Advances in Hybrid Supercapacitors

Hybrid supercapacitors (HSCs) are an emerging class of energy storage devices that combine the high power density of supercapacitors with the high energy density of batteries, offering a unique set of advantages that make them ideal for a wide range of applications. By pairing a faradaic electrode-where charges are stored through reversible redox, intercalation, or conversion reactions-with a non-faradaic or pseudocapacitive electrode that relies on surface ion adsorption, HSCs can provide higher energy density while still maintaining a high level of power output in short bursts, making them well-suited for applications that require rapid charging and discharging, such as in electric vehicles during acceleration, regenerative braking, or start-stop events; cordless power tools that must drive screws or drill masonry without voltage sag; grid-tied buffers that smooth short-term fluctuations from renewables; and even wearable or IoT devices that harvest intermittent energy and must transmit data bursts. This preprint features eleven research and review papers that focus on the recent advances in the field of hybrid supercapacitors, covering topics such as carbon-based and transition metal oxides electrode materials, electrolytes and additives, Zn-ion hybrid capacitors, hybrid energy storage systems, and control algorithms for supercapacitors. Research from over 40 authors from China, the United States, the United Kingdom, Romania, the Republic of Korea, Greece, and other countries and regions contributed to this preprint.