Abstract
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 (MoSx) 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 MoS3 and 2D crystalline MoS2 nanosheetst, denoted as 1D MoS3/rGO-250 and 2D MoS2/rGO-600, respectively. The 1D MoS3/rGO-250 exhibits a higher LPS adsorption and higher specific capacity, whereas the 2D MoS2/rGO-600 delivers superior conductivity, faster kinetics, and long-term stability, albeit at slightly lower specific capacity. When combining MoS2/rGO-600 in the S-C cathode and MoS3/rGO-250 in the interlayer (denoted as S-M6∖M2), the synergistic effect leads to a remarkable initial specific capacity of ∼1417 mAh g−1 at 0.1C and ∼1000 mAh g−1 at 1C, with good capacity retention over 500 cycles.