A New TiO-Based Cathode Material with Interface-Dominated Storage Mechanism for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are highly desirable for large-scale energy storage applications, yet the lack of suitable cathode materials hinders their deployment. Here, for the first time, a new and promising TiO-based cathode material (TOC-AI) is reported for AZIBs and unveil a novel energy storage mechanism that enables Zn storage predominantly originating from the interface. The TOC-AI composed of ultrafine TiO nanocrystals embedded within an amorphous carbon matrix, featuring abundant atomic interfaces and strong interactions, triggers a decoupled and rapid transport of Zn ions and electrons in the interfacial space charge region, similar to an electrostatic capacitor. Moreover, the presence of titanium vacancies facilitates Zn intercalation into the TiO bulks, contributing extra capacity to the composite. Finally, a high capacity of 111 mAh g and excellent cycling performance with 77% capacity retention after 17 000 cycles are achieved. Such interface-dominated storage mechanism has also been successfully extended to other composite systems, broadening the scope of potential applications for materials traditionally deemed inactive for Zn storage.