NEGATIVE ELECTRODE MATERIAL FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, MAKING METHOD AND LITHIUM ION SECONDARY BATTERY

摘要

A negative electrode material for nonaqueous electrolyte secondary batteries comprises composite particles which are prepared by coating surfaces of particles having silicon nano-particles dispersed in silicon oxide with a carbon coating, and etching the coated particles in an acidic atmosphere. The silicon nano-particles have a size of 1-100 nm. The composite particles contain oxygen and silicon in a molar ratio: O<O/Si<1.0. Using the negative electrode material, a lithium ion secondary battery can be fabricated which features a high 1st cycle charge/discharge efficiency, a high capacity, and improved cycle performance.