Tuning the conductivity and flexibility of functionalized cellulose/PVA binary blend doped with lithium perchlorate and glycerol: A new paradigm towards solid polymer electrolytes

Solid polymer electrolytes (SPEs) play a critical role in the advancement of solid-state lithium-ion batteries (SSLiBs), offering improved battery safety, enhanced thermal stability, and increased energy density while mitigating the risks of electrolyte leakage and degradation commonly associated with liquid-based batteries. This work focuses on tuning the ionic conductivity and mechanical flexibility of functionalized cellulose/poly (vinyl alcohol) (PVA) binary blend doped with lithium perchlorate (LiClO4) and glycerol. The SPE membranes are fabricated using the casting solution technique, incorporating various weight percentages of carboxymethyl cellulose (CMC), PVA, LiClO4, and glycerol. Their electrochemical properties are evaluated through electrochemical impedance spectroscopy (EIS), while their physicochemical characteristics, including complexation mechanisms, are assessed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) Spectroscopy, tensile testing, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Notably, the incorporation of 25 wt% glycerol CMC/PVA + 20 wt% LiClO4, labeled as SPE-Li20-Gly25, results in the highest recorded ionic conductivity of 2.70 × 10−3 S. cm−1, along with a lithium-ion transference number of 0.89 and an electrochemical window of 2.22 V. Additionally, this SPE membrane also demonstrates good flexibility, with a tensile strength of 0.84 MPa and an elongation at break (EAB) of 392.73 %, alongside a crystallinity index (CrI) of 23.41 %, thermal decomposition of 266 °C. A decreased peak ratio (XPS) of free Li+ to Li+- O from 0.78 to 0.22, indicates a stronger interaction between Li+ and the polymer framework, facilitated by glycerol. Eventually, the development of a highly conductive and flexible CMC/PVA binary blend-based polymer electrolyte introduces a new paradigm, highlighting its potential as a promising candidate for next-generation SSLiBs.