Enabling Ultrafast Single Mg²⁺ Insertion Kinetics of Magnesium-Ion Batteries via In Situ Dynamic Catalysis and Re-equilibration Effects

Magnesium-ion batteries (MIBs) have great potential inlarge-scaleenergy storage field with high capacity, excellent safety, and lowcost. However, the strong solvation effect of Mg2+ willlead to the formation of solvated ions in electrolytes with largersize and sluggish diffusion/reaction kinetics. Here, the concept ofinterfacial catalytic bond breaking is first introduced into the cathodedesign of MIBs by hybriding MoS2 quantum dots with VS4 (VS4@MQDs) as the cathode. The "in situdynamic catalysis and re-equilibration" effects can catalyzethe Cl-Mg bond breaking and trigger single Mg2+ insertion/extractionchemistries, which can significantly accelerate the diffusion andreaction kinetics, as verified by the decreased diffusion energy barriers(0.26 eV for Mg2+ vs 2.47 eV for MgCl+) andfast diffusion coefficient. Benefitting from these dynamic catalysiseffects, the constructed VS4@MQD-based MIBs deliver a highdischarge capacity of similar to 120 mA h g(-1) at 200mA g(-1) and a long-term cyclic stability of 1000cycles at 1 A g(-1). The improved performance anddetailed characterizations well prove that the active ions in MIBschange from MgCl+/Mg2Cl3+ to Mg2+ with fast kinetics.