Tunable ZnO/NiO heterojunction interface for supercapacitors electrodes by piezoelectric modulation

Interface is one of the most important issues considered for highly efficient electric energy storage. Herein, the piezoelectric effect was introduced in supercapacitor for high capacitance by tuning the interfacial character at ZnO/NiO p-n junction. With strain-induced piezo-polarization charges, the capacitance was enhanced by 42.8% after applying a 0.12% compressive strain on the flexible electrodes. Such an enhanced property was elucidated by engineering the energy band profile of P-N junction interface. Specifically, electrons can be temporarily trapped and accumulated at the piezo-induced broaden depletion layer at ZnO/NiO interface in charge process until fill the potential well between ZnO and NiO, so that additional electrons can be released during discharge. These results here demonstrate that suitable interface engineering may open up new opportunities in the development of high-performance supercapacitors. •The piezoelectric effect was introduced to tuning the interfacial character for supercapacitor performance modulation.•The capacitance was enhanced by 42.8% when applying a 0.12% compressive strain on ZnO/NiO electrodes.•Electrons can be trapped by piezo-induced broaden depletion layer in charge process.