Transport parameters of charge carriers in PEO-LiTf-based, plasticized, composite, and plasticized-composite electrolytes intended for Li-ion batteries

Solid polymer electrolytes are a key component in many electrochemical devices such as dye-sensitized solar cells, batteries, and supercapacitors. In this study, three electrolytes based on polyethylene oxide (PEO) host polymer, ethylene carbonate (EC) plasticizer, and Al 2 O 3 filler were investigated. The polymer electrolytes (PEO) 9 (EC) 9 (LiCF 3 SO 3 ) 2 , (PEO) 9 (LiCF 3 SO 3 ) 2 (Al 2 O 3 ) 0.75 , and (PEO) 9 (EC) 9 (LiCF 3 SO 3 ) 2 (Al 2 O 3 ) 0.75 were characterized by analyzing DC conductivity, the frequency dependence of AC conductivity, and complex dielectric function. The conductivities of the plasticized, composite, and plasticized-composite electrolytes at 26 °C increase from 6.25, 0.009, and 2.96 mS cm -1 to 21.5, 0.12, and 11.4 mS cm -1 , respectively, when the temperature increased to 70 °C. For the in-depth analysis of electrolytes, dielectric analysis was used to determine the charge carrier density ( n ), mobility ( μ ), and diffusion coefficient ( D ) using a newly developed method. Further, the investigation extended to study the temperature dependence of n , D , and μ . The study reveals that EC can increase the ionic conductivity by increasing n , and conversely, filler contributes by increasing μ , respectively. At 26 °C, (PEO) 9 (EC) 9 (LiCF 3 SO 3 ) 2 (Al 2 O 3 ) 0.75 shows D , μ , and n of 3.8×10 -11 m 2 s -1 , 1.5×10 -9 m 2 V -1 s -1 , and 1.3×10 27 m -3 , respectively. The values obtained for D , μ , and n parameters of the plasticized electrolytes agree with those available for similar electrolytes, while the composite electrolyte showed considerably lower values for n . The complex impedance analysis can be used to determine transport parameters of all the types (plasticized, composite, and plasticized composite) of polymer electrolytes.