A Friendly Soluble Protic Additive Enabling High Discharge Capability and Stabilizing Li Metal Anodes in Li-O2 Batteries

Promoting the solution phase formation of Li2O2 rather than on the cathode surface is a key issue for high-performance Li-O-2 batteries. Protic additives have been reported to guide the discharge of Li2O2 in the electrolyte solution, while further advances are stalled by the intrinsical reactivity to Li metal to deteriorate the lifespan of Li-O-2 batteries. Herein, rhodamine B (RhB), a protic additive, is first introduced into electrolyte as a phase-transfer catalyst to achieve solution phase formation of Li2O2. The yield of Li2O2 is 90.79%, and the discharge capacity is 46 000 mAh g(carbon)(-1) at current density of 1000 mA g(carbon)(-1), which is 23-fold higher than that of blank electrolyte. Density functional theory calculations further demonstrate the feasibility of RhB to boost solution phase discharge. Most notably, the free chlorine ion in RhB assists the in situ formation of a stable Li+-conducting solid electrolyte interphase to protect Li anode from corrosion and dendrite formation during cycling. As a result, Li||Li symmetric cells exhibit a long cycle performance up to 1300 h at 1 mA cm(-2) with low hysteresis voltage. Benefiting from the above results, Li-O-2 batteries with RhB present long cycle stability.