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CN-119852324-B - Secondary battery and electricity utilization device

CN119852324BCN 119852324 BCN119852324 BCN 119852324BCN-119852324-B

Abstract

The application provides a secondary battery and an electric device. The secondary battery comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on the surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium iron phosphate material doped with M element and Q element, M comprises one or more of Mn, ni, co, cr, cu, bi, sb, and Q comprises one or more of F, N, cl.

Inventors

  • JIANG JIHONG
  • LIU HONGYU
  • BIE CHANGFENG
  • LI XIAOJING
  • HE SIYUAN
  • NI HUAN

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260508
Application Date
20240531

Claims (7)

  1. 1. The secondary battery is characterized by comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on the surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the composition of the positive electrode active material comprises: LiFe 1-x M x PO y Q z , wherein x is more than or equal to 0.03 and less than or equal to 0.05,3.85, y is more than or equal to 4,0.0005 and z is more than or equal to 0.005, M comprises one or more of Mn, ni, co, cr, cu, and Q comprises one or more of F, cl.
  2. 2. The secondary battery according to claim 1, wherein, M comprises Mn, and Q comprises F.
  3. 3. The secondary battery according to claim 1, wherein, The positive electrode active material further includes a carbon element, and the mass content of the carbon element is 1.05% -1.35% based on the total mass of the positive electrode active material.
  4. 4. The secondary battery according to any one of claims 1 to 3, wherein the positive electrode active material satisfies at least one of the following conditions: (1) The unit cell parameters of the positive electrode active material are satisfied that a is more than or equal to 10.324A and less than or equal to 10.343A, b is more than or equal to 6.005A and less than or equal to 6.089A, c is more than or equal to 4.689A and less than or equal to 4.69A; (2) The unit cell volume V of the positive electrode active material is 290.718A 3 -292.168Å 3 ; (3) The Fe-O bond length L1 of the positive electrode active material is 2.080 A≤L1≤2.095A, and the P-O bond length L2 of the positive electrode active material is 1.533 A≤L2≤1.586A.
  5. 5. The secondary battery according to claim 1, wherein the positive electrode active material satisfies at least one of the following conditions: (1) The powder compaction density of the positive electrode active material meets 2.509g/cm 3 -2.571g/cm 3 ; (2) The particle distribution particle size D50 of the positive electrode active material satisfies 0.79-1.35 mu m; (3) The discharge gram capacity of the positive electrode active material at the discharge multiplying power of 0.1C is more than or equal to 158mAh/g.
  6. 6. The secondary battery according to claim 1, wherein the secondary battery has a discharge medium voltage of 3.396V-4.036V at a discharge rate of 0.1C.
  7. 7. An electric device, characterized in that the electric device comprises the secondary battery according to any one of claims 1 to 6.

Description

Secondary battery and electricity utilization device Technical Field The application relates to the technical field of lithium batteries, in particular to a secondary battery and an electric device. Background In recent years, along with the wider application range of lithium ion batteries, the lithium ion batteries are widely applied to energy storage power supply systems such as hydraulic power, firepower, wind power, solar power stations and the like, and a plurality of fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like. The improvement of the energy density of the secondary battery often comes at the expense of the rate performance and the cycle stability, and how to synchronously improve the energy density, the rate performance and the cycle stability of the secondary battery is a technical problem to be solved in the field. 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 and an electric device. The first aspect of the application provides a secondary battery, which comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on the surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium iron phosphate material doped with M element and Q element, M comprises one or more of Mn, ni, co, cr, cu, bi, sb, and Q comprises one or more of F, N, cl. The doped element Q in the positive electrode active material can replace oxygen on oxygen position in lithium iron phosphate to distort a cell, enlarge the volume of the cell, enlarge migration channels of lithium ions, improve the rate performance of the secondary battery, and the doped element M has high electronegativity and strong electron attraction capability, so that the oxidation-reduction potential of Fe 2+/Fe3+ is improved, the voltage platform of the secondary battery is improved, and the discharge medium voltage and energy density of the secondary battery are improved. The positive electrode active material realizes synchronous improvement of the energy density and the multiplying power performance of the secondary battery by doping M element and Q element simultaneously. In any embodiment, the composition of the positive electrode active material includes: LiFe1-xMxPOyQz, wherein 0< x is less than or equal to 0.1,3.85 and less than or equal to y is less than or equal to 4,0 is less than or equal to z is less than or equal to 0.05, M comprises one or more of Mn, ni, co, cr, cu, bi, sb, and Q comprises one or more of F, N, cl. In any embodiment, M comprises Mn and Q comprises F. The coordination charges of the anions of the Q element and the anions of the O element are different, so that the inequivalent substitution is caused, the instability of a crystal lattice is increased, and the cycling stability of the secondary battery is sacrificed, when the M element comprises Mn and the N element comprises F, the Mn doping causes the positive electrode active material to generate a ginger-Taylor (Jahn-Teller) effect in charge and discharge, two Mn-O bonds are elongated, the coordination structure of P 5+ and F - is more stable, and the energy density and the quick charge performance of the secondary battery are improved, and meanwhile, the cycling stability of the secondary battery is synchronously improved. The ginger-Taylor effect also shortens four Mn-O bonds of MnO 62-, the Fe-O bonds are lengthened, the oxidation-reduction potential of Fe 2+/Fe3+ is improved, meanwhile, the strength of the Mn-O-F bonds of the F element in the oxygen position can be further improved through strong electronegativity, the electrochemical potential of the positive electrode active material is further enhanced, and the effects of improving a voltage platform and improving energy density are further exerted through the synergistic effect of Mn and F. In the case of any of the embodiments described herein, x is more than or equal to 0.005 and less than or equal to 0.05,0.001 z is more than or equal to 0.01. The positive electrode active material x and y can satisfy the energy density, cycle stability and rate performance of the secondary battery in the above ranges. In any embodiment, the positive electrode active material further includes a carbon element, and the mass content of the carbon element is 1.05% to 1.35% based on the total mass of the positive electrode active material. The positive electrode active material having the carbon content within the above range has a low powder resistivity, which is advantageous for improvement of the rate performance of the secondary battery. In any embodiment, the unit cell parameters of the positive electrode