Ionic Conductivity Enhancement of Polyethylene Oxide-LiClO4 Electrolyte by Adding Functionalized Multi-Walled Carbon Nanotubes

Polymer electrolytes are needed in many solid-state electronic and energy devices. But polymer electrolytes usually have a low ionic conductivity. This work reports the enhancement in the ionic conductivity of polyethylene oxide (PEO)-LiClO4 electrolyte by adding functionalized multiwalled carbon nanotubes (MWCNTs). MWCNTs are functionalized with carboxylic groups through oxidation with acids. They can be dispersed in acetonitrile solutions of PEO and LiClO4. The presence of functionalized MWCNTs can effectively enhance the ionic conductivity of the PEO-LiClO4 electrolyte, and the ionic conductivity enhancement depends on the loading of the functionalized MWCNTs. Enhancement by a factor of 3.3 was observed. The enhancement in the ionic conductivity is attributed to the functionalized MWCNT-induced decrease in the crystallinity of PEO and increase in the salt dissociation due to the Lewis acid-base interaction of the functionalized MWCNTs with PEO and LiClO4. The addition of functionalized MWCNTs can also effectively improve the mechanical properties of PEO films.