A.C impedance, XRD, DSC, FTIR studies on PbTiO3 dispersoid pristine PVdF-co-HFP and PEMA blended PVdF-co-HFP microcomposite electrolytes

• Ionic mobility enhancement due to space charge effect
• Lead titanate spontaneous polarization blocking active dipoles C–F
• Lesser mass fraction (2.5 wt.%) of PbTiO3 for better thermal stability
• PEMA interaction through ester carbonyl side chain

A.C impedance, XRD and thermal and FTIR studies were carried out for pristine PVdF-co-HFP(30 wt.%)/PbTiO3(5 wt.%) polymer microcomposite electrolyte membranes (PMCEs) by varying three EC:DMC–LiBETI compositions (62.5:2.5 (NP2), 60.0:5.0 (NP3) and 57.5:7.5 (NP4) wt.%). The higher conductivity was noted 7.99 × 10− 5 S cm− 1 for NP4 and this account for better mobility of Li+ free cations. The studies were repeated by blending PEMA with PVdF-co-HFP in three blend ratios i.e., 7.5:22.5 (NP6) wt.% (1:3), 15:15 (NP7) wt.% (1:1) and 22.5:7.5 (NP8) wt.% (3:1) for the same EC/DMC–LiBETI compositions. While blending, the conductivity was decreased in general, and among the blend ratio, higher conductivity noted 4.60 × 10− 5 S cm− 1 for 3:1 (NP8) however it was lower than the pristine NP4. The temperature dependence of PMCE pristine and blended systems obeys Arrhenius behavior. The XRD diffractogram registers the dominance of lead titanate in pristine and blended systems albeit intensity variations. In DSC studies, variation of ΔHm and Tm was noted due to PEMA, and hindrance of VdF crystallites was observed within its melting endotherm Tm range due to fixed dispersoid PbTiO3 which suggests that 3:1 ratio with 2.5 wt.% LiBETI with 5 wt.% PbTiO3 showed better thermal stability. DSC studies had not registered the effect of PEMA in the thermal scale scanned than pristine PMCEs. FTIR investigation confirms molecular interactions in the vibrational range 400–2000 cm− 1 w.r.t. CO, C–F and C–H stretchings.