Stress-Engineered Nickel Current Collectors as Active Components for High-Performance Supercapacitors

Abstract

Metallic current collectors are widely used in electrochemical energy-storage devices, yet their contribution to electrode performance is often overlooked. In particular, the effects of current-collector microstructure and mechanical state on the electrochemical behavior of supported active materials remain poorly understood. Here we show that controlled annealing of nickel (Ni) current collectors can modify the electrochemical response of graphene oxide electrodes without changing the active material. Ni plates were stress-relief annealed below the recrystallization temperature at 120, 220 and 320 °C. The treated substrates were characterized using surface profilometry, scanning electron microscopy, electron backscatter diffraction and nanoindentation. Annealing altered the surface morphology, grain structure, crystallographic characteristics and mechanical properties of the Ni substrate. The electrochemical behavior of spent pot lining-derived graphene oxide (SPL-GO)/Ni electrodes in 3 M KOH was evaluated using cyclic voltammetry, galvanostatic charge−discharge and electrochemical impedance spectroscopy. These measurements revealed distinct charge-storage and interfacial characteristics among the annealed substrates. Among the investigated conditions, annealing at 220 °C produced the most favorable combination of surface morphology, microstructure and mechanical properties. The resulting SPL-GO/Ni electrode exhibited a specific capacitance of 414.14 F/g and a specific energy of 57.98 Wh/kg at 2 A/g. The electrode retained 96.08% of its initial capacitance after 2500 cycles. Electrochemical analysis revealed predominantly electric double-layer charge storage with contributions from diffusion-controlled processes. These findings demonstrate that the microstructural and mechanical state of a metallic current collector can modulate the electrochemical behaviour of the electrode. Therefore, substrate engineering advances an independent approach to tuning interfacial charge storage and electrode performance without altering the active-material chemistry.