Green supercapacitors: Latest developments and perspectives in the pursuit of sustainability

The slogans of modern times, “go green,” referring to the development of sustainable energy sources, have served as the main pushing force for the exploration of clean and green energy alternatives. Green energy sources are portrayed to limit the worldwide dependency on fossil fuels for energy supply, keeping in view their hazardous impact on the environment. Supercapacitors are electrochemical devices using the principle of electrochemical conversions for energy storage, providing a cleaner, greener and sustainable energy storing and delivering system. However, exploring the design aspects to develop such green energy alternatives remains essential and central. The understanding of designing aspects portrays their applicability. Apart from designing such devices, the green energy or eco-friendliness of such devices prior and after their usage cannot be neglected. The main aim behind exploration of supercapacitors is the elevation of energy density without compromising to the high power density capability. The elevation in energy density of supercapacitors can fill the void between batteries and fuel cells, thereby enabling sustainable energy storing devices. Furthermore, the elevation in specific capacitance to 1000–10000 F for supercapacitors can enhance their applicability in modern times. The enhancements in energy density and specific capacitance can play a vital role in overshadowing the limitations of batteries and fuel cells, thereby marking significance of supercapacitors among the electrochemical energy storing devices. The importance of greener and cleaner energy sources in the development of sustainable energy devices stays fundamental to this review. This review attempts to elaborate on the design aspects of green supercapacitors and the different green materials explored for supercapacitor applications in recent times to compete against the energy storing devices.