17 O NMR spectra isolating slow relaxing 17 O environments. the slow relaxation 17 O is dominated by oxide environments coordinated to paramagnetic TM ions (TM–O 2− ), cg = 2,100–2,300 ppm. After discharge, a new 17 O environment is formed corresponding to oxide surrounded by Li (that is, Li–O 2− ) created by the reduction of O 2 in the voids and reinsertion of Li + into the voids coordinated by the O 2− , centred at cg = 0 ppm. D 1 , relaxation delay.
