WO2023092930A1 - 钠离子正极材料及其制备方法、钠离子电池 - Google Patents

钠离子正极材料及其制备方法、钠离子电池 Download PDF

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WO2023092930A1
WO2023092930A1 PCT/CN2022/087447 CN2022087447W WO2023092930A1 WO 2023092930 A1 WO2023092930 A1 WO 2023092930A1 CN 2022087447 W CN2022087447 W CN 2022087447W WO 2023092930 A1 WO2023092930 A1 WO 2023092930A1
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positive electrode
manganese
source
electrode material
sodium ion
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English (en)
French (fr)
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张昊阳
蒋易晟
王占洲
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横店集团东磁股份有限公司
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Priority to EP22803159.7A priority Critical patent/EP4213244A1/en
Publication of WO2023092930A1 publication Critical patent/WO2023092930A1/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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 invention relates to the technical field of sodium ion batteries, in particular to a sodium ion positive electrode material, a preparation method thereof, and a sodium ion battery.
  • Lithium-ion batteries have been widely used in the field of energy storage due to their high energy density and long cycle life. However, the abundance of lithium resources in the earth's crust is low and the distribution is uneven. With the increasing demand for batteries in the energy storage field, the cost of lithium-ion batteries continues to rise. Sodium has similar physical and chemical properties to lithium, and sodium is rich in resources and low in price. The principle of sodium-ion batteries is similar to that of lithium-ion batteries. Sodium-ion batteries are considered to be a new generation of high-performance, low-cost secondary battery technology .
  • Manganese-based layered materials have attracted widespread attention due to their advantages such as simple preparation, environmental friendliness, and large specific capacity.
  • the manganese-based cathode material is easily eroded by the electrolyte during the charging and discharging process, which changes the structure of the material and seriously affects its cycle performance.
  • the current energy density of sodium-ion batteries is not as good as that of lithium-ion batteries.
  • the formation of SEI film during the formation process will consume a large amount of sodium source, further reducing the active sodium source, reducing the energy density, and limiting manganese. Further applications of base materials.
  • negative electrode pre-sodiumization is used to improve the consumption of sodium source.
  • the method and form are introduced into the battery system.
  • the pre-sodiumization of the negative electrode can be divided into direct addition of exogenous sodium, pre-sodiumization of active additives, electrochemical pre-sodiumization and chemical pre-sodiumization.
  • the above methods all involve further processing of the coated negative electrode sheet, and even need to use metal sodium directly to pre-sodiumize it, which has high requirements on the workshop environment and equipment, and takes a long time, which is not conducive to commercialization.
  • Sodium supplementation of the positive electrode isolates the erosion of the manganese-based matrix material and the electrolyte by coating inactive substances, which improves the cycle performance of the material, but at the same time affects its energy density.
  • the main purpose of the present invention is to provide a kind of sodium ion positive electrode material and its preparation method, sodium ion battery, to solve the problem of low capacity and poor cycle performance caused by the consumption of sodium source in the first circle of sodium ion positive electrode material in the prior art question.
  • a sodium ion positive electrode material includes a manganese-based positive electrode material and a coating layer coated on the manganese-based positive electrode material, the chemical composition of the manganese-based positive electrode material
  • the general formula is Na x Mn y M 1-y O 2 , wherein, M is selected from any one of Cu, Fe, Co, and Ni, and 0.5 ⁇ x ⁇ 1, 0.5 ⁇ y ⁇ 1, and the cladding layer contains Lithium ternary material
  • the coating layer is 5-20 wt%, preferably 10-20 wt%, and further preferably 12-17 wt%, of the manganese-based positive electrode material.
  • the above-mentioned sodium ion positive electrode material has a particle size of 0.2-1 ⁇ m.
  • a method for preparing the aforementioned sodium ion positive electrode material comprising: Step S1, which will include a manganese-based positive electrode material, a lithium source, a nickel source, a cobalt source, a manganese source, and a complex
  • Step S1 which will include a manganese-based positive electrode material, a lithium source, a nickel source, a cobalt source, a manganese source, and a complex
  • the raw materials of the agent are mixed and heated to obtain a gel; in step S2, the gel is sintered in an oxygen-containing atmosphere to obtain a sodium ion positive electrode material.
  • step S1 includes: step S11, mixing the raw materials to obtain a mixed solution; step S12, adjusting the pH value of the mixed solution to obtain a sol; step S13, heating the sol to obtain a gel; the preferred pH value is 7 ⁇ 8.
  • the heating temperature is preferably 70-90°C, and the heating method is preferably water bath heating.
  • the mixing process preferably includes: first mixing the manganese-based positive electrode material, lithium source, nickel source, cobalt source, and manganese source with water, Form the first solution; secondly mix the complexing agent with water to form the second solution; drop the second solution into the first solution to obtain the mixed solution; preferably adjust the pH value of the mixed solution by ammonia water, preferably the first mixed solution
  • the stirring speed of the mixing is 400-600r/min, the stirring time of the first mixing is preferably 3-5h, the stirring speed of the second mixing is preferably 300-500r/min, and the stirring time of the second mixing is 1-2h.
  • the manganese-based positive electrode material, nickel source, cobalt source, and manganese source are calculated by the transition metal ions contained in each component, and the lithium source is calculated by lithium ions.
  • the manganese-based positive electrode material, lithium source, and nickel source The molar ratio of cobalt source and manganese source is 23 ⁇ 28:1.6 ⁇ 6.4:0.5 ⁇ 2:0.5 ⁇ 2:0.5 ⁇ 2, preferably 23 ⁇ 28:3.2 ⁇ 6.4:1 ⁇ 2:1 ⁇ 2:1 ⁇ 2, more preferably 23 ⁇ 28:3.84 ⁇ 5.44:1.2 ⁇ 1.7:1.2 ⁇ 1.7:1.2 ⁇ 1.7; preferred lithium source is lithium carbonate and/or lithium hydroxide, preferred nickel source is selected from nickel acetate, nickel sulfate, chlorine Any one or more in nickel chloride, preferably cobalt source is selected from any one or more in cobalt acetate, cobalt sulfate, cobalt chloride, preferably manganese source is selected from manganese acetate, manganese sulfate, manganese
  • the total number of moles of the nickel source, cobalt source, and manganese source is n, and the ratio of the number of moles of the complexing agent to n is 1 to 1.1:1, preferably complexing
  • the mixture is selected from any one or more of citric acid, glycolic acid and acetic acid.
  • the above-mentioned sintering temperature is 800-1000° C., preferably the sintering time is 10-14 hours, and preferably the sintering heating rate is 5-10° C./min.
  • the drying temperature is 400-450° C.
  • the drying time is preferably 4-7 hours.
  • a sodium ion battery including a positive electrode and a negative electrode, the positive electrode includes a positive electrode material, and the positive electrode material is the aforementioned sodium ion positive electrode material.
  • the present invention aims at the problem that the manganese-based positive electrode material is easily eroded by the electrolyte and the problem of sodium source consumption in the process of forming the SEI film, and uses a lithium-containing ternary material with a large capacity as a coating layer to protect against sodium
  • the coating layer reduces the erosion of the electrolyte on the manganese-based cathode material
  • the lithium source containing lithium-containing ternary materials is used as a sacrificial agent to form a part of the SEI film. Therefore, the loss of the active sodium source in the manganese-based positive electrode material is reduced, and the electrical properties such as the reversible capacity and cycle performance of the sodium ion positive electrode material are improved.
  • FIG. 1 shows a schematic diagram of the first-cycle charge-discharge curve of the cylindrical sodium-ion battery of Example 1 at 2-4.1V.
  • the present invention provides a sodium ion positive electrode material Its preparation method and sodium ion battery.
  • a sodium ion positive electrode material in a typical embodiment of the present application, includes a manganese-based positive electrode material and a coating layer coated on the manganese-based positive electrode material, the chemical composition of the manganese-based positive electrode material
  • the general formula is Na x Mn y M 1-y O 2 , wherein, M is selected from any one of Cu, Fe, Co, and Ni, and 0.5 ⁇ x ⁇ 1, 0.5 ⁇ y ⁇ 1, and the cladding layer contains Lithium ternary material
  • the present invention aims at the problem that the manganese-based positive electrode material is easily eroded by the electrolyte and the problem of sodium source consumption in the process of forming the SEI film.
  • the lithium-containing ternary material with a large capacity is used as a coating layer to coat the sodium ion positive electrode material.
  • the coating layer reduces the erosion of the electrolyte on the manganese-based cathode material; on the other hand, during the formation process, the lithium source containing lithium-containing ternary materials is used as a sacrificial agent to form a part of the SEI film, thereby reducing the corrosion resistance of the manganese-based cathode material.
  • the loss of the active sodium source in the battery improves the electrical properties such as the reversible capacity and cycle performance of the sodium ion cathode material.
  • the above-mentioned coating layer is 5-20wt% of the manganese-based positive electrode material, preferably 10-20wt%, further, preferably It is 12-17wt%.
  • the above-mentioned sodium ion positive electrode material has a particle size of 0.2-1 ⁇ m, which is more suitable for the use requirements of current positive electrode materials.
  • a method for preparing the above-mentioned sodium ion positive electrode material includes: Step S1, which will include a manganese-based positive electrode material, a lithium source, a nickel source, a cobalt source, The raw materials of the manganese source and the complexing agent are mixed and heated to obtain a gel; in step S2, the gel is sintered in an atmosphere containing oxygen to obtain a sodium ion positive electrode material.
  • step S1 of the present application after the raw materials are mixed, a low-viscosity solution is first formed in a solvent, thereby obtaining a homogeneous sol at the molecular level in a short time, and further forming a uniformly mixed gel at the molecular level after heating, the sol-gel
  • the preparation conditions of the method are mild, each component is easy to control, the reaction time is short, the temperature is controllable, and the particle size obtained is small and uniform. After the sintering of the gel, the sodium ion positive electrode material with uniform coating and uniform particles is obtained.
  • step S1 includes: step S11, mixing the raw materials to obtain a mixed solution; step S12, adjusting the pH value of the mixed solution to obtain a sol; step S13, heating the sol to obtain a gel
  • the preferred pH value is 7-8, the preferred heating temperature is 70-90°C, the preferred heating method is water bath heating, and the preferred mixing process includes: manganese-based positive electrode material, lithium source, nickel source, cobalt source, manganese source Mix firstly with water to form the first solution; secondly mix the complexing agent with water to form the second solution; drop the second solution into the first solution to obtain the mixed solution; preferably adjust the mixed solution by ammonia water pH value, preferably the stirring speed of the first mixing is 400 ⁇ 600r/min, the preferred stirring time of the first mixing is 3 ⁇ 5h, the preferred stirring speed of the second mixing is 300 ⁇ 500r/min, the preferred stirring time of the second mixing For 1 ⁇ 2h.
  • the manganese-based positive electrode material, lithium source, nickel source, cobalt source, and manganese source with water to obtain a uniform first solution; secondly mix the complexing agent with water to form a uniform second solution; The second solution is dropped into the first solution to obtain a uniform mixed solution.
  • the preferred above-mentioned stirring speed and time are conducive to obtaining a uniform low-viscosity first solution and the second solution, and the second solution is dropped into the first solution.
  • the way of dripping helps to make the viscosity of the mixed solution not suddenly too large, which is conducive to the formation of a uniformly mixed gel sol at the molecular level.
  • a uniformly mixed gel at the molecular level is further formed, and then passed through The sintering of the gel makes the sodium ion cathode material with uniform coating and uniform particles.
  • the preparation conditions of the sol-gel method are mild, each component is easy to control, the reaction time is short, the temperature is controllable, and the particle size obtained is small and uniform.
  • the manganese-based positive electrode material, the nickel source, the cobalt source, and the manganese source are calculated by transition metal ions contained in each component, and the lithium source is calculated by lithium ions.
  • the above-mentioned manganese-based positive electrode The molar ratio of material, lithium source, nickel source, cobalt source and manganese source is 23 ⁇ 28:1.6 ⁇ 6.4:0.5 ⁇ 2:0.5 ⁇ 2:0.5 ⁇ 2, preferably 23 ⁇ 28:3.2 ⁇ 6.4:1 ⁇ 2 :1 ⁇ 2:1 ⁇ 2, more preferably 23 ⁇ 28:3.84 ⁇ 5.44:1.2 ⁇ 1.7:1.2 ⁇ 1.7:1.2 ⁇ 1.7; preferred lithium source is lithium carbonate and/or lithium hydroxide, preferred nickel source is selected from Any one or more in nickel acetate, nickel sulfate, nickel chloride, preferred cobalt source is selected from any one or more in cobalt acetate, cobalt sulfate, cobalt chloride, preferred manganese source is selected from manganese acetate, sulfuric
  • the raw materials of the above-mentioned ratio and their types are conducive to their dispersion uniformity in the solvent, and obtain the manganese-based positive electrode material Na x Mn y M 1-y O 2 with excellent performance and the lithium-containing
  • the amount of the ternary material LiNiaCobMncO2 cladding layer varies with the molar ratio of the lithium source, the nickel source, the cobalt source, and the manganese source .
  • the molar ratio of the manganese source is more conducive to the formation of a LiNia Co b Mn c O 2 coating layer that is well coated on Na x Mn y M 1-y O 2 , wherein, during the sintering process of the gel, the lithium source There is a small amount of loss due to volatilization, so a slightly excess lithium source is added.
  • the total number of moles of nickel source, cobalt source, and manganese source is n, and the number of moles of complexing agent
  • the ratio to n is 1 to 1.1:1.
  • the above-mentioned complexing agent is selected from any one or more of citric acid, glycolic acid, and acetic acid. Among them, although adding a little more complexing agent will not cause adverse reactions to sodium ions The reduction of the electrical performance of the positive electrode material will cause its waste, which will lead to an increase in cost.
  • the sintering temperature is preferably 800-1000°C
  • the sintering time is 10-14h
  • the heating rate is 5-10°C/min.
  • the drying temperature is 400-450° C., and the drying time is preferably 4-7 hours.
  • Drying the gel before sintering is beneficial to eliminate the interference of moisture in the gel on the sintering process.
  • a sodium ion battery including a positive electrode and a negative electrode, the positive electrode includes a positive electrode material, and the positive electrode material is the above-mentioned sodium ion positive electrode material.
  • a sodium ion battery comprising the sodium ion cathode material of the present application has a higher reversible capacity and a longer lifespan.
  • the sodium ion battery mainly includes: positive electrode, negative electrode, diaphragm, electrolyte and casing.
  • the preparation method of preferred positive pole comprises:
  • a binder polyvinylidene fluoride, sodium alginate, etc. is added to N-methylpyrrolidone to prepare a glue solution with a concentration of 6%.
  • the preparation method of preferred negative electrode comprises:
  • hard carbon added into deionized water in proportion to prepare a slurry and coat it on copper foil, remove the solvent at high temperature, roll and cut to obtain the negative electrode, of which hard carbon: CMC :
  • the mass ratio of SBR is 97:1.5:1.5.
  • the sodium salt in the electrolyte is any one or more of NaClO 4 , NaPF 6 , and NaTFSI
  • the organic solvent in the electrolyte is any of ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate. one or more.
  • the stirring speed of the first mixing is 600r/min
  • the stirring time of the first mixing is 3h
  • the stirring speed of the second mixing is 500r/min
  • the stirring time of the second mixing is 1h.
  • the pH value of the mixed liquid is adjusted between 7 and 8 with ammonia water to obtain a sol. Heat the sol water bath to 80°C to remove moisture and obtain a gel. The gel was dried at 450°C for 5 hours. Then the gel was sintered at 900°C (heating rate of 5-10°C/min) for 12 hours to obtain a sodium ion positive electrode material with a LiNiaCobMncO2 coating amount of 14wt%.
  • the charge-discharge curve of the first cycle under V is shown in Figure 1.
  • the charge specific capacity is 103mAh/g
  • the discharge capacity is 84.5mAh/g.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 to citric acid is 26:3.84:1.2:1.2:1.2, and the molar ratio of Na 0.67 MnO 2 to citric acid is 26:3.6, finally obtaining a sodium ion cathode material with a coating amount of 12wt%.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 and citric acid was 26:5.44:1.7:1.7:1.7, and the molar ratio of Na 0.67 MnO 2 to citric acid was 26:5.1. Finally, a sodium ion cathode material with a coating amount of 17wt% was obtained.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 and citric acid was 26:3.2:1:1:1, and the molar ratio of Na 0.67 MnO 2 to citric acid was 26:3. Finally, a sodium ion cathode material with a coating amount of 10wt% was obtained.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 to citric acid is 26:6, and the molar ratio of Na 0.67 MnO 2 to citric acid is 26:6, and finally a sodium ion cathode material with a coating amount of 20% is obtained.
  • Na 0.67 MnO 2 , lithium chloride, nickel chloride, cobalt chloride, and manganese chloride are calculated based on the transition metal ions contained in each component , the molar ratio in lithium chloride (calculated as lithium ions) is 26:4.48:1.4:1.4:1.4, and finally a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • the complexing agent is glycolic acid, and finally a sodium ion positive electrode material with a coating amount of 14wt% is obtained.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 to citric acid was 26:4.62, and the molar ratio of Na 0.67 MnO 2 to citric acid was 23:4.48:1.4:1.4:1.4. Finally, a sodium ion cathode material with a coating amount of 14% was obtained.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 to citric acid is 26:3.78, and the molar ratio of Na 0.67 MnO 2 to citric acid is 26:3.78. Finally, a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • Na 0.67 MnO 2 , lithium carbonate , nickel acetate, cobalt acetate, manganese acetate The molar ratio of Na 0.67 MnO 2 to citric acid is 26:6.3, and the molar ratio of Na 0.67 MnO 2 to citric acid is 26:6.3, and finally a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • the sol water bath was heated to 70° C. to remove moisture to obtain a gel, and finally a sodium ion positive electrode material with a coating amount of 14 wt % was obtained.
  • the sol water bath was heated to 90° C. to remove moisture to obtain a gel, and finally a sodium ion cathode material with a coating amount of 14 wt % was obtained.
  • the sol water bath was heated to 60° C. to remove moisture to obtain a gel, and finally a sodium ion positive electrode material with a coating amount of 14%.
  • the gel was dried at 400° C. for 7 hours to finally obtain a sodium ion cathode material with a coating amount of 14%.
  • the gel was sintered at 1000° C. for 10 hours to finally obtain a sodium ion cathode material with a coating amount of 14%.
  • the gel was sintered at 800° C. for 14 hours to finally obtain a sodium ion cathode material with a coating amount of 14%.
  • the gel was sintered at 750° C. for 12 hours to finally obtain a sodium ion cathode material with a coating amount of 14%.
  • the manganese-based positive electrode material is Na 0.67 Mn 0.67 Ni 0.33 O 2 , and finally a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • the stirring speed of the first mixing is 400r/min, the stirring time of the first mixing is 5h, and finally a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • the stirring speed of the first mixing was 350 r/min, the stirring time of the first mixing was 3 hours, and finally a sodium ion positive electrode material with a coating amount of 14% was obtained.
  • the stirring speed of the first mixing is 300r/min, the stirring time of the first mixing is 2h, and finally a sodium ion positive electrode material with a coating amount of 14% is obtained.
  • the stirring speed of the first mixing is 250 r/min, the stirring time of the first mixing is 1 h, and finally a sodium ion cathode material with a coating amount of 14% is obtained.
  • the second solution was directly mixed with the first solution to obtain a mixed solution, and finally a sodium ion cathode material with a coating amount of 14% was obtained.
  • the manganese-based cathode material is Na 0.67 MnO 2 directly used as the sodium ion cathode material.
  • the manganese-based cathode material is Na 0.67 Mn 0.67 Ni 0.33 O 2 directly as the sodium ion cathode material.
  • the first-cycle charge-discharge curve of the cylindrical sodium-ion battery of Comparative Example 1 at 2-4.1V shows that its charge specific capacity is 85mAh/g, its discharge capacity is 67mAh/g, and its irreversible capacity is 18mAh/g. From the Na 0.67 MnO of comparative example 1
  • the chemical formula of the coating layer of the sodium ion positive electrode material obtained in the above Examples 1 to 25 is LiNi 1/3 Co 1/3 Mn 1/3 O 2 , and the particle size of the sodium ion positive electrode material is basically in the range of 0.2 to 1 ⁇ m. Inside.
  • Battery assembly wind the positive electrode, negative electrode, and diaphragm together, and then carry out the electrolyte solution (the sodium salt is NaClO 4 , the organic solvent in the electrolyte solution is ethylene carbonate, propylene carbonate, and dimethyl carbonate with a volume ratio of 1 :1:1) injection to obtain a cylindrical sodium-ion battery.
  • the sodium salt is NaClO 4
  • the organic solvent in the electrolyte solution is ethylene carbonate, propylene carbonate, and dimethyl carbonate with a volume ratio of 1 :1:1
  • the present invention aims at the problem that the manganese-based positive electrode material is easily eroded by the electrolyte and the problem of sodium source consumption in the process of forming the SEI film.
  • the lithium-containing ternary material with a large capacity is used as a coating layer to coat the sodium ion positive electrode material.
  • the coating layer reduces the erosion of the electrolyte on the manganese-based cathode material; on the other hand, during the formation process, the lithium source containing lithium-containing ternary materials is used as a sacrificial agent to form a part of the SEI film, thereby reducing the corrosion resistance of the manganese-based cathode material.
  • the loss of the active sodium source in the battery improves the electrical properties such as the reversible capacity and cycle performance of the sodium ion cathode material.

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Abstract

本发明提供了一种钠离子正极材料及其制备方法、钠离子电池。该钠离子正极材料包括锰基正极材料和包覆于锰基正极材料的包覆层，锰基正极材料的化学通式为NaxMnyM1-yO2，其中，M选自Cu、Fe、Co、Ni中的任意一种，且0.5≤x≤1，0.5≤y≤1，包覆层为含锂三元材料，含锂三元材料的化学通式为LiNiaCobMncO2，0<a<1，0<b<1，0<c<1，a+b+c＝1。本申请以含锂三元材料的锂源作为牺牲剂生成部分SEI膜，从而降低了锰基正极材料中的活性钠源的损耗，进而提升了钠离子正极材料的可逆容量、循环性能等电学性能。

Description

钠离子正极材料及其制备方法、钠离子电池 技术领域
本发明涉及钠离子电池技术领域，具体而言，涉及一种钠离子正极材料及其制备方法、钠离子电池。
背景技术
锂离子电池因其能量密度高，循环寿命长在储能领域得到了广泛的应用。但锂资源在地壳中丰度较低且分布不均，随着储能领域对电池的需求量越来越大，使得锂离子电池的成本不断攀升。钠元素拥有与锂元素相似的物化性质，且钠资源丰富，价格低廉，钠离子电池也与锂离子电池的原理类似，钠离子电池被认为是新一代的高性能，低成本的二次电池技术。
锰基层状材料拥有制备简单，环境友好，比容量大等优势受到广泛关注。同时锰基正极材料在充放电过程中容易受到电解液的侵蚀，使得材料结构改变，严重影响其循环性能。另外，目前钠离子电池能量密度不及锂离子电池，在使用硬碳作为负极的情况下，化成过程中形成SEI膜会消耗大量钠源，进一步降低了活性钠源，降低了能量密度，限制了锰基材料的进一步应用。
在改善化成SEI膜对钠源的消耗方面，有正极补钠和负极补钠两种方式，通常采用负极预钠化来改善钠源的消耗，预钠化指的是将外源钠以合适的方式和形态引入电池体系，负极预钠化根据预钠化方式分为直接添加外源钠、活性添加剂预钠化、电化学预钠化和化学预钠化。以上方法都涉及到对涂布后的负极极片进行进一步处理，甚至需要直接使用金属钠对其进行预钠化，对车间环境、设备的要求较高，所需时间较长，不利于商业化应用。正极补钠如通过包覆非活性物质来隔绝锰基层状材料与电解液的侵蚀，这使得材料的循环性能得到了提升，但同时影响了其能量密度。
发明内容
本发明的主要目的在于提供一种钠离子正极材料及其制备方法、钠离子电池，以解决现有技术中的钠离子正极材料的首圈钠源消耗导致其容量较低以及循环性能较差的问题。
为了实现上述目的，根据本发明的一个方面，提供了一种钠离子正极材料，该钠离子正极材料包括锰基正极材料和包覆于锰基正极材料的包覆层，锰基正极材料的化学通式为Na xMn yM 1-yO 2，其中，M选自Cu、Fe、Co、Ni中的任意一种，且0.5≤x≤1，0.5≤y≤1，包覆层为含锂三元材料，含锂三元材料的化学通式为LiNi aCo bMn cO 2，0<a<1，0<b<1，0<c<1，a+b+c＝1。
进一步地，上述包覆层为锰基正极材料的5～20wt％，优选为10～20wt％，进一步地，优选为12～17wt％。
进一步地，上述钠离子正极材料的粒径为0.2～1μm。
根据本发明的另一个方面，提供了一种前述钠离子正极材料的制备方法，该制备方法包括：步骤S1，将包括锰基正极材料、锂源、镍源、钴源、锰源及络合剂的原料进行混合并加热，得到凝胶；步骤S2，在含氧气的气氛中，将凝胶进行烧结，得到钠离子正极材料。
进一步地，上述步骤S1包括：步骤S11，将原料混合，得到混合液；步骤S12，调节混合液的pH值，得到溶胶；步骤S13，将溶胶进行加热，得到凝胶；优选pH值为7～8，优选加热的温度为70～90℃，优选加热的方式为水浴加热，优选混合的过程包括：将锰基正极材料、锂源、镍源、钴源、锰源与水进行第一混合，形成第一溶液；将络合剂与水进行第二混合，形成第二溶液；将第二溶液滴入第一溶液中，得到混合液；优选通过氨水调节混合液的pH值，优选第一混合的搅拌转速为400～600r/min，优选第一混合的搅拌时间为3～5h，优选第二混合的搅拌转速为300～500r/min，优选第二混合的搅拌时间为1～2h。
进一步地，上述锰基正极材料、镍源、钴源、锰源中分别以各组分中所含的过渡金属离子计，锂源中以锂离子计，锰基正极材料、锂源、镍源、钴源、锰源的摩尔比为23～28:1.6～6.4:0.5～2:0.5～2:0.5～2，优选为23～28:3.2～6.4:1～2:1～2:1～2，更优选为23～28:3.84～5.44:1.2～1.7:1.2～1.7:1.2～1.7；优选锂源为碳酸锂和/或氢氧化锂，优选镍源选自醋酸镍、硫酸镍、氯化镍中的任意一种或多种，优选钴源选自醋酸钴、硫酸钴、氯化钴中的任意一种或多种，优选锰源选自醋酸锰、硫酸锰、氯化锰中的任意一种或多种。
进一步地，以各组分中所含的过渡金属离子计，镍源、钴源、锰源的总摩尔数为n，络合剂的摩尔数与n的比为1～1.1：1，优选络合剂选自柠檬酸、乙醇酸、乙酸中的任意一种或多种。
进一步地，上述烧结的温度为800～1000℃，优选烧结的时间为10～14h，优选烧结的升温速率为5～10℃/min。
进一步地，在上述烧结之前，将凝胶进行干燥，干燥的温度为400～450℃，优选干燥的时间为4～7h。
根据本发明的又一个方面，提供了一种钠离子电池，包括正极与负极，正极包括正极材料，该正极材料为前述的钠离子正极材料。
应用本发明的技术方案，本发明针对锰基正极材料易被电解液侵蚀的问题和形成SEI膜的过程中钠源消耗的问题，将容量较大的含锂三元材料作为包覆层对钠离子正极材料进行包覆，一方面通过包覆层降低了电解液对锰基正极材料的侵蚀，另一方面在化成过程中，以含锂三元材料的锂源作为牺牲剂生成部分SEI膜，从而降低了锰基正极材料中的活性钠源的损耗，进而提升了钠离子正极材料的可逆容量、循环性能等电学性能。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1示出了实施例1的圆柱型钠离子电池在2～4.1V下的首圈充放电曲线示意图。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
如背景技术所分析的，现有技术中存在钠离子正极材料的首圈钠源消耗导致其容量较低以及循环性能较差的问题，为解决该问题，本发明提供了一种钠离子正极材料及其制备方法、钠离子电池。
在本申请的一种典型的实施方式中，提供了一种钠离子正极材料，该钠离子正极材料包括锰基正极材料和包覆于锰基正极材料的包覆层，锰基正极材料的化学通式为Na xMn yM 1-yO 2，其中，M选自Cu、Fe、Co、Ni中的任意一种，且0.5≤x≤1，0.5≤y≤1，包覆层为含锂三元材料，含锂三元材料的化学通式为LiNi aCo bMn cO 2，0<a<1，0<b<1，0<c<1，a+b+c＝1。
本发明针对锰基正极材料易被电解液侵蚀的问题和形成SEI膜的过程中钠源消耗的问题，将容量较大的含锂三元材料作为包覆层对钠离子正极材料进行包覆，一方面通过包覆层降低了电解液对锰基正极材料的侵蚀，另一方面在化成过程中，以含锂三元材料的锂源作为牺牲剂生成部分SEI膜，从而降低了锰基正极材料中的活性钠源的损耗，进而提升了钠离子正极材料的可逆容量、循环性能等电学性能。
为了进一步地提高包覆层对锰基正极材料的保护作用以及降低对活性钠源的损耗，上述包覆层为锰基正极材料的5～20wt％，优选为10～20wt％，进一步地，优选为12～17wt％。
优选上述钠离子正极材料的粒径为0.2～1μm，从而更适合当前正极材料的使用要求。
在本申请的另一种典型的实施方式中，提供了一种上述钠离子正极材料的制备方法，该制备方法包括：步骤S1，将包括锰基正极材料、锂源、镍源、钴源、锰源及络合剂的原料进行混合并加热，得到凝胶；步骤S2，在含氧气的气氛中，将凝胶进行烧结，得到钠离子正极材料。
本申请的步骤S1中原料混合之后首先在溶剂中形成低粘度溶液，从而在短时间内获得分子水平的均匀性溶胶，加热之后进一步地形成分子水平的均匀混合的凝胶，该溶胶-凝胶法的制备条件温和、各组分易于控制、反应时间较短、温度可控，得到的颗粒粒径较小且均一。再经过对凝胶的烧结，使得包覆均匀、颗粒均一的钠离子正极材料。
为提高溶胶形成凝胶的效率，优选上述步骤S1包括：步骤S11，将原料混合，得到混合液；步骤S12，调节混合液的pH值，得到溶胶；步骤S13，将溶胶进行加热，得到凝胶；优选pH值为7～8，优选加热的温度为70～90℃，优选加热的方式为水浴加热，优选混合的过程 包括：将锰基正极材料、锂源、镍源、钴源、锰源与水进行第一混合，形成第一溶液；将络合剂与水进行第二混合，形成第二溶液；将第二溶滴入第一溶液中，得到混合液；优选通过氨水调节混合液的pH值，优选第一混合的搅拌转速为400～600r/min，优选第一混合的搅拌时间为3～5h，优选第二混合的搅拌转速为300～500r/min，优选第二混合的搅拌时间为1～2h。
将锰基正极材料、锂源、镍源、钴源、锰源与水进行第一混合，得到均匀的第一溶液；将络合剂与水进行第二混合，形成均匀的第二溶液；再将第二溶液滴入第一溶液中，得到均匀的混合液，优选的上述搅拌转速和时间有利于得到均一的低粘度第一溶液和第二溶液，以及将第二溶液滴入第一溶液的滴入的方式有助于使得混合液的粘度不至于突然太大，从而有利于形成分子水平的均匀混合的凝胶溶胶，加热蒸发水分之后进一步地形成分子水平的均匀混合的凝胶，再经过对凝胶的烧结，使得包覆均匀、颗粒均一的钠离子正极材料。该溶胶-凝胶法的制备条件温和、各组分易于控制、反应时间较短、温度可控，得到的颗粒粒径较小且均一。
在本申请的一种实施例中，锰基正极材料、镍源、钴源、锰源中分别以各组分中所含的过渡金属离子计，锂源中以锂离子计，上述锰基正极材料、锂源、镍源、钴源、锰源的摩尔比为23～28:1.6～6.4:0.5～2:0.5～2:0.5～2，优选为23～28:3.2～6.4:1～2:1～2:1～2，更优选为23～28:3.84～5.44:1.2～1.7:1.2～1.7:1.2～1.7；优选锂源为碳酸锂和/或氢氧化锂，优选镍源选自醋酸镍、硫酸镍、氯化镍中的任意一种或多种，优选钴源选自醋酸钴、硫酸钴、氯化钴中的任意一种或多种，优选锰源选自醋酸锰、硫酸锰、氯化锰中的任意一种或多种。
上述比例的原料及其种类有利于其在溶剂中的分散均匀性，并得到性能优良的锰基正极材料Na xMn yM 1-yO 2和包覆于该锰基正极材料的，含锂三元材料LiNi aCo bMn cO 2包覆层的量随着锂源、镍源、钴源、锰源的摩尔比变化，优选的上述锰基正极材料、锂源、镍源、钴源、锰源的摩尔比更有助于形成对Na xMn yM 1-yO 2优良包覆的LiNi aCo bMn cO 2包覆层，其中，凝胶进行烧结的过程中，锂源有挥发而导致少量的损失，因此添加稍微过量的锂源。
为提高络合剂与原料中的金属离子的络合效果，以各组分中所含的过渡金属离子计，镍源、钴源、锰源的总摩尔数为n，络合剂的摩尔数与n的比为1～1.1：1，优选上述络合剂选自柠檬酸、乙醇酸、乙酸中的任意一种或多种，其中，络合剂稍加多了虽然不会导致对钠离子正极材料电性能的降低，但是会造成其浪费，从而导致成本增高。
为尽可能地兼顾烧结的效率和包覆层的均匀性，优选上述烧结的温度为800～1000℃，优选烧结的时间为10～14h，优选烧结的升温速率为5～10℃/min。
在本申请的一种实施例中，在上述烧结之前，将凝胶进行干燥，干燥的温度为400～450℃，优选干燥的时间为4～7h。
烧结之前将凝胶进行干燥有利于排除凝胶中的水分对烧结过程的干扰作用。
在本申请的又一种典型的实施方式中，提供了一种钠离子电池，包括正极与负极，该正极包括正极材料，正极材料为上述的钠离子正极材料。
包括本申请的钠离子正极材料的钠离子电池具有更高的可逆容量和更长的寿命。
其中，钠离子电池主要包括：正极、负极、隔膜、电解液和外壳。
为进一步地提高钠离子电池的性能，优选正极的制备方法包括：
将粘结剂(聚偏氟乙烯、海藻酸钠等)加入N-甲基吡咯烷酮中，制得浓度为6％的胶液。
将本申请以上制备得到的钠离子正极材料、导电剂(石墨、炭黑、乙炔黑、石墨烯中的任意一种或多种)加入胶液中，搅拌均匀，得到粘度为4500～6500mPas·s的浆料，将该浆料涂覆在铝箔上，高温除去溶剂，辊压分切后得到正极，其中，上述钠离子正极材料、导电剂和粘结剂的质量比为97：2：1。
优选负极的制备方法包括：
将硬碳、增稠剂CMC、粘结剂SBR按比例加入去离子水中，制得浆料并涂覆在铜箔上，高温除去溶剂，辊压分切后得到负极，其中为硬碳：CMC：SBR的质量比为97:1.5:1.5。
电解液中的钠盐为NaClO 4、NaPF 6、NaTFSI中的任意一种或多种，电解液中的有机溶剂为碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸二乙酯中的任意一种或多种。
以下将结合具体实施例和对比例，对本申请的有益效果进行说明。
实施例1
将Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰按(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)摩尔比为26:4.48:1.4:1.4:1.4溶于水中进行第一混合，形成第一溶液，将柠檬酸(Na 0.67MnO 2与柠檬酸的摩尔比为26:4.2)加入水中进行第二混合，形成第二溶液，将第二溶液滴入第一溶液中，得到混合液。其中，第一混合的搅拌转速为600r/min，第一混合的搅拌时间为3h，第二混合的搅拌转速为500r/min，第二混合的搅拌时间为1h。用氨水调节混合液的pH值为7～8之间，得到溶胶。将溶胶水浴加热至80℃，除去水分，得到凝胶。将凝胶在450℃下干燥5小时。然后再将凝胶在900℃(升温速率为5～10℃/min)下烧结12小时，得到LiNi aCo bMn cO 2包覆量为14wt％的钠离子正极材料，其在2～4.1V下的首圈充放电曲线如图1所示，其充电比容量为103mAh/g，放电容量为84.5mAh/g。
实施例2
实施例2与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为26:3.84:1.2:1.2:1.2，Na 0.67MnO 2与柠檬酸的摩尔比为26:3.6，最终得到包覆量为12wt％的钠离子正极材料。
实施例3
实施例3与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为26:5.44:1.7:1.7:1.7，Na 0.67MnO 2与柠檬酸的摩尔比为26:5.1，最终得到包覆量为17wt％的钠离子正极材料。
实施例4
实施例4与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为26:3.2:1:1:1，Na 0.67MnO 2与柠檬酸的摩尔比为26:3，最终得到包覆量为10wt％的钠离子正极材料。
实施例5
实施例5与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为26:6.4:2:2:2，Na 0.67MnO 2与柠檬酸的摩尔比为26:6，最终得到包覆量为20％的钠离子正极材料。
实施例6
实施例6与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为26:1.6:0.5:0.5:0.5，Na 0.67MnO 2与柠檬酸摩尔比为26:1.5，最终得到包覆量为5％的钠离子正极材料，其在2～4.1V下的首圈充放电曲线显示其充电比容量为89.3mAh/g，放电容量为71.2mAh/g。
实施例7
实施例7与实施例1的区别在于，
Na 0.67MnO 2、氯化锂、氯化镍、氯化钴、氯化锰(Na 0.67MnO 2、氯化镍、氯化钴、氯化锰中以各组分中所含的过渡金属离子计，氯化锂中以锂离子计)的摩尔比为26:4.48:1.4:1.4:1.4，最终得到包覆量为14％的钠离子正极材料。
实施例8
实施例8与实施例1的区别在于，
络合剂为乙醇酸，最终得到包覆量为14wt％的钠离子正极材料。
实施例9
实施例9与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为23:4.48:1.4:1.4:1.4，Na 0.67MnO 2与柠檬酸摩尔比为26:4.62，最终得到包覆量为14％的钠离子正极材料。
实施例10
实施例10与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为28:4.48:1.4:1.4:1.4，Na 0.67MnO 2与柠檬酸摩尔比为26:3.78，最终得到包覆量为14％的钠离子正极材料。
实施例11
实施例11与实施例1的区别在于，
Na 0.67MnO 2、碳酸锂、醋酸镍、醋酸钴、醋酸锰(Na 0.67MnO 2、醋酸镍、醋酸钴、醋酸锰中以各组分中所含的过渡金属离子计，碳酸锂中以锂离子计)的摩尔比为30:4.48:1.4:1.4:1.4，Na 0.67MnO 2与柠檬酸摩尔比为26:6.3，最终得到包覆量为14％的钠离子正极材料。
实施例12
实施例12与实施例1的区别在于，
将溶胶水浴加热至70℃，除去水分，得到凝胶，最终得到包覆量为14wt％的钠离子正极材料。
实施例13
实施例13与实施例1的区别在于，
将溶胶水浴加热至90℃，除去水分，得到凝胶，最终得到包覆量为14wt％的钠离子正极材料。
实施例14
实施例14与实施例1的区别在于，
将溶胶水浴加热至60℃，除去水分，得到凝胶，最终得到包覆量为14％的钠离子正极材料。
实施例15
实施例15与实施例1的区别在于，
用氨水调节混合液的pH值为8～9之间，得到溶胶，最终得到包覆量为14％的钠离子正极材料。
实施例16
实施例16与实施例1的区别在于，
将凝胶在400℃下干燥7小时，最终得到包覆量为14％的钠离子正极材料。
实施例17
实施例17与实施例1的区别在于，
将凝胶在1000℃下烧结10小时，最终得到包覆量为14％的钠离子正极材料。
实施例18
实施例18与实施例1的区别在于，
将凝胶在800℃下烧结14小时，最终得到包覆量为14％的钠离子正极材料。
实施例19
实施例19与实施例1的区别在于，
将凝胶在750℃下烧结12小时，最终得到包覆量为14％的钠离子正极材料。
实施例20
实施例20与实施例1的区别在于，
锰基正极材料为Na 0.67Mn 0.67Ni 0.33O 2，最终得到包覆量为14％的钠离子正极材料。
实施例21
实施例21与实施例1的区别在于，
第一混合的搅拌转速为400r/min，第一混合的搅拌时间为5h，最终得到包覆量为14％的钠离子正极材料。
实施例22
实施例22与实施例1的区别在于，
第一混合的搅拌转速为350r/min，第一混合的搅拌时间为3h，最终得到包覆量为14％的钠离子正极材料。
实施例23
实施例23与实施例1的区别在于，
第一混合的搅拌转速为300r/min，第一混合的搅拌时间为2h，最终得到包覆量为14％的钠离子正极材料。
实施例24
实施例24与实施例1的区别在于，
第一混合的搅拌转速为250r/min，第一混合的搅拌时间为1h，最终得到包覆量为14％的钠离子正极材料。
实施例25
实施例25与实施例1的区别在于，
将第二溶液与第一溶液直接混合，得到混合液，最终得到包覆量为14％的钠离子正极材料。
对比例1
对比例1与实施例1的区别在于，
将锰基正极材料为Na 0.67MnO 2直接作为钠离子正极材料。
对比例2
对比例2与实施例20的区别在于，
将锰基正极材料为Na 0.67Mn 0.67Ni 0.33O 2直接作为钠离子正极材料。
对比例1的圆柱型钠离子电池在2～4.1V下的首圈充放电曲线显示其充电比容量为85mAh/g，放电容量为67mAh/g，不可逆容量为18mAh/g。从对比例1的Na 0.67MnO 2的充电比容量为85mAh/g到实施例1的钠离子正极材料的充电比容量103mAh/g，可见，通过本申请对锰基正极材料的包覆改性能较好地弥补首圈不可逆容量损失。
以上述实施例1至25得到的钠离子正极材料的包覆层的化学式为LiNi 1/3Co 1/3Mn 1/3O 2，钠离子正极材料的粒径基本都在0.2～1μm的范围内。
分别按照钠离子正极材料：Super P：PVDF＝97:2:1的比例加入N-甲基吡络烷酮，其中固含量为65％，搅拌均匀得到正极浆料，将正极浆料涂布在厚度为15μm的铝箔上，烘干得到正极。
按照硬碳：Super P：PVDF＝94:3:3的比例加入N-甲基吡络烷酮，其中固含量为52％，搅拌均匀得到负极浆料，将负极浆料涂布在厚度为8μm的铜箔箔上，烘干得到负极。
电池的装配：将正极、负极、隔膜一同进行卷绕，后续进行电解液(钠盐为NaClO 4，电解液中的有机溶剂为碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯的体积比为1:1:1)注入得到圆柱型钠离子电池。
在0.5C的条件下分别测试实施例1至25、对比例1、对比例2的圆柱型钠离子电池的首次放电容量、循环100周的剩余容量和循环100周的容量保持率如表1所示。
表1
Figure PCTCN2022087447-appb-000001
Figure PCTCN2022087447-appb-000002
从以上的描述中，可以看出，本发明上述的实施例实现了如下技术效果：
本发明针对锰基正极材料易被电解液侵蚀的问题和形成SEI膜的过程中钠源消耗的问题，将容量较大的含锂三元材料作为包覆层对钠离子正极材料进行包覆，一方面通过包覆层降低了电解液对锰基正极材料的侵蚀，另一方面在化成过程中，以含锂三元材料的锂源作为牺牲剂生成部分SEI膜，从而降低了锰基正极材料中的活性钠源的损耗，进而提升了钠离子正极材料的可逆容量、循环性能等电学性能。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种钠离子正极材料，其特征在于，所述钠离子正极材料包括锰基正极材料和包覆于所述锰基正极材料的包覆层，所述锰基正极材料的化学通式为Na xMn yM 1-yO 2，其中，M选自Cu、Fe、Co、Ni中的任意一种，且0.5≤x≤1，0.5≤y≤1，所述包覆层为含锂三元材料，所述含锂三元材料的化学通式为LiNi aCo bMn cO 2，0<a<1，0<b<1，0<c<1，a+b+c＝1。
  2. 根据权利要求1所述的钠离子正极材料，其特征在于，所述包覆层为所述锰基正极材料的5～20wt％，优选为10～20wt％，进一步地，优选为12～17wt％。
  3. 根据权利要求1或2所述的钠离子正极材料，其特征在于，所述钠离子正极材料的粒径为0.2～1μm。
  4. 一种权利要求1至3中任一项所述钠离子正极材料的制备方法，其特征在于，所述制备方法包括：
    步骤S1，将包括锰基正极材料、锂源、镍源、钴源、锰源及络合剂的原料进行混合并加热，得到凝胶；
    步骤S2，在含氧气的气氛中，将所述凝胶进行烧结，得到所述钠离子正极材料。
  5. 根据权利要求4所述的制备方法，其特征在于，所述步骤S1包括：
    步骤S11，将所述原料混合，得到混合液；
    步骤S12，调节所述混合液的pH值，得到溶胶；
    步骤S13，将所述溶胶进行加热，得到所述凝胶；
    优选所述pH值为7～8，优选所述加热的温度为70～90℃，优选所述加热的方式为水浴加热，
    优选所述混合的过程包括：
    将所述锰基正极材料、所述锂源、所述镍源、所述钴源、所述锰源与水进行第一混合，形成第一溶液；
    将所述络合剂与水进行第二混合，形成第二溶液；
    将所述第二溶液滴入所述第一溶液中，得到所述混合液；
    优选通过氨水调节所述混合液的pH值，优选所述第一混合的搅拌转速为400～600r/min，优选所述第一混合的搅拌时间为3～5h，优选所述第二混合的搅拌转速为300～500r/min，优选所述第二混合的搅拌时间为1～2h。
  6. 根据权利要求4或5所述的制备方法，其特征在于，所述锰基正极材料、所述镍源、所述钴源、所述锰源中分别以各组分中所含的过渡金属离子计，所述锂源中以锂离子计， 所述锰基正极材料、所述锂源、所述镍源、所述钴源、所述锰源的摩尔比为23～28:1.6～6.4:0.5～2:0.5～2:0.5～2，优选为23～28:3.2～6.4:1～2:1～2:1～2，更优选为23～28:3.84～5.44:1.2～1.7:1.2～1.7:1.2～1.7；优选所述锂源为碳酸锂和/或氢氧化锂，优选所述镍源选自醋酸镍、硫酸镍、氯化镍中的任意一种或多种，优选所述钴源选自醋酸钴、硫酸钴、氯化钴中的任意一种或多种，优选所述锰源选自醋酸锰、硫酸锰、氯化锰中的任意一种或多种。
  7. 根据权利要求4所述的制备方法，其特征在于，以各组分中所含的过渡金属离子计，所述镍源、所述钴源、所述锰源的总摩尔数为n，所述络合剂的摩尔数与所述n的比为1～1.1：1，优选所述络合剂选自柠檬酸、乙醇酸、乙酸中的任意一种或多种。
  8. 根据权利要求4至7中任一项所述的制备方法，其特征在于，所述烧结的温度为800～1000℃，优选所述烧结的时间为10～14h，优选所述烧结的升温速率为5～10℃/min。
  9. 根据权利要求4至7中任一项所述的制备方法，其特征在于，在所述烧结之前，将所述凝胶进行干燥，所述干燥的温度为400～450℃，优选所述干燥的时间为4～7h。
  10. 一种钠离子电池，包括正极与负极，所述正极包括正极材料，其特征在于，所述正极材料为权利要求1至9中任一项所述的钠离子正极材料。
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