Copper-doped and coated sodium electric precursor as well as preparation method and application thereof

Abstract

The invention provides a copper-doped and coated sodium electric precursor as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out first coprecipitation reaction on a mixed metal salt solution, a precipitator solution and a complexing agent solution; the mixed metal salt solution comprises nickel ions, iron ions, manganese ions and copper ions; after the first coprecipitation reaction is finished, the pH value of the system is increased, a copper coating preparation stage is started, a second coprecipitation reaction continues to be carried out, after the second coprecipitation reaction is finished, the mixed metal salt solution is replaced with a copper salt solution, the pH value of the system is reduced, a third coprecipitation reaction continues to be carried out, and the copper-doped and coated sodium electric precursor is obtained. According to the preparation method, micro particles are introduced in the coating preparation stage, Cu < 2 + > is brought into a particle system in the stage that large particles adsorb the micro particles to grow, uniform coating is achieved, and finally the precursor which is uniform in element distribution, uniform in structure distribution, high in tap density, high in specific surface area and free of hardening is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a copper-doped coated sodium battery precursor, a preparation method thereof, and an application thereof. Background Art

[0002] As a new energy storage technology, sodium-ion batteries have received extensive attention in recent years. Compared with traditional lithium-ion batteries, sodium-ion batteries have the advantages of rich resources, low cost, environmental friendliness, high safety, great performance potential, and wide application scenarios.

[0003] Layered oxide sodium battery cathode materials have significant advantages and broad development prospects in sodium-ion batteries. Compared with other types of sodium battery cathode materials (such as polyanion compounds, Prussian blue analogs, and organic materials), they show unique competitiveness in terms of performance, cost, and scalability. During the charge and discharge process of layered sodium battery cathode materials, problems such as structural degradation, interfacial side reactions, slow sodium ion diffusion kinetics, transition metal dissolution, and mechanical stress accumulation caused by volume change will be encountered.

[0004] In order to alleviate the performance degradation problem of layered sodium battery cathode materials, various improvement strategies have been proposed in the prior art. Among them, doping or coating Cu in the system can improve the material conductivity, stabilize the crystal structure, improve the electrochemical performance, inhibit phase transformation, and reduce the cost. That is, doping and coating Cu at the precursor end is a way with low economic cost and convenient for subsequent direct industrial production. Generally, the co-precipitation method is used to prepare sodium battery precursors industrially. Since the precipitation coefficient of Cu 2+ differs greatly from that of other metal ions, the doping of Cu 2+ results in segregation of the structure. At the same time, during the Cu coating process, due to the increase in Cu content at this stage, the structure segregation will be more serious.

[0005] In the prior art, for example, CN118877958A uses a method of first preparing a nickel-cobalt-manganese skeleton and then adding a single copper salt to fill the gaps to obtain a sodium battery precursor with a gradient distribution of Cu elements. However, the precursor obtained by this method has poor structural uniformity, and there will also be a problem of uneven distribution of Cu elements in the overall structure. It can be seen from the provided electron microscope images that there are many micropowder structures on the surface. At the same time, since Cu 2+ precipitates in another crystal form, the overall crystallinity is generally low and the tap density is low. Finally, in order to fill the gaps, more Cu 2+ is required, and the doping of more Cu 2+ will have a great impact on the electrochemical performance of the subsequent cathode material.

[0006] Based on the above research, a preparation method of a copper-doped and coated sodium battery precursor is required. The preparation method can achieve uniform doping and coating of copper, and obtain a sodium battery precursor with uniform element distribution, uniform structure, high tap density, high specific surface area and no caking. Summary of the Invention

[0007] The object of the present invention is to provide a copper-doped and coated sodium battery precursor, its preparation method and application. The preparation method obtains a densely grown spherical nucleus through copper doping, and then through the coating preparation stage, introduces fine particles, and brings the Cu 2+ into the particle system during the stage of large particles adsorbing fine particles for growth, realizing uniform coating, and finally obtaining a copper-doped and coated sodium battery precursor with uniform element distribution, uniform structure distribution, high tap density, high specific surface area and no caking.

[0008] To achieve the object of the present invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method of a copper-doped and coated sodium battery precursor, and the preparation method includes the following steps:

[0010] (1) Perform a first co-precipitation reaction on a mixed metal salt solution, a precipitant solution and a complexing agent solution;

[0011] The mixed metal salt solution includes nickel ions, iron ions, manganese ions and copper ions;

[0012] (2) After the first co-precipitation reaction in step (1) ends, raise the pH of the system, enter the copper coating preparation stage, and continue to perform a second co-precipitation reaction;

[0013] (3) After the second co-precipitation reaction in step (2) ends, replace the mixed metal salt solution in step (1) with a copper salt solution, lower the pH of the system, enter the copper coating stage, and continue to perform a third co-precipitation reaction to obtain the copper-doped and coated sodium battery precursor.

[0014] The present invention first performs a first co-precipitation reaction on a mixed metal salt solution including copper ions to obtain a spherical nucleus doped with copper and densely grown, then raises the pH of the co-precipitation system, introduces fine particles in the copper coating preparation stage, then lowers the pH of the system, and replaces the mixed metal salt solution with a copper salt solution for copper coating. Therefore, the present invention introduces fine particles in the copper coating preparation stage. The fine particles will be adsorbed by large particles during particle growth, and copper ions will be brought into the particle system when large particles adsorb fine particles for growth, realizing uniform coating of copper, and finally obtaining a Cu-coated and doped sodium battery precursor with uniform element distribution, uniform structure distribution, high tap density, high specific surface area and no caking.

[0015] Preferably, the pH of the second coprecipitation reaction in step (2) is 11.0 - 11.5. For example, it can be 11.0, 11.1, 11.2, 11.3, 11.4, or 11.5, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0016] The pH of the second coprecipitation reaction in the present invention affects the growth of fine particles. Preferably within a specific range, if the pH of the second coprecipitation reaction is too small, too few fine particles are generated, which will affect the uniformity of copper ion coating. If the pH of the second coprecipitation reaction is too large, on the one hand, too many fine particles are generated, resulting in agglomeration between small particles and unable to be adsorbed by large particles. On the other hand, the pH fluctuation during the switching of the two reaction stages is too large, the reaction is in a non-steady state, and both large and small particles are prone to agglomeration, resulting in a drastic decrease in the dispersibility of the prepared precursor, thus deteriorating the performance indicators of the precursor.

[0017] Preferably, the time of the second coprecipitation reaction in step (2) is 2 - 8 h. For example, it can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0018] The time of the second coprecipitation reaction in the present invention affects the amount of fine particles generated. If the time of the second coprecipitation reaction is too short, too few fine particles are generated, which is not conducive to copper coating. If the time of the second coprecipitation reaction is too long, too many fine particles are generated, resulting in agglomeration between small particles and unable to be adsorbed by large particles, and finally forming a precursor with a spherical morphology of different sizes, which is not conducive to the subsequent copper coating process.

[0019] Preferably, the concentration of the complexing agent in the second coprecipitation reaction in step (2) is 0.1 - 0.7 mol / L. For example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, or 0.7 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the pH of the third coprecipitation reaction in step (3) is 7.0 - 11.0. For example, it can be 7.0, 8.0, 9.0, 10.0, or 11.0, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the concentration of the complexing agent in the third co-precipitation reaction in step (3) is 0.1-0.7 mol / L. For example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L or 0.7 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0022] Preferably, after the third co-precipitation reaction in step (3) yields particles with a D50 particle size of 4.0-12.6 μm, the reaction is stopped. For example, it can be 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm or 12.6 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the concentration of the copper salt solution in step (3) is 0.5-1.0 mol / L. For example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the flow rate of the copper salt solution in step (3) is 1-15 L / h. For example, it can be 1 L / h, 3 L / h, 5 L / h, 7 L / h, 9 L / h, 11 L / h, 13 L / h or 15 L / h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the temperatures of the third co-precipitation reaction in step (3), the second co-precipitation reaction in step (2), and the first co-precipitation reaction in step (1) are each independently 30-80 °C. For example, it can be 30 °C, 40 °C, 50 °C, 60 °C, 70 °C or 80 °C, and the atmospheres each independently include air and a protective gas.

[0026] The present invention conducts co-precipitation in air and a protective gas. That is, after incorporating a certain proportion of Cu into the oxidation system, it will promote the growth of a fine and dense structure of the precursor, improving the tap density and BET of the precursor.

[0027] Preferably, the protective gas includes any one or a combination of at least two of helium, nitrogen or argon.

[0028] Preferably, in the air and the protective gas, the proportion of air is 20 - 80 vol%, for example, it can be 20 vol%, 30 vol%, 40 vol%, 50 vol%, 60 vol%, 70 vol% or 80 vol%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the total flow rate of the air and the protective gas is 2 - 25 L / min, for example, it can be 2 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min or 25 L / min, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the pH of the first coprecipitation reaction in step (1) is 7.0 - 11.0, for example, it can be 7.0, 8.0, 9.0, 10.0 or 11.0, and the complexing agent concentration is 0.1 - 0.7 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L or 0.7 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, after the first coprecipitation reaction in step (1), particles with a particle size D50 of 3.7 - 12.3 μm are obtained, for example, it can be 3.7 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm or 12.3 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0032] Preferably, in step (1), the mixed metal salt solution, the precipitant solution and the complexing agent solution are introduced into the bottom solution for the first coprecipitation reaction.

[0033] Preferably, the bottom solution includes water, a precipitant and a complexing agent.

[0034] Preferably, the pH of the bottom solution is 11.0 - 13.0, for example, it can be 11.0, 11.5, 12.0, 12.5 or 13.0, and the complexing agent concentration is 0.1 - 0.7 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L or 0.7 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] That is, the pH of the bottom liquid of the present invention is 11.0 - 13.0. After slowly reducing the pH to 7.0 - 11.0, the first coprecipitation reaction is carried out. Then, the pH is slowly increased to 11.0 - 11.5 for the second coprecipitation reaction, and then the pH is slowly reduced to 7.0 - 11.0 for the third coprecipitation reaction. Therefore, the pH of the second coprecipitation reaction is greater than that of the first coprecipitation reaction, and the pH of the third coprecipitation reaction is less than that of the second coprecipitation reaction.

[0036] Preferably, the bottom liquid accounts for 15 - 75% of the volume of the reaction kettle. For example, it can be 15%, 25%, 35%, 45%, 55%, 65% or 75%. The volume of the reaction kettle is 200 - 800L. For example, it can be 200L, 300L, 400L, 500L, 600L, 700L or 800L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0037] Preferably, in the mixed metal salt solution in step (1), the molar ratio of nickel ions, iron ions, manganese ions and copper ions is a:b:c:d, where 0.1 < a < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.1 < b < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.1 < c < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.02 < d < 0.06. For example, it can be 0.021, 0.03, 0.04, 0.05 or 0.059, and a + b + c + d = 1.

[0038] The present invention is based on Ni a Fe b Mn c Cu d A mixed metal salt solution is prepared according to the molecular formula of (OH)2, where a + b + c + d = 1, 0.1 < a < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.1 < b < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.1 < c < 0.5. For example, it can be 0.11, 0.2, 0.3, 0.4 or 0.49, 0.02 < d < 0.06. For example, it can be 0.021, 0.03, 0.04, 0.05 or 0.059, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the total metal ion concentration of the mixed metal salt solution in step (1) is 1.0 - 3.0 mol / L. For example, it can be 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, or 3.0 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0040] Preferably, the flow rate of the mixed metal salt solution in step (1) is 2 - 30 L / h. For example, it can be 2 L / h, 5 L / h, 10 L / h, 15 L / h, 20 L / h, 25 L / h, or 30 L / h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0041] Preferably, the concentration of the precipitant solution in step (1) is 1 - 10 mol / L. For example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the precipitant solution in step (1) includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate.

[0043] Preferably, the concentration of the complexing agent solution in step (1) is 1 - 10 mol / L. For example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0044] Preferably, the complexing agent solution in step (1) includes any one or a combination of at least two of ammonia water, ammonium bicarbonate, ammonium sulfate, oxalic acid, sodium oxalate, citric acid, sodium citrate, EDTA, tartaric acid, sodium tartrate, or sodium hexametaphosphate.

[0045] In a second aspect, the present invention provides a sodium - ion battery cathode precursor doped with copper and coated, and the sodium - ion battery cathode precursor doped with copper and coated is prepared by using the preparation method as described in the first aspect.

[0046] In a third aspect, the present invention provides a sodium - ion battery cathode material, and the sodium - ion battery cathode material is obtained by mixing and sintering a sodium source and the sodium - ion battery cathode precursor doped with copper and coated as described in the second aspect.

[0047] In a fourth aspect, the present invention provides a sodium - ion battery, and the sodium - ion battery includes the sodium - ion battery cathode material as described in the third aspect.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] Due to the increase in Cu content during the copper coating stage, it is difficult to achieve uniform copper coating by traditional growth methods. However, in the present invention, after manufacturing a small amount of fine particles through the copper coating preparation stage before coating, in the subsequent stage, during the process of large particles absorbing fine particles, Cu 2+ can be perfectly introduced into the structure to achieve uniform coating; moreover, when doping copper in the present invention, the oxidation method can achieve uniform doping of Cu, and the obtained precursor has a uniform structure. At the same time, after adding a certain proportion of Cu to the oxidation system, it will promote the growth of a fine and dense structure of the precursor, improve the tap density of the precursor, and moderately increase the BET. Specific embodiments

[0050] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0051] Example 1

[0052] This example provides a preparation method for a sodium-ion battery precursor doped with copper and coated, and the preparation method includes the following steps:

[0053] (1) According to the molecular formula Ni 0.29 Fe 0.33 Mn 0.36 Cu 0.02 Prepare a mixed metal salt solution with a concentration of 1.8 mol / L, prepare a mixed solution of sodium hydroxide and potassium hydroxide with a concentration of 6 mol / L as a precipitant solution (the molar ratio of sodium hydroxide to potassium hydroxide is 1:1), and prepare a mixed solution of ammonia water, sodium tartrate and sodium hexametaphosphate with a concentration of 3 mol / L as a complexing agent solution (the molar ratio of ammonia water, sodium tartrate and sodium hexametaphosphate is 2:1:1);

[0054] (2) In a reaction kettle with a volume of 600 L, add pure water accounting for 23% of the kettle volume as the bottom liquid, control the pH of the bottom liquid to be 11.9, the complexing agent concentration to be 0.5 mol / L, and introduce a mixed gas of helium, argon and air (the air accounts for 30 vol%), the total flow rate of the mixed gas is L / min, and carry out subsequent reactions at a temperature of 37 °C;

[0055] (3) Cu doping stage: Feed the mixed metal salt solution, precipitant solution, and complexing agent solution described in step (1). Among them, the flow rate of the mixed metal salt solution is 21 L / h, and the first coprecipitation reaction is carried out under the conditions of pH = 8.3 and a complexing agent concentration of 0.5 mol / L to obtain particles with a D50 particle size of 3.9 μm;

[0056] (4) Cu coating preparation stage: Slowly increase the pH of the system to 11.1, control the complexing agent concentration to 0.5 mol / L, and carry out the second coprecipitation reaction for 3 h;

[0057] (5) Cu coating stage: After the second coprecipitation reaction described in step (2) ends, replace the mixed metal salt solution described in step (1) with a copper salt solution with a concentration of 0.7 mol / L, feed it into the system at a flow rate of 10 L / h, and lower the pH of the system to 8.3 with a complexing agent concentration of 0.5 mol / L, and carry out the third coprecipitation reaction to obtain the copper-doped and coated sodium battery precursor with a D50 particle size of 4.2 μm.

[0058] Example 2

[0059] This example provides a method for preparing a copper-doped and coated sodium battery precursor, and the preparation method includes the following steps:

[0060] (1) According to the molecular formula Ni 0.3 Fe 0.3 Mn 0.36 Cu 0.04 (OH)2, prepare a mixed metal salt solution with a concentration of 1.0 mol / L, prepare a sodium hydroxide solution with a concentration of 1 mol / L as the precipitant solution, and prepare a mixed solution of ammonia water, sodium tartrate, and sodium hexametaphosphate with a concentration of 1 mol / L as the complexing agent solution (the molar ratio of ammonia water, sodium tartrate, and sodium hexametaphosphate is 2:2:1);

[0061] (2) In a reaction kettle with a volume of 600 L, add pure water accounting for 23% of the kettle volume as the bottom liquid, control the pH of the bottom liquid to 13, the complexing agent concentration to 0.7 mol / L, and feed a mixed gas of helium, argon, and air (the air accounts for 20 vol%), the total flow rate of the mixed gas is 5 L / min, and carry out subsequent reactions at a temperature of 50 °C;

[0062] (3) Cu doping stage: Feed the mixed metal salt solution, precipitant solution, and complexing agent solution described in step (1). Among them, the flow rate of the mixed metal salt solution is 30 L / h, and the first coprecipitation reaction is carried out under the conditions of pH = 11.0 and a complexing agent concentration of 0.7 mol / L to obtain particles with a D50 particle size of 5 μm;

[0063] (4) Cu Coating Preparation Stage: Slowly increase the pH of the system to 11.5, control the complexing agent concentration at 0.7 mol / L, and conduct the second co-precipitation reaction for 8 h;

[0064] (5) Cu Coating Stage: After the completion of the second co-precipitation reaction described in step (2), replace the mixed metal salt solution described in step (1) with a copper salt solution with a concentration of 1.0 mol / L, introduce it into the system at a flow rate of 1 L / h, and lower the pH of the system to 11.0, with the complexing agent concentration at 0.7 mol / L, and conduct the third co-precipitation reaction to obtain the sodium-ion battery precursor with a particle size D50 of 6 μm coated with copper doping.

[0065] Example 3

[0066] This example provides a method for preparing a sodium-ion battery precursor coated with copper doping, and the preparation method includes the following steps:

[0067] (1) Prepare a mixed metal salt solution with a concentration of 3.0 mol / L according to the molecular formula Ni 0.29 Fe 0.31 Mn 0.35 Cu 0.05 (OH)2, prepare a sodium hydroxide solution with a concentration of 10 mol / L as the precipitant solution, and prepare a mixed solution of ammonia water, sodium tartrate and sodium hexametaphosphate with a concentration of 10 mol / L as the complexing agent solution (the molar ratio of ammonia water, sodium tartrate and sodium hexametaphosphate is 2:1:2);

[0068] (2) In a reaction kettle with a volume of 600 L, add pure water accounting for 23% of the kettle volume as the bottom liquid, control the pH of the bottom liquid at 11, the complexing agent concentration at 0.1 mol / L, and introduce a mixed gas of helium, argon and air (the air accounts for 50 vol%), the total flow rate of the mixed gas is 25 L / min, and conduct subsequent reactions at a temperature of 30 °C;

[0069] (3) Cu Doping Stage: Introduce the mixed metal salt solution, precipitant solution and complexing agent solution described in step (1), where the flow rate of the mixed metal salt solution is 5 L / h, and conduct the first co-precipitation reaction under the conditions of pH 7.0 and complexing agent concentration of 0.1 mol / L to obtain particles with a particle size D50 of 3.7 μm;

[0070] (4) Cu Coating Preparation Stage: Slowly increase the pH of the system to 11.0, control the complexing agent concentration at 0.1 mol / L, and conduct the second co-precipitation reaction for 2 h;

[0071] (5) Cu Coating Stage: After the second coprecipitation reaction described in step (2) is completed, replace the mixed metal salt solution described in step (1) with a copper salt solution with a concentration of 0.5 mol / L, introduce it into the system at a flow rate of 15 L / h, and lower the pH of the system to 7.0. The complexing agent concentration is 0.1 mol / L, and a third coprecipitation reaction is carried out to obtain the copper-doped and coated sodium-ion battery precursor with a D50 particle size of 4.5 μm.

[0072] Example 4

[0073] This example provides a method for preparing a copper-doped and coated sodium-ion battery precursor. Except for slowly increasing the pH of the system to 12 for the second coprecipitation reaction in the copper coating preparation stage, the rest are the same as in Example 1.

[0074] Example 5

[0075] This example provides a method for preparing a copper-doped and coated sodium-ion battery precursor. Except for slowly increasing the pH of the system to 10.5 for the second coprecipitation reaction in the copper coating preparation stage, the rest are the same as in Example 1.

[0076] Example 6

[0077] This example provides a method for preparing a copper-doped and coated sodium-ion battery precursor. Except for the second coprecipitation reaction time being 9 h in the copper coating preparation stage, the rest are the same as in Example 1.

[0078] Example 7

[0079] This example provides a method for preparing a copper-doped and coated sodium-ion battery precursor. Except for the second coprecipitation reaction time being 1 h in the copper coating preparation stage, the rest are the same as in Example 1.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a copper-doped and coated sodium-ion battery precursor. Except for not performing the copper coating preparation stage in step (4), the rest are the same as in Example 1.

[0082] The tap densities and specific surface areas of the copper-doped and coated sodium-ion battery precursors obtained in the above examples and comparative examples are shown in Table 1:

[0083] Table 1

[0084] <![CDATA[Tap density (g / cm 3 )]]> <![CDATA[Specific surface area (m 2 / g) <!-- 6 -->]]> Example 1 1.69 63 Example 2 1.82 54 Example 3 1.64 66 Example 4 1.32 121 Example 5 1.52 142 Example 6 1.41 106 Example 7 1.47 133 Comparative Example 1 1.22 189

[0085] As can be seen from Table 1:

[0086] It can be seen from Example 1 and Comparative Example 1 that before copper coating in the present invention, the pH of the system is first increased to introduce fine particles. When large particles attract fine particles, copper is coated on the surface of the particles, thereby improving the distribution and coating uniformity of copper and further increasing the tap density of the precursor. For example, the tap density of Comparative Example 1 can be increased from 1.22 g / cm 3 to 1.69 g / cm of Example 1 3 , and the specific surface area of Example 1 is within a suitable range; it can be seen from Example 1 and Examples 4-5 that the pH in the copper coating preparation stage of the present invention affects the generation of fine particles, thereby affecting the tap density of the material, etc.; it can be seen from Example 1 and Examples 6-7 that the time taken in the copper coating preparation stage of the present invention affects the amount of fine particles generated, thereby affecting the copper coating and the tap density and other properties of the precursor material.

[0087] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a copper-doped sodium electrode precursor, characterized in that: The preparation method comprises the following steps: (1) subjecting a mixed metal salt solution, a precipitant solution and a complexing agent solution to a first coprecipitation reaction; The mixed metal salt solution includes nickel ions, iron ions, manganese ions and copper ions; (2) After the first coprecipitation reaction in step (1) is completed, the pH of the system is increased, the copper coating preparation stage is entered, and the second coprecipitation reaction is continued; (3) After the second coprecipitation reaction in step (2) is completed, the mixed metal salt solution in step (1) is replaced with a copper salt solution to lower the pH of the system, enter the copper coating stage, and continue the third coprecipitation reaction to obtain the copper-doped and coated sodium electrode precursor.

2. The preparation method according to claim 1, characterized in that: Step (2) the pH of the second coprecipitation reaction is 11.0-11.5; Preferably, the second coprecipitation reaction time in step (2) is 2-8 hours; Preferably, the concentration of the complexing agent in the second coprecipitation reaction in step (2) is 0.1-0.7 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The pH of the third coprecipitation reaction in step (3) is 7.0-11.0; Preferably, the concentration of the complexing agent in the third coprecipitation reaction in step (3) is 0.1-0.7 mol / L; Preferably, after the third coprecipitation reaction in step (3) obtains particles with a particle size D50 of 4.0-12.6 μm, the reaction is stopped.

4. The preparation method according to any one of claims 1 to 3, characterized in that The concentration of the copper salt solution in step (3) is 0.5-1.0 mol / L; Preferably, the flow rate of the copper salt solution in step (3) is 1-15 L / h.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperatures of the third coprecipitation reaction in step (3), the second coprecipitation reaction in step (2) and the first coprecipitation reaction in step (1) are independently 30-80° C., and the atmospheres are independently air and protective gas; Preferably, in the air and the protective gas, the proportion of air is 20-80 vol%; Preferably, the total flow rate of the air and the protective gas is 2-25 L / min.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (1) The pH of the first coprecipitation reaction is 7.0-11.0, and the concentration of the complexing agent is 0.1-0.7 mol / L; Preferably, after the first coprecipitation reaction in step (1) is completed, particles with a particle size D50 of 3.7-12.3 μm are obtained; Preferably, in step (1), the mixed metal salt solution, the precipitant solution and the complexing agent solution are introduced into the base solution to perform a first coprecipitation reaction; Preferably, the pH of the base solution is 11.0-13.0, and the concentration of the complexing agent is 0.1-0.7 mol / L.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In the mixed metal salt solution of step (1), the molar ratio of nickel ion, iron ion, manganese ion and copper ion is a:b:c:d, wherein 0.1<a<0.5, 0.1<b<0.5, 0.1<c<0.5, 0.02<d<0.06, a+b+c+d=1; Preferably, the total metal ion concentration of the mixed metal salt solution in step (1) is 1.0-3.0 mol / L; Preferably, the flow rate of the mixed metal salt solution in step (1) is 2-30 L / h; Preferably, the concentration of the precipitant solution in step (1) is 1-10 mol / L; Preferably, the concentration of the complexing agent solution in step (1) is 1-10 mol / L.

8. A copper-doped sodium electrode precursor, characterized in that: The copper-doped and coated sodium electrode precursor is prepared by the preparation method according to any one of claims 1 to 7.

9. A sodium positive electrode material, characterized in that: The sodium-based positive electrode material is obtained by mixing and sintering a sodium source and the copper-doped and coated sodium-based precursor as described in claim 8.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium positive electrode material as claimed in claim 9.