Lithium difluorophosphate as a multi-functional electrolyte additive for 4.4 V LiNi0.5Co0.2Mn0.3O2/graphite lithium ion batteries

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2019-08, Vol.846, p.113141, Article 113141
• Main Authors: Lei, Qiufen, Yang, Tianxiang, Zhao, Xiaoyang, Fan, Weizhen, Wang, Wenlian, Yu, Le, Guo, Shoubin, Zuo, Xiaoxi, Zeng, Ronghua, Nan, Junmin
• Format: Article
• Language: English
• Subjects: Decomposition reactions; Electrolytes; Graphite; High temperature; Lithium; Lithium-ion batteries; Performance enhancement; Rechargeable batteries
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2019.05.023

Lithium difluorophosphate (LiPO2F2) as a multi-functional additive is added into the carbonate-based electrolyte to enhance the electrochemical performances of 4.4 V LiNi0.5Co0.2Mn0.3O2/graphite lithium ion batteries (LIBs). Compared with the baseline electrolyte, the addition of 2% LiPO2F2 can significantly improve the electrolyte stability and enlarge the electrochemical window of about 1 V. At the room temperature and cutoff voltage of 4.4 V, the capacity retention of the batteries with 2% LiPO2F2 is increased from 55% to 93% after 150 cycles. At the high temperature of 45 °C, the capacity retention of the battery with 2% LiPO2F2 additive still keeps 86% after 150 cycles, while the coulombic efficiency of the battery without additive begins to decline sharply after 30 cycles. These positive effects are also reflected in the low temperature discharging at −20 °C, cycling at −10 °C, and rate capability. The enhanced performances are attributed to the excellent interfacial film promoted by the additive, which can reduce the interfacial impedance, suppress electrolyte decomposition, and alleviate the side reactions. It is indicated that LiPO2F2 is a promising multi-functional electrolyte additive for high-voltage NCM/graphite LIBs.