The key difference between the two is that batteries have a higher density (storing more energy per mass) whilst capacitors have a higher power density (releasing and store energy more quickly). Supercapacitors have the highest available capacitance values per volume and greatest energy density of all capacitors.
Unlike batteries, which store energy through chemical reactions, supercapacitors store energy electrostatically, enabling rapid charge/discharge cycles. In certain applications, this gives them a significant advantage in terms of power density, lifespan, efficiency, operating temperature range and sustainability.
Both supercapacitors and batteries can be integrated to form an energy storage system (ESS) that maximizes the utility of both power and energy. The key objective here is to amplify their respective strengths while minimizing their shortcomings.
While batteries can store energy for a long period, they take a long time to charge and discharge electricity. This is where capacitors come in — they store electricity in an electric field that can be quickly charged and discharged for rapid access to power as needed.
Among different technologies, conventional capacitors possess the lowest energy storage capacity but can deliver their charge extremely rapidly resulting in the highest power density. Fuel cells offer increased energy densities but involve complex chemical reactions for energy release.
Supercapacitors, bridging conventional capacitors and batteries, promise efficient energy storage. Yet, challenges hamper widespread adoption. This review assesses energy density limits, costs, materials, and scalability barriers.