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Both particle monodispersity and mesopore orientation have been considered in this work. Monodisperse spherical silica particles with a solid core and a mesoporous shell featuring mesopore channels perpendicular to the core surface were synthesized for the first time by adopting silica particles as the core component and by employing C n -TAB (n = 12, 14, 16, 18), the structure-directing agent for the mesoporous shell. Micelles on the surface of the silica particles are formed from the electrostatic interaction between the partially negatively charged silica particles and the positively charged surfactant molecules under basic conditions. The particles synthesized in this work have a uniformly coated thin mesoporous shell of about 28-61 nm in thickness over the silica core and possess a surface area of ca. 370-500 m 2 g 21 , pore volume of ca. 0.2-0.35 cc g 21 , and narrow pore size distribution.

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Nanocrystalline Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 powders were prepared by a simple combustion method and investigated using X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), particle size analysis (PSA), and galvanostatic charge/discharge cycling. According to the XRD analysis, single-phase compounds with a layered structure were obtained for powders with 0 ¡ x ¡ 0.25, while mixtures were obtained for powders with 0.30 ¡ x ¡ 0.50. Rietveld analysis revealed that single-phase Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 is basically a layered rock-salt structure in which a small amount of Ni occupies the 3a sites. The initial discharge capacity of a Li/Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 cell with x ~0.20 was about 288 mA h g 21 , corresponding to about 91% of the theoretical value, when it was cycled in the voltage range of 4.8-2.0 V with a specific current of 20 mA g 21 at 30 uC. As far as we know, charge/discharge cycling on an Li/Li[Ni 0.20 Li 0.20 Mn 0.60 ]O 2 cell gives the highest discharge capacity of 288 mA h g 21 among the LiMO 2 -based (M ~Co, Ni, and Mn) cathode materials. A very promising factor for high-rate capability applications was an excellent rate capability in continuous cycling at specific currents ranging from 20 mA g 21 to 900 mA g 21 , due to the nanocrystalline particle size of 80-200 nm. The origin of the 4.5 V plateau was investigated by means of weight loss measurement and XAS for the charged/discharged electrodes. The weight loss measurement for the charged electrodes gave indirect evidence that the 4.5 V plateau did not originate from the ejection of oxygen. In XAS, the Mn oxidation state of 41 did not change during the charge/discharge process, and surprisingly the Ni did not further oxidize beyond about 31.

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Surface coating is essential for the cathode materials applied in all-solid-state batteries (ASSBs) based on sulfide electrolytes because of the instability of the cathode/sulfide interface. In contrast with those for general lithium ion batteries (LIBs) using a liquid electrolyte, the coating materials for ASSBs require different functional properties such as high ionic conductivity, low reactivity with sulfide electrolytes, and low electronic conductivity. In addition to LiNbO3, which is the most popular coating material for ASSBs, LiTaO3 is another highly promising coating material, and both materials mostly satisfy these requirements. In this work, LiTaO3 and LiNbO3 were used to coat the surface of LiNi0.82Co0.12Mn0.06O2 cathodes for ASSBs. Further, the effects of two different coating methods, postcoating and precursor-based (PB) coating, were characterized and compared. The postcoating method simply forms a coating layer, whereas the PB coating method offers an additional doping effect owing to the diffusion of coating ions into the cathode structure. Surface coating considerably increased the capacity of the ASSB cathodes under all experimental conditions. With the same coating amount and method, the effect of the LiTaO3 coating was similar or superior to that of the LiNbO3 coating. Compared with the postcoating method, however, the PB coating method resulted in a superior rate capability and cyclic performance, which was mostly attributed to the doping effect of Ta or Nb. An X-ray photoelectron spectroscopy analysis confirmed that both the LiTaO3 and LiNbO3 coatings suppressed side reactions. Among the coatings we examined, the LiTaO3 coating prepared by the PB method most effectively enhanced the electrochemical performance of the cathodes for sulfide electrolyte-based ASSBs.