Alloy-assisted stabilization of thin Li metal anode in pouch-type cell

Abstract

Lithium metal batteries (LMBs) with thin lithium (Li) metal anodes deliver higher energy densities compared to the traditional LMBs with thicker Li anodes. However, Li metal anode faces many issues such as uncontrolled dendrite formation, resulting in poor cycle life and low coulombic efficiency (CE). To address these issues, we present metal trifluoromethanesulfonates (Mx(CF3SO3)y, MTFMS, where M = Li, Zn, Cu, Ag, Mg) as electrolyte additives to suppress dendrite formation and provide better cyclability. Interestingly, the metal (M) formed from MTFMS brings a stable Li deposition owing to its alloying reaction with Li. In addition, a stable LiF-rich solid electrolyte interphase (SEI) is derived from -CF3 functional groups which further suppress dendrite formation. Li||Cu cells cycled with MTFMS exhibit higher initial CE up to 96.6% with significantly buffered overpotential. Furthermore, Li||Li symmetric cells composed of MTFMS show a superior cyclability for over 500 h. An LiNi0.8Mn0.1Co0.1O2 (NMC811) full cell assembled with a thin Li metal anode (≤ 50 µm) under practically controlled N/P and E/C ratios in pouch cell mode reveals a stabilized capacity retention of up to 82.3% for 150 cycles, along with excellent rate capability, particularly with MgTFMS. The introduction of MTFMS as an additive will pave a new framework in the design of high energy density LMBs using thin Li metal anode.