High sulfur loading, rGO-linked and polymer binder-free cathodes based on rGO wrapped N,P-codoped mesoporous carbon as sulfur host for Li-S batteries

Lithium-sulfur batteries have been recognized as one of the most promising candidates for the next-generation high energy storage devices. However, the polysulfides shuttling, low electronic conductivity of sulfur and its solid reduction products, as well as the large volume expansion during S <-> Li2S transformation are the main obstacles to prohibit their commercialization. Here we to resolve these problems, by using N,P-codoped mesoporous carbon coated with rGO protective layers as sulfur host and rGO as conductive binder. The N,P-codoped mesoporous carbon could provide both physical adsorption and chemical interactions due to the micro/mesoporous pore structures, high surface area and P-S bonds, O-S bonds as well as good surface affinity. The rGO protective layers could well entrap sulfur in the host materials and inhibit polysulfides escaping from cathodes and shuttling. Most importantly, this protective layers combined with rGO conductive binders could also form a continuous conductive networks for electrons transportation, Li ions transfer channels through atomic scaled defects and mechanical protection layers to accommodate the severe volume expansion and finally ensuring 80-90 wt% sulfur loading in the cathode material. The unique designed cathodes exhibit excellent electrochemical performances with specific capacity as high as 1469 mAh/g at 0.1 C, a reversible specific capacity of 977 mAh/g after 100 cycles at 0.5 C rate and a low self-discharge behavior.