Vanadium gradient doped sodium battery positive electrode material, preparation method therefor, and use thereof

Abstract

A vanadium gradient doped sodium battery positive electrode material, a preparation method therefor, and the use thereof. The preparation method comprises the following steps: (1) mixing a vanadium source and a complexing agent solution to obtain a vanadium-containing mixed solution, conducting concurrent flow addition of a nickel-copper-iron-manganese mixed salt solution, the vanadium-containing mixed solution, a precipitating agent solution, and a complexing agent solution into a base solution, performing a co-precipitation reaction, and obtaining a sodium battery precursor; and (2) mixing the sodium battery precursor with a sodium source, performing sintering, and obtaining the vanadium gradient doped sodium battery positive electrode material; wherein during the co-precipitation reaction, the feed rate of the vanadium-containing mixed solution gradually increases while the feed rate of another solution remains unchanged. By means of first dissolving a vanadate in a complexing agent and then carrying out precipitation during a reaction, wet preparation of a vanadium-doped precursor is implemented, and by means of vanadium gradient doping, the prepared positive electrode material acquires better long cycle performance.

Description

A vanadium gradient-doped sodium cathode material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of sodium ion batteries and relates to a vanadium gradient-doped sodium battery positive electrode material and a preparation method and application thereof. Background Art

[0002] In recent years, with the increasing use of electronic products, especially the development of the new energy vehicle industry, the demand for high-power, high-energy and high-safety lithium-ion batteries has been driven, prompting people to continuously seek battery systems with better performance. Currently, the commonly used and more mature lithium-ion battery cathode materials are lithium cobalt oxide (LiCoO2), lithium nickel oxide, lithium manganese oxide (Li x Mn2O4), lithium iron phosphate (LiFePO4), etc. However, lithium resources are limited and unevenly distributed, and the problem of high raw material costs has gradually become prominent.

[0003] Similar to lithium-ion batteries, secondary sodium-ion batteries have become a key development direction in the energy storage field due to their low cost, non-toxicity, and abundant and evenly distributed sodium resources. Like lithium-ion batteries, the energy storage performance of sodium-ion batteries is primarily influenced by the cathode material.

[0004] CN116588994A discloses a sodium ion battery cathode precursor, a sodium ion battery cathode material, a preparation method thereof, and a sodium ion battery. The sodium ion battery cathode precursor has a core-shell structure, wherein the core of the core-shell structure is a nickel-iron-manganese ternary precursor and the outer shell of the core-shell structure is a copper oxide layer.

[0005] CN116081696A discloses a method for preparing a sodium ion battery precursor material and a sodium ion battery positive electrode material. The method for preparing the sodium ion battery precursor material comprises: mixing metal salt solutions to obtain a mixed metal solution; wherein the mixed metal solution comprises one of a chloride solution, a sulfate solution, and a nitrate solution, and the metal source in the mixed metal solution comprises a mixture of multiple metals selected from copper, iron, manganese, nickel, cobalt, chromium, zinc, and calcium; spray pyrolysis of the mixed metal solution to obtain a precursor powder; and post-processing the precursor powder to obtain the sodium ion battery precursor material.

[0006] Although the above solutions have advantages in cost or energy density, their cycle performance is not ideal and cannot meet the application of sodium-ion batteries in the energy storage field.

[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 the present application is to provide a vanadium gradient-doped sodium cathode material, a preparation method and application thereof. The present application prepares a vanadium-doped precursor by a wet method by first dissolving vanadate in a chelating agent and then precipitating it in the reaction. By vanadium gradient doping, the prepared cathode material has good long-cycle performance.

[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 vanadium gradient-doped sodium cathode material, the preparation method comprising the following steps:

[0012] (1) mixing a vanadium source and a complexing agent solution to obtain a vanadium-containing mixed solution, and injecting a nickel-copper-iron-manganese mixed salt solution, the vanadium-containing mixed solution, a precipitant solution, and a complexing agent solution into the bottom liquid in parallel to perform a coprecipitation reaction to obtain a sodium electrode precursor;

[0013] (2) mixing the sodium battery precursor with a sodium source, and sintering the mixture to obtain the vanadium gradient-doped sodium battery positive electrode material;

[0014] Wherein, during the coprecipitation reaction, the feeding rate of other solutions remains unchanged, and the feeding rate of the vanadium-containing mixed solution is gradually increased.

[0015] During the coprecipitation reaction described in the present application, the feeding rate of the vanadium-containing mixed solution may be increased once and then kept constant, or the feeding rate may be increased gradually.

[0016] In this application, vanadium is doped into the sodium cathode at the atomic level by a wet method, and V is directly doped in the co-precipitation stage. Compared with doping during the sintering process, this can not only simplify the preparation process of the cathode material, but also reduce the cost consumption in material preparation.

[0017] The present application presents a gradient doping of V element. Since the VO bond is more stable, it can effectively suppress the P2-O2 phase change during the charge and discharge process and maintain the P2 stacking structure of the triangular prism during the cycle, thereby greatly improving the structural stability of the positive electrode material and further improving the cycle performance.

[0018] In one embodiment, the vanadium source in step (1) includes vanadate and / or metavanadate.

[0019] In one embodiment, the concentration of vanadium in the vanadium-containing mixed solution is 0.2 to 2 mol / L, for example, 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0020] In one embodiment, the complexing agent solution in step (1) includes aqueous ammonia and / or oxalic acid solution.

[0021] In one embodiment, the concentration of the complexing agent solution is 4 to 12 mol / L, for example, 4 mol / L, 5 mol / L, 8 mol / L, 10 mol / L or 12 mol / L.

[0022] In one embodiment, the precipitant solution comprises sodium hydroxide solution.

[0023] In one embodiment, the concentration of the precipitant solution is 2 to 15 mol / L, for example, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L or 15 mol / L.

[0024] In one embodiment, the concentration of the nickel-copper-iron-manganese mixed salt solution is 0.5-5 mol / L, for example, 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L or 5 mol / L.

[0025] In one embodiment, the concentration of the complexing agent in the base solution is 0 to 2 mol / L, for example, 0 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0026] In one embodiment, the pH of the base solution is 9 to 13, for example, 9, 10, 11, 12 or 13.

[0027] In one embodiment, the feeding rate of the nickel-copper-iron-manganese mixed salt solution in step (1) is 4 to 100 L / h, for example: 4 L / h, 10 L / h, 20 L / h, 50 L / h or 100 L / h, etc.

[0028] In one embodiment, the feed rate of the vanadium-containing mixed solution is 0.5 to 20 L / h, for example, 0.5 L / h, 1 L / h, 5 L / h, 10 L / h or 20 L / h.

[0029] In one embodiment, the feed rate of the precipitant solution is 1 to 20 L / h, for example, 1 L / h, 5 L / h, 10 L / h, 15 L / h or 20 L / h.

[0030] In one embodiment, the feeding rate of the complexing agent solution is 0.5 to 10 L / h, for example, 0.5 L / h, 1 L / h, 4 L / h, 8 L / h or 10 L / h.

[0031] In one embodiment, the temperature of the coprecipitation reaction in step (1) is 40-80°C, for example, 40°C, 50°C, 60°C, 70°C or 80°C.

[0032] In one embodiment, the pH of the coprecipitation reaction is 9 to 13, for example, 9, 10, 11, 12 or 13.

[0033] In one embodiment, the end point of the coprecipitation reaction is that the particle size in the system is 3 to 8 μm, for example, 3 μm, 4 μm, 5 μm, 7 μm or 8 μm.

[0034] In one embodiment, during the coprecipitation reaction, the concentration of vanadium in the system increases at a rate of 0.002 to 0.5 mol / L·h, for example, 0.002 mol / L·h, 0.05 mol / L·h, 0.1 mol / L·h, 0.3 mol / L·h or 0.5 mol / L·h.

[0035] In one embodiment, the sodium source in step (2) comprises sodium carbonate.

[0036] In one embodiment, the sintering temperature is 700-1200°C, for example, 700°C, 800°C, 900°C, 1000°C or 1200°C.

[0037] In one embodiment, the sintering treatment time is 10 to 25 hours, for example, 10 hours, 12 hours, 15 hours, 20 hours or 25 hours.

[0038] In a second aspect, the present application provides a vanadium gradient-doped sodium cathode material, wherein the vanadium gradient-doped sodium cathode material is prepared by the method described in the first aspect.

[0039] In a third aspect, the present application provides a positive electrode plate, which comprises the vanadium gradient-doped sodium positive electrode material as described in the second aspect.

[0040] In a fourth aspect, the present application provides a sodium ion battery, which comprises the positive electrode sheet as described in the third aspect.

[0041] Compared with the prior art, this application has the following beneficial effects:

[0042] (1) The present application uses a wet method to dope vanadium into the sodium cathode at the atomic level, and directly dopes V element in the co-precipitation stage. Compared with doping in the sintering process, this can not only simplify the preparation process of the cathode material, but also reduce the cost consumption in material preparation.

[0043] (2) The present application adopts a gradient doping of V element. Since the VO bond is more stable, it can effectively suppress the P2-O2 phase change during the charge and discharge process and maintain the P2 stacking structure of the triangular prism during the cycle, thereby greatly improving the structural stability of the positive electrode material and further improving the cycle performance.

[0044] (3) The vanadium-doped sodium cathode material prepared by the method described in this application can achieve an initial discharge capacity of more than 124.5 mAh / g and a capacity retention rate of ≥80% for more than 2,500 cycles. This application uses a gradient doping method with the V element. The appropriate doping amount can maintain the original capacity while enhancing the cycle life of the material.

[0045] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0047] FIG1 is a SEM image of the sodium electrolyte precursor described in Example 1 of the present application. DETAILED DESCRIPTION

[0048] 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.

[0049] Example 1

[0050] This embodiment provides a vanadium gradient-doped sodium battery positive electrode material. The preparation method of the vanadium gradient-doped sodium battery positive electrode material is as follows:

[0051] (1) A mixed salt solution of nickel, copper, iron and manganese was mixed to obtain solution A (Ni:Cu:Fe:Mn=0.3:0.1:0.3:0.3, c=2 mol / L), and sodium vanadate was dissolved in ammonia water as a complex solution to obtain solution B (vanadium concentration was 1 mol / L). Solution A and solution B, sodium hydroxide solution (10 mol / L) and ammonia water (8 mol / L) were added to the bottom liquid in parallel. During the parallel addition, the feeding rate of solution A was 40 L / h, the concentration of vanadium element in the system was gradually increased at a rate of 0.02 mol / L·h, the feeding rate of sodium hydroxide solution was 15 L / h, and the feeding rate of ammonia water was 5 L / h. A coprecipitation reaction was carried out under a protective atmosphere at a reaction temperature of 60° C. and a pH value of 10 to 11. When the average particle size of the particles in the system reached 5.0 μm, the reaction was stopped, the mixture was aged for 8 h, washed by centrifugation, and dried at 100° C. to obtain a sodium electric precursor. The SEM image of the sodium electric precursor is shown in FIG1 . As can be seen from FIG1 , the precursor prepared in this embodiment has good sphericity, uniform size, and an average particle size of 5.0 μm.

[0052] (2) Sodium carbonate and precursor powder were weighed and mixed evenly according to a molar ratio of 1.03:1, and calcined at 900° C. for 18 h to obtain the vanadium gradient-doped sodium cathode material.

[0053] Example 2

[0054] This embodiment provides a vanadium gradient-doped sodium battery positive electrode material. The preparation method of the vanadium gradient-doped sodium battery positive electrode material is as follows:

[0055] (1) A mixed salt solution of nickel, copper, iron and manganese is mixed to obtain solution A (Ni:Cu:Fe:Mn=0.3:0.1:0.3:0.3, c=0.5 mol / L), and sodium vanadate is dissolved in a complex solution of ammonia to obtain solution B (vanadium concentration is 0.2 mol / L). Solution A and solution B, sodium hydroxide solution (2 mol / L) and oxalic acid (4 mol / L) are added to the bottom liquid in parallel. During the parallel addition process, the feed rate of solution A is 100 L / h, and the concentration of vanadium in the system is gradually increased at a rate of 0.5 mol / L·h. The feed rate of sodium hydroxide solution is 20 L / h, and the feed rate of oxalic acid is 10 L / h. A coprecipitation reaction is carried out under a protective atmosphere at a reaction temperature of 80°C and a pH value of 10.5-11.2. When the average particle size of the particles in the system reaches 5.0 μm, the reaction is stopped, the mixture is aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain a sodium electrode precursor.

[0056] (2) Sodium carbonate and precursor powder were weighed and mixed evenly in a molar ratio of 1.03:1, and calcined at 700° C. for 25 h to obtain the vanadium gradient-doped sodium cathode material.

[0057] Example 3

[0058] This embodiment provides a vanadium gradient-doped sodium battery positive electrode material. The preparation method of the vanadium gradient-doped sodium battery positive electrode material is as follows:

[0059] (1) A mixed salt solution of nickel, copper, iron and manganese is mixed to obtain solution A (Ni:Cu:Fe:Mn=0.3:0.1:0.3:0.3, c=5 mol / L), and sodium vanadate is dissolved in a complex solution of ammonia to obtain solution B (vanadium concentration is 2 mol / L). Solution A and solution B, sodium hydroxide solution (15 mol / L) and ammonia water (12 mol / L) are added to the bottom liquid in parallel. During the parallel addition process, the feed rate of solution A is 4 L / h, and the concentration of vanadium element in the system is gradually increased at a rate of 0.002 mol / L·h. The feed rate of sodium hydroxide solution is 1 L / h, and the feed rate of ammonia water is 0.5 L / h. A coprecipitation reaction is carried out under a protective atmosphere at a reaction temperature of 40°C and a pH value of 11 to 11.8. When the average particle size of the particles in the system reaches 5.0 μm, the reaction is stopped, aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain a sodium electrode precursor;

[0060] (2) Sodium carbonate and precursor powder were weighed and mixed evenly in a molar ratio of 1.03:1, and calcined at 12700° C. for 25 h to obtain the vanadium gradient-doped sodium cathode material.

[0061] Example 4

[0062] The only difference between this embodiment and embodiment 1 is that the concentration of vanadium in the vanadium-containing mixed solution is 0.1 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0063] Example 5

[0064] The only difference between this embodiment and embodiment 1 is that the concentration of vanadium in the vanadium-containing mixed solution is 3 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 6

[0066] The only difference between this embodiment and embodiment 1 is that the concentration of vanadium in the system is gradually increased at a rate of 0.001 mol / L·h. Other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Example 7

[0068] The only difference between this embodiment and embodiment 1 is that the concentration of vanadium in the system is gradually increased at a rate of 1 mol / L·h. Other conditions and parameters are exactly the same as those in embodiment 1.

[0069] Comparative Example 1

[0070] The only difference between this comparative example and Example 1 is that the vanadium source and the complexing agent are not mixed, but the vanadium source solution is fed alone. Other conditions and parameters are exactly the same as those in Example 1.

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 1 is that vanadium is not added, and other conditions and parameters are exactly the same as those in Example 1.

[0073] Comparative Example 3

[0074] The only difference between this comparative example and Example 1 is that the vanadium-containing mixed solution is not introduced first. After the particle size in the system reaches 4.5 μm, the vanadium-containing mixed solution is introduced until the particles reach 5 μm. Other conditions and parameters are exactly the same as those in Example 1.

[0075] Performance testing:

[0076] At 25°C, the vanadium gradient-doped sodium cathode materials prepared in the above examples and comparative examples were used as the main positive electrode materials, and the sodium metal sheet was used as the negative electrode to assemble into CR2032 button batteries. The electrochemical performance was then tested at 0.1C in the voltage range of 2.5-4.35V. The test results are shown in Table 1:

[0077] Table 1

[0078] As can be seen from Table 1, from Examples 1-3, the vanadium gradient-doped sodium positive electrode material prepared by the method described in the present application can produce a sodium ion battery with an initial discharge capacity of more than 124.5 mAh / g, and the number of cycles with a capacity retention rate of ≥80% can reach more than 2500 times.

[0079] By comparing Example 1 with Examples 4-5, it can be seen that during the preparation of the vanadium gradient-doped sodium cathode material described in this application, the concentration of vanadium in the vanadium-containing mixed solution affects its performance. When the vanadium concentration in the vanadium-containing mixed solution is controlled at 0.2 to 2 mol / L, the performance of the vanadium gradient-doped sodium cathode material is better. If the vanadium concentration is too low, it will not have a stabilizing effect, resulting in a cycle life that cannot reach the optimal level. If the vanadium concentration is too high, the amount of vanadium doped is too large, sacrificing capacity.

[0080] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the vanadium gradient-doped sodium positive electrode material described in the present application, the rate of increase of the concentration of the vanadium element in the system will affect the performance of the system. The rate of increase of the concentration of the vanadium element in the system is controlled at 0.002 to 0.5 mol / L·h, and the performance of the vanadium gradient-doped sodium positive electrode material is better. If the concentration of the vanadium element in the system increases too quickly, the overall amount of doping is large, sacrificing the capacity. If the concentration of the vanadium element in the system increases too slowly, the overall amount of doping is small, and the cycle life cannot be improved.

[0081] By comparing Example 1 with Comparative Examples 1-3, it can be seen that the present application presents a gradient doping of the V element. Since the VO bond is more stable, it can effectively suppress the P2-O2 phase change during the charge and discharge process and maintain the P2 stacking structure of the triangular prism during the cycle, thereby greatly improving the structural stability of the positive electrode material and further improving the cycle performance.

[0082] 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 method for preparing a vanadium gradient-doped sodium positive electrode material, The following steps are involved: (1) mixing a vanadium source and a complexing agent solution to obtain a vanadium-containing mixed solution, and injecting a nickel-copper-iron-manganese mixed salt solution, the vanadium-containing mixed solution, a precipitant solution and a complexing agent solution into the bottom liquid in parallel to perform a coprecipitation reaction to obtain a sodium electrode precursor; (2) mixing the sodium battery precursor with a sodium source, and subjecting the mixture to sintering treatment to obtain the vanadium gradient-doped sodium battery positive electrode material; Wherein, during the coprecipitation reaction, the feed rate of other solutions remains unchanged, and the feed rate of the vanadium-containing mixed solution gradually increases.

2. The preparation method according to claim 1, in, The vanadium source in step (1) comprises vanadate and / or metavanadate; Optionally, the concentration of vanadium in the vanadium-containing mixed solution is 0.2-2 mol / L.

3. The preparation method according to claim 1 or 2, in, The complexing agent solution in step (1) includes aqueous ammonia and / or oxalic acid solution; Optionally, the concentration of the complexing agent solution is 4 to 12 mol / L; Optionally, the precipitant solution comprises a sodium hydroxide solution; Optionally, the concentration of the precipitant solution is 2 to 15 mol / L; Optionally, the concentration of the nickel-copper-iron-manganese mixed salt solution is 0.5 to 5 mol / L; Optionally, the concentration of the complexing agent in the base solution is 0 to 2 mol / L; Optionally, the pH of the base solution is 9-13.

4. The preparation method according to any one of claims 1 to 3, in, The feeding rate of the nickel-copper-iron-manganese mixed salt solution in step (1) is 4 to 100 L / h; Optionally, the feed rate of the vanadium-containing mixed solution is 0.5 to 20 L / h; Optionally, the feed rate of the precipitant solution is 1 to 20 L / h; Optionally, the feeding rate of the complexing agent solution is 0.5 to 10 L / h.

5. The preparation method according to any one of claims 1 to 4, in, The temperature of the coprecipitation reaction in step (1) is 40-80° C. Optionally, the pH of the coprecipitation reaction is 9 to 13; Optionally, the end point of the coprecipitation reaction is that the particle size in the system is 3 to 8 μm.

6. The preparation method according to any one of claims 1 to 5, in, During the coprecipitation reaction, the concentration of vanadium in the system increases at a rate of 0.002 to 0.5 mol / L·h.

7. The preparation method according to any one of claims 1 to 6, in, The sodium source in step (2) comprises sodium carbonate; Optionally, the sintering temperature is 700-1200°C; Optionally, the sintering treatment time is 10 to 25 hours.

8. A vanadium gradient-doped sodium positive electrode material prepared by the method according to any one of claims 1 to 7.

9. A positive electrode sheet comprising the vanadium gradient-doped sodium positive electrode material as claimed in claim 8.

10. A sodium ion battery comprising the positive electrode sheet according to claim 9.

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