High-capacity long-cycle lanthanum-doped sodium vanadium phosphate positive electrode material and preparation method thereof

Abstract

The invention discloses a high-capacity long-cycle lanthanum-doped sodium vanadium phosphate positive electrode material and a preparation method thereof, relates to the technical field of sodium ion batteries, and aims to solve the problem that an existing NVP material is difficult to have high capacity and structural stability at the same time. The technical key points of the invention are as follows: the high-capacity long-cycle lanthanum-doped sodium vanadium phosphate positive electrode material is provided, the high-capacity long-cycle lanthanum-doped sodium vanadium phosphate positive electrode material contains an NVP type material with a composition formula (I) and Na < 3 + x > V < 2-y > Lay (PO4) 3 / C (I), x and y meet the following formula, x is more than 0 and less than or equal to 0.5, y is more than or equal to 0.01 and less than or equal to 0.06, and C is an amorphous carbon layer which is formed by in-situ carbonization and uniformly coats the surfaces of material particles. The rare earth La element is introduced to dope the V site, crystal lattices are expanded, a wider channel is provided for de-intercalation of sodium ions, meanwhile, La doping is beneficial to stabilization of the crystal structure, and the transmission behavior of the sodium ions is optimized; on the basis of inheriting the advantage of ultrahigh capacity of a sodium-rich strategy, the cycling stability of the material is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more specifically, to a high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material and its preparation method. Background Technology

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage due to the abundant reserves of sodium, low cost, and high safety. As a key component of sodium-ion batteries, the cathode material determines the battery's energy density, cycle life, and overall cost. Among many cathode materials, sodium vanadium phosphate (Na3V2(PO4)3, or NVP for short) with a NASICON (sodium superionic conductor) structure has attracted much attention due to its stable three-dimensional framework structure and high operating voltage (approximately 3.4 V vs. Na+ / / Na). However, NVP material has low intrinsic electronic conductivity and can only reversibly insert and extract two sodium ions, resulting in a limited theoretical specific capacity (approximately 117 mAh·g). -1 This severely restricts its practical application.

[0003] To overcome these shortcomings, the industry has proposed several improvement methods. Firstly, carbon coating technology can be used to improve the electronic conductivity of the material, but this method cannot break through the upper limit of its theoretical capacity. Secondly, other metal elements can be used to dope and modify the vanadium sites. For example, Tongji University (CN117228647A) proposed using Co and Fe co-doping and introducing sodium vacancies to improve the voltage window and structural stability. The Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CN116344752A) has prepared various vanadium-doped (Mn, Fe, Cr, Ti, etc.) phosphate materials using a melt-sintering method, but transition metal doping often involves increased cost, ion dissolution, or the Jahn-Teller effect. Fuzhou University (CN115084502A) has developed a Na4V... x Mn y Ni z Although the (PO4)3 material increases the operating voltage, the Ni element does not participate in the redox reaction, resulting in limited actual capacity.

[0004] Recently, a "sodium-rich" research strategy has provided a new approach to overcoming the NVP capacity bottleneck, as described by Lu et al. [1] (Carbon. 2022, 196: 562-572) A Na4FeV(PO4)3 material was synthesized via V 3+ / V 4+ and Fe 2+ / Fe 3+ Redox couples achieved high capacity, but Fe 2+ Easily oxidized to Fe 3+Furthermore, the NaFePO4 impurity phase is prone to appear during material preparation, affecting purity and performance. Cong et al. [2] (ACS Sustainable Chem. Eng. 2023, 11(45):16341-16353) reported Na 3+x V2(PO4)3 / C(x>0) materials achieve specific capacities exceeding theoretical values ​​by allowing excess sodium to occupy Na2 sites and participate in electrochemical reactions. However, the excessive insertion and extraction of sodium leads to lattice shrinkage, causing structural stress accumulation and capacity decay. Therefore, ensuring the structural stability of sodium-rich NVP materials while achieving high capacity has become a pressing technical challenge. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] Existing NVP materials struggle to balance high capacity with structural stability.

[0007] To address the aforementioned technical problems, this invention provides a high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material and its preparation method. By introducing rare-earth element La to dope the V-site, the larger ionic radius of La provides a more spacious channel for sodium ion insertion / extraction, effectively buffering volume strain during cycling. Simultaneously, La doping helps stabilize the crystal structure and optimize sodium ion transport behavior; while inheriting the ultra-high capacity advantages of the sodium-rich strategy, the cycling stability of the material is significantly improved. The technical solution adopted in this invention is as follows:

[0008] This invention provides a high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material, which contains an NVP-type material with the following composition (I).

[0009] Na 3+x V 2-y La y (PO4)3 / C…(I)

[0010] Where x and y satisfy the following equation,

[0011] 0 < x ≤ 0.5,

[0012] 0.01 ≤ y ≤ 0.06,

[0013] C represents an amorphous carbon layer that is uniformly coated on the surface of material particles, formed through in-situ carbonization.

[0014] Furthermore, the thickness of the amorphous carbon layer is 3-6 nm.

[0015] This invention provides a method for preparing the above-mentioned high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material, comprising the following steps:

[0016] (1) Weigh out the sodium source, vanadium source, lanthanum source, phosphorus source and carbon source according to the element ratio in the composition formula (I);

[0017] (2) Dissolve the weighed vanadium source and carbon source in deionized water to obtain a mixed solution;

[0018] (3) Dissolve the weighed phosphorus source and sodium source in deionized water to obtain mixture two;

[0019] (4) Preliminary blending: Under continuous stirring, the first mixture is slowly added dropwise to the second mixture to prepare a suspension;

[0020] (5) Dissolve the weighed lanthanum source in dilute acetic acid solution to obtain lanthanum source solution. Under vigorous stirring, add the lanthanum source solution dropwise to the suspension obtained in step (4). During the process, adjust the pH value of the reaction system in the range of 3.2-3.8 by adding dilute acetic acid solution dropwise. Continue the reaction to obtain sol-gel.

[0021] (6) Dry the sol-gel to obtain the precursor;

[0022] (7) The precursor is calcined under a protective atmosphere to form a uniform carbon coating layer on the surface of the material. After cooling and grinding, lanthanum-doped sodium vanadium phosphate cathode material is obtained.

[0023] Furthermore, the molar ratio of the carbon source added to the Na source in the cathode material is (1.2-1.8):1.

[0024] Further, the sodium source mentioned in step (1) is at least one of sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), or sodium acetate (CH3COONa);

[0025] The vanadium source is at least one of ammonium metavanadate (NH4VO3) or vanadium pentoxide (V2O5);

[0026] The lanthanum source is lanthanum acetate (La(OOCCH3)3·6H2O);

[0027] The phosphorus source is at least one of ammonium dihydrogen phosphate (NH4H2PO4) or diammonium hydrogen phosphate ((NH4)2HPO4);

[0028] The carbon source is at least one of citric acid, oxalic acid, or ascorbic acid.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. The dual stabilization mechanism of "lattice struts" and "carbon layer buffers" works synergistically to ensure long cycle life:

[0031] This invention innovatively incorporates rare earth element La 3+ Introducing a crystal structure, its large ionic radius (1.06 Å) is beneficial to the V-site (V... 3+ The substitution of sodium ions (0.64 Å) creates an effective "lattice support" effect, pre-expanding the sodium ion migration channels and enhancing the rigidity of the structural framework. Simultaneously, the in-situ formed uniform amorphous carbon coating (3-6 nm thick) not only constructs a three-dimensional conductive network, but more importantly, this carbon layer acts as an excellent elastic buffer matrix, effectively suppressing and dispersing the microscopic volume changes and internal stresses caused by sodium ion insertion / extraction during charging and discharging. This synergistic effect of "internal lattice support" and "external carbon layer constraint" is the core key to achieving ultra-long cycle stability of the material.

[0032] 2. Precise pH control strategy to ensure high-purity phase and effective doping:

[0033] In the sol-gel preparation process, this invention uses a precision pH meter to monitor the pH in real time and dynamically add dilute acetic acid, precisely stabilizing the pH of the reaction system within the critical range of 3.2-3.8. This precise pH control fundamentally inhibits the growth of lanthanum source (La). 3+ ) and phosphorus source (PO4) 3- This process directly binds to the tendency to form the lanthanum phosphate (LaPO4) impurity phase, thus ensuring that La can effectively dope into the lattice sites of Na3V2(PO4)3, rather than existing as an impurity phase. This is a key process guarantee for obtaining high-purity, high-performance target products.

[0034] 3. Achieving simultaneous breakthroughs in capacity and stability through triple modification of "lanthanum doping - sodium enrichment - carbon coating":

[0035] This invention organically combines lanthanum doping, a sodium-rich strategy, and in-situ carbon coating, resulting in a synergistic effect of "1+1+1>3". The sodium-rich strategy provides a sodium ion source exceeding theoretical values, laying the foundation for high capacity; La doping improves structural stability while optimizing sodium ion transport kinetics; and uniform carbon coating solves the problem of low intrinsic conductivity and assists in buffering volume effects. Ultimately, the material can achieve an initial discharge specific capacity of no less than 120 mAh / g at 0.2C rate, while maintaining a capacity retention of over 92% after 500 cycles, truly achieving a perfect balance between high capacity and long cycling duration.

[0036] 4. The process has good reproducibility and is suitable for large-scale preparation:

[0037] The preparation method has a clear process and key parameters (such as pH value and calcination regime) are highly controllable, which effectively ensures batch-to-batch consistency and stability, laying a solid foundation for large-scale industrial production. Attached Figure Description

[0038] Figure 1 Na in the embodiments of the present invention 3.5 V 1.94 La 0.06 (PO4)3 / C and Na 3.5 XRD comparison chart of V2(PO4)3 / C;

[0039] Figure 2 Na in the embodiments of the present invention 3.5 V 1.94 La 0.06 (PO4)3 / C(a) and Na 3.5 SEM comparison images of V2(PO4)3 / C(b);

[0040] Figure 3 Na in the embodiments of the present invention 3.5 V 1.94 La 0.06 TEM image of (PO4)3 / C;

[0041] Figure 4 This is a graph showing the performance of the CR2025 button cell in this embodiment of the invention after 500 cycles at a current density of 0.2C. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments or examples are merely some, not all, of the embodiments or examples of the present invention. All other embodiments or examples obtained by those skilled in the art based on the embodiments or examples of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] This disclosure relates to NVP-type materials containing a NASICON-type crystal structure with space group R-3c; it has a stable three-dimensional framework structure. In this embodiment, rare earth element La is introduced to dope the V sites, because La... 3+ Doping causes lattice expansion, making Na... +The diffusion channels are enlarged, effectively increasing the material's capacity. Furthermore, in-situ carbonization forms a uniform amorphous carbon layer coating the surface of the material particles.

[0045] More specifically, the lanthanum-doped sodium vanadium phosphate cathode material disclosed herein contains an NVP-type material with the following composition (I).

[0046] Na 3+x V 2-y La y (PO4)3 / C…(I)

[0047] Where x and y satisfy the following equation,

[0048] 0 < x ≤ 0.5,

[0049] 0.01 ≤ y ≤ 0.06,

[0050] C represents an amorphous carbon layer that is uniformly coated on the surface of material particles, formed through in-situ carbonization.

[0051] The preparation method and material properties of the lanthanum-doped sodium vanadium phosphate cathode material of the present invention will be described below with reference to specific embodiments and comparative examples.

[0052] Example 1

[0053] A method for preparing a high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material includes the following steps:

[0054] (1) Weighing of raw materials: According to the general chemical formula Na 3.5 V 1.94 La 0.06 The stoichiometric ratio of (PO4)3 is as follows: sodium acetate (CH3COONa) as sodium source, ammonium metavanadate (NH4VO3) as vanadium source, lanthanum acetate (La(OOCCH3)3·6H2O) as lanthanum source, ammonium dihydrogen phosphate (NH4H2PO4) as phosphorus source, and citric acid as carbon source.

[0055] The molar ratio of the added carbon source to Na is 1.2:1.

[0056] (2) Vanadium source pretreatment: The vanadium source and carbon source weighed in step (1) are added to deionized water at 80°C in sequence, and then magnetically stirred for 30 minutes in a water bath at 80°C until a uniform, transparent dark blue mixed liquid is obtained.

[0057] (3) Sodium and phosphorus sources are dissolved: The phosphorus source and sodium source weighed in step (1) are dissolved in deionized water at 80°C in sequence and stirred magnetically until completely dissolved to obtain a clear mixed solution II.

[0058] (4) Preliminary mixing: Under continuous stirring, the mixture obtained in step (2) is slowly added dropwise to the mixture obtained in step (3) at a rate of 2 mL / min through a constant pressure dropping funnel; after the addition is completed, continue stirring for 30 minutes to obtain a blue suspension.

[0059] (5) Lanthanum source introduction and sol-gelation: The lanthanum source weighed in step (1) was dissolved in a 5% dilute acetic acid solution to obtain a lanthanum source solution; under vigorous stirring, the obtained lanthanum source solution was added dropwise to the suspension obtained in step (4) at a rate of 1 mL / min; throughout the dropwise addition and mixing process, the pH value of the system was monitored in real time using a precision pH meter, and the pH value of the reaction system was precisely controlled and stabilized in the range of 3.2-3.8 by dynamically adding 5% dilute acetic acid; subsequently, the system temperature was maintained at 80℃ and stirred continuously for 8 hours, so that the mixture was finally transformed into a viscous, uniform blue sol-gel.

[0060] (6) Precursor drying: The sol-gel obtained in step (5) is transferred to a vacuum drying oven and dried at 80°C for 10 hours to obtain a fluffy blue precursor.

[0061] (7) High-temperature calcination: After the precursor obtained in step (6) is initially ground and passed through a 200-mesh sieve, it is placed in a corundum boat and calcined in a tube furnace under a nitrogen atmosphere. First, the temperature is raised to 350°C at a heating rate of 3-5°C / min and held for 3 hours. Then, the temperature is raised to 800°C at the same heating rate and held for 10 hours to complete the crystallization reaction of the material and realize the in-situ carbonization of the carbon source, and finally a uniform carbon coating layer is formed on the surface of the material.

[0062] (8) Post-processing of the product: After calcination in step (7), the product is naturally cooled to room temperature, taken out and ground, and then passed through a 200-mesh sieve to obtain powdered lanthanum-doped sodium-rich sodium vanadium phosphate / carbon composite cathode material (Na). 3.5 V 1.94 La 0.06 (PO4)3 / C).

[0063] The cathode material preparation method disclosed herein is not limited to cathode materials with the above-mentioned elemental ratios. Based on the composition formula (I), by controlling x to be below 0.5 and y to be above 0.01 and below 0.06, materials with different Na, V, and La elemental ratios can be prepared. Furthermore, it is not limited to the sodium source, vanadium source, phosphorus source, and carbon source mentioned above. Sodium source can be one or more of sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), or sodium acetate (CH3COONa); vanadium source can be one or more of ammonium metavanadate (NH4VO3) or vanadium pentoxide (V2O5); phosphorus source can be one or more of ammonium dihydrogen phosphate (NH4H2PO4) or diammonium hydrogen phosphate ((NH4)2HPO4); and carbon source can be one or more of citric acid, oxalic acid, or ascorbic acid.

[0064] Example 2

[0065] The difference between this embodiment and Embodiment 1 is that in step (1), according to the general chemical formula Na... 3.1 V 1.99 La 0.01 Based on the stoichiometric ratio of (PO4)3, sodium acetate (CH3COONa) as the sodium source, ammonium metavanadate (NH4VO3) as the vanadium source, lanthanum acetate (La(OOCCH3)3·6H2O) as the lanthanum source, ammonium dihydrogen phosphate (NH4H2PO4) as the phosphorus source, and citric acid as the carbon source were accurately weighed. The final product was a lanthanum-doped sodium-rich sodium vanadium phosphate / carbon composite cathode material (Na). 3.1 V 1.99 La 0.01 (PO4)3 / C).

[0066] Example 3

[0067] The difference between this embodiment and Embodiment 1 is that in step (1), according to the general chemical formula Na... 3.3 V 1.97 La 0.03 Based on the stoichiometric ratio of (PO4)3, sodium acetate (CH3COONa) as the sodium source, ammonium metavanadate (NH4VO3) as the vanadium source, lanthanum acetate (La(OOCCH3)3·6H2O) as the lanthanum source, ammonium dihydrogen phosphate (NH4H2PO4) as the phosphorus source, and citric acid as the carbon source were accurately weighed. The final product was a lanthanum-doped sodium-rich sodium vanadium phosphate / carbon composite cathode material (Na). 3.3 V 1.97 La 0.03 (PO4)3 / C).

[0068] Example 4

[0069] The difference between this embodiment and Embodiment 1 is that, in step (1), oxalic acid is used as the carbon source. The final product is a lanthanum-doped sodium-rich sodium vanadium phosphate / carbon composite cathode material (Na...). 3.5 V 1.94 La 0.06 (PO4)3 / C).

[0070] Comparative Example 1

[0071] (1) Weighing of raw materials: According to the general chemical formula Na 3.5 The stoichiometric ratio of V2(PO4)3 is determined by accurately weighing sodium acetate (CH3COONa), ammonium metavanadate (NH4VO3), ammonium dihydrogen phosphate (NH4H2PO4), and citric acid.

[0072] The molar ratio of the added carbon source to Na is 1.2:1.

[0073] (2) Vanadium source pretreatment: The vanadium source and carbon source weighed in step (1) are added to deionized water at 80°C in sequence, and then magnetically stirred for 30 minutes in a water bath at 80°C until a uniform, transparent dark blue mixed liquid is obtained.

[0074] (3) Sodium and phosphorus sources are dissolved: The phosphorus source and sodium source weighed in step (1) are dissolved in deionized water at 80°C in sequence and stirred magnetically until completely dissolved to obtain a clear mixed solution II.

[0075] (4) Preliminary mixing: Under continuous stirring, the dark blue mixture obtained in step (2) is slowly added dropwise to the clear mixture obtained in step (3) at a rate of 2 mL / min through a constant pressure dropping funnel; after the addition is completed, continue stirring for 30 minutes to obtain a blue suspension.

[0076] (5) Sol-gelation: The temperature of the blue suspension system obtained in step (4) is maintained at 80°C and stirred continuously for 8 hours, so that it is eventually transformed into a viscous and uniform blue sol-gel.

[0077] (6) Precursor drying: The sol-gel obtained in step (5) is transferred to a vacuum drying oven and dried at 80°C for 10 hours to obtain a fluffy blue precursor.

[0078] (7) High-temperature calcination: After the precursor obtained in step (6) is initially ground and passed through a 200-mesh sieve, it is placed in a corundum boat and calcined in a tube furnace under a nitrogen atmosphere. First, the temperature is raised to 350°C at a heating rate of 3-5°C / min and held for 3 hours. Then, the temperature is raised to 800°C at the same heating rate and held for 10 hours to complete the crystallization reaction of the material and realize the in-situ carbonization of the carbon source, and finally a uniform carbon coating layer is formed on the surface of the material.

[0079] (8) Post-processing of the product: After the product from step (7) is calcined, it is naturally cooled to room temperature, taken out and ground, and then passed through a 200-mesh sieve to obtain sodium-rich vanadium phosphate sodium / carbon composite cathode material (Na). 3.5 V2(PO4)3 / C).

[0080] The cathode material (Na) obtained in Example 1 3.5 V 1.94 La 0.06 (PO4)3 / C) and the cathode material obtained in Comparative Example 1 (Na) 3.5 XRD analysis was performed on V2(PO4)3 / C, such as... Figure 1 As shown, all diffraction peaks perfectly correspond to the standard NASICON-type sodium vanadium phosphate structure (PDF#53-0018, space group R-3c), and no obvious impurity phase peaks were observed. This proves that the synthesized material has a high-purity target crystal structure, consistent with undoped lanthanum NVP (Na+). 3.5 Compared to V2(PO4)3 / C, the characteristic peaks of the material doped with lanthanum shift to the left, indicating that lattice expansion occurred after doping. + The diffusion channels become larger.

[0081] The cathode material (Na) obtained in Example 1 3.5 V 1.94 La 0.06 (PO4)3 / C) and the cathode material obtained in Comparative Example 1 (Na) 3.5 V2(PO4)3 / C) was subjected to SEM detection, such as Figure 2 As shown, Na 3.5 V 1.94 La 0.06 (PO4)3 / C compared to undoped Na 3.5 The finer particle size distribution of V2(PO4)3 / C further demonstrates that lanthanum doping plays a role in refining the grain size.

[0082] The cathode material (Na) obtained in Example 1 3.5 V 1.94 La 0.06 (PO4)3 / C) was subjected to TEM detection, such as Figure 3 As shown, this indicates that Na 3.5 V 1.94 La 0.06 The (PO4)3 / C surface is coated with a uniform carbon layer of 3.37-5.94 nm. This carbon layer can effectively improve the electronic conductivity of the material and provide a buffer for the volume change during the sodium ion insertion / extraction process. It is a key structure for improving electrochemical performance.

[0083] The cathode materials obtained in Examples 1-4 and Comparative Example 1 were assembled into CR2025 coin cells and subjected to 500 cycles at a current density of 0.2C. Figure 4 As shown, Examples 1-4 exhibit excellent high capacity and cycle stability. Their initial discharge specific capacities were 138.9 mAh·g⁻¹, 124.9 mAh·g⁻¹, 130.4 mAh·g⁻¹, and 135.1 mAh·g⁻¹, respectively. After 500 charge-discharge cycles, the specific capacities remained at 134.4 mAh·g⁻¹, 115.7 mAh·g⁻¹, 123.4 mAh·g⁻¹, and 129.9 mAh·g⁻¹, respectively, with capacity retention rates of 96.7%, 92.6%, 94.6%, and 96.2%. Compared to Comparative Example 1 (initial specific capacity 134.3 mAh·g⁻¹, specific capacity maintained at 108.8 mAh·g⁻¹ after 500 cycles, capacity retention rate 81%), this demonstrates superior capacity retention, fully proving the long-lifetime characteristics of the material under high specific capacity.

[0084] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

[0085] The documents cited in this invention include:

[0086] [1]Lu, Fengqi, et al. New-type NASICON-Na4FeV(PO4)3 cathode with highretention and durability for sodium ion batteries[J]. Carbon, 2022, 196: 562-572.

[0087] [2]Cong J , Luo SH , Li P .Ultracapacity Properties of the RefinedStructure in Na-Rich Na 3.4 V2(PO4)3 / C as Sodium-Ion Battery Cathodes by Tapping the Na-Vacancy Potential[J]. ACS Sustainable Chemistry & Engineering, 2023,11(45):16341-16353.DOI:10.1021 / acssuschemeng.3c05572.

Claims

1. A high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material, characterized in that, It contains NVP-type materials with the following composition (I), Na 3+x V 2-y The y (PO4)3 / C…(I) Where x and y satisfy the following equation, 0＜x ≤ 0.5， 0.01 ≤ y ≤ 0.06， C represents an amorphous carbon layer that is uniformly coated on the surface of material particles, formed through in-situ carbonization.

2. The high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material according to claim 1, characterized in that, The thickness of the amorphous carbon layer is 3-6 nm.

3. The method for preparing the high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material according to claim 1, characterized in that, Includes the following steps: (1) Weigh out the sodium source, vanadium source, lanthanum source, phosphorus source and carbon source according to the element ratio in the composition formula (I); (2) Dissolve the weighed vanadium source and carbon source in deionized water to obtain a mixed solution; (3) Dissolve the weighed phosphorus source and sodium source in deionized water to obtain mixture two; (4) Preliminary blending: Under continuous stirring, the first mixture is slowly added dropwise to the second mixture to prepare a suspension; (5) Dissolve the weighed lanthanum source in dilute acetic acid solution to obtain lanthanum source solution. Under vigorous stirring, add the lanthanum source solution dropwise to the suspension obtained in step (4). During the process, adjust the pH value of the reaction system in the range of 3.2-3.8 by adding dilute acetic acid solution dropwise. Continue the reaction to obtain sol-gel. (6) Dry the sol-gel to obtain the precursor; (7) The precursor is calcined under a protective atmosphere to form a uniform carbon coating layer on the surface of the material. After cooling and grinding, lanthanum-doped sodium vanadium phosphate cathode material is obtained.

4. The method for preparing the high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material according to claim 3, characterized in that, The molar ratio of the carbon source added to the Na source in the cathode material is (1.2-1.8):

1.

5. The method for preparing the high-capacity, long-cycle lanthanum-doped sodium vanadium phosphate cathode material according to claim 4, characterized in that, The sodium source mentioned in step (1) is at least one of sodium carbonate, sodium bicarbonate, or sodium acetate; The vanadium source is at least one of ammonium metavanadate or vanadium pentoxide. The lanthanum source is lanthanum acetate; The phosphorus source is at least one of ammonium dihydrogen phosphate or diammonium hydrogen phosphate; The carbon source is at least one of citric acid, oxalic acid, or ascorbic acid.

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