Screening method for self-discharging of square lithium ion batteries

Abstract

The invention provides a screening method for self-discharging of square lithium ion batteries. The method comprises the following steps: (1) charging each battery at normal temperature and normal pressure to a preset charged state and recording an open-circuit voltage V1 of the battery; (2) placing the battery in a preset high pressure environment for a preset time t; (3) taking the batter out, placing the battery in a normal pressure environment and recording an open-circuit voltage V2 of the battery; and (4) screening out a battery, with a V2 value less than a set value U1 or a difference value between V1 and V2 greater than a set value U2, as a battery with great self-discharging. Preferably, the preset charged state in the step (1) is 50 to 100% SOC, the preset high pressure environment in the step (2) is 0.15 to 1 MPa, and the preset laying time t is 5 to 20 d. According to the invention, a preset high pressure is applied on the square battery to allow the positive plate and the negative plate of each battery to fully contact with the diaphragm of the battery so as to effectively screening out batteries with great self-discharging, so the detection rate of batteries with great self-discharging can be substantially increased, and product quality is improved.

Description

technical field [0001] The invention relates to a self-discharge screening method of a square lithium ion battery. Background technique [0002] At present, with the depletion of fossil fuels and the deterioration of the environment, lithium-ion batteries have become a new power source and a core component of electric vehicles, and are developing rapidly. The battery pack for electric vehicles is mainly composed of a large number of single cells connected in series and parallel. The consistency of the single battery is an important factor affecting the performance of the battery pack. The inconsistent self-discharge rate of single cells is one of the important reasons for the poor performance of battery packs. Therefore, it is necessary to screen out batteries with large self-discharge before the single batteries leave the factory. [0003] Battery self-discharge refers to the loss of capacity due to internal spontaneous reactions when the battery is in an open circuit st...

AI Technical Summary

Problems solved by technology

In a normal pressure environment, the internal and external pressures of the battery are equal, the structure of the internal pole core of the battery is loose, and the micro-short circuit may not occur, which will not lead to a large self-discharge of the battery. However, under certain conditions, the micro-short circuit may occur, causing the battery Large self-discharge