Exploring the potential of transition-metal-based hollow micro- and nanoparticles in supercapacitor electrodes

The development of high-performance supercapacitors for energy storage applications is important in the era of renewable energy. This review article comprehensively analyzes the electrochemical performance of transition metal-based hollow micro- and nanoparticles, including transition metal oxides (TMOs), transition metal sulfides (TMSs), transition metal phosphides/phosphates (TMPs), and transition metal selenides (TMSes). The study focuses on specific capacitance, energy density, power density, and cycling stability. In addition, this study investigates the impact of various properties of micro- and nanoparticles on the electrochemical performance of supercapacitors. These properties include morphology, shell thickness, pore size, porosity, crystallinity, metallic and non-metallic element ratio, and incorporation of conductive materials such as carbon or conductive polymer into their structures. The analysis finds that TMPs exhibit the highest specific capacitance due to their high theoretical capacitance. Furthermore, the review also highlights the significance of employing transition metalbased materials as both anode and cathode to achieve a high energy density. The highest energy density was observed in the TMSe-based supercapacitor constructed from pseudocapacitive cathode and anode. The study provides valuable insights into the current research landscape of transition metal-based hollow micro- and nanoparticles and sheds light on areas that may require further investigation. Ultimately, this review contributes to the development of high-performance supercapacitors and could aid in realizing their full potential in energy storage applications.