Beyond theoretical capacity in Cu-based integrated anode: Insight into the structural evolution of CuO

An excellent CuO/Cu integrated anode with CuO nanoparticle-aggregated microsheets on Cu current collector showed higher capacity beyond the theoretical capacity of CuO. The reoxidation of Cu including converted Cu nanoparticles and Cu current collector into CuO guaranteed the highly reversible conversion reaction and high capacity. The combined current ex-situ methods of XRD, SEM and TEM were used to find the origin of the additional capacity by examining the structural evolution and phase transformation of CuO/Cu integrated anode during electrochemical cycling. After 110 cycles, the discharge capacity of CuO/Cu integrated anode retained a large value of 706 mAh g^-1, which is beyond the theoretical capacity of CuO materials (674 mAh g^-1). The specific electrode configuration and the release of Cu from integrated Cu current collector made these CuO/Cu electrodes maintain high capacity and cycling stability. The present research demonstrates a protocol for the design of high-performance anode structure: in situ chemical and electrochemical activating integrated electrode system.