Charge Transport, Mechanical and Storage Performances of Sepiolite Based Composite Polymer Electrolytes

In the present report, electrochemical, thermal, mechanical and structural properties of the polymer electrolyte composed of Polyvinylidene fluoride (PVdF)-Bis(trifluoromethane)sulfonimide (LiTFSI) for various concentrations of Sepiolite was investigated. Concentration of Sepiolite was optimised based on the ambient temperature conductivity. It was observed that 10 wt.% of sepiolite incorporated composite polymer electrolyte (CPE) showed a higher ionic conductivity in the order of 3.58 x 10⁻⁴ S cm⁻¹. C−C stretching, C−F stretching and very strong -CF₂ ring breathing vibrational modes of PVdF and the complexity of the prepared composite electrolyte were studied using FTIR and X-ray diffraction analysis. The as-prepared CPE is thermally stable up to ∼335 °C; the addition of sepiolite filler into the polymer salt matrix increased the storage modulus to 40 x 10⁷ Pa from 12 x 10⁷ Pa until 90 °C. The galvanic charge-discharge performances of the CPE that exhibited high ionic conductivity were evaluated in the Li|PVdF-LiTFSI-Sepiolite|LiFePO₄ half cell configuration. The cell showed a reversible capacity of 148 mAh g⁻¹ in the second cycle; and exhibited capacity retention above 75 % even after 100 cycles. It was noted that the incorporation of eco-friendly sepiolite into the polymer electrolyte greatly enhanced the thermal, mechanical, structural and electrochemical properties of the composite electrolytes.