Cobalt-free doped layered oxide composite material and preparation method and application thereof

Abstract

The application discloses a cobalt-doped layered oxide composite material and a preparation method and application thereof, and has a general formula of Na m [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn n I; in formula I, 0.50<=m<=0.70, 0.78<=n<=1.00. The transition metal cations with redox reactivity such as Ni 2+ , Fe 3+ , Cu 2+ and the non-redox active transition metal cations such as Al 3+ , Mn 4+ , Zn 2+ are simultaneously introduced, so that the P2-type layered transition metal oxide balances the reversible capacity and structural stability of the material. The layered structure disclosed by the application is beneficial to the reversible insertion and extraction of Na + , accelerates ion migration, reduces charge transfer resistance and enhances structural stability.

Description

Technical Field

[0001] This application relates to a cobalt-free layered oxide composite material, its preparation method, and its application, belonging to the fields of nanomaterials and sodium-ion battery technology. Background Technology

[0002] Lithium-ion batteries (LIBs) are ubiquitous in modern society, permeating our daily lives through portable electronic devices and electric vehicles. However, the scarcity of lithium resources and their concentration in geopolitically sensitive regions have prompted researchers to explore alternative electrochemical energy storage systems. Sodium-ion batteries (NIBs) have attracted significant interest as a low-cost alternative to lithium-ion systems in large-scale energy storage applications due to the abundance of naturally occurring sodium resources and the similar chemical properties of sodium and lithium. A primary challenge in advancing NIBs lies in developing high-performance and low-cost electrode materials.

[0003] The cathode material in sodium-ion batteries (NIBs) is a crucial factor determining battery capacity, electrochemical performance, and production cost. Various cathode materials have been explored, including layered transition metal oxides (LTMOs), Prussian blue analogs, and polyanionic compounds. Layered oxides (NaxMO2) are classified into O-type and P-type, with the P2 and O3 phases showing promise as cathode materials for NIBs by promoting rapid sodium ion insertion / extraction during charge and discharge. Among existing cathode materials, P2-type layered oxides, particularly manganese-rich sodium oxides (NaxMnO2), are considered one of the most attractive cathode candidates due to their high specific capacity and natural Mn abundance. However, layered oxide materials suffer from complex phase transitions and structural instability, limiting their overall applicability.

[0004] Over the past few decades, extensive research has been conducted to stabilize the anion redox process in manganese-based P2-type layered cathodes, discovering that a stable crystal structure can prevent the "collapse" of the lattice and ion diffusion channels. Recently, high-entropy oxides (HEOs) have exhibited significantly improved structural stability during charge and discharge processes. They can help stabilize the crystal structure of materials by maximizing the configurational entropy, thereby improving their cycle stability. The high-entropy (HE) method relies on "mixing" five or more metal elements to form a crystalline solid solution. Higher entropy increases the solid solubility of different metals in the structure, which is conducive to the formation of single phases. This provides a new approach for the modification of P2-type layered transition metal oxides.

[0005] Currently, the high-entropy strategy is widely used in the modification of O3-type layered transition metal oxides, and most high-entropy layered NIB cathode materials contain cobalt (Co). However, the highly volatile price of cobalt and the geopolitical restrictions on cobalt mining make the elimination of cobalt an urgent need for the new energy industry. Due to their advantages of high energy density and low cost, low-nickel (Ni) and Co-free layered oxide cathodes have become the most promising cathode materials for next-generation NIBs. Modifying cathode materials using the HE strategy is a complex task because it involves the influence of each element on the material's capacity and structural stability. Summary of the Invention

[0006] This invention introduces Ni 2+ Fe 3+ Cu 2+ Cations with redox reactivity provide charge compensation, reducing the adverse effects of capacity decay caused by the reduction of Mn; the introduction of Al 3+ Mn 4+ Zn 2+ Non-redox reactive cations inhibit phase transitions in materials, stabilizing their structure. There are few reports and related patents on cobalt-free, low-nickel, high-entropy-doped layered oxide sodium electrode materials, indicating significant potential for research and development in this field.

[0007] The purpose of this invention is to address the shortcomings of current technologies by providing a method for preparing a cobalt-free, low-nickel, high-entropy layered oxide sodium cathode material.

[0008] According to one aspect of this application, a cobalt-free layered oxide composite material is provided, the general formula of which is:

[0009] Na m [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn n O2 type I;

[0010] In Equation I, 0.50≤m≤0.70, 0.78≤n≤1.00.

[0011] Optionally, the layered oxide composite material is of type P2.

[0012] Optionally, the microstructure of the layered oxide composite material is microspheres with a particle size of 3–9 μm.

[0013] According to another aspect of this application, a method for preparing the above-described layered oxide composite material is provided, the method comprising the following steps:

[0014] (1) A mixture containing sodium source, aluminum source, nickel source, iron source, copper source, zinc source, manganese source and solvent is evaporated, dried and calcined to obtain the precursor of the layered oxide composite material;

[0015] (2) The precursor of the layered oxide composite material is ball-milled and spray-dried to obtain the layered oxide composite material.

[0016] Optionally, the sodium source is selected from at least one of sodium nitrate, sodium sulfate, sodium carbonate, and sodium oxide.

[0017] Optionally, the aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, aluminum carbonate, and aluminum oxide.

[0018] Optionally, the nickel source is selected from at least one of nickel nitrate, nickel sulfate, nickel carbonate, and nickel oxide.

[0019] Optionally, the iron source is selected from at least one of ferric nitrate, ferric sulfate, ferric acetate, and ferric oxide.

[0020] Optionally, the copper source is selected from at least one of copper nitrate, copper sulfate, copper carbonate, and copper oxide.

[0021] Optionally, the zinc source is selected from at least one of zinc nitrate, zinc sulfate, zinc acetate, and zinc oxide.

[0022] Optionally, the manganese source is selected from at least one of manganese acetate, manganese sulfate, manganese carbonate, and manganese oxide (II).

[0023] Optionally, the molar ratio of the sodium source, aluminum source, nickel source, iron source, copper source, zinc source, and manganese source is (30-60):1:1:1:1:1:(35-85).

[0024] Optionally, the solvent is selected from at least one of water and ethanol.

[0025] Optionally, the molar volume ratio of the sodium source to the solvent is 1.40 to 1.45 mol / L.

[0026] Optionally, in step (1), the temperature at which the solvent is evaporated is 70–80°C.

[0027] Optionally, in step (1), the temperature at which the solvent is evaporated is independently selected from any value of 70°C, 72°C, 74°C, 75°C, 78°C, 80°C, or a range between any two of the above.

[0028] Optionally, the drying temperature is 70–90°C, and the drying time is 10–24 hours.

[0029] Optionally, the drying temperature is independently selected from any value of 70°C, 75°C, 80°C, 85°C, 90°C, or a range between any two of the above.

[0030] Optionally, the drying time is independently selected from any value of 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h or a range between any two of the above.

[0031] Optionally, the calcination temperature is 750–1150°C, and the calcination time is 10–14 hours.

[0032] Optionally, the calcination temperature is independently selected from any value of 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or a range between any two of the above.

[0033] Optionally, the calcination time is independently selected from any value of 10h, 11h, 12h, 13h, 14h or a range between any two of the above.

[0034] Optionally, in step (2), the spray drying temperature is 160-200°C and the spray drying time is 3.0-6.5h.

[0035] Optionally, in step (2), the spray drying temperature is independently selected from any value of 160°C, 170°C, 180°C, 190°C, 200°C or a range between any two of the above.

[0036] Optionally, in step (2), the spray drying time is independently selected from any value of 3.0h, 4.0h, 5.0h, 6.0h, 6.5h or a range between any two of the above.

[0037] According to another aspect of this application, an application of the above-described layered oxide composite material in a sodium-ion battery is provided, the sodium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator; the positive electrode is a layered oxide composite material; the negative electrode is a sodium sheet; the electrolyte is sodium hexafluorophosphate; and the separator is glass fiber.

[0038] Optionally, the sodium-ion battery has an initial reversible capacity of 120–140 mAh g at a 0.5C rate. -1 .

[0039] As an optional implementation, this application is achieved through the following technical solution:

[0040] The method for preparing a self-supporting layered transition metal oxide sodium-ion battery cathode material includes the following steps:

[0041] The first step is to synthesize NM-HEO.

[0042] Weigh out NaNO3, Al(NO3)3·9H2O, Ni(NO3)2, Fe(NO3)3·9H2O, Cu(NO3)3·3H2O, Zn(NO3)2, and Mn(CH3COO)2 according to a molar ratio of 30–60:1:1:1:1:1:35–85. Weigh out 700–820 mL of deionized water as solvent, then evaporate the solvent to dryness in a water bath at 70–80 °C, and finally vacuum dry in a vacuum drying oven at 70–90 °C for 10–24 h. Then calcine in a muffle furnace at 750 °C–1150 °C for 10–14 h to obtain NM-HEO.

[0043] The second step is to prepare NM-HEO with microsphere morphology.

[0044] The calcined material is ball-milled, and after ball milling, it is prepared into a uniform dispersion. It is then dried at a spray temperature of 160-200℃, and the dried powder is collected to obtain NM-HEO with microsphere morphology.

[0045] This application discloses a method for preparing a cobalt-free, low-nickel, high-entropy-doped layered oxide sodium cathode material. Based on this method, P2-type Na... 0.67 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 8 / 9 O2 (NM-HEO) is a positive electrode material for sodium-ion batteries. The invented Na... 0.67 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 8 / 9 O2 cathode material is a type of material that employs a high-entropy strategy and simultaneously introduces Ni. 2+ Fe 3+ Cu 2+ Transition metal cations with redox reactivity and Al 3+ Mn 4+ Zn 2+ P2-type layered transition metal oxides, containing non-redox reactive transition metal cations, balance the reversible capacity and structural stability of the material. The layered structure is beneficial for Na... + It allows for reversible insertion and extraction, accelerating ion migration, reducing charge transfer resistance, and enhancing structural stability.

[0046] The beneficial effects that this application can produce include:

[0047] 1) Compared with previous NM materials, the NM-HEO cathode material provided in this application uses the sol-gel method, resulting in more uniform element doping; ball milling and spray drying methods are used to obtain spherical layered transition metal oxides, which broadens the development of LTMO in the field of NIBs cathode materials.

[0048] 2) The NM-HEO prepared by this invention, as provided in this application, has a microstructure of nanosheets self-assembling into microspheres, and Na... + It exhibits high content, high energy density, and high compaction density. Its preparation method employs a rationally designed two-step strategy: first, NM-HEO is synthesized via a sol-gel method; then, ball milling and spray drying are used to obtain NM-HEO layered NIBs cathode materials with a nanosheet self-assembly into microsphere morphology. The high-entropy strategy can suppress phase transitions and stabilize the crystal structure through entropy stabilization; the microsphere morphology can improve the compaction density of the material. Attached Figure Description

[0049] Figure 1 The image shows the scanning electron microscope (SEM) morphology of the NM-HEO cathode material prepared in Example 1 of this application. The scale bar is 5 μm.

[0050] Figure 2 This is an energy dispersive spectroscopy (EDS) elemental analysis diagram of the NM-HEO cathode material prepared in Example 1 of this application.

[0051] Figure 3 The graph shows the cycle performance test results of a coin cell assembled with NM-HEO cathode material prepared in Example 1 of this application as the cathode and metallic sodium as the anode.

[0052] Figure 4 Na obtained in Example 2 of this application 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 Cyclic performance test diagram of a coin cell assembled with O2 as the positive electrode and metallic sodium as the negative electrode. Detailed Implementation

[0053] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0054] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0055] This application employs a Zeiss high-resolution scanning electron microscope for microstructure characterization. Microscopic images with a scale bar of 5 μm were captured at an electron beam acceleration voltage of 2.0 kV and a magnification of 2.0 kX. This application also utilizes a Newway 8-channel testing system for coin cell electrochemical performance testing at 0.5C (1C = 240 mAh g⁻¹). -1 Cycle 100 times at a multiplier.

[0056] Example 1

[0057] The first step is to synthesize NM-HEO(Na) 0.67 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 8 / 9 O2)

[0058] Weigh out NaNO3, Al(NO3)3·9H2O, Ni(NO3)2, Fe(NO3)3·9H2O, Cu(NO3)3·3H2O, Zn(NO3)2, and Mn(CH3COO)2 according to a molar ratio of 30.5:1:1:1:1:1:40. Weigh out 84.99 g of NaNO3, 15.50 g of Al(NO3)3·9H2O, 9.69 g of Ni(NO3)2, 13.46 g of Fe(NO3)3·9H2O, 8.05 g of Cu(NO3)3·3H2O, 9.92 g of Zn(NO3)2, and 326.78 g of Mn(CH3COO)2. Weigh out 700 mL of deionized water as the solvent, then evaporate the solvent to dryness in a water bath at 80°C, and finally vacuum dry in a vacuum drying oven at 80°C for 12 hours. Then it is fed into a muffle furnace and calcined at 750°C for 12 hours to obtain NM-HEO.

[0059] The second step is to prepare Na with microsphere morphology. 0.67 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 8 / 9 O2

[0060] The calcined material is ball-milled, and after ball milling, it is prepared into a uniform dispersion. It is then dried at a spray temperature of 160°C, and the dried powder is collected to obtain NM-HEO with microsphere morphology.

[0061] The cobalt-free, low-nickel, high-entropy-doped layered oxide sodium cathode material NM-HEO prepared in Example 1 was analyzed by scanning electron microscopy. Figure 1As can be seen, the obtained NM-HEO cathode material exhibits a microscopic morphology of nanosheets assembled into microspheres, with an average diameter of 8 μm. Elemental analysis was performed on the NM-HEO material prepared in this embodiment.

[0062] The NM-HEO microspheres prepared in Example 1 were subjected to elemental analysis using energy dispersive spectroscopy. Figure 2 It can be seen that the various metallic elements are evenly distributed.

[0063] Example 2

[0064] The first step is to synthesize Na. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 O2

[0065] Weigh out NaNO3, Al(NO3)3·9H2O, Ni(NO3)2, Fe(NO3)3·9H2O, Cu(NO3)3·3H2O, Zn(NO3)2, and Mn(CH3COO)2 according to a molar ratio of 31.8:1:1:1:1:1:35.5. Weigh out 89.27g of NaNO3, 15.50g of Al(NO3)3·9H2O, 9.69g of Ni(NO3)2, 13.46g of Fe(NO3)3·9H2O, 8.05g of Cu(NO3)3·3H2O, 9.92g of Zn(NO3)2, and 285.85g of Mn(CH3COO)2. Weigh out 730mL of deionized water as solvent, then evaporate the solvent to dryness in a water bath at 70℃, and finally vacuum dry in a vacuum drying oven at 70℃ for 10h. Then it is fed into a muffle furnace and calcined at 950°C for 10 hours to obtain Na. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 O2.

[0066] The second step is to prepare Na with microsphere morphology. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 O2

[0067] The calcined material was ball-milled, and after ball milling, it was prepared into a uniform dispersion. This dispersion was then dried at a spray temperature of 180°C. The dried powder was collected to obtain Na nanospheres. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 O2.

[0068] Experiments showed that although the water bath solvent evaporation process in Example 2 was relatively slow, the electrochemical performance test results were as follows: Figure 4 As shown, at a 0.5C rate, Na 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 Mn 0.78 The initial reversible specific capacity of O2 is only 115.21 mAh g. -1 It is far lower than the discharge specific capacity of the NM-HEO obtained in Example 1.

[0069] Example 3

[0070] The first step is to synthesize Na. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 MnO2

[0071] Weigh out NaNO3, Al(NO3)3·9H2O, Ni(NO3)2, Fe(NO3)3·9H2O, Cu(NO3)3·3H2O, Zn(NO3)2, and Mn(CH3COO)2 according to a molar ratio of 31.8:1:1:1:1:1:45.5. Weigh out 99.186g of NaNO3, 15.50g of Al(NO3)3·9H2O, 9.69g of Ni(NO3)2, 13.46g of Fe(NO3)3·9H2O, 8.05g of Cu(NO3)3·3H2O, 9.92g of Zn(NO3)2, and 367.53g of Mn(CH3COO)2. Use 820mL of deionized water as solvent, then evaporate the solvent in a water bath at 75℃, and finally vacuum dry in a vacuum drying oven at 90℃ for 24h. Then it is fed into a muffle furnace and calcined at 1150℃ for 14 hours to obtain Na. 0.7 [Al 0.2 Fe 0.2Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 MnO2.

[0072] The second step is to prepare Na with microsphere morphology. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 The calcined material was ball-milled with MnO2, and after ball milling, it was prepared into a uniform dispersion. This dispersion was then dried at a spray temperature of 200°C. The dried powder was collected to obtain Na+ microspheres. 0.7 [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 ] 1 / 9 MnO2.

[0073] Experiments showed that in the first step of Example 3, after vacuum drying, the material was darker in color and harder than in Examples 1 and 2, and the electrochemical performance test results were not much different from those of Example 1.

[0074] Test Example 1

[0075] Using a sodium sheet as the negative electrode, glass fiber as the separator, and adding 150 μL of sodium hexafluorophosphate electrolyte, a self-supporting layered transition metal oxide sodium-ion battery positive electrode material prepared in Example 1 was assembled into a sodium-ion coin cell, and cycle performance testing was performed. Figure 3 As shown, the material exhibits an initial reversible capacity of 123 mAh g⁻¹ at a 0.5C rate within a voltage window of 2.0–4.0 V. -1 It has a relatively high specific capacity.

[0076] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A cobalt-free layered oxide composite material, characterized in that, The general formula of the layered oxide composite material is: Na m [Al 0.2 Fe 0.2 Ni 0.2 Cu 0.2 Zn 0.2 1 / 9 Mn n O2 formula I;​ In Equation I, 0.50 ≤ m ≤ 0.70, 0.78 ≤ n ≤ 1.00; The layered oxide composite material is of type P2; The microstructure of the layered oxide composite material is microspheres with a particle size of 3~9 μm.

2. The method for preparing the layered oxide composite material according to claim 1, characterized in that, The preparation method includes the following steps: (1) A mixture containing sodium source, aluminum source, nickel source, iron source, copper source, zinc source, manganese source and solvent is evaporated, dried and calcined to obtain the precursor of the layered oxide composite material; (2) The precursor of the layered oxide composite material is ball-milled and spray-dried to obtain the layered oxide composite material.

3. The preparation method according to claim 2, characterized in that, The sodium source is selected from at least one of sodium nitrate, sodium sulfate, sodium carbonate, and sodium oxide; The aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, aluminum carbonate, and aluminum oxide; The nickel source is selected from at least one of nickel nitrate, nickel sulfate, nickel carbonate, and nickel oxide; The iron source is selected from at least one of ferric nitrate, ferric sulfate, ferric acetate, and ferric oxide; The copper source is selected from at least one of copper nitrate, copper sulfate, copper carbonate, and copper oxide; The zinc source is selected from at least one of zinc nitrate, zinc sulfate, zinc acetate, and zinc oxide; The manganese source is selected from at least one of manganese acetate, manganese sulfate, manganese carbonate, and manganese oxide (II).

4. The preparation method according to claim 2, characterized in that, The molar ratio of the sodium source, aluminum source, nickel source, iron source, copper source, zinc source, and manganese source is (30~60):1:1:1:1:1:(35~85).

5. The preparation method according to claim 2, characterized in that, The solvent is selected from at least one of water and ethanol.

6. The preparation method according to claim 2, characterized in that, The molar volume ratio of the sodium source to the solvent is 1.40~1.45 mol / L.

7. The preparation method according to claim 2, characterized in that, In step (1), the temperature at which the solvent is evaporated is 70~80℃; The drying temperature is 70~90℃, and the drying time is 10~24h; The calcination temperature is 750~1150℃, and the calcination time is 10~14h.

8. The preparation method according to claim 2, characterized in that, In step (2), the spray drying temperature is 160~200℃ and the spray drying time is 3.0~6.5h.

9. The application of the layered oxide composite material according to claim 1 in a sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator; The positive electrode is a layered oxide composite material; the negative electrode is a sodium sheet; the electrolyte is sodium hexafluorophosphate; and the diaphragm is glass fiber.

10. The application according to claim 9, characterized in that, The sodium-ion battery has an initial reversible capacity of 120~140 mAh g at a 0.5C rate. -1 .

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