Activated graphene with tailored pore structure parameters for long cycle-life lithium-sulfur batteries

Activated graphene (AG) with various specific surface areas, pore volumes, and average pore sizes is fabricated and applied as a matrix for sulfur. The impacts of the AG pore structure parameters and sulfur loadings on the electrochemical performance of lithium-sulfur batteries are systematically investigated. The results show that specific capacity, cycling performance, and Coulombic efficiency of the batteries are closely linked to the pore structure and sulfur loading. An AG3/S composite electrode with a high sulfur loading of 72 wt.% exhibited an excellent long-term cycling stability (50% capacity retention over 1,000 cycles) and extra-low capacity fade rate (0.05% per cycle). In addition, when LiNO3 was used as an electrolyte additive, the AG3/S electrode exhibited a similar capacity retention and high Coulombic efficiency (similar to 98%) over 1,000 cycles. The excellent electrochemical performance of the series of AG3/S electrodes is attributed to the mixed micro/mesoporous structure, high surface area, and good electrical conductivity of the AG matrices and the well-distributed sulfur within the micro/mesopores, which is beneficial for electrical and ionic transfer during cycling.