A dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, its preparation method and application

Abstract

The present invention discloses a dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, its preparation method and application, belonging to the technical field of sodium-ion battery cathode materials. The chemical general formula of the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material is Na4V 1‑x MnTi x P3O 12‑y Cl y , 0.03 < x < 0.1, 0.05 < y < 0.20. The present invention realizes the synergistic regulation of the stability of the cation skeleton and the anion transport channel through the substitution of Ti at the V site and the partial substitution of Cl ‑ at the O site. Ti 4+ doping effectively inhibits the Jahn–Teller distortion caused by Mn 3+ and enhances the crystal structure stability; Cl ‑ doping expands the Na + migration channel, thereby significantly improving the transport kinetic performance of the material. The prepared cathode material exhibits a higher reversible specific capacity, excellent rate performance and significantly enhanced long cycle stability in sodium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery cathode materials, specifically relating to a dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] The ever-increasing global energy demand and the urgency of achieving "dual carbon" targets have jointly driven the urgent need for large-scale, low-cost, and highly safe electrochemical energy storage systems. Among various candidate technologies, sodium-ion batteries (SIBs) are widely considered one of the most promising large-scale stationary energy storage technologies to replace lithium-ion batteries due to the abundance, wide distribution, and low cost of sodium resources.

[0003] Among numerous cathode materials, NASICON-type materials have attracted considerable attention due to their stable three-dimensional framework structure and large sodium ion channels. Na3V2(PO4)3, as a typical NASICON-type material, possesses high ionic conductivity and theoretical specific capacity; however, the toxicity, environmental unfriendliness, and price volatility of vanadium severely limit its commercialization prospects. Therefore, developing "low-vanadium" or "vanadium-free" NASICON materials has become a current research hotspot.

[0004] By partially replacing vanadium with low-cost, environmentally friendly manganese, the resulting Na4VMn(PO4)3 material exhibits a considerable specific capacity (≈110 mAh / g) and a higher average operating voltage (≈3.5 V). However, in Mn-based materials, Mn... 3+ The resulting Jahn-Teller distortion leads to structural deformation and capacity decay. Furthermore, its inherently low electronic conductivity limits rate performance. Existing techniques improve performance through single-element doping, but it is difficult to simultaneously address the dual requirements of suppressing crystal structure distortion and improving ion diffusion kinetics. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, its preparation method, and its application, through Ti... 4+ / Cl - Dual-site co-doping, by simultaneously regulating both cation and anion sites, stabilizes the crystal structure and expands the sodium ion transport channels, thereby improving the discharge capacity, rate performance, and cycle performance of Na4VMn(PO4)3 materials.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material, wherein the general chemical formula of the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material is Na₄V₂. 1-x MnTi x P3O 12-y Cl y Where 0.03 ≤ x ≤ 0.1, 0.05 ≤ y ≤ 0.20.

[0008] Furthermore, 0.03 ≤ x ≤ 0.08, 0.10 ≤ y ≤ 0.20; further optimized, x=0.05, y=0.1.

[0009] In a second aspect, the present invention provides a method for preparing the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, comprising the following steps:

[0010] (1) According to the general chemical formula Na4V 1-x MnTi x P3O 12-y Cl y The raw materials were weighed according to the stoichiometric ratio. The vanadium source, manganese source, sodium source, phosphorus source, titanium source, chlorine source, and chelating agent (which also serves as a carbon source) were dissolved in water. The mixture was heated and stirred at 65~75℃ for 0.8~1.2h, and then stirred at 80~85℃ to form a gel. The gel was then dried to obtain the electrode material precursor.

[0011] (2) The electrode material precursor in step (1) is heated to 750~850℃ for 6~10h at a rate of 4~6℃ / min under an inert atmosphere, and then cooled to room temperature to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material.

[0012] Furthermore, the vanadium source is an inorganic vanadium salt or vanadium oxide; the manganese source is an inorganic manganese salt or manganese oxide; the sodium source is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, and sodium pyrophosphate; the phosphorus source is a phosphate or hydrogen phosphate; and the chelating agent is one or more of glucose, citric acid, and ascorbic acid.

[0013] Furthermore, the vanadium source is V2O5; the manganese source is MnCO3; the phosphorus source is NH4H2PO4; and the chelating agent is glucose.

[0014] Furthermore, the titanium source is titanium dioxide; the chlorine source is sodium chloride.

[0015] Furthermore, the molar ratio of the chelating agent to the manganese element in the manganese source is 1.5~2.0:1.

[0016] Furthermore, the drying method is vacuum drying or thermal radiation drying.

[0017] In a third aspect, the present invention provides the application of the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material in the preparation of sodium-ion batteries; specifically, it includes the following application methods:

[0018] (1) Used to prepare positive electrode material for sodium-ion batteries, and the material is used as the positive electrode active material for sodium-ion batteries;

[0019] (2) Used for the positive electrode of sodium-ion batteries;

[0020] (3) Used as cathode material for high-power or long-life sodium-ion batteries.

[0021] Further, the application method (1) includes the following steps: mixing the dual-site doped Na4VMn(PO4)3 sodium-ion battery positive electrode material, conductive agent and binder in a mass ratio of 7~9:1:1, adding an appropriate amount of N-methylpyrrolidone (NMP) to make a slurry, coating it on an aluminum foil current collector, and drying it to obtain a positive electrode sheet.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] (1) This invention innovatively employs Ti / Cl for dual-site synergistic doping. Ti 4+ (Ionic radius and V) 3+ The near-substitution of V sites can act as a "pillar," enhancing lattice stability and suppressing Mn during cycling. 3+ Jahn-Teller distortion.

[0024] (2) In this invention, Cl - (ionic radius greater than O) 2- () partially replaces O in PO4 2- This can moderately expand the sodium ion migration channels in the NASICON structure and improve kinetic performance.

[0025] (3) The Ti / Cl co-doped Na4VMn(PO4)3 cathode material prepared by the present invention exhibits higher reversible specific capacity, excellent rate performance and significantly enhanced long cycle life, which is superior to undoped or single-doped materials.

[0026] (4) The sol-gel method combined with high-temperature solid-phase reaction used in this invention is mature, simple, has low equipment requirements, and uses low-cost and readily available raw materials. Attached Figure Description

[0027] Figure 1X-ray diffraction (XRD) spectra of NVMP-TiCl prepared in Example 1 and NVMP prepared in Comparative Example 1;

[0028] Figure 2 The image shows a scanning electron microscope (SEM) image of the NVMP-TiCl prepared in Example 1.

[0029] Figure 3 Charge-discharge curves of CR2032 coin cells prepared for NVMP-TiCl, NVMP, and NVMP-Ti at a 0.5C rate;

[0030] Figure 4 Rate performance of CR2032 coin cells prepared for NVMP-TiCl, NVMP, and NVMP-Ti at different rates;

[0031] Figure 5 Long-term cycling curves of CR2032 coin cells prepared for NVMP-TiCl, NVMP, and NVMP-Ti at 5C rate. Detailed Implementation

[0032] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0034] Example 1

[0035] Preparation of chemical formula Na4V 0.95 MnTi 0.05 P3O 11.9 Cl 0.1 The dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material (i.e., x=0.05, y=0.1) is as follows:

[0036] (1) Weigh 1.9 mmol V2O5, 4 mmol MnCO3, 8 mmol Na2CO3, 12 mmol NH4H2PO4, 0.2 mmol TiO2, and 0.4 mmol NaCl according to the stoichiometric ratio, and weigh 6 mmol of glucose at the same time; place all the above raw materials in a beaker, add 50 ml of deionized water, and stir magnetically in a 70℃ water bath for 1 h; place the beaker on a temperature-controlled magnetic stirrer and continue stirring at 80℃ until the mixture forms a uniform gel; transfer the gel to a vacuum drying oven and dry at 110℃ for 12 h to obtain the electrode material precursor;

[0037] (2) The electrode material precursor was placed in a corundum boat, put into a tube furnace, and high-purity argon was introduced as a protective gas. The temperature was raised to 800°C at a rate of 5°C / min, and calcined at 800°C for 8 hours. After calcination, the product was naturally cooled to room temperature, taken out, and ground to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material, labeled as NVMP-TiCl.

[0038] Example 2

[0039] Preparation of chemical formula Na4V 0.97 MnTi 0.03 P3O 11.85 Cl 0.15 The dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material (i.e., x=0.03, y=0.15) is as follows:

[0040] (1) Weigh 1.94 mmol V2O5, 4 mmol MnCO3, 8 mmol Na2CO3, 12 mmol NH4H2PO4, 0.12 mmol TiO2, and 0.6 mmol NaCl according to the stoichiometric ratio, and weigh 8 mmol of glucose at the same time; place all the above raw materials in a beaker, add 50 ml of deionized water, and stir magnetically in a water bath at 70℃ for 1 h; place the beaker on a temperature-controlled magnetic stirrer and continue stirring at 80℃ until the mixture forms a uniform gel; transfer the gel to a vacuum drying oven and dry at 110℃ for 12 h to obtain the electrode material precursor;

[0041] (2) The electrode material precursor was placed in a corundum boat, put into a tube furnace, and high-purity argon was introduced as a protective gas. The temperature was raised to 750°C at a rate of 5°C / min, and calcined at 750°C for 10 hours. After calcination, the product was naturally cooled to room temperature, taken out, and ground to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material.

[0042] Example 3

[0043] Preparation of chemical formula Na4V 0.92 MnTi 0.08 P3O 11.8 Cl 0.2 The dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material (i.e., x=0.08, y=0.2) is as follows:

[0044] (1) Weigh 1.84 mmol V2O5, 4 mmol MnCO3, 8 mmol Na2CO3, 12 mmol NH4H2PO4, 0.32 mmol TiO2, and 0.8 mmol NaCl according to the stoichiometric ratio, and weigh 6 mmol of glucose at the same time; place all the above raw materials in a beaker, add 50 ml of deionized water, and stir magnetically in a 70℃ water bath for 1 h; place the beaker on a temperature-controlled magnetic stirrer and continue stirring at 80℃ until the mixture forms a uniform gel; transfer the gel to a vacuum drying oven and dry at 110℃ for 12 h to obtain the electrode material precursor;

[0045] (2) The electrode material precursor was placed in a corundum boat, put into a tube furnace, and high-purity argon was introduced as a protective gas. The temperature was raised to 800°C at a rate of 5°C / min, and calcined at 800°C for 8 hours. After calcination, the product was naturally cooled to room temperature, taken out, and ground to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material.

[0046] Comparative Example 1

[0047] The preparation of Na4VMn(PO4)3 sodium-ion battery cathode material is as follows:

[0048] (1) Weigh 2 mmol V2O5, 4 mmol MnCO3, 8 mmol Na2CO3, and 12 mmol NH4H2PO4 according to the stoichiometric ratio, and weigh 6 mmol of glucose at the same time; place all the above raw materials in a beaker, add 50 ml of deionized water, and stir magnetically in a 70℃ water bath for 1 h; place the beaker on a temperature-controlled magnetic stirrer and continue stirring at 80℃ until the mixture forms a uniform gel; transfer the gel to a vacuum drying oven and dry at 110℃ for 12 h to obtain the electrode material precursor;

[0049] (2) The electrode material precursor was placed in a corundum boat, put into a tube furnace, and high-purity argon was introduced as a protective gas. The temperature was raised to 800°C at a rate of 5°C / min, and calcined at 800°C for 8 hours. After calcination, the product was naturally cooled to room temperature, taken out, and ground to obtain Na4VMn(PO4)3 sodium ion battery cathode material, labeled as NVMP.

[0050] Comparative Example 2

[0051] Preparation of Ti 4+ Doped Na4V 0.95 MnTi 0.05 The (PO4)3 sodium-ion battery cathode material is specifically:

[0052] (1) Weigh 1.9 mmol V2O5, 4 mmol MnCO3, 8 mmol Na2CO3, 12 mmol NH4H2PO4, and 0.2 mmol TiO2 according to the stoichiometric ratio, and weigh 6 mmol of glucose at the same time; place all the above raw materials in a beaker, add 50 ml of deionized water, and stir magnetically in a 70℃ water bath for 1 h; place the beaker on a temperature-controlled magnetic stirrer and continue stirring at 80℃ until the mixture forms a uniform gel; transfer the gel to a vacuum drying oven and dry at 110℃ for 12 h to obtain the electrode material precursor;

[0053] (2) The electrode material precursor was placed in a corundum boat and placed in a tube furnace. High-purity argon gas was introduced as a protective gas, and the temperature was raised to 800°C at a rate of 5°C / min. The furnace was then calcined at 800°C for 8 hours. After calcination, the furnace was allowed to cool naturally to room temperature. The product was then removed, ground, and Ti was obtained. 4+ Doped Na4V 0.95 MnTi 0.05 (PO4)3 sodium-ion battery cathode material, labeled as NVMP-Ti.

[0054] Performance testing

[0055] (1) The XRD patterns of NVMP-TiCl prepared in Example 1 and NVMP prepared in Comparative Example 1 are shown below. Figure 1 As shown, by Figure 1 As can be seen, Example 1 matches the typical NASICON structure Na4VMn(PO4)3. Compared with undoped NVMP, the NVMP-TiCl diffraction peak positions are slightly shifted, indicating that the lattice parameters have changed and Ti and Cl have been successfully doped into the lattice, resulting in structural tuning.

[0056] (2) SEM image of NVMP-TiCl prepared in Example 1 is shown below. Figure 2 As shown in the figure, nanoparticles are uniformly distributed on the surface of NVMP-TiCl. These nanoparticles cover larger two-dimensional nanosheets and together form a hierarchical network structure with three-dimensional interconnection, which is beneficial for electron / ion transport and electrolyte wetting.

[0057] (3) Electrochemical performance testing

[0058] The active materials prepared in Examples 1-3 and Comparative Examples 1-2 (dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material, undoped Na4VMn(PO4)3 material, Ti) were compared with those prepared in Examples 1-3 and Comparative Examples 1-2. 4+ Doped Na₄VMn(PO₄)₃ material was mixed with acetylene black and PVDF binder at a mass ratio of 8:1:1, and an appropriate amount of NMP solvent was added. The mixture was stirred for 30 min to prepare a uniform slurry. The slurry was uniformly coated onto aluminum foil and vacuum dried at 120℃ for 12 h. After rolling, it was cut into 12 mm diameter discs to serve as the positive electrode. In an argon-filled glove box, a CR2032 coin cell was assembled using a sodium metal sheet as the negative electrode, a glass fiber membrane as the separator, and 1.0 M NaPF₆ / DIGLYME as the electrolyte.

[0059] 1) The charge-discharge performance of the CR2032 coin cells prepared according to the above (Examples 1-3, Comparative Examples 1-2 sodium-ion battery cathode materials) at a 0.5C rate was tested. The initial discharge specific capacity data are shown in Table 1. The charge-discharge curves of the CR2032 coin cells prepared by NVMP-TiCl, NVMP, and NVMP-Ti at a 0.5C rate are shown in Table 1. Figure 3 As shown; by Figure 3 It can be seen that the CR2032 coin cell prepared by NVMP-TiCl in Example 1 has an initial discharge specific capacity of about 105 mAh / g, which is higher than that of Comparative Example 1 (NVMP, 92.4 mAh / g) and Comparative Example 2 (NVMP-Ti, 101 mAh / g).

[0060] 2) The rate performance of the CR2032 coin cells prepared using the above-mentioned (Examples 1-3, Comparative Examples 1-2 sodium-ion battery cathode materials) at different rates (0.5C, 1C, 2C, 5C, 10C, 30C) was tested. The capacity retention at 30C is shown in Table 1. The rate curves of the CR2032 coin cells prepared using NVMP-TiCl, NVMP, and NVMP-Ti at different rates (0.5C, 1C, 2C, 5C, 10C, 30C) are shown in Table 1. Figure 4 As can be seen, the CR2032 coin cell prepared by NVMP-TiCl in Example 1 exhibits the highest capacity retention. In particular, at a high rate of 30C, its discharge capacity can still be maintained at about 88 mAh / g, which is significantly better than the two comparative examples.

[0061] 3) The long-term cycling performance of the CR2032 coin cells prepared in the above-mentioned examples (Examples 1-3, Comparative Examples 1-2 sodium-ion battery cathode materials) at 5C rate was tested. The capacity retention after 500 cycles is shown in Table 1. The long-term cycling curves of the CR2032 coin cells prepared by NVMP-TiCl, NVMP, and NVMP-Ti at 5C rate are shown in Table 1. Figure 5 As shown in the figure, the CR2032 coin cell prepared by NVMP-TiCl in Example 1 has a capacity retention rate as high as 94%, while the capacity retention rate of Comparative Example 1 after 500 cycles under the same conditions is less than 85%, and the capacity retention rate of Comparative Example 2 after 500 cycles is about 91%. This indicates that Ti / Cl dual-site doping has a synergistic effect in improving long-term cycling stability.

[0062] Table 1 Electrochemical properties of Na4VMn(PO4)3 materials

[0063]

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Those skilled in the art can make changes and modifications to the described embodiments without departing from the spirit and scope of the present invention, and all such changes and modifications should be covered within the protection scope defined by the claims of the present invention.

Claims

1. A dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material, characterized in that, The chemical formula of the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material is Na4V 1-x MnTi x P3O 12-y Cl y Where 0.03 ≤ x ≤ 0.08, 0.10 ≤ y ≤ 0.20; The preparation method of the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material is as follows: (1) According to the general chemical formula Na4V 1-x MnTi x P3O 12-y Cl y The raw materials were weighed according to the stoichiometric ratio. The vanadium source, manganese source, sodium source, phosphorus source, titanium source, chlorine source and chelating agent were dissolved in water. The mixture was heated and stirred at 65~75℃ for 0.8~1.2h, and then stirred at 80~85℃ to form a gel. The gel was dried to obtain the electrode material precursor. (2) The electrode material precursor in step (1) is heated to 750-850℃ for 6-10h at a rate of 4-6℃ / min under an inert atmosphere, and then cooled to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material. The molar ratio of the chelating agent to the manganese element in the manganese source is 1.5~2.0:1; The chelating agent is one or more of glucose, citric acid, and ascorbic acid.

2. A method for preparing the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material according to claim 1, characterized in that, Includes the following steps: (1) According to the general chemical formula Na4V 1-x MnTi x P3O 12-y Cl y The raw materials were weighed according to the stoichiometric ratio. The vanadium source, manganese source, sodium source, phosphorus source, titanium source, chlorine source and chelating agent were dissolved in water. The mixture was heated and stirred at 65~75℃ for 0.8~1.2h, and then stirred at 80~85℃ to form a gel. The gel was dried to obtain the electrode material precursor. (2) The electrode material precursor in step (1) is heated to 750-850℃ for 6-10h at a rate of 4-6℃ / min under an inert atmosphere, and then cooled to obtain the double-site doped Na4VMn(PO4)3 sodium ion battery cathode material. The molar ratio of the chelating agent to the manganese element in the manganese source is 1.5~2.0:

1.

3. The method for preparing the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material according to claim 2, characterized in that, The vanadium source is an inorganic vanadium salt or vanadium oxide; the manganese source is an inorganic manganese salt or manganese oxide; the sodium source is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, and sodium pyrophosphate; and the phosphorus source is a phosphate or hydrogen phosphate.

4. The method for preparing the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material according to claim 3, characterized in that, The vanadium source is V2O5; the manganese source is MnCO3; the phosphorus source is NH4H2PO4; and the chelating agent is glucose.

5. The method for preparing the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material according to claim 2, characterized in that, The titanium source is titanium dioxide; the chlorine source is sodium chloride.

6. The method for preparing the dual-site doped Na₄VMn(PO₄)₃ sodium-ion battery cathode material according to claim 2, characterized in that, The drying method is vacuum drying or thermal radiation drying.

7. The application of the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material according to claim 1 or the dual-site doped Na4VMn(PO4)3 sodium-ion battery cathode material prepared by the method according to any one of claims 2 to 6 in the preparation of sodium-ion batteries.

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