Demonstration of MAX phases as triple functional artificial solid electrolyte interphase for ultralong life lithium metal anodes.

Solid electrolyte interphase (SEI) has significant role in controlling lithium (Li) dendrites. However, lack of chemical stability, mechanical strength and self-perfection for conventional SEI cannot persistently suppress Li dendrites, leading to inferior cycling life. Herein, MAX phases (TiSnC and TiSC) as triple functional artificial SEI (ASEI) with high modulus, chemical stability and self-smoothing ability are introduced on Li foils (TiSnC@Li and TiSC@Li) for ultralong life Li metal anodes (LMAs). The high mechanical strength with lithiophilicity of the MAX can induce uniform Li deposition and suppress dendrite growth, while the excellent chemical stability and self-smoothing ability of the MAX guarantee the consistency of the ASEI, achieving ultralong life of the LMAs. As a result, the TiSnC@Li||Li@TiSnC half-cells demonstrate ultralong cycling performance of 5000 h at 5 mAh cm and 5 mA cm. The TiSnC@Li||LiFePO(LFP) full-cells demonstrate ultralong stability up to 3000 cycles at 5C. At harsh conditions including 24.3 mg cm of LFP, 6.0 g (Ah) of electrolyte and 2.6 of negative/positive ratio, the TiSnC@Li||LFP full-cells maintain 2.9 mAh cm after 130 cycles at 0.3C. This work demonstrates the MAX phases with high modulus, chemical stability and self-smoothing ability as triple functional ASEI for metal anode protection.