Transition metal layered oxide positive electrode material for sodium battery, and preparation method therefor and use thereof

Abstract

The invention relates to the technical field of batteries. Provided is a transition metal layered oxide positive electrode material for a sodium battery, and a preparation method therefor and the use thereof. The chemical formula of the positive electrode material is NaaNibMgcCodMnO2, wherein 0.75≤a≤0.9, 0.1≤b≤0.75, 0.1≤c≤0.25, and 0.1≤d≤0.4. The preparation method for the positive electrode material comprises the following steps: weighing and mixing a nickel source, a magnesium source, a manganese source and a cobalt source, adding the resulting mixture to deionized water, and mixing same to obtain a salt solution having a metal ion concentration of 1.0-2.0 mol / L; mixing the salt solution, a precipitant and a complexing agent, so as to obtain a precursor material; adding a sodium source to deionized water, adding the precursor material thereto, stirring and mixing same, and evaporating moisture, so as to obtain a layered oxide; and drying the layered oxide, and then grinding, calcining and cooling same to obtain the positive electrode material. The positive electrode material is applied to the field of sodium-ion batteries.

Description

Transition metal layered oxide sodium battery positive electrode material, preparation method and application Technical Field

[0001] The present application relates to the technical field of battery positive electrode materials, and in particular to transition metal layered oxide sodium battery positive electrode materials, preparation methods, and applications. Background Art

[0002] The cathode material plays a key role in the production of sodium-ion batteries. Currently, the main cathode materials can be divided into transition metal layered oxides, polyanions, and Prussian blue. Transition metal layered oxides are the preferred cathode material for sodium-ion batteries due to their simple preparation, easy technology transfer, high voltage platform, and excellent overall performance.

[0003] The disadvantage of the existing technology is that the transition metal layered oxides currently produced have high water absorption, unstable specific capacity, and unstable phase structure of the material, resulting in poor battery cycle performance.

[0004] Summary of the Invention

[0005] In order to solve at least one of the above technical problems, a positive electrode material with weaker water absorption is developed for the preparation of the positive electrode of a sodium battery. The present application provides a transition metal layered oxide sodium battery positive electrode material, a preparation method and an application.

[0006] On the one hand, the present application provides a transition metal layered oxide sodium battery positive electrode material, the chemical formula of the positive electrode material is Na a Ni b Mg c Co d MnO2, where 0.75≤a≤0.9, 0.1≤b≤0.75, 0.1≤c≤0.25, 0.1≤d≤0.4.

[0007] By adopting the above technical solution, the prepared positive electrode material has weak water absorption, which can effectively reduce the positive electrode material from absorbing water and becoming jelly-like during the preparation of the electrode sheet, thereby facilitating subsequent coating; and reducing the water absorption of the positive electrode material can make the positive electrode material less likely to undergo phase structure changes during the subsequent charging and discharging process, thereby improving the stability of the positive electrode material.

[0008] Optionally, the raw materials of the positive electrode material include a nickel source, a magnesium source, a manganese source, a cobalt source and a sodium source; wherein:

[0009] The nickel source is one or more of nickel acetate, nickel nitrate, and nickel sulfate; and / or

[0010] The magnesium source is one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate; and / or

[0011] The manganese source is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese oxalate; and / or

[0012] The cobalt source is one or more of cobalt acetate, cobalt sulfate, cobalt nitrate, and cobalt oxalate; and / or

[0013] The sodium source is one or more of sodium acetate, sodium chloride, sodium nitrate and sodium sulfate.

[0014] Optionally, the median particle size D50 of the positive electrode material is 1 to 20 μm.

[0015] Optionally, the positive electrode material is a layered 03 type structure.

[0016] In a second aspect, the present application also provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0017] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, and add them to deionized water to obtain a salt solution with a metal ion concentration of 1.0 to 2.0 mol / L;

[0018] mixing a salt solution, a precipitant, and a complexing agent to obtain a precursor material;

[0019] Adding a formulated amount of sodium source to deionized water, then adding the precursor material, stirring and mixing, and evaporating the water to obtain a layered oxide;

[0020] The layered oxide is dried, fully ground, calcined, and cooled to obtain a positive electrode material.

[0021] By adopting the above preparation method, the positive electrode material prepared has weak water absorption and strong phase stability during the charge and discharge process.

[0022] Optionally, the precipitant is a 25-35 wt% potassium hydroxide solution.

[0023] Optionally, the complexing agent is a 5-10 mol / L ammonia solution, and in the process of mixing the salt solution, the precipitant and the complexing agent to obtain the precursor material, the ammonia concentration is always controlled to be 0.25-0.35 mol / L, and the pH is always controlled to be 10-11.

[0024] Optionally, the nickel source, magnesium source, manganese source and cobalt source are mixed and added to deionized water, with a stirring speed of 300 to 600 r / min and a stirring time of 60 min; and / or,

[0025] Mixing the salt solution, the precipitant and the complexing agent at a stirring speed of 400 to 600 r / min for 60 minutes; and / or,

[0026] After adding the precursor material, the stirring speed is 400-600 r / min and the stirring time is 60 min.

[0027] Optionally, the evaporation process is: evaporating to dryness in an oil bath at 95°C; and / or,

[0028] The drying process is as follows: heating to 115°C at a heating rate of 10°C / min and drying for 15 hours; and / or,

[0029] The calcination process is as follows: heating to 600°C at a heating rate of 15-20°C / min and calcining for 15 hours.

[0030] In a third aspect, the present application provides the application of the above-mentioned positive electrode material in the field of sodium ion batteries.

[0031] By adopting the above-mentioned positive electrode material, the sodium ion battery prepared has excellent stability and cycle performance.

[0032] In summary, the present invention includes at least one of the following beneficial technical effects:

[0033] 1. The positive electrode material prepared in this application has low water absorption;

[0034] 2. The positive electrode material prepared in this application has high phase structure stability during the charge and discharge process. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] This application designs a transition metal layered oxide sodium battery positive electrode material, the chemical formula of the positive electrode material is Na a Ni b Mg c Co d MnO2, where 0.75≤a≤0.9, 0.1≤b≤0.75, 0.1≤c≤0.25, 0.1≤d≤0.4.

[0037] The positive electrode material of the present application is prepared by the following preparation method, comprising the following steps:

[0038] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, and add them to deionized water to obtain a salt solution with a metal ion concentration of 1.0 to 2.0 mol / L;

[0039] mixing a salt solution, a precipitant, and a complexing agent to obtain a precursor material;

[0040] Mixing a formulated amount of sodium source with a precursor material, and evaporating the water to obtain a layered oxide;

[0041] The layered oxide is dried, fully ground, calcined, and cooled to obtain a positive electrode material.

[0042] Application of the positive electrode material of the present application in the field of sodium ion batteries.

[0043] Because the positive electrode material plays a major role in the production process of sodium ion batteries, and among the main positive electrode materials currently, transition metal layered oxides are the preferred positive electrode materials for sodium ion batteries. However, the transition metal layered oxides currently produced have high water absorption, resulting in unstable gram capacity, unstable phase structure of the material, and poor cycle performance of the battery prepared. Therefore, the inventors conducted research in the direction of transition metal layered oxides and obtained a new transition metal layered oxide quaternary positive electrode material. The positive electrode material prepared in this application includes, in addition to sodium, four metal elements: nickel, magnesium, manganese and cobalt, of which nickel, manganese and cobalt are transition metal elements. The formed quaternary layered oxide has low water absorption, and at the same time, the stability of the phase structure of the positive electrode material during the charge and discharge process is improved, which is indirectly reflected in the improvement of the 500 / 1000 cycle capacity and 0.5c reversible specific capacity retention rate of the sodium ion battery prepared with the positive electrode material.

[0044] This application provides Preparation Examples 1 to 18 for preparing different nickel sources, magnesium sources, manganese sources, cobalt sources and sodium sources, respectively, and all of them are anhydrous compounds or compositions of multiple anhydrous compounds.

[0045] Preparation Example 1

[0046] The nickel source in this preparation example is 100 mol % nickel acetate.

[0047] Preparation Example 2

[0048] The nickel source in this preparation example is a mixture of 50 mol% nickel acetate and 50 mol% nickel nitrate.

[0049] Preparation Example 3

[0050] The nickel source in this preparation example is a mixture of 20 mol% nickel acetate, 30 mol% nickel nitrate and 50 mol% nickel sulfate.

[0051] Preparation Example 4

[0052] The magnesium source in this preparation example is 100 mol % magnesium chloride.

[0053] Preparation Example 5

[0054] The magnesium source in this preparation example is a mixture of 50 mol% magnesium chloride and 50 mol% magnesium nitrate.

[0055] Preparation Example 6

[0056] The magnesium source in this preparation example is a mixture of 20 mol% magnesium chloride, 30 mol% magnesium nitrate and 50 mol% magnesium sulfate.

[0057] Preparation Example 7

[0058] The manganese source in this preparation example is 100 mol % manganese acetate.

[0059] Preparation Example 8

[0060] The manganese source in this preparation example is a mixture of 50 mol% manganese sulfate and 50 mol% manganese nitrate.

[0061] Preparation Example 9

[0062] The manganese source in this preparation example is a mixture of 20 mol% manganese acetate, 30 mol% manganese nitrate and 50 mol% manganese oxalate.

[0063] Preparation Example 10

[0064] The manganese source in this preparation example is a mixture of 50 mol% manganese acetate and 50 mol% manganese sulfate.

[0065] Preparation Example 11

[0066] The cobalt source in this preparation example is 100 mol % cobalt acetate.

[0067] Preparation Example 12

[0068] The cobalt source in this preparation example is a mixture of 50 mol% cobalt sulfate and 50 mol% cobalt nitrate.

[0069] Preparation Example 13

[0070] The cobalt source in this preparation example is a mixture of 20 mol% cobalt acetate, 30 mol% cobalt nitrate and 50 mol% cobalt oxalate.

[0071] Preparation Example 14

[0072] The cobalt source in this preparation example is a mixture of 50 mol% cobalt acetate and 50 mol% cobalt sulfate.

[0073] Preparation Example 15

[0074] The sodium source in this preparation example is 100 mol% sodium acetate.

[0075] Preparation Example 16

[0076] The sodium source in this preparation example is a mixture of 50 mol% sodium sulfate and 50 mol% sodium nitrate.

[0077] Preparation Example 17

[0078] The sodium source in this preparation example is a mixture of 20 mol% sodium acetate, 30 mol% sodium nitrate and 50 mol% sodium chloride.

[0079] Preparation Example 18

[0080] The sodium source in this preparation example is a mixture of 50 mol% sodium acetate and 50 mol% sodium sulfate.

[0081] Specific embodiments

[0082] Example 1

[0083] This example uses the nickel source prepared in Preparation Example 1, the magnesium source prepared in Preparation Example 6, the manganese source prepared in Preparation Example 9, the cobalt source prepared in Preparation Example 11, and the sodium source prepared in Preparation Example 16.

[0084] The molar ratio of the nickel source, magnesium source, manganese source, cobalt source and sodium source is 0.15:0.2:0.3:1:0.85.

[0085] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, add them to deionized water, and stir them thoroughly at a stirring speed of 300 r / min for 60 min to obtain a salt solution, wherein the metal ion concentration in the salt solution is 1.8 mol / L;

[0086] The salt solution, 25 wt% potassium hydroxide solution and 8 mol / L ammonia solution were mixed at a stirring speed of 600 r / min and a stirring time of 60 min to obtain a precursor material;

[0087] Add the sodium source to the deionized water, then add the precursor material, stirring at 400 r / min for 60 min;

[0088] The mixed solution was added into an oil bath at 95°C and the layered oxide was obtained after the water was evaporated.

[0089] The layered oxide was placed in a forced air drying oven at 115°C for 15 hours at a heating rate of 10°C / min. After drying, it was fully ground and placed in a muffle furnace at 600°C for calcination for 15 hours at a heating rate of 15°C / min. The positive electrode material was obtained by cooling in the furnace.

[0090] Example 2

[0091] This example uses the nickel source prepared in Preparation Example 2, the magnesium source prepared in Preparation Example 5, the manganese source prepared in Preparation Example 7, the cobalt source prepared in Preparation Example 12, and the sodium source prepared in Preparation Example 15.

[0092] The molar ratio of the nickel source, the magnesium source, the manganese source, the cobalt source and the sodium source is 0.1:0.25:0.25:1:0.9.

[0093] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, add them to deionized water, and stir them thoroughly at a stirring speed of 450 r / min for 60 min to obtain a salt solution, wherein the metal ion concentration in the salt solution is 1.2 mol / L;

[0094] The salt solution, 30 wt % potassium hydroxide solution and 8 mol / L ammonia solution were mixed at a stirring speed of 600 r / min and a stirring time of 60 min to obtain a precursor material;

[0095] Add the sodium source to the deionized water, then add the precursor material, stirring at a speed of 500 r / min for 60 min;

[0096] The mixed solution was added into an oil bath at 95°C and the layered oxide was obtained after the water was evaporated.

[0097] The layered oxide was placed in a forced air drying oven at a temperature of 115°C for 15 hours at a heating rate of 10°C / min. After drying, it was fully ground and placed in a muffle furnace at 600°C for calcination for 15 hours at a heating rate of 20°C / min. The positive electrode material was obtained by cooling in the furnace.

[0098] Example 3

[0099] This example uses the nickel source prepared in Preparation Example 3, the magnesium source prepared in Preparation Example 4, the manganese source prepared in Preparation Example 10, the cobalt source prepared in Preparation Example 13, and the sodium source prepared in Preparation Example 17.

[0100] The molar ratio of the nickel source, magnesium source, manganese source, cobalt source and sodium source is 0.2:0.1:0.4:1:0.8.

[0101] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, add them to deionized water, and stir them thoroughly at a stirring speed of 300 r / min for 60 min to obtain a salt solution, wherein the metal ion concentration in the salt solution is 1 mol / L;

[0102] The salt solution, 35 wt % potassium hydroxide solution and 10 mol / L ammonia solution were mixed at a stirring speed of 600 r / min and a stirring time of 60 min to obtain a precursor material;

[0103] Add the sodium source to the deionized water, then add the precursor material, stirring at 400 r / min for 60 min;

[0104] The mixed solution was added into an oil bath at 95°C and the layered oxide was obtained after the water was evaporated.

[0105] The layered oxide was placed in a forced air drying oven at a temperature of 115°C for 15 hours at a heating rate of 10°C / min. After drying, it was fully ground and placed in a muffle furnace at 600°C for calcination for 15 hours at a heating rate of 18°C / min. The positive electrode material was obtained by cooling in the furnace.

[0106] Example 4

[0107] This example uses the nickel source prepared in Preparation Example 1, the magnesium source prepared in Preparation Example 4, the manganese source prepared in Preparation Example 8, the cobalt source prepared in Preparation Example 14, and the sodium source prepared in Preparation Example 18.

[0108] The molar ratio of the nickel source, magnesium source, manganese source, cobalt source and sodium source is 0.25:0.1:0.4:1:0.75.

[0109] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, add them to deionized water, and stir them thoroughly at a stirring speed of 600 r / min for 60 min to obtain a salt solution, wherein the metal ion concentration in the salt solution is 1.5 mol / L;

[0110] The salt solution, 25 wt% potassium hydroxide solution and 5 mol / L ammonia solution were mixed at a stirring speed of 400 r / min and a stirring time of 60 min to obtain a precursor material;

[0111] Add the sodium source to the deionized water, then add the precursor material, stirring at 600 r / min for 60 min;

[0112] The mixed solution was added into an oil bath at 95°C and the layered oxide was obtained after the water was evaporated.

[0113] The layered oxide was placed in a forced air drying oven at 115°C for 15 hours at a heating rate of 10°C / min. After drying, it was fully ground and placed in a muffle furnace at 600°C for calcination for 15 hours at a heating rate of 15°C / min. The positive electrode material was obtained by cooling in the furnace.

[0114] Example 5

[0115] This example uses the nickel source prepared in Preparation Example 2, the magnesium source prepared in Preparation Example 5, the manganese source prepared in Preparation Example 8, the cobalt source prepared in Preparation Example 12, and the sodium source prepared in Preparation Example 16.

[0116] The molar ratio of the nickel source, magnesium source, manganese source, cobalt source and sodium source is 0.25:0.2:0.3:1:0.75.

[0117] Weigh the formulated amounts of nickel source, magnesium source, manganese source, and cobalt source, mix them, add them to deionized water, and stir them thoroughly at a stirring speed of 450 r / min for 60 min to obtain a salt solution, wherein the metal ion concentration in the salt solution is 2 mol / L;

[0118] The salt solution, 30 wt % potassium hydroxide solution and 5 mol / L ammonia solution were mixed at a stirring speed of 500 r / min and a stirring time of 60 min to obtain a precursor material;

[0119] Add the sodium source to the deionized water, then add the precursor material, stirring at a speed of 500 r / min for 60 min;

[0120] The mixed solution was added into an oil bath at 95°C and the layered oxide was obtained after the water was evaporated.

[0121] The layered oxide was placed in a forced air drying oven at a temperature of 115°C for 15 hours at a heating rate of 10°C / min. After drying, it was fully ground and placed in a muffle furnace at 600°C for calcination for 15 hours at a heating rate of 20°C / min. The positive electrode material was obtained by cooling in the furnace.

[0122] Comparative Example

[0123] The difference from Example 1 is that this comparative example uses the nickel source prepared in Preparation Example 1, the manganese source prepared in Preparation Example 9, and the sodium source prepared in Preparation Example 16, and the molar ratio of the nickel source, manganese source, and sodium source is 0.1:1:0.9. The other conditions are exactly the same as in Example 1, and the positive electrode material obtained is Na 0.9 Ni 0.1 MnO2.

[0124] The water absorption performance of the positive electrode materials prepared in the above Examples 1-5 and the comparative example was tested; the test method is as follows:

[0125] 1. After preparing the positive electrode material, set it aside and observe how long it takes for it to become jelly-like;

[0126] 2. Use a Karl Fischer moisture meter to detect the water content of the positive electrode during stacking.

[0127] [Corrected 09.11.2023 according to Rule 91] The test results are shown in Table 1.

[0128] [Corrected 09.11.2023 according to Rule 91] Table 1 Test results of water absorption performance of positive electrode materials in Examples 1-5 and Comparative Examples

[0129] [Corrected on 09.11.2023 according to Rule 91] It can be seen from Examples 1-5, the comparative examples and Table 1 that the positive electrode material prepared in the present application will not become jelly-like until it is left for at least 2.5 hours, especially the positive electrode material prepared in Example 2, which becomes jelly-like only after being left for more than 3 hours; while the positive electrode material in the comparative example becomes jelly-like after only 1 hour; therefore, it can be seen that the positive electrode material prepared in the present application has greatly reduced water absorption performance during the shelf life of the positive electrode preparation compared with the positive electrode material in the comparative example.

[0130] After preparing positive electrode sheets using the positive electrode materials in Examples 1-5 and the comparative example, the water content of the positive electrode sheets during lamination was measured; the water content of the positive electrode sheets corresponding to Examples 1-5 was all below 100 ppm, while the water content of the positive electrode sheets corresponding to the comparative example reached 160 ppm, which was much higher than the water content of the positive electrode sheets corresponding to Examples 1-5; in particular, the water content of the positive electrode sheet corresponding to Example 2 was less than 80 ppm, which was more than doubled compared to the comparative example.

[0131] Battery preparation: Use the positive electrode materials prepared in Examples 1-5 and the comparative examples as the positive electrode materials of the sodium ion battery, use hard carbon as the negative electrode material, and use NaPF6 as the electrolyte as the sodium salt electrolyte to prepare a 3Ah soft-pack sodium ion battery; obtain battery 1-6.

[0132] The battery prepared above was tested for 1000 cycles at room temperature and the reversible specific capacity of the first cycle.

[0133] Battery performance test: 500th / 1000th week capacity retention rate:

[0134] At 25°C, batteries numbered 1-6 were charged at 0.3C constant current and constant voltage to 4V, cut off at 0.05C, and then discharged at 0.3C constant current to 2V. After 1000 charge and discharge cycles, the 1000th cycle capacity retention rate was calculated using the formula: 500th / 1000th cycle capacity retention rate = 500th / 1000th cycle discharge capacity / first cycle discharge capacity × 100%.

[0135] 0.5C reversible specific capacity = first-cycle discharge capacity / mass of active material contained in the positive electrode.

[0136] [Corrected 09.11.2023 according to Rule 91] The performance test results of Battery 1 to Battery 6 are shown in Table 2.

[0137] [Corrected 09.11.2023 according to Rule 91] Table 2 Performance test data of battery 1 to battery 6

[0138] By comparing the performance test data of Battery 1 to Battery 6, it can be seen that the 500-week capacity retention rates of Battery 1-5 corresponding to Examples 1-5 are all 83% or above, which is much higher than the 70% of Battery 6 corresponding to the comparative document; and the 1000-week capacity retention rates of Battery 1-5 corresponding to Examples 1-5 are all 81% or above, which is much higher than the 63% of Battery 6 corresponding to the comparative document.

[0139] Moreover, the capacity retention rate of batteries 1-5 corresponding to Examples 1-5 decreased by 2.4%-8% from 500 weeks to 1000 weeks; the decrease in the capacity retention rate of battery 6 corresponding to the comparative example was 10%. Therefore, it can be concluded that the batteries 1-5 made of the positive electrode materials prepared in the present application not only have a high capacity retention rate at the 500 / 1000th week, but also have a capacity retention rate decrease of 2.4%-8% from 500 weeks to 1000 weeks, which is lower than the 10% of the battery 6 corresponding to the comparative example. It can be seen that the capacity retention rate of batteries 1-5 corresponding to the positive electrode materials prepared in the present application decreases less than that of battery 6 as the number of cycles increases. It can be concluded that the stability of the positive electrode material prepared in the present application is always better than that of the positive electrode material prepared in the comparative example as the number of cycles of the battery increases.

[0140] [Corrected 09.11.2023 according to Rule 91] It can also be seen from the performance data of batteries 1-6 and Table 2 that the 0.5C reversible specific capacity of batteries 1-5 corresponding to Examples 1-5 of the present application are all above 120 mAh / g, while the 0.5C reversible specific capacity of battery 6 corresponding to the comparative example does not reach 110 mAh / g.

[0141] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A transition metal layered oxide sodium battery positive electrode material, characterized in that: The chemical formula of the positive electrode material is Na a Ni b Mg c Co d MnO2, where 0.75≤a≤0.9, 0.1≤b≤0.75, 0.1≤c≤0.25, 0.1≤d≤0.

4.

2. The positive electrode material according to claim 1, characterized in that The raw materials of the positive electrode material include a nickel source, a magnesium source, a manganese source, a cobalt source and a sodium source; wherein: The nickel source is one or more of nickel acetate, nickel nitrate, and nickel sulfate; and / or The magnesium source is one or more of magnesium chloride, magnesium sulfate and magnesium nitrate; and / or The manganese source is one or more of manganese nitrate, manganese acetate, manganese sulfate and manganese oxalate; and / or The cobalt source is one or more of cobalt acetate, cobalt sulfate, cobalt nitrate, and cobalt oxalate; and / or The sodium source is one or more of sodium acetate, sodium chloride, sodium nitrate and sodium sulfate.

3. The positive electrode material according to claim 1, characterized in that The median particle size D50 of the positive electrode material is 1 to 20 μm.

4. The positive electrode material according to claim 1, characterized in that The positive electrode material is a layered 03 type structure.

5. A method for preparing the positive electrode material according to claim 1, characterized in that: The following steps are involved: Weigh the nickel source, magnesium source, manganese source and cobalt source in the formula, mix them and add them into deionized water to obtain a salt solution with a metal ion concentration of 1.0 to 2.0 mol / L; mixing a salt solution, a precipitant, and a complexing agent to obtain a precursor material; Adding a formulated amount of sodium source into deionized water, then adding the precursor material, stirring and mixing, and evaporating the water to obtain a layered oxide; The layered oxide is dried, fully ground, calcined, and cooled to obtain a positive electrode material.

6. The preparation method according to claim 5, characterized in that: The precipitant is a 25-35wt% potassium hydroxide solution.

7. The preparation method according to claim 5, characterized in that: The complexing agent is a 5-10 mol / L ammonia solution, and in the process of mixing the salt solution, the precipitant and the complexing agent to obtain the precursor material, the ammonia concentration is always controlled to be 0.25-0.35 mol / L, and the pH is always controlled to be 10-11.

8. The preparation method according to claim 5, characterized in that: Mix the nickel source, magnesium source, manganese source and cobalt source and add them into deionized water, with a stirring speed of 300-600 r / min and a stirring time of 60 min; and / or, Mix the salt solution, the precipitant and the complexing agent at a stirring speed of 400 to 600 r / min for 60 min; and / or, After adding the precursor material, the stirring speed is 400-600 r / min and the stirring time is 60 min.

9. The preparation method according to claim 5, characterized in that: The evaporation process is as follows: evaporating to dryness in an oil bath at 95°C; and / or, The drying process is: heating to 115°C at a heating rate of 10°C / min and drying for 15h; and / or, The calcination process is as follows: heating to 600°C at a heating rate of 15-20°C / min and calcining for 15h.

10. Use of the positive electrode material according to claim 1 in the field of sodium ion batteries.

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