Sodium titanate coated sodium-ion battery cathode material and preparation method and application thereof

Abstract

This invention relates to the field of sodium-ion battery cathode materials, and discloses a sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate, its preparation method, and its applications. The sodium-ion battery cathode material includes a core and an in-situ coating layer covering the outer surface of the core, wherein the core is a layered oxide, and the coating layer is sodium copper titanate. This sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate has a low residual alkali content and can improve the rate performance and cycle stability of the material without reducing its initial capacity.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery cathode materials, specifically relating to a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate, its preparation method, and its application. Background Technology

[0002] Over the past few decades, environmental pollution caused by the use of traditional fossil fuels has garnered widespread attention, making the search for green, environmentally friendly, and renewable energy sources a research hotspot in energy storage and energy transition. Lithium-ion batteries, with their advantages of high operating voltage, large specific capacity, and high energy density, have become the most promising candidate for storing these renewable energy sources. However, lithium resources are limited in quantity and unevenly distributed in the Earth's crust. As demand continues to increase, their price continues to rise, limiting their widespread application in large-scale energy storage. This has prompted researchers to continuously develop alternatives with similar performance to lithium-ion batteries but at a lower cost.

[0003] Sodium-ion batteries possess electrochemical performance similar to lithium-ion batteries, and sodium is an abundant and inexpensive element, making it a promising candidate for energy storage and backup power applications. Currently, extensively researched sodium-ion cathode materials mainly include transition metal layered oxides, Prussian blue compounds, and polyanionic compounds. Among these, transition metal layered oxides have attracted considerable attention due to their high specific capacity, low cost, and simple preparation methods. However, the complex phase transitions during charge and discharge can lead to structural collapse of the electrode material, resulting in rapid capacity decay and poor cycle stability. Element doping and surface coating can improve the electrochemical performance of sodium-ion cathode materials. Studies have found that coating the surface of sodium-ion cathode materials with oxides such as titanium dioxide, zirconium dioxide, aluminum oxide, manganese dioxide, and silicon dioxide can improve cycle stability, but often reduces the initial capacity and rate retention.

[0004] Therefore, it is of great significance to research and develop a rapid, simple, and in-situ method for preparing sodium-ion battery cathode materials with a copper titanate coating. The cathode material obtained by this method has low residual alkali content, no reduction or even improvement in initial capacity, and significantly improved rate performance and cycle stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in existing technologies, such as the collapse of the electrode material structure due to complex phase transitions during the charging and discharging process of sodium-ion cathode materials, which leads to rapid capacity decay and poor cycle stability, as well as the defects in the reduction of initial capacity and rate retention caused by improving the cycle stability of materials through element doping and surface coating. This invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate, its preparation method, and its application. This sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate has a low residual alkali content and can improve the rate performance and cycle stability of the material without reducing its initial capacity.

[0006] To achieve the above objectives, the first aspect of the present invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate, wherein the sodium-ion battery cathode material includes a core and a coating layer in-situ coating the outer surface of the core, wherein the core is a layered oxide and the coating layer is sodium copper titanate.

[0007] A second aspect of this invention provides a method for preparing a sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate, wherein the preparation method includes:

[0008] (1) Mix the amine complexing agent, solvent, titanium source and copper source to obtain a copper-titanium amine complex mixed solution;

[0009] (2) The copper-titanium amine complex mixture solution is brought into contact with the layered oxide and stirred until uniformly mixed to obtain a mixture of copper-titanium amine complex and layered oxide.

[0010] (3) The mixture of copper titanium amine complex and layered oxide is sintered to obtain a positive electrode material with in-situ coating modification of sodium copper titanate.

[0011] A third aspect of the present invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate prepared by the aforementioned preparation method.

[0012] The fourth aspect of this invention provides an application of the aforementioned sodium copper titanate in-situ coated modified sodium-ion battery cathode material in a coin cell.

[0013] The beneficial effects of the present invention through the above technical solution are as follows:

[0014] The present invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate and its preparation method. The method utilizes an amine complexing agent to form a copper-titanium amine complex with a copper source and a titanium source. During the sintering process, this complex can react with residual alkali on the material surface to generate sodium copper titanate, which is then attached to the cathode material surface in situ, resulting in a uniform and dense coating. The cathode material obtained by this method has a low residual alkali content, and the initial capacity is not reduced or even improved. The rate performance and cycle stability are significantly improved. That is, the rate performance and cycle stability of the material can be improved without reducing the initial capacity of the material. In addition, the method is fast, simple, short-cycle, easy to operate, and easy to scale up for production. Attached Figure Description

[0015] Figure 1 SEM image of the sodium-ion battery cathode material with in-situ coating modified with sodium copper titanate prepared in Example 1;

[0016] Figure 2 SEM image of the sodium-ion battery cathode material without sodium copper titanate coating modification prepared in Comparative Example 1;

[0017] Figure 3 The diagram shows the 100-cycle coin cell cathode materials prepared in Examples 1, 2, 3, and Comparative Example 1. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] As mentioned above, the first aspect of the present invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate, wherein the sodium-ion battery cathode material includes a core and a coating layer in-situ coating the outer surface of the core, wherein the core is a layered oxide and the coating layer is sodium copper titanate.

[0020] The inventors of this invention have discovered that uniformly coating sodium copper titanate on the surface of the cathode material can reduce residual alkali on the cathode material surface and improve the rate performance and cycle stability of the material without reducing the initial capacity of the material.

[0021] According to the present invention, the layered oxide is prepared by a common high-temperature solid-state method; preferably, the layered oxide has the molecular formula Na. x A u B v Cw O2; wherein A and B are the same or different, each selected from one or more of Ni, Ti, Fe, Mn, Cu, Ca, Zn, Zr, Mg, V, Y, Al and Sc, and C is selected from one or more of Mg, Al, Ti, K, Ca, Co, Cu, Zn, Y, W, Zr, Nb, Mo, Sr and Sn, 0.5 < x < 1.0, 0.1 < u < 0.4, 0.2 < v < 0.7, 0.005 < w < 0.15, and u + v + w = ​​1.

[0022] According to the present invention, preferably, A and B are each selected from one or more of Ni, Ti, Fe, Mn, Cu, Ca, Zn and Al.

[0023] According to the present invention, preferably, C is selected from one or more of Mg, Ti, Ca, Y, W, Zr, Sr and Sn.

[0024] According to the present invention, preferably, 0.6≤x≤0.98, 0.2≤u≤0.35, 0.3≤v≤0.65, and 0.006≤w≤0.12.

[0025] According to the present invention, more preferably, the layered oxide has the molecular formula Na. 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2.

[0026] According to the present invention, the thickness of the coating layer is 10-50 nm, preferably 12-35 nm.

[0027] According to the present invention, the average particle size of the kernel is 5-8.5 μm, preferably 5.5-8 μm.

[0028] According to the present invention, the average particle size of the sodium-ion battery cathode material is 5.5-8.2 μm, preferably 5.8-7.8 μm, and more preferably 7.2-7.8 μm.

[0029] A second aspect of this invention provides a method for preparing a sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate, wherein the preparation method includes:

[0030] (1) Mix the amine complexing agent, solvent, titanium source and copper source to obtain a copper-titanium amine complex mixed solution;

[0031] (2) The copper-titanium amine complex mixture solution is brought into contact with the layered oxide and stirred until uniformly mixed to obtain a mixture of copper-titanium amine complex and layered oxide.

[0032] (3) The mixture of copper titanium amine complex and layered oxide is sintered to obtain a positive electrode material with in-situ coating modification of sodium copper titanate.

[0033] The inventors of this invention have discovered that by using amine complexing agents to form copper-titanium amine complexes with copper and titanium sources, these complexes can react with residual alkali on the material surface during sintering to generate sodium copper titanate which adheres in situ to the surface of the cathode material, thus uniformly and densely coating it. The cathode material obtained by this method has a low residual alkali content and can improve the rate performance and cycle stability of the material without reducing its initial capacity.

[0034] According to the present invention, the layered oxide has the molecular formula Na. x A u B v C w O2, as mentioned above, will not be repeated here.

[0035] According to the present invention, the amine complexing agent is selected from one or more of n-octylamine, isooctylamine, n-butylamine, cyclohexylamine, ethanolamine, 1,2-propanediamine, 2-amino-2-methyl-1-propanol and 3-(diethylamino)-1,2-propanediol, preferably 2-amino-2-methyl-1-propanol.

[0036] According to the present invention, the titanium source is selected from one or more of isopropyl titanate, tetrabutyl titanate, 2-ethyl-1-hexanoate titanium, n-propoxide titanium, titanium ethoxide and tetramethylethanol titanium, preferably isopropyl titanate.

[0037] According to the present invention, the copper source is selected from organic acid copper salt compounds. Preferably, the copper source is selected from one or more of copper acetate, copper oxalate, copper formate, copper citrate, copper pyruvate, copper benzoate, copper succinate, copper hexanoate, copper tartrate, copper neodecanoate, and copper salicylate. More preferably, the copper source is selected from one or more of copper acetate, copper oxalate, and copper formate.

[0038] According to the present invention, the solvent is selected from one or more of ethanol, methanol and isopropanol, preferably ethanol.

[0039] According to the present invention, the molar ratio of the copper source to the amine complexing agent is 1:(2-6), preferably 1:(2-5), and more preferably 1:(3-4).

[0040] According to the present invention, the molar ratio of the transition metal element to the copper source in the layered oxide is 1:(0.001-0.15), preferably 1:(0.01-0.12), and more preferably 1:(0.02-0.1).

[0041] According to the present invention, the molar ratio of copper element in the copper source to titanium element in the titanium source is 1:(1-6), preferably 1:(2-5), and more preferably 1:(3-4).

[0042] According to the present invention, the solid-liquid volume ratio of the layered oxide and the solvent is 1:(0.1-3), preferably 1:(0.5-1.5), and more preferably 1:(0.8-1).

[0043] According to the present invention, the sintering process comprises two stages: the first stage is maintained in an air atmosphere at 50-80°C for 1-4 hours at a heating rate of 2-7°C / min; the second stage is maintained in an air atmosphere at 120-800°C for 3-10 hours at a heating rate of 2-10°C / min.

[0044] According to the present invention, after sintering and waiting for natural cooling, the sodium-ion battery cathode material with in-situ coating modified by sodium copper titanate can be obtained by passing it through a 300-400 mesh sieve.

[0045] A third aspect of the present invention provides a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate prepared by the aforementioned preparation method.

[0046] The fourth aspect of this invention provides an application of the aforementioned sodium copper titanate in-situ coated modified sodium-ion battery cathode material in a coin cell.

[0047] Button fabrication and testing:

[0048] The sodium-ion battery positive electrode material modified by in-situ coating of sodium copper titanate provided by this invention, conductive carbon black, and polyvinylidene fluoride are mixed in a ratio of 96:2:2. After uniform mixing, N-methylpyrrolidone is added to obtain a slurry. The slurry is coated on aluminum foil, and after vacuum drying and cutting, the sodium-ion battery positive electrode material is obtained. Using a sodium metal sheet as the negative electrode, glass fiber as the separator, and NaClO4 as the electrolyte, the negative electrode shell, sodium metal sheet, separator, electrolyte, positive electrode sheet, gasket, spring, and positive electrode shell are pressed and sealed to form a button-type sodium-ion battery.

[0049] The present invention will be described in detail below through embodiments.

[0050] In the following examples and comparative examples:

[0051] The residual alkali parameter was determined by potentiometric titration.

[0052] The charge and discharge parameters were measured using a coin cell battery in the LAND battery charge and discharge test system.

[0053] The rate parameter was measured using a coin cell battery in the LAND battery charge-discharge test system.

[0054] The 100-cycle performance parameters were measured using a coin cell battery in the LAND battery charge-discharge test system.

[0055] It should be noted that the LAND battery charge-discharge system in this invention is used to perform capacity, rate, and cycle tests on coin cells under certain charge-discharge test regimes; it is not a type of battery. The coin cell performance of all samples in this invention was measured using the LAND battery charge-discharge system.

[0056] The cathode material raw materials are prepared using a conventional high-temperature solid-state method.

[0057] Example 1

[0058] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0059] The preparation method specifically includes:

[0060] (1) According to the copper-amine molar ratio of 1:3, the copper-titanium molar ratio of 1:3, and the solid-liquid volume ratio of layered oxide and solvent of 1:0.8, weigh 2-amino-2-methyl-1-propanol, copper formate, isopropyl titanate and ethanol. First, add 2-amino-2-methyl-1-propanol to ethanol and stir to dissolve. Then, add isopropyl titanate and copper formate in sequence and stir until dissolved to obtain a mixed solution of copper-titanium-amine complex.

[0061] (2) Layered oxide (Na) 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2) Add copper titanium amine complex mixed solution to make the molar ratio of transition metal element in layered oxide to copper source based on copper element 1:0.05. Stir the mixture thoroughly and mix evenly to obtain a mixture of copper titanium amine complex and layered oxide.

[0062] (3) The mixture is transferred to a box furnace for pre-sintering and re-sintering. The pre-sintering temperature is set at 60℃, the heating rate is 2℃ / min, and the holding time is 3h. Then the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 6h. After natural cooling, the sodium-ion battery cathode material with in-situ copper titanate coating is obtained by passing it through a 325-mesh sieve. The parameters of the sodium-ion battery cathode material with in-situ copper titanate coating are shown in Table 1.

[0063] Figure 1 The image shows a SEM image of the sodium-ion battery cathode material with in-situ coating modified with sodium copper titanate prepared in Example 1. Figure 1 It can be seen that after in-situ coating modification with sodium copper titanate, there is a fine and uniform coating on the surface of the material.

[0064] Example 2

[0065] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0066] The preparation method specifically includes:

[0067] (1) According to the copper-amine molar ratio of 1:3, the copper-titanium molar ratio of 1:3, and the solid-liquid volume ratio of layered oxide and solvent of 1:0.8, weigh 2-amino-2-methyl-1-propanol, copper formate, isopropyl titanate and ethanol. First, add 2-amino-2-methyl-1-propanol to ethanol and stir to dissolve. Then, add isopropyl titanate and copper formate in sequence and stir until dissolved to obtain a mixed solution of copper-titanium-amine complex.

[0068] (2) Layered oxide (Na) 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2) is added to a copper-titanium amine complex mixture solution, so that the molar ratio of the transition metal element in the layered oxide to the copper source (calculated as copper element) is 1:0.02. The mixture is stirred thoroughly and mixed evenly to obtain a mixture of copper-titanium amine complex and layered oxide.

[0069] (3) The mixture is transferred to a box furnace for pre-sintering and re-sintering. The pre-sintering temperature is set at 60℃, the heating rate is 2℃ / min, and the holding time is 3h. Then the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 6h. After natural cooling, the sodium-ion battery cathode material with in-situ copper titanate coating is obtained by passing it through a 325-mesh sieve. The parameters of the sodium-ion battery cathode material with in-situ copper titanate coating are shown in Table 1.

[0070] Example 3

[0071] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0072] The preparation method specifically includes:

[0073] (1) According to the copper-amine molar ratio of 1:3, the copper-titanium molar ratio of 1:3, and the solid-liquid volume ratio of layered oxide and solvent of 1:0.8, weigh 2-amino-2-methyl-1-propanol, copper formate, isopropyl titanate and ethanol. First, add 2-amino-2-methyl-1-propanol to ethanol and stir to dissolve. Then, add isopropyl titanate and copper formate in sequence and stir until dissolved to obtain a mixed solution of copper-titanium-amine complex.

[0074] (2) Layered oxide (Na) 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2) is added to a copper-titanium amine complex mixture solution, so that the molar ratio of the transition metal element in the layered oxide to the copper source (calculated as copper element) is 1:0.08. The mixture is stirred thoroughly and mixed evenly to obtain a mixture of copper-titanium amine complex and layered oxide.

[0075] (3) The mixture is transferred to a box furnace for pre-sintering and re-sintering. The pre-sintering temperature is set at 60℃, the heating rate is 2℃ / min, and the holding time is 3h. Then the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 6h. After natural cooling, the sodium-ion battery cathode material with in-situ copper titanate coating is obtained by passing it through a 325-mesh sieve. The parameters of the sodium-ion battery cathode material with in-situ copper titanate coating are shown in Table 1.

[0076] Example 4

[0077] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0078] The preparation method specifically includes:

[0079] (1) According to the copper-amine molar ratio of 1:3, the copper-titanium molar ratio of 1:3, and the solid-liquid volume ratio of layered oxide and solvent of 1:0.8, weigh 2-amino-2-methyl-1-propanol, copper formate, isopropyl titanate and ethanol. First, add 2-amino-2-methyl-1-propanol to ethanol and stir to dissolve. Then, add isopropyl titanate and copper formate in sequence and stir until dissolved to obtain a mixed solution of copper-titanium-amine complex.

[0080] (2) Layered oxide (Na) 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2) is added to a copper-titanium amine complex mixture solution, so that the molar ratio of the transition metal element in the layered oxide to the copper source (calculated as copper element) is 1:0.10. The mixture is stirred thoroughly and mixed evenly to obtain a mixture of copper-titanium amine complex and layered oxide.

[0081] (3) The mixture is transferred to a box furnace for pre-sintering and re-sintering. The pre-sintering temperature is set at 60℃, the heating rate is 2℃ / min, and the holding time is 3h. Then the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 6h. After natural cooling, the sodium-ion battery cathode material with in-situ copper titanate coating is obtained by passing it through a 325-mesh sieve. The parameters of the sodium-ion battery cathode material with in-situ copper titanate coating are shown in Table 1.

[0082] Example 5

[0083] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0084] Sodium-ion battery cathode material with in-situ coating modification of sodium copper titanate was prepared using the same method as in Example 1, except that "copper formate" was replaced with "copper acetate", the pre-sintering temperature was set to 70°C, the heating rate was 2°C / min, and the temperature was held for 2.5h. Then, the temperature was increased to 400°C at a heating rate of 5°C / min and held for 7h.

[0085] The parameters of the sodium-ion battery cathode material prepared by in-situ coating with sodium copper titanate are shown in Table 1.

[0086] Example 6

[0087] This embodiment illustrates the preparation of the sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate according to the present invention.

[0088] Sodium-ion battery cathode material with in-situ coating modification of sodium copper titanate was prepared using the same method as in Example 1, except that "copper formate" was replaced with "copper oxalate", the pre-sintering temperature was set to 80°C, the heating rate was 2°C / min, and the temperature was held for 2 hours. Then, the temperature was increased to 500°C at a heating rate of 5°C / min and held for 5 hours.

[0089] The parameters of the sodium-ion battery cathode material prepared by in-situ coating with sodium copper titanate are shown in Table 1.

[0090] Example 7

[0091] A sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate and its preparation method include the following steps:

[0092] (1) According to the copper-amine molar ratio of 1:3, the copper-titanium molar ratio of 1:3, and the solid-liquid volume ratio of layered oxide and solvent of 1:0.8, weigh ethanolamine, copper oxalate, isopropyl titanate and ethanol. First, add ethanolamine to ethanol and stir to dissolve. Then, add isopropyl titanate and copper oxalate in sequence and stir until dissolved to obtain a mixed solution of copper-titanium-amine complex.

[0093] (2) Layered oxide (Na) 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.06 Ti 0.03 O2) is added to a copper-titanium amine complex mixture solution, so that the molar ratio of the transition metal element in the layered oxide to the copper source (calculated as copper element) is 1:0.05. The mixture is stirred thoroughly and mixed evenly to obtain a mixture of copper-titanium amine complex and layered oxide.

[0094] (3) The mixture is transferred to a box furnace for pre-sintering and re-sintering. The pre-sintering temperature is set at 60℃, the heating rate is 2℃ / min, and the holding time is 3h. Then the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 6h. After natural cooling, the sodium-ion battery cathode material with in-situ copper titanate coating is obtained by passing it through a 325-mesh sieve. The parameters of the sodium-ion battery cathode material with in-situ copper titanate coating are shown in Table 1.

[0095] Comparative Example 1

[0096] A sodium-ion battery cathode material without sodium copper titanate coating modification and its preparation method include the following steps:

[0097] Weigh the same amount of layered oxide as in Example 1, and directly transfer it to a box furnace for sintering. Set the pre-sintering temperature to 60°C, the heating rate to 2°C / min, and hold for 3 hours. Then, heat to 450°C at a heating rate of 5°C / min and hold for 6 hours. After natural cooling, the sodium-ion battery cathode material without in-situ coating of sodium copper titanate is obtained. The parameters of the sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate are shown in Table 1.

[0098] Figure 2 The image shows a SEM image of the sodium-ion battery cathode material prepared in Comparative Example 1 without sodium copper titanate coating modification. Figure 2 It can be seen that the surface of the material without sodium copper titanate coating modification is smoother.

[0099] Figure 3 The diagram shows the 100-cycle circuit diagrams for Examples 1, 2, 3, and Comparative Example 1. Figure 3 It can be seen that the retention rates of Examples 1, 2, 3 and Comparative Example 1 after 100 cycles of 1C / 1C in the voltage range of 2.0-4.0V were 92.6%, 87.8%, 90.0% and 83.2%, respectively, indicating that the in-situ coating modification with sodium copper titanate can significantly improve the cycling stability of the material.

[0100] Comparative Example 2

[0101] Sodium-ion battery cathode material with in-situ coating modification of sodium copper titanate was prepared using the same method as in Example 1, except that "copper formate" was replaced with "copper nitrate".

[0102] The parameters of the sodium-ion battery cathode material prepared by in-situ coating with sodium copper titanate are shown in Table 1.

[0103] Comparative Example 3

[0104] Sodium-ion battery cathode material with in-situ coating modification of sodium copper titanate was prepared using the same method as in Example 1, except that "isopropyl titanate" was replaced with "titanium tetrachloride".

[0105] The parameters of the sodium-ion battery cathode material prepared by in-situ coating with sodium copper titanate are shown in Table 1.

[0106] Comparative Example 4

[0107] Sodium-ion battery cathode material with in-situ coating modified with sodium copper titanate was prepared using the same method as in Example 1, except that the following was replaced with the following: "Setting the pre-sintering temperature to 60°C, heating rate to 2°C / min, holding for 3 hours, then heating to 450°C at a rate of 5°C / min, and holding for 6 hours" was replaced with "Setting the pre-sintering temperature to 100°C, heating rate to 5°C / min, holding for 1.5 hours, then heating to 400°C at a rate of 7°C / min, and holding for 5.5 hours".

[0108] The parameters of the sodium-ion battery cathode material prepared by in-situ coating with sodium copper titanate are shown in Table 1.

[0109] Table 1

[0110]

[0111] As can be seen from Table 1, the thickness of the coating layer (sodium copper titanate) of the sodium-ion battery cathode material prepared by the method of the present invention is 12-35 nm; and the average particle size of the prepared sodium-ion battery cathode material is 7.45-7.79 μm.

[0112] Test case

[0113] Button cell fabrication and performance testing:

[0114] The positive electrode materials with in-situ coating and modification of sodium copper titanate prepared in Examples 1-7, the positive electrode materials without sodium copper titanate coating and modification prepared in the comparative examples, the sodium-ion battery positive electrode materials with in-situ coating and modification of sodium copper titanate prepared in Comparative Examples 2-4, conductive carbon black, and polyvinylidene fluoride were mixed in a ratio of 96:2:2. After uniform mixing, N-methylpyrrolidone was added to obtain a slurry. The slurry was coated on aluminum foil, and after vacuum drying and cutting, sodium-ion battery positive electrode materials were obtained. Using sodium metal sheet as negative electrode, glass fiber as separator, and NaClO4 as electrolyte, the negative electrode shell, sodium metal sheet, separator, electrolyte, positive electrode sheet, gasket, spring, and positive electrode shell were pressed and sealed to form a button-type sodium-ion battery.

[0115] Electrochemical performance tests were conducted at a voltage of 2.0-4.0V. The first discharge specific capacity was tested at 0.1C / 0.1C, and then 100 cycles were performed at 1C / 1C.

[0116] Table 2

[0117]

[0118]

[0119] The test results obtained are as follows: After in-situ coating modification with sodium copper titanate, as shown in Table 2, the initial discharge specific capacity of Examples 1, 2, and 3 are 141.2 mAh / g, 136.9 mAh / g, and 137.1 mAh / g, respectively; the 5C rate retention rates are 86.1%, 78.2%, and 81.6%, respectively; and the 100-cycle retention rates are 92.6%, 87.8%, and 90.0%, respectively. In contrast, the initial discharge specific capacity, 5C rate retention rate, and 100-cycle retention rate of Comparative Example 1 are 135.7 mAh / g, 67.2%, and 83.2%, respectively. Furthermore, by comparing Examples 1-7 and Comparative Examples 1-4, it can be found that in-situ coating modification with sodium copper titanate can significantly improve the rate performance and cycle stability of the material, while the discharge specific capacity remains basically unchanged or even increases.

[0120] Table 3

[0121]

[0122] Table 3 shows the test data of residual alkali in the examples and comparative examples. As can be seen from Table 3, the sodium-ion battery cathode material modified by in-situ coating of copper titanate prepared in this invention has a low residual alkali content, indicating that the copper-titanium amine complex reacts with the residual alkali on the surface of the core material during the sintering process, effectively reducing the residual alkali on the material surface and alleviating the material's sensitivity to moisture.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a sodium-ion battery cathode material modified by in-situ coating with sodium copper titanate, characterized in that, The preparation method includes: (1) Mix the amine complexing agent, solvent, titanium source and copper source to obtain a copper-titanium amine complex mixed solution; (2) The copper-titanium amine complex mixture solution is brought into contact with the layered oxide and stirred until uniformly mixed to obtain a mixture of copper-titanium amine complex and layered oxide. (3) The copper-titanium amine complex and the layered oxide mixture are sintered to obtain a positive electrode material with in-situ coating and modification of sodium copper titanate; The amine complexing agent is selected from one or more of n-octylamine, isooctylamine, n-butylamine, cyclohexylamine, ethanolamine, 1,2-propanediamine, 2-amino-2-methyl-1-propanol and 3-(diethylamino)-1,2-propanediol; The titanium source is selected from one or more of isopropyl titanate, tetrabutyl titanate, titanium 2-ethyl-1-hexanoate, titanium n-propoxide, titanium ethoxide, and titanium tetramethylethanol. The copper source is selected from organic acid copper salt compounds; The sintering process consists of two stages: the first stage is maintained in an air atmosphere at 50-80℃ for 1-4 hours at a heating rate of 2-7℃ / min; the second stage is maintained in an air atmosphere at 400-500℃ for 3-10 hours at a heating rate of 2-10℃ / min.

2. The preparation method according to claim 1, wherein, The copper source is selected from one or more of copper acetate, copper oxalate, copper formate, copper citrate, copper pyruvate, copper benzoate, copper succinate, copper hexanoate, copper tartrate, copper neodecanoate, and copper salicylate.

3. The preparation method according to claim 1, wherein, The layered oxide has the molecular formula Na. x A u B v C w O2; wherein A and B are the same or different, each selected from one or more of Ni, Ti, Fe, Mn, Cu, Ca, Zn, Zr, Mg, V, Y, Al and Sc, and C is selected from one or more of Mg, Al, Ti, K, Ca, Co, Cu, Zn, Y, W, Zr, Nb, Mo, Sr and Sn, 0.5 < x < 1.0, 0.1 < u < 0.4, 0.2 < v < 0.7, 0.005 < w < 0.15, and u + v + w = ​​1.

4. The preparation method according to claim 3, wherein, The layered oxide has the molecular formula Na. 0.97 Ni 0.26 Fe 0.30 Mn 0.35 Mg 0.05 Ti 0.04 O2.

5. The preparation method according to claim 1, wherein, The molar ratio of the copper source to the amine complexing agent is 1:(2-6). And / or, the molar ratio of the transition metal element to the copper source in the layered oxide is 1:(0.001-0.15). And / or, the molar ratio of copper in the copper source to titanium in the titanium source is 1:(1-6). And / or, the solid-liquid volume ratio of the layered oxide to the solvent is 1:(0.1-3).

6. The preparation method according to claim 5, wherein, The molar ratio of the copper source to the amine complexing agent is 1:(2-5). And / or, the molar ratio of the transition metal element to the copper source in the layered oxide is 1:(0.01-0.12). And / or, the molar ratio of copper in the copper source to titanium in the titanium source is 1:(2-5). And / or, the solid-liquid volume ratio of the layered oxide to the solvent is 1:(0.5-1.5).

7. A sodium-ion battery cathode material with in-situ coated sodium copper titanate modified by the preparation method according to any one of claims 1-6.

8. The sodium-ion battery cathode material according to claim 7, wherein, The sodium-ion battery cathode material includes a core and a coating layer that is in situ coated on the outer surface of the core, wherein the core is a layered oxide and the coating layer is sodium copper titanate.

9. The sodium-ion battery cathode material according to claim 8, wherein, The thickness of the coating layer is 10-50 nm; The average particle size of the kernel is 5-8.5 μm.

10. The sodium-ion battery cathode material according to claim 9, wherein, The thickness of the coating layer is 12-35 nm; The average particle size of the kernel is 5.5-8 μm.

11. The application of a sodium-ion battery cathode material modified by in-situ coating of sodium copper titanate as described in any one of claims 7-10 in a coin cell.

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