Effect of the Direct Pre-Lithiation on Cycling Performance of Li Ion Battery with Silicon-Containing Anodes

Abstract

The desire to advanced lithium ion battery is growing with the expansion of electronic markets. Therefore, studies on making electrode materials with high energy density and long cycle life are actively conducted. Among those materials, silicon containing anode is one of the most important materials in making high energy density batteries because of the high theoretical capacity of silicon (~4200mAh/g). However, silicon containing anodes have the disadvantage of large initial irreversible capacity and continuous capacity loss due to large volume change of silicon. Because Li ions transferred from the cathode to the anode disappear without being reversibly used for charging and discharging, the capacity of the full cell becomes significantly smaller than expected. To solve this problem, pre-lithiation has been proposed as a powerful method which can be done through several methods including chemical and electrochemical pre-lithiation and pre-lithiation by direct-contact to lithium [1]. Pre-lithiation studies show that the Coulombic efficiency and discharge capacity dramatically increased. In this research, we propose a method to improve a cycle life of Li ion batteries with silicon containing anodes by applying pre-lithiation to suppress the volume change of silicon. We applied a direct pre-lithation method to increase the cycle life through depositing Li onto the anode; which has an impact on the manufacturing process and the accurate controlling of Li amount. When the coin cell was fabricated with a high capacity cathode and a pre-lithiated silicon containing anode, we were able to obtain not only high discharge capacity (~18%) but also enhanced cycle life characteristics (~30%). In order to investigate the cause of improved cycle life of the cell, three electrode electrochemical experiments were conducted, and then the charged/discharged state of the anode and the cathode are separately extracted in the full cell profile. Analysis of the extracted profiles confirms that the end-voltage of the anode with accurate amount of extra Li is lowered, which means that the silicon in the anode did not completely shrink after discharge. This result demonstrates that the pre-lithiation method is effective in reducing the volume change of the silicon during cycling. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) also supported the above results. We would like to share this result through the presentation and hope that this work will provide an effective method to build a long cycle life Li ion battery with silicon-containing anodes.