Aqueous secondary battery

Abstract

This zinc / zinc sulfate / manganese oxide aqueous secondary battery uses a zinc alloy that contains indium (In) and bismuth (Bi) as a negative electrode active material and can thereby suppress generation of hydrogen gas.

Description

water-based secondary battery

[0001] The present invention relates to aqueous secondary batteries, and more particularly to zinc / zinc sulfate / manganese oxide aqueous secondary batteries.

[0002] Renewable energy emits CO ２ However, power generation systems that use natural energy sources such as solar and wind power generation are subject to large fluctuations in output due to factors such as weather.

[0003] Therefore, in order to stabilize the power supply from a power generation system that uses natural energy and use it as a main power source, it is necessary to store the unused electricity in a storage battery when the amount of power generated exceeds demand, and to release the electricity stored in the storage battery to make up for the shortfall when the amount of power generated falls short of demand.

[0004] These storage batteries that complement power generation systems that utilize natural energy will be large-scale, so they must not only have excellent battery capacity and cycle characteristics, but also be highly safe and inexpensive. Zinc, which has abundant reserves and a stable supply, is attracting attention as a material for next-generation batteries to replace lithium.

[0005] Non-Patent Document 1 describes a battery with a water-based electrolyte and high safety guaranteed, in which metallic zinc (Zn) is used for the negative electrode, zinc sulfate aqueous solution for the electrolyte, and manganese oxide (MnO ２ The paper describes a zinc / zinc sulfate / manganese oxide aqueous secondary battery using a single-walled carbon nanotube (SWCNT) and describes that by inserting a three-dimensional network of single-walled carbon nanotubes into the positive and negative electrodes of this aqueous secondary battery, the electrochemical performance can be improved, and the capacity retention rate and cycle characteristics can be enhanced, making it promising for application to long-term energy storage.

[0006] Electrochemistry of rechargeable aqueous zinc / zinc-sulfate / manganese-oxide batteries and methods for preparation of high-performance cathodes; Wei Gong, Bunshi Fugetsu, Wei Mao, Adavan Kilyankil Vipin, Ichiro Sakata, Lei Su, Xueji Zhang & Morinobu Endo (Journal of Materials Chemistry A (Issue 29 2022))

[0007] However, in the aqueous secondary battery described in Non-Patent Document 1, hydrogen gas is generated from the negative electrode during charging and discharging, which causes the container of a sealed battery to swell, making it difficult to stack the batteries to increase their size.

[0008] The present invention has been made in view of the problems associated with the prior art, and an object of the present invention is to provide a zinc / zinc sulfate / manganese oxide aqueous secondary battery in which generation of hydrogen gas is suppressed.

[0009] As a result of extensive research into achieving the above object, the inventors have found that the above object can be achieved by using a zinc alloy containing indium (In) and bismuth (Bi) as a negative electrode active material, and have thus completed the present invention.

[0010] That is, the above-mentioned problems of the present invention are solved by the following (1) and (2): (1) Manganese dioxide (MnO ２ (2) The aqueous secondary battery according to (1), characterized in that the electrolyte has a pH of 4.2 to 4.8, and the zinc alloy contains 0.05 to 0.12 wt % of indium (In) and 0.05 to 0.12 wt % of bismuth (Bi).

[0011] According to the present invention, a zinc alloy containing indium (In) and bismuth (Bi) is used as the negative electrode active material, so that a water-based zinc-manganese secondary battery can be provided in which the hydrogen overvoltage of the negative electrode is increased and the generation of hydrogen gas is suppressed.

[0012] The aqueous secondary battery of the present invention will be described in detail. The aqueous secondary battery of the present invention is a battery containing manganese dioxide (MnO ２ The aqueous zinc / zinc sulfate / manganese oxide secondary battery (hereinafter referred to as "aqueous zinc-manganese secondary battery") includes a positive electrode containing zinc sulfate and single-walled carbon nanotubes, an electrolyte containing an aqueous zinc sulfate solution, and a negative electrode containing a zinc alloy containing indium (In) and bismuth (Bi).

[0013] (Negative Electrode) The negative electrode can be composed of a current collector and a negative electrode active material layer formed on the surface of the current collector.

[0014] The negative electrode active material is a zinc alloy containing indium (In) and bismuth (Bi). When the negative electrode active material is a Zn—In—Bi alloy, generation of hydrogen gas from the negative electrode can be suppressed.

[0015] Zinc (Zn) is a metal that has a greater tendency to ionize than hydrogen, and dissolves in dilute sulfuric acid, generating hydrogen.

[0016] Conventionally, in alkaline manganese batteries, in order to suppress the generation of hydrogen gas from the negative electrode using zinc, mercury, which has a high hydrogen overvoltage, is added to the battery.

[0017] However, the likelihood of the hydrogen gas generation reaction occurring at the negative electrode varies depending on the pH of the electrolyte, and the hydrogen overvoltage required to suppress the generation of hydrogen gas is higher in an acidic electrolyte than in an alkaline electrolyte.

[0018] In the present invention, a zinc alloy containing indium (In) and bismuth (Bi) is used as the negative electrode active material, so that the hydrogen overvoltage at the negative electrode can be increased and hydrogen generation in an acidic environment can be suppressed.

[0019] The contents of indium (In) and bismuth (Bi) in the zinc alloy vary depending on the pH of the electrolyte, but it is preferable that indium (In) is 0.05 to 0.12 wt % and bismuth (Bi) is 0.05 to 0.12 wt %.

[0020] When the content of In and Bi in the zinc alloy is within the above range, generation of hydrogen gas in the acidic electrolyte can be prevented.

[0021] Furthermore, the zinc alloy may contain, in addition to In and Bi, other metals with high hydrogen overvoltage, such as lead (Pb), tin (Sn), and mercury (Hg), and the total content of these metals is preferably 0.1 wt% or less.

[0022] The negative electrode active material can be produced by an atomization method in which a molten metal obtained by adding predetermined amounts of additive metals such as indium and bismuth to metallic zinc is sprayed and cooled.

[0023] The negative electrode can be produced by mixing the negative electrode active material with a binder and a conductive additive, adding a dispersion medium to form a slurry of the negative electrode mixture, applying the slurry to the surface of the current collector, and drying the slurry to form a negative electrode active material layer.

[0024] The binder may be polyvinylidene fluoride, the dispersion medium may be N-methylpyrrolidone, and the negative electrode current collector may be made of SUS.

[0025] (Positive Electrode) The positive electrode can be composed of a current collector and a positive electrode active material layer formed on the surface of the current collector.

[0026] The positive electrode active material is manganese dioxide (MnO ２ Manganese oxide is an oxide that is abundant and inexpensive, but manganese dioxide (MnO ２ ) has poor conductivity and limited electrochemical properties.

[0027] Generally, a composite is used that is made by mixing manganese dioxide particles with carbon-based conductive particles such as carbon black and a binder, but because this is not a nano-level composite, it is not possible to eliminate resistance between particles or the resistance of the binder.

[0028] The positive electrode active material layer of the present invention contains single-wall carbon nanotubes (SWCNTs) as carbon-based conductive particles, and manganese dioxide and the SWCNTs are bonded together without the intervention of a binder.

[0029] Therefore, the conductive paths of the carbonaceous conductive particles are lengthened, reducing the resistance between particles, and the resistance of the binder is eliminated, thereby improving the battery performance.

[0030] The positive electrode active material layer can be formed by electrolytically depositing manganese dioxide on SWCNTs coated on a current collector. The positive electrode current collector can be made of SUS, the same as the negative electrode current collector.

[0031] (Electrolyte) Zinc sulfate (ZnSO ４ ) and manganese sulfate (MnSO ４ ) is used.

[0032] The pH of the electrolyte is preferably 4.2 to 4.8. ４ and MnSO ４ In an electrolyte solution containing ２ SO ４ Add H ＋ By increasing the concentration of , the average discharge voltage of the battery can be increased.

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0034] Example 1 (Fabrication of Positive Electrode) Single-walled carbon nanotubes were dispersed in N-methyl-2-pyrrolidone containing a polymer dispersant (polyvinylpyrrolidone) to obtain a dispersion of single-walled carbon nanotubes (SWCNT).

[0035] This dispersion was dip-coated onto a stainless steel foil, dried at 60°C, and the dispersant and dispersion medium were removed with ethanol. Manganese dioxide was then precipitated on the SWCNT network formed on the surface of the stainless steel foil to obtain a positive electrode.

[0036] (Preparation of Negative Electrode) 90 parts by mass of Zn—In—Bi alloy powder containing 0.1 wt % each of In and Bi, 0.5 parts by mass of single-walled carbon nanotubes, 5 parts by mass of polyvinylidene fluoride (Solef5130 manufactured by Solvey), and N-methylpyrrolidone were mixed, kneaded, and dispersed, and the mixture was passed through a 100-mesh sieve to prepare a negative electrode slurry with a solid content of 27.6%.

[0037] The negative electrode slurry was applied to a current collector foil (SUS400) and dried at 100° C. for 15 minutes to obtain a negative electrode.

[0038] (Fabrication of Battery) A laminate obtained by sandwiching a separator (paper using glass fiber) between the prepared positive electrode and negative electrode was housed in a laminate film, and a 2M ZnSO ４ and 0.1 M MnSO ４ An aqueous electrolyte solution (pH 4.5) containing the above was poured into the battery, and the battery was sealed to obtain an aqueous zinc-manganese secondary battery.

[0039] Comparative Example 1 A water-based zinc-manganese secondary battery was obtained in the same manner as in Example 1, except that the Zn—In—Bi alloy powder in the negative electrode slurry was changed to pure Zn powder.

[0040] <Evaluation> The aqueous zinc-manganese secondary batteries of Example 1 and Comparative Example 1 were charged and discharged at 0.1 C (25° C.) to measure the amount of hydrogen gas generated. The measurement results are shown in Table 1.

[0041] 〇: No gas generation (no expansion of laminate exterior) ×: Gas generation (expansion of laminate exterior)

[0042] From the results in Table 1, it was confirmed that the generation of hydrogen gas was suppressed in Example 1, in which the negative electrode active material was a Zn—In—Bi alloy.

Claims

1. Manganese dioxide (MnO ２ a positive electrode containing zinc alloy containing indium (In) and bismuth (Bi); an electrolyte containing an aqueous zinc sulfate solution; and a negative electrode containing a zinc alloy containing indium (In) and bismuth (Bi).

2. The aqueous secondary battery according to claim 1, characterized in that the pH of the electrolyte is 4.2 to 4.8, and the zinc alloy contains 0.05 to 0.12 wt% indium (In) and 0.05 to 0.12 wt% bismuth (Bi).

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