Engineering Rich-Cation Vacancies in CuCo2O4 Hollow Spheres with a Large Surface Area Derived from a Template-Free Approach for Ultrahigh Capacity and High-Energy Density Supercapacitors

Intriguing cationic defects with hollow nano-/microstructuresarea critical challenge but a potential strategy to discover electrochemicalenergy conversion and storage devices with improved electrochemicalperformances. Herein, we successfully produced a highly porous, andlarge surface area of self-templated CuCo2O4 hollow spheres (CCOHSs) with cationic defects via a solvothermalroute. We hypothesized that the inside-out Ostwald ripening mechanismof the template-free strategy was the framework for forming the CCOHSs.Cationic defects (Cu) within the CCOHSs were identified by employingvarious analytical techniques, including energy-dispersive X-ray spectroscopyanalysis of both scanning and transmission electron microscopy, X-rayphoton spectroscopy, and inductively coupled plasma-atomicemission spectroscopy. The resulting CCOHSs had significant properties,such as a high specific surface area of 98.32 m(2) g(-1), rich porosity, and battery-type electrode behaviorin supercapacitor applications. Notably, the CCOHSs demonstrated anoutstanding specific capacity of 1003.7 C g(-1) at1 A g(-1), with excellent structural integrity andcycle stability. Moreover, the fabricated asymmetric CCOHS//activatedcarbon device exhibited a high energy density of 65.2 Wh kg(-1) at a power density of 777.8 W kg(-1).

Automated summary

A highly porous and large surface area of self-templated CuCo2O4 hollow spheres with cationic defects were successfully produced via a solvothermal route. These hollow spheres exhibited high specific surface area, rich porosity, and battery-type electrode behavior, showing excellent structural integrity and cycle stability. The fabricated device using these hollow spheres demonstrated outstanding specific capacity and high energy density.