Synergistic Effects of Surface Coating and Bulk Doping in Ni-Rich Lithium Nickel Cobalt Manganese Oxide Cathode Materials for High-Energy Lithium Ion Batteries.
Ni-rich layered oxide cathodes are promising candidates to satisfy the increasing energy demand of lithium-ion batteries for automotive applications. Thermal and cycling stability issues originating from increasing Ni contents are addressed by mitigation strategies such as elemental bulk substitution ("doping") and surface coating. Although both approaches separately benefit the cycling stability, there are only few reports investigating the combination of two of such approaches. Herein, the combination of Zr as common dopant in commercial materials with effective Li2 WO4 and WO3 coatings was investigated with special focus on the impact of different material processing conditions on struct…
Effect of anion substitution on the structural and transport properties of argyrodites Cu7PSe6−xSx
Inspired by the good performance of argyrodites as ion conducting thermoelectrics and as solid electrolytes we investigated the effect of isovalent S2- substitution for Se2- in Cu7PSe6. At room temperature Cu7PSe6 crystallizes in the primitive cubic β-polymorph of the argyrodite structure and transforms to the face-centered high-temperature (HT) γ-modification above 320 K. The transition for the homologous Cu7PS6 occurs at 510 K. Promising thermoelectric and ion conducting properties are observed only in the HT modification, where the cations are mobile. Using Rietveld refinements against X-ray diffraction data the effect of isovalent S2- substitution for Se2- on the structural and transpor…