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US-20260125265-A1 - COMPOSITE POSITIVE ELECTRODE MATERIAL, PREPARATION METHOD THEREFOR AND USE THEREOF

US20260125265A1US 20260125265 A1US20260125265 A1US 20260125265A1US-20260125265-A1

Abstract

A composite positive electrode material, a preparation method thereof and a use thereof, where the composite positive electrode material includes an inner core and a carbon coating layer covering at least part of a surface of the inner core and/or embedded in the inner core; the inner core includes NaFePO 4 and a compound represented by Formula 1; Na 4+x Fe 3-y (PO 4 ) 2+z P 2 O 7 Formula 1; in Formula 1, −0.15≤x≤0.8, 0≤y≤0.5, and −0.2≤z≤0.2; and a crystal size of NaFePO 4 is ≤100 nm. The composite positive electrode material, when used in batteries, can improve the capacity and rate capability of the batteries.

Inventors

  • Xueying Wang
  • Xufeng YAN
  • Rui Liu

Assignees

  • NINGBO RONBAY NEW ENERGY TECHNOLOGY Co.,Ltd.

Dates

Publication Date
20260507
Application Date
20251229
Priority Date
20230629

Claims (20)

  1. 1 . A composite positive electrode material, comprising an inner core and a carbon coating layer covering at least part of a surface of the inner core and/or embedded in the inner core; wherein the inner core comprises NaFePO 4 and a compound represented by Formula 1; in Formula 1, −0.15≤x≤0.8, 0≤y≤0.5, −0.2≤z≤0.2; and a crystal size of NaFePO 4 is ≤100 nm.
  2. 2 . The composite positive electrode material according to claim 1 , wherein an atomic ratio of Fe to P gradually decreases from (0.9-1.1):1 in the composite positive electrode material from outside to inside, and then stabilizes at (0.65-0.85):1; and/or, an atomic ratio of Fe to Na gradually decreases from (0.9-1.1):1 in the composite positive electrode material from outside to inside, and then stabilizes at (0.65-0.85):1.
  3. 3 . The composite positive electrode material according to claim 1 , wherein a mass percentage content of the carbon coating layer is 0.5-5% based on a total mass of the composite positive electrode material.
  4. 4 . The composite positive electrode material according to claim 2 , wherein a mass percentage content of the carbon coating layer is 0.5-5% based on a total mass of the composite positive electrode material.
  5. 5 . The composite positive electrode material according to claim 1 , wherein a molar ratio of PO 4 3− to P 2 O 7 4− in the composite positive electrode material is (1.5-3):1.
  6. 6 . The composite positive electrode material according to claim 2 , wherein a molar ratio of PO 4 3− to P 2 O 7 4− in the composite positive electrode material is (1.5-3):1.
  7. 7 . The composite positive electrode material according to claim 3 , wherein a molar ratio of PO 4 3− to P 2 O 7 4− in the composite positive electrode material is (1.5-3):1.
  8. 8 . The composite positive electrode material according to claim 1 , wherein a particle size of the inner core is 100-900 nm; and/or, a specific surface area of the composite positive electrode material is 5-20 m 2 g −1 ; and/or, a compaction density of the composite positive electrode material is 1.9-2.4 g cm −3 .
  9. 9 . The composite positive electrode material according to claim 2 , wherein a particle size of the inner core is 100-900 nm; and/or, a specific surface area of the composite positive electrode material is 5-20 m 2 g −1 ; and/or, a compaction density of the composite positive electrode material is 1.9-2.4 g cm −3 .
  10. 10 . The composite positive electrode material according to claim 3 , wherein a particle size of the inner core is 100-900 nm; and/or, a specific surface area of the composite positive electrode material is 5-20 m 2 g −1 ; and/or, a compaction density of the composite positive electrode material is 1.9-2.4 g cm −3 .
  11. 11 . The composite positive electrode material according to claim 4 , wherein a particle size of the inner core is 100-900 nm; and/or, a specific surface area of the composite positive electrode material is 5-20 m 2 g −1 ; and/or, a compaction density of the composite positive electrode material is 1.9-2.4 g cm −3 .
  12. 12 . A preparation method of the composite positive electrode material according to claim 1 , comprising performing a sand milling treatment and a spray drying treatment in sequence on a raw material system comprising a sodium source, an iron source, a phosphorus source and a carbon source, to obtain a powder; and performing a first calcination treatment, a second calcination treatment, a third calcination treatment and a fourth calcination treatment on the powder in sequence, to obtain the composite positive electrode material; wherein in the raw material system, a molar proportion a of sodium element, a molar proportion b of iron element, and a molar proportion c of phosphorus element satisfy: 3.85≤a≤4.8; 2.5≤b≤3; and 3.8≤c≤4.2; in the first calcination treatment, a temperature is 255-260° C. and a time is 1-2 h; in the second calcination treatment, a temperature is 300-320° C. and a time is 3-5 h; in the third calcination treatment, a temperature is 370-390° C. and a time is 1-2 h; and in the fourth calcination treatment, a temperature is 470-500° C. and a time is 8-10 h.
  13. 13 . The preparation method according to claim 12 , wherein the sodium source and also the iron source and the carbon sources simultaneously contain sodium ferric ethylenediaminetetraacetate.
  14. 14 . The preparation method according to claim 12 , wherein the sand milling treatment comprises a first sand milling treatment and a second sand milling treatment; and a particle size of a sand milling agent in the second sand milling treatment is smaller than a particle size of a sand milling agent in the first sand milling treatment.
  15. 15 . The preparation method according to claim 14 , wherein in the first sand milling treatment, a rotational speed is 900-1200 rpm and a time is 2-3 h; and/or, in the second sand milling treatment, a rotational speed is 400-2000 rpm and a time is 1-2 h.
  16. 16 . The preparation method according to claim 12 , wherein the carbon source comprises an organic carbon source.
  17. 17 . The preparation method according to claim 16 , wherein the carbon source further comprises an inorganic carbon source; and a mass ratio of the organic carbon source to the inorganic carbon source is (12.5-30):1.
  18. 18 . The preparation method according to claim 17 , wherein the raw material system further comprises a coupling agent; and a mass percentage content of the coupling agent is 1-3% based on a total mass of the raw material system.
  19. 19 . The preparation method according to claim 18 , wherein the coupling agent is a titanic acid ester coupling agent.
  20. 20 . A battery, comprising the composite positive electrode material according to claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Application No. PCT/CN2024/101442, filed on Jun. 25, 2024, which claims priority to Chinese Patent Application No. 202310793176.6 filed with China National Intellectual Property Administration on Jun. 29, 2023. Both of the aforementioned applications are hereby incorporated by reference in their entireties. TECHNICAL FIELD Embodiments of the present application relate to a composite positive electrode material, a preparation method thereof and a use thereof, belonging to the technical field of secondary batteries. BACKGROUND Compared with lithium resources, sodium resources are abundant and low-cost, and thus the industry is increasingly inclined to research sodium-ion batteries. Sodium iron phosphate-pyrophosphate (NFPP) is considered one of the most industrially promising positive electrode materials for sodium-ion batteries due to its low cost and excellent structural stability. However, NFPP has low electronic conductivity. To improve the electronic conductivity of NFPP, existing technologies mainly employ carbon coating on NFPP. Nevertheless, at present, the composite positive electrode materials with carbon-coated NFPP still have the problems of low capacity and poor rate capability. SUMMARY The present application provides a composite positive electrode material, which, when used in batteries, can improve the capacity and rate capability of the batteries. The present application provides a preparation method of a composite positive electrode material, which preparation method may prepare the above composite positive electrode material, has a simple preparation process, and is suitable for wide popularization and application. The present application provides a battery, which includes the above composite positive electrode material, and thus has excellent rate capability, cycling performance, and discharge specific capacity. The present application provides a composite positive electrode material, including an inner core and a carbon coating layer covering at least part of a surface of the inner core and/or embedded in the inner core; where the inner core includes NaFePO4 and a compound represented by Formula 1; in Formula 1, −0.15≤x≤0.8, 0≤y≤0.5, −0.2≤z≤0.2; anda crystal size of NaFePO4 is ≤100 nm. In the composite positive electrode material as described above, an atomic ratio of Fe to P in the composite positive electrode material gradually decreases from (0.9-1.1):1 from outside to inside and then stabilizes at (0.65-0.85):1; and/or, an atomic ratio of Fe to Na in the composite positive electrode material gradually decreases from (0.9-1.1):1 from outside to inside and then stabilizes at (0.65-0.85):1. In the composite positive electrode material as described above, based on a total mass of the composite positive electrode material, a mass percentage content of the carbon coating layer is 0.5-5%. In the composite positive electrode material as described above, a molar ratio of PO43− to P2O74− is (1.5-3):1. In the composite positive electrode material as described above, a particle size of the inner core is 100-900 nm. In the composite positive electrode material as described above, a specific surface area of the composite positive electrode material is 5-20 m2 g−1. In the composite positive electrode material as described above, a compaction density of the composite positive electrode material is 1.9-2.4 g cm−3. The present application provides a preparation method of the composite positive electrode material as described above, including: performing a sand milling treatment and a spray drying treatment in sequence on a raw material system including a sodium source, an iron source, a phosphorus source and a carbon source, to obtain a powder; andperforming a first calcination treatment, a second calcination treatment, a third calcination treatment and a fourth calcination treatment on the powder in sequence, to obtain the composite positive electrode material;where in the raw material system, a molar proportion a of sodium element, a molar proportion b of iron element, and a molar proportion c of phosphorus element satisfy: 3.85≤a≤4.8; 2.5≤b≤3; and 3.8≤c≤4.2;in the first calcination treatment, a temperature is 255-260° C. and a time is 1-2 h;in the second calcination treatment, a temperature is 300-320° C. and a time is 3-5 h;in the third calcination treatment, a temperature is 370-390° C. and a time is 1-2 h; andin the fourth calcination treatment, a temperature is 470-500° C. and a time is 8-10 h. In the preparation method as described above, the sodium source and the iron source are simultaneously sodium ferric ethylenediaminetetraacetate (Sodium Ferric EDTA). In the preparation method as described above, the sand milling treatment includes a first sand milling treatment and a second sand milling treatment; a particle size of a sand milling agent in the second sand milling treatment is smaller than a partic