Incorporating different MoSx/rGO catalysts in interlayer and cathode to enhance Li-S battery performance: A dual-catalyst strategy

Lithium polysulfide (LPS) shuttling remains a fundamental challenge that limits the cycle life of Li-S batteries (LSBs). Though incorporating electrocatalysts in the S cathode improves the LPS conversion and confinement, it is difficult to fully resolve this issue with a single electrocatalyst because LSB redox chemistry involves multiple redox steps with a series of soluble LPSs in sequential reactions. Here, we demonstrate that a dual-catalyst strategy can significantly enhance the LPS conversion kinetics, specific capacity, and long-term cycling stability compared to mono-catalyst approaches. To achieve this, we employ a thin catalyst coating on the S-C cathode as a catalytic interlayer, which promotes LPS conversion and improves their retention in the cathode. A family of molybdenum sulfide (MoS x ) materials supported on reduced graphene oxide (rGO) nanosheets is synthesized using specific microwave heating followed by thermal treatment at 250 °C or 600 °C to form 1D chain-like amorphous MoS 3 and 2D nanosheet crystalline MoS 2 , denoted as 1D MoS 3 /rGO-250 and 2D MoS 2 /rGO-600, respectively. The 1D MoS 3 /rGO-250 exhibits a higher LPS adsorption and higher specific capacity, whereas the 2D MoS 2 /rGO-600 delivers superior conductivity, faster kinetics, and long-term stability, albeit at slightly lower specific capacity. When combining MoS 2 /rGO-600 in the S-C cathode and MoS 3 /rGO-250 in the interlayer (denoted as S-M6//M2), the synergistic effect leads to a remarkable initial specific capacity of ∼1,417 mAh g -1 at 0.1C and ∼1,000 mAh g -1 at 1C, with a good capacity retention over 500 cycles.