Lithium-Ion and Sodium-Ion Hybrid Capacitors: From Insertion-Type Materials Design to Devices Construction

There is a great appeal to develop an omnipotent player combining lithium-ion batteries (LIBs) with the capacitive storage communities. Hybrid capacitors as a kind of promising energy storage device are attracting increasing attention in the main playground in recent years. Unlike supercapacitors (SCs) and LIBs, hybrid capacitors combine a capacitive electrode with a Faradaic battery electrode. In these hybrid cells, the capacitive electrode brings the power while the energy mainly comes from the Faradaic one. Numerous efforts have been conducted in the past decades; however, the research about hybrid capacitors is still at its infancy stage, and it is not expected to replace LIBs or SCs in the near future utterly. Here, the advances of hybrid capacitors, including insertion-type materials, lithium-ion capacitors, and sodium-ion capacitors, are reviewed. This review aims to offer useful guidance for the design of faradic battery electrodes and hybrid cell construction. Brief challenges and opportunities for future research on hybrid capacitors are finally presented.