Fabrication of energy storage EDLC device based on CS:PEO polymer blend electrolytes with high Li+ ion transference number

Abstract

High ion transference number polymer blend electrolytes of chitosan (CS):poly (ethylene oxide) (PEO):LiClO4 systems were synthesized using solution cast technique. The XRD analysis indicated that the crystalline peaks of CS vanished in CS:PEO host blend polymer. The intensity of the hump observed in CS:PEO blend film decreased upon addition of LiClO4 salt. The FTIR study revealed the complex formation between the CS:PEO and added salt through the shifting and lessening in intensity of the FTIR bands corresponding to the functional groups. The bulk resistance estimated from the impedance plots decreased with increasing salt concentration. The maximum DC conductivity was found to be 7.34 × 10−4 S cm−1 for CS:PEO incorporated with 40 wt% of LiCLO4 salt. The electrical equivalent circuit (EEC) model has been carried out for selected samples to clarify the common picture of the electrical properties of the system. It has been verified via transference number analysis (TNM) that the transport mechanism in CS:PEO:LiClO4 electrolyte is predominantly ionic in nature with tion = 0.993 and tel = 0.007. The high ion transference number and high DC conductivity emphasized the possibility of the samples for electrochemical device application. From linear sweep voltammetry (LSV) investigation, CS:PEO:LiClO4 electrolyte was found to be electrochemically constant as the voltage sweep linearly up to 2.24 V. The CV curve covered most of the area of the current–potential plot with no redox peaks. The DC conductivity value, TNM and LSV results revealed the availability of the samples for electrical double layer capacitor (EDLC) application. The existence of charges double-layer in the fabricated EDLC was proven from cyclic voltammetry (CV). EDLC showed a consistent performance of specific capacitance (6.88 F g−1), energy density (0.94 Wh kg−1) and power density (305 W kg−1) for complete 100 cycles at a current density of 0.5 mA cm−2.