Influence of N-doped TiO ₂ on lithium ion conductivity of porous polymeric electrolyte membrane containing LiClO ₄

Polymer electrolyte composites (PECs) based on poly(vinylidenefluoride-co- hexafluoropropylene) (PVDF-HFP) that contained lithium perchlorate (LiClO ₄) were prepared. N-doped TiO ₂ (N-Ti) was used as a filler to enhance the Li ⁺ ion conductivity. Structural modification and electrochemical properties of the PECs were investigated in order to understand the effect of N-Ti in the polymer matrix on ionic conductivity. The PECs prepared with different N-Ti contents were characterized by SEM, mapping, DSC, and a.c. impedance. From the results, the prepared N-Ti-filled PECs showed a good ability to absorb and retain the Li ⁺ ion. The presence of N-Ti in PVDF-HFP was resulted in increasing the ion conductivity significantly. The highest ion conductivity (6.7 × 10 ^{- 4} S/cm) was observed at a relative low N-Ti content (2.5 wt.%). It is believed that the addition of N-Ti could provide the foundation for the ionic transportation and ion-mobility of the PECs and the N-doping on TiO ₂ led to a more enhanced ionic conductivity by higher interaction between polar groups, such as O and N of N-Ti and Li ⁺ ions.