Achieving highly stable Li–O2 battery operation by designing a carbon nitride-based cathode towards a stable reaction interface

Abstract

Aprotic Li–O₂ batteries have attracted a great deal of attention because of their potential to offer much higher energy density than those provided by commercialized lithium-ion batteries. However, their reversible operation is plagued by serious side-reactions from liquid electrolytes and/or carbon-based materials. Recently, carbon-free materials have been proposed and utilized to construct stable cathodes for Li/O₂ chemistry. Different from most of the previously reported metal-based carbon-free cathodes, herein we report a non-metal-based carbon-free cathode support consisting of mesoporous boron-doped carbon nitride (m-BCN) and demonstrate its excellent stability and activity for Li/O₂ chemistry. Benefiting from the introduction of evenly distributed RuO₂ nanoparticles (1–2 nm) in the pores of the boron-doped carbon nitride support, excellent cycle stability with a low overpotential (141 cycles with a pristine Li anode which is extended to 227 cycles after replacing it with a new Li anode at 0.5 mA cm⁻²) and superior rate capability (1.28 mA h cm⁻² at 1 mA cm⁻²) are obtained. This impressive performance is ascribed to the enhanced stability and activity of such designed cathodes, which is supported by the fact that reversible formation and decomposition of Li₂O₂ with no accumulation of Li₂CO₃ is detected during cycling. These results demonstrate that manipulating cathode materials towards stable reaction interfaces is essential for alleviating the formation of by-products and improving the performance of Li–O₂ batteries.