Space-charge limited ionic conductivity enhancement in gel polymer electrolyte capacitors by embedding nanoparticles

Abstract

In this work, a novel mixture of ionic liquid gel polymer electrolyte (ILGPE), containing 1-butyl-3-methylimidazolium bromide, ammonium acetate and poly(vinyl alcohol), with Si@C and SiO2 embedded nanoparticles is fabricated. The resulting CILGPE is deposited onto interdigitated electrodes. The fabricated electrolytes have been characterised by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the resulting capacitors have been characterised by impedance spectroscopy (IS) and linear sweep voltammetry (LSV) and modelled. The specific capacitance for capacitor with ILGPE is 0.042Fcm−3, while for the capacitor with SiO2 and Si@C embedded in ILGPE are 0.072 Fcm−3 and 0.06 Fcm−3, respectively. Therefore, the addition of SiO2 and Si@C nanoparticles improves the capacitance by 71% and 42%, respectively. The results of fitting I-V curves exhibit reductions in both the activation voltage (Vtr) and in the voltage that indicates the traps are filled (VTFL) with the addition of nanoparticles, revealing an increase in charge contribution. We propose that the capacitance enhancement is due to the contribution of nanoparticles to: (i) the creation new effective ion transport pathways, (ii) ion dissociation in the electrolyte and (iii) the crystallinity reduction of ILGPE. This work contributes with new findings about the effect of nanoparticles on the Space-charge-limited-conduction (SCLC) mechanism and how these changes in transport mechanism are related to the series and leakage resistances, capacitance, and physicochemical properties.