A binder-free lithium-sulfur battery cathode using three-dimensional porous g-C3N4 nanoflakes as sulfur host displaying high binding energies with lithium polysulfides

A binder-free porous graphene like-C3N4 nanoflakes/carbon cloth/sulfur lithium-sulfur battery cathode prepared through a thermal polymerization method is presented. On the basis of the density functional theory calculations on the bonds between g-C3N4 and lithium polysulfides including Li2S4, Li2S6 and Li2S8, it is found the cathode possesses robust binding energies towards polysulfides and an improved conductivity, which would enable a strong suppression for the transfer of the lithium polysulfides. The prepared porous binder-free cathode exhibits a high capacity of 892 mAh g−1 after cycling 250 times at 0.2 C and a well-recoverable rate-performance, which indicates a good potential to construct high-performance lithium-sulfur batteries for practical applications.