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WO2022134541A1 - 正极材料及其制备方法以及电化学装置 - Google Patents

正极材料及其制备方法以及电化学装置 Download PDF

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Publication number
WO2022134541A1
WO2022134541A1 PCT/CN2021/105205 CN2021105205W WO2022134541A1 WO 2022134541 A1 WO2022134541 A1 WO 2022134541A1 CN 2021105205 W CN2021105205 W CN 2021105205W WO 2022134541 A1 WO2022134541 A1 WO 2022134541A1
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Prior art keywords
positive electrode
lithium
electrode material
electrochemical device
crystal structure
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PCT/CN2021/105205
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English (en)
French (fr)
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吴霞
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宁德新能源科技有限公司
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Publication of WO2022134541A1 publication Critical patent/WO2022134541A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, and in particular, to a positive electrode material, a preparation method thereof, and an electrochemical device.
  • Electrochemical devices such as lithium-ion batteries
  • LiCoO 2 cathode material which has an R-3m phase structure and a theoretical capacity of 273.8mAh/g. It has good cycle and safety performance, high compaction density and simple preparation process. . Since its commercialization by Sony in 1991, LiCoO 2 cathode materials have dominated the lithium-ion battery materials market. In order to obtain higher specific energy, LiCoO 2 is developing towards high voltage (>4.6Vvs.Li/Li + ). However, when LiCoO 2 is charged to 4.5V, the capacity can only reach 190mAh/g.
  • metal cations such as Al, Mg, Ti, Zn, and Ni are generally used in the industry and scientific research community for bulk doping to improve the structural stability of R-3m phase LiCoO 2 .
  • the doping of most elements improves the structural stability of the material by delaying the irreversible phase transition, but the effect of this method on the structure stability is not obvious at voltages higher than 4.6V.
  • the doping amount increases, the theoretical capacity loss will increase. Therefore, there is an urgent need to find a cathode material for lithium-ion batteries with high specific capacity, high voltage platform, good structural reversibility, and interface stability at high voltage.
  • the purpose of the present application is to provide a positive electrode material, which has good interface stability, high capacity and cycle stability.
  • the present application provides a composite positive electrode material, including lithium cobalt oxide with a P6 3 mc crystal structure and lithium manganese oxide with a C2/m crystal structure; in the XRD pattern of the positive electrode material, it is located at 17°
  • the characteristic peak intensity in the range of -19° is I A
  • the characteristic peak intensity in the range of 19°-22° is I B , 0.1 ⁇ IB / IA ⁇ 0.5 .
  • the average particle diameter D1 of the lithium cobalt oxide having the P6 3 mc crystal structure and the average particle diameter D2 of the lithium manganese oxide having the C2/m crystal structure satisfy: 0.1 ⁇ D2/D1 ⁇ 0.5.
  • the average particle size D1 is 5 ⁇ m to 30 ⁇ m; the average particle size D2 is 1 ⁇ m to 5 ⁇ m.
  • the lithium cobalt oxide includes Li and Co elements and optionally includes at least one of M element or Na element, wherein M element includes Al, Mg, Ti, Mn, Fe, Ni, Zn, At least one of Cu, Nb, Cr, Y or Zr; the sum of the molar content of Co and M elements is n Co+M , the molar content of Li element is n Li , and the ratio x of n Li to n Co+M is 0.6 ⁇ x ⁇ 0.95, the molar content of M element is n M , the ratio of n M to n Co+M y is 0 ⁇ y ⁇ 0.15, the molar content of Na element is n Na , the ratio of n Na to n Co+M z is 0 ⁇ z ⁇ 0.03.
  • M element includes Al, Mg, Ti, Mn, Fe, Ni, Zn, At least one of Cu, Nb, Cr, Y or Zr
  • the sum of the molar content of Co and M elements is n Co+M
  • the lithium cobalt oxide includes Li x Na z Co 1-y My O 2 , 0.6 ⁇ x ⁇ 0.95, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03, and M includes Al, Mg, Ti, At least one of Mn, Fe, Ni, Zn, Cu, Nb, Cr, Y, and Zr.
  • the lithium manganese oxide includes Li 2 ⁇ h Mn 1-g T g O k , 0 ⁇ h ⁇ 1, 0 ⁇ g ⁇ 0.5, 0 ⁇ k ⁇ 5, T includes Ti, Sn, Ru, At least one of Ni, Co and Al.
  • the present application further provides an electrochemical device including a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, and the positive electrode sheet includes the positive electrode material of the present application.
  • the electrolyte includes a carboxylate.
  • the carboxylates include at least one of the following: pentasodium diethylenetriaminepentaacetate, sodium nitrilotriacetate, sodium edetate, sodium gluconate.
  • the mass percentage content of the carboxylate is 0.01% to 0.15% based on the mass of the electrolyte.
  • the cathode material provided by the present application has good interface stability, high capacity characteristics and cycle stability.
  • the "average particle size” means that the material powder is photographed and observed by a SEM scanning electron microscope, and then, 10 material particles are randomly selected from the SEM photograph using image analysis software, and these The respective areas of the material particles, and then, assuming that the material particles are spherical, the respective particle diameters R (diameter) are obtained by the following formula:
  • R 2 ⁇ (S/ ⁇ ) 1/2 ; wherein, S is the area of the material particle;
  • the process of obtaining the particle diameter R of the material particles was performed on 10 SEM images, and the particle diameters of the obtained 100 (10 ⁇ 10) material particles were arithmetically averaged to obtain the average particle diameter of the material particles.
  • the positive electrode material of the present application the preparation method thereof, and the electrochemical device of the present application will be described in detail below.
  • the cathode material of the present application includes lithium cobalt oxide with a P6 3 mc crystal structure and lithium manganese oxide with a C2/m crystal structure; in the XRD pattern of the cathode material, it is located in the range of 17°-19°
  • the peak intensity of the characteristic peak (P6 3 mc structure peak) within 19°-22° is I A
  • the characteristic peak intensity (C2/m peak) in the range of 19°-22° is I B , 0.1 ⁇ IB / IA ⁇ 0.5 .
  • Lithium cobalt oxide with P6 3 mc crystal structure has a stable oxygen structure, is not easy to release oxygen at high voltage, has a stable structure, and thus has good cycle performance. In addition, it has lithium ion accepting ability, which can absorb additional lithium ions.
  • the theoretical capacity (>300mAh/g) of lithium manganese oxide with C2/m crystal structure is higher than that of P6 3 mc cathode material.
  • the lithium cobalt oxides of mc are compounded together, which can well combine the advantages of the two materials and solve their respective shortcomings.
  • the characteristic peak intensity (P63mc structure peak) in the range of 17°-19° is IA
  • the characteristic peak intensity (C2/m peak) in the range of 19°-22° is When I B , 0.1 ⁇ I B /I A ⁇ 0.5, on the one hand, there is a sufficient amount of lithium manganese oxide in the positive electrode material to provide lithium ions for the lithium cobalt oxide with P6 3 mc crystal structure, and to supplement the formation of the SEI film. On the other hand, the excess of lithium manganese oxide is avoided, thereby greatly improving the cycle stability of the cathode material.
  • the average particle size D1 of the lithium cobalt oxide having the P6 3 mc structure and the average particle size D2 of the lithium manganese oxide having the C2/m crystal structure satisfy: 0.1 ⁇ D2/D1 ⁇ 0.5. Satisfying the above particle size relationship, the small particles of lithium manganese oxide that play the role of supplementing lithium can mainly exist in the pores between the large particle size lithium cobalt oxides, reducing the change of the lithium manganese oxide structure due to the cycle process. It adversely affects the active connections between Li-Co oxides, thereby maintaining high cycling stability.
  • the average particle size D1 is 5 ⁇ m to 30 ⁇ m; the average particle size D2 is 1 ⁇ m to 5 ⁇ m.
  • the method for confirming holes and gaps includes: using an ion polishing machine (JEOL-IB-09010CP) to process the material to obtain a cross-section; using SEM to photograph the cross-section with a shooting magnification of not less than 5.0K to obtain Grain images, in which closed areas of a different color than the surrounding are holes and cracks.
  • the closed area refers to an area enclosed by closed lines in the image, and the line connecting any point inside the closed area and any point outside the area intersects the boundary of the area.
  • the hole selection requirements may be: in a single particle in the image, the ratio of the longest axis of the closed area to the longest axis of the particle is not higher than 10%, and the difference between the longest axis and the shortest axis of the closed area is less than 0.5 microns;
  • the requirements for the selection of cracks can be as follows: the ratio of the longest axis of the closed region in a single particle to the longest axis of the particle is not less than 70%.
  • the lithium cobalt oxide includes Li and Co elements and optionally includes at least one of M element or Na element, wherein M element includes Al, Mg, Ti, Mn, Fe, Ni, Zn, At least one of Cu, Nb, Cr, Y or Zr; the sum of the molar content of Co and M elements is n Co+M , the molar content of Li element is n Li , and the ratio x of n Li to n Co+M is 0.6 ⁇ x ⁇ 0.95, the molar content of M element is n M , the ratio of n M to n Co+M y is 0 ⁇ y ⁇ 0.15, the molar content of Na element is n Na , the ratio of n Na to n Co+M z is 0 ⁇ z ⁇ 0.03.
  • M element includes Al, Mg, Ti, Mn, Fe, Ni, Zn, At least one of Cu, Nb, Cr, Y or Zr
  • the sum of the molar content of Co and M elements is n Co+M
  • the lithium cobalt oxide includes Li x Na z Co 1-y My O 2 , 0.6 ⁇ x ⁇ 0.95, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03, and M includes Al, Mg, Ti, At least one of Mn, Fe, Ni, Zn, Cu, Nb, Cr, Y, and Zr.
  • the lithium manganese oxide includes Li 2 ⁇ h Mn 1-g T g O k , 0 ⁇ h ⁇ 1, 0 ⁇ g ⁇ 0.5, 0 ⁇ k ⁇ 5, T includes Ti, Sn, Ru, At least one of Ni, Co and Al.
  • the method for preparing the positive electrode material of the present application comprises the steps of:
  • step b Use the Nan Co 1-y My O 2 obtained in step a as the precursor, mix it with the lithium-containing molten salt uniformly, and react at 200°C-400°C in an air atmosphere. After the reaction is completed, the reactant is subjected to Deionized water was washed several times, and after the molten salt was cleaned, the powder was dried to obtain Li x Na z Co 1-y My O 2 with a hexagonal close-packed (HCP) oxygen structure, where 0.6 ⁇ x ⁇ 0.85, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03;
  • HCP hexagonal close-packed
  • step d Mix the products obtained in step b and step c uniformly according to a certain proportion to obtain the positive electrode material of the present application.
  • the M element is selected from at least one of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, Y, and Zr.
  • the precipitating agent comprises sodium carbonate.
  • the complexing agent comprises aqueous ammonia.
  • step a the pH is 5-9.
  • the T element includes at least one of Ti, Sn, Ru, Ni, Co, and Al.
  • step d the mass ratio of the product obtained in step c mixed with the product obtained in step b is m, and 0 ⁇ m ⁇ 0.2.
  • the electrochemical device of the present application is, for example, a primary battery or a secondary battery.
  • the secondary battery is, for example, a lithium secondary battery, and the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical device includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.
  • the positive electrode sheet is known in the art as a positive electrode sheet that can be used in electrochemical devices.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode material disposed on the positive electrode current collector.
  • the positive electrode sheet includes the positive electrode material described above in the present application.
  • the structure of the positive electrode sheet is known in the art as the structure of the positive electrode sheet that can be used in an electrochemical device.
  • the preparation method of the positive electrode sheet is known in the art and can be used for the preparation of the positive electrode sheet of the electrochemical device.
  • a positive electrode active material, a binder, and a conductive material and a thickener are added as required, and then the positive electrode slurry is dissolved or dispersed in a solvent.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the positive electrode active material layer, such as but not limited to N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the electrochemical devices of the present application include a negative electrode sheet.
  • the negative electrode sheet is a negative electrode sheet known in the art that can be used in an electrochemical device.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
  • the anode active material layer includes an anode active material and an anode binder.
  • the negative electrode active material can be selected from various conventionally known materials that can be used as negative electrode active materials of electrochemical devices that can intercalate and deintercalate active ions or conventionally known materials capable of doping and dedoping active ions. substance.
  • the negative active material includes at least one of lithium metal, lithium metal alloy, transition metal oxide, carbon material, and silicon-based material.
  • the anode binder may include various polymeric binders.
  • the negative electrode active material layer further includes a negative electrode conductive agent.
  • the negative electrode conductive agent is used to provide conductivity for the negative electrode and can improve the conductivity of the negative electrode.
  • the negative electrode conductive agent is a conductive material known in the art that can be used as the negative electrode active material layer.
  • the negative electrode conductive agent may be selected from any conductive material as long as it does not cause chemical changes.
  • the structure of the negative electrode sheet is known in the art as the structure of the negative electrode sheet that can be used in an electrochemical device.
  • the preparation method of the negative electrode sheet is known in the art for the preparation method of the negative electrode sheet that can be used in an electrochemical device.
  • negative electrode active material and binder are usually added, and conductive material and thickener are added as required, and then dissolved or dispersed in a solvent to prepare negative electrode slurry.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the negative electrode active material layer, and the solvent is, for example, but not limited to, water.
  • Thickeners are known in the art and can be used as a thickener for the negative active material layer, such as, but not limited to, sodium carboxymethylcellulose.
  • the electrochemical devices of the present application include a separator.
  • the separator is a separator known in the art that can be used in electrochemical devices, such as, but not limited to, a polyolefin-based porous membrane.
  • the polyolefin-based porous film comprises polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate Monolayer or multilayer film composed of one or more of ester copolymers.
  • the present application has no particular limitations on the shape and thickness of the separator.
  • the preparation method of the separator is known in the art and can be used for the preparation of the separator of the electrochemical device.
  • the electrolyte includes an electrolyte salt.
  • Electrolyte salts are those known to those skilled in the art that are suitable for use in electrochemical devices. Appropriate electrolyte salts can be selected for different electrochemical devices. For example, for lithium ion batteries, lithium salts are generally used as electrolyte salts.
  • the electrolyte further includes an organic solvent.
  • the organic solvent is an organic solvent known to those skilled in the art and suitable for electrochemical devices, for example, a non-aqueous organic solvent is generally used.
  • the non-aqueous organic solvent includes at least one of carbonate-based solvents, carboxylate-based solvents, ether-based solvents, sulfone-based solvents, or other aprotic solvents.
  • the electrolyte further includes additives.
  • the additives are known in the art and are suitable for electrochemical devices, and can be added according to the required performance of the electrochemical device.
  • the additive comprises a carboxylate.
  • the carboxylate comprises at least one of pentasodium diethylenetriaminepentaacetate, sodium nitrilotriacetate, sodium edetate, and sodium gluconate.
  • the mass percentage of the carboxylate is 0.01%-0.15%.
  • the mass percentage of the carboxylate may be 0.02%, 0.03%, 0.05%, 0.07%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%.
  • the configuration of the electrolyte can be prepared by methods known to those skilled in the art, and its composition can be selected according to actual needs.
  • the lithium ion batteries of the examples and comparative examples were prepared according to the following methods.
  • the negative active material artificial graphite, binder styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in a weight ratio of 96:2:2 and dispersed in deionized water to form a slurry. After stirring evenly, it is coated on copper with a thickness of 6 ⁇ m.
  • the foil negative electrode current collector is dried to form a negative electrode active material layer, and is dried and cold pressed to obtain a negative electrode sheet.
  • a lithium cobalt oxide having a P6 3 mc crystal structure and a lithium manganese oxide having a C2/m crystal structure satisfying the compositional characteristics in Tables 1-4 were mixed as positive electrode materials. Then, the positive electrode material, conductive carbon black and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in the N-methylpyrrolidone solvent system in a mass ratio of 98:1:1 to obtain a positive electrode slurry, which is coated with On the aluminum foil of 12 ⁇ m, it was dried and sliced to obtain a positive electrode sheet.
  • PVDF polyvinylidene fluoride
  • a polyethylene porous polymer film with a thickness of 8 ⁇ m was used as the separator.
  • the electrolytes used in Examples 4-1 to 4-7 and Comparative Example 4-1 were obtained by adding additives with corresponding contents on the basis of the above-mentioned basic electrolyte.
  • the positive electrode sheet, the separator film and the negative electrode sheet are stacked in sequence, so that the separator film is placed between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80 °C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and shaping.
  • First-round discharge capacity and cycle performance test At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were charged with a constant current of 0.5C to a voltage of 4.8V, then left for 5 minutes, and then discharged with a constant current of 0.5C To the voltage of 3.0V, let stand for 5min, this is a cycle charge and discharge process, the discharge capacity this time is recorded as the first cycle discharge capacity.
  • the lithium-ion battery is subjected to N-cycle charge-discharge test according to the above method, and the discharge capacity of the N-cycle cycle is obtained by detection.
  • the capacity retention rate (%) of the lithium-ion battery after N cycles the discharge capacity of the Nth cycle/the discharge capacity of the first cycle ⁇ 100%.
  • Table 1 shows the effect of the composition of the cathode material and the peak intensity ratio on the performance of the lithium ion battery.
  • Table 2 shows the effect of the particle size relationship between lithium cobalt oxide with P6 3 mc crystal structure and lithium manganese oxide with C2/m crystal structure on the performance of lithium ion batteries.
  • Table 3 demonstrates the effect of the void/crack structure of LiCoO with P63mc crystal structure on the performance of Li-ion batteries.
  • Table 4 shows the effect of the content of carboxylate in the electrolyte on the performance of Li-ion batteries.
  • the positive electrode material has a sufficient amount of lithium manganese oxide to provide lithium ions for the lithium cobalt oxide having the P6 3 mc crystal structure, and supplement the formation of SEI On the other hand, it can avoid too much unstable C2/m crystal structure, thus greatly reducing the cycle stability of the cathode material.
  • the lithium cobalt oxide with the P6 3 mc crystal structure has both a hole and a crack structure.
  • it can promote the extraction of lithium ions inside the active material, thereby greatly improving the The first cycle discharge capacity of lithium-ion batteries;
  • the structure of pores and cracks can provide a buffer for stress and strain during cycling, improving the cycling stability of lithium-ion batteries.

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Abstract

本申请提供了一种正极材料及其制备方法以及电化学装置。所述正极材料包括具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物；所述正极材料的XRD图谱中，位于17°-19°范围内的特征峰峰强为I A，位于19°-22°范围内的特征峰峰强为I B，0.1≤I B/I A≤0.5。所述电化学装置包括正极片、负极片、隔离膜和电解液，其中，所述正极片包括本申请所述的正极材料。所述正极材料具有良好的结构稳定性、高容量特性以及循环稳定性。

Description

正极材料及其制备方法以及电化学装置 技术领域
本申请涉及电化学领域，具体涉及一种正极材料及其制备方法以及电化学装置。
背景技术
电化学装置，例如锂离子电池因其能量密度高、循环性能好、环保、安全且无记忆效应等优点，被广泛的应用于便携式电子产品、电动交通、国防航空、能源储备等领域。为了满足社会发展的需求，寻求具有更高能量密度和功率密度的锂离子电池是亟待解决的问题，这就要求所用正极材料具有更高比容量和更高电压平台。
目前在3C领域商业化用最多的正极材料是LiCoO 2正极材料，为R-3m相结构，理论容量为273.8mAh/g，其具有良好的循环及安全性能，高的压实密度且制备工艺简单。自1991年Sony公司实现商业化以来，LiCoO 2正极材料在锂离子电池材料市场一直占据着主要地位。为了获取更高比能量，LiCoO 2正朝着高电压(>4.6Vvs.Li/Li +)方向发展。然而LiCoO 2充电到4.5V，容量也仅能达到190mAh/g。人们试图通过从晶体结构中脱出更多的Li +来实现更高的比容量，但随着电压进一步升高，Li +大量脱出，晶体结构将发生一系列不可逆的相变(O3到H1-3，H1-3到O1)，使得材料循环性能和安全性能大大降低。加之，高电压下界面副反应加剧，Co金属溶出严重，而高电压电解液技术难以配套，常规电解液在高电压下分解加速、失效加快，因而容量衰减十分严重。
目前，产业界和科研界一般采用Al、Mg、Ti、Zn、Ni等金属阳离子进行体相掺杂，来提高R-3m相LiCoO 2的结构稳定性。大部分元素的掺杂都是通过推迟不可逆相变来提高材料的结构稳定性，但该方法在高于4.6V电压后对结构的稳定效果并不明显。此外，掺杂量增多，理论容量损失会增大。因此，急需寻求一种具有高比容量、高电压平台、结构可逆性好且在高电压下 界面稳定的锂离子电池正极材料。
发明内容
鉴于背景技术存在的问题，本申请的目的在于提供一种正极材料，其具有良好的界面稳定性、高容量性以及循环稳定性。
在一些实施例中，本申请提供一种复合正极材料，包括具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物；正极材料的XRD图谱中，位于17°-19°范围内的特征峰峰强为I A，位于19°-22°范围内的特征峰峰强为I B，0.1≤I B/I A≤0.5。
在一些实施例中，具有P6 3mc晶体结构的锂钴氧化物的平均粒径D1与具有C2/m晶体结构的锂锰氧化物的平均粒径D2满足：0.1≤D2/D1≤0.5。
在一些实施例中，平均粒径D1为5μm至30μm；平均粒径D2为1μm至5μm。
在一些实施例中，锂钴氧化物内部存在孔洞和/或裂缝。
在一些实施例中，锂钴氧化物包括Li和Co元素以及可选地包含M元素或Na元素中的至少一种，其中，M元素包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y或Zr中的至少一种；Co和M元素的摩尔含量之和为n Co+M，Li元素的摩尔含量为n Li，n Li与n Co+M的比值x为0.6<x<0.95，M元素的摩尔含量为n M，n M与n Co+M的比值y为0≤y<0.15，Na元素的摩尔含量为n Na，n Na与n Co+M的比值z为0≤z<0.03。
在一些实施例中，锂钴氧化物包括Li xNa zCo 1-yM yO 2，0.6<x<0.95，0≤y<0.15，0≤z<0.03，M包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y和Zr中的至少一种。
在一些实施例中，锂锰氧化物包括Li 2±hMn 1-gT gO k，0≤h≤1，0≤g≤0.5，0<k<5，T包括Ti、Sn、Ru、Ni、Co和Al中的至少一种。
在一些实施例中，本申请还提供了一种电化学装置，包括正极片、负极片、隔离膜和电解液，正极片包括本申请的正极材料。
在一些实施例中，电解液包括羧酸盐。
在一些实施例中，羧酸盐包括以下的至少一种：二乙烯三胺五乙酸五 钠、次氮基三乙酸钠、乙二胺四乙酸钠、葡萄糖酸钠。
在一些实施例中，基于电解液的质量，羧酸盐的质量百分含量为0.01％至0.15％。
本申请的有益效果如下：本申请提供的正极材料具有良好的界面稳定性、高容量特性以及循环稳定性。
具体实施方式
应理解的是，所公开的实施例仅是本申请的示例，本申请可以以各种形式实施，因此，本文公开的具体细节不应被解释为限制，而是仅作为权利要求的基础且作为表示性的基础用于教导本领域普通技术人员以各种方式实施本申请。
在本申请的说明中，未明确说明的术语、专业用词均为本领域技术人员的公知常识，未明确说明的方法均为本领域技术人员公知的常规方法。
在本申请的说明中，“平均粒径”指的是通过SEM扫描电镜对材料粉体进行拍摄观察，然后，使用图像解析软件，从SEM照片中随机地选出10个材料颗粒，求出这些材料颗粒各自的面积，接着，假设材料颗粒是球形，通过以下公式求出各自的粒径R(直径)：
R＝2×(S/π) 1/2；其中，S为材料颗粒的面积；
对10张SEM图像进行求出上述材料颗粒粒径R的处理，并将所得100(10×10)个材料颗粒的粒径进行算数平均，从而求得所述材料颗粒的平均粒径。
下面详细说明本申请的正极材料及其制备方法以及电化学装置。
[正极材料]
在一些实施例中，本申请的正极材料包括具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物；正极材料的XRD图谱中，位于17°-19°范围内的特征峰峰强(P6 3mc结构峰)为I A，位于19°-22°范围内的特征峰峰强(C2/m峰)为I B，0.1≤I B/I A≤0.5。
具有P6 3mc晶体结构的锂钴氧化物具有稳定的氧结构，高电压不易释氧，结构稳定，因而循环性能好。此外，其具有锂离子接收能力，能吸收额外锂 离子。C2/m晶体结构的锂锰氧化物理论容量(>300mAh/g)比P6 3mc正极材料理论容量更高，当其脱出锂离子后，能实现部分锂离子的可逆循环，将其与P6 3mc的锂钴氧化物复合在一起，可以很好结合两个材料的优点，解决各自缺点。当正极材料的XRD图谱中，位于17°-19°范围内的特征峰峰强(P63mc结构峰)为I A，位于19°-22°范围内的特征峰峰强(C2/m峰)为I B，0.1<I B/I A≤0.5时，一方面，正极材料中具有足量的锂锰氧化物为具有P6 3mc晶体结构的锂钴氧化物提供锂离子、以及补充形成SEI膜所消耗的锂离子，从而提高锂离子电池的容量；另一方面，避免了锂锰氧化物过量，从而大幅提高正极材料的循环稳定性。
在一些实施例中，具有P6 3mc结构的锂钴氧化物的平均粒径D1与具有C2/m晶体结构的锂锰氧化物的平均粒径D2满足：0.1≤D2/D1≤0.5。满足上述粒径关系，起到补锂作用的小颗粒锂锰氧化物能够主要存在于大粒径的锂钴氧化物之间的孔隙中，减小锂锰氧化物由于循环过程中自身结构的变化对锂钴氧化物之间的活性连接产生不利影响，从而维持较高的循环稳定性。
在一些实施例中，平均粒径D1为5μm至30μm；平均粒径D2为1μm至5μm。
在一些实施例中，具有P6 3mc结构的锂钴氧化物内部存在孔洞和/或裂缝。在一些实施例中，孔洞和缝隙的确认方法包括：利用离子抛光机(日本电子-IB-09010CP)对材料进行加工，得到断面；利用SEM对断面进行拍摄，拍摄倍数不低于5.0K，获得颗粒图像，在图像中，与周围颜色不同的闭合区域即为孔洞和裂缝。其中，闭合区域是指图像中由封闭线条围成的一个区域，闭合区域内部任何一点与区域外任何一点的连线都和区域的边界相交。在图像中，连接闭合曲线任意两点，最长的距离即为最长轴，最短的距离即为最短轴。其中，孔洞选取要求可为：在图像的单个颗粒中闭合区域的最长轴与颗粒最长轴的比不高于10％，且闭合区域的最长轴与最短轴的差值小于0.5微米；裂缝的选取要求可为：单个颗粒中闭合区域的最长轴与颗粒最长轴的比不低于70％。
在一些实施例中，锂钴氧化物包括Li和Co元素以及可选地包含M元素或Na元素中的至少一种，其中，M元素包括Al、Mg、Ti、Mn、Fe、 Ni、Zn、Cu、Nb、Cr、Y或Zr中的至少一种；Co和M元素的摩尔含量之和为n Co+M，Li元素的摩尔含量为n Li，n Li与n Co+M的比值x为0.6<x<0.95，M元素的摩尔含量为n M，n M与n Co+M的比值y为0≤y<0.15，Na元素的摩尔含量为n Na，n Na与n Co+M的比值z为0≤z<0.03。
在一些实施例中，锂钴氧化物包括Li xNa zCo 1-yM yO 2，0.6<x<0.95，0≤y<0.15，0≤z<0.03，M包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y和Zr中的至少一种。
在一些实施例中，锂锰氧化物包括Li 2±hMn 1-gT gO k，0≤h≤1，0≤g≤0.5，0<k<5，T包括Ti、Sn、Ru、Ni、Co和Al中的至少一种。
[正极材料的制备方法]
其次说明制备本申请正极材料的方法。
在一些实施例中，制备本申请正极材料的方法，包含步骤：
a.将可溶性Co盐(如硝酸钴)和M盐(如硝酸M盐)按Co：M＝(1-y):y的摩尔比溶入溶剂中，加入沉淀剂和络合剂，调节pH，形成沉淀；然后将沉淀物进行烧结，研磨获得(Co 1-yM y) 3O 4粉体；然后，将(Co 1-yM y) 3O 4粉体与Na 2CO 3按n：(1-y)的摩尔比在700℃-900℃、空气气氛中反应，得到Na nCo 1-yM yO 2，其中0≤y<0.15，0.6≤n<1；
b.采用步骤a得到的Na nCo 1-yM yO 2作为前躯体，将其与含锂熔盐混合均匀，在200℃-400℃、空气气氛中反应，反应完成后将反应物经去离子水多次洗涤，待熔盐清洗干净，烘干粉体得到具有密排六方(HCP)氧结构的Li xNa zCo 1-yM yO 2，其中，0.6<x<0.85，0≤y<0.15，0≤z<0.03；
c.将锂盐和M和N盐或M和N的氧化物按照Li：Mn：N＝2+h：1：g的摩尔比混合，进行一步在700℃-900℃、空气气氛中反应烧结得到Li 2 ±hMn 1-gN gO k，其中，0≤h≤1，0≤g≤0.5，0<k<5。
d.将步骤b与步骤c得到的产物按照一定比例混合均匀，得到本申请的正极材料。
在一些实施例中，在步骤a中，M元素选自Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y和Zr中的至少一种。
在一些实施例中，在步骤a中，沉淀剂包含碳酸钠。
在一些实施例中，在步骤a中，络合剂包含氨水。
在一些实施例中，在步骤a中，pH为5-9。
在一些实施例中，在步骤c中，T元素包含Ti、Sn、Ru、Ni、Co和Al中的至少一种。
在一些实施例中，在步骤d中，步骤c得到的产物与步骤b得到的产物混合的质量比为m，0<m≤0.2。
[电化学装置]
最后说明本申请的电化学装置。
本申请的电化学装置例如为一次电池、二次电池。二次电池例如为锂二次电池，锂二次电池包含但不限于锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
在一些实施例中，电化学装置包含正极片、负极片、隔离膜以及电解液。
<正极片>
正极片是本领域技术公知的可被用于电化学装置的正极片。在一些实施例中，正极片包含正极集流体以及设置在正极集流体上的正极材料。在一些实施例中，正极片包含本申请前述的正极材料。
在一些实施例中，正极片的结构为本领域技术公知的可被用于电化学装置的正极片的结构。
在一些实施例中，正极片的制备方法是本领域技术公知的可被用于电化学装置的正极片的制备方法。在一些实施例中，在正极浆料的制备中，通常加入正极活性物质、粘结剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成正极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作正极活性物质层的溶剂，溶剂例如但不限于N-甲基吡咯烷酮(NMP)。
<负极片>
在一些实施例中，本申请的电化学装置包含负极片。负极片是本领域技术公知的可被用于电化学装置的负极片。在一些实施例中，负极片包含负极集流体以及设置在负极集流体上的负极活性物质层。在一些实施例中，负极活性物质层包括负极活性物质以及负极粘结剂。
负极活性物质可选用本领域技术公知的各种可被用作电化学装置的负极活性物质的能够嵌入、脱嵌活性离子的传统公知的物质或能够掺杂、脱掺杂活性离子的传统公知的物质。
在一些实施例中，负极活性物质包含锂金属、锂金属合金、过渡金属氧化物、碳材料、硅基材料中的至少一种。
在一些实施例中，负极粘结剂可以包含各种聚合物粘合剂。
在一些实施例中，负极活性物质层还包含负极导电剂。负极导电剂用于为负极提供导电性，可改善负极导电率。负极导电剂是本领域公知的可被用作负极活性物质层的导电材料。负极导电剂可以选自任何导电的材料，只要它不引起化学变化即可。
在一些实施例中，负极片的结构为本领域技术公知的可被用于电化学装置的负极片的结构。
在一些实施例中，负极片的制备方法是本领域技术公知的可被用于电化学装置的负极片的制备方法。在一些实施例中，在负极浆料的制备中，通常加入负极活性物质、粘合剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成负极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作负极活性物质层的溶剂，溶剂例如但不限于水。增稠剂是本领域公知的可被用作负极活性物质层的增稠剂，增稠剂例如但不限于羧甲基纤维素钠。
<隔离膜>
在一些实施例中，本申请的电化学装置包含隔离膜。隔离膜是本领域技术公知的可被用于电化学装置的隔离膜，例如但不限于聚烯烃类多孔膜。在一些实施例中，聚烯烃类多孔膜包含聚乙烯(PE)、乙烯-丙烯共聚物、聚丙烯(PP)、乙烯-丁烯共聚物、乙烯-己烯共聚物、乙烯-甲基丙烯酸甲酯共聚物中的一种或几种组成的单层或多层膜。
本申请对隔离膜的形态和厚度没有特别的限制。隔离膜的制备方法是本领域技术公知的可被用于电化学装置的隔离膜的制备方法。
<电解液>
在一些实施例中，电解液包含电解质盐。电解质盐是本领域技术公知的适用于电化学装置的电解质盐。针对不同的电化学装置，可以选用合适的电 解质盐。例如对于锂离子电池，电解质盐通常使用锂盐。
在一些实施例中，电解液还包含有机溶剂。有机溶剂是本领域技术公知的适用于电化学装置的有机溶剂，例如通常使用非水有机溶剂。在一些实施例中，非水有机溶剂包含碳酸酯类溶剂、羧酸酯类溶剂、醚类溶剂、砜类溶剂或其他非质子溶剂中的至少一种。
在一些实施例中，电解液还包含添加剂。添加剂是本领域技术公知的适用于电化学装置的添加剂，可根据需要的电化学装置的性能进行添加。在一些实施例中，添加剂包含羧酸盐。在一些实施例中，羧酸盐包含二乙烯三胺五乙酸五钠、次氮基三乙酸钠、乙二胺四乙酸钠、葡萄糖酸钠中的至少一种。在一些实施例中，基于电解液的质量，羧酸盐的质量百分含量为0.01％-0.15％。在一些实施例中，基于电解液的质量，羧酸盐的质量百分含量可为0.02％、0.03％、0.05％、0.07％、0.09％、0.10％、0.11％、0.12％、0.13％。
电解液的配置可通过本领域技术人员公知的方法调配而成，其组成可根据实际需要进行选择。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。在下述实施例、对比例中，所使用到的试剂、材料等如没有特殊的说明，均可商购获得或合成获得。
实施例和对比例的锂离子电池均按照下述方法制备。
(1)负极片的制备：
将负极活性材料人造石墨、粘结剂丁苯橡胶和羧甲基纤维素钠按重量比96：2：2混合后分散于去离子水中形成浆料，搅拌均匀后涂布于厚度为6μm的铜箔负极集流体上，干燥，形成负极活性材料层，经过烘干和冷压，得到负极片。
(2)正极片的制备：
将满足表1-4中组成特征的具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物混合作为正极材料。然后将正极材料、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按质量比98：1：1在N-甲基吡咯烷酮溶剂体 系中充分搅拌混合均匀后，得到正极浆料，涂覆于12μm的铝箔上，干燥、切片，得到正极片。
(3)隔离膜的制备：
采用厚度为8μm的聚乙烯多孔聚合物膜作为隔离膜。
(4)电解液的制备：
在含水量小于10ppm的环境下，将六氟磷酸锂(1.15mol/L)与非水有机溶剂(其组成为碳酸乙烯酯EC：碳酸亚丙酯PC：碳酸二乙酯DEC＝1：1：1，重量比)混合得到实施例1-1至实施例1-16、对比例1-1至对比例1-6、实施例2-1至实施例2-5、实施例3-1至实施例3-3以及对比例4-2中使用的基础电解液。在上述基础电解液的基础上添加相应含量的添加剂即得实施例4-1至4-7、对比例4-1中使用的电解液。
(5)锂离子电池的制备：
将正极片、隔离膜、负极片按顺序依次叠好，使隔离膜处于正极片和负极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，整形等工艺流程得到锂离子电池。
接下来说明锂离子电池的性能测试过程。
首圈放电容量及循环性能测试：在25℃下，将实施例和对比例制备得到的锂离子电池以0.5C恒流充电至电压为4.8V，之后静置5min，再以0.5C恒流放电至电压为3.0V，静置5min，此为一个循环充放电过程，此次的放电容量记为首圈放电容量。将锂离子电池按照上述方法进行N圈循环充放电测试，检测得到第N圈循环的放电容量。锂离子电池循环N圈后的容量保持率(％)＝第N圈循环的放电容量/首圈放电容量×100％。
实施例和对比例的锂离子电池的相关参数以及锂离子电池的性能测试结果如表1-表4所示。
表1展示了正极材料的组成、峰强比对锂离子电池性能的影响。
表2展示了具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物之间的粒径关系对锂离子电池性能的影响。
表3展示了具有P6 3mc晶体结构的锂钴氧化物的空洞/裂缝结构对锂离子电池性能的影响。
表4展示了电解液中羧酸盐的含量对锂离子电池性能的影响。
Figure PCTCN2021105205-appb-000001
通过比较表1的实施例1-1至1-16和对比例1-1至1-6可知，当所述正极材料的XRD图谱中，0.1≤I B/I A≤0.5时，相较于不含锂锰氧化物的对比例1-1至1-4，在维持较优的循环容量保持率的同时，首圈放电容量大幅提升；而相较于I B/I A>0.5的对比例1-5至1-6，其循环容量保持率更为优异。这是由于，满足0.1≤I B/I A≤0.5，一方面，正极材料中具有足量的锂锰氧化物为具有P6 3mc晶体结构的锂钴氧化物提供锂离子、并且补充了形成SEI膜所消耗的锂离子，从而大幅提高了锂离子电池的首圈放电容量；另一方面，能够避免不稳定的C2/m晶体结构过多，从而大幅降低正极材料的循环稳定性。
表2
Figure PCTCN2021105205-appb-000002
通过比较表2的实施例2-1至2-5可知，当具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物之间的粒径关系满足0.1≤D2/D1≤0.5，锂离子电池能够具有更加优异的循环容量保持率。这是由于：起补锂作用的小颗粒锂锰氧化物能够主要存在于大粒径的锂钴氧化物之间的孔隙中，减小锂锰氧化物由于循环过程中自身结构的变化对锂钴氧化物之间的活性连接产生不利影响，从而维持较高的循环稳定性。
表3
Figure PCTCN2021105205-appb-000003
通过比较表3的实施例3-1至3-3可知，具有P6 3mc晶体结构的锂钴氧化物同时具有孔洞和裂缝结构，一方面，能够促进活性材料内部的锂离子脱出，从而大幅提升锂离子电池的首圈放电容量；另一方面，孔洞和裂缝结构 能够为循环过程中的应力应变提供缓冲作用，提升了锂离子电池的循环稳定性。
表4
Figure PCTCN2021105205-appb-000004
通过比较表4的实施例4-1至4-7和对比例4-1至4-2可知，电解液中添加适量的羧酸盐能够大幅提升锂离子电池的循环容量保持率。这是由于适量的羧酸盐能够稳定正极材料中的Mn等过渡金属，从而提升锂离子电池的循环稳定性。
以上所述，仅是本申请的示例，并非对本申请做任何形式的限制，虽然本申请以较佳实施例揭示如上，然而并非用以限制本申请，任何熟悉本专业的技术人员，在不脱离本申请技术方案的范围内，利用上述揭示的技术内容做出些许的变动或修饰均等同于等效实施案例，均在本申请技术方案的范围内。

Claims (10)

  1. 一种正极材料，其特征在于，包括具有P6 3mc晶体结构的锂钴氧化物以及具有C2/m晶体结构的锂锰氧化物；所述正极材料的XRD图谱中，位于17°-19°范围内的特征峰峰强为I A，位于19°-22°范围内的特征峰峰强为I B，0.1≤I B/I A≤0.5。
  2. 根据权利要求1所述的正极材料，其特征在于，所述具有P6 3mc晶体结构的锂钴氧化物的平均粒径D1与所述具有C2/m晶体结构的锂锰氧化物的平均粒径D2满足：0.1≤D2/D1≤0.5。
  3. 根据权利要求2所述的正极材料，其特征在于，所述平均粒径D1为5μm至30μm；所述平均粒径D2为1μm至5μm。
  4. 根据权利要求1所述的正极材料，其特征在于，所述锂钴氧化物内部存在孔洞和/或裂缝。
  5. 根据权利要求1所述的正极材料，其特征在于，所述正极材料满足以下条件的至少一者：
    a)所述锂钴氧化物包括Li和Co元素以及可选地包含M元素或Na元素中的至少一种，其中，M元素包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y或Zr中的至少一种；所述Co和M元素的摩尔含量之和为n Co+M，所述Li元素的摩尔含量为n Li，所述n Li与所述n Co+M的比值x为0.6<x<0.95，所述M元素的摩尔含量为n M，所述n M与所述n Co+M的比值y为0≤y<0.15，所述Na元素的摩尔含量为n Na，所述n Na与所述n Co+M的比值z为0≤z<0.03；
    b)所述锂锰氧化物包括Li 2±hMn 1-gT gO k，0≤h≤1，0≤g≤0.5，0<k<5，T包括Ti、Sn、Ru、Ni、Co和Al中的至少一种。
  6. 根据权利要求5所述的正极材料，其特征在于，所述锂钴氧化物 包括Li xNa zCo 1-yM yO 2，0.6<x<0.95，0≤y<0.15，0≤z<0.03，M包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Y和Zr中的至少一种。
  7. 一种电化学装置，包括正极片、负极片、隔离膜和电解液，所述正极片包括权利要求1-6中任一项所述的正极材料。
  8. 根据权利要求7所述的电化学装置，所述电解液包括羧酸盐。
  9. 根据权利要求8所述的电化学装置，所述羧酸盐包括以下的至少一种：
    二乙烯三胺五乙酸五钠、次氮基三乙酸钠、乙二胺四乙酸钠、葡萄糖酸钠。
  10. 根据权利要求8所述的电化学装置，基于所述电解液的质量，所述羧酸盐的质量百分含量为0.01％至0.15％。
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