Advancements in asymmetric supercapacitors: Material selection, mechanisms, and breakthroughs with metallic oxides, sulfides, and phosphates

The growing demand for electricity in transportation, optoelectronics, and portable electronics requires green and reliable power sources with high energy, power, and durability. Over the past decade supercapattery, a generic term for hybrid supercapacitors gained immense attention in the scientific communities and widespread applications. This article addresses the confusions and differences among capacitive, Faradaic, and pseudocapacitive charge storage mechanisms. There are some pros and cons associated with selection of electrode materials so, materials engineering and device engineering along with challenges are briefly discussed. Herein, we endeavor to assess the multiple synthesis techniques and their profound impacts on electrochemical performance. Systematical survey on properties of active materials like surface area, porosity, economic viability, interlayer spacing, robustness, and cyclic stability are covered. Ideal candidates for discussion here are metallic sulfides, oxides, and phosphates with their binary and ternary composites. Finally, some challenges and future recommendations are summarized.