Why lithium battery performance will decline?

Lithium batteries are commonly seen in our daily lives. In addition to being used in electric vehicles, lithium batteries are found in more and more electronic products such as mobile phones and tablet computers, and their performance is decaying all the time.




You charge it every time your cellphone or electric car runs out of power, and the maximum capacity will be reduced after this cycle is completed. A few years later, you will find that the phone was originally available once for 2 days, but it can only last for half a day. The charge for an electric car was originally from downtown Shanghai to Chongming. Now it is powered off from the company.




Recently, researchers at the U.S. Department of Energy discovered the reasons for the decline in battery capacity.




According to the Gizmodo website, this is mainly due to the change in the electrode structure due to the movement of ions in the cell.




In lithium-ion batteries, lithium ions move from the anode to the cathode through non-aqueous electrolytes. Each charge-discharge cycle, the electrode structure will occur a slight change (atomic level changes).




During discharge, ions pass through the anode and they gradually dissipate on the electrode surface in an irregular fashion. HuolinXin, a material scientist at Brookhaven LabsCenter, described the phenomenon as similar to the gradual rusting of steel.




Unfortunately, the flaw of lithium batteries is "born" and can not be changed. Not only the anode, the cathode will also have the performance degradation.




As lithium ions traverse the electrode during charging, a rock-salt is created, forming an electrically insulating shell in the cell. The thicker the insulating shell is, the worse the batterys charging performance is. HuolinXin said that in the case of higher charging voltage, the decline in charging performance even more pronounced. Not only that, the maximum battery capacity will therefore decline.




Xin said that may be able to solve this problem by adding a coating material to the cathode that is resistant to crystallization, which allows ions to pass freely between the anode and the cathode. However, such materials require long-term research and development and experimental verification.