Improvement of Energy Capacity with Vitamin C Treated Dual-Layered Graphene-Sulfur Cathodes in Lithium-Sulfur Batteries

A graphene-based cathode design for lithium-sulfur batteries (LSB) that shows excellent electrochemical performance is proposed. The dual-layered cathode is composed of a sulfur active layer and a polysulfide absorption layer, and both layers are based on vitamin C treated graphene oxide at various degrees of reduction. By controlling the degree of reduction of graphene, the dual-layered cathode can increase sulfur utilization dramatically owing to the uniform formation of nanosized sulfur particles, the chemical bonding of dissolved polysulfides on the oxygen-rich sulfur active layer, and the physisorption of free polysulfides on the absorption layer. This approach enables a LSB with a high specific capacity of over 600 mAhg(sulfur)(-1) after 100 cycles even under a high current rate of 1C (1675 mAg(sulfur)(-1)). An intriguing aspect of our work is the synthesis of a high-performance dual-layered cathode by a green chemistry method, which could be a promising approach to LSBs with high energy and power densities.