Designing Electroless Deposited RuO2 Thin Films for Laminated Quasi‐Solid‐State Symmetric Supercapacitor

Abstract Producing energy storage electrodes with exceptional performance using pseudocapacitive materials presents significant challenges. This study introduces a binder‐free, economical, and scalable method for the synthesis of a thin film of ruthenium oxide (RuO 2 ) suitable for symmetric supercapacitors through electroless deposition. The influence of annealing temperature (373, 473, 573, and 673 K) on electrochemical performance is investigated. The RO‐573 thin film electrode demonstrated an impressive specific capacitance of 1006 F g −1 at a scan rate of 10 mV s −1 . Additionally, a laminated quasi‐solid‐state symmetric device has been developed, showcasing a remarkable specific capacitance of 198 F g −1 , ultrahigh energy density of 59.01 Wh kg −1 , and a power density of 2.4 kW kg −1 . The laminated, symmetric, quasi‐solid‐state supercapacitor device demonstrates impressive stability over 10,000 cycles, achieving a retention rate of 92%. The characteristics and design of laminated quasi‐solid‐state symmetric supercapacitors render them highly appropriate for real‐time applications in advanced energy storage systems.