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US-12623918-B2 - Composite sodium ferrous sulfate cathode material, and preparation method and application thereof

US12623918B2US 12623918 B2US12623918 B2US 12623918B2US-12623918-B2

Abstract

The present disclosure belongs to the field of sodium batteries. Provided are a composite sodium ferrous sulfate cathode material, and a preparation method and application thereof. The composite sodium ferrous sulfate cathode material includes a core. A chemical formula of the core is Na x M y Fe z (PO 4 ) k (SO 4 ) (0.4-0.6)x O t , where M includes at least one of manganese, vanadium, or titanium, 16≤x≤17, y=1, 4≤z≤5, 2≤k≤2.6, and y+z−0.1x−1.5k≤t≤y+z+0.1x−1.5k. According to the present disclosure, sulfate decomposition is reduced, the material performance of the composite sodium ferrous sulfate cathode material is improved, and a secondary battery using the composite sodium ferrous sulfate cathode material is improved in terms of performance such as cycling performance.

Inventors

  • Fei LV
  • Kai Gao
  • Qin Wang

Assignees

  • Hubei Wanrun New Energy Technology Co., Ltd.

Dates

Publication Date
20260512
Application Date
20240910

Claims (16)

  1. 1 . A composite sodium ferrous sulfate cathode material, comprising a core, wherein a chemical formula of the core is Na x M y Fe z (PO4) k (SO 4 ) (0.4-0.6)x O t , M comprises at least one of manganese, vanadium, or titanium, 16≤x≤17, y=1, 4≤z≤5, 2≤k≤2.6, and y+z−0.1x−1.5k≤t≤y+z+0.1x−1.5k.
  2. 2 . The composite sodium ferrous sulfate cathode material according to claim 1 , further comprising a carbon coating layer, wherein the carbon coating layer coats a surface of the core, and a molar ratio of a carbon element in the carbon coating layer to a sodium element in the core is greater than or equal to 0.5 and less than or equal to 1.
  3. 3 . The composite sodium ferrous sulfate cathode material according to claim 1 , wherein a sodium ion diffusion coefficient of the composite sodium ferrous sulfate cathode material is 1*10 −10 cm 2 /s-5*10 −10 cm 2 /s; and the powder resistivity of the composite sodium ferrous sulfate cathode material is 15 Ω·cm-25 Ω·cm.
  4. 4 . A method for preparing a composite sodium ferrous sulfate cathode material, comprising the following steps: mixing a ferrous iron source, a sodium source, a phosphorus source, a dopant, a reducing agent, and a first solvent to obtain a first slurry; performing a hydrothermal reaction on the first slurry, and then performing filtration and washing to obtain a washed material; mixing the washed material, a sulfate compound, a carbon source, and a second solvent to obtain a second slurry; and drying and calcining the second slurry, and then performing pulverization and impurity removal to obtain a composite sodium ferrous sulfate cathode material.
  5. 5 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein in the first slurry, the dopant comprises a doped element, and a molar ratio of the doped element to an iron element, a sodium element, and a phosphorus element is 1:(4-5):(16.0-17.0):(2-2.6); and/or a molar ratio of an iron element in the ferrous iron source to the reducing agent is 1:(0.1-0.3); and/or a solid content of the first slurry is 25%-35%; and/or a molar ratio of a sodium element in the washed material to the carbon source is 1:(0.5-1); and/or a solid content of the second slurry is 20%-30%.
  6. 6 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein the ferrous iron source comprises at least one of ferrous acetate or ferrous phosphate; and/or the sodium source comprises at least one of sodium hydroxide, sodium oxide, sodium carbonate, sodium acetate, or sodium phosphate; and/or the phosphorus source comprises sodium phosphate; and/or the reducing agent comprises sodium phosphite; and/or the dopant comprises at least one of a manganese source, a vanadium source, or a titanium source; and/or the carbon source comprises at least one of graphene or a carbon nanotube; and/or the sulfate compound comprises sulfuric acid and ammonium sulphate; in the second slurry, a molar ratio of a sodium element in the washed material to the sulfuric acid is 1:(0.3-0.4); and/or a molar ratio of the sodium element in the washed material to the ammonium sulphate is 1:(0.1-0.2).
  7. 7 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein a temperature of the hydrothermal reaction is 200° C.-300° C., a time for the hydrothermal reaction is 12 h-15 h, and pressure of the hydrothermal reaction is 1.5 MPa-2 MPa.
  8. 8 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein the hydrothermal reaction is performed while stirring, and a stirring speed is 200 r/min-300 r/min.
  9. 9 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein in the step of drying and calcining the second slurry, a calcining temperature is 300° C.-350° C., a calcining time is 4 h-8 h, and calcining is performed under a protective atmosphere.
  10. 10 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein in the calcining process, a heating rate is 1° C./min-2° C./min, and a cooling rate is 2° C./min-4° C./min.
  11. 11 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein spray drying is used for drying, an inlet air temperature for spray drying is 150° C.-350° C., and an outlet air temperature is 70° C.-95° C.
  12. 12 . The method for preparing a composite sodium ferrous sulfate cathode material according to claim 4 , wherein airflow pulverization is used for pulverization, a protective gas is used as a gas source for pulverization, and an air pressure is 0.5 MPa-0.8 MPa.
  13. 13 . A cathode plate, comprising the composite sodium ferrous sulfate cathode material according to claim 1 .
  14. 14 . A secondary battery, comprising the cathode plate according to claim 13 .
  15. 15 . The composite sodium ferrous sulfate cathode material according to claim 2 , a mass fraction of the carbon coating layer in the composite sodium ferrous sulfate cathode material is 5% to 10%.
  16. 16 . The composite sodium ferrous sulfate cathode material according to claim 1 , the chemical formula of the composite sodium ferrous sulfate cathode material is Na 16.6 MnFe 4.5 (PO 4 ) 2.3 (SO 4 ) 8.3 O 2.05 /C, Na 16 MnFe 4 (PO 4 ) 2 (SO 4 ) 6.4 O 3.6 /C, Na 17 MnFe 5 (PO 4 ) 2.6 (SO 4 ) 9.35 O 0.85 /C, Na 16.6 VFe 4.5 (PO 4 ) 2.3 (SO 4 ) 8.3 O 2.05 /C, or Na 16.6 TiFe 4.5 (PO 4 ) 2.3 (SO 4 ) 8.3 O 3.05 /C.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Chinese Patent Application No. 2024111909789 filed to the China National Intellectual Property Administration on Aug. 27, 2024 and entitled “Composite Sodium Ferrous Sulfate Cathode Material, and Preparation Method and Application Thereof”, the disclosure of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present disclosure relates to the technical field of sodium batteries, and specifically to a composite sodium ferrous sulfate cathode material, and a preparation method and application thereof. BACKGROUND With the development of lithium batteries, lithium has gradually become a bottleneck resource for new energy development. As an element in the same main group, sodium element has a electrochemical property very close to the lithium, has abundant reserves, has a crustal abundance of about 2.64%, and is cheaper in cost. Therefore, the use of sodium to replace the lithium to develop sodium-ion batteries has a very wide application prospect, and searching and developing an appropriate electrode material has become one of the main tasks in researching the sodium-ion batteries. A polyanionic sodium battery material has the characteristics of being low in cost, excellent in cycling performance, etc. The research of a cathode material for sodium ion batteries also focuses on a polyanionic material. Among numerous polyanionic compounds, SO42− has higher electronegativity and a stronger inductive effect, such that a working voltage of a sulfate material is higher, thereby receiving more attentions. Since sodium ferrous sulfate is lower in sintering temperature and low in energy consumption, in the polyanionic material, the polyanion cost of a sulfate series is lower. When the sodium ferrous sulfate is used as the cathode material for sodium ion batteries, compared to a LiFePO4 cathode material, a charging and discharging platform of a battery is higher. However, the sodium ferrous sulfate material has the disadvantages of being relatively low in electronic conductivity and sodium ion diffusion coefficient, which limit the actual application of the material. In the related art, the ionic conductivity of the cathode material for polyanionic sodium batteries is generally increased by doping metal ions, and the electronic conductivity of the material is increased by means of carbon coating. In conventional doping methods, doped metal salts and an iron salt are generally mixed and ground first, and then the mixture is sintered. However, the cathode material obtained by the above solution is poor in electrical performance, the reason is that a sintering temperature of the cathode material cannot exceed 350° C. to prevent the decomposition of sulfate in a necessary raw material, but at the above temperature, an ion diffusion rate is slow, and it is difficult to achieve the formation of a uniformly-mixed eutectic body of the doped metal and iron. Therefore, it is necessary to provide a solution that reduces sulfate decomposition and improve the material performance of a composite sodium ferrous sulfate cathode material. SUMMARY In view of the technical problems in the BACKGROUND, the present disclosure provides a composite sodium ferrous sulfate cathode material, and a preparation method and application thereof, to solve the technical problem of how to reduce sulfate decomposition to improve the material performance of a composite sodium ferrous sulfate cathode material. In a first aspect, an embodiment of the present disclosure provides a composite sodium ferrous sulfate cathode material, including a core-, where a chemical formula of the core is NaxMyFez(PO4)k(SO4)(0.4-0.6)xOt, where M includes at least one of manganese, vanadium, or titanium, 16≤x≤17, y=1, 4≤z≤5, 2≤k≤2.6, and y+z−0.1x−1.5k≤t≤y+z+0.1x−1.5k. In the technical solution of this embodiment of the present disclosure, the ionic conductivity of the composite sodium ferrous sulfate cathode material is increased through element doping, and ensures a sodium ion diffusion coefficient, moreover, a retention degree of sulfate is high, and iron and doped metal forms a uniform core, so as to achieve further improvement of the performance of the composite sodium ferrous sulfate cathode material. In some embodiments, the composite sodium ferrous sulfate cathode material further includes a carbon coating layer, where the carbon coating layer coats a surface of the core, and a molar ratio of a carbon element in the carbon coating layer to a sodium element in the core is greater than or equal to 0.5 and less than or equal to 1. In these embodiments, the electron conductivity of the material is increased through a carbon-coated core-shell structure. In some embodiments, a sodium ion diffusion coefficient of the composite sodium ferrous sulfate cathode material is 1*10−10 cm2/s-5*10−10 cm2/s; and the powder resistivity is 15 Ω·cm-25 Ω·cm. In these embodiments, the sodium i