Enabling Ultrafast Single Mg<sup>2+</sup> Insertion Kinetics of Magnesium-Ion Batteries via In Situ Dynamic Catalysis and Re-equilibration Effects
Rongrui Deng, Shuangshuang Tan, Zhongting Wang, Rong Li, Guanjie Lu, Baihua Qu, Le Tong, Ronghua Wang, Chaohe Xu, Guangsheng Huang, Jingfeng Wang, Aitao Tang, Xiaoyuan Zhou, Fusheng Pan
Abstract
Magnesium-ion batteries (MIBs) have great potential in large-scale energy storage field with high capacity, excellent safety, and low cost. However, the strong solvation effect of Mg 2+ will lead to the formation of solvated ions in electrolytes with larger size and sluggish diffusion/reaction kinetics. Here, the concept of interfacial catalytic bond breaking is first introduced into the cathode design of MIBs by hybriding MoS 2 quantum dots with VS 4 (VS 4 @MQDs) as the cathode. The “in situ dynamic catalysis and re-equilibration” effects can catalyze the Cl–Mg bond breaking and trigger single Mg 2+ insertion/extraction chemistries, which can significantly accelerate the diffusion and reaction kinetics, as verified by the decreased diffusion energy barriers (0.26 eV for Mg 2+ vs 2.47 eV for MgCl + ) and fast diffusion coefficient. Benefitting from these dynamic catalysis effects, the constructed VS 4 @MQD-based MIBs deliver a high discharge capacity of ∼120 mA h g –1 at 200 mA g –1 and a long-term cyclic stability of 1000 cycles at 1 A g –1 . The improved performance and detailed characterizations well prove that the active ions in MIBs change from MgCl + /Mg 2 Cl 3+ to Mg 2+ with fast kinetics.