A method for preparing a sodium manganese titanium phosphate positive electrode material by a solid phase method

Abstract

The application belongs to the technical field of sodium-ion battery positive electrode materials, and particularly relates to a method for preparing a sodium titanium manganese phosphate positive electrode material by a solid-phase method.The method comprises the following steps: adding a sodium source, a phosphorus source, a manganese source, a titanium source and a transition metal compound M into water and stirring until they are uniformly mixed, then adding a carbon source and a dispersing agent, mixing until they are uniformly mixed, and performing sand milling to obtain a precursor slurry; and performing spray drying on the precursor slurry, and then performing high-temperature sintering to obtain the sodium titanium manganese phosphate positive electrode material.The sodium titanium manganese phosphate positive electrode material prepared by the method has excellent crystallinity, high discharge capacity and high first coulomb efficiency, and good cycle stability; meanwhile, the solid-phase synthesis process is stable and controllable, and large-scale industrial production of the NMTP material is realized.The positive electrode material can be widely applied to low-speed electric vehicles, energy storage power stations and other scenes, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery cathode materials, specifically relating to a method for preparing sodium titanium manganese phosphate cathode material by solid-state method. Background Technology

[0002] Existing cathode materials for sodium-ion batteries mainly include polyanionic, Prussian blue, and layered oxides. Among them, polyanionic materials have received widespread attention due to their structural stability and excellent safety. Sodium iron pyrophosphate (NFPP) has become the first mass-produced polyanionic cathode material due to its structural stability, low cost, and moderate capacity.

[0003] However, NFPP has inherent drawbacks, such as a low voltage plateau (approximately 3.1 V vs Na). + The presence of Na (Na) results in limited energy density. When paired with a hard carbon anode, the battery energy density is only 105–110 Wh / kg, which is insufficient to meet the high energy density requirements of low-speed electric vehicles, energy storage power stations, and other scenarios, thus limiting its further promotion.

[0004] To overcome this bottleneck, researchers turned their attention to sodium manganese titanium phosphate (NMTP). Compared to NFPP, NMTP has a higher voltage plateau (approximately 3.5V and 4.1V vs Na). + The sodium-ion battery (Na) has an energy density of over 150 Wh / kg in the voltage range of 2.5–4.3V, which is a significant improvement over NFPP, making it more competitive in target scenarios and providing a new direction for the performance upgrade of polyanion sodium-ion batteries.

[0005] Despite the significant energy density advantage of NMTPs, many problems still need to be addressed: First, their electronic conductivity is extremely low (10⁻⁶). -9 ~10 -8 Its low S / cm and ionic conductivity limit its rate performance and make it unable to meet the requirements of rapid charge and discharge. Secondly, it is prone to Na-Mn antisite defects during cycling, resulting in significant capacity decay and affecting cycle life. In addition, its synthesis process currently mainly adopts the sol-gel method, which is difficult to achieve large-scale mass production. The solid-phase method, which is more suitable for large-scale mass production, is still in the exploratory stage, which restricts its industrialization and cost control.

[0006] In summary, optimizing the electrochemical performance of NMTP, solving its low conductivity and cycle capacity decay problems, developing a mature solid-state preparation method, and promoting large-scale mass production are the urgent technical challenges to be solved in the field of polyanionic sodium-ion battery cathode materials. Summary of the Invention

[0007] Based on the above technical background, the main objective of this invention is to provide a solid-state method for preparing sodium titanium manganese phosphate cathode material, so as to overcome the shortcomings of the prior art.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: The first aspect of this invention is to provide a method for preparing sodium manganese titanium phosphate cathode material by solid-state method, the method comprising the following steps: Step 1: Add sodium source, phosphorus source, manganese source, titanium source and transition metal compound M to water and stir evenly. Then add carbon source and dispersant and mix evenly. After sand milling, obtain precursor slurry. Step 2: Spray dry the precursor slurry to obtain precursor powder; Step 3: The precursor powder is sintered at high temperature to obtain sodium titanium manganese phosphate cathode material.

[0009] The steps described above are described in detail below.

[0010] In step 1, the sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source are weighed and mixed according to the ratio of Na:Mn:Ti:M:P = 3.1~3.5:1:0.5~0.8:0.2~0.4:2.8~3.2.

[0011] Preferably, the sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source are weighed and mixed in a ratio of Na:Mn:Ti:M:P = 3.3:1:0.7:0.3:3.

[0012] The sodium source is selected from one or more of NaOH, Na2C2O4, and Na2CO3.

[0013] Preferably, the sodium source is NaOH.

[0014] The manganese source is selected from one or more of Mn3(PO4)2, MnCO3, MnO, MnO2, and Mn3O4.

[0015] Preferably, the manganese source is Mn3(PO4)2.

[0016] The titanium source is selected from one or more of NaTi2(PO4)3, rutile titanium dioxide, anatase titanium dioxide, and tetrabutyl titanate.

[0017] Preferably, the titanium source is NaTi2(PO4)3.

[0018] Experiments revealed that when sodium titanium phosphate was used as the titanium source, the resulting cathode material exhibited high crystallinity and excellent electrochemical performance. However, when titanium dioxide or tetrabutyl titanate was used as the titanium source, the synthesized cathode material showed lower capacity or more impurities. This is mainly because rutile or anatase titanium dioxide is relatively dense, has low reactivity as a precursor, and is difficult to embed into the NASICON structure of NMTP. When tetrabutyl titanate was used as the titanium source, its hydrolysis characteristics and chemical activity were the key issues. Tetrabutyl titanate hydrolyzed into Ti(OH)4 or low-valence titanium oxide intermediates, resulting in a loose product structure and very uneven reactivity. NaTi2(PO4)3 itself has a NASICON phosphate structure, and its Na and PO4 ions can directly participate in the construction of the NASICON phase. At the same time, the co-diffusion of Mn and Na can promote the regular growth of three-dimensional ion transport channels. The formation of Na-Mn antisite defects is directly related to the lattice stress induced by impurities. Furthermore, when titanium dioxide or tetrabutyl titanate is used, the formation of impurity phases leads to uneven NMTP grain size and significant lattice distortion at grain boundaries, resulting in increased Na content during cycling. + The increased volume changes caused by repeated insertion and extraction will lead to increased Mn 2+ Migration to Na sites leads to an increase in the density of antisite defects with increasing cycle count, resulting in decreased cycle stability.

[0019] The phosphorus source is selected from one or more of H3PO4, NH4H2PO4, NaH2PO4, and Na2HPO4.

[0020] Preferably, the phosphorus source is H3PO4.

[0021] The transition metal compound M is selected from one or more of tungsten oxide, vanadium pentoxide, niobium oxide, and zinc oxide.

[0022] Preferably, the transition metal oxide is vanadium pentoxide.

[0023] The mass ratio of the carbon source to the dispersant is 1:0.5 to 1:5.

[0024] Preferably, the mass ratio of the carbon source to the dispersant is 1:1.

[0025] The amount of carbon source and dispersant added is 5 to 10% of the total weight of sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source.

[0026] Preferably, the amount of carbon source and dispersant added is 8% of the total weight of sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source.

[0027] The carbon source is selected from one or more of glucose, sucrose, citric acid, graphene, and carbon nanotubes.

[0028] Preferably, the carbon source is sucrose.

[0029] The dispersant is selected from one or more of polyacrylic acid, polyethylene glycol, and PVP.

[0030] Preferably, the dispersant is polyacrylic acid.

[0031] The solid content of the precursor slurry is 20-40%, preferably 30%.

[0032] Grind the particles to a particle size of D50≤200nm and Dmax≤800nm.

[0033] In step 2, the spray drying conditions are: inlet air temperature of 160-200℃, outlet air temperature of 80-100℃, and the moisture content of the spray-dried precursor powder is <1%.

[0034] Preferably, the spray drying conditions are: inlet air temperature of 180°C, outlet air temperature of 90°C, and the moisture content of the spray-dried precursor powder is <1%.

[0035] In step 3, the conditions for high-temperature sintering are as follows: under a nitrogen protective atmosphere, the temperature is increased to 630-660°C at a heating rate of 2-5°C / min, and sintering is carried out at this temperature for 8-15 hours.

[0036] Preferably, the conditions for high-temperature sintering are: under a nitrogen protective atmosphere, the temperature is increased to 650°C at a heating rate of 3°C / min, and sintering is carried out at this temperature for 12 hours.

[0037] A suitable sintering temperature (630-660℃) and sintering time (8-15h) can promote the full reaction of raw materials, forming a highly crystalline NMTP phase with uniform grain size, while ensuring uniform carbon coating and avoiding the formation of impurity phases or excessive oxidation of the carbon layer. If the sintering temperature is too high (e.g., 680℃ in Comparative Example 3), it will lead to excessive grain growth, increasing ion transport resistance and reducing the 0.1C discharge capacity to 89mAh / g, with an initial coulombic efficiency of only 77%. If the sintering temperature is too low (e.g., 620℃ in Comparative Example 4), the raw material reaction will be insufficient, resulting in insufficient crystallinity. Although the initial coulombic efficiency is relatively high (96%), the discharge capacity is only 95mAh / g, and the capacity decays rapidly during cycling. By using the optimized sintering temperature of 630-660℃ and the sintering time of 8-15h of this invention, a balance can be achieved between the material crystallinity and the carbon layer coating effect.

[0038] A second aspect of the present invention is to provide a sodium titanium manganese phosphate cathode material prepared by the method according to the first aspect of the present invention.

[0039] The beneficial effects of this invention are as follows: (1) The preparation method described in this invention adopts a solid-phase synthesis path of "wet grinding-spray drying-atmosphere sintering". Compared with the traditional sol-gel method, it has the advantages of simple process, controllable process, low raw material cost and high feasibility of mass production. The spray drying step can accurately control the water content of the precursor and ensure the uniformity of subsequent high-temperature sintering; at the same time, by optimizing the sintering temperature and sintering time, the crystallinity of the cathode material can be improved.

[0040] (2) This invention creatively selects NaTi2(PO4)3 as the titanium source, which itself has a NASICON phosphate structure and can directly participate in the NASICON phase construction of NMTP, promoting Na + With PO4 3- Coordinated diffusion and regular growth of three-dimensional ion transport channels effectively reduce impurity phase formation and lattice distortion. Compared to titanium dioxide (rutile and anatase) or tetrabutyl titanate used in existing technologies, NaTi2(PO4)3 as a titanium source can significantly reduce Mn during cycling. 2+ Migration to Na sites inhibits the growth of antisite defect density, thereby improving the cycling stability of the material.

[0041] (3) By doping with transition metal element M and precisely controlling the proportions of each raw material and sintering process parameters, the present invention enables the prepared NMTP material to have excellent crystallinity, effectively improving the ion and electron transport efficiency. At the same time, the cathode material has a high compaction density, which can improve the energy density and power density of the battery.

[0042] (4) The present invention can form a uniform carbon layer by using carbon source and dispersant in combination, thereby improving the electronic conductivity of the cathode material, while avoiding the adverse effects of excessively high or low carbon content on battery performance.

[0043] (5) The sodium, phosphorus, manganese and carbon sources used in this invention have wide compatibility and can be flexibly selected according to the needs of industrial production. The NMTP cathode material prepared by this invention has excellent energy density and cycle performance, and is compatible with various sodium-ion battery structures such as button, soft pack and cylindrical, providing key material support for the industrialization and promotion of sodium-ion batteries. Attached Figure Description

[0044] Figure 1 The XRD pattern of the cathode material described in Example 1 is shown. Figure 2 The charge-discharge curves of the sodium-ion half-cell assembled in Example 1 are shown at room temperature (25°C) and a current density of 0.1 C. Detailed Implementation

[0045] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0046] Example The present invention is further illustrated below with specific examples. These embodiments are merely illustrative and not intended to limit the scope of the invention. All raw materials used in the embodiments of the present invention are commercially available.

[0047] Example 1 A method for preparing sodium manganese titanium phosphate cathode material by solid-state method, the method comprising the following steps: The ingredients were prepared and milled. Using pure water as a solvent, a slurry was prepared with a solid content of 30% and a total dry powder weight of 300 g, and then stirred evenly. The phosphorus source in the dry powder was phosphoric acid, the sodium source was sodium hydroxide, the titanium source was sodium titanium phosphate, the manganese source was manganese phosphate, the carbon source was sucrose, and the dispersant was polyacrylic acid compound. In addition, transition metal oxide M (vanadium pentoxide) was added to the dry powder. The sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source were weighed and mixed according to Na:Mn:Ti:M:P=3.3:1:0.7:0.3:3. The total mass ratio of carbon source and polyacrylic acid was 1:1, and the amount of carbon source and polyacrylic acid added was 8% of the total weight of other dry powder (sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source). Then, the powder was milled until the particle size D50≤200nm and Dmax≤800nm ​​to obtain the precursor slurry.

[0048] The precursor slurry is spray-dried; the precursor slurry with qualified particle size is spray-dried into powder. The inlet air temperature of the spray dryer is set to 180℃ and the outlet air temperature is set to 90℃ to ensure that the moisture content of the precursor powder is less than 1%, thus obtaining the precursor powder.

[0049] The precursor powder is sintered; the dried precursor powder is placed in a tube furnace for sintering. During the sintering process, nitrogen gas must be introduced into the tube furnace throughout the process. The heating rate of sintering is 3℃ / min, and the temperature is raised to 650℃. The material is then sintered at this temperature for 12 h to obtain the cathode material.

[0050] The sintered positive electrode material was used to prepare a button cell for testing. NMP (N-methylpyrrolidone) was used as a solvent and SP (conductive carbon black) was used as a conductive agent. The positive electrode material, NMP, and SP were mixed evenly in a mass ratio of 90:5:5. The mixture was then evenly coated on aluminum foil as the positive electrode, sodium sheet was used as the negative electrode, and 1 mol / L LiPF6 / EC (lithium hexafluorophosphate / ethylene carbonate) : DMC (dimethyl carbonate) (LiPF6 / EC:DMC volume ratio 1:1) was used as the electrolyte. PP was used as the separator to assemble CR2016 button cells.

[0051] Example 2 The titanium manganese sodium phosphate cathode material was prepared in a manner similar to that in Example 1, except that the titanium source, titanium sodium phosphate, was replaced with rutile titanium dioxide. Example 3 The titanium manganese sodium phosphate cathode material was prepared in a manner similar to that in Example 1, except that the titanium source, titanium sodium phosphate, was replaced with anatase titanium dioxide. Example 4 The titanium manganese sodium phosphate cathode material was prepared in a manner similar to that in Example 1, except that the titanium source, titanium sodium phosphate, was replaced with tetrabutyl titanate. Comparative Example Comparative Example 1 The sodium titanium manganese phosphate cathode material was prepared in a manner similar to that in Example 1, except that the amount of carbon source sucrose and dispersant polyacrylic acid added was 15% of the total weight of other dry powders.

[0052] Comparative Example 2 The sodium titanium manganese phosphate cathode material was prepared in a manner similar to that in Example 1, except that the amount of carbon source sucrose and dispersant polyacrylic acid added was 3% of the total weight of other dry powders.

[0053] Comparative Example 3 The sodium titanium manganese phosphate cathode material was prepared in a manner similar to that in Example 1, except that the temperature was raised to 680°C and sintered at that temperature for 12 h.

[0054] Comparative Example 4 The sodium titanium manganese phosphate cathode material was prepared in a manner similar to that in Example 1, except that the temperature was raised to 620°C and sintered at that temperature for 12 h.

[0055] Comparative Example 5 The sodium titanium manganese phosphate cathode material was prepared in a manner similar to that in Example 1, except that no transition metal oxide M was added. Comparative Example 6 The preparation of the sodium titanium manganese phosphate cathode material was carried out in a similar manner to that in Example 1, except that the sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source were weighed and mixed in the ratio of Na:Mn:Ti:M:P=3.3:1:0.7:0.5:3. Experimental Example Example 1: Charge and Discharge Performance Test Button cells made from the cathode materials prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to charge-discharge tests, initial coulombic efficiency tests, compaction density tests, and carbon content tests. The test method was as follows: charge-discharge tests were performed at a voltage of 2.5-4.2V and a charge-discharge rate of 0.1C. The test results are shown in Table 1.

[0056] Table 1

[0057] In Table 1, comparing Examples 1-4, and Examples 2-3, after replacing the titanium source with sodium titanium phosphate or rutile titanium dioxide, anatase titanium dioxide, or tetrabutyl titanate, the 0.1C charge / discharge capacity and initial coulombic efficiency were reduced. Furthermore, the compaction density of Examples 3 and 4 and the carbon content of Example 2 were reduced compared to Example 1. These results indicate that sodium titanium phosphate as a titanium source is beneficial for improving charge / discharge capacity, initial coulombic efficiency, and compaction density.

[0058] Compared to Example 1, Comparative Examples 1 and 2 adjusted the total amount of carbon source sucrose and dispersant polyacrylic acid. Comparative data from Comparative Example 1 (carbon source + dispersant addition 15%), Example 1 (addition amount 8%), and Comparative Example 2 (addition amount 3%) showed that Example 1, with a carbon content of 2.52 wt.%, exhibited the best overall performance with a discharge capacity of 108 mAh / g and a coulombic efficiency of 86%. Comparative Example 1, with an excessively high addition amount (15%), increased the carbon content to 4.34 wt.%, resulting in a slight increase in coulombic efficiency to 88%, but a significant decrease in compaction density to 1.85 g / cm³. 3 (Low compaction density reduces battery energy density), with the discharge capacity dropping to 97 mAh / g. Comparative Example 2 had an excessively low addition amount (3%), with a carbon content of only 0.56 wt.%, resulting in insufficient electronic conductivity, leading to a discharge capacity of only 69 mAh / g and a coulombic efficiency of 78%, a significant performance degradation. These results indicate that the amount of carbon source and dispersant added has a significant impact on the battery's charge / discharge capacity, coulombic efficiency, and compaction density. An addition amount of approximately 8% carbon source and dispersant is the optimal choice for balancing conductivity, compaction density, and discharge capacity.

[0059] Based on the data from Comparative Example 3 (sintering temperature 680℃), Example 1 (sintering temperature 650℃), and Comparative Example 4 (sintering temperature 620℃), it can be seen that both excessively high and excessively low sintering temperatures will impair discharge performance. In Comparative Example 3, the temperature was too high (680℃), and although the charging capacity could reach a maximum of 116mAh, the discharge capacity was only 89mAh / g and the coulombic efficiency was 77%. This may be due to excessive grain growth caused by high temperature, which leads to increased ion transport resistance. In Comparative Example 4, the temperature was too low (620℃), and the raw material reaction was insufficient. Although the coulombic efficiency was as high as 96%, the discharge capacity was only 95mAh / g, and insufficient crystallinity would exacerbate the capacity decay during cycling. The sintering temperature of 650℃ in Example 1 can achieve a balance between sufficient raw material reaction and uniform grain size, ensuring high discharge capacity and good coulombic efficiency, indicating that the carbon layer coating effect is stable within this temperature range. The above results indicate that sintering temperature and sintering time have a significant impact on the charge-discharge capacity, coulombic efficiency, and compaction density of the battery. A sintering temperature of 650℃ and a sintering time of approximately 12 hours are beneficial for improving the battery's electrical performance.

[0060] Compared with Example 1, Comparative Example 5 did not add transition metal oxide M. The charge-discharge capacity, first coulombic efficiency and compaction density of Comparative Example 5 were all lower than those of Example 1, indicating that adding transition metal oxide M during the preparation process is beneficial to improving the charge-discharge capacity, first coulombic efficiency and compaction density of the battery.

[0061] Compared with Example 1, Comparative Example 6 changed the ratio of sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source. The charge-discharge capacity, initial coulombic efficiency and compaction density of Comparative Example 6 were lower than those of Example 1. The above results show that the ratio of sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source has a significant impact on the battery capacity, initial coulombic efficiency and compaction density. Only when the ratio of sodium source, manganese source, titanium source, transition metal oxide M and phosphorus source is within the range defined by this invention can the battery have better electrical performance.

[0062] Experiment Example 2 XRD Test The sodium titanium manganese phosphate cathode material prepared in Example 1 was subjected to XRD testing, and the test results are as follows: Figure 1 As shown.

[0063] from Figure 1 As can be seen from the data, the sodium titanium manganese phosphate cathode material has excellent crystallinity.

[0064] Experiment Example 3: Charge and Discharge Test A sodium-ion half-cell made with the positive electrode material obtained in Example 1 was subjected to charge-discharge tests at room temperature (25°C) and a current density of 0.1 C. The test results are as follows: Figure 2 As shown.

[0065] from Figure 2 As can be seen, within the V range of 2.5-4.2, the sodium-ion half-cell made from this cathode material exhibits a charging capacity of 125 mAh / g and a discharging capacity of 108 mAh / g; furthermore, at 3.6V, representing Mn... 2+ / Mn 3+ The voltage plateau of the redox potential corresponds to a capacity of 60 mAh / g, indicating that the redox potential of Mn ions exhibits good performance, demonstrating that the sodium ion half-cell has good cycle performance and significantly suppresses the Mn-Na mixing phenomenon.

[0066] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing sodium manganese titanium phosphate cathode material by solid-state method, characterized in that, The method includes the following steps: Step 1: Add sodium source, phosphorus source, manganese source, titanium source and transition metal compound M to water and stir evenly. Then add carbon source and dispersant and mix evenly. After sand milling, obtain precursor slurry. Step 2: Spray dry the precursor slurry to obtain precursor powder; Step 3: The precursor powder is sintered at high temperature to obtain sodium titanium manganese phosphate cathode material.

2. The method according to claim 1, characterized in that, In step 1, The sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source are weighed and mixed according to the ratio of Na : Mn : Ti : M : P = 3.1~3.5 : 1 : 0.5~0.8 : 0.2~0.4 : 2.8~3.

2.

3. The method according to claim 1, characterized in that, In step 1, The sodium source is selected from one or more of NaOH, Na2C2O4, and Na2CO3; and / or, The manganese source is selected from one or more of Mn3(PO4)2, MnCO3, MnO, MnO2, and Mn3O4; and / or, The titanium source is selected from one or more of NaTi2(PO4)3, rutile titanium dioxide, anatase titanium dioxide, and tetrabutyl titanate; and / or, The transition metal compound M is selected from one or more of tungsten oxide, vanadium pentoxide, niobium oxide, and zinc oxide; and / or, The phosphorus source is selected from one or more of H3PO4, NH4H2PO4, NaH2PO4, and Na2HPO4.

4. The method according to claim 1, characterized in that, In step 1, The mass ratio of the carbon source to the dispersant is 1:0.5 to 1:

5.

5. The method according to claim 1, characterized in that, In step 1, The amount of carbon source and dispersant added is 5 to 10% of the total weight of sodium source, manganese source, titanium source, transition metal compound M, and phosphorus source.

6. The method according to claim 1, characterized in that, In step 1, The carbon source is selected from one or more of glucose, sucrose, citric acid, graphene, and carbon nanotubes; and / or, The dispersant is selected from one or more of polyacrylic acid, polyethylene glycol, and PVP.

7. The method according to claim 1, characterized in that, In step 1, The solid content in the precursor slurry is 20-40%; Grind the particles to a particle size of D50≤200nm and Dmax≤800nm.

8. The method according to claim 1, characterized in that, In step 2, The spray drying conditions are as follows: inlet air temperature is 160-200℃, outlet air temperature is 80-100℃, and the moisture content of the precursor powder after spray drying is <1%.

9. The method according to claim 1, characterized in that, In step 3, The conditions for high-temperature sintering are as follows: under a nitrogen protective atmosphere, the temperature is increased to 630-660°C at a heating rate of 2-5°C / min, and sintering is carried out at this temperature for 8-15 hours.

10. A sodium manganese titanium phosphate cathode material prepared by the method according to any one of claims 1 to 9.

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