A sodium-ion battery layered positive electrode material, a surface coating method and application

Abstract

The application belongs to the technical field of sodium ion batteries, and discloses a sodium ion battery layered positive electrode material, a surface coating method and application, wherein the surface coating method comprises the following steps: mixing hydroxide and a sodium ion battery layered positive electrode material, fully grinding and coating, and then sintering to obtain a surface coated sodium ion battery layered positive electrode material. The hydroxide coating proposed in the application can decompose to generate water at high temperature, can reduce residual alkali, and can form an oxide coating layer on the surface of the layered positive electrode by decomposing the hydroxide, thereby forming a protective layer and inhibiting the continuous generation of residual alkali to protect the stability of the material. The method used in the application has the advantages of simple and controllable process, and can realize large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a layered cathode material for sodium-ion batteries, a surface coating method, and its application. Background Technology

[0002] Currently, lithium-ion batteries are widely used in our daily transportation and communication fields due to their advantages such as high energy density and long cycle life. Sodium and lithium have similar physical and chemical properties, and sodium resources are abundant. Therefore, sodium can be used to replace lithium as a new energy storage system. The main factor restricting the development of sodium-ion batteries is the cathode material. Sodium-ion battery cathode materials mainly include transition metal layered oxides, polyanionic compounds, and Prussian blue compounds. Among them, layered cathode materials are the most likely to be directly applied to sodium-ion batteries. However, the surface of layered oxide cathodes is prone to react with water and carbon dioxide in the air, producing residual alkali, which seriously affects the processing performance of the material and the electrochemical performance of the battery. Therefore, it is necessary to coat and modify the material to reduce and suppress the generation of residual alkali.

[0003] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: The existing patent (ZL202010191573.2) proposes a method to remove residual alkali by treating the material with acid. This method can achieve the effect of removing residual alkali, but the layered material will continue to react with air to produce residual alkali. It cannot provide subsequent protection for the layered material and cannot inhibit the continuous generation of residual alkali. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a layered cathode material for sodium-ion batteries, a surface coating method, and its application.

[0005] This invention is implemented as follows: a method for coating the surface of a layered positive electrode material for a sodium-ion battery, the method comprising: A certain amount of hydroxide is mixed with the layered cathode material of sodium-ion batteries, and then thoroughly ground and coated. The mixture is sintered to obtain the surface-coated layered cathode material of sodium-ion batteries.

[0006] Furthermore, the mass ratio of the hydroxide to the sodium-ion battery layered cathode material is (0.01-1):100.

[0007] Furthermore, the layered cathode material of the sodium-ion battery is Na. x Ni α Fe β Mn γ M 1-α-β-γO2, M is one or more of Li, Mg, B, Si, Ca, Al, Zn, K, Cu, Co, Zr, Ge, Sn, Pb, P, Sb, Bi, Nb, Mo, Ti, and Sr; where 0.5 <x≤1,0<α<1, 0<β<1, 0<γ<1, α+β+γ≤1。

[0008] Furthermore, the hydroxide is one or more of magnesium hydroxide, zinc hydroxide, zirconium hydroxide, aluminum hydroxide, copper hydroxide, indium hydroxide, bismuth hydroxide, and barium hydroxide.

[0009] Furthermore, the sintering temperature of the sodium-ion battery layered cathode material and hydroxide is 200-1200℃.

[0010] Another object of the present invention is to provide a sodium-ion battery layered cathode material prepared by implementing the above-described sodium-ion battery layered cathode material surface coating method, wherein the sodium-ion battery layered cathode material surface coating method coats the surface of the sodium-ion battery layered cathode material.

[0011] Another object of the present invention is to provide an application of the aforementioned layered cathode material in sodium-ion batteries.

[0012] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows: First, addressing the technical problems existing in the prior art and the difficulty in solving them, this paper closely analyzes, in conjunction with the technical solution to be protected by this invention and the results and data obtained during the research and development process, how the technical solution of this invention solves the technical problems, and the inventive technical effects brought about by solving these problems. The specific description is as follows: Compared with the prior art, the present invention coats hydroxide onto the surface of the layered cathode material of sodium-ion battery. The coated hydroxide decomposes into water and oxides at high temperature. The water can reduce residual alkali, while the oxide generated by the decomposition of hydroxide coats the surface of the layered cathode, forming an effective protective layer. This can inhibit the continued generation of residual alkali and improve the electrochemical performance of the material.

[0013] The method used in this invention has the advantages of simple and controllable process, and can realize large-scale industrial production.

[0014] Second, considering the technical solution as a whole or from a product perspective, the technical effects and advantages of the technical solution to be protected by this invention are specifically described as follows: The hydroxide coating method provided by this invention can achieve two goals at once. It can reduce residual alkali and inhibit the generation of residual alkali by simply using the coating method. It is simple, controllable and low cost.

[0015] Third, as supplementary evidence of the inventive step of the claims of this invention, it is also reflected in the following important aspects: (1) The expected benefits and commercial value of the technical solution of this invention after transformation are as follows: Sodium-ion batteries are a promising new energy storage system. The hydroxide coating method for cathode materials proposed in this invention can reduce residual alkali and suppress its generation, providing a stable cathode material for sodium-ion batteries and promoting the large-scale application of sodium-ion batteries.

[0016] (2) Whether the technical solution of the present invention solves the technical problem that people have long wanted to solve but have never been able to solve successfully: Existing technologies can only remove residual alkali but cannot inhibit its continuous generation. The method and application of coating the surface of layered cathode material for sodium-ion batteries provided by this invention can effectively solve the technical problem of how to reduce and inhibit the generation of residual alkali by using only the coating method. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method for coating the surface of layered cathode material for sodium-ion batteries provided in this embodiment of the invention; Figure 2 The NaMn provided in Embodiment 1 of this invention 0.4 Fe 0.35 Ni 0.25 Scanning electron microscope (SEM) image of O2 coated with aluminum hydroxide. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] To enable those skilled in the art to fully understand how the present invention is specifically implemented, this section provides an explanatory description of the embodiments that expand upon the technical solutions of the claims.

[0020] like Figure 1 As shown, the method for coating the surface of a layered cathode material for a sodium-ion battery provided in this embodiment of the invention includes: S101, a certain amount of hydroxide is mixed with the layered positive electrode material of sodium-ion battery, and then fully ground and coated. S102, sinter the mixture to obtain a surface-coated layered cathode material for sodium-ion batteries.

[0021] Furthermore, the mass ratio of the hydroxide to the sodium-ion battery layered cathode material is (0.01-1):100; Furthermore, the layered cathode material of the sodium-ion battery is Na. x Ni α Fe β Mn γ M 1-α-β-γ O2, M is one or more of Li, Mg, B, Si, Ca, Al, Zn, K, Cu, Co, Zr, Ge, Sn, Pb, P, Sb, Bi, Nb, Mo, Ti, and Sr; where 0.5 <x≤1,0<α<1, 0<β<1, 0<γ<1, α+β+γ≤1。

[0022] Furthermore, the hydroxide is one or more of magnesium hydroxide, zinc hydroxide, zirconium hydroxide, aluminum hydroxide, copper hydroxide, indium hydroxide, bismuth hydroxide, and barium hydroxide.

[0023] Furthermore, the sintering temperature of the layered cathode material and hydroxide is 200-1200℃.

[0024] This invention also provides an application of a method for coating the surface of a layered cathode material in a sodium-ion battery. In this method, hydroxides decompose at high temperatures to produce water, reducing residual alkali. Simultaneously, the oxides generated from the decomposition of hydroxides coat the surface of the layered cathode, inhibiting the continued generation of residual alkali.

[0025] This invention also provides a sodium-ion battery layered cathode material prepared by the aforementioned sodium-ion battery layered cathode material surface coating method, wherein the sodium-ion battery layered cathode material surface coating method coats the surface of the sodium-ion battery layered cathode material.

[0026] This invention also provides the application of the layered cathode material in sodium-ion batteries.

[0027] Example 1 Na₂CO₃, MnO₂, Fe₂O₃, and NiO were ball-milled in a specific ratio and then sintered at high temperature to obtain NaMn. 0.4 Fe 0.35 Ni 0.25 O2. Aluminum hydroxide and NaMn were mixed in a mass ratio of 0.2:100. 0.4 Fe 0.35 Ni 0.25 O2 was mixed evenly using a high-speed mixer, and then sintered at 400℃ for 6 hours. The pH of the material before and after coating was tested. Figure 2The image shows a SEM image after coating, clearly showing a layer of small alumina particles on the surface. In this embodiment of the invention, the materials before and after treatment are used as positive electrodes, sodium metal as negative electrodes, glass fiber as a separator, and a NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution as an electrolyte. 3% by weight of fluorinated ethylene carbonate (FEC) is added to the electrolyte. A button cell is assembled and charged / discharge tests are performed with a current density of 12 mA / g and a voltage range of 2-4 V.

[0028] Example 2 A precursor nickel-iron-copper-manganese hydroxide was prepared by co-precipitation of MnSO4, CuSO4, NiSO4, and FeSO4 in a certain proportion. Na2CO3 was then mixed with the precursor and sintered at high temperature to obtain NaCu. 0.03 Ni 0.25 Fe 0.30 Mn 0.42 O2. A mixture of magnesium hydroxide, copper hydroxide, and NaCu in a mass ratio of 0.1:0.2:100. 0.03 Ni 0.25 Fe 0.30 Mn 0.42 O2 was mixed in a coating fusion machine and then sintered at 500°C for 2 hours. The pH was tested before and after coating. In this embodiment, the materials before and after treatment were used as positive electrodes, sodium metal as negative electrodes, glass fiber as separators, and a NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution as electrolyte. 3% by weight of fluorinated ethylene carbonate (FEC) was added to the above electrolyte. Button batteries were assembled and charge-discharge tests were conducted at a current density of 12 mA / g and a voltage range of 2-4 V.

[0029] Example 3 Na₂CO₃, MnO₂, Fe₂O₃, NiO, ZnO, and CoO were ball-milled in a specific ratio and then sintered at high temperature to obtain NaNi. 0.2 Zn 0.04 Co 0.01 Fe 0.3 Mn 0.45 O2. Add zinc hydroxide in a mass ratio of 0.5:100; NaNi 0.2 Zn 0.04 Co 0.01 Fe 0.3 Mn 0.45O2 ball milling for 2 hours, followed by sintering at 300℃ for 3 hours. The pH before and after coating was tested. Using the materials before and after treatment in this embodiment as positive electrodes, metallic sodium as the negative electrode, glass fiber as the separator, and a NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution as the electrolyte, along with 3% by weight of fluorinated ethylene carbonate (FEC) added to the electrolyte, button batteries were assembled and charge-discharge tests were conducted at a current density of 12 mA / g and a voltage range of 2-4 V.

[0030] Example 4 Na₂CO₃, MnO₂, Fe₂O₃, NiO, SnO₂, and ZrO are ball-milled in a specific ratio and then sintered at high temperature to obtain Na₂CO₃. 0.7 Mn 0.58 Fe 0.20 Ni 0.18 Sn 0.02 Zr 0.02 O2 mixes barium hydroxide and zirconium hydroxide in a mass ratio of 0.3:0.6:100; Na 0.7 Mn 0.58 Fe 0.20 Ni 0.18 Sn 0.02 Zr 0.02 O2 was mixed evenly in a coating fusion machine and sintered at 600°C for 4 hours. The pH was tested before and after coating. In this embodiment, the materials before and after treatment were used as positive electrodes, sodium metal as negative electrodes, glass fiber as separators, and a NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution as electrolyte. 3% by weight of fluorinated ethylene carbonate (FEC) was added to the electrolyte. Button batteries were assembled and charge-discharge tests were conducted at a current density of 12 mA / g and a voltage range of 2-4V.

[0031] Example 5 Na₂CO₃, CaO, Bi₂O₃, MnO₂, Fe₂O₃, NiO, and TiO₂ were ball-milled in a specific ratio and then sintered at high temperature to obtain Na₂CO₃. 0.72 Mn 0.50 Fe 0.20 Ni 0.20 Ti 0.06 Bi 0.03 Ca 0.01 O2 will mix indium hydroxide: bismuth hydroxide: Na in a mass ratio of 0.1:0.3:100. 0.72 Mn 0.50 Fe 0.20 Ni 0.20 Ti 0.06 Bi 0.03 Ca 0.01O2 was mixed evenly in a high-speed mixer and treated at 700°C for 3 hours. The pH was tested before and after coating. In this embodiment, the materials before and after treatment were used as positive electrodes, sodium metal as negative electrodes, glass fiber as separators, and a NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution as electrolyte. 3% by weight of fluorinated ethylene carbonate (FEC) was added to the above electrolyte. Button batteries were assembled and charge-discharge tests were conducted at a current density of 12 mA / g and a voltage range of 2-4V.

[0032] The embodiments of the present invention have achieved some positive results during the research and development or use process, and have indeed great advantages compared with the prior art. The following content describes them in conjunction with the data, charts and other information of the experimental process.

[0033] The pH and electrochemical cycling performance results of the layered cathode materials prepared in Examples 1-5 of this invention before and after coating are shown in Table 1. It can be seen that the pH value is significantly reduced after coating, indicating that it can effectively reduce and inhibit the generation of residual alkali. The capacity retention rate after 100 cycles after treatment is also improved to a certain extent.

[0034] Table 1. pH and electrochemical cycling performance of the layered cathode materials prepared in Examples 1-5 before and after coating.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for coating the surface of a layered positive electrode material for a sodium-ion battery, characterized in that, include: A certain amount of hydroxide is mixed with a layered cathode material for sodium-ion batteries, and then thoroughly ground and coated. The mixture is sintered to obtain a layered cathode material for sodium-ion batteries with a surface coating. The mass ratio of the hydroxide to the layered cathode material for sodium-ion batteries is (0.01-1):

100. The hydroxide is one or more of magnesium hydroxide, copper hydroxide, indium hydroxide, bismuth hydroxide, and barium hydroxide; The decomposition of the coating hydroxide can reduce residual alkali and form a protective layer on the material surface. The coated hydroxide decomposes into water and oxides at high temperatures. Water can reduce residual alkali, while the oxides generated by the decomposition of hydroxide coat the layered positive electrode surface, forming an effective protective layer.

2. The method for coating the surface of a layered positive electrode material for a sodium-ion battery as described in claim 1, characterized in that, The layered cathode material of the sodium-ion battery is Na. x Ni α Fe β Mn γ M 1-α-β-γ O2, M is one or more of Li, Mg, B, Si, Ca, Al, Zn, K, Cu, Co, Zr, Ge, Sn, Pb, P, Sb, Bi, Nb, Mo, Ti, and Sr; where 0.5 <x≤1,0<α<1,0<β<1,0<γ<1,α+β+γ≤1。 3. The method for coating the surface of layered positive electrode material for sodium-ion batteries as described in claim 1, characterized in that, The sintering temperature of the sodium-ion battery layered cathode material and hydroxide is 200-1200℃.

4. A sodium-ion battery layered cathode material prepared by the method for coating the surface of a sodium-ion battery layered cathode material according to any one of claims 1-3, characterized in that, The method for coating the surface of the layered cathode material of the sodium-ion battery involves coating the surface of the layered cathode material of the sodium-ion battery.

5. An application of the layered cathode material of sodium-ion battery as described in claim 4 in a sodium-ion battery.

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