Search

CN-122000329-A - Secondary battery, method for manufacturing the same, and power consumption device

CN122000329ACN 122000329 ACN122000329 ACN 122000329ACN-122000329-A

Abstract

The application provides a secondary battery, a preparation method thereof and an electric device. In particular, the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the positive electrode sheet comprising a positive electrode active material comprising lithium iron manganese phosphate particles and first lithium iron phosphate particles, the primary average particle diameter of the lithium iron manganese phosphate particles being 120 to 600nm, the area ratio of the first lithium iron phosphate particles being 2 to 30% and the area ratio of the lithium iron manganese phosphate particles being 70 to 98% based on the total area of the positive electrode active material in the cross section of the positive electrode sheet.

Inventors

  • BIE CHANGFENG
  • CHEN XUDONG
  • HUANG YANG
  • LIN ZILONG
  • Du Wanying
  • WU YICHEN
  • LIU HUAIWEN
  • NI HUAN
  • LIU NA

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260508
Application Date
20240108

Claims (18)

  1. 1. The secondary battery is characterized by comprising a positive electrode plate, a negative electrode plate, a separation film and electrolyte, wherein the positive electrode plate comprises a positive electrode active material, the positive electrode active material comprises lithium iron manganese phosphate particles and first lithium iron phosphate particles, and the primary average particle size of the lithium iron manganese phosphate particles is 120-600 nm; the first lithium iron phosphate particles have an area ratio of 2% to 30% and the lithium iron manganese phosphate particles have an area ratio of 70% to 98% based on the total area of the positive electrode active material in the cross section of the positive electrode sheet.
  2. 2. The secondary battery according to claim 1, wherein the primary average particle diameter s1 of the first lithium iron phosphate particles satisfies 500 nm≤s1≤3000 nm.
  3. 3. The secondary battery according to claim 1 or 2, wherein the positive electrode active material further comprises second lithium iron phosphate particles, and a primary average particle diameter s2 of the second lithium iron phosphate particles satisfies 30 nm≤s2≤200nm.
  4. 4. The secondary battery according to claim 3, wherein the second lithium iron phosphate particles have an area ratio of 1 to 10%, the first lithium iron phosphate particles have an area ratio of 2 to 25%, and the lithium manganese iron phosphate particles have an area ratio of 70 to 97% based on the total area of the positive electrode active material in the cross section of the positive electrode sheet.
  5. 5. The secondary battery of any one of claims 1-4, wherein the lithium iron manganese phosphate particles have a molecular formula Li m Fe x Mn r P y O j Q q , wherein Q includes at least one of Al, na, K, mg, cu, cr, zn, pb, ca, co, ni, sr, nb, V, ti, B, S, si, N, F, cl, br, 0.95 ∈m ∈1.15, x >0, r >0,0.9 +≤x+r +≤ 1,0.95 +≤y +≤ 1,3.5 +≤j +.4, 0 +.q +.0.1, and/or The first lithium iron phosphate particles have the formula Li m1 Fe x1 P y1 O j1 Q1 q1 , where Q1 includes at least one of Al, na, K, mg, cu, mn, cr, zn, pb, ca, co, ni, sr, nb, V, ti, B, S, si, N, F, cl, br, m1 is more than or equal to 0.95 and less than or equal to 1.15,0.9, x1 is more than or equal to 1,0.95 y1 is less than or equal to 1,3.5, j1 is less than or equal to 4,0< q1 is less than or equal to 0.1, and/or The second lithium iron phosphate particles have a molecular formula Li m2 Fe x2 P y2 O j2 Q2 q2 , wherein Q2 includes at least one of Al, na, K, mg, cu, mn, cr, zn, pb, ca, co, ni, sr, nb, V, ti, B, S, si, N, F, cl, br, m2 is more than or equal to 0.95 and less than or equal to 1.15,0.9 and x2 is more than or equal to 1, y2 is more than or equal to 0.95 and less than or equal to 1,3.5 and less than or equal to j2 and less than or equal to 4, and Q2 is more than or equal to 0 and less than or equal to 0.1.
  6. 6. The secondary battery according to claim 5, wherein in the first lithium iron phosphate particles, the Q1 includes at least one of Ti, V, mg, nb, and the content of Ti, V, mg, and/or Nb is 1000 to 10000ppm based on the total weight of the first lithium iron phosphate particles.
  7. 7. The secondary battery according to any one of claims 1 to 6, wherein the specific surface area of the first lithium iron phosphate particles is 3m 2 /g-8 m 2 /g.
  8. 8. The secondary battery according to any one of claims 1 to 7, wherein the carbon content of the first lithium iron phosphate particles is Cx1 wt%, based on the total weight of the first lithium iron phosphate particles, wherein 0.8≤cx1≤2.0.
  9. 9. The secondary battery according to any one of claims 3 to 8, wherein the primary average particle diameter of the lithium iron phosphate particles is 150 to 210nm, the primary average particle diameter s1 of the first lithium iron phosphate particles satisfies 870 nm≤s1≤3000 nm, and/or the primary average particle diameter s2 of the second lithium iron phosphate particles satisfies 60 nm≤s2≤200 nm.
  10. 10. The secondary battery according to any one of claims 1 to 9, wherein the capacity of the first lithium iron phosphate particles is equal to or greater than 88%, the η being defined as: And (3) charging and discharging the battery taking the first lithium iron phosphate particles as the positive electrode active material twice under a constant current with the multiplying power of 0.1C within the voltage range of 2.0V-3.75V, and then charging and discharging once under a constant current with the multiplying power of 1C, wherein in a charging and discharging test with the multiplying power of 1C, the capacity value of extracting and discharging voltage of 3.2V is recorded as C1, the capacity value of extracting and discharging to 2.0V is C2, and eta=C1/C2, wherein the charging process comprises constant voltage charging, constant voltage is 3.75V, and constant voltage cut-off current is 50 mu A.
  11. 11. The secondary battery according to any one of claims 1 to 10, wherein the first lithium iron phosphate particles satisfy at least one of (a) to (f): (a) The Dv10 of the first lithium iron phosphate particles is more than or equal to 0.2 mu m; (b) The Dv50 of the first lithium iron phosphate particles is 0.5-5 mu m; (c) The Dv90 of the first lithium iron phosphate particles is less than or equal to 10 mu m; (d) The Dv99 of the first lithium iron phosphate particles is less than or equal to 12 mu m; (e) The powder compaction density of the first lithium iron phosphate at the pressure of 3 tons is more than or equal to 2.25g/cm 3 ; (f) The first lithium iron phosphate has a powder resistivity of less than 60 Ω -cm.
  12. 12. The secondary battery according to any one of claims 3 to 11, wherein the aspect ratio of the second lithium iron phosphate particles is 1.3 or more.
  13. 13. The secondary battery according to any one of claims 3 to 12, wherein a ratio W of (020) crystal plane diffraction peak intensity to (211) crystal plane diffraction peak intensity of the second lithium iron phosphate particles is not less than 1.03.
  14. 14. The secondary battery according to any one of claims 1 to 14, wherein a manganese elution amount of the secondary battery is 50ppm or less.
  15. 15. The secondary battery according to any one of claims 1 to 14, wherein the first lithium iron phosphate particles are mainly obtained by the following production method: Providing a raw material containing at least a lithium source, an iron source, a phosphorus source, a carbon film forming agent, a carbon source and a modifier, and performing sintering at least twice, The temperature of the first sintering is 500-760 ℃; the temperature of the second sintering is 700-800 ℃.
  16. 16. The secondary battery according to claim 15, wherein the first lithium iron phosphate particles are mainly obtained by the following production method: Providing a raw material containing at least a lithium source, an iron source, a phosphorus source, a carbon film forming agent and a modifier, and performing sintering at least twice, The carbon content of the material after the first sintering is 0.01-0.79 wt%; The carbon content of the material after the second sintering is 0.8-2.0 wt%.
  17. 17. The secondary battery according to claim 15 or 16, wherein the preparation method of the first lithium iron phosphate particles comprises the steps of: performing first pulverization after performing the first sintering, performing second pulverization after performing the second sintering, wherein, The Dv50 of the product after the first crushing is 300nm-1200nm; The Dv50 of the product after the second crushing is 500nm-5000nm.
  18. 18. An electric device comprising the secondary battery according to any one of claims 1 to 17.

Description

Secondary battery, method for manufacturing the same, and power consumption device The application is based on the application number 202410027059.3, the application date 2024, 01 and 08, the application number Ningde, the new energy science and technology Co., ltd, the application name of which is 'secondary battery, its preparation method and electricity device'. Technical Field The application relates to the technical field of secondary batteries, in particular to a secondary battery, a preparation method thereof and an electric device. Background As a positive electrode active material of the lithium ion battery, the lithium iron manganese phosphate has higher voltage platform, theoretical energy density, theoretical specific capacity and lower cost than the lithium iron phosphate. However, lithium iron phosphate has a problem of poor storage performance at high temperature (60 ℃) as compared with lithium iron phosphate. Accordingly, it is desirable to provide a positive electrode active material comprising lithium iron manganese phosphate salts, which has good high temperature storage properties. Disclosure of Invention The present application has been made in view of the above problems, and an object thereof is to provide a secondary battery having excellent high-temperature storage performance, a method for producing the same, and an electric device. The inventors found that the above object can be achieved by adopting the technical solution of the present application. The first aspect of the application provides a secondary battery, which comprises a positive electrode plate, a negative electrode plate, a separation film and electrolyte, wherein the positive electrode plate comprises a positive electrode active material, the positive electrode active material comprises lithium iron manganese phosphate particles, the primary average particle size of the lithium iron manganese phosphate particles is 120-600nm, and the manganese leaching amount of the secondary battery is less than or equal to 50ppm. The secondary battery has better high-temperature storage performance. In addition, the secondary battery provided by the application has better high-temperature cycle performance and higher solid content of the positive electrode slurry. In any embodiment, the positive electrode active material further includes first lithium iron phosphate particles, and the primary average particle diameter s1 of the first lithium iron phosphate particles satisfies 500 nm≤s1≤3000 nm. When the positive electrode active material further comprises first lithium iron phosphate particles, and the primary average particle diameter s1 of the first lithium iron phosphate particles is less than or equal to 500nm and less than or equal to s1 and less than or equal to 3000nm, the secondary battery provided by the application has lower manganese leaching amount, better high-temperature storage performance, better high-temperature cycle performance and higher solid content of positive electrode slurry. In any embodiment, the first lithium iron phosphate particles have an area ratio of 2% to 30% and the lithium iron manganese phosphate particles have an area ratio of 70% to 98% based on the total area of the positive electrode active material in the cross section of the positive electrode sheet. In any embodiment, the positive electrode active material further includes second lithium iron phosphate particles, and the primary average particle diameter s2 of the second lithium iron phosphate particles satisfies 30 nm≤s2≤200 nm. When the positive electrode active material further comprises second lithium iron phosphate particles, and the primary average particle diameter s2 of the second lithium iron phosphate particles is more than or equal to 30nm and less than or equal to 200nm, the secondary battery provided by the application has lower manganese leaching amount, better high-temperature storage performance and better high-temperature cycle performance. In any embodiment, the area ratio of the second lithium iron phosphate particles is 1-10%, the area ratio of the first lithium iron phosphate particles is 2-25%, and the area ratio of the lithium manganese iron phosphate particles is 70% -97% based on the total area of the positive electrode active material in the cross section of the positive electrode sheet. In any embodiment, the lithium iron manganese phosphate particles have the formula Li mFexMnrPyOjQq, where Q includes at least one of Al, na, K, mg, cu, cr, zn, pb, ca, co, ni, sr, nb, V, ti, B, S, si, N, F, cl, br, 0.95≤m≤1.15, x >0, r >0, 0.9≤x+r≤1, 0.95≤y≤1, 3.5≤j≤4, 0≤q≤0.1, and/or The first lithium iron phosphate particles have the formula Li m1Fex1Py1Oj1Q1q1, wherein Q1 includes at least one of Al, na, K, mg, cu, mn, cr, zn, pb, ca, co, ni, sr, nb, V, ti, B, S, si, N, F, cl, br, 0.95≤m1≤ 1.15,0.9≤x1≤1, 0.95≤y1≤ 1,3.5≤j1≤4, 0< q1≤0.1, and/or The second lithium iron phosphate particles have the molecular formula Li m2Fex2Py2O