Sodium vanadium phosphate-based composite positive electrode material and preparation method and application thereof
By employing a synergistic modification strategy of metal ion doping and rare earth phosphate/carbon layer coating, the problems of low electronic conductivity and interface instability in sodium vanadium phosphate cathode materials were solved, resulting in a sodium-ion battery cathode material with high rate performance and long cycle life.
Patent Information
- Application Number
- CN202511677787.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-02-10
AI Technical Summary
Existing sodium vanadium phosphate cathode materials have low electronic conductivity, poor sodium ion diffusion performance, and suffer from interfacial side reactions and structural instability during long-term charge and discharge processes, which limits their application in sodium-ion batteries.
A synergistic modification strategy of metal ion doping and rare earth phosphate/carbon layer coating was adopted to form a core-shell structured sodium vanadium phosphate-based composite cathode material. By strengthening MO bonds and constructing composite interfaces, the electronic conductivity and sodium ion diffusion rate were improved, and the interface stability was enhanced.
This significantly improves the high-rate performance and long cycle life of the material, meeting the practical application requirements of sodium-ion batteries.
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Figure CN121506904A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion battery materials technology, specifically to a sodium vanadium phosphate-based composite cathode material, its preparation method, and its application. Background Technology
[0002] Renewable energy sources such as solar and wind power inherently possess intermittency and instability, posing a significant challenge to the power grid. Energy storage technology can effectively smooth out the drastic fluctuations in photovoltaic and wind power, achieving peak shaving and valley filling, playing a crucial role in ensuring national energy security and improving energy efficiency. Lithium-ion batteries are widely used in new energy vehicles, portable electronic devices, and energy storage due to their high energy density and long cycle life. However, the extremely uneven distribution of global lithium resources and their low abundance in the Earth's crust have resulted in cost and resource constraints that severely hinder the rapid development of lithium-ion battery systems. In contrast, sodium-ion batteries, with their abundant sodium resources and low cost, show broad application prospects in large-scale energy storage.
[0003] The performance of sodium-ion batteries is limited by the cathode material, making the development of suitable cathode materials crucial for their large-scale application. Sodium vanadium phosphate (Na3V2(PO4)3), as a typical polyanionic cathode material, possesses a three-dimensional open framework structure, high theoretical specific capacity and voltage plateau, exhibiting excellent structural stability and sodium-ion diffusion kinetics. However, the strong covalent bonding of its phosphate groups results in extremely low intrinsic electronic conductivity, severely limiting its rate performance and reversible capacity. Furthermore, during long-term charge-discharge cycles, interfacial side reactions between the electrode material and the electrolyte, as well as the structural stability issues of the material itself, lead to rapid capacity decay. These problems have become key bottlenecks restricting the commercial application of sodium vanadium phosphate cathode materials. Existing technologies for modifying sodium vanadium phosphate mainly include nano-sizing, carbon coating, and metal ion doping. None of these single modification strategies can simultaneously address the dual challenges of bulk conductivity and interfacial stability, resulting in overall material performance that fails to meet practical application requirements. Therefore, developing multi-dimensional modification technologies with synergistic enhancement effects has become an urgent need to overcome the performance bottleneck of sodium vanadium phosphate. Summary of the Invention
[0004] The purpose of this invention is to provide a universal synergistic modification strategy of ion doping and rare earth phosphate / carbon layer coating, which can be widely applied to NASICON-type vanadium-based phosphate cathode materials to simultaneously solve problems such as electronic / ionic conduction, interface stability and structural robustness.
[0005] To solve the above-mentioned technical problems, a sodium vanadium phosphate-based composite cathode material is invented; to achieve the above objectives, the technical solution of this invention is as follows:
[0006] The general chemical formula of the sodium vanadium phosphate-based composite cathode material is Na3V. 2-2x M x (PO4) 3-x / C@xREPO4, where M is the doped metal element; RE is the rare earth element; 0.001≤x≤0.5; C is amorphous carbon.
[0007] The composite cathode material has a core-shell structure, with the core being a NASICON-type crystal doped with M ions and the outer shell being a composite coating layer composed of rare earth phosphate and amorphous carbon.
[0008] The preparation method of the sodium vanadium phosphate-based composite cathode material specifically includes the following steps:
[0009] 1) Weigh out the sodium source, vanadium source, doped metal source, phosphorus source, rare earth salt and carbon source according to the stoichiometric ratio of the general chemical formula; the mass of the carbon source is 10 to 30% of the total mass of the sodium source, vanadium source, doped metal source, phosphorus source and rare earth salt.
[0010] 2) Add the vanadium source, doped metal source, rare earth salt and carbon source from step 1) to deionized water in sequence, and heat and stir at 30-100℃ for 0.5-2 hours to form a mixed solution;
[0011] 3) Add sodium source and phosphorus source to the mixed solution obtained in step 2), heat and stir at 60-120℃ for 2-10h to form sol, and then dry in an oven at 80-150℃ for 1-20h to obtain gel precursor;
[0012] 4) Grind the gel precursor obtained in step 3), and then pre-sinter and sinter it at high temperature under an inert atmosphere. After cooling, the sodium vanadium phosphate-based composite cathode material Na3V is obtained. 2-2x M x (PO4) 3-x / C@xREPO4.
[0013] Optionally, in step 1), the sodium source is one or more of sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, or sodium carbonate; the vanadium source is one or more of ammonium metavanadate, ammonium vanadate, or vanadium pentoxide; the doped metal source is one or more of the chloride, acetate, oxalate, nitrate, or carbonate of the doped metal; the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, or phosphoric acid; the rare earth salt is one or more of rare earth nitrate, carbonate, or chloride; and the carbon source is one or more of citric acid, oxalic acid, ascorbic acid, glucose, or sucrose.
[0014] Optionally, in step 1), the molar ratio of sodium source, vanadium source, doped metal source, phosphorus source, and rare earth salt is 3-3.5:1-2.5:0.001-0.5:2.5-3.5:0.001-0.05.
[0015] Optionally, in step 3), the atmosphere used during sintering is one or more of argon, nitrogen, nitrogen containing 5% hydrogen, and argon containing 5% hydrogen; the pre-sintering temperature is 200-500℃, and the time is 2-10h; the high-temperature sintering temperature is 600-1000℃, and the time is 4-20h.
[0016] Prepared Na3V 2-2x M x (PO4) 3-x Using C@xREPO4 material as the positive electrode, a sodium metal sheet as the negative electrode, a glass fiber membrane as the separator, and 1M NaClO4 dissolved in a 1:1 volume ratio of propylene carbonate (PC) and ethylene carbonate (EC) mixed solvent (containing 5wt% fluoroethylene carbonate, FEC) as the electrolyte, and aluminum foil as the current collector, a CR2032 coin cell sodium-ion battery was assembled in an inert atmosphere inside a glove box.
[0017] Beneficial effects of the present invention
[0018] The positive electrode material of this invention has the composition of Na3V. 2-2x M x (PO4) 3-x This invention provides a sodium vanadium phosphate-based composite material synergistically modified by metal ion doping and rare earth phosphate / carbon layer coating, its preparation method, and its application. The synthesis method of this invention is simple, and the synthesized Na3V... 2-2x M x (PO4) 3-x In the / C@xREPO4 material, trivalent metal ions (M) are doped into the V sites, forming stronger MO bonds to stabilize the crystal structure and broaden the sodium ion diffusion channels. During sintering, a rare-earth phosphate nanocoating layer is generated in situ, forming a composite interface with the carbon network, synergistically improving the material's conductivity and interfacial stability. Through the synergistic effect of bulk doping and rare-earth phosphate / carbon layer surface coating, this material simultaneously improves electronic conductivity, sodium ion diffusion rate, and interfacial stability, thus achieving excellent high-rate performance and long cycle life. It has significant application value and promising prospects in energy storage and other fields. Attached Figure Description
[0019] Figure 1 Na3V in Embodiment 1 of the present invention 1.98 Al 0.01 (PO4) 2.99X-ray diffraction patterns of / C@1%LaPO4 material and Na3V2(PO4)3 / C material in Comparative Example 1.
[0020] Figure 2 The Na3V prepared in Example 1 of this invention 1.98 Al 0.01 (PO4) 2.99 Transmission electron microscopy image of / C@1%LaPO4 material.
[0021] Figure 3 Na3V in Embodiment 1 of the present invention 1.98 Al 0.01 (PO4) 2.99 Rate performance curves of / C@1%LaPO4 material and Na3V2(PO4)3 / C material in Comparative Example 1 as the positive electrode of sodium-ion battery.
[0022] Figure 4 The Na3V prepared in Example 1 of this invention 1.98 Al 0.01 (PO4) 2.99 Cycling performance curve of / C@1%LaPO4 material as a sodium-ion battery cathode at 1C rate. Detailed Implementation
[0023] The present invention will be described in detail below through specific embodiments.
[0024] Example 1
[0025] (1) Weigh the raw materials sodium acetate, ammonium metavanadate, aluminum nitrate nonahydrate, lanthanum nitrate hexahydrate, and ammonium dihydrogen phosphate in a molar ratio of 3:1.98:0.01:0.01:3. Citric acid is selected as the complexing agent and carbon source. First, add ammonium metavanadate, aluminum nitrate nonahydrate, lanthanum nitrate hexahydrate, and citric acid to 100 mL of deionized water and stir at 80 °C for 1 h to obtain a blue homogeneous solution. Add sodium acetate and ammonium dihydrogen phosphate to the above solution and stir in an 80 °C water bath for 5 h to form a sol. Dry the sol in an oven at 120 °C for 12 h to form a gel precursor.
[0026] (2) The gel precursor was ground and placed in a tube furnace for pre-sintering at 350°C for 4 hours under an argon atmosphere, followed by sintering at 750°C for 8 hours. After cooling, the sintered product was ground to obtain the final product Na3V. 1.98 Al 0.01 (PO4) 2.99 / C@1% LaPO4 cathode material. The XRD patterns of the materials obtained in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown, the transmission electron microscope (TEM) image of the material obtained in Example 1 is as follows. Figure 2 As shown.
[0027] Example 2
[0028] (1) Weigh the raw materials sodium acetate, ammonium metavanadate, aluminum nitrate nonahydrate, lanthanum nitrate hexahydrate, and ammonium dihydrogen phosphate in a molar ratio of 3:1.96:0.02:0.02:3. Citric acid was selected as the complexing agent and carbon source. First, ammonium metavanadate, aluminum nitrate nonahydrate, lanthanum nitrate hexahydrate, and citric acid were added to 100 mL of deionized water and stirred at 80 °C for 1 h to obtain a blue homogeneous solution. Sodium acetate and ammonium dihydrogen phosphate were added to the above solution and stirred in an 80 °C water bath for 5 h to form a sol. The sol was dried in an oven at 120 °C for 12 h to form a gel precursor.
[0029] (2) The gel precursor was ground and placed in a tube furnace for pre-sintering at 350°C for 4 hours under a nitrogen atmosphere, followed by sintering at 700°C for 10 hours. After cooling, the sintered product was ground to obtain the final product Na3V. 1.96 Al 0.02 (PO4) 2.98 / C@2% LaPO4 cathode material.
[0030] Example 3
[0031] (1) Weigh the raw materials sodium acetate, vanadium pentoxide, aluminum nitrate nonahydrate, cerium nitrate hexahydrate, and ammonium dihydrogen phosphate in a molar ratio of 3:1.98:0.01:0.01:3. Citric acid is selected as the complexing agent and carbon source. First, dissolve vanadium pentoxide, aluminum nitrate nonahydrate, cerium nitrate hexahydrate, and citric acid in deionized water to obtain a blue homogeneous solution. Add sodium acetate and ammonium dihydrogen phosphate to the above solution and stir in an 80°C water bath for 5 hours to form a sol. Dry the sol in a 120°C oven for 12 hours to form a gel precursor.
[0032] (2) The gel precursor was ground and placed in a tube furnace for pre-sintering at 350°C for 4 hours under an argon atmosphere, followed by sintering at 750°C for 10 hours. After natural cooling, the sintered product was ground to obtain the final product Na3V. 1.98 Al 0.01 (PO4) 2.99 / C@1%CePO4 cathode material.
[0033] Comparative Example 1
[0034] (1) Weigh sodium acetate, ammonium metavanadate, and ammonium dihydrogen phosphate in a molar ratio of 3:2:3, using citric acid as the carbon source. First, dissolve ammonium metavanadate and citric acid in deionized water. Add sodium acetate and ammonium dihydrogen phosphate to the above solution and stir in an 80°C water bath for 5 hours to form a sol. Dry the sol in a 120°C oven for 12 hours to form a gel precursor.
[0035] (2) The gel precursor was ground and placed in a tube furnace. It was pre-sintered at 350°C for 4 hours under an argon atmosphere, and then the temperature was raised to 750°C for 8 hours. After cooling, the sintered product was ground to obtain the final product Na3V2(PO4)3 / C cathode material.
[0036] Performance testing
[0037] The materials obtained in Example 1 and Comparative Example 1 were used as positive electrode active materials, and mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 to form a slurry. The slurry was then coated onto aluminum foil to prepare a positive electrode sheet. Using a sodium metal sheet as the counter electrode, glass fiber as the separator, and a 1M NaClO4 solution of propylene carbonate PC / ethylene carbonate EC (1:1 vol%) (containing 5 wt% fluoroethylene carbonate, FEC) as the electrolyte, a CR2032 coin cell was assembled in an argon glove box and subjected to charge-discharge tests. The voltage range was 2.5–4.0V.
[0038] The rate performance curves of the materials obtained in Example 1 and Comparative Example 1 are as follows: Figure 3 As shown. Electrochemical test results show that the discharge specific capacities of the material in Example 1 at C rates of 0.2, 1, 3, 5, 8, 10, and 15 are 110.7, 109.1, 107.5, 105.6, 102.9, 101.6, and 99.7 mAh g, respectively. -1 Meanwhile, the discharge specific capacities of the material in Comparative Example 1 at the same discharge rate were 97.3, 95.6, 94.4, 93.4, 92.1, 91.0, and 89.2 mAh g, respectively. -1 The cycling performance curve of the material obtained in Example 1 is shown below. Figure 4 As shown. The initial discharge specific capacity at 1C rate is 109.1 mAh g. -1 After 200 cycles, the capacity retention rate was 97.0%. This fully demonstrates the significant effect of the synergistic modification strategy of this invention.
[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A sodium vanadium phosphate-based composite cathode material, characterized in that, Its general chemical formula is Na3V 2-2x M x (PO4) 3-x / C@xREPO4, where: M is selected from Al3+, Fe3+, etc. + Cr3 + Sc3 + Ga3 + and In3 + One or more trivalent metal ions; RE is one or more rare earth elements selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y; 0.001≤x≤0.5; C is amorphous carbon.
2. The cathode material according to claim 1, characterized in that, The composite cathode material has a core-shell structure, with the core being a NASICON-type crystal doped with M ions and the outer shell being a composite coating layer composed of rare earth phosphate and amorphous carbon.
3. A method for preparing the sodium vanadium phosphate-based composite cathode material as described in claim 1 or 2, characterized in that, Includes the following steps: 1) Weigh out the sodium source, vanadium source, doped metal source, phosphorus source, rare earth salt and carbon source according to the stoichiometric ratio of the general chemical formula; the mass of the carbon source is 10-30% of the total mass of the sodium source, vanadium source, doped metal source, phosphorus source and rare earth salt. 2) Add the vanadium source, doped metal source, rare earth salt and carbon source from step 1) to deionized water in sequence, and heat and stir at 30-100℃ for 0.5-2 hours to form a mixed solution; 3) Add sodium source and phosphorus source to the mixed solution obtained in step 2), heat and stir at 60-120℃ for 2-10h to form sol, and then dry in an oven at 80-150℃ for 1-20h to obtain gel precursor; 4) Grind the gel precursor obtained in step 3), and then pre-sinter and sinter it at high temperature under an inert atmosphere. After cooling, the sodium vanadium phosphate-based composite cathode material Na3V is obtained. 2-2x M x (PO4) 3-x / C@xREPO4.
4. The method according to claim 3, characterized in that, In step 1), the sodium source is one or more of sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, or sodium carbonate; the vanadium source is one or more of ammonium metavanadate, ammonium vanadate, or vanadium pentoxide; the doped metal source is one or more of the chloride, acetate, oxalate, nitrate, or carbonate of the doped metal; the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, or phosphoric acid; the rare earth salt is one or more of rare earth nitrate, carbonate, or chloride; and the carbon source is one or more of citric acid, oxalic acid, ascorbic acid, glucose, or sucrose.
5. The method for preparing the sodium vanadium phosphate-based composite cathode material according to claim 3, characterized in that, In step 1), the molar ratio of sodium source, vanadium source, doped metal source, phosphorus source, and rare earth salt is 3-3.5:1-2.5:0.001-0.5:2.5-3.5:0.001-0.
05.
6. The method according to claim 3, characterized in that, In step 3), the atmosphere used during sintering is one or more of argon, nitrogen, nitrogen containing 5% hydrogen, and argon containing 5% hydrogen; the pre-sintering temperature is 200-500℃, and the time is 2-10h; the high-temperature sintering temperature is 600-1000℃, and the time is 4-20h.
7. An application of the composite cathode material according to claim 1 or 2, wherein the composite cathode material Na3V 2-2x M x (PO4) 3-x / C@xREPO4 is used in sodium-ion batteries and / or lithium-ion batteries.