The high resolution NMR spectrum of a sample with a PEO Li ratio of 3 2 is consistent with at least two Li environments, one solvated by the polymer and one in small ionic clusters.
The proposed Li environments are shown in Figure 4f.
Given the experimentally observed intensities, the Li ions must be removed from the Liβ sublattice, yielding two Li environments in a 1 1 ratio, in agreement with the Li NMR results.
A single isotropic resonance is observed in both the P and Li NMR spectra (δiso of 2985 ppm and −104 ppm, respectively) as expected from single distinct P and Li environments in LiCoPO4.
The ex situ NMR spectra of a range of delithiated samples provide direct insight into the P and Li local environments occurring in the intermediate phase: two Li environments are present in a 1 1 ratio (one environment containing a first coordination shell of only Co2+ cations), along with two P environments in a 2 1 ratio.
Note that the different spin spin (T2) relaxation times for the two P and two Li environments have been accounted for in the intensity analysis (see the Supporting Information).
They can be superimposed onto each other by a translation in the direction perpendicular to the Co chains (see the Supporting Information), which, as observed in Figure 3d, results in a total of two distinct Li environments: four Li sites surrounded by six Co2+ (denoted Liα, Figure 4d) and eight Li sites surrounded by three Co2+ and three Co3+ (denoted Liβ, Figure 4e).
Because the P Fermi contact shifts are much more sensitive to the nature and/or oxidation state of the transition metals in the first coordination shell than the Li NMR spectra, we first analyze the P spectra before proceeding to examine the Li environments.
Shao-Meng Li, another Environment Canada scientist and co-author of the study, said the S.O.A. particles tended to lower temperatures by reflecting energy back toward the sun.
The comparison with pure rutile-FeF2 showed that the Li local environments were similar to those of the FeF3 system lending further support to the experimental data.
