Mobility of Li cations in X zeolites studied by solid-state NMR spectroscopy
Abstract 6 Li and 7 Li MAS NMR spectra of the dehydrated zeolites LiX-1.0 [(SiAlO 4 ) 96 Li 96 ] and LiX-1.25 [(Si 106 Al 86 O 384 )Li 86 ] contain three peaks belonging to cations in the crystallographic sites SI′, SII, and SIII. 7 Li MAS NMR spectra recorded at variable temperature show that the SIII cations are mobile at temperatures above 233 K in case of LiX-1.0, and above 273 K in case of LiX-1.25. The mobility of the SIII cations causes a shorter T 1 for SIII in comparison to the non-mobile six-ring cations of LiX-1.0 at 293 K. An activation energy of 13 kJ mol −1 was determined for the SIII cations in the temperature range of T =233–313 K. We predict that the Li ion conductivity of zeolite LiX-1.0 will be higher than the Li ion conductivity of any zeolite reported up to date.