As a representative electrochemical energy storage device, supercapacitors (SCs) feature higher energy density than traditional capacitors and better power density and cycle life compared to lithium-ion batteries, which explains why they are extensively applied in the field of energy storage. While the available reviews are mainly concerned with component materials, state estimation, and industrial applications, there is a shortage of understanding of thermal behaviors and thermal management systems of SCs, which makes this review a timely aide for fulfilling this gap. This review introduces the energy storage mechanisms of SCs, followed by descriptions of current investigations of thermal behaviors. This covers the aspects of heat generation rates for electric double-layer capacitors (EDLCs) and hybrid supercapacitors (HSCs), together with reviewing existing experimental methods to measure and estimate heat generation rates, as well as comparative assessments of multiple heat generation rate models and research on thermal runaway. In addition, there are also overviews of current efforts by researchers in air cooling systems, liquid cooling systems, phase change material cooling systems, and heat pipe cooling systems. Finally, an in-depth discussion is provided regarding the challenges and future work directions for SCs in thermal behaviors and thermal management systems.

The lithium-ion battery (LIB) has become the most widely used electrochemical energy storage device due to the advantage of high energy density. However, because of the low rate of Faradaic process to transfer lithium ions (Li⁺), the LIB has the defects of poor power performance and cycle performance, which can be improved by adding capacitor material to the cathode, and the resulting hybrid device is also known as a lithium-ion battery capacitor (LIBC). This review introduces the typical structure and working principle of an LIBC, and it summarizes the recent research developments in advanced LIBCs. An overview of non-lithiated and pre-lithiated anode materials for LIBCs applications is given, and the commonly used pre-lithiation methods for the anodes of LIBCs are present. Capacitor materials added to the cathodes, and suitable separator materials of LIBCs are also reviewed. In addition, the polarization phenomenon, pulsed performance and safety issues of LIBCs and electrode engineering for improving electrochemical performance are systematically analyzed. Finally, the future research and development direction of advanced LIBCs is prospected through the discussion of the existing problems of an LIBC in which the battery material in the composite cathode is LiNi_xCo_yMn_1−x−yO₂ (NCM).