Optimization of the Li-ion conductivity of UiO-66 coated LiCoPO4 nanocomposites

LiCoPO4 coated by different concentrations of UiO-66 (LiCoPO4@xUiO-66) samples, with x = 0.0, 0.01, and
0.02, were successfully synthesized. XRD spectra confirmed that the samples have a single orthorhombic phase
with the Pnmɑ space group. The microstructure of these samples was investigated via TEM. Besides, all expected
elements appeared in the XRF spectra in the same stoichiometry ratios of the raw materials. The XAS spectra of
UiO-66-coated LiCoPO4 samples with varying contents are similar to that of pure LiCoPO4 both in terms of the
position of the absorption edge and the highest position. The values of BET-specific surface areas and meso-to
macropore volume of the LiCoPO4@UiO-66 composites increased with UiO-66 additions. Interestingly, the
ionic conductivity of LiCoPO4@UiO-66 composites increased by UiO-66 additions. Because of the UiO-66 coating
on LiCoPO4, these composites have a 3D tunable porous structure while retaining their composition and crystal
structure. This 3D-tunable porous structure easily allows Li+ ion migration. The observed results exhibit a new type of synthetic post-modification of the organic/inorganic UiO-66 subunits, yielding a unique electrode possibly suited for Li-ion batteries.