Single atomic cobalt catalyst significantly accelerates lithium ion diffusion in high mass loading Li2S cathode

Abstract

It is widely accepted that catalysts in batteries can decrease the energy barriers of conversion reactions. However, little attention has been paid to their influence on ionic diffusion in the electrode or across the interface. Herein, we report that lithium ion diffusivity can be significantly accelerated in an intrinsically electrode by atomically-distributed metal catalyst. Electrochemical measurements have found single atomic cobalt catalyst embedded in a nanocarbon network is capable of increasing the kinetics of lithium ion, providing rapid conversion reaction rate in an ultrahigh-rate Li2S battery. Meanwhile, density functional theory simulations have revealed that the lithium ion diffusion barrier on a nanocarbon surface is highly sensitive to the dopant atoms and can be decreased by introduction of cobalt atoms. The synergetic effects of the well-known Li2S decomposition catalysis and the lithium ion diffusion acceleration allow us to achieve a high Li2S mass loading cathode with superior rate performance and reversibility. The as-prepared Li2S electrode converted from cheap Li2SO4 precursors can deliver a high rate capacity (441 ​mA ​h ​g-1 based on Li2S at 10 ​C) and long lifespan for 1500 cycles at 2 ​C with average capacity fading of 0.04% per cycle. Impressively, the high areal mass loading cells display a specific capacity of 340 ​mA ​h ​g-1 based on Li2S mass at 23.4 ​mA ​cm-2 (5 ​C) and a long cycle life (2.26 ​mA ​h ​cm-2 at 6.77 ​mA ​cm-2 after 200 cycles), which have not been reported for Li2S cathodes.