Boosting Li–S battery by rational design of freestanding cathode with enriched anchoring and catalytic N-sites carbonaceous host

Abstract

Lithium-sulfur (Li–S) batteries are considered to be a promising energy storage owing to high energy density and low cost. However, the S cathodes are still suffering from poor cycle life and low Coulombic efficiency due to ‘shuttle effect’ of lithium polysulfide. Herein, we report a novel and effective strategy to fabricate a free-standing Li–S battery cathode with enriched anchoring and catalytic N-sites host. Benefiting from synergistic effects of multifunctional porous carbon nanofiber host (g-C3N4@PCNF), the g-C3N4@PCNF/S cathode achieves good flexibility and excellent cycling retention, such as stable long cycle performance with a capacity decay of only 0.056% per cycle over 500 cycles at 1.0 A g−1. The excellent performance of g-C3N4@PCNF/S cathode can be mainly attributed to: (i) the interconnected network and internal porous structure of PCNF offering free space for S-loading and volume change during charge/discharge; (ii) the 3D g-C3N4@PCNF host providing an efficient electron/Li+ transport highway for fast interfacial reaction kinetics; (iii) the catalytic effect of g-C3N4 promoting rapid redox conversion of S species and retarding polysulfide shuttling. This effective strategy has demonstrated great potential as good candidates for commercial flexible and durable Li–S batteries.