Surface-engineered binder-free PEDOT shielded nickel magnesium selenide nanosheet arrays electrode for ultralong-life flexible quasi-solid-state hybrid supercapacitors

Together with the development of high-performance advanced electronics, flexible supercapacitors (SCs) with tailored nanostructures have great attraction. Electrochemically deposited nanosheet arrays of nickel magnesium selenide (NixMg3-xSe4, NMgS) with high capacitance provide high potentials as a positive electrode in flexible SCs. To further enhance their electrochemical properties and long-term cycling stability, a promising strategy of surface engineering with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is proposed. The present work proposes the construction of PEDOT shielded NMgS ([email protected]) on a flexible carbon cloth substrate via a hierarchical electrodeposition technique. Benefitting from the synergistic effect, the [email protected] exhibits an excellent areal capacitance value of 1440 mF cm−2 at 4 mA cm−2. A novel shape-adaptable polymer gel electrolyte-assisted flexible quasi-solid-state hybrid SC (FQHSC) device constructed with [email protected] as a positive electrode and activated carbon as a negative electrode demonstrates the maximum power and energy density values of 14.13 mW cm−2 and 0.18 mWh cm−2, respectively, followed by outstanding cycling stability (∼100% capacitance retention over 50,000 cycles). Furthermore, the FQHSC device successfully powered electronic devices with no serious degradation upon bending and twisting for wearable electronic applications.