liquid electrolyte. The ability to plate/strip a lithium anode from an organic-liquid electrolyte has recently been demonstrated. [2] However, the limited capacities of the transition-metal oxides used as cathodes [3] have created a growing interest in the lithium-sulfur (Li-S) battery [4] because sulfur (S 8 ) units are reduced to dilithium sulfide (Li 2 S) to give a theoretical capacity of 1675 mA h g −1 . However, a principal impediment of the sulfur cathode has been the existence of intermediate Li 2 S x polysulfides that are soluble in the organicliquid electrolytes; failure to capture all of the dissolved polysulfides on surfaces electronically connected to the cathode current collector for reversing the reduction reaction rather than poisoning the anode has resulted in a poor cycle life of a Li-S cell. [5] Considerable effort has been devoted to tailoring carbonaceous frameworks and adding carbon interlayers for inhibiting polysulfide dissolution and/or capture of the polysulfides on a surface where the sulfur-reduction reaction can be reversed; [6] but this strategy has not been completely successful [7] partly because carbon possesses nonpolar properties, [8] which makes difficult facile adsorption of polysulfides [9] as well as feeble reduction/oxidation of Li 2 S. With another strategy, several groups [10] have reported that heterogeneous adsorption sites can be provided by metal oxides or sulfides having sulfophilic surfaces. However, although it has been noted that the heteropolar property on the reaction site prefers charge transfer from metal disulfide to soluble polysulfides, there are practical limitations that prevent the polysulfides from being sufficiently bound at high sulfur loading.

Al-substituted Li 7 La 3 Zr 2 O 12 (LLZO) pellets with a grain size of 100-200 µm and a relative density of 94% were prepared by conventional solid-state processing at a sintering temperature of 1100° C, 130°C lower than previously reported. Morphological features and the presence of impurities were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) was used to visualize the distribution of impurities. The results suggest that chemical composition of the powder cover strongly affects morphology and impurity formation, and that particle size control is critical to densification. These properties, in turn, strongly affect total ionic conductivity and interfacial resistance of the sintered pellets.3

Surface coating of cathode materials with AlO has been shown to be a promising method for cathode stabilization and improved cycling performance at high operating voltages. However, a detailed understanding on how coating process and cathode composition change the chemical composition, morphology, and distribution of coating within the cathode interface and bulk lattice is still missing. In this study, we use a wet-chemical method to synthesize a series of AlO-coated LiNiCoMnO and LiCoO cathodes treated under various annealing temperatures and a combination of structural characterization techniques to understand the composition, homogeneity, and morphology of the coating layer and the bulk cathode. Nuclear magnetic resonance and electron microscopy results reveal that the nature of the interface is highly dependent on the annealing temperature and cathode composition. For AlO-coated LiNiCoMnO, higher annealing temperature leads to more homogeneous and more closely attached coating on cathode materials, corresponding to better electrochemical performance. Lower AlO coating content is found to be helpful to further improve the initial capacity and cyclability, which can greatly outperform the pristine cathode material. For AlO-coated LiCoO, the incorporation of Al into the cathode lattice is observed after annealing at high temperatures, implying the transformation from "surface coatings" to "dopants", which is not observed for LiNiCoMnO. As a result, AlO-coated LiCoO annealed at higher temperature shows similar initial capacity but lower retention compared to that annealed at a lower temperature, due to the intercalation of surface alumina into the bulk layered structure forming a solid solution.