Dielectric Modified Separators for High-Voltage and High-Rate Supercapacitors

Widening the operational voltage window (OVW) of electrolytes has long been attracting researchers' attention as an effective solution for improving the energy density of supercapacitors (SCs). However, the application of commercial cellulose separators in SCs under high voltage is impeded because of the hygroscopic property of hydroxyl functional groups and high self-discharges. Herein, the dielectric materials poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP and TiO2 are employed to modify the surfaces of cellulose separators, which has improved the rate (100% capacitance retention at 20 A g(-1)) and cyclic (over 83% capacitance retention after 10000 cycles) performance of SCs significantly. In addition, the OVW of the organic electrolyte is widened from 2.7 V to 3.8 V. The possible mechanism underlying the function of dielectric materials in SCs is discussed by establishing a model and performing inferential calculation. (C) 2022 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.

Automated summary

In this study, PVDF-HFP and TiO2 modified cellulose separators significantly improved the performance of SCs, including 100% capacitance retention rate and 83% capacitance retention rate after cycles. The widening of the OVW of the organic electrolyte further enhanced the performance of SCs.