Resistivity-Temperature Behavior of Intrinsically Conducting Bis(3-methoxysalicylideniminato)nickel Polymer

Materials with a positive temperature coefficient have many applications, including overcharge and over-temperature protection in lithium-ion (Li-ion) batteries. The thermoresistive properties of an electrically conductive polymer, based on a Ni(salen)-type backbone, known as polyNiMeOSalen, were evaluated by means of in situ resistivity measurements. It was found that the polymer was conductive at temperatures below 220 degrees C; however, the polymer increased in resistivity by three orders of magnitude upon reaching 250 degrees C. Thermogravimetric results combined with elemental analyses revealed that the switch from the insulation stage to the conductive stage resulted from thermally dedoping the polymer. Electrochemical studies demonstrated that a polymer retains its electroactivity when it is heated and can be recovered to a conductive state through oxidation via electrochemical doping in an electrolyte solution.