Creating electronic and ionic conductivity gradients for improving energy storage performance of ruthenium oxide electrodes

Robust Ru-based thin films are successfully fabricated by single- (SA) and multiple-annealing (MA) thermal decomposition methods and are utilized as high-performance electrodes for the supercapacitors. Two critical parameters, the annealing temperature and treatment duration, are engineered for synthesizing stable thin-film electrodes. It is found that the SA thermal decomposition technique at 250 °C for 6 h results in stable RuO₂ electrodes with remarkable electrochemical performance. The MA approach consists of 2- and 3-stage thermal treatment steps. The maximal capacitance of MA-treated capacitor reaches as high as 308.8 F g⁻¹. The MA-treated electrodes deliver exceptional rate capability as well as superior cycling stability (93% capacitance retention upon 2000 cycles). The enhanced performance is attributed to the multistep thermal stages along with the layer-by-layer deposition, enabling enhanced heat transfer to individual thin layers. An optimal thermal treatment procedure is assessed empowering enhanced capacitive performance due to high hydrous RuO₂·xH₂O ratio, reduced crystalline structure, facile electrolyte wetting, and stable adhesion between the deposits and the Ti substrate. The robust design of MA-treated thin film deposits paves the way for synthesizing high-performance electrodes for the supercapacitors.