The structure of an amorphous polymer electrolyte model material, PPO-LiClO4, has been investigated on the short-range length scale using neutron diffraction H/D isotope substitution experiments. We report experimental results which may be attributed to a lithium ether-oxygen distance of about 2.1 Angstrom The findings indicate, within the experimental accuracy, that the cation environment of the Li+ ion in PPO-LiClO4 O:M = 16:1 is approximately the same as reported for crystalline and amorphous complexes of PEO and lithium salts. (C) 2000 Elsevier Science Ltd. All rights reserved.