Ionic conductivity of PPO-sulfonamide salt hybrids and their network polymers

New type of polymer electrolytes containing poly(propylene oxide) (PPO)/sulfonamide (SA) lithium salt (-NLi-SO2-) unit were synthesized and the electrochemical properties were analyzed. The mono- or di-charged hybrids became amorphous salt and showed low glass transition temperature, but the bulk ionic conductivity was lower than 10−6 S/cm at room temperature. The introduction of terminal group having strong electron-withdrawing effect on the SA end improved the ionic conductivity. The maximum ionic conductivity was observed (1.7 × 10−5 S/cm at 30 °C) when the terminal group of PPO500-SA Li salt hybrid was trifluorometyl (-CF3) group. On the other hand, two types of hybrid-networks were also synthesized. They were rubbery solids with amorphous phase. The ionic conductivity was less than 10−8 S/cm because of the relatively higher Tg. The ionic conductivity of the network was improved more than 1000 times by the addition of PPO500-SALi-CF3. The Blend of the network and oligomer gave homogeneously mixed dry polymer electrolyte without phase separation. The electrochemical characteristics was analyzed with Li ∥ PPO electrolyte ∥ Li cell under dc electric field.