Tuning the LUMO Energy of an Organic Interphase to Stabilize Lithium Metal Batteries

Abstract

Interfacial stability is considered as a priority in high-energy lithium metal batteries (LMBs), stemming from the extremely low electrochemical potential of Li metal and its intrinsic high reactivity. The naturally grown solid–electrolyte interphase (SEI) containing organic compositions (e.g., R1OCOOR2, ROLi) and inorganic compositions (e.g., Li2CO3, Li3N) is thermodynamically unstable against Li metal. Herein, we created a highly stable organic interphase (HSOI) with a well-tuned LUMO energy to improve the antireduction ability of SEI components and enhance the long-term cyclability of LMBs. Employing trifluoromethyl functional groups (−CF3) in the molecule structure of a SEI can significantly tune the orbital energies and the HOMO–LUMO gap due to the strong electron-withdrawing property of −CF3 functional groups. With the protection of HSOI, cells can cycle more than 1300 h, which is 5-fold improvement in cell lifetime, demonstrating the vital role of the HSOI layer on the stability of LMBs.