Aging lithium-ion battery can recover and extend cycle life

by:CTECHi     2021-07-24

Because the current development of lithium-ion battery technology has stabilized, the portable electronic equipment and electric vehicle industries have developed vigorously, resulting in an increasing global demand for lithium-ion batteries. However, the The aging of the material leads to a decrease in the power storage capacity, which leads to the need to replace the battery with a new one after the product has been used for a period of time. The current common charging method in the market is the constant current-constant voltage (CC-CV) charging method. However, this charging method will cause the solid electrolyte interface (SEI) inside the battery to be generated when the constant current (CC) charging stage is about to end. The loss of recyclable lithium ions in the battery leads to a decrease in the cycle life of the battery.

Chen Baiduan, National Taiwan University Condensation Science Research Center, and others applied density functional theory to analyze and calculate the internal lithium ion movement of lithium iron phosphate (LiFePO4) batteries, and establish a sine wave charging Model, this model introduces a negative voltage during the charging process to suppress the formation of the passivation layer.

Researchers compare the battery capacity of the sine wave charging method with the traditional CC-CV charging method based on the standard that the battery capacity of electric vehicles is less than 80% and needs to be replaced. , And the battery is charged and discharged with high current to simulate the use of electric vehicles. From the experimental results, it can be found that the traditional CC-CV charging method reaches 80% capacity after 600 cycles, and the battery using the sine wave charging method also The remaining 95% of the electric capacity indicates that the sine wave charging method has the effect of prolonging the battery life.

In addition, the sine wave charging method for batteries eliminated from electric vehicles can also increase the capacity by up to 18.7%. During the charging process of sine wave charging, the battery temperature rises up to 9°C, and the charging time is only half the time of the traditional CC-CV charging method, and its performance is better than that of the traditional CC-CV charging method.

In order to verify the influence of the sine wave charging method on the internal SEI film impedance of the battery, the researchers used electrochemical impedance spectroscopy (EIS) to analyze the battery, and the results showed that this charge was used Compared with the battery using traditional CC-CV, the battery after 600 cycles of the method effectively inhibits the growth of the SEI film, and can maintain the level of internal impedance similar to that of the new battery. This indicates that the charging method has a significant effect on the internal material structure of the lithium-ion battery. The damage is less, and it can provide a longer battery life. Therefore, the charging method will provide users of lithium-ion battery products with a better choice.

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