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.