Anode Material Research Trends: From Lithium-Ion to Next-Generation Potassium-Ion Hybrid Supercapacitors

The growing interest in and demand for energy storage devices have spurred extensive research on systems such as supercapacitors (SCs) and batteries, as well as the development of advanced electrode materials. Among these, hybrid supercapacitors (HSCs) have garnered attention due to their ability to combine the high-power density and long cycle life of SCs with the high energy density of batteries. Notably, lithium-ion hybrid supercapacitors (Li-HSCs), which integrate the properties of lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), have emerged as high-performance energy storage devices. However, the rising costs and limited availability of lithium have shifted the focus toward next-generation energy storage systems. In this context, potassium-ion hybrid supercapacitors (K-HSCs) are gaining recognition as promising alternatives to Li-HSCs. This review provides an in-depth analysis of research trends, from the anode materials utilized in Li-HSCs to the recently developed anode materials for K-HSCs. Furthermore, it highlights the challenges and future directions for advancing next-generation HSC technologies.