PNNL

Abstract

The growth of lithium (Li) dendrite and the low Coulombic efficiency (CE) of Li anode during repeated Li plating/stripping processes are the two major obstacles to the development of rechargeable Li metal batteries (LMBs). Introducing a dendrite-suppressing additive into the nonaqueous electrolyte is one of the facile and effective solutions to promote the commercialization of LMBs. Herein, Li difluorophosphate (LiPO2F2, LiDFP) is used as an electrolyte additive to suppress the growth of Li dendrites by forming a vigorous and stable solid electrolyte interphase layer on the Li metal surface. Moreover, the Li CE can be largely improved from 84.6% for the conventional LiPF6-based electrolyte to 95.2% by the addition of an optimal concentration of LiDFP at 0.15 M. The optimal LiDFP-containing electrolyte can allow the Li||Li symmetric cells to cycle stably for more than 500 and 200 h at 0.5 and 1.0 mA cm-2, respectively, much longer than the control electrolyte without LiDFP additive. Meanwhile, this LiDFP-containing electrolyte can also greatly enhance the cycle life of the Li||LiNi1/3Co1/3Mn1/3O2 cells with a moderately high mass loading of 9.7 mg cm-2. These results demonstrate that LiDFP has extensive application prospects as a dendrite-suppressing additive in advanced LMBs.