Self-Powered Piezo-Supercapacitors Based on ZnO@Mo-Fe-MnO2 Nanoarrays

The development of self-charging supercapacitor power cells (SCSPCs) has profound implications for smart electronic devices used in different fields. Here, we epitaxially electrodeposited Mo- and Fe-codoped MnO2 films on piezoelectric ZnO nanoarrays (NAs) grown on the flexible carbon cloth (denoted ZnO@Mo-Fe-MnO2 NAs). An SCSPC device was assembled with the ZnO@Mo-Fe-MnO2 NA electrode and poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-Trfe) piezoelectric film doped with BaTiO3 (BTO) and carbon nanotubes (CNTs) (denoted PVDF-Trfe/CNTs/BTO). The SCSPC device exhibited an energy density of 30 μWh cm-2 with a high-power density of 40 mW cm-2, and delivered an excellent self-charging performance of 363 mV (10 N) driven by both the piezoelectric ZnO NAs and the PVDF-Trfe/CNTs/BTO films. More intriguingly, the device also could also be self-charged by 184 mV due to residual stress alone, and showed excellent energy conversion efficiency and low self-discharge rate. This work illustrates for the first time the self-charging mechanism involving electrolyte ion migration driven by both electrodes and films. A comprehensive analysis strongly confirmed the important contribution of the piezoelectric ZnO NAs in the self-charging process of the SCSPC device. This work provides novel directions and insights for the development of SCSPCs.