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CN-122025882-A - Dynamic pressure formation method suitable for soft-package battery cell and soft-package battery cell

CN122025882ACN 122025882 ACN122025882 ACN 122025882ACN-122025882-A

Abstract

The application provides a dynamic pressure formation method suitable for a soft-package battery cell and the soft-package battery cell, and relates to the technical field of lithium batteries. The application provides a dynamic pressure formation method suitable for a soft-package battery cell, which is characterized in that the pressure is changed from a constant static mode to dynamic circulation adjustment in a certain interval, so that the gas pressure between an anode pole piece and a diaphragm in the battery cell and in each pore in the pole piece is always in dynamic change in the formation process, smooth discharge of gas generated by film formation of an SEI film is facilitated, the time required by gas overflow is shortened, on the other hand, stress release of stress deformation of the diaphragm caused by volume expansion extrusion of the cathode in the formation process is facilitated, the risk of wrinkling of the diaphragm in the subsequent charge-discharge process is reduced, the negative electrode reaction interface of the soft-package battery cell obtained by the formation method under the condition of 100 percent SOC is good, black spots, lithium precipitation, abnormity such as no wrinkling of the anode pole piece and the diaphragm are avoided, the electrical performance is remarkably improved, and the formation time is saved.

Inventors

  • ZHANG FANGPING
  • XIANG LIANGSHUN
  • XIANG JIAYUAN
  • ZHOU JING
  • LI YANHONG
  • ZHOU QINGQING
  • CAI YANHUI
  • XIE YUE
  • YAN YINI

Assignees

  • 浙江南都电源动力股份有限公司
  • 杭州南都动力科技有限公司

Dates

Publication Date
20260512
Application Date
20251226

Claims (10)

  1. 1. The dynamic pressure formation method suitable for the soft-package battery core is characterized by comprising the following steps in sequence: Step 1, applying pressure P1 to the battery core through a device when the battery core is kept still before formation and initial charging, and then linearly and reciprocally cycling the applied pressure in a P1-P2 interval; step 2, applying pressure to linearly and reciprocally circulate in the interval P2-P3, and charging with current II during the process 2; step 3, applying pressure to linearly and reciprocally circulate in the interval P3-P4, and charging with current III during the process 3; A step 4 of applying pressure to linearly reciprocate in the interval P4-P5, wherein the step 4 is charged by a current IV during the process; the current I < current II < current III < current IV, and the pressure P1< P2< P3< P4< P5.
  2. 2. The dynamic pressure formation method suitable for the soft-packaged battery cells according to claim 1, wherein the pressure P1 is more than or equal to 0.03MPa, and the pressure P5 is less than or equal to 0.3 MPa.
  3. 3. The dynamic pressure formation method for soft-pack cells according to claim 1 or 2, wherein the pressures P1, P2, P3, P4, and P5 are 0.03MPa, 0.05MPa, 0.07MPa, 0.09MPa, and 0.11MPa in this order.
  4. 4. The method of claim 1 or 2, wherein the current I, the current II, the current III, and the current IV are in the range of 0.1-0.3A, 0.5-1A, 1.2-2A, and 2.2-3.5A, respectively.
  5. 5. The method of claim 4, wherein the current I, the current II, the current III, and the current IV range are 0.3A, 0.6A, 1.8A, and 3A, respectively.
  6. 6. The method for dynamic pressure formation of a soft battery cell according to claim 1, wherein the duration of the process 1 is 30-60min, the duration of the process 2 is 12-30min, the duration of the process 3 is 30-56min, and the duration of the process 4 is 60-120min.
  7. 7. The method for dynamic pressure formation of soft battery cells according to any one of claims 1,2,5 and 6, wherein a rest phase I is provided between the step 2 and the step 3, and the pressure of the rest phase I is P2, the current is 0, and the time is 10-20 min.
  8. 8. The method according to claim 7, wherein the step 4 is followed by a rest phase II, the rest phase II has a pressure of P5, a current of 0, and a time of 10-20 min.
  9. 9. The method of claim 1,2,5,6,8, wherein the state of charge of the cell after the end of step4 is 90-100% SOC.
  10. 10. A soft-pack cell, characterized in that the preparation steps thereof comprise a dynamic pressure formation method according to any one of claims 1-9, which is suitable for soft-pack cells.

Description

Dynamic pressure formation method suitable for soft-package battery cell and soft-package battery cell Technical Field The invention relates to the technical field of lithium batteries, in particular to a dynamic pressure formation method suitable for a soft-package battery cell and the soft-package battery cell. Background The soft package battery core is used as an important packaging form of the lithium ion battery, and is widely applied in the fields of consumer electronics, electric automobiles, energy storage systems and the like due to the advantages of high energy density, flexible design, good safety and the like. In the manufacturing process, formation is one of the key processes, and aims to form a stable solid electrolyte interface film on the surface of the negative electrode by first charging. The SEI film has the characteristics of ion conduction and electronic insulation, can prevent electrolyte from being continuously decomposed, and ensures the efficiency and the safety of long-term circulation of the battery. Therefore, the optimization of the formation process directly affects the initial performance, cycle life and reliability of the cell. At present, a pressurizing and heating mode is generally adopted in the soft package battery core formation stage in the industry, and a multi-stage constant current charging strategy (usually three-stage charging to about 30% SOC or four-stage charging to about 90% SOC) is combined. The main purpose of the process is to apply constant external pressure in the SEI film forming process, promote the pole piece and the diaphragm to keep close contact, and enhance the uniformity of interface reaction, so as to obtain a compact and stable SEI film structure. The multi-stage charging is arranged to control the reaction rate, so that the aggravation of side reaction and local overheating caused by the excessively fast charging are avoided. Although the above method has achieved effects in a certain range, it has revealed that the significant drawbacks in practical use are that the solvent and additive in the electrolyte react with each other in reduction on the surface of the negative electrode during SEI film formation to generate a certain amount of gas (e.g.)、Etc.). Under constant pressure conditions, these gases are compressed between the pole piece aperture, pole piece and diaphragm gap, and are difficult to effectively vent. The gas retention can cause uneven infiltration of local electrolyte, prevent normal transmission of lithium ions, cause uneven growth of SEI film, even form local insulation area, and cause capacity attenuation and internal resistance increase in subsequent circulation. Lithium ions cause significant volume expansion (typically up to 10% or more) when first intercalated into a graphite negative electrode. Under the action of constant external pressure, the expanded negative electrode can continuously squeeze the diaphragm, so that the diaphragm is subjected to micro deformation and internal stress is accumulated. When the thickness of the negative electrode is partially retracted in the subsequent discharging process, the diaphragm is easy to generate wrinkles or micro-damage due to uneven stress release. The wrinkled areas may cause excessive local resistance, increasing the risk of thermal runaway, and also accelerating the aging of the diaphragm, affecting its mechanical integrity and long-term isolation. The combined action of gas retention and diaphragm stress deformation obviously improves the probability of negative electrode black spots and lithium precipitation in the formation stage. The black spots generally correspond to areas where electrolyte decomposition products and gas are gathered, and represent the areas where SEI film quality is poor, and lithium precipitation is caused by non-uniform deposition on the surface of a negative electrode to form metal lithium due to the blocking of lithium ion transmission, so that capacity loss is caused, and potential safety hazards such as short circuit are more likely to be caused. To alleviate the above problems, the industry has attempted various improvements such as optimizing electrolyte formulations to reduce gassing, adjusting charge curves to slow reaction kinetics, improving separator coatings to enhance their extrusion resistance, and the like. However, these methods have focused on the adjustment of the material system or single process parameters, and have not been radically changed to the dynamic requirements of the internal physical environment (pressure distribution and gas migration conditions) of the cell in the process. Particularly when facing higher energy density electrode systems, the gas generation and expansion phenomena are more prominent, and the limitations of the traditional constant pressure formation process are increasingly prominent. Disclosure of Invention The application provides a dynamic pressure formation method suitable for a soft package b