N-doped porous carbon coated g-C3N4/ g-C3N4 heterojunction for polysulfide restriction and catalytic conversion towards enhanced lithium-sulfur batteries

Notorious shuttle effects and poor electrical conductivity of S have long hindered the commercialization of lithium-sulfur (Li-S) batteries. Herein, N-doped porous carbon coated graphitic carbon nitride heterojunction (g-C3N4/ g-C3N4 @C) composites was prepared by growing g-C3N4/ g-C3N4 heterojunction on the pores of the porous carbon. The effective interface adhesion of g-C3N4/ g-C3N4 heterojunction and high conductive porous carbon served as S host insure the initial specific capacity of 752 mAh/g at 1 C, reversible capacity of 496 mAh/g at 1 C after 400 cycles, and higher rate capacity of 468 mAh/g at 2 C after 500 cycles for Li-S batteries. The mechanism of this ternary synergetic system for enhancement of electrochemical performance is based on effective interface adhesion and conductive property caused by different band energies of g-C3N4 and the N-doped porous carbon.