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A sol-gel method was used to fabricate Al-oxide coated LiNi1/3Co1/3Mn1/3O2 cathodes and their surface structure and high-voltage charge/discharge characteristics were evaluated with a view to their potential use in Li-ion batteries. Scanning transmission electron microscopy (STEM) revealed that a solid solution of LiAlO2-LiNi1/3Co1/3Mn1/3O2 is uniformly formed to a depth of several nanometers from the surface of Al-oxide coated LiNi1/3Co1/3Mn1/3O2. Furthermore, the discharge capacity and average discharge voltage of Al-oxide coated LiNi1/3Co1/3Mn1/3O2 is equal to or higher than uncoated LiNi1/3Co1/3Mn1/3O2 at a charge voltage of 4.5 to 4.9 V. It was also found that the Al-oxide coating significantly improves the cycle performance at a charge voltage of 4.5 to 4.7 V. A substantial fade in capacity observed during the cycling of bare LiNi1/3Co1/3Mn1/3O2 is attributed to an increase in polarization due to an increased charge transfer resistance (Rct), which is indicative of degradation of the interface between the electrode and electrolyte. However, this increase in polarization and Rct is effectively suppressed in the Al-oxide coated LiNi1/3Co1/3Mn1/3O2. This can be explained by an inhibition of the formation of a rock-salt-structured phase in the surface region of bare LiNi1/3Co1/3Mn1/3O2 during cycling, as confirmed by STEM and electron energy loss spectrometry. [ABSTRACT FROM AUTHOR]

To understand the effect of surface modification on the degradation of battery materials, analytical transmission electron microscopy (TEM), which provides fine structure and chemical state with high spatial resolution, was applied. To address current issues about the artificial damage around the surface region of cathodic oxide particles from sample preparation, such as ion milling, LiCoO2 submicron particles were synthesized by using the Pechini method; LiCoO2 particles modified by the oxides of Zr were prepared by using the evaporation and dryness method. Smaller Zr-oxide particles with a diameter of about 10 nm and partial coverage were deposited on LiCoO2 to explore the effect of coating. The cycling properties of a cell containing LiCoO2 were improved by coating with Zr oxides even in the inhomogeneous coverage. Capacity retention was found to be virtually the same as that of cells containing LiCoO2 coated with 5 wt% and 10 wt% oxides of Zr. Our TEM results revealed a thin Li-Zr oxide overlayer on the LiCoO2 surface, where Zr-oxide particles were not deposited. It is suggested that this thin overlayer can provide an effective improvement of the electrochemical performance. [ABSTRACT FROM AUTHOR]

One way of increasing the energy density of lithium-ion batteries is to use electrode materials that exhibit high capacities owing to multielectron processes. Here, we report two novel materials, Li2TiS3 and Li3NbS4, which were mechanochemically synthesised at room temperature. When used as positive-electrode materials, Li2TiS3 and Li3NbS4 charged and discharged with high capacities of 425 mA h g–1 and 386 mA h g–1, respectively. These capacities correspond to those resulting from 2.5- and 3.5-electron processes. The average discharge voltage was approximately 2.2 V. It should be possible to prepare a number of high-capacity materials on the basis of the concept used to prepare Li2TiS3 and Li3NbS4. [ABSTRACT FROM AUTHOR]

LiCoO2 particles about 300 nm in size were synthesized by the Pechini method. LiCoO2 modified using Al oxide and Si oxide were also prepared by the sol-gel method. These samples allowed direct TEM observation without sampling damage, and homogeneous distribution of coating materials on the surface was confirmed. The cycling properties of LiCoO2 coated with Al oxide were improved compared with pristine LiCoO2. Samples modified with Si oxide showed poor electrochemical performance. From an analytical TEM study, there was a thin layer of Co and Al mixture on the LiCoO2 surface in the Al oxide coated LiCoO2. By Si oxide coating, a homogeneous layer about 5 nm in thickness was formed. Using an EELS study, the Li ion concentration in particles was mapped under monochromatized electron beam conditions. Homogeneous Li distribution was confirmed in the cycled particles in LiCoO2 coated by Al oxide. In contrast, an inhomogeneous Li distribution was found in pristine and LiCoO2 with Si oxide coating. [ABSTRACT FROM AUTHOR]

By means of a surfactant-assisted hydrothermal method, we have successfully synthesized sodium manganese oxide nanorods with 2 × 4 tunnel structure using layered manganese oxide as starting material. The nanorods have diameters of ca. 20 nm and lengths up to 1 m. Not only the morphological change of manganese oxide from particle to rod but also the structural change from layer to tunnel have simultaneously been achieved during the hydrothermal treatment. The specific capacitance of thus obtained nanorods reaches to 140 F/g. About 57% of the capacitance at 1 mV/s could be maintained when the scan rate was increased to 100 mV/s. [ABSTRACT FROM AUTHOR]