Activation of Passive Nanofillers in Composite Polymer Electrolyte for Higher Performance Lithium-Ion Batteries

Poor ionic conductivity in gel or solid electrolytes hinders the electrochemical performance and hence applications of solid-state lithium-ion batteries. In this work, a simple and efficient approach to increase the ionic conductivity of gel electrolytes is reported. Composite gel polymer electrolyte (CGPE) films, consisting of poly(vinylidene fluoride-hexafluoropropylene) as the host polymer and the trilayer polypropylene membrane as the mechanical support, are prepared using charge-modified acidic TiO₂ and basic SiO₂ nanoparticles as ionic conductors. Ionic conductivities of 1.56, 1, and 1 × 10⁻² mS cm⁻¹ for acidic CGPE, basic CGPE, and CGPE without nanofillers are achieved, respectively. The Li-graphite cells employing the modified nanofillers incorporated CGPE show an enhanced electrochemical performance with the first cycle specific capacity of 412/408.5 mAh g⁻¹ for the cell with acidic CGPE and 349/347.18 mAh g⁻¹ with basic CGPE at the C/20 rate. After five cycles, each of C/8, C/4, C/2, and 1C, the acidic CGPE demonstrates a capacity retention of 78% compared to that of the basic one with 70%. This modification method has been demonstrated as a simple, facile, and scalable technique to improve electrolyte performance for solid-state lithium-ion batteries.