In-situ growth of binder-free Cr/NiO thin film electrodes via co-sputtering for asymmetric supercapacitors

Recently, metal oxides (MOs) have received tremendous interest for flexible energy storage systems: in partic-ular, supercapacitors (SCs). SC electrodes are commonly fabricated via the coating of MOs particles, conductive carbon and binders. However, such electrodes, can weaken the performance of SCs. In this work, binder-free nanocluster Cr-doped NiO thin films are grown on flexible stainless-steel (SS) foils using a one-step co-sputter-ing technique. The distinctive nanocluster structure of Cr-incorporated NiO thin film electrodes (TFEs) has the benefit of reduced ion diffusion length and good charge transport, and can increase the accessibility of ions onto the active surface area. The developed TFEs are examined in 2 M KOH aqueous electrolyte, demonstrating highest areal capacitance of 429 mF cm-2 (251 mC cm-2). Subsequently, an asymmetric coin cell (ACC) SC is assembled. Even after 5,000 cycles, the developed ACC SC demonstrates exceptional cycling stability. Thereafter, the aging test is conducted after 720 h and reveals good electrochemical performance with minimal capacitance fading. Results reveal that Cr-doped NiO TFEs show excellent electrochemical performance with higher areal capacitance and stability compared to NiO and other metal oxide-based TFEs reported previously. The grown Cr-doped NiO binder-free TFEs are good candidates for high-performance and flexible energy storage systems.

Automated summary

In this study, binder-free nanocluster Cr-doped NiO thin film electrodes were developed on flexible stainless-steel foils using a one-step co-sputtering technique. The unique nanocluster structure of the electrodes resulted in reduced ion diffusion length, improved charge transport, and increased accessibility of ions onto the active surface area. The electrodes exhibited a high areal capacitance of 429 mF cm-2 (251 mC cm-2) in a 2 M KOH aqueous electrolyte. The developed asymmetric coin cell supercapacitors demonstrated exceptional cycling stability even after 5,000 cycles and good electrochemical performance with minimal capacitance fading after 720 hours of aging test.