Screening method for recessive short circuit lithium ion cell

Abstract

The invention discloses a screening method of hidden short-circuit lithium-ion battery cores, comprising the following steps: A. carrying out the half power storage ageing treatment of the battery cores after cleaning seals thereof and screening the battery cores with the unqualified voltage after the half power storage ageing treatment; B. carrying out the full power storage ageing treatment of the battery cores with the qualified voltage and screening the unqualified battery cores after the full power ageing treatment. The screening method makes full use of the advantages of the half power storage and the full power storage and carries out the storage by two times, that is, the half power storage is firstly carried out for a period of time to lead the dispersion of the lithium ions in a graphite negative electrode layer to be more even, thereby reducing the size expansion of the battery cores after the capacity grading and improving the reversible capacity; then the full power storage is further carried out; as the voltage is high during the full power storage, the voltage attenuation of internal micro-short-circuit battery cores is more apparent, and the battery cores are more easily screened out.

Description

technical field [0001] The invention relates to the technical field of battery manufacturing, in particular to a screening method for hidden short-circuit lithium-ion batteries. Background technique [0002] Lithium-ion batteries are developed on the basis of lithium metal batteries. With many advantages such as high specific energy, long service life, and environmental protection, they have rapidly developed into the preferred energy source for mobile electronic devices. However, in recent years, the explosion and recall of lithium batteries have cast a lot of shadows on the safety of lithium-ion batteries. The main aspects that affect the safety of lithium-ion batteries are: internal short circuit or external short circuit, overcharge or overdischarge, high rate charge Caused by discharge and improper use environment, especially internal short circuit. Due to the unremoved dust sticking inside the lithium-ion battery during the production process, the metal debris introdu...

AI Technical Summary

Problems solved by technology

Due to the unremoved dust sticking inside the lithium-ion battery during the production process, the metal debris introduced during the process, the local mismatch between the positive and negative electrodes caused the formation of lithium dendrites, and the material particles on the surface of the electrodes caused the diaphragm to break through. Or the rupture of the diaphragm directly caused by the production process can cause a short circuit or a micro-short circuit inside the cell. For the dominant short-circuit cell, it can generally be picked out by a short-circuit tester during the production process, but for those cells that cannot be used for short-circuit The hidden short circuit directly measured by the tester, that is, the micro-short-circuit battery will generate heat, bulge or even explode after several times of charging and discharging, which poses a great safety hazard during use.

[0003] At present, there are two main ways to screen for hidden short-circuit cells: 1) After the cells are charged to half-charged and aged at a higher temperature (35°C-50°C) for several days, the micro-short-circuit cells are screened according to the voltage drop; 2) ) After the battery is sealed, it is directly charged to a full charge of 4.2V, and after being stored at room temperature (15°C-35°C) for several days, the micro-short-circuit battery is screened according to the voltage drop. The drop is not obvious, and it is not easy to pick out the micro-short-circuit cells. On the other hand, because the aging temperature needs to be 35-50°C, additional energy is wasted

Method II is directly charged to full charge for storage. Although it is easy to pick out the micro-short-circuit cell, due to the lack of necessary aging after half charge and before full charge, the lithium ions and electrolyte have a uniform diffusion time, thus When the battery is fully charged, part of the lithium will not be precipitated on the surface of the negative electrode, resulting in a decrease in reversible capacity and an increase in the size of the finished core, and there is a large explosion and other safety hazards in the fully charged storage battery