Regulation preferred crystal plane and oxygen vacancy of CoWO4 with morphology remolding to boost electrochemical performances for battery-supercapacitor hybrid device electrode.

Crystal plane engineering and defect engineering are feasible approaches to tune the electrochemical performance of nanocmaterials. Herein, a carambola-like CoWO 4 microsphere with preferred crystal planes and oxygen vacancies is synthesized by a microwave-assisted hydrothermal process together with post annealing treatment. The in-depth observation on microstructure and electrochemical tests suggest that it is the new preferred crystal planes and oxygen vacancies in CoWO 4 that improves conductivity and reaction activity to lead to a much higher capacity. Further density functional theory (DFT) analysis reveals that tuning the preferred crystal plane and introduction of oxygen vacancy into CoWO 4 not only effectively enhance electronic conductivity, but also promote OH− adsorption/desorption, and reduce electronic transmission barrier. As a result, the as-obtained carambola-like CoWO 4 microsphere with preferred crystal planes and oxygen vacancies delivers high specific capacity (493.7 C g−1/137.1 mA h g−1 at 1 A g−1) with superior rate capability (148.6 C g−1/41.3 mA h g−1 at 15 A g−1). Moreover, the cycling-induced morphology evolution lead to unconventional capacity increasing during cycling. The as-fabricated A-CoWO 4 //6 M KOH//activated carbon (AC) BSH device exhibits a maximum energy density of 27.5 Wh kg−1 at 1031.4 W kg−1 and 95.7% capacity retention after 12000 cycles. This work provides a possible way to improve the electrochemical performances of other metal oxide electrodes with low-capacity and irreversibility. [Display omitted] • ●CoWO 4 with preferred crystal planes and oxygen vacancies was synthesized. • ●A-CoWO 4 electrode exhibits improved conductivity and reaction activity. • ●DFT reveals the effect of preferred orientation and oxygen vacancies. • ●The morphology remolding lead to an increased cycling capacity phenomenon. • ●BSH devices deliver 27.5 Wh kg−1 energy density at a power density of 1031.4 W kg−1 [ABSTRACT FROM AUTHOR]