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Layered Li[Mn1⁄3Ni1⁄3Co1⁄3]O2 cathode material was synthesized by carbonate coprecipitation method. SEM observation and X-ray diffraction experiment showed that the material with spherical particle morphology was successfully synthesized by the method. The cathode material delivered 180 mAh/g as an initial discharge capacity at 0.2 mA/cm2 and showed high average capacity retention ratio of 99.85%/cycle over 40 cycles.

We have developed silica-composite nonwovens using polyolefin fiber and nanosize silica powder. The silica-composite nonwoven showed better wettability than the polyolefin-based microporous membrane and nonwoven. It was found that the Gurley value of the silica-composite nonwoven has to be higher than 200 s 100 cm −3 in order to suppress a microshort of battery. It was confirmed that the silica-composite nonwovens showed higher maximum power than that of the Celgard membrane by instantaneous discharging test. The cells with the silica-composite nonwovens showed better cycling performances than that of the Celgard membrane at a moderate C-rate of 0.5. A hot-oven test using charged cells up to 4.2 V exhibited that the cells with the silicacomposite nonwovens are thermally stable at 150°C, whereas the cell with the Celgard membrane showed a short circuit probably due to thermal shrinkage of the separator.

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