We may be underestimating the power capabilities of lithium-ion capacitors

In this Perspective, we express our opinion on the specific power and power density of lithium-ion capacitors. These cells are state-of-the-art commercially available high voltage hybrid capacitors, notable for combining high energy and high power in one cell. However, the power characteristics of these electrochemical cells are not always well understood in the scientific community and there is a substantial amount of conflicting information in the available literature. It appears that their power characteristics are often understated, undermining the appropriate recognition of these cells. Therefore, we present the evaluation of the power capabilities of lithium-ion capacitors on the basis of key literature results and targeted laboratory measurements in our group. From our analysis, power densities superior to those in electrochemical supercapacitors are usually achievable in lithium-ion capacitors. Consequently, these cells may be recognised as superior alternatives to supercapacitors not only in terms of their energy densities but also in terms of power densities (or, in gravimetric terms, specific powers). The discussion points provided in this Perspective should stimulate better understanding of lithium-ion capacitors as innovative cells for high power applications.