Core–Shell Ni/Ni(OH)₂ Nanowire Array for Asymmetric Supercapacitors

In this study, we present a systematic investigation of the electrochemical performance of a core–shell Ni/Ni(OH) 2 nanowire array in an asymmetric supercapacitor configuration with graphene flakes. We synthesized the nanowires, with diameters of 35, 100, and 150 nm, through electrodeposition, which enabled us to precisely control their dimensions. We discovered a remarkable trend: the supercapacitor performance initially increases with nanowire height but then gradually decreases after reaching a critical point. To further explain and understand this phenomenon, we employed finite element analysis (FEA), which confirmed our experimental results and revealed the underlying electrochemical mechanisms. The FEA simulations showed that the nanowire length affects the distribution and accessibility of ionic species surrounding the nanowire array, which in turn influences the charge storage and transfer processes. Our findings demonstrate the crucial role of nanowire geometry in electrochemical behavior and provide valuable insights into designing nanowire architectures for optimal supercapacitor performance.