Search

CN-118630153-B - Positive electrode active material, method for producing same, secondary battery, and electricity-using device

CN118630153BCN 118630153 BCN118630153 BCN 118630153BCN-118630153-B

Abstract

The application provides a positive electrode active material, a preparation method thereof, a secondary battery and an electric device. The positive electrode active material comprises a polyanion compound with a general formula shown in a formula I, wherein the crystallinity of the positive electrode active material is 0.8-1, M comprises at least one of Mg, al, sc, ti, V, cr, mn, fe, co, ni, cu, zn, zr, nb, mo, sn, hf, ta, W and Pb, x is more than or equal to 1 and less than or equal to 7, y 1 +y 2 is more than or equal to 1 and less than or equal to 4, z is more than or equal to 1 and less than or equal to 2, and k is more than or equal to 1 and less than or equal to 4. The positive electrode active material has higher crystallinity, and is beneficial to improving the first discharge capacity of the battery.

Inventors

  • YANG HUILING
  • ZHAO YUZHEN
  • XU YUE
  • GUAN YINGJIE
  • WEN YAN
  • HUANG QISEN

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260505
Application Date
20230310

Claims (20)

  1. 1. A positive electrode active material is characterized in that the positive electrode active material comprises a polyanion compound with a general formula shown in a formula I, the crystallinity of the positive electrode active material is 0.8-1, Na x Fe y1 M y2 (PO 4 ) z (P 2 O 7 ) k formula I Wherein M comprises at least one of Mg, al, sc, ti, V, cr, mn, co, ni, cu, zn, zr, nb, mo, sn, hf, ta, W and Pb; x is more than or equal to 1 and less than or equal to 7,1 y 1 +y 2 is less than or equal to y is less than or equal to 1 +y 2 is less than or equal to.
  2. 2. The positive electrode active material according to claim 1, wherein a ratio Id of (602) peak intensity to (022) peak intensity in an XRD diffraction spectrum of the positive electrode active material is 0.9 to 1.5.
  3. 3. The positive electrode active material according to claim 1 or 2, further comprising a carbon material located on at least part of the surface of the polyanion compound primary particle.
  4. 4. The positive electrode active material according to any one of claims 1 to 3, wherein 1≤x≤7, 1≤y 1 +y 2 ≤4, 1≤z≤2, 1≤k≤4, and 0≤y 2 <4.
  5. 5. The positive electrode active material according to any one of claims 1 to 4, wherein 1≤x≤4, 1≤y 1 +y 2 ≤3, 1≤z≤2, 1≤k≤2, and y 2 is 0.
  6. 6. The positive electrode active material according to any one of claims 1 to 5, wherein M comprises at least one of Mg, al, V, mn.
  7. 7. The positive electrode active material according to any one of claims 1 to 6, wherein the positive electrode active material comprises at least one of Na 3.98 Fe 3 (PO 4 ) 2 P 2 O 7 、Na 4 Fe 2.8 (PO 4 ) 2 P 2 O 7 、Na 3.98 Fe 2.8 (PO 4 ) 2 P 2 O 7 、Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 .
  8. 8. A method for preparing a positive electrode active material, comprising the steps of: Mixing a raw material containing a sodium source, an iron source and a phosphorus source with a solvent to obtain mixed slurry, wherein the raw material also comprises an M source; Drying and calcining the mixed slurry to obtain a positive electrode active material, wherein the positive electrode active material comprises a polyanion compound with a general formula shown in a formula I, the crystallinity of the positive electrode active material is 0.8-1, Na x Fe y1 M y2 (PO 4 ) z (P 2 O 7 ) k formula I Wherein M comprises at least one of Mg, al, sc, ti, V, cr, mn, co, ni, cu, zn, zr, nb, mo, sn, hf, ta, W and Pb; x is more than or equal to 1 and less than or equal to 7,1 y 1 +y 2 is less than or equal to y is less than or equal to 1 +y 2 is less than or equal to.
  9. 9. The method for producing a positive electrode active material according to claim 8, wherein 1≤x≤7, 1≤y 1 +y 2 ≤4, 1≤z≤2, 1≤k≤4, and 0≤y 2 <4.
  10. 10. The method for producing a positive electrode active material according to claim 8 or 9, wherein 1≤x≤4, 1≤y 1 +y 2 ≤3, 1≤z≤2, 1≤k≤2, and y 2 is 0.
  11. 11. The method for producing a positive electrode active material according to any one of claims 8 to 10, wherein M includes at least one of Mg, al, V, mn.
  12. 12. The method for producing a positive electrode active material according to any one of claims 8 to 11, wherein the positive electrode active material comprises at least one of Na 3.98 Fe 3 (PO 4 ) 2 P 2 O 7 、Na 4 Fe 2.8 (PO 4 ) 2 P 2 O 7 、Na 3.98 Fe 2.8 (PO 4 ) 2 P 2 O 7 、Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 .
  13. 13. The method for producing a positive electrode active material according to any one of claims 8 to 12, wherein the step of mixing a raw material containing a sodium source, an iron source, and a phosphorus source with a solvent to obtain a mixed slurry specifically comprises: Adding a raw material containing a sodium source, ferrous oxalate and a phosphorus source into a solvent, stirring and grinding to obtain mixed slurry, wherein the mixed slurry is subjected to a homogenizing shear rate of 300S -1 ~900 S -1 .
  14. 14. The method for producing a positive electrode active material according to any one of claims 8 to 13, wherein the median particle diameter Dv50 of the particles in the mixed slurry is 0.05 μm to 1.5 μm.
  15. 15. The method for producing a positive electrode active material according to any one of claims 8 to 14, wherein the median particle diameter Dv50 of the particles in the mixed slurry is 0.1 μm to 0.7 μm.
  16. 16. The method for producing a positive electrode active material according to any one of claims 8 to 15, wherein the solid content of the mixed slurry is 15% to 50%.
  17. 17. The method for producing a positive electrode active material according to claim 16, wherein the solid content of the mixed slurry is 25% to 40%.
  18. 18. The method of any one of claims 8 to 17, wherein the mixed slurry comprises a carbon source.
  19. 19. The method for producing a positive electrode active material according to claim 18, characterized in that the method for producing comprises: Adding a raw material containing a sodium source, ferrous oxalate and a phosphorus source into a solvent, stirring and grinding until the median particle diameter Dv50 of particles in the slurry is 0.1-1.3 mu m, and mixing with a carbon source to obtain a mixed slurry.
  20. 20. The method for producing a positive electrode active material according to claim 19, characterized in that the method for producing comprises: Adding a raw material containing a sodium source, ferrous oxalate and a phosphorus source into a solvent, stirring and grinding until the median particle diameter Dv50 of particles in the slurry is 0.1-0.7 mu m, and mixing with a carbon source to obtain a mixed slurry.

Description

Positive electrode active material, method for producing same, secondary battery, and electricity-using device Technical Field The application relates to the technical field of secondary batteries, in particular to a positive electrode active material, a preparation method thereof, a secondary battery and an electric device. Background Sodium batteries have great potential for large-scale energy storage due to their abundant reserves, low price and wide operating temperature. Iron-based polyanion compounds are considered as a type of electrode material with the most promising application prospect in terms of excellent structural stability, safety and suitable voltage plateau. However, there are still problems with sodium batteries using iron-based polyanion compounds as positive electrode materials. The application requirements of the new generation electrochemical system cannot be met. Disclosure of Invention The present application has been made in view of the above problems, and an object of the present application is to provide a positive electrode active material having a high crystallinity, which is advantageous in improving the first discharge capacity of a battery. In a first aspect of the present application, there is provided a positive electrode active material comprising a polyanion compound having a general formula represented by formula I, the positive electrode active material having a crystallinity of 0.8 to 1, Na xFey1My2(PO4)z(P2O7)k formula I Wherein M comprises at least one of Mg, al, sc, ti, V, cr, mn, fe, co, ni, cu, zn, zr, nb, mo, sn, hf, ta, W and Pb; x is more than or equal to 1 and less than or equal to 7, 1y 1+y2 is less than or equal to y is less than or equal to 1+y2 is less than or equal to. The positive electrode active material with the crystallinity of 0.8-1 is beneficial to improving the first discharge capacity of the battery, so that the battery has higher charging capacity and the performance of the battery is improved. In any embodiment, the ratio Id of the (602) peak intensity to the (022) peak intensity in the XRD diffraction spectrum of the positive electrode active material is 0.9-1.5. The applicant has unexpectedly found that the higher the ratio Id of (602) peak intensity to (022) peak intensity in the XRD diffraction spectrum, the more excellent the electrochemical performance of the positive electrode active material. In any embodiment, the positive electrode active material further comprises a carbon material located on at least a portion of the surface of the polyanionic compound primary particle. The carbon material is positioned on the surface of the primary particles, so that the problem of poor conductivity of the iron-based polyanion compound can be remarkably improved, and the electrochemical performance of the positive electrode active material can be greatly improved. A second aspect of the present application provides a method for preparing a positive electrode active material, comprising the steps of: Mixing a raw material containing a sodium source, an iron source and a phosphorus source with a solvent to obtain mixed slurry, wherein the raw material also comprises an M source; Drying and calcining the mixed slurry to obtain a positive electrode active material, wherein the positive electrode active material comprises a polyanion compound with a general formula shown in a formula I, the crystallinity of the positive electrode active material is 0.8-1, Na xFey1My2(PO4)z(P2O7)k formula I Wherein M comprises at least one of Mg, al, sc, ti, V, cr, mn, fe, co, ni, cu, zn, zr, nb, mo, sn, hf, ta, W and Pb; x is more than or equal to 1 and less than or equal to 7, 1y 1+y2 is less than or equal to y is less than or equal to 1+y2 is less than or equal to. The positive electrode active material with the crystallinity of 0.8-1 is beneficial to improving the first discharge capacity of the battery, so that the battery has higher charging capacity and the performance of the battery is improved. In any embodiment, the step of mixing the raw materials including the sodium source, the iron source, and the phosphorus source with the solvent to obtain the mixed slurry specifically includes: And adding the raw materials containing the sodium source, the ferrous oxalate and the phosphorus source into a solvent, stirring and grinding to obtain mixed slurry, wherein the mixed slurry is subjected to a homogeneous shear rate of 300S -1～900S-1. The stirring homogeneous shear rate is controlled to be 300S -1～900S-1, and the high homogeneous shear rate is beneficial to avoiding or reducing the precursor generated by the reaction of the sodium source, the phosphorus source and the ferrous oxalate from wrapping unreacted ferrous oxalate, so that the unreacted ferrous oxalate is convenient to be fully exposed to fully react, and the crystallinity of the positive electrode active material is improved. In any embodiment, the median particle diameter Dv50 of the particles in the m