Relieving the "Sudden Death" of Li-O2 Batteries by Grafting an Antifouling Film on Cathode Surfaces.

The "sudden-death" phenomenon has been frequently encountered during discharging of Li-O2 batteries and has been ascribed to the growth of a blocking film of Li2O2 on the cathode surface. Recent fundamental study revealed that this dilemma could be addressed by discharging Li2O2 in the electrolyte solution rather than on the cathode surface. However, even for Li-O2 batteries operated under the conditions favorable for the solution growth of Li2O2, sudden death still persists and its origin remains incompletely understood. Herein, by using a combination of in situ spectroscopy and theoretical calculation, we reveal that sudden death of Li-O2 batteries operated under the conditions (e.g., low discharge current density and high donor number electrolyte solvent) favorable for discharging Li2O2 in the electrolyte solutions is caused by adventitious adsorption of a minor quantity of Li2O2, which triggers a rapid transition of Li2O2 growth mode from solution- to surface-mediated growth. Moreover, a cathode surface modification strategy has been developed to effectively retard the Li2O2 adsorption and therefore significantly alleviate the sudden death of Li-O2 batteries.