Comprehensive understanding of self-discharge of lithium battery

Classification of self-discharge:

From the effect of self-discharge on the battery, self-discharge can be divided into two types: self-discharge where the loss capacity can be reversibly compensated; and self-discharge where the loss capacity cannot be reversibly compensated. According to these two classifications, we can give some self-discharge reasons approximately contoured.
Reasons for self-discharge:

1. Causes of reversible capacity loss: The reason for the reversible capacity loss is that a reversible discharge reaction occurs, and the principle is consistent with the normal discharge reaction of the battery. The difference is that the normal discharge electron path is an external circuit and the reaction speed is fast; the self-discharge electron path is an electrolyte, and the reaction speed is very slow.

2. Causes of irreversible capacity loss: When an irreversible reaction occurs inside the battery, the resulting capacity loss is irreversible capacity loss. The types of irreversible reactions that occur mainly include:

A: The irreversible reaction between the positive electrode and the electrolyte (relatively mainly occurs in two materials which are prone to structural defects such as lithium manganate and lithium nickelate, such as the reaction of lithium manganate positive electrode with lithium ion in the electrolyte:

LiyMn2O4+xLi++xe-→Liy+xMn2O4, etc.)

B: Irreversible reaction between the negative electrode material and the electrolyte (the SEI film formed during the formation is to protect the negative electrode from the corrosion of the electrolyte, and the reaction between the negative electrode and the electrolyte may be:

LiyC6→Liy-xC6+xLi++x, etc.)

C: Irreversible reaction caused by impurities in the electrolyte itself

(eg, CO2 possible reaction in the solvent: 2CO2+2e-+2Li+→Li2CO3+CO

The reaction of O2 in the solvent: 1/2O2+2e-+2Li+→Li2O)

A similar reaction irreversibly consumes lithium ions in the electrolyte, which in turn loses battery capacity.

D: Irreversible reaction caused by micro short circuit caused by impurities during production. This phenomenon is the most important cause of the large self-discharge of individual batteries.

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