Production and applications of innovative materials with advanced electrochemical properties for energy storage

Energy conversion and storage are among the primary requirements of modern societies, in line with environmental sustainability and economic development goals. Especially electrochemical supercapacitors (ESCs) stand out among energy storage technologies due to their advantages such as high power density, fast charge/discharge characteristics, and long cycle life. Within the scope of this thesis study, the design of advanced electrode materials was targeted to overcome the problems of low specific capacitance and limited electrochemical stability encountered in supercapacitors. For this purpose, three-dimensional (3D) thiospinel metal sulfide structures were planned to be grown directly on the surface of nickel foam (NF) coated with reduced graphene hydrogel (RGH), without the use of a binder. By synthesizing the highly porous RGH structures within the macroporous matrix of NF, the electrode-electrolyte contact surface area was increased. In the second stage, high effective surface area electrodes were obtained by the direct growth of thiospinel sulfide structures composed of MCo₂S₄/A₃S₄ (M: Ni, Cu, Fe, Mn, Zn; A: Ni, Co) compounds with a core-shell morphology onto the RGH/NF surface. Furthermore, the use of Ni/Co-based layered double hydroxide (LDH) structures with a high specific surface area in the shell region aimed to improve electrolyte diffusion and electrochemical reaction kinetics, and comprehensive experimental studies were carried out in this direction. The resulting electrode structures were determined to achieve high-performance values such as a specific capacitance of ≥1500 F/g and an energy density of ≥50 Wh\ kg.