Liquid-injection process of low-temperature lithium ion battery cell

Abstract

The invention relates to a liquid-injection process of a low-temperature lithium ion battery cell. The liquid-injection process is characterized by comprising the following two steps: (1) when a liquid is injected into the lithium ion battery cell, firstly injecting an electrolyte capable of forming a good SEI (solid electrolyte interface) film, sealing and standing, thus forming the cell; (2) after forming the cell, injecting the rest of the other low-temperature electrolyte or low-melting point solvent, and sealing. The process can be used for solving the use problems of solvents of PC (polycarbonate) and linear carboxylic ester which are in favor of improving the battery low-temperature performance and are bad for the formation of the SEI film, therefore, the battery low-temperature performance is improved; and meanwhile, the gas generated at the early charge process of the battery when an electrode forms the SEI film can be removed.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, in particular to a liquid injection process for low-temperature lithium-ion battery cells. Background technique [0002] During the first charging and discharging process of the lithium-ion battery, the electrode material and the electrolyte react at the solid-liquid phase interface to form a solid dielectric film (SEI film). SEI film is an electronic insulator, but Li + excellent conductor. [0003] On the one hand, the formation of the SEI film consumes part of the lithium ions, which increases the irreversible capacity of the first charge and discharge, and reduces the first charge and discharge efficiency of the electrode material. Moreover, gas is generated during this process, which adversely affects the performance of the battery cell. Many literatures have proposed various methods to eliminate the adverse effects of gas. For example, patent CN101399328A proposes a two-step liquid ...

AI Technical Summary

Problems solved by technology

In organic electrolytes, EC is generally an essential component for forming an excellent and stable SEI film, but EC has a high melting point (37°C), which is unfavorable for the low-temperature performance of the battery

Therefore, the industry has always wanted to replace part or all of EC with PC (-49°C) with a similar dielectric constant and low melting point. However, PC has a higher reduction potential and will co-embed graphite layers first, causing the graphite layers to peel off.

In order to inhibit the damage of PC to graphite, the electrolyte with PC solvent needs to add film-forming additives with higher reduction potential at the same time, and the addition of film-forming additives will generally lead to a decrease in other performances of the battery

In addition, although some other low-melting point solvents will not damage graphite, they are not conducive to the formation of excellent and stable SEI films.

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