Alloy-assisted stabilization of thin Li metal anodes in pouch-type cells

Abstract

Lithium metal batteries (LMBs) with thin lithium (Li) metal anodes deliver higher energy densities compared to traditional LMBs with thicker Li anodes. However, Li metal anodes suffer from uncontrolled dendrite formation, resulting in poor cycle life and low coulombic efficiency (CE). To address these issues, we present metal trifluoromethanesulfonates (M_x(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 enables stable Li deposition through its alloying reaction with Li. In addition, a stable LiF-rich solid electrolyte interphase (SEI) is derived from –CF₃ functional groups, further suppressing dendrite formation. Li‖Cu cells cycled with MTFMS exhibit a higher initial CE of up to 96.6% with significantly buffered overpotential. Furthermore, Li‖Li symmetric cells composed of MTFMS show superior cyclability for over 500 h. A LiNi_0.8Mn_0.1Co_0.1O₂ (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 revealed 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 establish a new framework in the design of high-energy-density LMBs using thin Li metal anodes.