Lithium-Ion Conducting Molecular Composites Prepared by Yamamoto Polymerization

A3. Organic and Inorganic Ion Conducting Materials
Hannes Nederstedt1 , Patric Jannasch1
1 Lund University, Department of Chemistry, Centre for Analysis and Synthesis
Introduction/Purpose: Solid polymer electrolytes (SPEs) are promising alternatives to the flammable liquid electrolytes that are currently used in most commercial lithium-ion batteries. Because the transport of ions occurs through segmental motions of the polymer, ionic conductivity typically decreases as the mechanical strength of the SPE increases [1]. Much research has been devoted to the use of microphase separation to achieve mechanically strong SPEs that still retain a high ionic conductivity.
Methods: Previous studies of microphase separated SPEs include so-called molecular composites, with rigid poly(p-phenylene) backbones bearing flexible oligo(ethylene oxide) side chains [2]. In the present study, we have prepared poly(p-phenylenes) using nickel(0) mediated Yamamoto polymerization [3, 4]. These polymers were subsequently doped with lithium bis(trifluoromethane) sulfonimide and characterized as SPEs with a focus on thermal properties, morphology, and ionic conductivity.
Results: Yamamoto polymerization via in situ reduction of Ni(II) yielded polymers with intermediate molar mass (~60 repeating units). The polymers showed high thermal stability and exhibited phase structures consisting of layers of poly(p-phenylene) separated by the ethylene oxide side chains. The ionic conductivity of the SPEs depended on both the length of the ethylene oxide side chains and the lithium ion concentration, and reached 1.1·10-4 S cm-1 at 80 °C.
Conclusions: The combined results showed an efficient and straightforward polymerization, ordered phase structure, and moderate ionic conductivities, demostrating the potential of molecular composites for applications as SPEs in different electrochemical applications.
Selected references
  1. Hallinan DTJ, Balsara NP. Annu Rev Mater Res 43 (2013) 503-525
  2. Lauter U, Meyer WH, Wegner G. Macromolecules 30 (1997) 2092-2101
  3. Yamamoto T, Yamamoto A. Chem Lett 6 (1977) 353-356
  4. Yamamoto T, Hayashi Y, Yamamoto A. Bull Chem Soc Jpn. 51 (1978) 2091-2097