Hybrid Nano-Phase Ion/Electron Dual Pathways of Nickel/Cobalt-Boride Cathodes Boosting Intercalation Kinetics for...

Nickel-based hydroxides and their derivatives exhibit relatively low capacities and unsatisfactory durability as cathode materials for rechargeable alkaline batteries. In this work, a hybrid NiCo-B nanosheet cathode, integrating electrolyte ion-shuttling channels and electron-transferring networks into a metal-organic framework (MOF), was devised delicately. In the structure, the hybrid ion/electron dual pathways were constructed by NiCo-MOF frameworks and NiCo-B interpenetration networks. It revealed that nano-phase electron-transferring pathways in the MOF obviously boosted ion intercalation kinetics. The as-obtained hybrid NiCo-B nanosheets as cathode materials exhibited reversible capacity as high as 280 mA h g^-1 at a current density of 1 A g^-1 and excellent rate capability with a capacity retention of 78% from 1 to 10 A g^-1. After 2000 charge/discharge cycles at 4 A g^-1, the capacity still remained at 94% of the initial one. A full battery assembled with a hybrid NiCo-B cathode and a Fe₂O₃ anode showed a high capacity of 250 mA h g^-1 and a considerable stability of 89% after 1000 cycles. Ragone plots indicated the highest energy density of 409 W h kg^-1 and the lowest power density of 1.5 kW kg^-1, outperforming other aqueous batteries. It revealed that a syngenetic structure of ion/electron hybrid dual pathways integrated into an MOF could be a potential strategy to optimize ion intercalation electrode materials for alkaline batteries.