Voltage analysis of polymer lithium battery charging

Polymer lithium battery charging voltage description

1. Polymer lithium battery charging method

At present, the charging method of polymer lithium battery generally adopts constant current and constant voltage charging: the battery first charges CC with constant current, when the battery voltage rises to a certain value (4.2V). The voltage remains constant, and the current in the circuit drops to very little and eventually approaches zero.

2. Electrochemical principle of polymer lithium battery

A polymer lithium ion battery refers to a secondary battery in which a Li+ intercalation compound is a positive electrode or a negative electrode. The positive electrode is a lithium compound LiCoO2, LiNiO2 or LiMn2O4, and the negative electrode is a lithium-carbon intercalation compound LixC6. A typical battery system is:

(-)C|LiPF6-EC+DEC|LiCoO2(+)

Positive electrode reaction: LiCoO2=Li1-xCoO2+xLi++xe------------(2.1)

Negative reaction: 6C+xLi++xe-=LixC6-----------(2.2)

Total battery reaction: LiCoO2+6C=Li1-xCoO2+LixC6-----------(2.3)

3. After the polymer lithium battery is overcharged

The polymer lithium battery cannot be overcharged. If overcharge occurs, the performance of the battery will be greatly affected. Metal lithium deposition will occur in the negative electrode, which may cause the battery to explode or ignite, and the solvent in the electrolyte may be decomposed, resulting in serious damage to the battery performance.

4. Polymer lithium battery charging voltage value selection

At present, the electrochemical window of the positive electrode material, the negative electrode material and the electrolyte used in the commercial lithium battery are basically above 4.5V, that is, the battery is relatively stable when the battery charging voltage reaches 4.5V. However, if the battery charging voltage is too low (such as below 4.15V), it will seriously affect the battery charge. If the battery charging voltage is controlled at 4.13V, the battery charge is about 60-80% of the battery capacity, greatly affects the performance of battery performance. In fact, the charging voltage of the battery is related to the battery system and has nothing to do with the discharge rate of the battery.

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