Rational design of graphene @ nitrogen and phosphorous dual-doped porous carbon sandwich-type layer for advanced lithium-sulfur batteries

Lithium sulfur (Li-S) batteries show great prospect as a next generation high energy density rechargeable battery systems. However, the practical utilization of Li-S batteries is still obstructed by the shuttle effects which inducing the fast capacity fading and the loss of active sulfur. Herein, a special graphene @ nitrogen and phosphorous dual-doped porous carbon (N-P-PC/G) is presented to modify a commercial separator for an advanced Li-S battery. The N-P-PC/G nanosheet employs graphene layer as an excellent conductive framework covered with uniform layers of N, P dual-doped porous carbon on both sides which possessing massive interconnected meso-/micropores. It is demonstrated that the N-P-PC/G-modified separator can suppress the shuttle effects by coupling interactions including physical absorption, chemical adsorption and interfacial interaction. With the aid of the N-P-PC/G-modified separator, the pure sulfur cathode with high-sulfur loading of 3 mg cm(-2) offers a high initial discharge capacity of 1207 mA h g(-1) at 0.5 C (1 C = 1675 mA h g(-1)), and a maintained capacity of 635 mA h g(-1) (fading rate of only 0.095% per cycle), after 500 cycles. This work suggests that combining hybrid nanocarbon with multi-heteroatom doping to modify the commercial separator is an effective approach to obtain high electrochemical performance Li-S batteries.