Method for improving formation liquid loss and application thereof

Abstract

The invention relates to a method for improving formation liquid loss and application thereof. The method comprises the steps: carrying out the gradient change adjustment of the vacuum degree according to voltage changes in the negative pressure formation process, wherein the gradient change adjustment of the vacuum degree comprises four stages: the first stage: the voltage is less than 2.5 V, andthe vacuum degree is adjusted to be -20 kPa to -40 kPa, wherein -40 kPa is not included; in the second stage: the voltage ranges from 2.5 V to 3.0 V, wherein 3.0 V is not included, and the vacuum degree is adjusted to range from -40 kPa to -80 kPa, and -80 kPa is not included; in the third stage: the voltage ranges from 3.0 V to 3.75 V, and the vacuum degree is adjusted to range from -80 kPa to -100 kPa; in the fourth stage, the voltage is greater than 3.75 V, the vacuum degree is adjusted to be -40 kPa to -80 kPa, wherein -80 kPa is not included. By adopting the method, the liquid loss in the formation process is effectively improved while the vacuum pumping of the gas accumulated in the battery is ensured.

Description

technical field [0001] The invention belongs to the field of batteries, and relates to a method for improving liquid loss from formation and an application thereof. Background technique [0002] In the battery production process, formation is a relatively important process. During formation, a layer of SEI film will be formed on the surface of the negative electrode sheet. The quality of the SEI film directly affects the cycle life, safety, thermal stability, self-discharge and internal stability of the battery cell. Resistance and other electrochemical properties; the current negative pressure formation process will cause electrolyte loss, and reducing the amount of liquid loss in the formation is of great significance for reducing the cost of the formation process. [0003] At present, there are several methods for the amount of fluid loss during formation: 1) Increase the volume of the transition cup that collects the electrolyte in the tooling of the formation cabinet, i...

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Problems solved by technology

However, this method is too cumbersome, and the composition of the first electrolyte and the second electrolyte is different, which will affect the wettability of the electrolyte and affect the performance of the battery.

[0004] In the formation process disclosed by CN110661050A, the temperature is maintained at 25±5°C, the vacuum valve is opened, the vacuum degree is kept at -0.06~-0.08MPa, and the constant current is charged at 0.05C to 3.22-3.24V, shelved, and then at a constant current of 0.2C Charge to 3.34-3.35V; CN101908647A discloses the use of negative pressure formation technology to form the battery, control the internal pressure of the battery within the vacuum range of -0.01MPa~-0.1MPa, and charge within the current range of 0.01C~1.5C, And control the charging amount of the lithium-ion battery for formation by time; CN102117936A discloses a method for forming a soft-packed lithium-ion battery. During the formation process, a reflux device is used to evacuate the inner cavity of the aluminum-plastic film, and the vacuum degree of the gauge pressure is 0.05-0.06MPa. Then use an inert gas to back-press the electrolyte, and automatically control the amount of back pressure to prevent the gas from entering the battery; the vacuum degree during the above formation process is kept within a specific range, and when the vacuum is too high, a large amount of electrolyte will be sucked away , resulting in an increase in the amount of fluid loss, and if the vacuum is too small, it will cause gas residues and affect battery performance

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