A layered oxide composite material and its preparation method and application

Abstract

The present invention belongs to the technical field of sodium ion battery materials, and specifically relates to a layered oxide composite material and its preparation method and application. The present invention provides a layered oxide composite material, the chemical composition of which is K x Na 0.64‑x Mg 0.2 Ni 0.74 Mn 0.74 O 2‑x F x , the value of x ranges from 0.02 to 0.12; the layered oxide composite material has a P2-type structure. The present invention utilizes a synergistic effect of potassium / fluorine dual ion doping to form stable crystals with the metal oxide on the surface of the layered oxide material. This suppresses side reactions during charge and discharge, forming a stable solid electrolyte membrane, and improving the coulombic efficiency and cycling stability of the positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery materials, and specifically relates to a layered oxide composite material and a preparation method and application thereof. Background Art

[0002] As lithium resources continue to be developed globally, their costs remain high, and lithium-ion batteries are gradually losing their competitiveness in large-scale energy storage. Sodium-ion batteries, on the other hand, offer greater cost advantages than lithium-ion batteries and hold greater promise for application in large-scale energy storage.

[0003] Currently, the cathode materials for sodium-ion batteries primarily include polyanionic materials, Prussian blue compounds, and metal oxides. Polyanionic materials have high electronic conductivity, but suffer from low specific capacity and low electronic conductivity. While Prussian blue compounds and metal oxides have high specific capacity, they contain a high amount of crystalline water and vacancy defects, which can affect the battery's cycling stability. Metal oxides undergo phase transitions during charge and discharge cycles, similarly reducing the battery's cycling stability. Summary of the Invention

[0004] The purpose of the present invention is to provide a layered oxide composite material and a preparation method and application thereof. The layered oxide composite material provided by the present invention has excellent cycle stability.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a layered oxide composite material, the chemical composition of the layered oxide composite material is K x Na 0.64-x Mg 0.2 Ni 0.74 Mn 0.74 O 2-x F x , the value range of x is 0.02~0.12;

[0007] The layered oxide composite material has a P2 type structure.

[0008] Preferably, the particle size D50 of the layered oxide composite material is 6.5-10 μm.

[0009] The present invention also provides a method for preparing the layered oxide composite material described in the above technical solution, comprising the following steps:

[0010] first mixing a soluble manganese source, a soluble nickel source, a soluble magnesium source, and water to obtain a first mixed solution;

[0011] a second mixing of the soluble sodium source, the complexing agent and water to obtain a second mixed solution;

[0012] The first mixed solution and the second mixed solution are mixed for a third time, and subjected to a complexation reaction to obtain a precursor;

[0013] The precursor is mixed with a soluble fluorine source and a soluble potassium source, and the mixture is calcined to obtain the layered oxide composite material.

[0014] Preferably, the molar ratio of the soluble manganese source, the soluble nickel source, the soluble magnesium source and water is 1:1:0.27:150-200, calculated based on the amount of Mn, Ni and Mg.

[0015] Preferably, the complexing agent includes one or more of citric acid, citrate, maleic acid and maleate.

[0016] Preferably, based on the amount of Na, the molar ratio of the soluble sodium source, the complexing agent and water is 1:1:11.

[0017] Preferably, the third mixing comprises:

[0018] Under stirring, adding the second mixed liquid dropwise to the first mixed liquid;

[0019] The rate of the dropwise addition is 3 to 5 mL / min;

[0020] The mass ratio of the first mixed liquid to the second mixed liquid is 430-450:1.

[0021] Preferably, the molar ratio of the soluble fluorine source to the soluble potassium source is 1:1, based on the amount of F and K, and the value of x ranges from 0.02 to 0.12;

[0022] The mass ratio of the precursor to the soluble fluorine source is 100:1-10.

[0023] Preferably, the calcination temperature is 500-1000° C., the holding time is 5-10 h, and the pressure is 0.1-1 MPa.

[0024] The present invention also provides the use of the layered oxide composite material described in the above technical solution or the layered oxide composite material prepared by the preparation method described in the above technical solution in sodium ion positive electrode materials.

[0025] The present invention provides a layered oxide composite material, the chemical composition of the layered oxide composite material is K x Na 0.64-x Mg 0.2 Ni 0.74 Mn 0.74 O 2-xF x , the value of x ranges from 0.02 to 0.12; the layered oxide composite material has a P2-type structure. The present invention utilizes a synergistic effect of potassium / fluorine dual ion doping to form stable crystals with the metal oxide on the surface of the layered oxide material. This suppresses side reactions during charge and discharge, forming a stable solid electrolyte membrane, and improving the coulombic efficiency and cycling stability of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a SEM image of the layered oxide composite material obtained in Example 1;

[0027] Figure 2 The cycle stability performance curves of the sodium ion half-cells assembled from the layered oxide composite materials obtained in Example 4 and Comparative Example 2;

[0028] Figure 3 The figure shows the rate performance curve of the sodium ion half-cell assembled from the layered oxide composite materials obtained in Example 4 and Comparative Example 2. DETAILED DESCRIPTION

[0029] The present invention provides a layered oxide composite material, the chemical composition of the layered oxide composite material is K x Na 0.64-x Mg 0.2 Ni 0.74 Mn 0.74 O 2-x F x , the value range of x is 0.02~0.12;

[0030] The layered oxide composite material has a P2 type structure.

[0031] In the present invention, the value range of x is 0.02 to 0.12, more preferably 0.05 to 0.10, and even more preferably 0.06 to 0.08.

[0032] In the present invention, the valence of Mn in the chemical composition preferably includes +2 and +3.

[0033] In the present invention, the valence of Ni in the chemical composition is preferably +2. In the present invention, the total valence of the chemical composition is preferably 0.

[0034] In the present invention, the particle size D50 of the layered oxide composite material is preferably 6.5 to 10 μm.

[0035] In the present invention, the composite material with P2 type structure has a larger interlayer spacing, which can increase the Na +storage sites and ensures the realization of Na + Fast transmission.

[0036] The present invention also provides a method for preparing the layered oxide composite material described in the above technical solution, comprising the following steps:

[0037] first mixing a soluble manganese source, a soluble nickel source, a soluble magnesium source, and water to obtain a first mixed solution;

[0038] a second mixing of the soluble sodium source, the complexing agent and water to obtain a second mixed solution;

[0039] The first mixed solution and the second mixed solution are mixed for a third time, and subjected to a complexation reaction to obtain a precursor;

[0040] The precursor is mixed with a soluble fluorine source and a soluble potassium source, and the mixture is calcined to obtain the layered oxide composite material.

[0041] In the present invention, unless otherwise specified, all raw materials are products well known to those skilled in the art.

[0042] The present invention first mixes a soluble manganese source, a soluble nickel source, a soluble magnesium source and water to obtain a first mixed solution.

[0043] In the present invention, the soluble manganese source preferably includes manganese acetate tetrahydrate or manganese sulfate monohydrate; the soluble nickel source preferably includes nickel acetate tetrahydrate or nickel sulfate hexahydrate; and the soluble magnesium source preferably includes magnesium acetate tetrahydrate.

[0044] In the present invention, the molar ratio of the soluble manganese source, the soluble nickel source, the soluble magnesium source and water is preferably 1:1:0.27:150-200, calculated based on the amount of Mn, Ni and Mg.

[0045] The present invention has no particular limitation on the first mixing process, and the first mixing process may be performed using a process well known to those skilled in the art.

[0046] In the present invention, the soluble sodium source, the complexing agent and water are mixed for the second time to obtain a second mixed solution.

[0047] In the present invention, the soluble sodium source preferably includes sodium carbonate and sodium chloride; the molar ratio of the sodium carbonate to sodium chloride is preferably 1:9.

[0048] In the present invention, the complexing agent preferably includes one or more of citric acid, citrate, maleic acid and maleate; the citrate preferably includes sodium citrate; and the maleate preferably includes sodium maleate.

[0049] In the present invention, the molar ratio of the soluble sodium source, the complexing agent and water is preferably 1:1:11, calculated based on the amount of Na.

[0050] The present invention has no particular limitation on the second mixing process, and the process may be performed using a process well known to those skilled in the art.

[0051] In the present invention, there is no time limit for the first mixing and the second mixing.

[0052] After obtaining the first mixed liquid and the second mixed liquid, the present invention performs a third mixing of the first mixed liquid and the second mixed liquid, and performs a complexation reaction to obtain a precursor.

[0053] In the present invention, the mass ratio of the first mixed liquid to the second mixed liquid is preferably 430-450:1, more preferably 435-445:1, and even more preferably 438-440:1.

[0054] In the present invention, the third mixing preferably includes:

[0055] The second mixed liquid is added dropwise to the first mixed liquid under stirring.

[0056] In the present invention, the stirring speed is preferably 500 to 1000 rpm.

[0057] In the present invention, the dropping rate is preferably 3 to 5 mL / min.

[0058] In the present invention, the complexation reaction is carried out under stirring, and the stirring speed is preferably 500-800 rpm. In the present invention, the temperature of the complexation reaction is preferably 50-80°C. In the present invention, the complexation reaction occurs when the second mixed solution is dripped into the first mixed solution. The time of the complexation reaction includes the dripping time of the second mixed solution and the stirring time after the dripping is completed; the dripping time is preferably 1-7 hours; the stirring time after the dripping is completed is preferably 0.5-4 hours.

[0059] After the complexation reaction, the present invention preferably further comprises drying the obtained liquid.

[0060] In the present invention, the drying method is preferably spray drying; the feed temperature during the spray drying is preferably 110-200°C.

[0061] In the present invention, the particle size D50 of the precursor is preferably 6.5 to 10 μm.

[0062] After obtaining the precursor, the present invention fourthly mixes the precursor with a soluble fluorine source and a soluble potassium source, and calcines the mixture to obtain the layered oxide composite material.

[0063] In the present invention, the molar ratio of the soluble fluorine source to the soluble potassium source is preferably x:x, based on the amount of F and K, and the value of x ranges from 0.02 to 0.12. In the present invention, the soluble fluorine source and the soluble potassium source are both potassium fluoride.

[0064] In the present invention, the mass ratio of the precursor to the soluble fluorine source is preferably 100:1-10.

[0065] In the present invention, the fourth mixing method is preferably ball milling. The ball milling speed is preferably 220-320 rpm, more preferably 250-300 rpm, and even more preferably 260-280 rpm; the milling time is preferably 10-20 minutes, more preferably 12-18 minutes, and even more preferably 13-15 minutes. In the present invention, the ball milling is preferably performed in a planetary ball mill; the planetary ball mill is preferably operated in a sequential forward and reverse rotation mode, with the forward rotation cycle preferably being 10 times and the reverse rotation cycle preferably being 10 times.

[0066] In the present invention, the calcination temperature is preferably 500-1000°C, more preferably 600-900°C, and more preferably 700-800°C; the heating rate to the calcination temperature is preferably 3-5°C / min; the holding time is preferably 5-10h, more preferably 6-9h, and more preferably 7-8h; the pressure is preferably 0.1-1MPa, more preferably 0.2-0.9MPa, and more preferably 0.3-0.8MPa.

[0067] In the present invention, the calcination is preferably carried out in a nitrogen atmosphere. In the present invention, the calcination is preferably carried out in a tube furnace. In the present invention, a composite material with good crystallinity and density can be obtained after calcination.

[0068] After the calcination is completed, the present invention preferably further comprises sequentially washing and drying the resulting material. In the present invention, the water washing is preferably performed 3 to 5 times. In the present invention, the water washing can remove inorganic salt impurities. In the present invention, the inorganic salt impurities removed by the water washing can be recycled by recrystallization.

[0069] In the present invention, the drying temperature is preferably 80° C., and the drying time is preferably 24 hours.

[0070] The present invention also provides the use of the layered oxide composite material described in the above technical solution, or the layered oxide composite material prepared by the preparation method described in the above technical solution, in a sodium ion positive electrode material. The present invention does not particularly limit the specific implementation of the application, and can be carried out using methods familiar to those skilled in the art.

[0071] To further illustrate the present invention, a layered oxide composite material, a preparation method thereof, and applications thereof are described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0072] Example 1

[0073] 1 mmol of manganese acetate tetrahydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0074] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0075] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0076] The obtained precursor and 0.02 mmol potassium fluoride were added to a planetary ball mill, the speed was set to 250 rpm, the time was 15 min, forward rotation was 10 times, reverse rotation was 10 times, after grinding evenly, placed in a tube furnace, and calcined at a heating rate of 3 ° C / min to 500 ° C in a nitrogen atmosphere, the holding time was 5 h, and the pressure was 0.4 MPa; after calcination, the obtained material was washed with deionized water 5 times, and then placed in a drying oven at 80 ° C for 24 h to obtain the layered oxide composite material (chemical composition is K 0.02 Na 0.62 Mg 0.2 Ni 0.74 Mn 0.74 O 1.98 F 0.02 ).

[0077] Example 2

[0078] 1 mmol of manganese sulfate monohydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0079] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0080] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0081] The obtained precursor and 0.02 mmol potassium fluoride were added to a planetary ball mill, the speed was set to 250 rpm, the time was 15 min, forward rotation was 10 times, and reverse rotation was 10 times. After grinding evenly, it was placed in a tube furnace and calcined at a heating rate of 3 ° C / min to 1000 ° C in a nitrogen atmosphere. The holding time was 5 h and the pressure was 0.4 MPa. After calcination, the obtained material was washed with deionized water 5 times and placed in a drying oven at 80 ° C for 24 h to obtain the layered oxide composite material (chemical composition is K 0.02 Na 0.62 Mg 0.2 Ni 0.74 Mn 0.74 O 1.98 F 0.02 ).

[0082] Example 3

[0083] 1 mmol of manganese acetate tetrahydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0084] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0085] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0086] The obtained precursor and 0.06 mmol potassium fluoride were added to a planetary ball mill, the speed was set to 250 rpm, the time was 15 min, forward rotation was 10 times, reverse rotation was 10 times, after grinding evenly, placed in a tube furnace, and in a nitrogen atmosphere, the temperature was increased to 500 ° C at a heating rate of 3 ° C / min for calcination, the holding time was 5 h, and the pressure was 0.4 MPa; after calcination, the obtained material was washed with deionized water 5 times, and placed in a drying oven at 80 ° C for 24 h to obtain the layered oxide composite material (chemical composition is K 0.06 Na 0.58 Mg 0.2 Ni 0.74 Mn 0.74 O 1.94 F 0.06 ).

[0087] Example 4

[0088] 1 mmol of manganese acetate tetrahydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0089] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0090] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0091] The obtained precursor and 0.12 mmol potassium fluoride were added to a planetary ball mill, the speed was set to 250 rpm, the time was 15 min, forward rotation was 10 times, reverse rotation was 10 times, after grinding evenly, placed in a tube furnace, and calcined at a heating rate of 3 ° C / min to 1000 ° C in a nitrogen atmosphere, the holding time was 5 h, and the pressure was 0.4 MPa; after calcination, the obtained material was washed with deionized water 5 times, and then placed in a drying oven at 80 ° C for 24 h to obtain the layered oxide composite material (chemical composition is K 0.12 Na 0.52 Mg 0.2 Ni 0.74 Mn 0.74 O 1.88 F 0.12 ).

[0092] Comparative Example 1

[0093] 1 mmol of manganese acetate tetrahydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0094] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0095] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0096] The obtained precursor was placed in a tube furnace and calcined at a heating rate of 3°C / min to 500°C in a nitrogen atmosphere. The holding time was 5 hours and the pressure was 0.4 MPa. After calcination, the obtained material was washed with deionized water 5 times and then dried in a drying oven at 80°C for 24 hours to obtain the layered oxide composite material (chemical composition is Na 0.6 Mg 0.2 Ni 0.74 Mn 0.74 O2).

[0097] Comparative Example 2

[0098] 1 mmol of manganese acetate tetrahydrate, 1 mmol of nickel acetate tetrahydrate, 0.27 mmol of magnesium acetate tetrahydrate and 200 mmol of deionized water were mixed to obtain a first mixed solution;

[0099] 0.83 mmol of sodium citrate, 0.083 mmol of sodium carbonate, 0.747 mmol of sodium chloride and 9.13 mmol of deionized water were mixed to obtain a second mixed solution;

[0100] The first mixed solution was added dropwise to the second mixed solution at a stirring rate of 3 mL / min under a stirring rate of 500 rpm for 3 h. After the addition was completed, the mixture was stirred at a stirring rate of 500 rpm and a temperature of 60°C for 60 min to carry out a complexation reaction. The obtained liquid was placed in a spray dryer with an inlet temperature of 180°C and a feed rate of 5 mL / min to obtain a precursor.

[0101] The obtained precursor was placed in a tube furnace and calcined at a heating rate of 3°C / min to 1000°C in a nitrogen atmosphere for 5 hours at a pressure of 0.4 MPa. After calcination, the layered oxide composite material (chemical composition: Na 0.64 Mg 0.2 Ni 0.74 Mn 0.74 O2).

[0102] Performance Testing

[0103] Test Example 1

[0104] The layered oxide composite material obtained in Example 1 was subjected to scanning electron microscopy testing, and the obtained SEM image is as follows: Figure 1 As shown, from Figure 1 It can be seen that the obtained layered oxide composite material has a relatively dense structure, and the entire particle has a spherical structure, which will be better for the application of the material.

[0105] Test Example 2

[0106] Electrochemical performance tests were conducted using the layered oxide composite materials obtained in Examples 1 to 4 and Comparative Examples 1 to 2 as positive electrode active materials;

[0107] The layered oxide composite materials obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were used as positive electrode materials. In a drying room with a dew point below -40°C and a humidity below 10%, the positive electrode material, a binder, and conductive carbon black were mixed in NMP at a mass ratio of 90:5:5, homogenized to control the solid content to 45%, and coated on an aluminum foil current collector. The mixture was vacuum-baked at 100 to 110°C for 4 to 8 hours, pressed into shape, and then punched into sheets to prepare sodium positive electrode sheets.

[0108] A sodium ion half-cell was assembled using a sodium metal sheet as the negative electrode and 1 mol / L NaPF6 in EC / DMC (Vol 1:1) as the electrolyte. The electrochemical performance of the resulting sodium ion half-cell was tested using the LAND battery testing system from Wuhan Landian Electronics Co., Ltd.

[0109] The obtained sodium ion half-cell was subjected to constant current charge and discharge tests under the test conditions of 1C and a voltage range of 2.0 to 4V. The test results are shown in Table 1.

[0110] Table 1 Constant current charge and discharge test results of sodium ion half-cell

[0111] First charge capacity (mAh / g) Capacity retention efficiency after 300 cycles (%) Example 1 124.78 77.6％ Example 2 119.98 75.8％ Example 3 127.09 76.3％ Example 4 120.41 74.2％ Comparative Example 1 132.1 53.9％ Comparative Example 2 138.26 54.1％

[0112] The cycle performance diagram is as follows: Figure 2 As shown, from Figure 2It can be seen that after 300 cycles at a current density of 1C (=120 mA / g), the layered oxide composite material obtained in Example 4 still has 89.1 mAh / g, with a capacity retention rate of 74.2%, while the layered oxide composite material in the undoped Comparative Example 2 has only 74.8 mAh / g after 300 cycles, with a capacity retention rate of 54.1%;

[0113] The obtained rate performance diagram is as follows Figure 3 As shown, from Figure 3 It can be clearly seen that the doped layered oxide composite material obtained in the present invention has good rate performance.

[0114] In summary, it can be seen that the synergistic effect produced by the potassium / fluorine dual-doping of the layered oxide composite material provided by the present invention can effectively inhibit the occurrence of side reactions, thereby improving the cycle performance.

[0115] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A layered oxide composite material for a sodium ion battery positive electrode, characterized in that: The chemical composition of the layered oxide composite material is K x Na 0.64-x Mg 0.2 Ni 0.74 Mn 0.74 O 2-x F x , the value range of x is 0.02~0.12; The layered oxide composite material has a P2 type structure; The preparation method of the layered oxide composite material comprises the following steps: first mixing a soluble manganese source, a soluble nickel source, a soluble magnesium source, and water to obtain a first mixed solution; a second mixing of the soluble sodium source, the complexing agent and water to obtain a second mixed solution; The first mixed solution and the second mixed solution are mixed for a third time, and subjected to a complexation reaction to obtain a precursor; The precursor is mixed with a soluble fluorine source and a soluble potassium source, and the mixture is calcined to obtain the layered oxide composite material.

2. The layered oxide composite material according to claim 1, characterized in that The particle size D50 of the layered oxide composite material is 6.5-10 μm.

3. The method for preparing the layered oxide composite material according to any one of claims 1 to 2, characterized in that: The steps are: first mixing a soluble manganese source, a soluble nickel source, a soluble magnesium source, and water to obtain a first mixed solution; a second mixing of the soluble sodium source, the complexing agent and water to obtain a second mixed solution; The first mixed solution and the second mixed solution are mixed for a third time, and subjected to a complexation reaction to obtain a precursor; The precursor is mixed with a soluble fluorine source and a soluble potassium source, and the mixture is calcined to obtain the layered oxide composite material.

4. The preparation method according to claim 3, characterized in that Calculated based on the amount of Mn, Ni and Mg, the molar ratio of the soluble manganese source, the soluble nickel source, the soluble magnesium source and water is 1:1:0.27:150-200.

5. The preparation method according to claim 3, characterized in that The complexing agent includes one or more of citric acid, citrate, maleic acid and maleate.

6. The preparation method according to claim 3 or 5, characterized in that Calculated based on the amount of Na, the molar ratio of the soluble sodium source, the complexing agent and water is 1:1:

11.

7. The preparation method according to claim 3, characterized in that The third mixing comprises: Under stirring, adding the second mixed liquid dropwise to the first mixed liquid; The rate of the dropwise addition is 3-5 mL / min; The mass ratio of the first mixed liquid to the second mixed liquid is 430-450:

1.

8. The preparation method according to claim 3, characterized in that Calculated based on the amount of F and K, the molar ratio of the soluble fluorine source to the soluble potassium source is 1:1, and the value of x ranges from 0.02 to 0.12; The mass ratio of the precursor to the soluble fluorine source is 100:1-10.

9. The preparation method according to claim 3, characterized in that The calcination temperature is 500-1000° C., the holding time is 5-10 hours, and the pressure is 0.1-1 MPa.

10. Use of the layered oxide composite material according to any one of claims 1 to 2 or the layered oxide composite material prepared by the preparation method according to any one of claims 3 to 9 in sodium ion positive electrode materials.

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