Suppressing Interfacial Side Reactions of Anode-Free Lithium Batteries by an Organic Salt Monolayer

Anode-free lithium (Li) batteries are attractive owing to their high energy density. However, Li loss by forming solid-electrolyte interphase (SEI) during cell activation leads to a ≈25% capacity decrease, and the capacity constantly fades upon cycling due to the side reactions on the copper (Cu) current collector. This paper reports high-initial-efficiency, long-cycle-life, and long-calendar-life anode-free Li batteries by using an organic Li salt monolayer bonded on Cu. The functional salt, namely lithium ((4-carbamoylphenyl)sulfonyl)(fluorosulfonyl)imide, electrochemically decomposes and passivates the Cu surface, which reduces Li sacrifice by SEI formation and suppresses galvanic Li corrosion and Li-electrolyte reactions during cycling. This work records a LiF-rich interphase on Cu and guided Li nucleation and growth. A 93.6% initial Li deposition efficiency is realized in a regular carbonate electrolyte, and the galvanic current is decreased to ≈40 nA cm^-2 , merely one-tenth of bare Cu. After cell activation, 95.2% capacity is retained for a Cu|LiNi_0.8 Mn_0.1 Co_0.1 pouch cell with a theoretical capacity of 200 mAh, and the cell is operated over 600 cycles. Calendar aging showed no damage to cell performance.