Infilling of highly ion-conducting gel polymer electrolytes into electrodes with high mass loading for high-performance energy storage

Full utilization of electrodes toward high-performance energy storage is challenging in cases where electrode/electrolyte interface is significant. From a practical perspective, this is particularly important in cases where a thick electrode or one with a high mass loading is needed. Here, we report an approach to increase the electrode performance by the infilling of a highly ion-conductive organic gel polymer electrolyte (EI-GPE, ionic conductivity ∼9.2 mS cm⁻¹) into a multi-walled carbon nanotube (MWCNT) electrode with high mass loadings of up to 26 mg cm⁻² (or significant thicknesses of up to 443 μm). Typical GPE (t-GPE) with a film-forming property but moderate ionic conductivity (1.2 mS cm⁻¹) is then placed over the EI-GPE-filled electrode surface, resulted in flexible supercapacitor. Infilling of EI-GPE into MWCNT electrode provides a large-ion accessible interface that affords the increase in volumetric capacitance and energy density, about sixfold greater than that of the typical supercapacitors configured by sandwiching t-GPE as both electrolyte and the separator between a pair of electrodes. Importantly, this method enables scaling of the areal capacitance with electrode thickness (or mass loading of active material). A pouch type EI-SC provides stable performance after bending, suggesting it holds the promise of flexible energy storage.