Enabling stable sodium metal cycling by sodiophilic interphase in a polymer electrolyte system

Abstract

Enabling highly reversible sodium (Na) metal anodes in a polymer electrolyte (PE) system is critical for realizing next-generation batteries with lower cost, higher energy, and improved safety. However, the uneven Na deposition and high Na/PE interphase resistance lead to poor reversibility and short cycle life of Na metal anodes. To tackle these problems, here a variety of metal nanoparticles (M-np, M = Al, Sn, In or Au) are deposited onto copper (Cu) foils to synthesize binder-free M-np@Cu substrates for Na plating/stripping. Notably, the Au-np@Cu substrate provides abundant preferential nucleation/growth sites, decreasing Na nucleation barrier and thus promoting uniform Na deposition. Accordingly, stable Na metal anodes are achieved with high reversible capacities, long cycle life, and high usage of Na. With the Au-np@Cu/Na anode and PE, the full cell using a commercial bulk sulfur cathode exhibits a reversible capacity of >400 mAh g−1 with near-100% Coulombic efficiency over 200 cycles.