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

• A g -C 3 N 4 /carbon heterostructure on graphene nanosheet is synthesized. • The phenyl-modified strategy for g-C 3 N 4 is proven to effectively alleviate the “shuttle effect”. • The graphene works as the 2D framework and facilitates electron transport. • The in-situ thermal process builds a good electronic channel between g -C 3 N 4 and graphene. • The g -C 3 N 4 /carbon heterostructure exhibits good electrochemical performance. 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-C 3 N 4 /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 0.1C, 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-C 3 N 4 for application in Li-S electrochemistry.