Fabrication of solid polymer electrolyte based on carboxymethyl cellulose complexed with lithium acetate salt as Lithium‐ion battery separator

Abstract

Polymer electrolyte is a crucial component of solid‐state‐lithium‐ion batteries that role both as separators and electrolytes. The host polymer and lithium salt selection are crucial for producing a solid polymer electrolyte with optimum characteristics. This research aims to study the effect of lithium acetate (LiCH3COO) salt on carboxymethyl cellulose (CMC)‐based solid polymer electrolytes. The LiCH3COO‐complexed CMC solid polymer electrolyte was prepared using the solution casting method with various weight percentages of LiCH3COO, that is, 0%wt, 10%wt, 20%wt, and 30%wt. The ionic conductivity analysis was conducted by using electrochemical impedance spectroscopy (EIS), infrared analysis by Fourier transform infra‐red (FTIR), mechanical analysis, crystallinity degree analysis with X‐ray diffraction (XRD), and thermogravimetry analysis (TGA), differential thermogravimetry (DTG), and differential scanning calorimetry (DSC). The interaction between Li+ ions and CMC enhanced ionic conductivity, decreased mechanical strength, reduced crystallinity degree, and lowered thermal properties. The CMC/LiCH3COO (70/30) SPE was selected as the optimum condition because it exhibited good ionic conductivity and sufficient thermal stability, while it needs a mechanical strength improvement. Molecular dynamics simulations were also performed at the density‐functional tight‐binding (DFTB) level to unravel the molecular mechanism of the Li‐ion hopping in CMC. The CMC/LiCH3COO (70/30) showed the highest electrochemical window as high as 3.5 V. Based on the results, CMC complexed with 30 (%wt) LiCH3COO salt showed high potential as a polymer electrolyte for lithium‐ion battery applications.Highlights Fabrication of solid polymer electrolyte based on carboxymethyl cellulose complexed with lithium acetate salt was conducted by simple casting solution method. The 30%wt LiCH3COO into carboxymethyl cellulose (CMC)‐polymer host showed the highest ionic conductivity of 2.47 × 10−5 S cm−1. The 30%wt LiCH3COO‐complexed CMC shows some degradation peaks, they are water evaporation, decomplexation, depolymerization, melting, and completely degraded. The density‐functional tight‐binding method suggests that the Li‐ions hop both in perpendicular and parallel directions of the cellulose layers. The CMC/LiCH3COO (70/30) showed the highest electrochemical window as high as 3.5 V.