Beyond LiF: Tailoring Li<sub>2</sub>O-Dominated Solid Electrolyte Interphase for Stable Lithium Metal Batteries
Huipeng Zeng, Kai Yu, Jiawei Li, Mingman Yuan, Junjie Wang, Qingrong Wang, Anjie Lai, Yidong Jiang, Yan Xu, Guangzhao Zhang, Hongli Xu, Jun Wang, Wei Huang, Chaoyang Wang, Yonghong Deng, Shang‐Sen Chi
Abstract
The components and structures of the solid-electrolyte interphase (SEI) are critical for stable cycling of lithium metal batteries (LMBs). LiF has been widely studied as the dominant component of SEI, but Li 2 O, which has a much lower diffusion barrier for Li +, has rarely been investigated as the dominant component of SEI. The effect of Li 2 O-dominated SEI on electrochemical performance still remains elusive. Herein, an ultrastrong coordinated cosolvation diluent, 2,3-difluoroethoxybenzene (DFEB), is designed to modulate solvation structure and tailor Li 2 O-dominated SEI for stable LMBs. In the DFEB-based LHCE (DFEB-LHCE), DFEB intensively participates in the first solvation shell and synergizes with FSI – to tailor an Li 2 O-dominated inorganic-rich SEI which is different from the LiF-dominated SEI formed in conventional LHCE. Benefiting from this special SEI architecture, a high Coulombic efficiency (CE) of 99.58% in Li||Cu half cells, stable voltage profiles, and dense and uniform lithium deposition, as well as effective inhibition of Li dendrite formation in the symmetrical cell, are achieved. More importantly, the DFEB-LHCE can be matched with various cathodes such as LFP, NCM811, and S cathodes, and the Li||LFP full cell using DFEB-LHCE possesses 85% capacity retention after 650 stable cycles with 99.9% CE. Especially the 1.5 Ah practical lithium metal pouch cell achieves an excellent capacity retention of 89% after 250 cycles with a superb average CE of 99.93%. This work unravels the superiority of the Li 2 O-dominated SEI and the feasibility of tailoring SEI components through modulation of solvation structures.