Toward commercial-level mass-loading electrodes for supercapacitors: opportunities, challenges and perspectives

Abstract

Fast charging/discharging rate and long life span render supercapacitors a potential candidate for the next generation energy supply. Nevertheless, the remaining wide gap between the basic/experimental research and practical requirements acts as the main barrier for further progress. In consequence, devising new techniques and platforms to well match the key and urgent requirements from a commercial/usable standpoint is highly desired. Specifically, although great progress has been made for the configuration of tailor-made electrode materials in terms of methodology and mechanisms, to meet the practical requirement, a bottleneck and urgent issue is to keep a decent performance when increasing the mass loading multi-times to the commercial level. Frustratingly, due to the greatly inhibited and worsened charge storage and ion migration dynamics, it is so challenging to reach this goal and it has confused researchers to a great extent up to now. In this review, we try to illustrate and clarify the involved fundamental principles for commercial-level mass-loading electrodes, including the analysis and evaluation of ion permeation/diffusion, charge transfer and redox reaction dynamics. Subsequently, we summarize and comment on the up-to-date key achievements and progress toward commercial-level mass-loading electrodes, which is divided into six branches: coupling with 3D conductive substrates, creating available pore channels, configuring hierarchical structures, aligning internal constructions by physical force/field, optimizing the properties by hetero-atoms/ions and engineering conductive MOFs. In parallel, some scientific perceptions and impressive concepts to facilitate the reaction dynamics are also highlighted. Moreover, concise outlooks/perspectives are presented here with an expectation to spark new ideas and endeavors for bringing supercapacitors into practical and daily-life applications.