Core-shell sodium battery positive electrode material, preparation method therefor, and use thereof

Abstract

A core-shell sodium battery positive electrode material, a preparation method therefor, and the use thereof. The preparation method comprises the following steps: (1) concurrent flow addition of a mixed solution A, an additive solution, a precipitant solution, and a complexing agent solution into a base solution, and carrying out a one-step coprecipitation reaction; (2) switching the mixed solution A with a mixed solution B, and continuing to carry out a two-step coprecipitation reaction to obtain a core-shell sodium battery precursor; and (3) mixing the core-shell sodium battery precursor with a sodium source and carrying out sintering treatment to obtain the core-shell sodium battery positive electrode material; the mixed solution A comprises a main metal element, and the mixed solution B comprises a main metal element and an auxiliary metal element. Elemental components in the inner core and the outer shell are controlled via multi-step coprecipitation, the prepared core-shell structure material possesses high energy density, high safety and stability, etc., and the problems of quaternary or quinary phase separation, primary particles having no crystal form, and low tap density are solved.

Description

A core-shell 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 core-shell sodium battery positive electrode material and a preparation method and application thereof. Background Art

[0002] The new energy vehicle industry has experienced rapid growth in recent years. Its power battery materials are primarily lithium-ion batteries, encompassing two technology lines: lithium iron phosphate (LiFePO4) and ternary power batteries. The former offers excellent safety and low cost, while the latter offers high energy density and extended range, making it suitable for high-end vehicles. However, limited lithium reserves and high prices have led to a gradual increase in the cost of power batteries. Compared to lithium-ion batteries, sodium-ion batteries (Na-ion) offer advantages such as low cost, low-temperature resistance, safety, and abundant and readily available Na resources, making them a viable alternative in the new energy industry.

[0003] In the field of sodium-ion batteries, layered oxides have attracted much attention due to their high energy density and low production cost. There are two sintering routes for sodium-ion battery layered oxides: direct solid-phase sintering of the oxides and two-step sintering of layered precursors. When the layered precursor is mixed with a sodium source for sintering, the elements in the precursor are more evenly distributed and have better consistency. Therefore, the elements after sintering will also be more uniform, which has great advantages for the material's cycle stability and capacity.

[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] CN116230887A discloses a method for preparing a sodium-ion battery precursor material and cathode material with a Cu concentration gradient. Specifically, the method involves adjusting the pH through a coprecipitation method to obtain a core-shell precursor material containing no Cu core and a Cu shell. This is followed by a sintering process to allow the Cu element to diffuse at high temperature, resulting in a sodium-ion battery cathode material with a Cu concentration gradient from the outer layer to the center.

[0006] The sodium cathode material prepared by the above scheme will cause copper precipitation due to the uneven morphology of the precursor, and the tap density is too low.

[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 core-shell sodium battery positive electrode material and its preparation method and application. The present application controls the elemental composition of the inner core and the outer shell through step-by-step co-precipitation to obtain a core-shell structure material that can take into account the advantages of high energy density and high safety and stability, and can solve the problems faced by sodium quaternary or quinary batteries such as phase separation, amorphous primary particles and low tap density.

[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 core-shell sodium cathode material, the preparation method comprising the following steps:

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

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

[0014] (3) mixing the core-shell sodium battery precursor with a sodium source, and sintering the mixture to obtain the core-shell sodium battery positive electrode material;

[0015] The mixed solution A contains a main metal element, and the mixed solution B contains a main metal element and a subsidiary metal element.

[0016] The present invention prepares a core-shell structured sodium cathode material by controlling the elemental composition of the inner core and the outer shell through step-by-step co-precipitation. The core-shell structured sodium cathode material has the same morphology as the core-shell sodium cathode precursor, with prominent crystal form, uniform particle size, no phase separation, good dispersibility, and a tap density of up to 1.0 g / cm 3 above.

[0017] In one embodiment, the main metal element includes any one of Ni, Fe, or Mn, or a combination of at least two of them.

[0018] In one embodiment, the accessory metal element includes any one or a combination of at least two of Cu, Zn, Ti, Mg, Ca, Al, Ag, Co, Cr, La or Ce.

[0019] In one embodiment, the types of main metal elements in the mixed solution A and the mixed solution B may be the same or different, depending on the needs.

[0020] In one embodiment, the total concentration of metal ions in the mixed solution A is 1 to 5 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0021] In one embodiment, the total concentration of metal ions in the mixed solution B is 1 to 5 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0022] In one embodiment, the solute of the additive solution in step (1) includes ammonium sulfate and / or sulfuric acid.

[0023] In one embodiment, the concentration of the additive solution is 0.1 to 2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0024] In one embodiment, the precipitant solution comprises an alkali solution.

[0025] 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.

[0026] In one embodiment, the complexing agent solution includes any one of ammonia water, oxalic acid solution, ammonium sulfate solution, EDTA, citric acid solution or sodium acetate solution, or a combination of at least two thereof.

[0027] 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.

[0028] In one embodiment, the base solution includes alkali solution, a complexing agent and additives.

[0029] In one embodiment, the flow rate of the mixed solution A in step (1) is 20 to 80 kg / h, for example, 20 kg / h, 30 kg / h, 50 kg / h, 60 kg / h or 80 kg / h.

[0030] In one embodiment, the flow rate of the additive solution is 1 to 5 kg / h, for example, 1 kg / h, 2 kg / h, 3 kg / h, 4 kg / h or 5 kg / h.

[0031] In one embodiment, the flow rate of the precipitant solution is 5 to 20 kg / h, for example, 5 kg / h, 10 kg / h, 12 kg / h, 15 kg / h or 20 kg / h.

[0032] In one embodiment, the flow rate of the complexing agent solution is 1 to 8 kg / h, for example, 1 kg / h, 2 kg / h, 4 kg / h, 6 kg / h or 8 kg / h.

[0033] In one embodiment, the temperature of the one-step coprecipitation reaction in step (1) is 35-70°C, for example, 35°C, 40°C, 50°C, 60°C or 70°C.

[0034] In one embodiment, the pH of the one-step coprecipitation reaction is 9 to 12, for example, 9, 9.5, 10, 11 or 12.

[0035] In one embodiment, the stirring speed of the one-step coprecipitation reaction is 200-500 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 400 rpm or 500 rpm.

[0036] In one embodiment, the endpoint of the one-step coprecipitation reaction is that the particle size D501 in the system is 2 to 12 μm, for example, 2 μm, 3 μm, 4 μm, 6 μm, 8 μm or 12 μm.

[0037] In one embodiment, the pH of the two-step co-precipitation reaction in step (2) is less than the pH of the one-step co-precipitation reaction.

[0038] In one embodiment, the pH of the two-step co-precipitation reaction is 8-11, for example, 8, 8.5, 9, 10 or 11.

[0039] In one embodiment, the stirring speed of the two-step co-precipitation reaction is 250-450 rpm, for example, 250 rpm, 300 rpm, 350 rpm, 400 rpm or 450 rpm.

[0040] In one embodiment, the endpoint of the two-step coprecipitation reaction is that the particle size D502 in the system is 2.5 to 14 μm, for example, 2.5 μm, 3 μm, 5 μm, 8 μm or 14 μm.

[0041] In one embodiment, D502-D501=0.5-2 μm, for example, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm or 2 μm.

[0042] In one embodiment, the temperature of the sintering treatment in step (3) is 500-1000°C, for example, 500°C, 600°C, 800°C, 900°C or 1000°C.

[0043] In one embodiment, the sintering treatment time is 6 to 20 hours, for example, 6 hours, 8 hours, 10 hours, 15 hours or 20 hours.

[0044] In a second aspect, the present application provides a core-shell sodium cathode material, which is prepared by the method described in the first aspect.

[0045] The present invention designs a core-shell structure with nickel iron manganese hydroxide as the core and a shell containing doped metal elements, so that the tap density of the synthesized sodium electrolyte precursor material can reach 1.0g / cm 3 The morphology shown above is uniform primary particles with no phase separation. By designing a core-shell structure, the current problems in the industry with uneven morphology (Cu precipitation) and low tap density of quaternary sodium electrolyte precursors are solved.

[0046] In a third aspect, the present application provides a positive electrode plate, which comprises the core-shell sodium battery positive electrode material as described in the second aspect.

[0047] In a fourth aspect, the present application provides a sodium ion battery, which comprises the positive electrode sheet as described in the third aspect.

[0048] Compared with the prior art, this application has the following beneficial effects:

[0049] (1) This application controls the elemental composition of the inner core and the outer shell through step-by-step co-precipitation to obtain a core-shell structure material that can take into account the advantages of high energy density and high safety and stability, and can solve the problems faced by sodium quaternary or quinary materials such as phase separation, amorphous primary particles and low tap density.

[0050] (2) By adding additives during the reaction process, the present application can achieve uniform co-precipitation of elements such as Cu and Zn in the outer shell, and the prepared precursor does not undergo phase separation, thereby solving the problem of too low tap density of quaternary or quinary precursors.

[0051] (3) The tap density of the positive electrode precursor prepared by the method described in this application can reach 1.26 g / cm 3 As shown above, the capacity retention rate after 50 cycles at 1C can reach more than 92.19%, and it can be adapted to sodium battery positive electrode materials in various proportions.

[0052] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0053] 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.

[0054] Example 1

[0055] This embodiment provides a core-shell sodium cathode material, and the preparation method of the core-shell sodium cathode material is as follows:

[0056] (1) Nickel sulfate and manganese sulfate salt are prepared in a ratio of 1:1 to prepare nickel manganese sulfate solution A with a total metal ion concentration of 1 mol / L, an ammonia complexing agent solution with a concentration of 1 mol / L, and a NaOH solution with a concentration of 2 mol / L. A certain amount of pure water, ammonia complexing agent, alkaline solution and ammonium sulfate solution are added to the reactor as a bottom liquid to maintain the stability of the system. Solution A, ammonia complexing agent, NaOH precipitant and ammonium sulfate solution are added to the reactor in parallel, and the reaction is carried out at 35°C, maintaining the reaction pH at 11.0-11.8, the ammonia concentration at 7 g / L, and the stirring speed at 450 rpm. Nickel manganese core particles with a particle size of 2.5 μm are obtained. The flow rate of the solution A is 20 kg / h, the flow rate of the alkaline solution is 6 kg / h, the flow rate of the ammonia water is 2 kg / h, and the flow rate of the ammonium sulfate solution is 1 kg / h;

[0057] (2) A mixed solution B of nickel sulfate, copper sulfate and ferrous sulfate with a concentration of 2 mol / L was prepared in a ratio of 1:1:1, solution A was switched to mixed solution B, the reaction pH was maintained at 10-11, the ammonia concentration was 6 g / L, the stirring speed was 350 rpm, and the reaction was terminated when the particle size reached 3.0 μm to obtain the core-shell sodium electrode precursor Ni 0.4 Cu 0.1 Fe 0.1 Mn 0.4 (OH)2;

[0058] (3) The core-shell sodium battery precursor and sodium carbonate were mixed and ground in a mortar, and the ground mixture was calcined at 600°C for 15h with a heating rate of 1°C / min to obtain a core-shell structured sodium battery positive electrode material.

[0059] Example 2

[0060] This embodiment provides a core-shell sodium cathode material, and the preparation method of the core-shell sodium cathode material is as follows:

[0061] (1) Nickel sulfate, manganese sulfate and ferrous sulfate are prepared in a ratio of 2:4:4 to prepare nickel-iron-manganese sulfate solution A with a total metal ion concentration of 2 mol / L, an oxalic acid complexing agent solution with a concentration of 2 mol / L, and a NaOH solution with a concentration of 3 mol / L. A certain amount of pure water, ammonia complexing agent, alkaline solution and ammonium sulfate solution are added to the reactor as a bottom liquid to maintain the stability of the system. Solution A, oxalic acid complexing agent, NaOH precipitant and ammonium sulfate solution are added to the reactor in parallel, and the reaction is carried out at 50°C, maintaining the reaction pH at 10.5-11.5, the ammonia concentration at 4 g / L, and the stirring speed at 350 rpm. Nickel-manganese core particles with a particle size of 4.5 μm are obtained. The flow rate of the solution A is 80 kg / h, the flow rate of the alkaline solution is 20 kg / h, the flow rate of the ammonia water is 8 kg / h, and the flow rate of the ammonium sulfate solution is 5 kg / h;

[0062] (2) Prepare a mixed solution B of nickel sulfate and copper sulfate with a concentration of 2 mol / L in a ratio of 1:1, switch solution A to mixed solution B, maintain the reaction pH at 9-10.5, the oxalic acid concentration at 3 g / L, the stirring speed at 300 rpm, and terminate the reaction when the particle size reaches 5.0 μm to obtain the core-shell sodium electrode precursor Ni 0.3 Cu 0.1 Fe 0.3 Mn 0.3 (OH)2;

[0063] (3) The core-shell sodium battery precursor and sodium carbonate were mixed and ground in a mortar, and the ground mixture was calcined at 500°C for 20 h with a heating rate of 1.5°C / min to obtain a core-shell structured sodium battery positive electrode material.

[0064] Example 3

[0065] This embodiment provides a core-shell sodium cathode material, and the preparation method of the core-shell sodium cathode material is as follows:

[0066] (1) Nickel sulfate, manganese sulfate and ferrous sulfate are prepared in a ratio of 2:4:4 to prepare nickel-iron-manganese sulfate solution A with a total metal ion concentration of 5 mol / L, an ammonia complexing agent solution with a concentration of 3 mol / L, and a NaOH solution with a concentration of 4 mol / L. A certain amount of pure water, ammonia complexing agent, alkaline solution and ammonium sulfate solution are added to the reactor as a bottom liquid to maintain the stability of the system. Solution A, ammonia complexing agent, NaOH precipitant and ammonium sulfate solution are added to the reactor in parallel, and the reaction is carried out at 70°C, the pH of the reaction is maintained at 11.5-12, the ammonia concentration is 7 g / L, and the stirring speed is 500 rpm. Nickel-manganese core particles with a particle size of 12 μm are obtained. The flow rate of the solution A is 20 kg / h, the flow rate of the alkaline solution is 5 kg / h, the flow rate of the ammonia water is 1 kg / h, and the flow rate of the ammonium sulfate solution is 1 kg / h;

[0067] (2) A mixed solution B of nickel sulfate, copper sulfate, zinc sulfate and ferrous sulfate with a concentration of 2 mol / L was prepared in a ratio of 1:1:1:1, solution A was switched to mixed solution B, the reaction pH was maintained at 10.5-11, the ammonia concentration was 6 g / L, the stirring speed was 450 rpm, and the reaction was terminated when the particle size reached 14 μm to obtain the core-shell sodium electrode precursor Ni 0.21 Fe 0.41 Cn 0.03 Zn 0.03 Mn 0.32 (OH)2;

[0068] (3) The core-shell sodium battery precursor and sodium carbonate were mixed and ground in a mortar, and the ground mixture was calcined at 1000°C for 6 hours at a heating rate of 2°C / min to obtain a core-shell structured sodium battery positive electrode material.

[0069] Comparative Example 1

[0070] The only difference between this comparative example and Example 1 is that nickel, manganese, copper and iron are mixed to form a salt solution, and the precursor is prepared by a one-step co-precipitation. 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 no additive solution (ammonium sulfate solution) is added, and the precursor is prepared by one-step coprecipitation. 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 nickel and iron (main metals) are not added to the mixed solution B, and the other conditions and parameters are exactly the same as those in Example 1.

[0075] Performance testing:

[0076] The positive electrode materials in the examples and comparative examples were prepared into button-type batteries, and button-type batteries were tested. The test results are shown in Table 1:

[0077] Table 1

[0078] As can be seen from Table 1, from Examples 1-3, the tap density of the cathode precursor prepared by the method described in this application can reach 1.26 g / cm 3 As shown above, the capacity retention rate after 50 cycles at 1C can reach more than 92.19%, and it can be adapted to various proportions of sodium cathode materials. The core-shell sodium battery material of Example 1 exhibits high specific capacity and cycle stability after being prepared into a battery. Examples 2 and 3 also exhibit relatively high cycle stability. The main metal content in Comparative Example 1 is no different from that in Example 1, but it does not belong to the core-shell structure. After being prepared into a battery, the capacity is no different from that of Example 1, but the cycle stability is significantly reduced. The capacity and cycle stability of Comparative Examples 2 and 3 are also poor.

[0079] By comparison of Example 1 and Comparative Example 1, it can be seen that the present application controls the elemental composition of the inner core and the outer shell through step-by-step co-precipitation to prepare a core-shell structured sodium battery positive electrode material. The core-shell structured sodium battery positive electrode material is consistent with the morphology of the core-shell sodium battery precursor, which solves the current problems of uneven morphology (Cu precipitation) and low tap density of the quaternary sodium battery precursor in the industry, and improves the cyclic stability of the material.

[0080] By comparing Example 1 and Comparative Example 2, it can be seen that the present application can achieve uniform co-precipitation of elements such as Cu and Zn in the outer shell by adding additives during the reaction process, and the prepared precursor does not show phase separation, thereby solving the problem of too low tap density of quaternary or quinary precursors.

[0081] By comparing Example 1 and Comparative Example 3, it can be seen that the present application reduces the individual precipitation of Cu in the shell during the reaction process by adding Ni and Fe elements to the shell, thereby ensuring the uniformity of Cu doping in the shell, thereby improving the cycle stability of the battery.

[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 core-shell sodium cathode material, The following steps are involved: (1) injecting the mixed solution A, the additive solution, the precipitant solution and the complexing agent solution into the base solution in parallel to perform a one-step coprecipitation reaction; (2) switching the mixed solution A to the mixed solution B, and continuing the two-step coprecipitation reaction to obtain a core-shell sodium electrode precursor; (3) mixing the core-shell sodium battery precursor with a sodium source, and subjecting the mixture to sintering treatment to obtain the core-shell sodium battery positive electrode material; The mixed solution A contains a main metal element, and the mixed solution B contains a main metal element and a sub-metal element.

2. The preparation method according to claim 1, in, The main metal element includes any one of Ni, Fe or Mn or a combination of at least two; Optionally, the accessory metal element includes any one or a combination of at least two of Cu, Zn, Ti, Mg, Ca, Al, Ag, Co, Cr, La or Ce; Optionally, the total concentration of metal ions in the mixed solution A is 1 to 5 mol / L; Optionally, the total concentration of metal ions in the mixed solution B is 1 to 5 mol / L.

3. The preparation method according to claim 1 or 2, in, The solute of the additive solution in step (1) includes ammonium sulfate and / or sulfuric acid; Optionally, the concentration of the additive solution is 0.1 to 2 mol / L; Optionally, the precipitant solution comprises an alkali solution; Optionally, the concentration of the precipitant solution is 1 to 4 mol / L; Optionally, the complexing agent solution includes any one or a combination of at least two of ammonia water, oxalic acid solution, ammonium sulfate solution, EDTA, citric acid solution or sodium acetate solution; Optionally, the concentration of the complexing agent solution is 1 to 3 mol / L; Optionally, the base liquid includes alkali solution, a complexing agent and additives.

4. The preparation method according to any one of claims 1 to 3, in, The flow rate of the mixed solution A in step (1) is 20-80 kg / L; Optionally, the flow rate of the additive solution is 1 to 5 kg / h; Optionally, the flow rate of the precipitant solution is 5 to 20 kg / h; Optionally, the flow rate of the complexing agent solution is 1 to 8 kg / h.

5. The preparation method according to any one of claims 1 to 3, in, The temperature of the one-step coprecipitation reaction in step (1) is 35-70° C.; Optionally, the pH of the one-step coprecipitation reaction is 9 to 12; Optionally, the stirring speed of the one-step coprecipitation reaction is 200 to 500 rpm; Optionally, the endpoint of the one-step coprecipitation reaction is the particle size D50 in the system. 1 2~12μm.

6. The preparation method according to any one of claims 1 to 5, in, The pH of the two-step coprecipitation reaction in step (2) is less than the pH of the one-step coprecipitation reaction; Optionally, the pH of the two-step coprecipitation reaction is 8 to 11; Optionally, the stirring speed of the two-step coprecipitation reaction is 250-450 rpm; Optionally, the endpoint of the two-step coprecipitation reaction is the particle size D50 in the system. 2 2.5~14μm; Optionally, the D50 2 -D50 1 =0.5~2μm.

7. The preparation method according to any one of claims 1 to 6, in, The sintering temperature in step (3) is 500-1000° C. Optionally, the sintering treatment time is 6 to 20 hours.

8. A core-shell sodium cathode material prepared by the method according to any one of claims 1 to 7.

9. A positive electrode sheet comprising the core-shell 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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