Amorphous quantum dots enable V₂O₅ with superior Mg storage

Mg-ion batteries (MIBs) possess promising advantages over monovalent Li-ion battery. However, the exploitation of desirable cathode materials encounters the dilemma of sluggish reaction kinetics caused by strong coulomb interaction between Mg²⁺ and cathode. Reasonable electrode structure design is of great importance for achieving fast Mg²⁺ intercalation kinetics. Herein, a novel configuration composed of sub-5 nm amorphous V₂O₅ quantum dots and nitrogen-doping carbon nanofibers (a-V₂O₅-QDs@NCNFs) was elaborately designed and fabricated. Sub-5 nm QDs provide shorter diffusion path and more storage sites for Mg²⁺. Simultaneously, a large range of disorder states in amorphous structure can provide more open diffusion channels for Mg²⁺ transport. In addition, NCNFs play a crucial part in relieving the volumetric strains of V₂O₅ and maintaining the structural integrity during Mg²⁺ insertion/extraction. Reflecting in MIBs, a-V₂O₅-QDs@NCNFs deliver ultra-long cycling life (5000 cycles at 5 A g⁻¹) and outstanding rate performance (52 mAh g⁻¹ at 20 A g⁻¹). This design conception opens up a new route for exploiting high-performance cathode for MIBs.