Enhanced ionic conductivity and dielectric performance of CaB2O4-doped 2-hydroxyethyl cellulose polymer electrolytes for electrical double layer capacitor applications

Document Type

Article

Publication Date

3-1-2026

Abstract

In this study, the effects of calcium metaborate (CaB₂O₄) doping on the 2-hydroxyethyl cellulose (2-HEC)-based polymer electrolytes (PEs), which were synthesised using the solution casting method, were investigated. The electrolyte containing 27.27 wt% CaB₂O₄ achieved the highest ionic conductivity of 1.7 × 10−6 S cm−1, attributed to enhanced amorphous regions promoting ion mobility. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses confirmed reduced crystallinity and increased polymer chain mobility, and formed additional ion-conductive pathways upon CaB₂O₄ incorporation. Dielectric analysis showed increases in ε' and ε'′ values up to 27.27 wt% CaB₂O₄, indicating adequate charge storage and interfacial polarisation. Galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) tests confirmed the electric double-layer capacitor (EDLC) behaviour, with stable specific capacitance across extended voltage windows. The enhanced samples exhibited high ionic transference numbers and expanded electrochemical stability windows (ESW) in linear sweep voltammetry (LSV), reaching approximately 5.15 V. Notably, reducing the discharge current from 2 mA g−1 to 0.25 mA g−1, resulted in a substantial increase in specific capacitance, rising from 1.51 to 16 F g−1 (in the 0–1 V window) and from 1.79 to 18.2 F g−1 (in the 0–1.5 V window), which was attributed to improved ion accessibility and more efficient double-layer formation. These findings suggested that the 2-HEC/ CaB₂O₄ PEs were suitable for use in flexible and efficient energy storage devices, particularly in calcium-ion batteries and electrochemical capacitors.

Keywords

2-hydroxyethyl cellulose, Calcium metaborate, Polymer electrolyte, Ionic conductivity, EDLC, Electrochemical stability

Publication Title

Solid State Ionics

ISSN

0167-2738

DOI

10.1016/j.ssi.2026.117125

Volume

436

First Page

117125

Publisher

Elsevier

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