We report on the extraordinary superionic conductivity in the fulleride polymer Li 4 C 60, a crystalline material with no disorder. Li 7, NMR, and dc frequency dependent conductivity show uncorrelated ionic hopping across small energy barriers (Δ E a∼ 200 meV) and an ionic conductivity of 10− 2 S/cm at room temperature, higher than in “standard” ionic conductors. Ab initio calculations of the molecular structure find intrinsic unoccupied interstitial sites that can be filled by Li+ cations in stoichiometric Li 4 C 60 even at low temperatures. The low energy required for the occupation of these sites allows a sizable Li+ diffusion above 130 K. The results suggest novel application of lithium intercalated fullerides as electrodes in Li ions batteries.
American Physical Society
8 Apr 2009
Volume: 102 Issue: 14 Pages: 145901
Physical review letters