Oligomeric Poly(Oxazoline) as Potential Lithium Battery Electrolytes

Polymer electrolytes are a promising and inherently material for next generation lithium batteries. The advancement in this field requires the use of new synthetic and fabrication techniques, as well as the investigation of new polymers. Here we report on the development of oligomeric Poly(2-ethyl-2-oxazoline) as a candidate for lithium batteries. By reducing the degree of polymerisation, the glass transition temperature was reduced from 54 °C for commercially available 50,000 Da PEtOx to 9.45 °C for lab synthesized 890 Da PEtOx. Doping with high concentrations of the lithium salts lithium nitrate, Lithium bis(trifluoromethanesulfonyl)imide and lithium perchlorate, we demonstrate a glass transition temperature maximum as the polymer electrolyte moves into the polymer-in-salt regime. In this regime we recorded a maximum conductivity of was 3.3 x 10-3 S cm-1 at 100 °C and 67 mol % LiClO4. This study demonstrates the potential for further use of alkyl oxazolines at high lithium salt concentrations and elevated temperatures.