Improving the cyclability performance of lithium-ion batteries by introducing lithium difluorophosphate (LiPO 2 F 2 ) additive

• Published in: RSC advances Vol. 7; no. 42; pp. 26052 - 26059
• Main Authors: Yang, Guanghua, Shi, Junli, Shen, Cai, Wang, Shuwei, Xia, Lan, Hu, Huasheng, Luo, Hao, Xia, Yonggao, Liu, Zhaoping
• Format: Journal Article
• Language: English
• Published: 01.01.2017
• Subjects: Additives; anodes; atomic force microscopy; carbon electrodes; cathodes; dielectric spectroscopy; Electrochemical impedance spectroscopy; electrochemistry; Electrolytes; graphene; Graphite; Lithium; lithium batteries; Lithium-ion batteries; Rechargeable batteries; Solid electrolytes; X-ray photoelectron spectroscopy
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C7RA03926C

The cyclability of lithium-ion batteries (LIBs) is often affected by the components of the solid electrolyte interphase (SEI) layer which is generated from electrochemical decomposition of electrolyte. Here, lithium difluorophosphate (LiPO 2 F 2 ) is studied in this work. When 1.6 wt% LiPO 2 F 2 additive is incorporated into the reference electrolyte, the capacity retention of graphite/Li half-cell is increased from 82.53% to 98.04% and the capacity retention of LiCoO 2 /Li half-cell is increased from 89.60% to 97.53% after 160 cycles. Electrochemical impedance spectroscopy (EIS) indicates that the SEI layer containing LiPO 2 F 2 can decrease the surface impedance of cells in the last stage cycle. In situ atomic force microscopy (AFM), DFT calculations and X-ray photoelectron spectroscopy (XPS) results show that LiPO 2 F 2 is deposited on the surface of both LiCoO 2 and graphite electrodes, which effectively protects the graphite anode and suppresses the degradation of the cathode during the long-term cycling of LIBs.