A modified preparation method of a sodium-ion battery sodium manganese titanium phosphate positive electrode material

Abstract

The application belongs to the field of sodium ion batteries, and discloses a modified preparation method of a sodium titanate manganese phosphate positive electrode material of a sodium ion battery, which comprises the following steps: S1, weighing a metal ion chelating agent to prepare a solution I; S2, weighing a manganese source, a titanium source and a sodium source, and dissolving them in the solution I to obtain a solution II; S3, dissolving a Li, Mg or Ca source material in the solution II to obtain a solution III; weighing a phosphate to prepare a solution IV; S4, dropping the solution IV into the solution III drop by drop; and S5, stirring under an oil bath condition, and then drying and calcining, so that the modified sodium titanate manganese phosphate positive electrode material is obtained. According to the application, the low-orbital energy level elements Li, Mg or Ca are introduced into the sodium titanate manganese phosphate Na3MnTi(PO4)3 positive electrode material, and the preparation method is controlled, so that the modified sodium titanate manganese phosphate positive electrode material is obtained, the electronic configuration of Li(Mg, Ca)-O-Mn is constructed, the inhibition of the anti-site defect is realized, and the improvement of the electrochemical performance is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, and more specifically, relates to a method for modifying and preparing sodium titanium manganese phosphate cathode material for sodium-ion batteries. The modified sodium titanium manganese phosphate cathode material obtained has the characteristics of suppressing antisite defects and improving crystal structure, and can achieve the optimization and improvement of the electrochemical performance of sodium titanium manganese phosphate cathode material. Background Technology

[0002] To adapt to the global trend of green energy and low-carbon economic development, sodium-ion batteries (SIBs) have attracted increasing attention due to their abundant natural sodium resources and low cost. The cathode material is a crucial component of SIBs and largely determines their electrochemical performance. Therefore, it is essential to develop cathode materials with fast kinetics and high energy density to meet this growing demand. Sodium superionic conductor (NASICON) phosphates have become promising cathode materials for SIBs due to their high safety and good structural stability. Sodium titanium manganese phosphate (Na3MnTi(PO4)3), as a typical NASICON cathode material, exhibits high kinetics and high energy density within a voltage range of 1.5-4.3V, accompanied by Mn... 4+ / 3+ (≈4.0V vs Na+ / Na), Mn 3+ / 2+ (≈3.6V vs Na+ / Na) and Ti 4+ / 3+ A redox pair of approximately 2.1V vs. Na+ / Na allows for multi-electron transfer, resulting in a yield of 178 mAh g. -1 High theoretical specific capacity. Na3MnTi(PO4)3 (NMTP) is a three-dimensional open-frame structure formed by the shared corners of PO4 tetrahedra and MO6 (M represents the transition metal element, i.e., Ti and Mn elements) octahedra. + Located at two independent Na sites, namely (Na1, with crystal plane orientation 6b) and (Na2, with crystal plane orientation 18e), they have different Na... + Coordination environment, and Na during charging and discharging. + Ions tend to be reversibly extracted from and inserted into Na2 sites.

[0003] However, several challenges remain to be solved in Na3MnTi(PO4)3 cathode materials. Due to the significant number of Na vacancies within the Na3MnTi(PO4)3 framework, Mn... 2+ These vacant positions are easily occupied, forming a reverse position defect. Mn 2+ Overoccupancy not only hinders the Na2-Na1-Na2 ​​diffusion path, but also increases the Na... + It creates a diffusion barrier and also damages crystal integrity, while affecting electronic conductivity and ion diffusion capacity, ultimately leading to severe voltage hysteresis and rapid capacity loss in NMTPs. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a modified preparation method for sodium-titanium manganese phosphate (Na3MnTi(PO4)3) cathode materials for sodium-ion batteries. This method involves introducing low-orbital-level elements such as Li, Mg, or Ca into the Na3MnTi(PO4)3 cathode material, while simultaneously controlling the overall process design and key reaction conditions (e.g., the amount of low-orbital-level metal elements introduced and the amount of metal ion chelating agent). This yields a modified Na3MnTi(PO4)3 cathode material with a Li(Mg,Ca)-O-Mn electronic configuration, suppressing antisite defects and improving electrochemical performance. The invention is convenient to operate, easy to industrialize, and the prepared modified Na3MnTi(PO4)3 cathode material is easily controllable, exhibiting excellent cycle performance, rate performance, and structural stability.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a modified sodium manganese titanium phosphate cathode material is provided, characterized in that the molar ratio of Mn to Ti in the modified sodium manganese titanium phosphate cathode material is 1:1, and the preparation method includes the following steps:

[0006] S1. Weigh the metal ion chelating agent and dissolve it in anhydrous ethanol to obtain solution I; wherein, the ratio of the amount of the metal ion chelating agent in solution I to the total amount of the two transition metal elements Mn and Ti in the target modified sodium manganese titanium phosphate cathode material product is (0.5~3):2.

[0007] S2. Weigh out manganese source and titanium source according to the Mn and Ti elements in the target modified sodium titanium manganese phosphate cathode material product, and weigh out sodium source at the same time, so that the molar ratio of Na element provided by sodium source to Mn element provided by manganese source is greater than 3:1 and less than or equal to 3.05:1; dissolve sodium source, manganese source and titanium source in solution I to obtain solution II;

[0008] S3. Using any one of Li, Mg, or Ca as the low-orbit energy level metal element, weigh the low-orbit energy level metal element source material according to a molar ratio of the low-orbit energy level metal element to the Na element provided by the sodium source in solution II of 0.01 to 0.05:3; dissolve the low-orbit energy level metal element source material in solution II to obtain solution III;

[0009] Meanwhile, phosphate is weighed and dissolved in deionized water to obtain solution IV; wherein, the molar ratio of phosphate ions contained in the phosphate to the Na element provided by the sodium source in solution II is 1:1;

[0010] S4. Add solution IV dropwise into solution III and stir thoroughly to obtain solution V;

[0011] S5. Stir solution V in an oil bath, allow it to react fully, dry it, and then calcine it at a temperature of 600–750°C for 4–6 hours to obtain the target modified sodium titanium manganese phosphate cathode material.

[0012] As a further preferred embodiment of the present invention, in step S1, the metal ion chelating agent is selected from tartaric acid, anhydrous citric acid, disodium ethylenediaminetetraacetate, and gluconic acid.

[0013] In step S2, the sodium source is selected from sodium acetate and sodium nitrate; the manganese source is selected from manganese acetate and manganese nitrate; and the titanium source is selected from tetrabutyl titanate and isopropyl titanate.

[0014] In step S3, the low-orbit energy level metal element source material is selected from lithium acetate, lithium nitrate, magnesium acetate, magnesium nitrate, calcium acetate, and calcium nitrate; the phosphate is ammonium dihydrogen phosphate.

[0015] As a further preferred embodiment of the present invention, in step S3, the concentration of phosphate in solution IV is 0.345 g / mL;

[0016] In step S4, the drip rate of the droplet infusion is 1 to 5 ml / min; the droplet infusion is preferably performed using a peristaltic pump; preferably, the drip rate of the peristaltic pump is 2 ml / min.

[0017] As a further preferred embodiment of the present invention, in step S5, the oil bath is specifically an oil bath with a temperature of 70-85°C, preferably an oil bath with a temperature of 80°C;

[0018] The drying temperature used is 100-120°C, preferably 110°C; preferably, the drying is carried out using a forced-air drying oven.

[0019] The calcination was carried out under an Ar atmosphere at a temperature of 650°C for 6–8 hours.

[0020] As a further preferred embodiment of the present invention, in step S1, the ratio of the amount of metal ion chelating agent in solution I to the total amount of the two transition metal elements, Mn and Ti, in the target modified sodium titanium manganese phosphate cathode material product is 1:1.

[0021] As a further preferred embodiment of the present invention, in step S3, the molar ratio of the low orbital energy level metal element to the Na element provided by the sodium source in solution II is 0.03:3.

[0022] As a further preferred embodiment of the present invention, in step S4, the thorough stirring specifically involves stirring for 20 to 40 minutes after all solution IV has been added to solution III, with the stirring speed being 200 to 500 r / min.

[0023] According to another aspect of the present invention, the present invention provides a modified sodium titanium manganese phosphate cathode material obtained by the above preparation method.

[0024] According to another aspect of the present invention, the present invention provides the application of the above-mentioned modified sodium titanium manganese phosphate cathode material as a cathode material in sodium-ion batteries.

[0025] Compared with the prior art, the present invention introduces a low-orbit energy level Li into the sodium titanium manganese phosphate Na3MnTi(PO4)3 cathode material through the above-described technical solution. + Mg 2+ Ca 2+ Replace Na + This study constructs a Li(Mg, Ca)-O-Mn configuration to suppress antisite defects, providing a novel modification method and corresponding modified materials for sodium superionic conductor (NASICON) phosphate cathode materials. Due to the large energy difference between Li 2s (Mg 3s, Ca 4s) and O 2p orbitals, hybridization is restricted. This strengthens the dp orbital hybridization between Mn 3d and O 2p, promoting more charge transfer from Mn to O, thus forming stronger Mn-O bonds and hindering Mn from forming a hybrid. 2+ Migration to the Na site. This is due to strong dp orbital hybridization, which suppresses Mn migration. 2+ Over-occupancy reduces reverse site defects, which is directly reflected in the effective control of voltage hysteresis and the improvement of electrochemical performance.

[0026] Specifically, the present invention can achieve the following beneficial effects:

[0027] (1) The method of this invention is the first to introduce low-orbit energy level elements Li, Mg or Ca into sodium titanium manganese phosphate Na3MnTi(PO4)3 cathode material. The modification method specifically involves dissolving various metal source materials (i.e., manganese source, titanium source, sodium source, low-orbit energy level metal element source materials; for example, metal salt compounds of the corresponding metal elements can be used as source materials) in anhydrous ethanol, coordinating and binding through a chelating agent, and then obtaining site-substituted sodium titanium manganese phosphate cathode material by high-temperature calcination. No strong acid or strong base solvents are used in the whole process, so the method of this invention is convenient to operate and easy to scale up for industrial production.

[0028] The method of this invention involves adjusting the amount of metal ion chelating agent in solution I and the amount of total transition metal elements in the system (i.e., N) Ti +N Mn ; where N Ti N represents the amount of substance of Ti in the system. Mn The amount of substance of Mn element in the system, N Ti =N MnThe ratio of sodium (Na) to manganese (Mn) and titanium (Ti) in solution II is controlled at (0.5–3):2 (e.g., 1:2). This avoids insufficient chelating of metal elements due to insufficient chelating agent, or acidic solution due to excessive chelating agent, which is detrimental to grain growth and sol formation. Furthermore, the method of this invention controls the molar ratio of Na provided by the sodium source to Mn provided by the manganese source and Ti provided by the titanium source in solution II to be greater than 3:1:1 and less than or equal to 3.05:1:1 (of course, the molar ratio of Mn to Ti is 1:1). That is, the sodium source is controlled to be more abundant than the manganese and titanium sources, thus reducing sodium salt loss during subsequent high-temperature calcination. Calcination at 600–750°C for 4–6 hours avoids high-temperature energy consumption and ensures crystallinity during material growth.

[0029] (2) The low-orbit energy level Li, Mg or Ca doped modified sodium titanium manganese phosphate cathode material prepared by this invention can achieve Na site doping inside the crystal, which can suppress Mn 2+ Offside migration ensures crystal integrity while simultaneously increasing ion and electron diffusion rates and optimizing reaction kinetics. (See below) Figure 4 As shown in the example, compared with unmodified NMTP, the modified sodium titanium manganese phosphate obtained based on the method of the present invention has higher cycle stability, indicating that the structural stability of the modified sodium titanium manganese phosphate material is also improved.

[0030] (3) This invention modifies sodium titanium manganese phosphate cathode material by doping with low-orbital Li, Mg, or Ca to construct a Li(Mg, Ca)-O-Mn electronic configuration, which promotes strong orbital hybridization between Mn 3d and O 2p, thereby strengthening Mn-O bonding and enhancing Mn electron density. 2+ By creating an off-site migration barrier, suppressing anti-site defects, reducing voltage hysteresis, and improving diffusion kinetics and structural stability, the high-rate, long-cycle electrochemical performance of sodium titanium manganese phosphate is enhanced.

[0031] (4) This invention, starting from the electronic configuration level, comprehensively strengthens the overall material configuration, making it more suitable for high current and long cycle (5C, 500 cycles, as described below). Figure 4 The actual usage conditions of the example.

[0032] In summary, the modification method of this invention is convenient to operate and easy to scale up for production. The low-orbit energy level Li(Mg, Ca) doped modified sodium titanium manganese phosphate cathode material prepared is easy to control, has good structural stability, and excellent rate performance and cycle performance. Attached Figure Description

[0033] Figure 1 The image shows a comparison of the XRD patterns of the modified sodium manganese titanium phosphate cathode material (NMTP-Li3) prepared in Example 1 of this invention and the unmodified sodium manganese titanium phosphate cathode material (NMTP) prepared in Comparative Example 1.

[0034] Figure 2 The images show a SEM comparison between the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of this invention and the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1; wherein, Figure 2 (a) in the text corresponds to the modified sodium titanium manganese phosphate cathode material prepared in Example 1. Figure 2 (b) in the figure corresponds to the unmodified sodium titanium manganese phosphate cathode material prepared in proportion 1. The scale bars in the figure all represent 5 μm.

[0035] Figure 3 The figures show the charge-discharge curves of the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1 and the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of this invention; wherein, Figure 3 (a) corresponds to the unmodified sodium titanium manganese phosphate cathode material prepared in proportion 1. Figure 3 (b) in the example corresponds to the modified sodium titanium manganese phosphate cathode material prepared in Example 1.

[0036] Figure 4 This is a comparison chart of the cycle performance of the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of the present invention and the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1.

[0037] Figure 5 The first and second charge-discharge curves are shown for the sodium manganese titanium phosphate cathode material prepared by the excess citric acid metal chelating agent obtained in Comparative Example 4 of this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] Example 1

[0040] A method for preparing modified sodium-titanium manganese sodium phosphate cathode material for sodium-ion batteries. The molar ratio of transition metal elements Ti and Mn in the target modified sodium-titanium manganese sodium phosphate cathode material is 1:1 (in this embodiment, the amount of both Ti and Mn in the target modified sodium-titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this embodiment are as follows:

[0041] Step 1: Weigh anhydrous citric acid and dissolve it in 80 ml of anhydrous ethanol according to the total transition metal element molar ratio of 1:1 with the target sodium-ion battery titanium manganese sodium phosphate cathode material (i.e., weigh 2 mmol of anhydrous citric acid and dissolve it in 80 ml of anhydrous ethanol) to obtain solution I.

[0042] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0043] Step 3: Weigh lithium acetate according to a molar ratio of 0.03:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0044] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0045] Step 5: After stirring solution III evenly, slowly add solution IV dropwise to it at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0046] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir. After the reaction is complete, dry it in a 110℃ forced-air drying oven.

[0047] Step 7: Grind the dried material into powder, place it in a tube furnace and calcine it at high temperature of 650℃ for 6 hours in an Ar atmosphere to obtain low-energy Li-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage), denoted as NMTP-Li3 sample.

[0048] The low-orbital-level Li-doped modified sodium titanium manganese phosphate cathode material prepared in this embodiment achieves selective site doping of Li within the crystal, constructing a Li-O-Mn electronic configuration. Due to the energy difference between the Li 2s and O 2p orbitals, stronger orbital hybridization between Mn3d and O 2p is promoted, enhancing Mn-O bonding and improving Mn efficiency. 2+ The migration barrier suppresses antisite defects, perfects the crystal structure, and thus comprehensively improves the electrochemical performance.

[0049] Example 2

[0050] A method for preparing a modified sodium-ion battery titanium manganese sodium phosphate cathode material. The target modified sodium-ion battery titanium manganese sodium phosphate cathode material has a molar ratio of transition metal elements Ti and Mn of 1:1 (in this embodiment, the amount of both Ti and Mn in the target modified sodium-ion battery titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this embodiment are as follows:

[0051] Step 1: Weigh anhydrous citric acid according to a 1:1 molar ratio of total transition metal elements in the target sodium-ion battery titanium manganese sodium phosphate cathode material and dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0052] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0053] Step 3: Weigh magnesium acetate according to a molar ratio of 0.02:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0054] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0055] Step 5: After thoroughly stirring solution III, add solution IV dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0056] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir. After the reaction is complete, dry it in a 110℃ forced-air drying oven.

[0057] Step 7: Grind the dried material into powder, place it in a tube furnace for high-temperature calcination at 650°C for 6 hours in an Ar atmosphere, and obtain low-orbit energy level Mg-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage).

[0058] The low-orbital-level Mg-doped modified sodium titanium manganese phosphate cathode material prepared in this embodiment achieves selective site doping of Mg within the crystal, constructing a Mg-O-Mn electronic configuration. Due to the energy difference between the Mg 3s and O 2p orbitals, stronger orbital hybridization between Mn 3d and O 2p is promoted, enhancing Mn-O bonding and increasing Mn concentration. 2+ The migration barrier suppresses antisite defects, perfects the crystal structure, and thus comprehensively improves the electrochemical performance.

[0059] Example 3

[0060] A method for preparing a modified sodium-ion battery titanium manganese sodium phosphate cathode material. The target modified sodium-ion battery titanium manganese sodium phosphate cathode material has a molar ratio of transition metal elements Ti and Mn of 1:1 (in this embodiment, the amount of both Ti and Mn in the target modified sodium-ion battery titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this embodiment are as follows:

[0061] Step 1: Weigh anhydrous citric acid according to a 1:1 molar ratio of total transition metal elements in the target sodium-ion battery titanium manganese sodium phosphate cathode material and dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0062] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0063] Step 3: Weigh calcium acetate according to a molar ratio of 0.02:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0064] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0065] Step 5: After thoroughly stirring solution III, add solution IV dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0066] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir to react, then dry it in a 110℃ forced-air drying oven;

[0067] Step 7: Grind the dried material into powder, place it in a tube furnace and calcine at high temperature of 650℃ for 6 hours in an Ar atmosphere to obtain low-energy Ca-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then stored in a glove box).

[0068] The low-orbital-level Ca-doped modified sodium titanium manganese phosphate cathode material prepared in this embodiment achieves selective Ca doping within the crystal, constructing a Ca-O-Mn electronic configuration. Due to the energy difference between the Ca 4s and O 2p orbitals, stronger orbital hybridization between Mn 3d and O 2p is promoted, enhancing Mn-O bonding and increasing Mn concentration. 2+ The migration barrier suppresses antisite defects, perfects the crystal structure, and thus comprehensively improves the electrochemical performance.

[0069] Example 4

[0070] A method for preparing modified sodium-titanium manganese sodium phosphate cathode material for sodium-ion batteries. The molar ratio of transition metal elements Ti and Mn in the target modified sodium-titanium manganese sodium phosphate cathode material is 1:1 (in this embodiment, the amount of both Ti and Mn in the target modified sodium-titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this embodiment are as follows:

[0071] Step 1: Weigh anhydrous citric acid and dissolve it in 80 ml of anhydrous ethanol according to the total transition metal element molar ratio of 1:1 with the target sodium-ion battery titanium manganese sodium phosphate cathode material (i.e., weigh 2 mmol of anhydrous citric acid and dissolve it in 80 ml of anhydrous ethanol) to obtain solution I.

[0072] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0073] Step 3: Weigh lithium acetate according to a molar ratio of 0.05:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0074] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0075] Step 5: After stirring solution III evenly, slowly add solution IV dropwise to it at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0076] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir. After the reaction is complete, dry it in a 110℃ forced-air drying oven.

[0077] Step 7: Grind the dried material into powder, place it in a tube furnace and calcine it at high temperature of 650℃ for 6 hours in an Ar atmosphere to obtain low-energy Li-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage), denoted as NMTP-Li5 sample.

[0078] The low-orbital-level Li-doped modified sodium titanium manganese phosphate cathode material prepared in this embodiment achieves selective site doping of Li within the crystal, constructing a Li-O-Mn electronic configuration. Due to the energy difference between the Li 2s and O 2p orbitals, stronger orbital hybridization between Mn3d and O 2p is promoted, enhancing Mn-O bonding and improving Mn efficiency. 2+ The migration barrier suppresses antisite defects, and the electrochemical performance is improved (of course, the improvement effect is not as good as that of 0.03 mol doping in Example 1).

[0079] Comparative Example 1

[0080] This comparative example synthesizes an unmodified sodium titanium manganese phosphate cathode material (the molar ratio of transition metal elements Ti and Mn in the sodium titanium manganese phosphate cathode material is also equal to 1:1; in this comparative example, the amount of Ti and Mn in the target unmodified sodium-ion battery sodium titanium manganese phosphate cathode material is 1 mmol each), including the following steps:

[0081] Step 1: Weigh anhydrous citric acid according to a 1:1 molar ratio of total transition metal elements in the target sodium-ion battery titanium manganese sodium phosphate cathode material and dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0082] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0083] Step 3: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution III;

[0084] Step 4: After thoroughly stirring solution II, add solution III dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution IV;

[0085] Step 5: Place solution IV in an 80°C constant temperature oil bath and stir to react, then dry it in a 110°C forced-air drying oven;

[0086] Step 6: Grind the dried material into powder, place it in a tube furnace and calcine at high temperature of 650℃ for 6 hours in an Ar atmosphere to obtain unmodified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then stored in a glove box), and denoted as NMTP sample.

[0087] Comparative Example 2

[0088] A method for preparing a modified sodium-ion battery titanium manganese sodium phosphate cathode material. The target modified sodium-ion battery titanium manganese sodium phosphate cathode material has a molar ratio of transition metal elements Ti and Mn of 1:1 (in this comparative example, the amount of both Ti and Mn in the target modified sodium-ion battery titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this comparative example are as follows:

[0089] Step 1: Weigh anhydrous citric acid according to a 1:1 molar ratio of total transition metal elements in the target sodium-ion battery titanium manganese sodium phosphate cathode material and dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0090] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0091] Step 3: Weigh lithium acetate according to a molar ratio of 0.1:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0092] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0093] Step 5: After thoroughly stirring solution III, add solution IV dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0094] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir to react, then dry it in a 110℃ forced-air drying oven;

[0095] Step 7: Grind the dried material into powder, place it in a tube furnace and calcine at high temperature of 650℃ for 6 hours in an Ar atmosphere to obtain low-energy Li-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage).

[0096] The low-orbital-level Li-doped modified sodium titanium manganese phosphate cathode material prepared in this comparative example achieves selective Li doping within the crystal, constructing a Li-O-Mn electronic configuration. Due to the energy difference between the Li 2s and O 2p orbitals, stronger orbital hybridization between Mn 3d and O 2p is promoted, enhancing Mn-O bonding. However, excessive doping leads to severe lattice disruption, hindering Na... + The diffusion capacity of the material reduces its electrochemical performance.

[0097] Comparative Example 3

[0098] A method for preparing a modified sodium-ion battery titanium manganese sodium phosphate cathode material. The target modified sodium-ion battery titanium manganese sodium phosphate cathode material has a molar ratio of transition metal elements Ti and Mn of 1:1 (in this comparative example, the amount of both Ti and Mn in the target modified sodium-ion battery titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this comparative example are as follows:

[0099] Step 1: Weigh anhydrous citric acid according to a 1:1 molar ratio of total transition metal elements in the target sodium-ion battery titanium manganese sodium phosphate cathode material and dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0100] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0101] Step 3: Weigh calcium acetate according to a molar ratio of 0.03:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0102] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0103] Step 5: After thoroughly stirring solution III, add solution IV dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0104] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir to react, then dry it in a 110℃ forced-air drying oven;

[0105] Step 7: Grind the dried material into powder, place it in a tube furnace for high-temperature calcination at 750°C for 8 hours in an Ar atmosphere, and obtain low-energy Ca-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage).

[0106] The low-orbital-level Ca-doped modified sodium titanium manganese phosphate cathode material prepared in this comparative example achieves selective Ca doping within the crystal, constructing a Ca-O-Mn electronic configuration. Due to the energy difference between the Ca 4s and O 2p orbitals, stronger orbital hybridization between Mn 3d and O 2p is promoted, enhancing the Mn-O bond. However, due to excessively long calcination time, grain growth fracture occurs, leading to a decrease in electrochemical performance.

[0107] Comparative Example 4

[0108] A method for preparing a modified sodium-ion battery titanium manganese sodium phosphate cathode material. The target modified sodium-ion battery titanium manganese sodium phosphate cathode material has a molar ratio of transition metal elements Ti and Mn of 1:1 (in this comparative example, the amount of both Ti and Mn in the target modified sodium-ion battery titanium manganese sodium phosphate cathode material is 1 mmol). The steps of the preparation method described in this comparative example are as follows:

[0109] Step 1: Weigh anhydrous citric acid according to the total transition metal element molar ratio of 5:2 to sodium titanium manganese sodium phosphate cathode material of the target sodium-ion battery, dissolve it in 80 ml of anhydrous ethanol to obtain solution I;

[0110] Step 2: Weigh 3.02 mmol of sodium acetate, and weigh manganese acetate and isopropyl titanate in a molar ratio of 3.02:1:1 and dissolve them in solution I to obtain solution II;

[0111] Step 3: Weigh magnesium acetate according to a molar ratio of 0.03:3 with sodium acetate and dissolve it in solution II to obtain solution III;

[0112] Step 4: Weigh out ammonium dihydrogen phosphate at a molar ratio of 1:1 with sodium acetate and dissolve it in 10 ml of deionized water to obtain solution IV;

[0113] Step 5: After thoroughly stirring solution III, add solution IV dropwise at a rate of 2 ml / min using a peristaltic pump to obtain solution V;

[0114] Step 6: Place solution V in an 80℃ constant temperature oil bath and stir to react, then dry it in a 110℃ forced-air drying oven;

[0115] Step 7: Grind the dried material into powder, place it in a tube furnace for high-temperature calcination at 750°C for 8 hours in an Ar atmosphere, and obtain low-energy Mg-doped modified sodium titanium manganese phosphate cathode material (which can be naturally cooled to room temperature and then transferred to a glove box for storage).

[0116] The low-orbital-level Mg-doped modified sodium titanium manganese phosphate cathode material prepared in this comparative example achieves selective Mg doping within the crystal, constructing a Mg-O-Mn electronic configuration. Due to the energy difference between the Mg 3s and O 2p orbitals, stronger orbital hybridization between Mn 3d and O 2p is promoted, enhancing Mn-O bonding. However, due to excessive citric acid as a metal chelating agent, the solution is acidic, which is not conducive to the bonding of metal elements, resulting in an incomplete crystal structure of the synthesized sodium titanium manganese phosphate, weakened sodium storage performance of the host material, and reduced electrochemical performance.

[0117] Performance testing:

[0118] Figure 1This is an XRD comparison image of the modified sodium manganese titanium phosphate cathode material (NMTP-Li3) prepared in Example 1 of this invention and the unmodified sodium manganese titanium phosphate cathode material (NMTP) prepared in Comparative Example 1. Figure 1 It can be seen that the peak shape of the modified sodium titanium manganese phosphate cathode material is no different from that of the unmodified sample.

[0119] Figure 2 This is a SEM comparison image of the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of this invention and the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1. Figure 2 It can be seen that both the modified and unmodified samples exhibit micron-sized polyhedral particles with almost no change in morphology.

[0120] Figure 3 The figures show the charge-discharge curves of the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of this invention and the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1, within a current density range of 0.1C and a voltage range of 1.5-4.3V. Figure 3 It can be seen that the discharge capacity is improved (compared to the unmodified sample prepared in Comparative Example 1, whose discharge specific capacity is 154 mAh g). -1 The discharge specific capacity of the modified sample obtained based on the method of this invention was increased to 163 mAh g. -1 The voltage hysteresis at 4.0V and 2.6V was significantly suppressed, effectively alleviating the problem of voltage hysteresis.

[0121] Figure 4 This is a comparison chart of the cycle performance of the modified sodium titanium manganese phosphate cathode material prepared in Example 1 of this invention and the unmodified sodium titanium manganese phosphate cathode material prepared in Comparative Example 1 under 5C conditions and a voltage range of 1.5-4.3V. Figure 4 It can be seen that the modified sodium titanium manganese phosphate cathode material prepared in Example 1 has improved cycle stability and discharge specific capacity, and can avoid rapid capacity loss (as analyzed above, this is attributed to the more perfect crystal structure).

[0122] Figure 5 The charge-discharge curves of the sodium manganese titanium phosphate cathode material with excess citric acid added, prepared in Comparative Example 4 of this invention, are shown in the range of 0.1C current density and 1.5-4.3V voltage. Figure 5 It can be seen that the discharge capacity is greatly reduced, which is attributed to the excessive metal chelating agent destroying the crystal structure.

[0123] The above embodiments are merely examples. For instance, in addition to Ar atmosphere, other protective atmospheres (such as nitrogen or other inert gases) can be used for calcination.

[0124] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a modified sodium manganese titanium phosphate cathode material, characterized in that, The modified sodium manganese titanium phosphate cathode material has a molar ratio of Mn to Ti of 1:1, and the preparation method includes the following steps: S1. Weigh the metal ion chelating agent and dissolve it in anhydrous ethanol to obtain solution I; wherein, the ratio of the amount of metal ion chelating agent in solution I to the total amount of the two transition metal elements Mn and Ti in the target modified sodium manganese titanium phosphate cathode material product is (0.5~3):

2. S2. Weigh out manganese source and titanium source according to the Mn and Ti elements in the target modified sodium titanium manganese phosphate cathode material product, and weigh out sodium source at the same time, so that the molar ratio of Na element provided by sodium source to Mn element provided by manganese source is greater than 3:1 and less than or equal to 3.05:1; dissolve sodium source, manganese source and titanium source in solution I to obtain solution II; S3. Using any one of Li, Mg, or Ca as the low-orbit energy level metal element, weigh the low-orbit energy level metal element source material according to a molar ratio of the low-orbit energy level metal element to the Na element provided by the sodium source in solution II of 0.01~0.05:3; dissolve the low-orbit energy level metal element source material in solution II to obtain solution III; Meanwhile, phosphate is weighed and dissolved in deionized water to obtain solution IV; wherein, the molar ratio of phosphate ions contained in the phosphate to the Na element provided by the sodium source in solution II is 1:1; S4. Add solution IV dropwise into solution III and stir thoroughly to obtain solution V; S5. Stir solution V in an oil bath, allow it to react fully, dry it, and then calcine it at a temperature of 600–750°C for 4–6 hours to obtain the target modified sodium titanium manganese phosphate cathode material.

2. The preparation method according to claim 1, characterized in that, In step S1, the metal ion chelating agent is selected from tartaric acid, anhydrous citric acid, disodium ethylenediaminetetraacetate, and gluconic acid; In step S2, the sodium source is selected from sodium acetate and sodium nitrate; the manganese source is selected from manganese acetate and manganese nitrate; and the titanium source is selected from tetrabutyl titanate and isopropyl titanate. In step S3, the low-orbit energy level metal element source material is selected from lithium acetate, lithium nitrate, magnesium acetate, magnesium nitrate, calcium acetate, and calcium nitrate; the phosphate is ammonium dihydrogen phosphate.

3. The preparation method according to claim 1, characterized in that, In step S3, the concentration of phosphate in solution IV is 0.345 g / mL; In step S4, the dripping rate is 1~5 ml / min.

4. The preparation method according to claim 3, characterized in that, In step S4, the dripping is performed using a peristaltic pump; the dripping rate of the peristaltic pump is 2 ml / min.

5. The preparation method according to claim 1, characterized in that, In step S5, the oil bath is specifically an oil bath with a temperature of 70~85℃; The drying temperature used in the process is 100~120℃; The calcination was carried out under an Ar atmosphere at a temperature of 650°C.

6. The preparation method according to claim 5, characterized in that, In step S5, the oil bath is specifically an oil bath with a temperature of 80°C; The drying temperature used is 110°C; the drying is carried out using a forced-air drying oven.

7. The preparation method according to claim 1, characterized in that, In step S1, the ratio of the amount of metal ion chelating agent in solution I to the total amount of the two transition metal elements, Mn and Ti, in the target modified sodium manganese titanium phosphate cathode material product is 1:

1.

8. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of the low-orbit energy level metal element to the Na element provided by the sodium source in solution II is 0.03:

3.

9. The preparation method according to claim 1, characterized in that, In step S4, the thorough stirring specifically means stirring for 20 to 40 minutes after all solution IV has been added to solution III, with a stirring speed of 200 to 500 r / min.

10. A modified sodium titanium manganese phosphate cathode material is obtained by the preparation method according to any one of claims 1-9.

11. The application of the modified sodium titanium manganese phosphate cathode material as described in claim 10 as a cathode material in sodium-ion batteries.

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