New insight into the mechanism of LiPO2F2 on the interface of high-voltage cathode LiNi0.5Mn1.5O4 with truncated octahedral structure.

The development of high energy density material is of great importance and urgency for new generation of energy storage system. However, electrolyte formula for high voltage system remains a challenge. The use of various functional additives gives rise to the complexity of electrolyte system and hinders completely understanding of the action mechanism of additives. Herein, we report the adaptability and mechanism of a single additive LiPO 2 F 2 added in the conventional LiPF 6 -based electrolyte system. The resulting conclusion displays a notable improvement in the cycling stability for 5 V-class cathode LiNi 0.5 Mn 1.5 O 4 , the capacity retention increase from 85.76% to 95.92%. It is comforting that the rate performance is not reduced due to the increase in cycle stability, and it also shows good advantages in terms of high rate and reversibility. Meanwhile, detailed analysis about interface mechanism for LiPO 2 F 2 by the surface testing (SEM, TEM and XPS) give the direct characterizations. Common ion effect of the decomposition product Li 3 PO 4 from additive is probed from the above characterization and combined with DFT calculations and some clever experiments to prove the positive effect of additives. The findings obtained from this work may provide a useful guidance for the research on electrolyte formulation for high voltage system. Unlabelled Image • LiPO 2 F 2 as film-formed additive for high voltage system • Li 3 PO 4 produced by LiPO 2 F 2 on the surface of cathode plays a key role in performance improvement by common ion effect. • Cycling performance for LNMO has been improved. [ABSTRACT FROM AUTHOR]