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.