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). A self-charging supercapacitor power cell device was assembled with the Mo- and Fe-codoped MnO₂ nanoarray electrode and poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-Trfe) piezoelectric film doped with BaTiO₃ (BTO) and carbon nanotubes (CNTs) (denoted PVDF-Trfe/CNTs/BTO). The self-charging supercapacitor power cell 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 nanoarrays and the poly(vinylidenefluoride-co-trifluoroethylene) piezoelectric film doped with BaTiO₃ and carbon nanotubes. More intriguingly, the device 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 nanoarrays in the self-charging process of the self-charging supercapacitor power cell device. This work provides novel directions and insights for the development of self-charging supercapacitor power cells.