Synergistic regulation of lithium nucleation and anion-rich solvation structure via silver trifluoroacetate additive for stable lithium metal anodes

Abstract

Lithium (Li) metal, owing to its high theoretical specific capacity and low electrochemical potential, is considered one of the most promising anode materials for next-generation rechargeable batteries. However, interfacial instability severely hinders the practical application of Li anodes. Constructing a robust solid electrolyte interphase (SEI) with optimized chemical composition and structure has been recognized as an effective strategy to overcome this challenge. Here, we propose silver trifluoroacetate (AgTFA) as a multifunctional electrolyte additive that synergistically regulates Li nucleation and promotes the formation of an anion-rich solvation structure. Through a spontaneous in situ displacement reaction, uniformly distributed silver nanoparticles (Ag NPs) are generated on the Li surface, providing abundant lithiophilic nucleation sites to enable homogeneous Li deposition. Meanwhile, trifluoroacetate anions (TFA-) with an ultrahigh donor number, together with NO3- anions participating in Li+ solvation, markedly reduce the desolvation barrier and facilitate the formation of a LiF-Li3N-rich SEI. As a result, Li||Li symmetric cells exhibit remarkable cycling stability of up to 2,500 hours at 0.5 mA·cm-2/0.5 mAh·cm-2, while Li||LiFePO4 full cells deliver a high discharge capacity of 139.8 mAh·g-1 with an excellent capacity retention of 97.28% after 200 cycles at 1.0 C. This work demonstrates a feasible strategy for constructing durable SEI layers by coupling Li nucleation regulation with anion-rich solvation chemistry.