A New TiO₂-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 TiO₂-based cathode material (TOC-AI) is reported for AZIBs and unveil a novel energy storage mechanism that enables Zn²⁺ storage predominantly originating from the interface. The TOC-AI composed of ultrafine TiO₂ nanocrystals embedded within an amorphous carbon matrix, featuring abundant atomic interfaces and strong interactions, triggers a decoupled and rapid transport of Zn²⁺ ions and electrons in the interfacial space charge region, similar to an electrostatic capacitor. Moreover, the presence of titanium vacancies facilitates Zn²⁺ intercalation into the TiO₂ bulks, contributing extra capacity to the composite. Finally, a high capacity of 111 mAh g^-1 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 Zn²⁺ storage.