1T-2H Mixed-Phase MoS2 Stabilized with a Hyperbranched Polyethylene Ionomer for Mg2+/Li+ Co-Intercalation Toward High-Capacity Dual-Salt Batteries

Dual-salt magnesium/lithium-ion batteries (MLIBs) benefit from fast lithium ion diffusion on the cathode side while providing safety due to the dendrite-free Mg2+ stripping/plating mechanism on the anode side. Bulk MoS2 (B-MoS2), as a cathode for magnesium-ion batteries (MIBs), suffers from low conductivity and relatively van der Waals gaps and, consequently, resists against divalent Mg2+ insertion due to the high Coulombic interactions. In MLIBs, it exhibits a Daniell-cell type mechanism with the sole accommodation of Li+. In this paper, the synthesis of a 1T/2H mixed-phase MoS2(MP-MoS2) modified with a hyperbranched polyethylene ionomer, I@MP-MoS2, for high-capacity MLIBs with a distinct Mg2+/Li+ co-intercalation mechanism is reported. Benefiting from the enhanced conductivity (due to 53% metallic 1T phase), expanded van der Waals gaps (79% expansion compared to B-MoS2, 1.11 vs 0.62 nm), and enhanced interactions with THF-based electrolytes following the modification, I@MP-MoS2 shows a dramatically increased Mg2+ storage compared to its parent analogue (144 mAh g(-1) vs approximate to 2 mAh g(-1) at 20 mA g(-1)). In MLIBs, I@MP-MoS2 is demonstrated to exhibit remarkable specific capacities up to approximate to 270 mAh g(-1) at 20 mA g(-1) through a Mg2+/Li+ co-intercalation mechanism with 87% of capacity retention over 200 cycles at 100 mA g(-1).