Development of Electrolytes for Si-Graphite Composite Electrodes

• Published in: Journal of the Electrochemical Society Vol. 165; no. 10; pp. A2154 - A2161
• Main Authors: Nguyen, Cao Cuong, Lucht, Brett L.
• Format: Journal Article
• Language: English
• Published: United States The Electrochemical Society 01.01.2018
• Subjects: Electrolyte; ENERGY STORAGE; lithium ion battery; solid electrolyte interphase
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.0621810jes

The performance of Si-graphite/Li cells and Si-graphite/NMC111 cells has been investigated in 1.2 M LiPF6 /EC:DEC (1/1, w/w) with different electrolyte additives including LiNO3, FEC, and MEC. The addition of additives into electrolytes result in a significant improvement in capacity retention compared to the standard electrolyte for Si-graphite/Li cells. The cells cycled with electrolyte containing 0.5 wt% LiNO3, 5-10 wt% MEC or 10 wt% FEC have high capacity retention, at least 88%, while the cells cycled with standard electrolyte have lower capacity retention, 64%, after 100 cycles. Investigation of Si-graphite/NCM111 cells reveals that the cells cycled in electrolyte containing 0.5 wt% LiNO3 have better capacity retention than cells cycled with 10 wt% FEC, 57.9% vs. 44.6%, respectively. The combination of 10% MEC and LiNO3 further improves the capacity retention of the Si-graphite/NCM111 full cells to 79.9% after 100 cycles which is highest among the electrolytes investigated. Ex-situ surface analyses by XPS and IR-ATR have been conducted to provide a fundamental understanding the composition of the solid-electrolyte interphase (SEI) and its correlation to cycling performance.