Navigating Lithium Fluoride Formation by Electrode Interphase Engineering with Amphiphilic Covalent Organic Frameworks based Electrolyte

Abstract

Regulating the Li+ and anions directionally in electrolyte to achieve LiF-rich solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) is highly desired. Herein, we achieve the electrode interphase engineering with a kind of nonsacrificial amphiphilic covalent organic framework (i.e. TGBM-COF) based electrolyte. Specifically, TGBM-COF can function as a zwitterionic regulator in electrolyte to tune the Li + solvation structure for stable LiF-rich SEI/CEI in lithium-metal batteries (LMBs). Proved by comprehensive simulations and characterizations, the obtained TGBM-COF with regular distributed oxygen-tails could adsorb Li + ions and the positively charged guanidinium units could selectively adsorb PF6 -anions to form an anion-derived solvation structure, thus facilitating PF6 -anions to decompose into LiF at both electrodes. Meanwhile, its non-sacrificial and cationic characteristics ensure the unform dispersion in the electrolyte to achieve long-term battery stability. Noteworthy, the prepared TGBM-COF electrolyte enables stable cycling in Li||LFP full cell under rates from 0.2 C to 15 C, and it delivers a remarkable high-rate capacity at 8 C even after 900 cycles. This study offers a novel strategy for designing COFs as zwitterionic regulators for high-performance LMBs.