Trimethylsilyl Azide (TMSN₃) Enhanced Li-O₂ Battery Electrolytes

Li-O₂ batteries (commonly called Li-air batteries) are plagued by reactions of reduced oxygen intermediates at the cathode, as well as instability of ether-based electrolytes on the Li metal anode. Here, we study the effect of adding a non-redox mediator, trimethylsilyl azide (TMSN₃), to a diglyme-based electrolyte. The TMSN₃ enables formation of a stable bis(TMS)peroxide from Li₂O₂ during discharge. The bis(TMS)peroxide can subsequently undergo decomposition during charging with a reduction in overpotential of up to 1000 mV relative to the decomposition potential of Li₂O₂. TMSN₃ also results in formation of a robust solid electrolyte interphase (SEI), consisting of a composite of lithium nitride, reduced nitrates, and siloxanes that appear to limit both Li dendrite formation and bis(TMS)peroxide shuttling. The synergistic effect of TMSN₃ on both the cathode and anode enables a high areal capacity of 3.8 mAh cm^-2 at a high rate of 637 μA cm^-2 for up to 30 cycles.