ZIF-67 on Sulfur-Functionalized Graphene Oxide for Lithium–Sulfur Batteries

How to overcome the problem of fast capacity fading and low sulfur utilization is the key to promote the practical applications of lithium–sulfur (Li–S) batteries. Based on the fact that sulfur-functionalized graphene oxide (GO-S) can avoid the loss of sulfur/polysulfides through the strong C–S interaction, and the zeolitic imidazolate framework (ZIF-67) can capture sulfur and catalyze lithium polysulfide (Li2Sx, 4 ≤ x ≤ 8), the combination of ZIF-S (ZIF-67 after combining with sulfur) with GO-S can be expected to be an excellent electrode material for Li–S batteries due to the synergistic effect. Herein, ZIF-S@GO-S (n) nanocomposites (n = 1, 2, and 3 for the mass ratio of ZIF-67/GO of 4:1, 6:1, and 8:1, respectively) as the cathode materials in Li–S batteries were successfully fabricated, and ZIF-S@GO-S (2) showed better electrochemical performances and cycle stability with a high specific capacity of 1529.5 mA h g–1 at the initial cycle and 792 mA h g–1 after 500 cycles at 0.1 C (1 C = 1675 mA h g–1). The fact that ZIF-S@GO-S (n) can simultaneously improve the conductivity and utilization of S (C–S···S8 and C–S···SxLi2) and the conversion kinetics of Li2Sx (4 ≤ x ≤ 8) provides a new avenue for designing and fabricating promising cathodes for high-performance Li–S batteries.