Solid-state NMR Studies of Al-doped and Al 2O 3-coated LiCoO 2

Abstract

As a cathode material for commercial lithium rechargeable battery, Al-doped and Al 2O 3-coated LiCoO 2 were structurally characterized and compared by using solid-state 7Li and 27Al magic angle spinning (MAS) NMR. The structural states of lithium and aluminum in those samples were successfully identified by calculation of NMR spectra. 7Li MAS NMR spectra of samples had shown similar features having more than three lithium sites, which were determined as quadrupole coupling constant with the same asymmetric parameter ( η = 0.1); C Q = 1.10 MHz for octahedral site, and C Q = 2.97 MHz and C Q = 3.83 MHz for shoulders. 27Al MAS NMR spectra of samples, however, showed significant difference in two observed aluminum sites. In the simulation of NMR spectrum for Al 2O 3-coated LiCoO 2, the values of C Q and η were obtained; 4.45 MHz and η = 0.86 for tetrahedral site and 4.31 MHz and η = 0.81 for octahedral.