Surface-modified sodium electric precursor, and preparation method therefor and use thereof

Abstract

The present application provides a surface-modified sodium electric precursor, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: (1) injecting a mixed solution A, a precipitant solution and a complexing agent solution into a base solution in a cocurrent flow manner, and performing a one-step co-precipitation reaction; and (2) switching the mixed solution A into a mixed solution B, and continuing to perform a two-step co-precipitation reaction to obtain a surface-modified sodium electric precursor, wherein the mixed solution A comprises a main metal element and a doped metal element, and the mixed solution B comprises a coating metal element. In the present application, the coating modification of the surface of precursor particles is achieved by means of a heterogeneous precipitation method, such that the coating layer is more uniform and complete, and the thickness and the components are adjustable, which is beneficial to improving the stability and electrochemical performance of the material. The preparation method involved in the present application is simple and easy to implement, and is easy for industrial application.

Description

A surface-modified sodium electrolyte precursor and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries and relates to a surface-modified sodium battery precursor and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy vehicle and energy storage markets, the demand for lithium-ion batteries has exploded, but the limitations of lithium resources have restricted their further development. Sodium-ion batteries have similar working principles and electrochemical properties to lithium-ion batteries, and have potential advantages such as raw material cost advantages, high safety, excellent high and low temperature performance, and high-rate charge and discharge. They are expected to be widely used in markets such as power tools, low-speed vehicles, and energy storage. Cathode materials have a crucial impact on key performance indicators of sodium-ion batteries, such as energy density, power density, cycle life, and safety. The development of high-performance and low-cost cathode materials is an inevitable requirement for promoting the development of sodium-ion batteries. Among the many cathode materials, sodium transition metal layered oxides have received extensive attention and research due to their simple synthesis process and high energy density.

[0003] In the early stages of research, researchers often borrowed the technical route of lithium-ion battery development and replaced the lithium in the lithium-ion battery electrode material with sodium to study the electrode material of sodium-ion batteries, but their overall performance was not as good as that of lithium-ion batteries. On the one hand, the standard electrode potential of Na is 0.3V higher than that of Li, resulting in sodium-ion batteries with similar electrode materials generally having lower operating voltage and energy density than corresponding lithium-ion batteries. On the other hand, the radius of sodium ions (0.102nm) is larger than that of lithium ions (0.076nm), resulting in slow electrochemical reaction kinetics and more likely to cause irreversible phase changes in the structure of the electrode material, which deteriorates the cycle performance of the material. In addition, the air stability of sodium-ion battery positive electrode materials is generally poor, which limits its development and application.

[0004] CN115207325A discloses a coated sodium ion battery positive electrode material. The positive electrode material comprises at least one of the formula Na p Ni x Mn y M 1-x-y O 2-z F z and at least one compound coated with Na p Ni x Mn y M 1-x-y O 2-z F zA lithium-containing compound on the surface of a compound, wherein M is a doping element, the valence of M is n, and +2≤n≤+4; 0.5<p<1.01, 0.1<x<0.9, 0.1<y<0.9, 0≤z≤0.1; and the mass proportion of the lithium-containing compound is 0.02-2.0%.

[0005] CN116845188A discloses a coating method for a positive electrode material and a lithium-sodium battery. The method comprises the following steps: introducing a carbon source during the coating process of the positive electrode material, mixing the coating material with the carbon source, and calcining the mixture in an argon atmosphere to obtain a carbonized coating material, which is then mixed and coated with the positive electrode material to obtain a uniformly coated positive electrode material doped with the metal element in the coating material.

[0006] The above solution uses a dry method (ball milling method) to perform secondary coating on the surface of the material particles. This coating method is difficult to achieve the integrity of the coating layer and is difficult to meet the requirements of uniform and controllable coating thickness.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a surface-modified sodium electrochemical precursor, its preparation method, and application. This application utilizes a heterogeneous precipitation method to achieve surface coating modification of the precursor particles, resulting in a more uniform and complete coating layer with adjustable thickness and composition, which is beneficial for improving the stability and electrochemical performance of the material. The preparation method involved in this application is simple and easy to implement, and is amenable to industrial application.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a method for preparing a surface-modified sodium electrolyte precursor, the preparation method comprising the following steps:

[0012] (1) injecting the mixed solution A, the precipitant solution and the complexing agent solution into the bottom solution in parallel to perform a one-step coprecipitation reaction;

[0013] (2) switching mixed solution A to mixed solution B, and continuing the two-step coprecipitation reaction to obtain a surface-modified sodium electrode precursor;

[0014] The mixed solution A contains a main metal element and a doping metal element, and the mixed solution B contains a coating metal element.

[0015] This application uses a precipitation method to modify a protective layer on the surface of a precursor, namely, using heterogeneous nucleation and growth to achieve surface coating of particles under suitable reaction conditions. This method can make the coating more uniform and complete, and the thickness and composition can be adjusted, thereby further improving the structural stability and air stability of the electrode material, while reducing direct contact between the active material and the electrolyte, and achieving better electrochemical performance.

[0016] In one embodiment, the main metal elements include Ni, Co, and Mn.

[0017] In one embodiment, the doping metal element includes any one of Nb, Nd or Ce, or a combination of at least two of them.

[0018] In one embodiment, the coating metal element includes any one of Cu, Al, Zr, Mg or Ca, or a combination of at least two thereof.

[0019] In one embodiment, the precipitant solution in step (1) comprises an alkali solution.

[0020] In one embodiment, the concentration of the precipitant solution is 1 to 4 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 3 mol / L or 4 mol / L.

[0021] In one embodiment, the complexing agent solution includes any one of ammonia water, oxalic acid solution or citric acid solution, or a combination of at least two of them.

[0022] In one embodiment, the concentration of the complexing agent solution is 1 to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L.

[0023] In one embodiment, the base solution includes a precipitant and a complexing agent.

[0024] In one embodiment, the temperature of the one-step coprecipitation reaction in step (1) is 40-70°C, for example, 40°C, 45°C, 50°C, 60°C or 70°C.

[0025] In one embodiment, the pH of the one-step coprecipitation reaction is 10-12, for example, 10, 10.5, 11, 11.5 or 12.

[0026] In one embodiment, the stirring speed of the one-step co-precipitation reaction is 310-390 rpm, for example, 310 rpm, 320 rpm, 340 rpm, 360 rpm or 390 rpm.

[0027] In one embodiment, the end point of the one-step coprecipitation reaction in step (1) is that the particle size D501 in the system is 3 - 8 μm, for example: 3 μm, 4 μm, 6 μm, 7 μm, 8 μm, etc.

[0028] In one embodiment, the mass fraction of the coating layer in the surface-modified sodium-ion battery precursor in step (2) is 1 - 10%, for example: 1%, 2%, 5%, 8%, 10%, etc.

[0029] In a second aspect, the present application provides a surface-modified sodium-ion battery precursor, which is prepared by the method as described in the first aspect.

[0030] In one embodiment, the surface-modified sodium-ion battery precursor includes a doped core and a hydroxide coating layer provided on the surface of the core.

[0031] In one embodiment, the chemical formula of the doped core is Ni a Co b Mn 1-a-b-c M c (OH)2, 0.4 < a < 1, 0 < b < 0.5, 0 < c ≤ 0.05, and M includes any one or a combination of at least two of Nb, Nd, or Ce.

[0032] In a third aspect, the present application provides a surface-modified sodium-ion battery cathode material, which is prepared by mixing and sintering the surface-modified sodium-ion battery precursor as described in the second aspect with a sodium source.

[0033] In a fourth aspect, the present application provides a sodium-ion battery, which includes the surface-modified sodium-ion battery cathode material as described in the third aspect.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] (1) The present application realizes the coating modification of the surface of the precursor particles through the heterogeneous precipitation method, making the coating layer more uniform and complete, and the thickness and composition adjustable, which is beneficial to improving the stability and electrochemical performance of the material. The preparation method involved in the present application is simple and easy to implement, and is easy to be applied industrially.

[0036] (2) The method described in this application is applicable to various proportions of nickel-cobalt-manganese sodium battery precursors. The first discharge specific capacity of the battery made from the NCM523 sodium battery precursor can reach more than 146.8 mAh / g, and the capacity retention rate after 100 cycles can reach more than 77.4%. The first discharge specific capacity of the battery made from the NCM622 sodium battery precursor can reach more than 161.5 mAh / g, and the capacity retention rate after 100 cycles can reach more than 82.2%. The first discharge specific capacity of the battery made from the NCM811 sodium battery precursor can reach more than 159.2 mAh / g, and the capacity retention rate after 100 cycles can reach more than 80.3%.

[0037] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0038] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0039] Example 1

[0040] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0041] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and cerium sulfate with a molar ratio of Ni:Co:Mn:Ce of 0.5:0.2:0.28:0.02, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a cerium-doped precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.28 Ce 0.02 (OH)2;

[0042] (2) Stop feeding the mixed salt solution and feed the copper sulfate solution to continue the reaction. When the mass fraction of copper hydroxide in the total material reaches 2.0%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0043] Example 2

[0044] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0045] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare a reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and niobium sulfate with a molar ratio of Ni:Co:Mn:Nb of 0.6:0.2:0.15:0.05, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 45°C, pH to be 11.5, ammonia concentration to be 4.5g / L, and stirring speed to be 320rpm to obtain a niobium-doped precursor slurry Ni with a particle size of 7μm. 0.6 Co 0.2 Mn 0.15 Nb 0.05 (OH)2;

[0046] (2) Stop feeding the mixed salt solution and feed the zirconium sulfate solution to continue the reaction. When the mass fraction of zirconium hydroxide in the total material reaches 3.5%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0047] Example 3

[0048] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0049] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and neodymium sulfate with a molar ratio of Ni:Co:Mn:Nd of 0.8:0.1:0.07:0.03, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 65°C, pH to be 10.5, ammonia concentration to be 6.5g / L, and stirring speed to be 380rpm to obtain a neodymium-doped precursor slurry Ni with a particle size of 4μm. 0.8 Co 0.1 Mn 0.07 Nd 0.03 (OH)2;

[0050] (2) Stop feeding the mixed salt solution and feed the magnesium sulfate solution to continue the reaction. When the mass fraction of magnesium hydroxide in the total material reaches 5.0%, stop the reaction, age, wash, and dry to obtain a surface-modified sodium electrolyte precursor.

[0051] Example 4

[0052] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0053] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and cerium sulfate with a molar ratio of Ni:Co:Mn:Ce of 0.5:0.2:0.2:0.1, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a cerium-doped precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.2 Ce 0.1 (OH)2;

[0054] (2) Stop feeding the mixed salt solution and feed the copper sulfate solution to continue the reaction. When the mass fraction of copper hydroxide in the total material reaches 2.0%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0055] Example 5

[0056] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0057] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and cerium sulfate with a molar ratio of Ni:Co:Mn:Ce of 0.5:0.2:0.28:0.02, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a cerium-doped precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.28 Ce 0.02 (OH)2;

[0058] (2) Stop feeding the mixed salt solution and feed the copper sulfate solution to continue the reaction. When the mass fraction of copper hydroxide in the total material reaches 0.5%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0059] Example 6

[0060] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0061] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and cerium sulfate with a molar ratio of Ni:Co:Mn:Ce of 0.5:0.2:0.28:0.02, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a cerium-doped precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.28 Ce 0.02 (OH)2;

[0062] (2) Stop feeding the mixed salt solution and feed the copper sulfate solution to continue the reaction. When the mass fraction of copper hydroxide in the total material reaches 12%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0063] Comparative Example 1

[0064] This embodiment provides a surface-modified sodium electrolyte precursor, which is prepared by the following method:

[0065] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate and manganese sulfate with a molar ratio of Ni:Co:Mn of 0.5:0.2:0.3, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.3 (OH)2;

[0066] (2) Stop feeding the mixed salt solution and feed the copper sulfate solution to continue the reaction. When the mass fraction of copper hydroxide in the total material reaches 2.0%, stop the reaction, age, wash, and dry to obtain the surface-modified sodium electrolyte precursor.

[0067] Comparative Example 2

[0068] This embodiment provides a sodium battery precursor, which is prepared by the following method:

[0069] (1) Pure water, sodium hydroxide solution and ammonia water were added to the reactor to prepare the reaction base liquid. After the base liquid was qualified, a mixed salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and cerium sulfate with a molar ratio of Ni:Co:Mn:Ce of 0.5:0.2:0.28:0.02, sodium hydroxide solution and ammonia water were simultaneously introduced into the reactor for coprecipitation reaction. The reaction temperature was controlled to be 55°C, pH to be 11.0, ammonia concentration to be 5.5g / L, and stirring speed to be 350rpm to obtain a cerium-doped precursor slurry Ni with a particle size of 5μm. 0.5 Co 0.2 Mn 0.28 Ce 0.02 (OH)2, stop the reaction, age, wash and dry to obtain the sodium electrode precursor.

[0070] Performance testing:

[0071] The sodium precursors obtained in the examples and comparative examples were prepared into sodium ion battery positive electrode materials: the precursor powder was mixed with sodium carbonate according to a molar ratio of sodium content to transition metal of 0.9:1, and heated to 600°C at a heating rate of 5°C / min in an air atmosphere for 5 hours, and then heated to 800°C at a heating rate of 3°C / min for 10 hours, and naturally cooled to obtain a sodium ion battery positive electrode material. The sodium ion battery positive electrode materials obtained in each example were prepared into sodium ion batteries, and charge and discharge tests were performed at 50mA / g in the voltage range of 2-4.2V to test their first-week discharge capacity and capacity retention after 100 cycles. The test results are shown in Table 1:

[0072] Table 1

[0073] As can be seen from Table 1, it can be obtained from Examples 1-3 that the method described in the present application is applicable to various proportions of nickel, cobalt, manganese sodium precursors, and the first discharge specific capacity of the battery made from the NCM523 sodium precursor can reach more than 146.8 mAh / g, and the capacity retention rate after 100 cycles can reach more than 77.4%. The first discharge specific capacity of the battery made from the NCM622 sodium precursor can reach more than 161.5 mAh / g, and the capacity retention rate after 100 cycles can reach more than 82.2%. The first discharge specific capacity of the battery made from the NCM811 sodium precursor can reach more than 159.2 mAh / g, and the capacity retention rate after 100 cycles can reach more than 80.3%.

[0074] From the comparison between Example 1 and Example 4, it can be seen that the proportion of the doping element in the surface-modified sodium electrode precursor described in the present application in the metal elements of the precursor needs to be controlled within 0.05. If the amount of doping metal element added is too large, the specific capacity of the positive electrode material will decrease.

[0075] By comparing Example 1 with Examples 5-6, it can be seen that in the surface-modified sodium-ion battery precursor described in the present application, the amount of the coating layer will affect its performance. By controlling the mass fraction of the coating layer in the surface-modified sodium-ion battery precursor to 1 to 10%, the performance of the sodium-ion battery precursor is better. If the mass fraction of the coating layer is too high, the capacity of the positive electrode material will be low. If the mass fraction of the coating layer is too low, the structural stability and cycle performance of the sodium-ion battery cannot be effectively improved.

[0076] From the comparison between Example 1 and Comparative Example 1, it can be seen that the doping of Nb, Nd or Ce can play a role in expanding the lattice, which is beneficial to the insertion and extraction of sodium ions, enhances the structural stability and improves the cycle performance.

[0077] From the comparison between Example 1 and Comparative Example 2, it can be seen that coating with Cu, Al, Zr, Mg or Ca can reduce the side reaction between the electrode and the electrolyte and prevent the dissolution of the transition metal, thereby further improving the cycle stability.

[0078] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A preparation method of a surface-modified sodium battery precursor, comprising the following steps: (1) Injecting a mixed solution A, a precipitant solution, and a complexing agent solution into a bottom solution in parallel to perform a one-step coprecipitation reaction; (2) Switching the mixed solution A to a mixed solution B and continuing to perform a two-step coprecipitation reaction to obtain a surface-modified sodium battery precursor; The mixed solution A contains a main metal element and a doped metal element, and the mixed solution B contains a coating metal element.

2. The preparation method according to claim 1, wherein, The main metal element includes Ni, Co, and Mn; Optionally, the doped metal element includes any one or a combination of at least two of Nb, Nd, or Ce; Optionally, the coating metal element includes any one or a combination of at least two of Cu, Al, Zr, Mg, or Ca.

3. The preparation method according to claim 1 or 2, wherein The precipitant solution in step (1) includes an alkali solution; Optionally, the concentration of the precipitant solution is 1-4 mol / L; Optionally, the complexing agent solution includes any one or a combination of at least two of ammonia water, oxalic acid solution, or citric acid solution; Optionally, the concentration of the complexing agent solution is 1-3 mol / L; Optionally, the bottom solution includes a precipitant and a complexing agent.

4. The preparation method according to any one of claims 1-3, wherein, The temperature of the one-step coprecipitation reaction in step (1) is 40-70 °C; Optionally, the pH of the one-step coprecipitation reaction is 10-12; Optionally, the stirring speed of the one-step coprecipitation reaction is 310-390 rpm.

5. The preparation method according to any one of claims 1-4, wherein, The end point of the one-step coprecipitation reaction in step (1) is that the particle size D501 in the system is 3-8 μm.

6. The preparation method according to any one of claims 1-5, wherein, The mass fraction of the coating layer in the surface-modified sodium battery precursor in step (2) is 1-10%.

7. A surface-modified sodium battery precursor prepared by the method according to any one of claims 1-6.

8. The surface-modified sodium battery precursor according to claim 7, wherein, The surface-modified sodium battery precursor includes a doped core and a hydroxide coating layer provided on the surface of the core; Optionally, the chemical formula of the doped core is Ni a Co b Mn 1-a-b-c M c (OH)2, where 0.4 < a < 1, 0 < b < 0.5, 0 < c ≤ 0.05, and M includes any one or a combination of at least two of Nb, Nd, or Ce.

9. A surface-modified sodium battery cathode material prepared by mixing and sintering the surface-modified sodium battery precursor according to claim 7 or 8 with a sodium source.

10. A sodium ion battery comprising the surface-modified sodium battery cathode material according to claim 9.

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