Vacancies Revitalized Ni₃ZnC_0.7 Bimetallic Carbide Hybrid Electrodes with Multiplied Charge-Storage Capability for High-Capacity and Stable-Cyclability Lithium-Ion Storage

Transition metal carbides (TMCs) exhibit good electron conductivity and structural stability; however, the limited active sites hindered the application in lithium-ion batteries. Unlike many alloying or conversion-reaction-type active materials, most of them store charges by capacitive processes. Moreover, the Li-ion storage mechanism for the bimetallic counterparts has been substantiated mainly through an adsorption or intercalation Faradaic pseudocapacitance effect. Taking vacancy-enriched Ni3ZnC0.7 nanohybrids as example, we demonstrated for the first time the occurrence of local phase segregation and abnormally efficient Li-ion storage from in situ formed active nanocrystals in organo-functionalized ultrasmall Ni3ZnC0.7 (∼3–5 nm) hybrid electrodes. Those hybrid electrodes not only delivered high reversible Li-ion storage capability of 1100 mAh g–1 at 50 mA g–1 but also exhibited an excellent rate performance of 10 A g–1 with fully reversible capacity recovery and ultralong cycling stability (nearly no capacity decay) at different rates (e.g., 0.1 A g–1 for 300 cycles, 0.2 A g–1 for more than 500 cycles, and 1 A g–1 for 1000 cycles with nearly 100% capacity retention). Physicochemical characterization of the postcycled electrodes revealed highly active Zn and Ni nanocrystals newly generated around the parent vacancy-enriched Ni3ZnC0.7 nanocrystals, which enriched the active sites for Li-ion storage and simultaneously elevated the capacitive and diffusion-controlled charge-storage capability, probably accounting for the enhanced electrochemical performance, besides the highly electron-/ion-conductive porous carbon matrix and TMCs themselves.