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CN-122025884-A - Formation method of lithium ion battery and lithium ion battery

CN122025884ACN 122025884 ACN122025884 ACN 122025884ACN-122025884-A

Abstract

The invention relates to a formation method of a lithium ion battery and the lithium ion battery, which comprises dividing a film forming charging zone into at least 2 subzones according to the capacity exertion charging zone of each single active material, and forming a current when only one active material exerts capacity in the subzones Wherein I i 、W i represents the optimal film forming current and capacity ratio of the active materials which exert capacity, respectively, and when at least two active materials exert capacity in the sub-interval, the active materials are converted into the film forming current Wherein i=1, 2,3,..n, n represents the total number of active materials that exert capacity within the subinterval; and carrying out sectional constant current charging according to the subinterval and the corresponding formation current to finish formation. The formation method provided by the invention aims at a mixed electrode system of various active materials, effectively improves the uniformity, compactness and stability of film formation, and enhances the cycle life and safety of the battery.

Inventors

  • LI YAJIN
  • LI LIMIAO
  • QIAO ZHI

Assignees

  • 中创新航科技集团股份有限公司

Dates

Publication Date
20260512
Application Date
20260316

Claims (11)

  1. 1. A method of forming a lithium ion battery, the lithium ion battery comprising a target electrode comprising an active material comprising at least two different types of active materials; The formation method comprises the following steps: s1, determining that a film forming charge interval of a solid electrolyte interface film formed by a negative electrode of a lithium ion battery in a formation stage is 0-a%SOC, wherein a is more than 0; S2, acquiring a capacity exertion charge interval and an optimal film forming current of each single active material in a target electrode, wherein the target electrode comprises a blended negative electrode or a blended positive electrode; S3, dividing a film forming charging interval into at least 2 subintervals according to the capacity exertion charging interval of each single active material in the target electrode in the film forming charging interval, wherein the subintervals are continuous and non-overlapping, and each subinterval meets any one of the following conditions: Only one active material exerts capacity or at least two active materials exert capacity simultaneously; When only one active material in the subinterval exerts capacity, the current is formed Wherein I i 、W i represents an optimal film forming current and a capacity ratio of the active material exhibiting a capacity, respectively; when at least two active materials exert capacity in the subinterval, the current is formed Wherein i=1, 2,3,..n, n represents the total number of active materials that exert capacity within the subinterval; S4, carrying out sectional constant current charging according to the subinterval obtained in the step S3 and the corresponding formation current, and completing formation.
  2. 2. The method according to claim 1, wherein the value of a ranges from 5 to 20.
  3. 3. The method according to claim 1, wherein when the target electrode contains two active materials, i.e., a first active material and a second active material, the film formation charge interval is divided into a plurality of sub-intervals according to the capacity development charge interval of each single active material in the film formation charge interval; The capacity ratio and the optimal film forming current of the first active material are W 1 and I 1 respectively, the capacity ratio and the optimal film forming current of the second active material are W 2 and I 2 respectively, and the film forming charge interval is 0-a%SOC: Formation current corresponding to subinterval where only the first active material exerts capacity ; Formation current corresponding to subinterval where only the second active material exerts capacity ; Formation current corresponding to sub-interval where the first active material and the second active material simultaneously exert capacity 。
  4. 4. The method according to claim 1, wherein when the target electrode contains three active materials, namely, a first active material, a second active material, and a third active material, the film-forming charge interval is divided into a plurality of sub-intervals according to the capacity development charge interval of each single active material in the film-forming charge interval; The capacity ratio and the optimal film forming current of the first active material are W 1 and I 1 respectively, the capacity ratio and the optimal film forming current of the second active material are W 2 and I 2 respectively, the capacity ratio and the optimal film forming current of the third active material are W 3 and I 3 respectively, and the film forming charge interval is 0-a%SOC: Formation current corresponding to subinterval where only the first active material exerts capacity ; Formation current corresponding to subinterval where only the second active material exerts capacity ; Formation current corresponding to subinterval where only the third active material exerts capacity ; Formation current corresponding to subinterval of capacity of at least two of the first active material, the second active material and the third active material Wherein i is at least two of 1,2,3, and is determined according to the active materials which exert capacity together.
  5. 5. The method of claim 1, wherein the active material in the blended positive electrode comprises a primary active material and a doped active material.
  6. 6. The formation method according to claim 5, wherein the main active material includes lithium iron manganese phosphate and/or ternary material; and/or the doped active material comprises lithium iron phosphate.
  7. 7. The method according to claim 6, wherein the optimal film forming current of the lithium manganese iron phosphate is 0.02-0.1 c; And/or the optimal film forming current of the ternary material is 0.05-0.3 ℃; and/or the optimal film forming current of the lithium iron phosphate is 0.05-0.2 ℃.
  8. 8. The method of claim 1, wherein the active material in the blended anode comprises graphite and carbon silicon.
  9. 9. The method according to claim 1, wherein the step S4 is performed by standing before or after the segmented constant current charging.
  10. 10. The method according to claim 9, wherein the standing time is 1 to 5 minutes; And/or the temperature of the segmented constant current charging or standing is respectively and independently 40-50 ℃; and/or the pressure of the sectional constant current charging is-65 to-55 kPa.
  11. 11. A lithium ion battery, characterized in that the lithium ion battery is obtained by the formation method of the lithium ion battery according to any one of claims 1 to 10.

Description

Formation method of lithium ion battery and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a formation method of a lithium ion battery and the lithium ion battery. Background With the dual demands for cell energy density and cost, blending systems comprising at least two active materials are becoming the current mainstream. The common blending of the cathode and the anode is represented by a graphite silicon-doped system, and the energy density of the cathode is improved by a silicon material, and the positive blending comprises the blending of lithium iron phosphate and a ternary material, the blending of lithium iron phosphate and lithium manganese iron phosphate, the blending of lithium manganese iron phosphate and the ternary material and the like. The different blending systems are used for realizing the optimization of the comprehensive performance of the battery cell. The formation is a key procedure in the production process of lithium batteries, and directly influences the formation quality of a negative electrode solid electrolyte interface film (SEI film), so as to determine the cycle life, the rate capability and the safety of a battery cell. In the mixing system, different materials have different voltage intervals, when the different materials are mixed according to a specific proportion, the current density born by the materials in different charge intervals of the formed mixing system also changes, the current density change of the positive electrode material directly affects the polarization of the positive electrode, the positive electrode potential can be changed when the polarization degree is increased, the potential of the negative electrode is further affected, and the fluctuation of the potential of the negative electrode plays an important role in the film forming process of the negative electrode. Therefore, how to selectively form the current for the lithium ion battery of the blending system is a technical problem to be solved at present. Disclosure of Invention In view of the above problems, an object of the present invention is to provide a formation method of a lithium ion battery and a lithium ion battery. In order to achieve the aim of the invention, the invention adopts the following technical scheme: In a first aspect, the present invention provides a method of forming a lithium ion battery comprising an active material comprising at least two different types of active materials; The formation method comprises the following steps: s1, determining that a film forming charge interval of a solid electrolyte interface film formed by a negative electrode of a lithium ion battery in a formation stage is 0-a%SOC, wherein a is more than 0; S2, acquiring a capacity exertion charge interval and an optimal film forming current of each single active material in a target electrode, wherein the target electrode comprises a blended negative electrode or a blended positive electrode; s3, dividing a film forming charging interval into at least 2 sub-intervals according to the capacity exertion charging interval of each single active material in a target electrode in the film forming charging interval, wherein the sub-intervals are continuous and non-overlapping, and each sub-interval meets any one of the following conditions: Only one active material exerts capacity or at least two active materials exert capacity simultaneously; When only one active material in the subinterval exerts capacity, the current is formed Wherein I i、Wi represents an optimal film forming current and a capacity ratio of the active material exhibiting a capacity, respectively; when at least two active materials exert capacity in the subinterval, the current is formed Wherein i=1, 2,3,..n, n represents the total number of active materials that exert capacity within the subinterval; S4, carrying out sectional constant current charging according to the subinterval obtained in the step S3 and the corresponding formation current, and completing formation. According to the invention, according to the capacity contribution of different active materials in different SOC regions, the optimal film forming current of each material and the capacity exertion region thereof are pertinently matched, so that each active material can promote film forming with better current density in the exertion capacity stage, the uniformity, compactness and stability of film forming are effectively improved, and the cycle life and safety of the battery are enhanced. In a second aspect, the present invention provides a lithium ion battery, which is obtained by the formation method of the lithium ion battery in the first aspect of the present invention. The lithium ion battery provided by the invention adopts the formation method, so that the interface stability can be improved, the continuous decomposition of electrolyte in the circulation process can be effectively inh