Advances in the charging mechanisms for supercapacitor by <italic>in situ</italic> characterization methods

Supercapacitor is a kind of storage devices that store charge through the electrosorption of ion and fast and reversible faradaic reactions (redox reactions) on the surface of porous electrodes.Recently supercapacitors have boosted its electrochemical properties by tailored porous electrode materials at nanoscale level.Understanding and controlling the storage mechanisms of supercapacitors may hold the key to improving the electrochemical properties of supercapacitor.This article summarizes the advances on charging mechanisms of supercapacitors using various in-situ experimental techniques, including in-situ NMR spectroscopy, electrochemical quartz crystal microbalance (EQCM), in-situ infrared (IR) spectroscopy and in-situ scattering approaches.Finally, future research directions in advanced characterization techniques for supercapacitor are briefly discussed.