Abstract
Aqueous metal-selenium batteries based on chalcogenide cathodes, despite their multi-electron conversion-type redox reactions and rapid kinetics, suffer from short lifespans and unclear capacity degradation mechanisms. The interfacial interactions between doped carbon and chalcogenides correlate closely with the electrochemical structural evolution. Hence, flower-like Cu(2-x)Se wrapped with ultrathin N-doped carbon layer (Cu(2-x)Se@N-C) is synthesized via a simple γ radiation-pyrolysis route for the first time. The Cu(2-x)Se@N-C cathode displays a high-rate performance and long-term stability, with a respective capacity of 310.6 mAh g(-1) at 20 A g(-1) and a capacity retention rate of 92.9% after 30 000 cycles over 2000 h at 5 A g(-1). Ex situ X-ray diffraction and X-ray photoelectron spectroscopy confirm the reversible Cu storage mechanism of the Cu(2-x)Se@N-C cathode and the issues of volume expansion and oxidative dissolution related to the capacity degradation of the Cu(2-x)Se cathode. Furthermore, X-ray absorption analysis and theoretical calculations reveal the presence of Se─C interactions between the ultrathin N-doped carbon and Cu(2-x)Se. As a result, the physical and chemical dual-protection of N-doped carbon via Se-C not only effectively stabilizes the structural evolution of Cu(2-x)Se but also endows it with faster electrode reaction kinetics.