Co-recrystallization induced self-catalytic Li2S cathode fully interfaced with sulfide catalyst toward a high-performance lithium-free sulfur battery

Lithium sulfide (Li2S) is a promising cathode for a practical lithium-sulfur battery as it can be coupled with various safe lithium-free anodes. However, the high activation potential (>3.5 V) together with the shuttling of lithium polysulfides (LiPSs) bottleneck its practical uses. We are trying to present a catalysis solution to solve both problems simultaneously, specially with twinborn heterostructure to shoot off the trouble in interfacial contact between two solids, catalyst and Li2S. As a typical example, a Co9S8/Li2S heterostructure is reported here as a novel self-catalytic cathode through a co-recrystallization followed by a one-step carbothermic conversion. Co9S8 as the catalyst effectively lowers the Li2S activation potential (<2.4 V) due to fully integrated and contacted interfaces and consistently promotes the conversion of LiPSs to suppress the shuttling. The obtained freestanding cathode of Co9S8/Li2S heterostructures encapsulated in three-dimensional graphene shows a high capacity, reaching 92.6% of Li2S theoretical capacity, high rate performance (739 mAh g(-1) at 2 C), and a low capacity fading (0.039% per cycle at 1 C over 900 cycles). Even under a high Li2S loading of 12 mg cm(-2) and a low E/S ratio of 5 mu LmgLi2S-1$$ 5\kern0.24em \upmu \mathrm{L}\kern0.4em {\mathrm{mg}}_{{\mathrm{Li}}_2{\mathrm{S}}<^>{-1}} $$, 86% of theoretical capacity can be utilized.