Cobalt-induced highly-electroactive Li2S heterostructured cathode for Li-S batteries

Abstract

Lithium sulfide (Li2S) is a promising cathode material with a high theoretical capacity (1166 mA h g−1) that can be paired with nonlithium-metal anodes, which can eliminate the safety issue related with lithium anode. Nevertheless, its poor electronic conductivity and low Li ion diffusion lead to the high activation barrier of Li2S and sluggish kinetic conversion to polysulfides, hindering its commercialization. Herein, Li2S particles coated by Co nanomaterial-decorated porous carbon shells (Li2S/Co@C) are catalytically synthesized in-situ as the Li2S-Co heterostructures to enhance Li2S reactivity and its kinetic conversion via a carbothermic reduction. This Li2S/Co@C shows an ultra-low activation potential of 3.12 V, smaller by 0.74 V compared with commercial Li2S. Significantly, it presents an initial reversible capacity of 1006 mA h g−1 and maintains a high reversible capacity of 335 mA h g−1 at 0.1 C (1 C = 1166 mA g−1) after 500 cycles. An outstanding rate capacity is also achieved with a reversible capacity of 148 mA h g−1 at 3 C. More importantly, in-/ex-situ characterizations underscore that Co nanomaterials can serve as an Li2S-Co heterostructure catalyst to enhance the reactivity of Li2S, lithium polysulfides, and sulfur, thereby achieving high performance in Li-S batteries.