High-entropy doped sodium titanium phosphate battery negative electrode material, preparation method and application

Abstract

The invention belongs to the technical field of electrochemical metal ion battery materials, and discloses a high-entropy-doped sodium titanium phosphate battery negative electrode material, a preparation method and application, the high-entropy-doped sodium titanium phosphate battery negative electrode material is prepared by a sol-gel method, NaTi2 (PO4) 3 is prepared from a titanium source, citric acid, a sodium source and a phosphorus source and serves as a main body structure, aluminum magnesium tin niobium metal cations are introduced into a Ti site, and the high-entropy-doped sodium titanium phosphate battery negative electrode material is obtained. A high-entropy doped sodium titanium phosphate material with uniform element distribution and a stable NASICON structure is obtained through sol formation, gel drying and calcination, and then the high-entropy doped sodium titanium phosphate material is mixed with a conductive agent and a binder to prepare an electrode slurry sodium titanium phosphate battery negative electrode material, so that lattice regulation and control, configuration entropy stability and charge transfer performance improvement are realized. The prepared material has high initial reversible capacity, low oxidation / reduction peak potential difference and excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical metal-ion battery materials technology, and in particular to a high-entropy doped sodium titanium phosphate battery anode material, its preparation method, and its application. Background Technology

[0002] With the increasing demand for large-scale, safe, and low-cost energy storage systems, aqueous sodium-ion batteries (Aqueous Sodium) are gaining popularity. Ion batteries (ASIBs) have attracted widespread attention due to their use of abundant sodium resources, high safety, environmental friendliness, and cost advantages. Among many anode materials, NTP stands out because of its NASICON structure, an open three-dimensional framework structure, and relatively large Na+ content. + With its channel, high ion migration rate, and good structural and chemical stability, it is considered one of the more promising anodes in the ASIB system.

[0003] However, the application of existing NTP anode materials in aqueous sodium-ion batteries still faces the following major problems or limitations: (1) The actual reversible capacity is far from the theoretical capacity. Although the theoretical capacity of NTP is high, its capacity in actual battery systems is often far lower than the theoretical value due to poor electronic conductivity and low utilization of active materials. Even after carbon coating or nano-processing, its "actual utilization" still has a lot of room for improvement. (2) Large electrochemical polarization / polarization voltage. Due to the limited electronic conductivity and ion diffusion / transport capabilities, NTP electrodes exhibit large voltage polarization under cycling or high-rate conditions, which affects the capacity utilization and cycle performance. This is the main bottleneck hindering its application in high-power or long-cycle applications. (3) Unstable long-cycle performance. In aqueous electrolytes, water molecules in Na + The unique solvated shell structure formed around it easily leads to structural damage and capacity decay of the active material during repeated insertion and extraction during charge and discharge. Therefore, although NTP is a very promising anode material in aqueous sodium-ion batteries, current technology cannot simultaneously achieve high reversible capacity, low polarization (low oxidation / reduction peak potential difference), and long cycle stability. Summary of the Invention

[0004] To address the aforementioned deficiencies in the existing technology, one objective of this invention is to provide a method for preparing a high-entropy doped sodium titanium phosphate battery anode material. This method involves incorporating various metal cations into the NaTi2(PO4)3NASICON framework to form a high-entropy structure. Metal ions of different radii exert a high-entropy effect on the lattice, thereby optimizing the Na... + Diffusion channels increase the number of available active sites within the crystal. This can improve the Na+ content. +Insertion / detachment efficiency, more active titanium sites participate in electrochemical reactions, thereby improving the initial reversible capacity of the material.

[0005] The second object of the present application is to provide a high-entropy doped sodium titanium phosphate battery negative electrode material, which introduces high-entropy metal cations to adjust the crystal electronic structure, thereby improving the electronic conductivity and Na + Ion migration rate, which is manifested as a decrease in the potential difference (ΔE p ) between the oxidation peak and the reduction peak in the cyclic voltammetry test, i.e., the electrochemical polarization is reduced.

[0006] The third object of the present application is to provide a high-entropy doped sodium titanium phosphate battery negative electrode material in an electrode sheet. The material can be used to prepare a high-performance negative electrode sheet, and the assembled full battery exhibits excellent electrochemical performance.

[0007] The present application is realized by the following technical solutions.

[0008] In one aspect of the present application, a preparation method of a high-entropy doped sodium titanium phosphate battery negative electrode material is provided, comprising the following steps: Step 1, preparation of active material a. Dissolve the titanium source, citric acid and sodium source in the solvent according to the mass ratio (100-110):(45-55):(20-30), add (17-21) parts of aluminum magnesium tin niobium metal oxide powder to the mixed solution, and then add (50-60) parts of phosphorus source to the mixed solution with aluminum magnesium tin niobium metal oxide, to prepare a precursor mixture; b. Anneal the precursor mixture under argon atmosphere, control the heating rate, form a uniform phase, and synthesize a high-entropy doped sodium titanium phosphate active material; Step 2, preparation of electrode slurry Mix the active material and the conductive agent according to the mass ratio (8~10):(1~3), grind to obtain a mixed powder, and finally mix the mixed powder with (1~3) parts of a binder polyvinylidene fluoride solution to obtain an electrode slurry sodium titanium phosphate battery negative electrode material.

[0009] According to an exemplary embodiment of the present application, the aluminum magnesium tin niobium metal oxide powder is aluminum oxide, magnesium oxide, tin oxide and niobium pentoxide powder according to the mass ratio (2-3):(2-3):(7-8):(6-7).

[0010] According to an exemplary embodiment of the present application, the titanium source is butyl titanate, titanium tetraisopropoxide or titanium dioxide; the sodium source is sodium acetate, sodium nitrate or sodium carbonate; and the phosphorus source is phosphoric acid, ammonium dihydrogen phosphate or triethyl phosphate.

[0011] According to an exemplary embodiment of the present application, the conductive agent is acetylene black, conductive carbon black, ketjen black or graphite.

[0012] According to an exemplary embodiment of the present application, the binder is a polyvinylidene fluoride (PVDF) solution, 5-20 wt% polyvinylidene fluoride (PVDF) is poured into 80-95 wt% N-methyl pyrrolidone (NMP) according to the mass ratio, and it is left for 30-40 minutes until the PVDF is completely dissolved.

[0013] According to an exemplary embodiment of the present application, the mixture A is dissolved in anhydrous ethanol to obtain a mixture A solution with a concentration of 0.10-1.00 mol·L -1 .

[0014] According to an exemplary embodiment of the present application, in step 2, the active substance is mixed and ground with the conductive agent for 20-30 min.

[0015] According to an exemplary embodiment of the present application, the precursor mixture is annealed at 600-800℃ for 3-8 hours under an argon atmosphere, and the temperature rising rate is controlled to be 5℃ min -1 .

[0016] Another aspect of the present application provides a high-entropy doped sodium titanium phosphate battery negative electrode material prepared by the method.

[0017] Still another aspect of the present application provides an application of the high-entropy doped sodium titanium phosphate battery negative electrode material in an electrode sheet, taking a nickel mesh as a current collector, coating the prepared electrode slurry sodium titanium phosphate battery negative electrode material on the nickel mesh, and drying the electrode sheet coated with the electrode slurry in a vacuum environment to prepare an electrode sheet.

[0018] According to an exemplary embodiment of the present application, the electrode sheet is dried in a vacuum environment with a vacuum degree of 0.08 ~ 0.10 MPa at 100-120℃ for 10-15 h.

[0019] The present application has the following beneficial effects due to the above technical solutions: 1. The negative electrode material of the present application takes NaTi2(PO4)3 as the main structure, introduces aluminum, magnesium, tin and niobium metal cations at the Ti site to form a high-entropy doping system, and forms the material NaTi 1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2The (PO4)3 is the structure of NASICON, and the structure can form a transfer channel of sodium ions due to the hollow, so as to realize stable cycle performance and enhanced rate capability, so that the material has good electrochemical performance.

[0020] 2. The present application introduces high-entropy doping to produce lattice micro-distortion after introducing multiple metal cations, so that Na + The diffusion path becomes more smooth, and the number of internal active sites is increased, so as to realize lattice regulation, configuration entropy stability and charge transport performance improvement. The sol-gel method can ensure uniform doping, so that more Ti sites participate in the reversible Na + insertion / deintercalation reaction, so as to obtain higher reversible capacity in the first cycle.

[0021] 3. Metal ions with different electronegativities have a synergistic regulation effect on the band structure of the NASICON framework, which improves the electronic conductivity and Na + migration rate of the material, so as to enhance the reaction kinetics. In the CV test, the voltage difference between the oxidation / reduction peaks is reduced, indicating that the polarization is reduced and the charge transfer impedance is obviously decreased.

[0022] 4. The high-entropy solid solution structure has a high mixing entropy effect, which can significantly inhibit the phase change tendency and enhance the chemical stability of the lattice to aqueous electrolyte. In the cycle process, the high-entropy framework can maintain the structure without collapse and pulverization, significantly slow down the contact failure between particles, and thus realize excellent cycle life.

[0023] 5. After the high-entropy doped sodium titanium phosphate material is coated on the pole piece and assembled into an aqueous sodium ion full cell, it can maintain stable capacity output and has excellent practicability and popularization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings described herein are used to provide further understanding of the present application, constitute a part of the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 It is a synthesis flow chart of high-entropy doped sodium titanium phosphate battery negative material; Figure 2 It is a CV comparison diagram of NaTi 1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2 (PO4)3 negative electrode in aqueous sodium ion battery system 1 A g -1 Current density under the cycle of 1, 2, 100, 500 cycles; Figure 3 It is a CV comparison diagram of undoped NTP negative electrode; Figure 4 It is a CV comparison diagram of NaTi1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2 (PO4)3 negative electrode 0.2 A g -1 charge-discharge cycle at current density; Figure 5 NaTi 1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2 (PO4)3 negative electrode rate performance; Figure 6 NaTi 1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2 (PO4)3 and NTP negative electrode at 1 A g -1 cycle performance comparison chart at current density. DETAILED DESCRIPTION

[0025] The application will be described in detail below with reference to the accompanying drawings and specific examples, which are used to explain the application, but not as a limitation of the application.

[0026] The embodiment of the application provides a high-entropy doped sodium titanium phosphate negative electrode material preparation method, Figure 1 As shown in the figure, the synthesis process schematic diagram of the high-entropy doped sodium titanium phosphate negative electrode material is as follows: Step 1, preparation of active material a. The titanium source (titanium butoxide, titanium tetraisopropoxide or titanium dioxide) is added to anhydrous ethanol and kept in a water area with a heating temperature of 40-60 DEG C, then citric acid is added to the titanium source solution to obtain a mixed solution A, the sodium source (sodium acetate, sodium nitrate or sodium carbonate) is dissolved in anhydrous ethanol and added to the mixed solution A to obtain a mixed solution B, wherein the mass ratio of the titanium source, citric acid and sodium source is (100-110):(45-55):(20-30), and the concentration of the mixed solution B is 0.10-1.00 mol·L -1 ; then (17-21) parts of aluminum magnesium tin niobium metal oxide powder are added to the mixed solution B, and constant stirring is carried out to ensure complete dissolution, to obtain a mixed solution C, and (50-60) parts of a phosphorus source (phosphoric acid, ammonium dihydrogen phosphate or triethyl phosphate) is added to the mixed solution C to prepare a precursor mixture.

[0027] The aluminum magnesium tin niobium metal oxide powder is aluminum oxide, magnesium oxide, tin oxide and niobium pentoxide powder in a mass ratio of (2-3):(2-3):(7-8):(6-7).

[0028] b. Annealing the obtained precursor mixture at 600-800℃ for 3-8 hours under argon atmosphere, with a heating rate of 5℃ / min -1 to ensure uniform temperature distribution and phase formation, and NaTi 1.2 Mg 0.2 Al 0.2 Sn 0.2 Nb 0.2 (PO4)3active material.

[0029] Step 2, preparation of electrode slurry The active material and conductive agent (acetylene black, conductive carbon black, Ketjen black or graphite) are mixed in a mass ratio of (8-10):(1-3), and placed in a mortar for grinding for 20-30 min to obtain a uniformly mixed powder. Then, the binder polyvinylidene fluoride (PVDF) is poured into an NMP solution, and left to stand for several minutes until the PVDF is completely dissolved. Finally, the mixed powder is added to the (1-3) parts of the binder polyvinylidene fluoride solution and uniformly mixed to prepare the electrode slurry.

[0030] The binder is a polyvinylidene fluoride (PVDF) solution, and 5-20 wt% polyvinylidene fluoride (PVDF) is poured into 80-95 wt% N-methyl pyrrolidone (NMP) according to the mass ratio, and left to stand for 30-40 min until the PVDF is completely dissolved.

[0031] In the existing aqueous sodium-ion battery system, the NTP negative electrode material has the problems of low initial reversible capacity, large potential difference between oxidation / reduction peaks, obvious electrochemical polarization and insufficient structural stability during the cycle process. This is mainly due to the inherent defects of the material, such as limited Na + diffusion channels, single crystal electronic structure and easy erosion of particles in the aqueous environment. Therefore, it is urgent to construct a more stable, more conductive and more conducive to Na + migration crystal framework to improve the initial capacity, reduce polarization and improve the long-term cycle retention rate. Based on this, the present application introduces a variety of metal oxides for high-entropy doping regulation, and realizes uniform dispersion of the precursor by a sol-gel method to improve the structural stability and electrochemical performance of the NTP material, so as to improve the initial reversible capacity, reduce the oxidation / reduction peak potential difference and enhance the cycle life.

[0032] In step 1 of the present application, a mixed solution A is formed by configuring butyl titanate, citric acid and sodium acetate in a specific mass ratio, and Al2O3, MgO, SnO2 and Nb2O5 metal oxide powders are added to the solution to uniformly disperse Al-Mg-Sn-Nb multi-metal ions at the molecular level and form a high-entropy precursor system, and then phosphoric acid is added to promote the nucleation of the NASICON framework, and finally a high-entropy doped sodium titanium phosphate framework is formed. The multi-metal cations with different radii and valence states cooperatively control the arrangement mode of TiO6 and PO4 tetrahedrons in the lattice, so that Na + The migration channel is enlarged and more continuous. The lattice optimization significantly improves the Na + insertion / extraction kinetics, directly improves the initial reversible capacity of the material, and the incorporation of high-valence elements is beneficial to improve the electronic conductivity of the material, thereby reducing the potential difference between the oxidation / reduction peaks, achieving lower electrochemical polarization.

[0033] The mixed cation framework formed by the multi-metal high-entropy doping can effectively inhibit lattice distortion and structure collapse during water-based cycling, so that the material still maintains the integrity of the NASICON framework under long cycling. The synergistic presence of Al-Mg-Sn-Nb improves the thermodynamic stability of the crystal, so that it can maintain stable Na + migration path in water-based environment and high rate conditions, thereby achieving excellent cycle stability.

[0034] Further, the material is made into a slurry with PVDF / NMP and uniformly coated on a current collector, and after vacuum drying, an electrode sheet is formed. In the water-based sodium ion battery full cell assembly, the electrode exhibits higher reversible capacity and stable long cycle performance, providing a material basis for the practical application of high-safety water-based sodium ion batteries.

[0035] The following will describe the preparation of the high-entropy doped sodium titanium phosphate battery negative electrode material of the present application through different embodiments.

[0036] Example 1: Step 1: 100 mL of butyl titanate, 50 g of citric acid and 25 g of sodium acetate are dissolved in anhydrous ethanol to obtain a mixed solution with a concentration of 0.5 mol·L -1 -1, and 18.5 g of aluminum magnesium tin niobium metal oxide powder is added, including 2 g of aluminum oxide powder, 3 g of magnesium oxide powder, 7.5 g of tin oxide powder and 6 g of niobium pentoxide powder. Stir constantly to ensure complete dissolution, then add 50 mL of phosphoric acid to the solution to prepare a precursor mixture.

[0037] Step 2: The mixture obtained is annealed at 700℃ for 5 hours under an argon atmosphere, with a controlled heating rate of 5℃ / min to ensure uniform temperature distribution and phase formation, and the active substance is synthesized.

[0038] Step 3: Preparation of slurry: The binder polyvinylidene fluoride (PVDF) solution was prepared by pouring 10 wt% polyvinylidene fluoride (PVDF) into 90 wt% N-methyl pyrrolidone (NMP) with a mass ratio, and standing for 30 minutes until the PVDF was completely dissolved.

[0039] The active material and acetylene black were mixed in a mass ratio of 8:1, respectively, and placed in a mortar to grind the material uniformly and into a very fine powder. Then the mixed powder was added to 1 part of the binder polyvinylidene fluoride (PVDF) solution, and stood for several minutes until the PVDF was completely dissolved, to prepare the electrode slurry.

[0040] Example 2: Step 1: Dissolve 105 mL of titanium tetraisopropoxide, 45 g of citric acid, and 30 g of sodium acetate in anhydrous ethanol to obtain a mixed solution with a concentration of 0.8 mol·L -1 -1, and then add 17.5 g of aluminum magnesium tin niobium metal oxide powder, 2.5 g of aluminum oxide powder, 2 g of magnesium oxide powder, 7 g of tin oxide powder, and 6 g of niobium pentoxide powder, and continuously stir to ensure complete dissolution. Then 55 mL of ammonium dihydrogen phosphate is added to the solution to prepare a precursor mixture.

[0041] Step 2: The resulting mixture was annealed at 650°C for 4 hours under an argon atmosphere, with a controlled heating rate of 5°C / min to ensure uniform temperature distribution and phase formation. The active material was synthesized.

[0042] Step 3: Preparation of slurry: The binder polyvinylidene fluoride (PVDF) solution was prepared by pouring 15 wt% polyvinylidene fluoride (PVDF) into 85 wt% N-methyl pyrrolidone (NMP) with a mass ratio, and standing for 35 minutes until the PVDF was completely dissolved.

[0043] The active material and conductive carbon black were mixed in a mass ratio of 9:3, respectively, and placed in a mortar to grind the material uniformly and into a very fine powder. Then the mixed powder was added to 3 parts of the binder polyvinylidene fluoride (PVDF) solution, and stood for several minutes until the PVDF was completely dissolved, to prepare the electrode slurry.

[0044] Example 3: Step 1: Dissolve 110 mL of titanium dioxide, 48 g of citric acid, and 26 g of sodium carbonate in anhydrous ethanol to obtain a mixed solution with a concentration of 0.10 mol·L -1Step 1 : Dissolve 100 mL of butyl titanate, 55 g of citric acid and 20 g of sodium nitrate in anhydrous ethanol to obtain a mixed solution with a concentration of 1.00 mol·L -1 of the mixture, add 20.5 g of aluminum magnesium tin niobium metal oxide powder, among which 3 g of aluminum oxide powder, 2.5 g of magnesium oxide powder, 8 g of tin oxide powder and 7 g of niobium pentoxide powder, constantly stir to ensure complete dissolution, then add 58 mL of phosphoric acid to the solution to make a precursor mixture.

[0045] Step 2: The obtained mixture was annealed at 800°C for 3 hours under argon atmosphere, with a heating rate of 5°C / min to ensure uniform temperature distribution and phase formation. Synthesize active material.

[0046] Step 3: Prepare the slurry: Prepare the binder polyvinylidene fluoride (PVDF) solution, pour 5 wt% polyvinylidene fluoride (PVDF) into 95 wt% N-methyl pyrrolidone (NMP) according to the mass ratio, stand for 40 minutes until the PVDF is completely dissolved.

[0047] Mix the active material and Ketjen black according to the mass ratio of 10:2.5 respectively, put them in a mortar and grind them into a uniform and very fine powder, then add the mixed powder to 2.5 parts of the binder polyvinylidene fluoride (PVDF) solution, stand for a few minutes until the PVDF is completely dissolved, to make the electrode slurry.

[0048] Example 4 Step 1 : Dissolve 100 mL of butyl titanate, 55 g of citric acid and 20 g of sodium nitrate in anhydrous ethanol to obtain a mixed solution with a concentration of 1.00 mol·L -1 of the mixture, add 18 aluminum magnesium tin niobium metal oxide powder, among which 2 g of aluminum oxide powder, 2 g of magnesium oxide powder, 7.5 g of tin oxide powder and 6.5 g of niobium pentoxide powder, constantly stir to ensure complete dissolution, then add 60 mL of triethyl phosphate to the solution to make a precursor mixture.

[0049] Step 2: The obtained mixture was annealed at 600°C for 8 hours under argon atmosphere, with a heating rate of 5°C / min to ensure uniform temperature distribution and phase formation. Synthesize active material.

[0050] Step 3: Prepare the slurry: Prepare the binder polyvinylidene fluoride (PVDF) solution, pour 20 wt% polyvinylidene fluoride (PVDF) into 80 wt% N-methyl pyrrolidone (NMP) according to the mass ratio, stand for 30 minutes until the PVDF is completely dissolved.

[0051] The active material and graphite were mixed at a mass ratio of 8.5:2 and ground in a mortar until the material was uniform and a very fine powder. The mixed powder was then added to 2 parts of a binder polyvinylidene fluoride (PVDF) solution and left to stand for several minutes until the PVDF was completely dissolved to make an electrode slurry.

[0052] Comparative example: Undoped sodium titanium phosphate NTP The same sol-gel route as in this invention is used for preparation, but high-entropy doped metal oxides such as aluminum, magnesium, tin, and niobium described in this invention are not added during the precursor preparation process. The specific steps are as follows: 100 mL of tetrabutyl titanate, 50 g of citric acid, and 25 g of sodium acetate were added to anhydrous ethanol and stirred until dissolved, yielding a concentration of 0.50 mol / L. -1 A transparent mixed solution was prepared; then 50 mL of phosphoric acid was added to the mixed solution to form a precursor sol, which was reacted in a constant temperature water bath and dried to obtain a gel precursor. The obtained precursor was subjected to solid-phase reaction at 600, 700 and 800 °C for 3, 5 and 7 h, respectively, and then cooled and ground to obtain undoped NaTi2(PO4)3 material. After the material was prepared, it was mixed with conductive agent acetylene black and binder PVDF at a mass ratio of 8:1:1 to prepare an electrode slurry, which was coated on a nickel mesh current collector and vacuum dried. This slurry was used as a comparative negative electrode material for subsequent electrochemical performance testing.

[0053] To verify the electrochemical performance of the NTPs prepared in Examples 1–4 and the high-entropy doped NTP anode materials with different compositions, constant current charge-discharge tests and cyclic voltammetry (CV) tests were performed on all the obtained materials. The specific test methods are as follows.

[0054] 1. Battery Assembly: Under aqueous conditions, using the prepared electrode sheet as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, a 5 mol L⁻¹ battery was assembled. -1 NaNO3 aqueous solution was used as the electrolyte to test the battery in a three-electrode system (working electrode, reference electrode, and counter electrode). The battery was allowed to stand for 6–12 hours before testing to ensure that the electrolyte was fully absorbed.

[0055] 2. Constant Current Charge-Discharge Test Method: The batteries of Examples 1–4 were subjected to constant current charge-discharge performance tests on an electrochemical testing instrument, with the voltage range controlled between -1.0 and -0.4 V (vs. SCE saturated calomel electrode). The initial reversible capacity was 0.2 A g. -1 The following measurements were taken; the cyclic stability was measured at 5 A g. -1 A 500-cycle test was conducted, and the capacity retention rate was recorded; the rate performance was measured at 0.2, 0.5, 1, 2, and 5 Ag. -1 Tests were conducted at different current densities.

[0056] 3. Cyclic voltammetry (CV) test method On an electrochemical workstation, cyclic voltammetry (CV) tests were performed at a scan rate of 2 mV s -1 The materials obtained in Examples 1-4 were subjected to cyclic voltammetry tests. The positions of the oxidation and reduction peaks were recorded, and the potential difference between the peaks was calculated to evaluate the reversibility and polarization degree of the electrode reaction of the materials.

[0057] Through the above charge-discharge and CV test methods, the initial reversible capacity, the potential difference between the peaks, and the cycle stability of the materials can be systematically evaluated, and the effectiveness of different doping schemes in improving performance can be verified. Table 1 shows the comparison of the electrochemical performance test results of the sodium titanium phosphate battery negative electrode materials of the present application and the comparative examples.

[0058] Table 1: Performance comparison of comparative examples and examples

[0059] As can be seen from the comparison of the above examples and comparative examples, the high-entropy doped sodium titanium phosphate negative electrode materials of the present application have an initial reversible capacity of not less than 91.1 mAh g -1 , a potential difference between the peaks of not more than 0.186 V, and a capacity retention rate of not less than 85.4 % after 500 cycles at 1 A g -1 . Compared with the undoped comparative example NTP, which has an initial reversible capacity of only 88.7 mAh g -1 , a potential difference between the peaks of 0.264 V, and a capacity retention rate of only 23.6 %, the materials of the present application show significant improvement in capacity, polarization, and cycle durability.

[0060] As can be seen from Table 1, the high-entropy doped sodium titanium phosphate negative electrode materials of the present application have high reversible capacity, small electrochemical polarization (potential difference between the peaks), and excellent cycle stability. The performance improvement is due to the lattice regulation effect introduced by the multi-metal high-entropy cooperative doping, the site disorder caused by the multi-cation promoting Na + diffusion, the local structure distortion reducing the electrochemical reaction energy barrier, enhancing the NTP skeleton stability, and improving the long cycle structure retention ability. The high-entropy doping strategy of the present application can effectively improve the technical problems of insufficient capacity, large polarization, and poor cycle stability of traditional NTP materials, and can significantly improve the comprehensive electrochemical performance of the negative electrode materials of aqueous sodium-ion batteries.

[0061] The following application examples further illustrate the application of the high-entropy doped sodium titanium phosphate battery negative electrode materials prepared by the present application in electrode sheets.

[0062] Application Example 1 Using a nickel mesh as the current collector, the sodium titanium phosphate battery negative electrode material prepared in Example 1 was coated onto the nickel mesh, and the electrode sheet coated with the electrode slurry was placed under a vacuum of [missing information]. The nickel mesh electrode sheet was dried at 100°C for 15 h in a vacuum environment of 0.10 MPa. The weight of the dried nickel mesh electrode sheet was recorded.

[0063] Application Example 2 Using a nickel mesh as the current collector, the sodium titanium phosphate battery negative electrode material prepared in Example 2 was coated onto the nickel mesh, and the electrode sheet coated with the electrode slurry was placed under a vacuum of [missing information]. The nickel mesh electrode was dried at 105°C for 14 h in a vacuum environment of 0.095 MPa to prepare the electrode sheet. The weight of the dried nickel mesh electrode sheet was recorded.

[0064] Application Example 3 Using a nickel mesh as the current collector, the sodium titanium phosphate battery negative electrode material prepared in Example 3 was coated onto the nickel mesh. The electrode sheet coated with the electrode slurry was dried at 110°C for 12 h in a vacuum environment with a vacuum degree of 0.09 MPa to form an electrode sheet. The weight of the dried nickel mesh electrode sheet was recorded.

[0065] Application Example 4 Using a nickel mesh as the current collector, the sodium titanium phosphate battery negative electrode material prepared in Example 4 was coated onto the nickel mesh. The electrode sheet coated with the electrode slurry was then placed under a vacuum of [missing information]. The nickel mesh electrode was dried at 120°C for 10 h in a vacuum environment of 0.08 MPa to prepare the electrode sheet. The weight of the dried nickel mesh electrode sheet was recorded.

[0066] The following shows the application effect of high-entropy doped sodium titanium phosphate battery anode material in aqueous sodium batteries.

[0067] High-entropy doped sodium titanium phosphate battery anode material at 5 mol L -1 Electrochemical performance tests were conducted in NaNO3 solution. Figure 2 shows the electrochemical performance of the high-entropy doped sodium titanium phosphate battery anode material of this invention in 1 A g. -1 A schematic diagram of the charge-discharge curves at current density. This figure shows the typical charge-discharge plateau and voltage variation trend of the material under constant current conditions. As can be seen from the figure, the material of this invention exhibits a stable and gentle voltage plateau in an aqueous sodium-ion battery system, with high overlap between the charge-discharge curves and small voltage hysteresis, indicating that the material has low polarization behavior and excellent reversible Na+. + Embedding / extraction performance.

[0068] Figure 3 Undoped sodium titanium phosphate (NTP) and the high-entropy doped material NaTi of this invention 1.2 Mg 0.2 Al 0.2 Sn0.2 Nb 0.2 (PO4)3in the cyclic voltammetry (CV) curves at a scan rate of 2 mV s - ¹. The oxidation and reduction peak positions of the two materials are shown in the figure, and it can be seen that the high-entropy doped material has a lower oxidation / reduction peak potential difference and a lower degree of electrochemical polarization.

[0069] Figure 4 is the rate performance curve of the high-entropy doped sodium titanium phosphate battery negative electrode material of the application. The figure shows the capacity retention rate change of the material under different current densities, verifying that the material of the application can still maintain high capacity output and stable electrochemical performance under high rate conditions.

[0070] Figure 5 is the discharge capacity and coulombic efficiency curve of the high-entropy doped material of the application cycled at 200 mA g -1 The current density. The figure is used to show the capacity retention rate and coulombic efficiency of the material during the small current density cycle process, to prove that it has good cycle stability.

[0071] Figure 6 is the performance comparison chart of the undoped NTP and the high-entropy doped material of the application cycled at 1 A g -1 The condition. The figure shows that the high-entropy doped material has higher capacity retention rate and more stable cycle curve, further verifying that it has high specific capacity and excellent cycle stability.

[0072] The application is not limited to the above embodiments, and based on the technical solutions disclosed in the application, those skilled in the art can make some substitutions and modifications to some technical features without creative labor, and these substitutions and modifications are within the protection scope of the application.

Claims

1. A method for preparing a high-entropy doped sodium titanium phosphate battery anode material, characterized in that, The method comprises the following steps: Step 1, preparation of active material a. Dissolve a titanium source, citric acid and a sodium source in a solvent according to a mass ratio of (100-110):(45-55):(20-30), add (17-21) parts of aluminum magnesium tin niobium metal oxide powder to the mixed solution, and then add (50-60) parts of a phosphorus source to the mixed solution added with the aluminum magnesium tin niobium metal oxide to prepare a precursor mixture; b. Anneal the precursor mixture under an argon atmosphere, control the heating rate, form a homogeneous phase, and synthesize a high-entropy doped sodium titanium phosphate active material; Step 2, preparation of electrode slurry Mix the high-entropy doped sodium titanium phosphate active material with a conductive agent according to a mass ratio of (8-10):(1-3), grind, obtain a mixed powder, and finally mix the mixed powder with (1-3) parts of a binder polyvinylidene fluoride solution to prepare an electrode slurry sodium titanium phosphate battery negative electrode material.

2. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1, wherein, The aluminum magnesium tin niobium metal oxide powder is aluminum oxide, magnesium oxide, tin oxide and niobium pentoxide powder according to a mass ratio of (2-3):(2-3):(7-8):(6-7).

3. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1 wherein, The titanium source is butyl titanate, titanium tetraisopropoxide or titanium dioxide; The sodium source is sodium acetate, sodium nitrate or sodium carbonate; The phosphorus source is phosphoric acid, ammonium dihydrogen phosphate or triethyl phosphate.

4. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1, wherein, The conductive agent is acetylene black, conductive carbon black, ketjen black or graphite.

5. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1 wherein, The binder is a polyvinylidene fluoride solution, 5-20 wt% polyvinylidene fluoride is poured into 80-95 wt% N-methyl pyrrolidone according to a mass ratio, and the mixture is left to stand for 30-40 minutes until the PVDF is completely dissolved.

6. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1 wherein, The mixture A was dissolved in absolute ethanol to obtain a solution of mixture A with a molar concentration of 0.10 - 1.0 mol L -1 -1. In step 2, the active material is mixed with the conductive agent and ground for 20-30 minutes.

7. The process for the preparation of high entropy doped sodium titanium phosphate battery anode material as claimed in claim 1 wherein, The precursor mixture is annealed at 600-800°C for 3-8 hours under argon atmosphere, with a heating rate of 5°C min -1 .

8. A high-entropy doped sodium titanium phosphate battery negative electrode material prepared by the method of any one of claims 1-7.

9. Use of the high-entropy doped sodium titanium phosphate battery anode material according to claim 8 in an electrode sheet, characterized in that With a nickel mesh as a current collector, the prepared electrode slurry sodium titanium phosphate battery negative electrode material is coated on the nickel mesh, the electrode slurry-coated electrode sheet is dried in a vacuum environment, and an electrode sheet is prepared.

10. Use of the high-entropy doped sodium titanium phosphate battery anode material according to claim 1 in an electrode sheet, characterized in that at a vacuum degree of 0.08 to Drying is performed at 100-120℃ for 10-15 h in a vacuum environment of 0.10 MPa.

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