In-situ construction of g-C3N4/carbon heterostructure on graphene nanosheet: An efficient polysulfide barrier for advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have been considered as the future potential energy storage system with advantages of high energy density (2600 Wh kg-1), eco-friendliness and low cost. However, the poor conductivity and serious shuttle effects of polysulfides block their application. Herein, g-C3N4/carbon heterostructure on graphene nanosheet (PCNG) is constructed via phenyl-modified strategy and in-situ thermal polycondensation, which has a unique electron cloud distribution with excellent sulfur immobilization ability as well as good electroconductivity. As a result, Li-S cells with simple S/C cathodes and PCNG interlayers show a high initial capacity of 1192 mAh g-1 at 0.1 C, and an ultra-long lifespan with a slow capacity attenuation of 0.050% per cycle after 800 cycles. The cell with PCNG/PP separator also has a stable cycle performance at high area sulfur loading of 7 mg cm-2. These findings provide a new sight on functionalizing g-C3N4 for application in Li-S electrochemistry.