Ab initio structure solution of the polymer electrolyte poly(ethylene oxide)₃:LiAsF₆

The crystal structure of the polymer electrolyte complex PEO3:LiAsF6 has been determined ab initio from X-ray and neutron powder diffraction data using a simulated annealing approach in direct crystallographic space. The structure consists of rows of Li+ cations encapsulated within PEO helices and coordinated by three ether oxygens and two fluorines from two anions. This is the first polymer electrolyte structure in which fluorines coordinate directly to the cations. Although the conformation of each individual polymer chain and the arrangement of the cations and anions are similar to previously determined 3:1 complexes containing Li salts, the stacking and separation of neighboring chains are markedly different. This prevents elucidation of the structure using conventional refinement by the Rietveld method.