium (Zr), and zinc (Zn). It is a compound containing at least one selected from the group.
- the positive electrode utilization rate the decrease in the utilization rate of the positive electrode active material (hereinafter also simply referred to as the positive electrode utilization rate) may not be suppressed. It was.
- nickel oxide used as a positive electrode active material in an alkaline storage battery uses a sulfate such as nickel sulfate as a raw material, sulfate ions SO 4 2 ⁇ inevitably remain in the nickel oxide.
- the amount of sulfate ions remaining in the nickel oxide increases, the crystal structure of the nickel oxide becomes unstable, and defects and disturbances in the crystal structure are likely to occur.
- the electrochemical reaction during charge / discharge tends to be non-uniform, and the positive electrode utilization rate tends to decrease.
- the present inventor decreases the utilization rate of the positive electrode even if an additive such as that used in Patent Document 1 or Patent Document 2 is added to the positive electrode mixture. I noticed that there are cases where it can hardly be suppressed. In particular, in a high temperature environment such as 60 ° C., even if an additive is added to the positive electrode mixture using nickel oxide with a large amount of remaining sulfate ions, the effect of the addition may not be obtained. On the other hand, when the remaining amount of sulfate ion is small, the combination of the first additive and the second additive is added to the positive electrode mixture, thereby greatly reducing the positive electrode utilization rate even in a high temperature environment. It was found to be suppressed. That is, it has been clarified that the combination of the first additive and the second additive shows different behavior depending on the remaining amount of sulfate ions in the nickel oxide.
- the first additive and the second additive contained in the positive electrode are dissolved in the electrolytic solution although they are in a small amount.
- the first additive and the second additive form a complex dissolved state in the electrolytic solution.
- the reason why the combination of additives shows different behavior depending on the residual amount of sulfate ions is not clear, but because this complex dissolved state of additives affects the sulfate ions and crystal state in nickel oxide.
- it is considered that the decrease in the positive electrode utilization rate is significantly suppressed even at high temperatures, and high charging efficiency can be obtained.
- Such an effect is a very specific effect, and when the remaining amount of sulfate ion increases, it cannot be obtained by using both the first additive and the second additive, and the remaining amount of sulfate ion At least, it cannot be obtained by only one of the first additive and the second additive.
- alkaline storage batteries such as nickel metal hydride storage batteries may have a large self-discharge.
- Self-discharge tends to become prominent especially at high temperatures.
- Such suppression of self-discharge is hardly obtained even when both the first additive and the second additive are used when the remaining amount of sulfate ions in the nickel oxide increases, and the remaining amount of sulfate ions is small.
- it can hardly be obtained by only one of the first additive and the second additive. It has not been known that the remaining amount of sulfate ions in the nickel oxide and the first and second additives are effective in suppressing self-discharge.
- the positive electrode for an alkaline storage battery includes a conductive support (or a core material) and a positive electrode mixture attached to the support.
- a support body the well-known electroconductive support body used for the positive electrode of an alkaline storage battery can be used.
- the conductive support may be a three-dimensional porous body, or may be a flat plate or a sheet. Examples of the material for the support include nickel and nickel alloys.
- the positive electrode mixture includes nickel oxide as a positive electrode active material, a first additive, and a second additive.
- the nickel oxide as the positive electrode active material mainly contains nickel oxyhydroxide and / or nickel hydroxide.
- the nickel oxide can be obtained by mixing a nickel sulfate aqueous solution and a metal hydroxide aqueous solution. By mixing these aqueous solutions, particles containing nickel oxide are precipitated in the mixed solution.
- a complexing agent may be added to the mixed solution or the nickel sulfate aqueous solution. The complexing agent may be added as an aqueous solution.
- the precipitated nickel oxide may be further washed with an aqueous solution of metal hydroxide. By performing such cleaning, the remaining amount of sulfate ions in the nickel oxide can be reduced, and other impurities contained in the nickel oxide can be removed.
- the amount of sulfate ions remaining in the nickel oxide used as the positive electrode active material is 0.45 mass% or less.
- the residual amount of sulfate ions in the nickel oxide is desirably 0.42% by mass or less, and preferably 0.4% by mass or less.
- the crystallinity of the nickel oxide is improved.
- the crystallinity of the nickel oxide can be confirmed based on the crystallinity of the (001) plane. Charge acceptability can be improved by improving the crystallinity of nickel oxide.
- the residual amount of sulfate ions in the nickel oxide is 0.25% by mass or less or 0.2% by mass or less, the crystallinity of the nickel oxide is easily improved, and the utilization rate of the positive electrode is increased.
- the residual amount of sulfate ions is preferably as small as possible, it is difficult to reduce the residual amount of sulfate ions to 0% by mass. Therefore, for example, the residual amount of sulfate ions may be 0.01% by mass or more.
- the amount of sulfate ions remaining in the nickel oxide exceeds 0.45% by mass, even if the first additive and / or the second additive is added to the positive electrode mixture, the effect of the addition is almost obtained.
- the decrease in the utilization rate of the positive electrode is particularly remarkable at high temperatures.
- the self-discharge during battery storage increases.
- the remaining amount of sulfate ions in the nickel oxide is determined by mixing the concentration of each aqueous solution, the concentration of the aqueous solution containing the complexing agent, the nickel sulfate, and the metal hydroxide when the nickel sulfate aqueous solution and the metal hydroxide aqueous solution are mixed. It can be controlled by adjusting the mixing ratio of the complexing agent, the temperature of the mixed solution, the concentration and temperature of the aqueous solution of metal hydroxide used for washing, and the like.
- the concentration of nickel sulfate contained in nickel sulfate aqueous solution for example, it is selected from the range of 1 ⁇ 5mol / dm 3, is preferably 1.5 ⁇ 4mol / dm 3 or 2 ⁇ 3mol / dm 3,.
- the metal hydroxide used as a raw material examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
- concentration of the metal hydroxide contained in the metal hydroxide aqueous solution used as the raw material can be selected from the range of 2 to 12 mol / dm 3 , for example, 3 to 10 mol / dm 3 , or 4 to 8 mol / dm 3 . Preferably there is.
- the metal hydroxide is used in such a ratio that the stoichiometric ratio of nickel sulfate to the hydroxide ion capable of forming the metal hydroxide is 1: 2 (molar ratio). . Since it is preferable that the hydroxide ion is in a small excess of 2 times the molar amount of nickel in nickel sulfate, it may be, for example, 2.1 mol or more with respect to 1 mol of nickel. The upper limit of the hydroxide ion is not particularly limited, but may be 3 mol or less, or 2.5 mol or less with respect to 1 mol of nickel.
- a base can be used as the complexing agent, and among them, an inorganic base such as ammonia is preferable.
- the complexing agent can be used, for example, in a ratio of 1.8 to 3 mol, or in a ratio of 2 to 3 mol, with respect to 1 mol of nickel in nickel sulfate. preferable.
- each aqueous solution and complex-forming agent are adjusted so that the molar ratio is as described above.
- Supply amount is adjusted.
- the temperature of the mixed solution can be selected from the range of 30 to 65 ° C., for example, and is preferably 40 to 60 ° C. or 45 to 55 ° C.
- Examples of the metal hydroxide used for washing include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
- the same metal hydroxide as the raw material may be used for cleaning.
- the concentration of the metal hydroxide contained in the metal hydroxide aqueous solution used for washing can be selected from the range of 2 to 15 mol / dm 3 , for example, 3 to 12 mol / dm 3 , or 4 to 10 mol / dm 3 . Preferably there is.
- the temperature of the aqueous metal hydroxide solution used for washing can be selected from the range of 30 to 65 ° C., for example, and is preferably 40 to 60 ° C. or 45 to 55 ° C.
- the average particle diameter of the obtained particles containing nickel oxide is, for example, 3 to 25 ⁇ m.
- the nickel oxide may contain a metal element (third metal element) incorporated in the crystal structure of the nickel oxide. That is, the nickel oxide may be a solid solution containing a third metal element.
- the third metal element examples include alkaline earth metal elements such as magnesium and calcium, transition metal elements (for example, Group 9 elements of the periodic table such as cobalt; Group 12 elements of the periodic table such as zinc and cadmium), and the like. It is done. These 3rd metal elements can be used individually by 1 type or in combination of 2 or more types. Of these third metal elements, at least one selected from the group consisting of magnesium, cobalt, cadmium and zinc is preferable. In particular, the third metal element preferably contains cobalt and at least one selected from the group consisting of magnesium, cadmium and zinc, and more preferably contains cobalt and zinc.
- the charging efficiency can be further increased, and the positive electrode utilization rate can be more effectively improved. In particular, even when charged at a high temperature, high charging efficiency can be obtained. In addition, the effect of suppressing self-discharge during storage is enhanced.
- the amount of the third metal element in the total amount of nickel and the third metal element contained in the nickel oxide is, for example, 0.1 to 10% by mass, preferably 0.5 to 6% by mass, and more preferably 0.7%. Is 4% by mass. In such a range, the effect of the combination of the nickel oxide in which the remaining amount of sulfate ions is reduced and the third metal element is easily obtained.
- nickel oxide contains 2 or more types of 3rd metal elements
- the quantity of each 3rd metal element can be adjusted so that the sum total of 2 or more types of 3rd metal elements may become said amount. .
- the third metal element can be introduced into the crystal structure of the nickel oxide by coexisting the third metal element when mixing the nickel sulfate aqueous solution and the metal hydroxide aqueous solution. Specifically, by adding an inorganic acid salt of a third metal element (such as an inorganic strong acid salt such as sulfate) to a nickel sulfate aqueous solution and a metal hydroxide aqueous solution, the third metal element is mixed. Nickel oxide contained in the crystal structure can be obtained.
- a third metal element such as an inorganic strong acid salt such as sulfate
- the positive electrode mixture contains nickel oxide as a main component.
- the amount of nickel oxide in the positive electrode mixture is, for example, 60% by mass or more, and preferably 70% by mass or more.
- the amount of nickel oxide in the positive electrode mixture may be 75% by mass or more or 80% by mass or more.
- the first additive is a compound containing at least one first metal element selected from the group consisting of Yb, In, Ca, Ba, Be, Sb, Er, Tm, and Lu. Unlike the case of the third metal element, the positive electrode mixture contains such a first metal element in a compound state.
- the first additive has a function of increasing an oxygen generation overvoltage at a high temperature.
- the compound containing 1 type of 1st metal elements or the compound containing 2 or more types of 1st metal elements may be used, and these compounds may be used in combination of 2 or more types.
- Examples of the compound as the first additive include oxides, hydroxides, fluorides (CaF 2 and the like), inorganic acid salts (sulfates and the like), and the like. These compounds can be used individually by 1 type or in combination of 2 or more types.
- the oxides and hydroxides may be peroxides. Of these, oxides and hydroxides are preferred.
- examples of the oxide include Yb 2 O 3 , In 2 O 3 , BeO, Sb 2 O 3 , Er 2 O 3 , Tm 2 O 3 , and Lu 2 O 3.
- examples of the hydroxide include Ca (OH) 2 and Ba (OH) 2 .
- Yb 2 O 3 , In 2 O 3 , Ca (OH) 2 , Ba (OH) 2 , BeO, Sb 2 O 3 , Er 2 O 3 , Tm 2 O 3 , and Lu 2 O 3 It is preferable to use at least one selected from the group consisting of When such a compound is used, the effect of the combination with the second additive and nickel oxide in which the remaining amount of sulfate ions is controlled is easily obtained.
- the second additive is a compound containing at least one second metal element selected from the group consisting of Ti, V, Sc, Nb, Zr, and Zn. Unlike the case of the third metal element, the positive electrode mixture contains such a second metal element in the state of a compound.
- the second additive has an auxiliary function for more effectively exerting the function of the first additive.
- a compound containing one kind of second metal element or a compound containing two or more kinds of second metal elements may be used, or two or more of these compounds may be used in combination.
- Examples of the compound that is the second additive include oxides, hydroxides, fluorides, inorganic acid salts (such as sulfates), and the like. These compounds can be used individually by 1 type or in combination of 2 or more types.
- the oxides and hydroxides may be peroxides. Of these, oxides and hydroxides are preferable, and oxides are particularly preferable.
- the second additive it is preferable to use at least one selected from the group consisting of TiO 2 , V 2 O 5 , Sc 2 O 3 , Nb 2 O 5 , ZrO 2 , and ZnO.
- TiO 2 vanadium oxide
- V 2 O 5 vanadium oxide
- Sc 2 O 3 niobium oxide
- Nb 2 O 5 niobium oxide
- ZrO 2 zirconium oxide
- ZnO zirconium oxide
- the total amount of the first additive and the second additive is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 0.7 parts by mass with respect to 100 parts by mass of the nickel oxide. More than part by mass.
- the amount of the first additive and the second additive is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the nickel oxide. is there. These lower limit values and upper limit values can be arbitrarily combined.
- the total amount of the first additive and the second additive relative to 100 parts by mass of the nickel oxide may be, for example, 0.1 to 5 parts by mass, or 0.5 to 3 parts by mass.
- the mass ratio of the first additive to the second additive can be selected, for example, from a range of 1: 0.2 to 5, and is 1: 0.3 to 3, or 1: 0.5 to 2. preferable.
- the mass ratio is in such a range, the effect of combining both additives is easily obtained. Therefore, high charging efficiency is easily obtained even at high temperatures, and self-discharge can be effectively suppressed.
- the positive electrode mixture may further contain a conductive agent.
- the conductive agent may be added to the positive electrode mixture by mixing with other components of the positive electrode mixture (positive electrode active material, first and second additives, etc.).
- the surface of nickel oxide particles as a positive electrode active material may be coated with a conductive agent, and the coated particles may be used as a positive electrode mixture.
- the conductive agent examples include simple metals, alloys, conductive metal oxides, and conductive metal hydroxides.
- the type of metal contained in these conductive agents is not particularly limited, but it is preferable to use a material containing at least cobalt as the conductive agent.
- Examples of such a conductive agent include metallic cobalt, cobalt oxide (CoO, Co 2 O 3 , Co 3 O 4 etc.), cobalt hydroxide (cobalt hydroxide, ⁇ -type cobalt oxyhydroxide etc.) and the like. it can.
- These electrically conductive agents can be used individually by 1 type or in combination of 2 or more types. For example, metallic cobalt and cobalt oxide and / or cobalt hydroxide may be used in combination.
- the surface of the nickel oxide particles is coated with a conductive agent
- cobalt oxyhydroxide is particularly ⁇ -type.
- the amount of the conductive agent can be selected, for example, from the range of 1 to 20 parts by mass with respect to 100 parts by mass of the nickel oxide, and is preferably 2 to 15 parts by mass.
- the amount of the conductive agent is 3 to 20 parts by mass or 5 to 15 parts by mass with respect to 100 parts by mass of the nickel oxide. Is preferred.
- the amount of the conductive agent is preferably 2 to 10 parts by mass, or 3 to 7 parts by mass with respect to 100 parts by mass of the nickel oxide. .
- the conductive layer can be formed by a known method depending on the type of the conductive agent.
- a conductive layer containing a metal oxide such as cobalt oxide has a metal hydroxide such as cobalt hydroxide attached to the surface of particles containing nickel oxide, and (b) an alkali metal hydroxide. It can be formed by converting a metal hydroxide into a metal oxide such as ⁇ -type cobalt oxyhydroxide by a heat treatment in the presence of.
- a metal hydroxide such as cobalt hydroxide
- Objects can be attached to the surface of the particles.
- inorganic acid salts include strong inorganic acid salts such as sulfates. You may add the said complex formation agent, such as ammonia, to the aqueous solution containing a metal inorganic acid salt.
- the particles containing nickel oxide having a metal hydroxide such as cobalt hydroxide adhered to the surface are further heated in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide.
- an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide.
- metal hydroxide such as cobalt hydroxide on the particle surface is converted into oxide such as ⁇ -type cobalt oxyhydroxide, and a conductive layer having high conductivity is formed on the particle surface.
- the positive electrode is formed, for example, by applying a positive electrode mixture paste containing a positive electrode active material, a first additive, a second additive, a dispersion medium, and the like to a support, removing the dispersion medium by drying, and rolling. it can. Depending on the shape of the support and the like, the positive electrode mixture paste may be applied to the support or filled in the pores of the support.
- the positive electrode mixture paste can be prepared by mixing the positive electrode active material, the first additive, the second additive, and the dispersion medium.
- the dispersion medium known media such as water, organic media, and mixed media thereof can be used.
- a conductive agent, a binder, a thickener, etc. may be added to the positive electrode mixture paste as necessary, but these (particularly, a binder, a thickener) need not necessarily be added. Absent.
- binder examples include resin materials such as rubber-like materials such as styrene-butadiene copolymer rubber (SBR); polyolefin resins such as polyethylene and polypropylene; polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene. Fluoropolymers such as copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers; acrylic resins such as ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl acrylate copolymers; The Na ion crosslinked body etc. can be illustrated.
- resin materials such as rubber-like materials such as styrene-butadiene copolymer rubber (SBR); polyolefin resins such as polyethylene and polypropylene; polytetrafluoroethylene, polyvinylidene fluoride, tetraflu
- binders can be used individually by 1 type or in combination of 2 or more types.
- the amount of the binder is, for example, 7 parts by mass or less, and may be 0.01 to 5 parts by mass or 0.05 to 2 parts by mass with respect to 100 parts by mass of the active material.
- the thickener examples include carboxymethylcellulose (CMC) and modified products thereof (including salts such as Na salt), cellulose derivatives such as methylcellulose; saponified polymers having vinyl acetate units such as polyvinyl alcohol; polyethylene oxide, etc. And polyalkylene oxide. These thickeners can be used singly or in combination of two or more.
- the amount of the thickener is, for example, 5 parts by mass or less, and may be 0.01 to 3 parts by mass or 0.05 to 1.5 parts by mass with respect to 100 parts by mass of the active material.
- an alkaline storage battery includes the positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte.
- the configuration of the alkaline storage battery will be described below with reference to FIG.
- FIG. 1 is a longitudinal sectional view schematically showing the structure of an alkaline storage battery according to an embodiment of the present invention.
- the alkaline storage battery includes a bottomed cylindrical battery case 4 also serving as a negative electrode terminal, an electrode group housed in the battery case 4 and an alkaline electrolyte (not shown). In the electrode group, the negative electrode 1, the positive electrode 2, and the separator 3 interposed therebetween are spirally wound.
- a sealing plate 7 having a positive electrode terminal 5 and a safety valve 6 is disposed in the opening of the battery case 4 via an insulating gasket 8, and the alkaline storage battery is sealed by caulking the opening end of the battery case 4 inward. Has been.
- the sealing plate 7 is electrically connected to the positive electrode 2 through the positive electrode current collector plate 9.
- an electrode group is accommodated in a battery case 4, an alkaline electrolyte is injected, a sealing plate 7 is disposed in an opening of the battery case 4 via an insulating gasket 8, and the battery case 4 Can be obtained by caulking and sealing.
- the negative electrode 1 of the electrode group is electrically connected by contacting the battery case 4 at the outermost periphery.
- the positive electrode 2 of the electrode group and the sealing plate 7 are electrically connected via a positive electrode current collector plate 9.
- alkaline storage batteries examples include nickel metal hydride storage batteries, nickel cadmium storage batteries, and nickel zinc storage batteries.
- the positive electrode since the positive electrode is used, the self-discharge can be effectively suppressed even in the nickel-metal hydride storage battery having a large self-discharge.
- a negative electrode As a negative electrode, a well-known thing can be used according to the kind of alkaline storage battery.
- a nickel metal hydride storage battery for example, a negative electrode containing a hydrogen storage alloy powder capable of electrochemically storing and releasing hydrogen can be used as a negative electrode active material.
- a nickel cadmium storage battery for example, a negative electrode containing a cadmium compound such as cadmium hydroxide can be used as a negative electrode active material.
- the negative electrode may include a support (or a core material) and a negative electrode active material attached to the support.
- a support body A well-known thing can be used as a support body, and the porous or non-porous board
- the active material may be filled in the pores of the support.
- the negative electrode can be formed by attaching a negative electrode mixture paste containing at least a negative electrode active material to a support. Specifically, the negative electrode can be formed by applying a negative electrode mixture paste to a support, removing the dispersion medium by drying, and rolling in accordance with the case of the positive electrode.
- the negative electrode mixture paste usually contains a dispersion medium, and a known component used for the negative electrode, for example, a conductive agent, a binder, a thickener, and the like may be added as necessary.
- a dispersion medium, the binder, and the thickening agent are the same as those exemplified for the positive electrode.
- the amount of the binder and the thickener can be appropriately selected from the ranges exemplified for the positive electrode.
- the conductive agent is not particularly limited as long as it is a material having electronic conductivity.
- graphite such as natural graphite (flaky graphite etc.), artificial graphite and expanded graphite; carbon black such as acetylene black and ketjen black; conductive fibers such as carbon fiber and metal fiber; metal particles such as copper powder
- An organic conductive material such as a polyphenylene derivative can be exemplified.
- These conductive agents may be used alone or in combination of two or more. Of these, artificial graphite, ketjen black, carbon fiber and the like are preferable.
- the amount of the conductive agent is, for example, 0.01 to 20 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the active material.
- the conductive agent may be added to the negative electrode mixture paste and mixed with other components. Further, the surface of the negative electrode active material particles may be previously coated with a conductive agent.
- the conductive agent is coated by a known method, for example, by coating the surface of the negative electrode active material particles with a conductive agent, attaching a dispersion containing the conductive agent to dry, or mechanically coating the conductive agent by a mechanochemical method or the like. It can be done by doing.
- Alkaline electrolyte For example, an aqueous solution containing an alkaline electrolyte is used as the alkaline electrolyte.
- alkaline electrolyte examples include alkali metal hydroxides such as lithium hydroxide, potassium hydroxide, and sodium hydroxide. These can be used individually by 1 type or in combination of 2 or more types.
- the alkaline electrolyte preferably contains at least sodium hydroxide. Moreover, you may use together sodium hydroxide and at least 1 type selected from the group which consists of potassium hydroxide and lithium hydroxide as an alkali contained in an alkaline electrolyte.
- the concentration of sodium hydroxide contained in the alkaline electrolyte is, for example, 2.5 to 11.5 mol / dm 3 , preferably 3 to 11 mol / dm 3 , more preferably 3.5 to 10.5 mol / dm 3 , 4 to 10 mol / dm 3 .
- concentration of sodium hydroxide is in such a range, the charging efficiency can be more effectively increased even when charging at a high temperature, and self-discharge can be more effectively suppressed. Further, it is advantageous from the viewpoint that the cycle life can be improved by suppressing the discharge average voltage from decreasing while maintaining high charging efficiency.
- the total concentration of potassium hydroxide and lithium hydroxide contained in the alkaline electrolyte can be selected from the range of, for example, 5 to 40 g / dm 3 , 10 to 30 g / dm 3 , or 15 to 25 g / dm 3. It is preferable that The specific gravity of the alkaline electrolyte is, for example, 1.1 to 1.6, preferably 1.2 to 1.5.
- a separator In addition to the separator and the battery case, as other components, known components used for alkaline storage batteries, such as a microporous film, a nonwoven fabric, and a laminate of these, can be used.
- the material for the microporous membrane and the nonwoven fabric include polyolefin resins such as polyethylene and polypropylene; fluororesins; polyamide resins. From the viewpoint of high decomposition resistance to an alkaline electrolyte, it is preferable to use a separator made of polyolefin resin.
- hydrophilic group it is preferable to introduce a hydrophilic group into a separator formed of a highly hydrophobic material such as a polyolefin resin by a hydrophilic treatment.
- the hydrophilic treatment include corona discharge treatment, plasma treatment, and sulfonation treatment.
- a sulfonated separator that is, a separator having a sulfonic acid group (such as a polyolefin separator).
- Example 1 Preparation of nickel oxide Cobalt sulfate and zinc sulfate were added to a nickel sulfate aqueous solution with a concentration of 2.5 mol / dm 3 , and the amount of cobalt and zinc in the total amount of nickel, cobalt and zinc was 1.5% by mass, respectively. It added so that it might become.
- the temperature of the liquid mixture at this time was 50 degreeC.
- the precipitated nickel oxide is filtered off and washed with an aqueous sodium hydroxide solution having a temperature of 50 ° C. and a concentration of 2.5 mol / dm 3 to remove impurities such as sulfate ions contained in the nickel oxide, and then washed with water.
- the nickel oxide (a) was obtained by drying.
- the obtained nickel oxide was spherical particles having an average particle diameter of about 10 ⁇ m.
- the amount of sulfate ion SO 4 2- remaining in the nickel oxide was 0.2% by mass.
- Residual sulfate ion SO was changed in the same manner as above except that the concentration of each aqueous solution as a raw material and the mass ratio at the time of mixing, the temperature of the mixed solution, and the temperature and concentration of the sodium hydroxide aqueous solution used for washing were appropriately changed.
- the obtained positive electrode mixture paste was filled in a foamed nickel porous body (porosity 95%, surface density 300 g / cm 2 ) as a support, dried, pressed, and then given dimensions (thickness: 0.00).
- the positive electrodes A1 to A33 were produced by cutting into 5 mm, length: 110 mm, and width: 35 mm.
- the positive electrodes A1 to A33 have the composition Nos.
- the first additive and the second additive corresponding to each of 1 to 33 are included.
- the filling amount of the positive electrode mixture paste and the degree of pressurization were adjusted so that the theoretical capacity of the positive electrode was 1,000 mAh when nickel oxide was charged and discharged to perform a one-electron reaction.
- An exposed portion of the support was provided at one end along the longitudinal direction of the positive electrode.
- positive electrodes B1 to B33 and positive electrodes C1 to C33 were produced in the same manner as described above except that nickel oxide (b) or (c) was used instead of nickel oxide (a).
- composition No. which does not contain both the first additive and the second additive.
- composition No. including only one of the first additive and the second additive are comparative examples.
- Positive electrodes C1 to C33 using nickel oxide in which the amount of remaining sulfate ions is 0.6% by mass are also comparative examples.
- a negative electrode mixture paste was prepared by mixing 0.7 parts by mass of a styrene-butadiene copolymer as an agent, adding water to the obtained mixture, and further mixing.
- the negative electrode mixture paste was applied to both surfaces of a nickel-plated iron punching metal (thickness 30 ⁇ m) as a support to form a coating film. After drying the obtained coating film, it pressed with the support body and cut to predetermined size (thickness: 0.3 mm, length: 134 mm, width: 36 mm), and produced the hydrogen storage alloy negative electrode. The capacity of the negative electrode was adjusted to 1600 mAh. An exposed portion of the support was provided at one end portion along the longitudinal direction of the negative electrode (end end portion of the electrode group).
- an alkaline storage battery (nickel metal hydride battery) having the structure shown in FIG. 1 was prepared. More specifically, first, an electrode group was formed by winding these layers in a spiral shape with the separator 3 interposed between the positive electrode 2 and the negative electrode 1. As the separator 3, a sulfonated polypropylene separator was used.
- the positive electrode current collector plate 9 was welded to the exposed portion of the support formed on the positive electrode 2, and the sealing plate 7 and the positive electrode current collector plate 9 were made conductive through the positive electrode lead.
- the electrode group was housed in a battery case 4 that also serves as a bottomed cylindrical negative electrode terminal, and the outermost periphery of the negative electrode 3 and the inner wall of the battery case 4 were brought into contact with each other to electrically connect them.
- the outer periphery in the vicinity of the opening of the battery case 4 was recessed to provide a groove, and 2.0 cm 3 of alkaline electrolyte was injected into the battery case 4.
- alkaline electrolyte lithium hydroxide dissolved in a sodium hydroxide aqueous solution having a specific gravity of 1.3 so as to have a concentration of 20 g / dm 3 was used.
- a sealing plate 7 provided with a positive electrode terminal 5 and a safety valve 6 was attached to the opening of the battery case 4 through an insulating gasket 8.
- an AA size sealed nickel metal hydride storage battery A1 having a theoretical capacity of 1000 mAh with the positive electrode regulating the battery capacity was produced. .
- Nickel-metal hydride batteries A2 to A33, B1 to B33, and C1 to C33 were produced in the same manner as described above except that the positive electrodes A2 to A33, B1 to B33, and C1 to C33 were used instead of the positive electrode A1.
- the nickel metal hydride storage battery was activated by charge / discharge (temperature: 20 ° C., charging condition: 100 mA for 16 hours, discharging condition: 200 mA for 5 hours), and then subjected to the following evaluation.
- the nickel metal hydride storage battery obtained in (4) above is subjected to a charge / discharge test as follows to determine the utilization rate (positive electrode utilization rate) of nickel oxide as the positive electrode active material. It was.
- the positive electrode utilization rate is an indicator of charging characteristics.
- a nickel metal hydride storage battery was charged at an environmental temperature of 20 ° C. for 16 hours at a charging rate of 0.1 It, and then left at an environmental temperature of 25 ° C. for 3 hours, and then the environmental temperature of 20 ° C. Was discharged to 1.0 V at a discharge rate of 0.2 It. Such charge and discharge was repeated for 2 cycles, and the discharge capacity at the second cycle was determined. Based on the obtained discharge capacity, the positive electrode utilization rate was determined by the following formula.
- Positive electrode utilization rate (%) discharge capacity (mAh) / 1000 (mAh) ⁇ 100 Moreover, also when the environmental temperature at the time of charge was changed into 45 degreeC or 60 degreeC, it carried out similarly to the above, and calculated
- FIG. 2 shows the relationship between the positive electrode utilization rate in the batteries A1 to A33 and the environmental temperature during charging
- FIG. 3 shows the relationship between the positive electrode utilization rate and the environmental temperature during charging in the batteries B1 to B33.
- FIG. 4 shows the relationship between the positive electrode utilization rate and the environmental temperature during charging in the batteries C1 to C33.
- batteries of comparative examples containing only one of the first additive and the second additive (Battery A of Composition Nos. 1, 2, 7, 8, 13, 14, 19, 20, and 26 to 33)
- a high positive electrode utilization rate can be maintained at 20 ° C. and 45 ° C.
- the positive electrode utilization rate rapidly decreases, and only a positive electrode utilization rate of about 70% can be obtained.
- the comparative batteries (batteries A25 and B25) that do not contain either the first additive or the second additive, a high positive electrode utilization rate exceeding 90% is obtained at 20 ° C., but as the temperature increases. At 60 ° C., only a positive electrode utilization rate of 60% can be obtained.
- the battery C25 to which the first additive and the second additive are not added is about 70% at 40 ° C. Only the positive electrode utilization rate was obtained, and at 60 ° C., it was less than 50%. In addition, when either one of the first additive and the second additive was added, a positive electrode utilization rate exceeding 80% was obtained at 45 ° C., but decreased to nearly 50% at 60 ° C. (battery C1 C2, C7, C8, C13, C14, C19, C20, and C26 to C33). Further, even when both the first additive and the second additive were added, the positive electrode utilization rate at 60 ° C. decreased to nearly 60% (batteries C3 to C6, C9 to C12, C15 to C18, and C21 to C24).
- both the first additive and the second additive were added to the batteries of group A and B in which the amount of remaining sulfate ions was 0.2% by mass and 0.4% by mass.
- a high capacity remaining rate of 85% or more was obtained even after storage at 45 ° C. for 2 weeks. That is, it can be seen that in the battery of the example, self-discharge during storage is suppressed and high storage characteristics can be obtained.
- batteries of comparative examples containing only one of the first additive and the second additive (Battery A of Composition Nos. 1, 2, 7, 8, 13, 14, 19, 20, and 26 to 33) And B), the capacity remaining rate is low, only about 80%. Further, even in the comparative batteries A25 and B25 which did not contain either the first additive or the second additive, the capacity remaining rate was about 80%.
- the capacity remaining rate is almost the same between the case where the first additive and the second additive are not added, the case where one of the additives is added, and the case where both the additives are added. Absent. That is, when the amount of remaining sulfate ions is large, the effect of adding the additive is hardly obtained. However, when the amount of remaining sulfate ions is small, the effect of using both the first additive and the second additive is very remarkable, and a high capacity remaining rate can be maintained even after storage at high temperatures. it can.
- a compound containing Be, Sb, Er, Tm, and / or Lu BeO, Sb 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Lu 2 O 3, etc.
- BeO, Sb 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Lu 2 O 3, etc. was used as the first additive. Even in this case, the same effect as described above has been confirmed. Even when a compound containing Zn and / or Zr (ZnO, ZrO 2 or the like) is used as the second additive, the same effect as described above has been confirmed.
- the positive electrode of the present invention When the positive electrode of the present invention is used for an alkaline storage battery, high charging efficiency can be obtained even if the battery is charged in a wide temperature range including high temperatures. Moreover, the self-discharge of a battery can also be suppressed effectively. Therefore, the alkaline storage battery using the positive electrode is useful as a power source for various electronic devices, transportation devices, power storage devices and the like, and is also suitable for use as a power source for electric vehicles and hybrid vehicles.
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Abstract
Description
さらに、高温での充電効率を向上する目的で、Ni(OH)2結晶中に含まれる硫酸根(SO4 2-の量)を0.4重量%以下にすることも提案されている(特許文献3参照)。
特許文献1や特許文献2で使用される添加剤は、充電時の正極の酸素過電圧を向上させる効果があるため、このような添加剤を使用すると、正極における酸素の発生をある程度抑制できると考えられる。しかし、60℃などの高温下では、添加剤を正極合剤に添加しても、正極活物質の利用率(以下、単に、正極利用率とも言う)の低下を抑制できない場合があることが分かった。
(正極)
本発明の一実施形態に係るアルカリ蓄電池用正極は、より具体的には、導電性の支持体(または芯材)と、支持体に付着した正極合剤とを含む。
(支持体)
支持体としては、アルカリ蓄電池の正極に使用される公知の導電性の支持体が使用できる。導電性支持体は、3次元多孔体であってもよく、平板またはシートであってもよい。
支持体の材質としては、ニッケル、ニッケル合金などが挙げられる。
正極合剤は、正極活物質としてのニッケル酸化物と、第1添加剤と、第2添加剤とを含む。
(正極活物質)
正極活物質としてのニッケル酸化物は、主に、オキシ水酸化ニッケルおよび/または水酸化ニッケルを含む。
ニッケル酸化物は、硫酸ニッケル水溶液と、金属水酸化物の水溶液とを混合することにより得ることができる。これらの水溶液の混合により、ニッケル酸化物を含む粒子が混合液中で析出する。このとき、ニッケルイオンなどの金属イオンを安定化させるため、混合液や、硫酸ニッケル水溶液などに、錯形成剤を添加してもよい。錯形成剤は水溶液として添加してもよい。
原料として使用される金属水酸化物水溶液に含まれる金属水酸化物の濃度は、例えば、2~12mol/dm3の範囲から選択でき、3~10mol/dm3、または4~8mol/dm3であることが好ましい。
錯形成剤は、硫酸ニッケル中のニッケル1モルに対して、例えば、1.8~3モルとなるような割合で使用することができ、2~3モルとなるような割合で使用することが好ましい。
混合液の温度は、例えば、30~65℃の範囲から選択でき、40~60℃、または45~55℃であることが好ましい。
洗浄に使用される金属水酸化物水溶液に含まれる金属水酸化物の濃度は、例えば、2~15mol/dm3の範囲から選択でき、3~12mol/dm3、または4~10mol/dm3であることが好ましい。
なお、ニッケル酸化物は、ニッケル酸化物の結晶構造に組み込まれた金属元素(第3金属元素)を含んでいてもよい。すなわち、ニッケル酸化物は、第3金属元素を含む固溶体でもよい。
第1添加剤は、Yb、In、Ca、Ba、Be、Sb、Er、Tm、およびLuからなる群より選択される少なくとも一種の第1金属元素を含む化合物である。正極合剤は、このような第1金属元素を、上記第3金属元素の場合とは異なり、化合物の状態で含有する。第1添加剤は、高温時の酸素発生過電圧を上昇させる機能を有する。
第1添加剤としては、一種の第1金属元素を含む化合物または二種以上の第1金属元素を含む化合物を使用してもよく、これらの化合物を二種以上組み合わせて使用してもよい。
第1添加剤として、Yb2O3、In2O3、Ca(OH)2、Ba(OH)2、BeO、Sb2O3、Er2O3、Tm2O3、およびLu2O3からなる群より選択される少なくとも一種を用いることが好ましい。このような化合物を用いると、第2添加剤および硫酸イオンの残存量が制御されたニッケル酸化物との組み合わせによる効果が得られやすい。
第2添加剤は、Ti、V、Sc、Nb、Zr、およびZnからなる群より選択される少なくとも一種の第2金属元素を含む化合物である。正極合剤は、このような第2金属元素を、上記第3金属元素の場合とは異なり、化合物の状態で含有する。第2添加剤は、第1添加剤の機能をより効果的に発揮させる助剤的な機能を有する。
第2添加剤としては、一種の第2金属元素を含む化合物または二種以上の第2金属元素を含む化合物を使用してもよく、これらの化合物を二種以上組み合わせて使用してもよい。
正極合剤は、さらに導電剤を含んでもよい。導電剤は、正極合剤の他の構成成分(正極活物質、第1および第2添加剤など)とともに混合することにより正極合剤に添加してもよい。また、正極活物質としてのニッケル酸化物の粒子の表面を導電剤で被覆し、この被覆粒子を正極合剤に使用してもよい。
例えば、(a)コバルト酸化物などの金属酸化物を含む導電層は、水酸化コバルトなどの金属水酸化物を、ニッケル酸化物を含む粒子の表面に付着させ、(b)アルカリ金属水酸化物の存在下での加熱処理などにより、金属水酸化物を、γ型のオキシ水酸化コバルトなどの金属酸化物に変換することにより形成できる。
結着剤の量は、活物質100質量部に対して、例えば、7質量部以下であり、0.01~5質量部または0.05~2質量部であってもよい。
増粘剤の量は、活物質100質量部に対して、例えば、5質量部以下であり、0.01~3質量部または0.05~1.5質量部であってもよい。
本発明の他の一局面によれば、アルカリ蓄電池は、上記の正極と、負極と、正極および負極の間に介在するセパレータと、アルカリ電解液とを具備する。
アルカリ蓄電池の構成を、図1を参照しながら以下に説明する。図1は、本発明の一実施形態に係るアルカリ蓄電池の構造を模式的に示す縦断面図である。
(負極)
負極としては、アルカリ蓄電池の種類に応じて、公知のものが使用できる。ニッケル水素蓄電池では、例えば、負極活物質として、水素を電気化学的に吸蔵および放出可能な水素吸蔵合金粉末を含む負極が使用できる。ニッケルカドミウム蓄電池では、例えば、負極活物質として、水酸化カドミウムなどのカドミウム化合物を含む負極が使用できる。
支持体としては、公知のものが使用でき、ステンレス鋼、ニッケルまたはその合金などで形成された多孔性または無孔の基板が例示できる。支持体が多孔性基板の場合、活物質は、支持体の空孔に充填されていてもよい。
導電剤の量は、活物質100質量部に対して、例えば、0.01~20質量部、好ましくは0.1~10質量部、さらに好ましくは0.1~5質量部である。
アルカリ電解液としては、例えば、アルカリ電解質を含む水溶液が使用される。アルカリ電解質としては、水酸化リチウム、水酸化カリウム、水酸化ナトリウムなどのアルカリ金属水酸化物が例示できる。これらは、一種を単独でまたは二種以上を組み合わせて使用できる。
アルカリ電解液は、少なくとも水酸化ナトリウムを含むことが好ましい。また、アルカリ電解液に含まれるアルカリとして、水酸化ナトリウムと、水酸化カリウムおよび水酸化リチウムからなる群より選択される少なくとも一種とを併用してもよい。
アルカリ電解液の比重は、例えば、1.1~1.6、好ましくは1.2~1.5である。
セパレータ、電池ケースの他、他の構成要素としては、アルカリ蓄電池に使用される公知のもの、例えば、微多孔膜、不織布、これらの積層体などが使用できる。微多孔膜や不織布の材質としては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂;フッ素樹脂;ポリアミド樹脂などが例示できる。アルカリ電解液に対する耐分解性が高い点からは、ポリオレフィン樹脂製のセパレータを用いることが好ましい。
(1)ニッケル酸化物の作製
濃度2.5mol/dm3の硫酸ニッケル水溶液に、硫酸コバルトおよび硫酸亜鉛を、ニッケル、コバルトおよび亜鉛の総量に占めるコバルトおよび亜鉛の量がそれぞれ1.5質量%となるように添加した。得られた水溶液と、濃度5.5mol/dm3の水酸化ナトリウム水溶液と、濃度5.0mol/dm3のアンモニア水溶液とを、所定の質量比で混合し、主に水酸化ニッケルを含み、CoおよびZnが固溶したニッケル酸化物を析出させた。このときの混合液の温度は50℃であった。
正極活物質としての上記(1)で得られたニッケル酸化物(a)と、導電剤としてのコバルト粉末と、導電剤としての水酸化コバルト粉末と、表1に示す第1添加剤および第2添加剤とを、100:7:5:X:Yの質量比で混合し、さらに所定量の水を加えて練合することにより、正極合剤ペーストを調製した。
水素吸蔵合金としてMmNi3.6Co0.7Mn0.4Al0.3100質量部、増粘剤としてのカルボシキメチルセルロース0.15質量部、導電剤としてのカーボンブラック0.3質量部および結着剤としてのスチレンブタジエン共重合体0.7質量部を混合し、得られた混合物に水を添加してさらに混合することにより、負極合剤ペーストを調製した。
上記(2)で得られた正極A1および(3)で得られた負極を用いて、図1に示す構造を有するアルカリ蓄電池(ニッケル水素蓄電池)を作製した。
より詳細には、まず、正極2と、負極1との間に、セパレータ3を介在させた状態で、これらを重ねて渦巻き状に巻回することにより、電極群を形成した。セパレータ3としては、スルホン化されたポリプロピレン製のセパレータを用いた。
なお、ニッケル水素蓄電池は、充放電(温度:20℃、充電条件:100mAで16時間、放電条件:200mAで5時間)することにより活性化させた後、以下の評価に供した。
上記(4)で得られたニッケル水素蓄電池について、次のようにして充放電試験を行い、正極活物質であるニッケル酸化物の利用率(正極利用率)を求めた。正極利用率は、充電特性の指標となる。
また、充電時の環境温度を、45℃または60℃に変更した場合についても、上記と同様にして、各充電温度での正極利用率を求めた。
電池A1~A33における正極利用率と充電時の環境温度との関係を図2に、電池B1~B33における正極利用率と充電時の環境温度との関係を図3に、それぞれ示す。また、電池C1~C33における正極利用率と充電時の環境温度との関係を図4に示す。
上記(4)で得られたニッケル水素蓄電池を、20℃にて、0.1Itの充電率で16時間充電した。充電したニッケル水素蓄電池を、45℃の環境温度下で、2週間保存した。保存前後のニッケル水素蓄電池を、20℃にて、0.2Itの放電率で1.0Vまで放電し、このときの放電容量(mAh)を求めた。
得られた放電容量を元に、次式により、保存後のニッケル水素蓄電池の容量残存率を求め、自己放電の指標とした。
容量残存率(%)=(保存後の放電容量)(mAh)/(保存前の放電容量)(mAh)×100
図2および図3に示すように、残存する硫酸イオンの量が0.2質量%および0.4質量%であるAおよびBのグループの電池において、第1添加剤および第2添加剤の双方を添加した実施例の電池では、20℃および45℃では90%以上の高い正極利用率が得られている。また、実施例の電池では、温度が60℃の場合でも、80%以上の高い正極利用率を維持できている。これらのことから、実施例では、充電効率が改善されていることが分かる。
次に、各ニッケル水素蓄電池における容量残存率を表2に示す。
しかし、残存する硫酸イオンの量が少ない場合には、第1添加剤および第2添加剤の双方を用いることによる効果が極めて顕著に現れ、高温で保存後も高い容量残存率を維持することができる。
2 正極
3 セパレータ
4 電池ケース
5 正極端子
6 安全弁
7 封口板
8 絶縁ガスケット
9 正極集電板
Claims (11)
- 正極活物質としてのニッケル酸化物と、第1添加剤と、前記第1添加剤とは異なる第2添加剤とを含む正極合剤を含み、
前記ニッケル酸化物中に残存する硫酸イオンSO4 2-の量が、0.45質量%以下であり、
前記第1添加剤が、イッテルビウム、インジウム、カルシウム、バリウム、ベリリウム、アンチモン、エルビウム、ツリウム、およびルテチウムからなる群より選択される少なくとも一種を含む化合物であり、
前記第2添加剤が、チタン、バナジウム、スカンジウム、ニオブ、ジルコニウム、および亜鉛からなる群より選択される少なくとも一種を含む化合物である、アルカリ蓄電池用正極。 - 前記正極合剤に占める前記ニッケル酸化物の量が70質量%以上である、請求項1に記載のアルカリ蓄電池用正極。
- 前記ニッケル酸化物中に残存する硫酸イオンSO4 2-の量が、0.4質量%以下である、請求項1または2に記載のアルカリ蓄電池用正極。
- 前記第1添加剤が水酸化物または酸化物であり、
前記第2添加剤が水酸化物または酸化物である、請求項1~3のいずれか1項に記載のアルカリ蓄電池用正極。 - 前記第1添加剤が、Yb2O3、In2O3、Ca(OH)2、Ba(OH)2、BeO、Sb2O3、Er2O3、Tm2O3、およびLu2O3からなる群より選択される少なくとも一種である、請求項1~4のいずれか1項に記載のアルカリ蓄電池用正極。
- 前記第2添加剤が、TiO2、V2O5、Sc2O3、Nb2O5、ZrO2、およびZnOからなる群より選択される少なくとも一種である、請求項1~5のいずれか1項に記載のアルカリ蓄電池用正極。
- 前記ニッケル酸化物100質量部に対して、前記第1添加剤および前記第2添加剤の量は、合計で、0.1~5質量部であり、
前記第1添加剤と前記第2添加剤の質量比は1:0.2~5である、請求項1~6のいずれか1項に記載のアルカリ蓄電池用正極。 - 前記正極合剤は、さらに導電剤を含む請求項1~7のいずれか1項に記載のアルカリ蓄電池用正極。
- 前記導電剤が、金属コバルト、コバルト酸化物およびコバルト水酸化物からなる群より選択される少なくとも一種である、請求項8に記載のアルカリ蓄電池用正極。
- 前記ニッケル酸化物が、前記ニッケル酸化物の結晶構造に組み込まれた第3金属元素を含み、
前記第3金属元素が、マグネシウム、コバルト、カドミウムおよび亜鉛からなる群より選択される少なくとも一種であり、
前記ニッケル酸化物に含まれるニッケルおよび前記第3金属元素の総量に占める前記第3金属元素の量が0.1~10質量%である、請求項1~9のいずれか1項に記載のアルカリ蓄電池用正極。 - 請求項1~10のいずれか1項に記載の正極と、電気化学的に水素を吸蔵および放出可能な水素吸蔵合金を含む負極と、前記正極および前記負極の間に介在するセパレータと、アルカリ電解液とを具備する、アルカリ蓄電池。
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