WO2024037261A1 - 一种双层包覆锂钠复合富锂锰基正极材料的制备方法 - Google Patents

一种双层包覆锂钠复合富锂锰基正极材料的制备方法 Download PDF

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WO2024037261A1
WO2024037261A1 PCT/CN2023/107204 CN2023107204W WO2024037261A1 WO 2024037261 A1 WO2024037261 A1 WO 2024037261A1 CN 2023107204 W CN2023107204 W CN 2023107204W WO 2024037261 A1 WO2024037261 A1 WO 2024037261A1
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lithium
double
sodium
layer coated
rich manganese
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PCT/CN2023/107204
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English (en)
French (fr)
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张苗
阮丁山
李长东
毛林林
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广东邦普循环科技有限公司
湖南邦普循环科技有限公司
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Priority to PCT/CN2023/107204 priority Critical patent/WO2024037261A1/zh
Priority to CN202380010134.9A priority patent/CN117136443A/zh
Publication of WO2024037261A1 publication Critical patent/WO2024037261A1/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
    • H01M4/04—Processes of manufacture in general
    • 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
    • H01M4/48—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 disclosure relates to the technical field of cathode material preparation, and in particular to a preparation method of a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • cathode materials The use of high-capacity, high-voltage, and low-cost cathode materials is one of the key factors in obtaining low-cost, high-energy power batteries.
  • the discharge capacity of lithium-rich manganese-based cathode materials is as high as 300mAh/g, which is much higher than the discharge capacity of cathode materials such as lithium iron phosphate cathode materials and ternary cathode materials. Therefore, lithium-rich manganese-based cathode materials It is considered to be an ideal choice for a new generation of high energy density power batteries.
  • lithium-rich manganese-based cathode materials use manganese as the main matrix element and have relatively small demand for higher-priced metal elements such as nickel and cobalt, the proportion of lithium used in the synthesis process is high, and lithium The price is relatively high, so the preparation cost of lithium-rich manganese-based cathode materials is still high.
  • low-cost sodium salts are used to replace part of the high-cost lithium salts to synthesize lithium-sodium composite lithium-rich manganese-based cathode materials, which can ensure that the cathode materials maintain high performance and have cost advantages.
  • the purpose of this disclosure is to provide a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material, which has simple steps and low cost, and the prepared cathode material has good electrochemical properties.
  • a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material including the following steps:
  • S2 Mix the nickel manganese hydroxide precursor obtained in S1 with lithium salt, sodium salt and dopant evenly and then sinter it to obtain a sintered product;
  • S3 Place the one-burned product obtained in S2 into an ammonia solution to react, then filter, wash and dry to obtain the dried product;
  • the nickel-manganese hydroxide precursor is mixed with lithium salt, sodium salt, Dopants are blended and then sintered once. Part of the low-cost sodium salt is used to replace the high-cost lithium salt. This can form a sodium metal oxide with a large crystal plane spacing, which can stabilize the material structure and improve the bulk phase dynamics of the material.
  • the role of performance can ensure that the material has high performance and cost advantages; and the dopant can effectively promote the diffusion of lithium ions and sodium ions into the material during the sintering process, prevent accumulation on the surface of the first-fired product, and reduce the surface area of the first-fired product. Residual alkali. Then, the present disclosure performs alkali washing on the first-burning product in an ammonia solution.
  • the ammonia reacts with the nickel in the first-burning product without reacting with the manganese in the first-burning product; after the first-burning product is immersed in the ammonia solution, the material will A low-nickel and high-manganese product is formed on the surface, and the dried product is obtained through suction filtration, washing, and drying; then, the dried product is blended with fluoride and then sintered twice.
  • the low-nickel and high-manganese product is converted into It is a spinel phase, forming a spinel phase coating layer, and at the same time, fluoride forms a fluoride coating layer on the surface of the spinel phase coating layer, thereby forming a double-layer coating of spinel phase and fluoride; tip
  • the spar phase can provide a three-dimensional channel for the migration of Li + and improve the material interface dynamic properties, while the fluoride coating can reduce the irreversible loss of oxygen, ultimately achieving the purpose of improving material performance.
  • the nickel manganese hydroxide precursor in S1 is Ni x Mn 1-x (OH) 2 , where 0.35 ⁇ x ⁇ 0.4.
  • the lithium salt in S2 is Li 2 CO 3 .
  • the sodium salt in S2 is one of NaHCO 3 , NaCOOH, CH 3 COONa, CH 3 CH 2 COONa, Na 2 C 2 O 4 and C 6 H 5 Na 3 O 7 .
  • the above types of sodium salts have low melting points and can effectively promote the diffusion of sodium ions into the material under the action of dopants during the sintering process and reduce surface residual alkali.
  • the dopant in S2 is one of Nb 2 O 5 nanopowder, Co 3 O 4 nanopowder, WO 3 nanopowder, and La 2 O 3 nanopowder.
  • the above-mentioned solid phase dopants can effectively promote the diffusion of lithium ions and sodium ions in the lithium salt and sodium salt into the material during the sintering process, thereby reducing the residual alkali on the surface of the first-sintered product.
  • the molar ratio of the sum of lithium and sodium elements to the sum of nickel and manganese elements is 1.3 to 1.4:1. If the molar ratio of lithium and sodium elements is too low, the electrochemical performance of the cathode material cannot be satisfied; if the molar ratio of lithium and sodium elements is too high, the residual alkali content on the surface of the material will easily be too high, affecting the performance of the cathode material. Electrochemical properties.
  • the molar ratio of sodium element to the sum of lithium and sodium elements in S2 is 0.1 to 0.15:1. If the molar content of sodium element accounts for too low a proportion of the sum of moles of lithium and sodium elements, the amount of lithium element will be large and the cost will be high; if the molar content of sodium element accounts for too high a proportion of the sum of moles of lithium and sodium elements, the lithium element will The dosage is low and the electrochemical performance of the cathode material cannot be satisfied.
  • the mass of the dopant is 0.3% to 0.5% of the mass of the nickel manganese hydroxide precursor. If the mass fraction of the added dopant is too low relative to the mass of the nickel manganese hydroxide precursor, the dopant will not be able to effectively promote the diffusion of lithium ions and sodium ions into the material during the sintering process, resulting in residual alkali on the surface of the material. The higher the content, the lower the electrochemical performance.
  • sintering in S2 is carried out in an oxygen atmosphere at a sintering temperature of 900-1000°C and a sintering time of 15-20h.
  • the concentration of ammonia solution in S3 is 0.5-1 mol/L, and the reaction time is 30-60 minutes.
  • the concentration of the ammonia solution is within this range, which facilitates the reaction between the first-fired product and the ammonia to form low-nickel and high-manganese products on the surface of the material, thereby facilitating the conversion to a moderately thick spinel phase coating layer during the sintering process of S4.
  • the concentration of the ammonia solution is too low, it will be difficult to form low-nickel and high-manganese products after the first-sintered product is immersed in ammonia, resulting in a thin spinel phase coating layer formed by subsequent sintering transformation, which cannot provide sufficient three-dimensional space for the migration of Li + channel, and the effect on improving the dynamic properties of the material interface is not obvious. If the concentration of ammonia solution is too high, the spinel phase coating layer formed by subsequent sintering transformation will be too thick, which is also not conducive to the migration of Li + .
  • deionized water is used to wash until the pH value of the filtered water becomes neutral.
  • the drying temperature in S3 is 60 to 80°C and the drying time is 12 to 24 hours.
  • the fluoride in S4 is one of AlF 3 nanopowder, ZrF 4 nanopowder, and CaF 2 nanopowder. Coating with the above-mentioned fluoride can reduce the irreversible loss of oxygen, improve the first discharge specific capacity and first Coulombic efficiency of the cathode material, and achieve the purpose of improving material performance.
  • the mass of fluoride is 0.1% to 0.3% of the mass of the dried product.
  • sintering in S4 is carried out in an oxygen atmosphere, the sintering temperature is 600-800°C, and the sintering time is 8-10h.
  • the present disclosure has the following advantages:
  • the process used in this disclosure can not only be used in lithium-rich manganese-based cathode material systems, but can also be applied to other cathode material systems, and its applicability is very wide.
  • Figure 1 is a schematic structural diagram of an embodiment of the double-layer-coated lithium-sodium composite lithium-rich manganese-based cathode material of the present disclosure
  • Figure 2 is an SEM image of the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Example 1;
  • Figure 3 is an SEM image of the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Example 2;
  • Figure 4 is an SEM image of the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Comparative Example 1;
  • Figure 5 is an SEM image of the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Comparative Example 2;
  • Figure 6 is an SEM image of the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Comparative Example 4.
  • Figure 7 is an SEM image of the double-layer-coated lithium-sodium composite lithium-rich manganese-based cathode material obtained in Comparative Example 6.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material, which includes the following specific steps:
  • NiSO 4 and MnSO 4 with a certain stoichiometric ratio are used as nickel source and manganese source, NH 4 OH is used as complexing agent, and NaOH is used as precipitating agent , Ni 0.35 Mn 0.65 (OH) 2 precursor was prepared by co-precipitation method.
  • S2 Mix the Ni 0.35 Mn 0.65 (OH) 2 precursor obtained in S1 with Li 2 CO 3 , NaHCO 3 , and Nb 2 O 5 nanopowders.
  • the sum of lithium and sodium elements and the sum of nickel and manganese elements are The molar ratio is 1.35:1; the molar ratio of the sum of sodium element and lithium sodium element is 0.1:1; the mass of Nb 2 O 5 nanopowder is 0.3% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor.
  • S3 Place the first-burned product obtained in S2 into a 1 mol/L ammonia solution for 30 minutes.
  • the alkali-washed product is filtered and washed with deionized water until the pH value of the filtered water is neutral, and then placed in an oven at 80°C. Bake for 12 hours to obtain the dried product;
  • S4 Mix the dried product obtained in S3 evenly with AlF 3 nanopowder, where the mass of AlF 3 nanopowder is 0.2% of the mass of the dried product; then place it in an oxygen atmosphere, sinter at 450°C for 8 hours, and cool to room temperature to obtain
  • the finished material is the double-layer-coated lithium-sodium composite lithium-rich manganese-based cathode material of this embodiment.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the nickel manganese hydroxide precursor prepared in S1 is Ni 0.40 Mn 0.60 (OH) 2 .
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the sintering temperature in S2 is 1000°C.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the mass of Nb 2 O 5 nanopowder is 0.1% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the mass of Nb 2 O 5 nanopowder is 0.5% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the dopant Nb 2 O 5 nanopowder is replaced with Co 3 O 4 nanopowder.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the dopant Nb 2 O 5 nanopowder is replaced with WO 3 nanopowder.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the dopant Nb 2 O 5 nanopowder is replaced with La 2 O 3 nanopowder.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the first-burned product is washed with alkali in an ammonia solution for 60 minutes.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the concentration of ammonia solution is 0.5mol/L.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the mass of AlF 3 nanopowder is 0.1% of the mass of the dried product.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the mass of AlF 3 nanopowder is 0.3% of the mass of the dried product.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the sintering time is 10h.
  • This embodiment provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the sintering time is when the sintering temperature is 800°C.
  • This comparative example provides a method for preparing a double-layer coated lithium-rich manganese-based cathode material, including the following specific steps:
  • NiSO 4 and MnSO 4 with a certain stoichiometric ratio are used as nickel source and manganese source, NH 4 OH is used as complexing agent, and NaOH is used as precipitating agent , Ni 0.35 Mn 0.65 (OH) 2 precursor was prepared by co-precipitation method.
  • S2 Mix the Ni 0.35 Mn 0.65 (OH) 2 precursor obtained in S1 with Li 2 CO 3 and Nb 2 O 5 nanopowders. In the mixture, the molar ratio of the sum of lithium elements and nickel manganese elements is 1.35:1. ; The mass of Nb 2 O 5 nanopowder is 0.3% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor. After mixing evenly, place it in an oxygen atmosphere and sinter at 900°C for 15 hours. After the sintering is completed, cool to room temperature to obtain a sintered product.
  • S3 Place the first-burned product obtained in S2 into a 1 mol/L ammonia solution for 30 minutes.
  • the alkali-washed product is filtered and washed with deionized water until the pH value of the filtered water is neutral, and then placed in an oven at 80°C. Bake for 12 hours to obtain the dried product;
  • S4 Mix the dried product obtained in S3 evenly with AlF 3 nanopowder, where the mass of AlF 3 nanopowder is 0.2% of the mass of the dried product; then place it in an oxygen atmosphere, sinter at 450°C for 8 hours, and cool to room temperature to obtain
  • the finished material is the double-layer coated lithium-rich manganese-based cathode material of this comparative example.
  • This comparative example provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This comparative example provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • This comparative example provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material, which includes the following specific steps:
  • NiSO 4 and MnSO 4 with a certain stoichiometric ratio are used as nickel source and manganese source, NH 4 OH is used as complexing agent, and NaOH is used as precipitating agent , Ni 0.35 Mn 0.65 (OH) 2 precursor was prepared by co-precipitation method.
  • S2 Mix the Ni 0.35 Mn 0.65 (OH) 2 precursor obtained in S1 with Li 2 CO 3 and NaHCO 3 evenly, where the mixture Among them, the molar ratio of the sum of lithium and sodium elements to the sum of nickel and manganese elements is 1.35:1; the molar ratio of the sum of sodium elements and lithium and sodium elements is 0.1:1. After mixing evenly, it is placed in an oxygen atmosphere and sintered at 900°C for 15 hours. After the sintering is completed, it is cooled to room temperature to obtain a sintered product.
  • S3 Place the first-burned product obtained in S2 into a 1 mol/L ammonia solution for 30 minutes.
  • the alkali-washed product is filtered and washed with deionized water until the pH value of the filtered water is neutral, and then placed in an oven at 80°C. Bake for 12 hours to obtain the dried product;
  • S4 Mix the dried product obtained in S3 evenly with AlF 3 nanopowder, where the mass of AlF 3 nanopowder is 0.2% of the mass of the dried product; then place it in an oxygen atmosphere, sinter at 450°C for 8 hours, and cool to room temperature to obtain
  • the finished material is the double-layer-coated lithium-sodium composite lithium-rich manganese-based cathode material of this comparative example.
  • This comparative example provides a method for preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material.
  • the difference between the preparation method and Example 1 is:
  • the dopant Nb 2 O 5 nanopowder is replaced with MgO nanopowder.
  • This comparative example provides a method for preparing a lithium-sodium composite lithium-rich manganese-based cathode material, which includes the following specific steps:
  • NiSO 4 and MnSO 4 with a certain stoichiometric ratio are used as nickel source and manganese source, NH 4 OH is used as complexing agent, and NaOH is used as precipitating agent , Ni 0.35 Mn 0.65 (OH) 2 precursor was prepared by co-precipitation method.
  • S2 Mix the Ni 0.35 Mn 0.65 (OH) 2 precursor obtained in S1 with Li 2 CO 3 , NaHCO 3 , and Nb 2 O 5 nanopowders.
  • the sum of lithium and sodium elements and the sum of nickel and manganese elements are The molar ratio is 1.35:1; the molar ratio of the sum of sodium element and lithium sodium element is 0.1:1; the mass of Nb 2 O 5 nanopowder is 0.3% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor.
  • S3 Mix the first-fired product obtained from S2 evenly with AlF 3 nanopowder, where the mass of AlF 3 nanopowder is 0.2% of the mass of the dried product; then place it in an oxygen atmosphere, sinter at 450°C for 8 hours, and cool to room temperature to obtain
  • the finished material is the lithium-sodium composite lithium-rich manganese-based positive electrode material of this comparative example.
  • Comparative Example 6 that is, there is no ammonia reaction step, that is, S3 of Example 1 is not performed.
  • This comparative example provides a method for preparing a lithium-sodium composite lithium-rich manganese-based cathode material, which includes the following specific steps:
  • NiSO 4 and MnSO 4 with a certain stoichiometric ratio are used as nickel source and manganese source, NH 4 OH is used as complexing agent, and NaOH is used as precipitating agent , Ni 0.35 Mn 0.65 (OH) 2 was prepared by co-precipitation method Precursor.
  • S2 Mix the Ni 0.35 Mn 0.65 (OH) 2 precursor obtained in S1 with Li 2 CO 3 , NaHCO 3 , and Nb 2 O 5 nanopowders.
  • the sum of lithium and sodium elements and the sum of nickel and manganese elements are The molar ratio is 1.35:1; the molar ratio of the sum of sodium element and lithium sodium element is 0.1:1; the mass of Nb 2 O 5 nanopowder is 0.3% of the mass of Ni 0.35 Mn 0.65 (OH) 2 precursor.
  • S3 Place the first-burned product obtained in S2 into a 1 mol/L ammonia solution for 30 minutes.
  • the alkali-washed product is filtered and washed with deionized water until the pH value of the filtered water is neutral, and then placed in an oven at 80°C. Bake for 12 hours to obtain the dried product;
  • Comparative Example 7 the difference between Comparative Example 7 and Example 1 is that there is no fluoride coating.
  • the finished products that is, the cathode materials prepared in Examples 1-24 and Comparative Examples 1-7 were respectively subjected to electrochemical performance tests, and button batteries were used for the electrochemical performance tests.
  • the working electrode is made by mixing active material, conductive carbon, and polyvinylidene fluoride in deionized water at a mass ratio of 95:2:3 and then coating them on copper foil.
  • the counter electrode uses sodium foil.
  • the electrolyte is 1 mol/L NaClO4 dissolved in a mixed solvent of EC/DEC (volume ratio 1:1) and 3wt% LiDFOB is added.
  • the separator is a PP/PE/PP composite membrane. Assembling the button cells takes place in a glove box with oxygen and water levels below 1 ppm.
  • the electrochemical performance test of the battery was performed on an electrochemical workstation.
  • the test voltage is 2.3-4.55V, and the current density is 1/3C. Please refer to Table 3 for test results
  • the data of Examples 1 and 2 show that in the process of preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material, increasing the nickel content in the nickel-manganese hydroxide precursor will reduce the first time of the material. Reversible specific capacity and first coulombic efficiency.
  • the data of Examples 1, 3, 4, 5, 6, 23, and 24 show that in the process of preparing a double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material, the first firing temperature (i.e., the sintering temperature in S2), The lithium ratio, sodium ratio, and secondary firing temperature (i.e., the sintering temperature in S4) will all affect the performance of the finished material.
  • the data of Examples 1, 7, 8, 9, 10, 11 and Comparative Examples 1, 2, and 3 show that the finished material obtained without adding sodium salt or adding high melting point sodium salt in the first burning process (i.e. S2) has the first
  • the reversible specific capacities are all lower than the first reversible specific capacity of the finished material obtained by adding low melting point sodium salt in the first burning process (i.e. S2) of the present disclosure.
  • the data of Examples 1, 12, 13, 14, 15, 16 and Comparative Examples 4 and 5 show that not adding or not adding appropriate dopants during the first firing process (i.e. S2) will significantly reduce the first reversibility ratio of the finished material. capacity.
  • the data of Examples 1, 17, 18 and Comparative Example 6 show that the first calcined product is not subjected to an alkali washing reaction in an ammonia aqueous solution, and the first reversible specific capacity of the finished material obtained is lower than the first time reversible specific capacity of the finished material after the alkali washing reaction of the present disclosure. Reversible specific capacity.
  • the data of Examples 1, 19, 20, 21, 22 and Comparative Example 7 show that the material of the present disclosure can significantly improve the first discharge specific capacity and first Coulombic efficiency of the finished material after being coated with fluoride.
  • the preparation method of the double-layer coated lithium sodium composite lithium-rich manganese-based cathode material according to the present disclosure In the prepared double-layer coated lithium sodium composite lithium-rich manganese-based cathode material, from the inside to the outside They are lithium sodium composite lithium-rich manganese-based material, spinel phase coating layer, and fluoride coating layer. Please refer to Figures 2 to 7.
  • the double-layer coated lithium-sodium composite lithium-rich manganese-based cathode material prepared in the embodiment of the present disclosure has good morphology and large particles; the spinel phase and fluoride double-layer coating formed, Improve the electrochemical performance of the material; the spinel phase can provide a three-dimensional channel for the migration of Li + and improve the material interface dynamics, while the fluoride coating can reduce the irreversible loss of oxygen, ultimately achieving the purpose of improving the material performance.

Abstract

一种双层包覆锂钠复合富锂锰基正极材料的制备方法，涉及正极材料制备技术领域。包括以下步骤：S1：利用共沉淀法制备镍锰氢氧化物前驱体；S2：将S1得到的镍锰氢氧化物前驱体，与锂盐、钠盐、掺杂剂混合均匀后进行烧结，得到一烧产物；S3：将S2得到的一烧产物置于氨水溶液中反应，然后抽滤、洗涤、烘干，得到烘干产物；S4：将S3得到的烘干产物与氟化物混合均匀后进行烧结，得到所述双层包覆锂钠复合富锂锰基正极材料。通过选用低熔点钠盐和掺杂剂，可有效促进钠离子向材料内部扩散，同时，使用碱洗及氟化物包覆工艺，形成尖晶石相和氟化物双层包覆，最终达到提升材料性能的目的。

Description

一种双层包覆锂钠复合富锂锰基正极材料的制备方法 技术领域
本公开涉及正极材料制备技术领域，特别是涉及一种双层包覆锂钠复合富锂锰基正极材料的制备方法。
背景技术
在中国“双碳”战略目标和能源结构调整的背景下，中国新能源车行业在近几年得到快速发展，尽管如此，新能源汽车占中国汽车总量的比率仍然较低，相当一部分消费者对新能源车仍持观望态度。提升新能源车动力电池的能量密度，同时降低动力电池的瓦时成本是新能源车进一步发展的重点。
使用高容量、高电压、低成本的正极材料，是获得低成本高能量动力电池的关键因素之一。目前已知的正极材料中，富锂锰基正极材料的放电容量高达300mAh/g，远高于磷酸铁锂正极材料、三元正极材料等正极材料的放电容量，因此，富锂锰基正极材料被认为是新一代高能量密度动力电池的理想之选。
然而，富锂锰基正极材料虽然以锰作为主要基体元素，对于镍、钴等价格较高的金属元素需求量相对较少，但其合成过程中所使用的锂元素的配比较高，而锂的价格相对较高，因此富锂锰基正极材料的制备成本仍然较高。在相关技术中，用低成本的钠盐替代部分高成本的锂盐，合成锂钠复合富锂锰基正极材料，可以保证正极材料保持高性能的同时兼具成本优势。但是，由于钠离子的离子半径(0.113nm)大于锂离子的离子半径(0.076nm)，导致在固相烧结过程中，钠离子难以向材料内部扩散而在材料表面堆积，使得材料表面残碱过高，可逆比容量降低。
发明内容
基于此，本公开的目的在于，提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，该方法步骤简单，成本低，制备的正极材料具有较好的电化学性能。
一种双层包覆锂钠复合富锂锰基正极材料的制备方法，包括以下步骤：
S1：利用共沉淀法制备镍锰氢氧化物前驱体；
S2：将S1得到的镍锰氢氧化物前驱体，与锂盐、钠盐、掺杂剂混合均匀后进行烧结，得到一烧产物；
S3：将S2得到的一烧产物置于氨水溶液中反应，然后抽滤、洗涤、烘干，得到烘干产物；
S4：将S3得到的烘干产物与氟化物混合均匀后进行烧结，得到所述双层包覆锂钠复合 富锂锰基正极材料。
本公开所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，在制备镍锰氢氧化物前驱体后，将所述镍锰氢氧化物前驱体与锂盐、钠盐、掺杂剂共混后一次烧结，其中，用部分低成本的钠盐替代高成本的锂盐，可形成晶面间距较大的钠金属氧化物，起到稳定材料结构、改善材料体相动力学性能的作用，可以保证材料高性能的同时兼具成本优势；而掺杂剂可以有效促进锂离子和钠离子在烧结过程中向材料内部扩散，防止在一烧产物表面堆积，降低一烧产物表面残碱。然后，本公开通过将一烧产物在氨水溶液中进行碱洗，氨水与一烧产物中的镍进行反应，而不会与一烧产物中的锰反应；一烧产物浸入氨水溶液后会在材料表面形成低镍高锰产物，通过抽滤、洗涤、烘干获得烘干产物；随后，将烘干产物与氟化物共混后二次烧结，在烧结过程中，所述低镍高锰产物转化为尖晶石相，形成尖晶石相包覆层，同时氟化物在尖晶石相包覆层表面形成氟化物包覆层，从而形成尖晶石相和氟化物的双层包覆；尖晶石相能为Li+的迁移提供三维通道，改善材料界面动力学性能，而氟化物包覆可降低氧的不可逆损失，最终达到提升材料性能的目的。
在一个方案中，S1中的镍锰氢氧化物前驱体为NixMn1-x(OH)2，其中0.35≤x≤0.4。
在一个方案中，S2中的锂盐为Li2CO3。
在一个方案中，S2中的钠盐为NaHCO3、NaCOOH、CH3COONa、CH3CH2COONa、Na2C2O4、C6H5Na3O7中的一种。上述种类的钠盐，其熔点低，能够在烧结过程中，在掺杂剂的作用下有效促进钠离子向材料内部扩散，降低表面残碱。
在一个方案中，S2中的掺杂剂为Nb2O5纳米粉末、Co3O4纳米粉末、WO3纳米粉末、La2O3纳米粉末中的一种。上述固相掺杂剂可以有效促进锂盐和钠盐中的锂离子和钠离子在烧结过程中向材料内部扩散，进而起到降低一烧产物表面残碱的作用。
在一个方案中，S2中，锂钠元素之和与镍锰元素之和的摩尔比为1.3～1.4:1。若锂钠元素的摩尔之和占比过低，正极材料的电化学性能得不到满足；若锂钠元素的摩尔之和占比过高，则容易导致材料表面的残碱含量过高，影响电化学性能。
在一个方案中，S2中，钠元素与锂钠元素之和的摩尔比为0.1～0.15:1。若钠元素的摩尔含量锂钠元素摩尔之和的占比过低，则锂元素的用量大，成本高；若若钠元素的摩尔含量锂钠元素摩尔之和的占比过高，则锂元素的用量低，正极材料的电化学性能得不到满足。
在一个方案中，S2中，掺杂剂的质量是镍锰氢氧化物前驱体质量的0.3％～0.5％。若加入的掺杂剂的质量相对于镍锰氢氧化物前驱体质量的质量分数太低，则在烧结过程中掺杂剂不能有效促进锂离子和钠离子向材料内部扩散，导致材料表面残碱含量高，电化学性能降低。
在一个方案中，S2中的烧结在氧气气氛中进行，烧结温度为900-1000℃，烧结时间为 15-20h。
在一个方案中，S3中氨水溶液的浓度为0.5～1mol/L，反应时间为30～60min。氨水溶液的浓度在此范围内，便于一烧产物与氨水反应，在材料表面形成低镍高锰产物，从而便于在S4的烧结的过程中转换形成厚度适中的尖晶石相包覆层，若氨水溶液的浓度过低，则一烧产物浸于氨水后，难以形成低镍高锰产物，导致后续烧结转化形成的尖晶石相包覆层较薄，无法为Li+的迁移提供充足的三维通道，且对于改善材料界面动力学性能的效果不明显。若氨水溶液的浓度过高，则后续烧结转化形成的尖晶石相包覆层过厚，同样不利于Li+的迁移。
在一个方案中，S3中，采用去离子水洗涤至滤水pH值呈中性。
在一个方案中，S3中的烘干温度为60～80℃，时间为12～24h。
在一个方案中，S4中的氟化物为AlF3纳米粉末、ZrF4纳米粉末、CaF2纳米粉末中的一种。采用上述的氟化物进行包覆，可降低氧的不可逆损失，提高正极材料的首次放电比容量和首次库伦效率，达到提升材料性能的目的。
在一个方案中，S4中，氟化物的质量为烘干产物质量的0.1％～0.3％。
在一个方案中，S4中的烧结在氧气气氛中进行，烧结温度为600-800℃，烧结时间为8-10h。
本公开相较于现有技术具有以下优点：
1、从技术原理角度说，在富锂锰基正极材料合成过程中使用部分钠盐替代锂盐可形成晶面间距较大的钠金属氧化物，起到稳定材料结构，改善材料体相动力学性能的作用；通过选用低熔点钠盐和固相掺杂剂可有效促进钠离子在烧结过程中向材料内部扩散，同时，创新性地使用碱洗及氟化物包覆工艺，可进一步降低材料表面残碱并形成尖晶石相和氟化物双层包覆，改善材料界面动力学性能并降低氧的不可逆损失，最终达到提升材料性能的目的。
2、从成本角度说，在富锂锰基正极材料合成过程中使用部分低成本钠源替代锂源可显著降低材料的原材料成本，提升材料的经济性。
3、本公开中使用工艺不仅可以使用在富锂锰基正极材料体系中，也可以应用到其它正极材料体系中，适用性十分广泛。
附图说明
图1为本公开的双层包覆锂钠复合富锂锰基正极材料的一种实施方式的结构示意图；
图2为实施例1所得的双层包覆锂钠复合富锂锰基正极材料的SEM图；
图3为实施例2所得的双层包覆锂钠复合富锂锰基正极材料的SEM图；
图4为对比例1所得的双层包覆锂钠复合富锂锰基正极材料的SEM图；
图5为对比例2所得的双层包覆锂钠复合富锂锰基正极材料的SEM图；
图6为对比例4所得的双层包覆锂钠复合富锂锰基正极材料的SEM图；
图7为对比例6所得的双层包覆锂钠复合富锂锰基正极材料的SEM图。
具体实施方式
下面结合实施例和对比例对本公开做进一步的说明，需要表明的是，下述实施例仅是为了解释本公开，并不对其内容进行限定。
实施例1
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，包括以下具体步骤：
S1：以一定化学计量数之比(Ni元素和Mn元素的摩尔比为35:65)的NiSO4和MnSO4为镍源和锰源，以NH4OH为络合剂，以NaOH为沉淀剂，通过共沉淀法制备Ni0.35Mn0.65(OH)2前驱体。
S2：将S1得到的Ni0.35Mn0.65(OH)2前驱体与Li2CO3、NaHCO3、Nb2O5纳米粉末混合均匀，其中混合物中，锂钠元素之和与镍锰元素之和的摩尔比为1.35：1；钠元素与锂钠元素之和的摩尔比0.1：1；Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.3％。混合均匀后置于氧气气氛中，在900℃烧结15h，烧结完成后冷却至室温得到一烧产物。
S3：将S2得到的一烧产物置于1mol/L的氨水溶液中碱洗30min，碱洗产物通过抽滤、去离子水洗涤，洗涤至滤水pH值呈中性，然后在80℃烘箱中烘烤12h，得到烘干产物；
S4：将S3得到的烘干产物与AlF3纳米粉末混合均匀，其中AlF3纳米粉末的质量为烘干产物质量的0.2％；然后置于氧气气氛中，在450℃烧结8h，冷却至室温得到成品材料，即本实施例的双层包覆锂钠复合富锂锰基正极材料。
实施例2
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S1中制备的镍锰氢氧化物前驱体为Ni0.40Mn0.60(OH)2。
实施例3
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中的烧结温度为1000℃。
实施例4
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，锂钠元素之和与镍锰元素之和的摩尔比为1.3：1。
实施例5
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，锂钠元素之和与镍锰元素之和的摩尔比为1.4：1。
实施例6
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，钠元素与锂钠元素之和的摩尔比0.15：1。
实施例7
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为NaCOOH。
实施例8
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为CH3COONa。
实施例9
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为CH3CH2COONa。
实施例10
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为Na2C2O4。
实施例11
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为C6H5Na3O7。
实施例12
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.1％。
实施例13
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.5％。
实施例14
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将掺杂剂Nb2O5纳米粉末替换为Co3O4纳米粉末。
实施例15
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将掺杂剂Nb2O5纳米粉末替换为WO3纳米粉末。
实施例16
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将掺杂剂Nb2O5纳米粉末替换为La2O3纳米粉末。
实施例17
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S3中，一烧产物置于氨水溶液中碱洗60min。
实施例18
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S3中，氨水溶液浓度为0.5mol/L。
实施例19
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，AlF3纳米粉末的质量为烘干产物质量的0.1％。
实施例20
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，AlF3纳米粉末的质量为烘干产物质量的0.3％。
实施例21
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，将氟化物AlF3纳米粉末替换为ZrF4纳米粉末。
实施例22
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，将氟化物AlF3纳米粉末替换为CaF2纳米粉末。
实施例23
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，烧结时间为10h。
实施例24
本实施例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S4中，烧结时间为烧结温度为800℃。
对比例1
本对比例提供一种双层包覆富锂锰基正极材料的制备方法，包括以下具体步骤：
S1：以一定化学计量数之比(Ni元素和Mn元素的摩尔比为35:65)的NiSO4和MnSO4为镍源和锰源，以NH4OH为络合剂，以NaOH为沉淀剂，通过共沉淀法制备Ni0.35Mn0.65(OH)2前驱体。
S2：将S1得到的Ni0.35Mn0.65(OH)2前驱体与Li2CO3和Nb2O5纳米粉末混合均匀，其中混合物中，锂元素与镍锰元素之和的摩尔比为1.35：1；Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.3％。混合均匀后置于氧气气氛中，在900℃烧结15h，烧结完成后冷却至室温得到一烧产物。
S3：将S2得到的一烧产物置于1mol/L的氨水溶液中碱洗30min，碱洗产物通过抽滤、去离子水洗涤，洗涤至滤水pH值呈中性，然后在80℃烘箱中烘烤12h，得到烘干产物；
S4：将S3得到的烘干产物与AlF3纳米粉末混合均匀，其中AlF3纳米粉末的质量为烘干产物质量的0.2％；然后置于氧气气氛中，在450℃烧结8h，冷却至室温得到成品材料，即本对比例的双层包覆富锂锰基正极材料。
即对比例1与实施例1的区别在于S2中未加入钠盐。
对比例2
本对比例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为高熔点的Na2CO3。
对比例3
本对比例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将钠盐NaHCO3替换为Na2SO3。
对比例4
本对比例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，包括以下具体步骤：
S1：以一定化学计量数之比(Ni元素和Mn元素的摩尔比为35:65)的NiSO4和MnSO4为镍源和锰源，以NH4OH为络合剂，以NaOH为沉淀剂，通过共沉淀法制备Ni0.35Mn0.65(OH)2前驱体。
S2：将S1得到的Ni0.35Mn0.65(OH)2前驱体与Li2CO3和NaHCO3混合均匀，其中混合物 中，锂钠元素之和与镍锰元素之和的摩尔比为1.35：1；钠元素与锂钠元素之和的摩尔比为0.1：1。混合均匀后置于氧气气氛中，在900℃烧结15h，烧结完成后冷却至室温得到一烧产物。
S3：将S2得到的一烧产物置于1mol/L的氨水溶液中碱洗30min，碱洗产物通过抽滤、去离子水洗涤，洗涤至滤水pH值呈中性，然后在80℃烘箱中烘烤12h，得到烘干产物；
S4：将S3得到的烘干产物与AlF3纳米粉末混合均匀，其中AlF3纳米粉末的质量为烘干产物质量的0.2％；然后置于氧气气氛中，在450℃烧结8h，冷却至室温得到成品材料，即本对比例的双层包覆锂钠复合富锂锰基正极材料。
即对比例4与实施例1的区别在于S2中未加入掺杂剂。
对比例5
本对比例提供一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其制备方法与实施例1的区别在于：
S2中，将掺杂剂Nb2O5纳米粉末替换为MgO纳米粉末。
对比例6
本对比例提供一种锂钠复合富锂锰基正极材料的制备方法，包括以下具体步骤：
S1：以一定化学计量数之比(Ni元素和Mn元素的摩尔比为35:65)的NiSO4和MnSO4为镍源和锰源，以NH4OH为络合剂，以NaOH为沉淀剂，通过共沉淀法制备Ni0.35Mn0.65(OH)2前驱体。
S2：将S1得到的Ni0.35Mn0.65(OH)2前驱体与Li2CO3、NaHCO3、Nb2O5纳米粉末混合均匀，其中混合物中，锂钠元素之和与镍锰元素之和的摩尔比为1.35：1；钠元素与锂钠元素之和的摩尔比0.1：1；Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.3％。混合均匀后置于氧气气氛中，在900℃烧结15h，烧结完成后冷却至室温得到一烧产物。
S3：将S2得到的一烧产物与AlF3纳米粉末混合均匀，其中AlF3纳米粉末的质量为烘干产物质量的0.2％；然后置于氧气气氛中，在450℃烧结8h，冷却至室温得到成品材料，即本对比例的锂钠复合富锂锰基正极材料。
即对比例6与实施例1的区别在于无氨水反应工序，即未进行实施例1的S3。
对比例7
本对比例提供一种锂钠复合富锂锰基正极材料的制备方法，包括以下具体步骤：
S1：以一定化学计量数之比(Ni元素和Mn元素的摩尔比为35:65)的NiSO4和MnSO4为镍源和锰源，以NH4OH为络合剂，以NaOH为沉淀剂，通过共沉淀法制备Ni0.35Mn0.65(OH)2 前驱体。
S2：将S1得到的Ni0.35Mn0.65(OH)2前驱体与Li2CO3、NaHCO3、Nb2O5纳米粉末混合均匀，其中混合物中，锂钠元素之和与镍锰元素之和的摩尔比为1.35：1；钠元素与锂钠元素之和的摩尔比0.1：1；Nb2O5纳米粉末的质量是Ni0.35Mn0.65(OH)2前驱体质量的0.3％。混合均匀后置于氧气气氛中，在900℃烧结15h，烧结完成后冷却至室温得到一烧产物。
S3：将S2得到的一烧产物置于1mol/L的氨水溶液中碱洗30min，碱洗产物通过抽滤、去离子水洗涤，洗涤至滤水pH值呈中性，然后在80℃烘箱中烘烤12h，得到烘干产物；
S4：将S3得到的烘干产物置于氧气气氛中，在450℃烧结8h，冷却至室温得到成品材料，即本对比例的锂钠复合富锂锰基正极材料。
即对比例7与实施例1的区别在于无氟化物包覆。
测试
(1)分别对实施例1-16、以及对比例1-7的一烧产物进行残余碱离子含量的测试，具体数据由电位滴定仪测试得到。结果请参阅表1：
表1
由实施例1、2、3、4、5、6、12、13及其表1中的数据可知，镍锰氢氧化物前驱体中镍含量增加、一烧温度降低、锂钠配比提升、钠占比提升、掺杂剂量降低均会导致一烧产物的残余碱离子含量上升。
相较于实施例1、7、8、9、10、11中采用低熔点的钠盐，对比例2和3中采用的高熔点的钠盐会导致一烧产物的残余碱离子含量显著上升。
实施例1、14、15、16和对比例4和5数据显示S2中未添加或未添加合适的掺杂剂会 显著提升一烧产物的残余碱离子含量。
(2)分别对实施例1-24、以及对比例1-7的成品进行残余碱离子含量的测试。结果请参阅表2：
表2
由表2数据可知，将一烧产物置于氨水溶液中反应一段时间并经过氟化物包覆二烧后，成品表面残余碱离子含量显著降低。
(3)电化学性能测试
分别将实施例1-24与对比例1-7制备的成品即正极材料进行电化学性能测试，电化学性能测试使用纽扣电池。工作电极是将活性物质、导电碳、聚偏氟乙烯按质量比为95:2:3在去离子水中混合均匀后涂覆于铜箔上制得，对电极使用钠箔。电解液为1mol/L的NaClO4溶于EC/DEC(体积比为1:1)混合溶剂中并添加3wt％LiDFOB，隔膜采用PP/PE/PP复合膜。扣式电池的组装在氧气和水含量均低于1ppm的手套箱中进行。电池的电化学性能测试在电化学工作站上进行。测试电压为2.3-4.55V，电流密度为1/3C。测试结果请参阅表3
表3

表3中，实施例1和2的数据显示，在制备双层包覆锂钠复合富锂锰基正极材料的过程中，提高镍锰氢氧化物前驱体中镍的含量，会降低材料的首次可逆比容量和首次库伦效率。实施例1、3、4、5、6、23、24的数据显示，在制备双层包覆锂钠复合富锂锰基正极材料的过程中，一烧温度(即S2中的烧结温度)、锂配比、钠占比、二烧温度(即S4中的烧结温度)均会对成品材料的性能产生影响。实施例1、7、8、9、10、11与对比例1、2、3的数据显示，一烧过程(即S2)中不加入钠盐或加入高熔点钠盐的获得的成品材料的首次可逆比容量均低于本公开一烧过程中(即S2)加入低熔点钠盐获得的成品材料的首次可逆比容量。实施例1、12、13、14、15、16与对比例4和5的数据显示，一烧过程(即S2)中未添加或未添加合适的掺杂剂会显著降低成品材料的首次可逆比容量。实施例1、17、18与对比例6的数据显示，一烧产物未在氨水溶液中碱洗反应，其获得的成品材料的首次可逆比容量低于本公开的碱洗反应后成品材料的首次可逆比容量。实施例1、19、20、21、22与对比例7的数据显示，本公开的材料经过氟化物包覆后可显著提升成品材料的首次放电比容量和首次库伦效率。
另外请参阅图1，本公开所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，制备得到的双层包覆锂钠复合富锂锰基正极材料中，由内到外分别为锂钠复合富锂锰基材料、尖晶石相包覆层，氟化物包覆层。请参阅图2-图7，本公开实施例制备的双层包覆锂钠复合富锂锰基正极材料，其形貌好，颗粒大；形成的尖晶石相和氟化物双层包覆，提高材料的电化学性能；尖晶石相能为Li+的迁移提供三维通道，改善材料界面动力学性能，而氟化物包覆可降低氧的不可逆损失，最终达到提升材料性能的目的。
以上所述实施例仅表达了本公开的几种实施方式，其描述较为具体和详细，但并不能因 此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本公开构思的前提下，还可以做出若干变形和改进，则本公开也意图包含这些改动和变形。

Claims (15)

  1. 一种双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：包括以下步骤：
    S1：利用共沉淀法制备镍锰氢氧化物前驱体；
    S2：将S1得到的镍锰氢氧化物前驱体，与锂盐、钠盐、掺杂剂混合均匀后进行烧结，得到一烧产物；
    S3：将S2得到的一烧产物置于氨水溶液中反应，然后抽滤、洗涤、烘干，得到烘干产物；
    S4：将S3得到的烘干产物与氟化物混合均匀后进行烧结，得到所述双层包覆锂钠复合富锂锰基正极材料。
  2. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S1中的镍锰氢氧化物前驱体为NixMn1-x(OH)2，其中0.35≤x≤0.4。
  3. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中的锂盐为Li2CO3。
  4. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中的钠盐为NaHCO3、NaCOOH、CH3COONa、CH3CH2COONa、Na2C2O4、C6H5Na3O7中的一种。
  5. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中的掺杂剂为Nb2O5纳米粉末、Co3O4纳米粉末、WO3纳米粉末、La2O3纳米粉末中的一种。
  6. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中，锂钠元素之和与镍锰元素之和的摩尔比为1.3～1.4:1。
  7. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中，钠元素与锂钠元素之和的摩尔比为0.1～0.15:1。
  8. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中，掺杂剂的质量是镍锰氢氧化物前驱体质量的0.3％～0.5％。
  9. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S2中的烧结在氧气气氛中进行，烧结温度为900-1000℃，烧结时间为15-20h。
  10. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S3中氨水溶液的浓度为0.5～1mol/L，反应时间为30～60min。
  11. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在 于：S3中，采用去离子水洗涤至滤水pH值呈中性。
  12. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S3中的烘干温度为60～80℃，时间为12～24h。
  13. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S4中的氟化物为AlF3纳米粉末、ZrF4纳米粉末、CaF2纳米粉末中的一种。
  14. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S4中，氟化物的质量为烘干产物质量的0.1％～0.3％。
  15. 根据权利要求1所述的双层包覆锂钠复合富锂锰基正极材料的制备方法，其特征在于：S4中的烧结在氧气气氛中进行，烧结温度为600-800℃，烧结时间为8-10h。
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