Nanotechnology in Advanced 2D and 3D Nanostructured Transition Metal Oxide Based Flexible Supercapacitors: A Review

Abstract

Flexible supercapacitors (FSCs) can be power sources for the next generation of flexible and wearable electronic devices. Recent breakthroughs in nanotechnology have opened new opportunities in the energy industry to improve the performance of FSCs by providing high energy density, high power density, and excellent flexibility. Due to their higher surface area, larger contact area between electrode and electrolyte, and shorter ion‐diffusion pathways, low‐dimensional materials with a wide variety of morphologies play a key role in improving the performance of FSCs. Especially nanostructured transition metal oxides (TMOs) are of great interest for the application of SCs due to their superior specific capacitance, high energy density, high redox reversibility, easy availability, and environmental safety. However, the low electrical conductivity, low power density, poor cycle stability, and rigid properties of TMOs have limited their wide applications for FSCs. Therefore, the fabrication of nanostructured TMO‐based composites with conducting carbon, polymers, and other materials with large surface areas, pore and layer structures, etc., improves the electrical and mechanical properties. This review provides a brief overview of the current developments in 2D and 3D TMO‐based nanomaterials and their preparation techniques, design, structure, and fundamental understanding of nanoscale capacitive behavior for advanced flexible energy storage applications.