In situ prepared nano-crystalline TiO2–poly(methyl methacrylate) hybrid enhanced composite polymer electrolyte for Li-ion batteries

Abstract

Nano-sized ceramic fillers provide a promising approach to enhancing polymer electrolytes in terms of the interfacial chemistry, ionic conductivity, and C-rate performance of Li-ion cells, if their dispersibility and compatibility in a polymer matrix can be well managed. In this work, a nano-crystalline TiO₂–PMMA hybrid is prepared by in situ crystallization, and its structure and properties are characterized by XRD, FTIR, TG and HRTEM. The enhancements provided by the nano-crystalline TiO₂–PMMA hybrid as an additive in a PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) based composite polymer electrolyte, including in the pore distribution, electrolyte uptake, ionic conductivity, and electrochemical properties, are confirmed by SEM, linear sweep voltammetry (LSV), charge–discharge cycle testing and AC impedance measurements. The results obtained in this work show that, after the process of annealing, the nano-crystalline TiO₂–PMMA hybrid can retain a good dispersibility in PVDF-HFP. Moreover, the nanohybrid doped PVDF-HFP CPE exhibits improved pore distribution, electrolyte uptake and ionic conductivity. Even more importantly, LiCoO₂/Li cells with doped CPE exhibit good C-rate performances, which is confirmed by AC impedance results, which show a remarkable enhancement in the interfacial compatibility between the doped CPE and the electrode.