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.