Nanochannels regulating ionic transport for boosting electrochemical energy storage and conversion: a review

Electrochemical power sources, as one of the most promising energy storage and conversion technologies, provide great opportunities for developing high energy density electrochemical devices and portable electronics. However, uncontrolled ionic transport in electrochemical energy conversion, typically undesired anion transfer, usually causes some issues degrading the performance of energy storage devices. Nanochannels offer an effective strategy to solve the ionic transport problems for boosting electrochemical energy storage and conversion. In this review, the advantages of nanochannels for electrochemical energy storage and conversion and the construction principle of nanochannels are introduced, including ion selectivity and ultrafast ion transmission of nanochannels, which are considered as two critical factors to achieve highly efficient energy conversion. Recent advances in applications of nanochannels in lithium secondary batteries (LSBs), electrokinetic energy conversion systems and concentration cells are summarized in detail. Nanochannels exist in the above systems in two typical forms: functional separator and electrode protective layer. Current research on nanochannel-based LSBs is still at the early stage, and deeper and broader applications are expected in the future. Finally, the remaining challenges of nanochannel fabrication, performance improvement, and intelligent construction are presented. It is envisioned that this paper will provide new insights for developing high-performance and versatile energy storage electronics based on nanochannels.