Preparation method of low-nickel copper-manganese-based sodium ion battery positive electrode material

Abstract

The application comprises the following steps: obtaining a carbonate precursor through a modified coprecipitation reaction by using a nickel source, a manganese source, a copper source and a carbonate precipitation complexing agent, uniformly mixing the carbonate precursor with carbon nanotubes and then adding a sodium source, and calcining the mixture to obtain a positive electrode material. The application uses a lower proportion of nickel to prepare a copper-manganese-based sodium-ion battery positive electrode material, the structure of which is more stable, has good ion conductivity and improves the discharge specific capacity. The precursor is mixed with carbon nanotubes and sintered, which significantly hinders the promotion of the grain and the grain boundary, maintains the stability of the crystal phase structure and solves the problem of crystal phase transformation. The carbon nanotubes form a network structure of electronic conduction structure after sintering, reduces the contact between the positive electrode material and the electrolyte, suppresses the occurrence of side reactions, is stable in structure under high-voltage conditions and improves the cycle performance of the material. The synthesis method is simple, easy to operate, has a short synthesis period and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sodium-ion battery cathode materials, and particularly relates to a preparation method of a low-nickel copper-manganese-based sodium-ion battery cathode material. BACKGROUND

[0002] Sodium-ion batteries have become a research hotspot in battery technology in recent years due to their abundant raw materials, low cost, high safety and other characteristics. Since the radius of sodium ions is larger than that of lithium ions, the current research key is to develop electrode materials that can stably and quickly deintercalate sodium ions. Researchers have made a lot of efforts to improve the electrochemical properties and structural stability of sodium-ion battery cathode materials.

[0003] Sodium nickel manganese oxide, as a classic sodium battery cathode material, has been favored by many energy storage researchers due to its high specific capacity, high working voltage and stability in air. However, during the charging and discharging process, the transition metal layer will slide due to the change of Na concentration in the material, and the P2 phase will undergo P2-O2 transformation, accompanied by serious capacity decay. In order to improve the electrochemical performance of sodium nickel manganese oxide cathode material, the main method currently adopted by researchers is to improve the performance of the material from different angles through doping substitution, surface coating and other methods.

[0004] For example, CN115064670A discloses a preparation method of a doped and coated modified sodium nickel manganese oxide cathode material, comprising the following steps: (1) using a hydrogen peroxide solution to perform surface treatment on the sodium nickel manganese oxide cathode material to obtain a surface-treated sodium nickel manganese oxide cathode material; (2) mixing the surface-treated sodium nickel manganese oxide cathode material in step (1) with a sodium salt and MgO powder, performing grinding treatment, and then performing calcination treatment to obtain the doped and coated modified sodium nickel manganese oxide cathode material. A sodium-poor sodium nickel manganese oxide cathode material is prepared by using a simple surface treatment method, and then MgO and a sodium source are mixed and calcined, so that a sodium nickel manganese oxide cathode material coated with Mg2+ doped Mg0.4Ni0.6O on the surface is prepared by one-step reaction, thereby achieving the purpose of improving the cycle stability and rate performance of the material.

[0005] CN114388794A discloses a sodium-ion battery aluminum-doped zinc oxide coated sodium nickel manganese oxide cathode material and a preparation method thereof. The cathode material has a core-shell structure, and aluminum-doped zinc oxide is coated on the surface of the sodium nickel manganese oxide. The preparation method of the cathode material is to add the sodium nickel manganese oxide into an aqueous solution containing an aluminum source, a zinc source and a complexing agent to obtain a gel, dry the gel to obtain a dry gel, grind the dry gel, and then calcine the dry gel under air to obtain the aluminum-doped zinc oxide coated sodium nickel manganese oxide.

[0006] Although the electrochemical performance of the sodium-ion battery positive electrode material is improved to some extent, the operation process is complex, the cost is high, and the conductivity, specific capacity and cycle performance still have further space for improvement. Therefore, it has very important practical significance to provide a preparation method of a doped and coated modified sodium nickel manganese acid positive electrode material which has a simple doping and coating process and good electrochemical performance. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a low-nickel copper-manganese-based sodium-ion battery positive electrode material, which has a simple process, low cost, and the obtained positive electrode material has better conductivity, specific capacity, rate characteristics and longer cycle life.

[0008] To achieve this purpose of the application, the following technical solutions are adopted:

[0009] A preparation method of a low-nickel copper-manganese-based sodium-ion battery positive electrode material, the preparation method comprising the following steps:

[0010] (1) Add a nickel source, a manganese source and a copper source to pure water, and finely grind by sand milling to obtain a mixed solution A; dissolve a carbonate in pure water to obtain a solution B; the sand milling speed is 1800-2500 rpm, and the sand milling time is 0.5-2 h; the ratio of the nickel source, the copper source and the manganese source is (0.01-0.03):(0.20-0.40):(0.60-0.80);

[0011] (2) The solution A and the solution B in step (1) are added to a reaction kettle containing a bottom liquid to perform a co-precipitation reaction, and a carbonate precursor is obtained; during the co-precipitation reaction, the particle size is controlled to be 2-8 um, the reaction temperature is controlled to be 40-70℃, the stirring speed is controlled to be 400-800 rpm, the reaction pH is controlled to be 7-9, and the reaction time is controlled to be 10-20 h;

[0012] (3) The carbonate precursor obtained in step (2) is mixed with CNTs, and then a sodium source is added, and the mixture is calcined to obtain the positive electrode material; the amount of the carbon source added is 3-8% of the mass of the precursor.

[0013] The general formula of the positive electrode material is NaxNiaCubMn(1-a-b)O2@CNTs, wherein 0.5≤x<1, 0.01≤a<0.03, and 0.2<b<0.4.

[0014] The nickel source in step (1) is one or more of nickel sulfate, nickel chloride, nickel nitrate or nickel acetate; the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese sesquioxide or manganese acetate; the copper source is one or more of copper sulfate, copper oxide, cuprous oxide, copper chloride, copper nitrate or copper acetate; and the carbonate precipitant is one or more of ammonium bicarbonate, sodium bicarbonate, ammonium carbonate or sodium carbonate.

[0015] The solid content of the solution used for sand milling in step (1) is 20-60%; and the carbonate in solution B is a supersaturated solution with a concentration of 2.0-2.5 mol / L.

[0016] The base solution in step (2) is ammonium bicarbonate, and the concentration of the ammonium bicarbonate is 1.4-1.8 mol / L.

[0017] The sodium source in step (3) is any one or more of sodium hydroxide, sodium carbonate, sodium oxalate, sodium nitrite, disodium hydrogen phosphate, sodium bicarbonate, sodium citrate or sodium lactate.

[0018] The amount of the carbon source added in step (3) is 3-8% of the mass of the precursor; and the amount of the sodium source added is 50-80% of the mass of the precursor.

[0019] In step (3), the sintering is performed at a temperature increasing rate of 2-4 ℃ / min to 700-1000 ℃, and the holding time is 4-6 h.

[0020] The positive electrode material obtained above is assembled into a button cell, the positive electrode material obtained is mixed with conductive carbon black and a binder PVDF at a mass ratio of 8:1:1, and N-methyl pyrrolidone solution is added and mixed uniformly to prepare a positive electrode slurry of the battery. The slurry is coated on an aluminum foil, vacuum dried and roller pressed to form a positive electrode sheet, a sodium metal sheet is used as a negative electrode, a 1 mol / L NaClO4 ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) solution is used as an electrolyte, a glass fiber is used as a separator, and the button cell is assembled in an argon-filled glove box.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] First, the precursor is prepared on the basis of the improvement of the coprecipitation method, which can improve the equipment cycle utilization rate, and the process is simpler and more environmentally friendly. Only one step is needed to complete the synthesis, and the synthesis method is simple, easy to operate, has a short synthesis period, and is suitable for large-scale production.

[0023] Secondly, a low-nickel copper-manganese-based precursor is used, a lower proportion of nickel is used to reduce the cost of raw materials, and the prepared positive electrode material has a more stable structure. The introduction of copper expands the transmission channel of sodium ions, has good ion conductivity, and improves the discharge specific capacity, solving the problems of poor electronic conductivity and slow ion diffusion rate in the prior art. The applicant found that when more nickel was added under this process condition, the electrochemical properties such as capacity and cycle were not better than those of low-nickel materials.

[0024] Thirdly, the low-nickel copper-manganese-based precursor is mixed with carbon nanotubes, and then mixed with sodium salt for sintering, which can significantly hinder the pushing of the grain boundaries of active substances during the reaction, maintain the stability of the crystal structure, and the sintered carbon nanotubes can reduce the contact between the positive electrode material and the electrolyte, inhibit the occurrence of side reactions, maintain the structure stable under high voltage conditions, and improve the cycle performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 FIG. 1 is a scanning electron microscope (SEM) image and element mapping of a low-nickel copper-manganese-based sodium ion battery positive electrode material prepared in Example 1;

[0026] Figure 2 FIG. 3 is a cycle performance diagram of the low-nickel copper-manganese-based sodium ion battery positive electrode material prepared in Example 1;

[0027] Figure 3 FIG. 4 is a rate performance diagram of the low-nickel copper-manganese-based sodium ion battery positive electrode material prepared in Examples 1-6 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. In order to further understand the present application, the present application is further described below in combination with the description and specific preferred embodiments, and these embodiments cannot be understood as limiting the scope of the present application.

[0029] Example 1

[0030] The present embodiment provides a low-nickel copper-manganese-based sodium ion battery positive electrode material, and the preparation method of the positive electrode material is as follows:

[0031] Nickel sulfate, copper oxide, manganese sulfate were weighed according to the molar ratio of 0.02:0.31:0.67, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 1.0 h; 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 15 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0032] The above precursor was mixed with 5% carbon nanotubes, then 67% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 900°C at a rate of 3°C / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0033] Figure 1 The above precursor was mixed with 5% carbon nanotubes, then 67% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 900°C at a rate of 3°C / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0034] Example 2

[0035] Nickel sulfate, copper sulfate, and trimanganese tetraoxide were weighed according to the molar ratio of 0.05:0.30:0.65, and dissolved in pure water to prepare a solution with a solid content of 10% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 1.0 h; 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 15 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0036] The above precursor was mixed with 5% carbon nanotubes, then 67% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 900°C at a rate of 3°C / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0037] Example 3

[0038] Nickel sulfate, copper oxide, manganese sulfate were weighed according to the molar ratio of 0.02:0.45:0.53, and dissolved in pure water to prepare a solution with a solid content of 30% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 1.5 h; 2.1 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.7 mol / L ammonium carbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt to ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 6 μm, the pH value was about 8, the stirring speed was 700 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 5 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0039] The above precursor was mixed with 1% glucose, then 100% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 500°C at a rate of 5°C / min from room temperature under air atmosphere for 10 h, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0040] Example 4

[0041] Nickel sulfate, copper oxide, manganese sulfate were weighed according to the molar ratio of 0.1:0.23:0.67, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 0.5 h; 2.6 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 2.0 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt to ammonium bicarbonate precipitant was controlled to be 1:1.5, the particle size was controlled to be 10 μm, the pH value was about 8, the stirring speed was 900 rpm, and the temperature was 80°C. The co-precipitation reaction was carried out for 25 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0042] The above precursor was mixed with 10% sucrose, then 33% sodium carbonate was added and mixed uniformly, and the mixture was heated to 1100°C at a rate of 4°C / min from room temperature under air atmosphere for 3 h, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0043] Example 5

[0044] Nickel sulfate, copper oxide, manganese chloride were weighed according to the molar ratio of 0.1:0.05:0.85, and dissolved in pure water to prepare a solution with a solid content of 50% for sanding refinement, the sanding machine speed was 1500 rpm, and the time was 2.5 h; 2.4 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.0 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt to ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 300 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 30 h, and after the reaction was completed, the product was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0045] The above precursor was mixed with 9% glucose, then 67% sodium carbonate was added and mixed uniformly, and the mixture was heated to 900°C at a rate of 2°C / min from room temperature under air atmosphere for 6 h, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0046] Example 6

[0047] Nickel nitrate, copper oxide, and manganese sulfate were weighed according to the molar ratio of 0.005:0.31:0.685, and dissolved in pure water to prepare a solution with a solid content of 70% for sanding refinement, the sanding machine speed was 2600 rpm, and the time was 1.5 h; 1.8 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.5 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt to ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 30°C. The co-precipitation reaction was carried out for 15 h, and after the reaction was completed, the product was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0048] The above precursor was mixed with 6% carbon nanotubes, then 75% sodium carbonate was added and mixed uniformly, and the mixture was heated to 800°C at a rate of 3°C / min from room temperature under air atmosphere for 7 h, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that no nickel source is added during batching. The specific experimental conditions are as follows.

[0051] Copper oxide, manganese sulfate were weighed according to the mole ratio of 0.31:0.69, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 1.0 h; 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution, ammonium bicarbonate supersaturated solution was added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50℃. The co-precipitation reaction was carried out for 15 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0052] The above precursor was mixed with 5% carbon nanotubes, then 67% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 900℃ at a rate of 3℃ / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 1 is that no copper source is added during batching. The specific experimental conditions are as follows.

[0055] Nickel sulfate, manganese sulfate were weighed according to the mole ratio of 0.02:0.98, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement, the sanding machine speed was 2000 rpm, and the time was 1.0 h; 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution; 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution, ammonium bicarbonate supersaturated solution was added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50℃. The co-precipitation reaction was carried out for 15 h, and after the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain a carbonate precursor.

[0056] The above precursor was mixed with 5% carbon nanotubes, then 67% sodium bicarbonate was added and mixed uniformly, and the mixture was heated to 900℃ at a rate of 3℃ / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel manganese-based sodium-ion battery positive electrode material was obtained.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that no carbon nanotubes are added before the precursor is mixed with the sodium source. The specific experimental conditions are as follows.

[0059] Nickel sulfate, copper oxide, manganese sulfate were weighed according to the molar ratio of 0.02:0.31:0.67, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement. The sanding machine speed was 2000 rpm, and the time was 1.0 h. 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution. 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 15 h. After the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain the carbonate precursor.

[0060] The above precursor was mixed with 67% sodium bicarbonate, and the mixture was heated to 900°C at a rate of 3°C / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0061] Comparative Example 4

[0062] The only difference between this comparative example and Example 1 is that carbon nanotubes were added after the precursor was mixed with the sodium source. The specific experimental conditions are as follows.

[0063] Nickel sulfate, copper oxide, manganese sulfate were weighed according to the molar ratio of 0.02:0.31:0.67, and dissolved in pure water to prepare a solution with a solid content of 40% for sanding refinement. The sanding machine speed was 2000 rpm, and the time was 1.0 h. 2.3 mol / L ammonium bicarbonate was prepared as a precipitant and complexing agent solution. 1.7 mol / L ammonium bicarbonate solution was prepared as a bottom solution. The mixed metal solution and the ammonium bicarbonate supersaturated solution were added to the above-mentioned bottom solution by peristaltic pump, the ratio of mixed metal salt and ammonium bicarbonate precipitant was controlled to be 1:2, the particle size was controlled to be 5 μm, the pH value was about 8, the stirring speed was 600 rpm, and the temperature was 50°C. The co-precipitation reaction was carried out for 15 h. After the reaction was completed, the mixture was filtered, washed with hot water, and dried to obtain the carbonate precursor.

[0064] The above precursor was mixed with 67% sodium bicarbonate, and the mixture was heated to 900°C at a rate of 3°C / min from room temperature under air atmosphere, and then naturally cooled to room temperature. After crushing and sieving, a low-nickel copper-manganese-based sodium-ion battery positive electrode material was obtained.

[0065] Table 1

[0066] Number Initial charge specific capacity (mAh / g) Initial discharge specific capacity (mAh / g) Initial charge-discharge efficiency (%) Example 1 140.61 128.71 91.54 Example 2 136.42 116.09 85.10 Example 3 134.51 113.69 84.52 Example 4 135.12 107.66 79.68 Example 5 120.44 97.86 81.25 Example 6 101.91 88.14 86.49 Comparative Example 1 96.14 82.43 85.74 Comparative Example 2 82.43 71.49 86.73 Comparative Example 3 73.64 58.55 79.51 Comparative Example 4 80.13 65.18 81.34

[0067] The prepared button cells of the positive electrode materials in Examples 1-6 and Comparative Examples 1-4 were tested using a blue electric tester, with a voltage range of 2.0-4.5V, 0.1C charge-discharge activation for one cycle, to obtain the first charge-discharge specific capacity, the first coulombic efficiency, and the test results are shown in Table 1. Then, the button cells were charged at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and discharged at a constant current of 1C, and cycled for 50 cycles, to obtain the relevant data of the 50th cycle discharge capacity and the 50th cycle capacity retention rate, and other parameters. The test results are shown in Table 2. Figure 2 The prepared button cells of the positive electrode materials in Examples 1-6 and Comparative Examples 1-2 were subjected to rate test using a blue electric tester, with a voltage range of 2.0-4.5V, charged at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C; and discharged at a constant current of 0.1C, 0.2C, 0.5C, 1C, 5C, 10C, and 0.1C, respectively, with a cutoff voltage of 2V. The test results are shown in Table 3. Figure 3

[0068] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all such changes or replacements fall within the protection scope and disclosure scope of the present application.​

Claims

1. A method for preparing a low-nickel copper-manganese-based sodium-ion battery cathode material, characterized in that, The preparation method includes the following steps: (1) Add nickel source, manganese source and copper source to pure water and refine by sand milling to obtain mixed solution A; dissolve carbonate in pure water to obtain solution B; the sand milling speed is 1800-2500 rpm and the sand milling time is 0.5-2h; the ratio of nickel source, copper source and manganese source is (0.01-0.03):(0.20-0.40):(0.60-0.80); (2) Solution A and solution B in step (1) are added to a reaction vessel containing the bottom liquid for co-precipitation reaction to obtain carbonate precursor; during the co-precipitation reaction, the particle size is controlled to be 2-8 μm, the reaction temperature is controlled to be 40-70℃, the stirring speed is 400-800 rpm, the reaction pH is 7-9, and the reaction time is 10-20 h. (3) Mix the carbonate precursor obtained in step (2) with CNTs evenly, then add a sodium source, and calcine the mixture to obtain the cathode material; the amount of CNTs added is 3-8% of the mass of the carbonate precursor; The general formula of the positive electrode material is Na. x Ni a Cu b Mn (1-a-b) O2@CNTs, where 0.5≤x<1, 0.01≤a<0.03, 0.2 <b<0.4; The base solution in step (2) is ammonium bicarbonate, and the concentration of ammonium bicarbonate is 1.4-1.8 mol / L; The amount of sodium source added in step (3) is 50-80% of the mass of the carbonate precursor.

2. The method for preparing a low-nickel copper-manganese-based sodium-ion battery cathode material as described in claim 1, characterized in that: The nickel source mentioned in step (1) is one or more of nickel sulfate, nickel chloride, nickel nitrate or nickel acetate; the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese tetroxide or manganese acetate; the copper source is one or more of copper sulfate, copper oxide, cuprous oxide, copper chloride, copper nitrate or copper acetate; and the carbonate is one or more of ammonium bicarbonate, sodium bicarbonate, ammonium carbonate or sodium carbonate.

3. The method for preparing a low-nickel copper-manganese-based sodium-ion battery cathode material as described in claim 1, characterized in that: In step (1), the solid content of the liquid material used for sand milling is 20-60%; the carbonate in solution B is a supersaturated solution with a concentration of 2.0-2.5 mol / L.

4. The method for preparing a low-nickel copper-manganese-based sodium-ion battery cathode material as described in claim 1, characterized in that: The sodium source mentioned in step (3) is any one or more of sodium hydroxide, sodium carbonate, sodium oxalate, sodium nitrite, disodium hydrogen phosphate, sodium bicarbonate, sodium citrate, or sodium lactate.

5. The method for preparing a low-nickel copper-manganese-based sodium-ion battery cathode material as described in claim 1, characterized in that: In step (3), the calcination is carried out at a heating rate of 2-4℃ / min to 700-1000℃, and the holding time is 4-6h.

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