Chemical Solution–Based Deposition Techniques for Asymmetric Supercapacitors: Progress in Electrode Materials for High-Efficiency Energy Storage

The fast growth of portable electronics, clean energy technologies, and electric cars intensifies the need for energy-efficient storage devices. Asymmetric supercapacitors (ASCs) are a potentially helpful innovation, offering a distinct merit by combining two dissimilar electrodes. Despite having high power densities, their widespread use is limited by their inferior energy densities compared to batteries. For ASCs to be commercially viable, two conditions must be met: They must supply high energy densities and be affordable. Therefore, this work examines the latest advancements in fabricating ASC electrode materials via low-cost chemical solution–based deposition techniques for high-energy-density applications. By adjusting several parameters, including solution concentration, temperature, and conductive substrate selection, these techniques enable the nanoscale enhancement of electrode material properties. This study emphasizes on the synthesis, structural design, and electrochemical capabilities of common ASC electrode materials. This includes conducting polymers, transition metal oxides, and carbon-based nanocomposites. Likewise, the potential of emerging materials, such as layered double hydroxides and 2D transition metal dichalcogenides, is discussed. Furthermore, ASCs are appropriately categorized into subgroups with their respective electrode arrangement. Lastly, performance evaluation tests and future perspectives to address the current challenges in this field are presented to pave the way for the construction of ASCs with enhanced efficiency and longevity.