METHOD FOR MANUFACTURING POSITIVE ELECTRODE ACTIVE MATERIAL FOR POWER STORAGE DEVICE

An objective of the present invention is to provide a method of preparing a positive electrode active material for a power storage device, the positive electrode active material having improved capacity properties and electron conductivity. The method of the present invention, as a process of preparing a positive electrode active material for a power storage device, the positive electrode active material comprising a lithium silicate compound represented by chemical formula, Li_2MSiO_4, comprises: heat-treating a mixed material at a high temperature; pulverizing the heat-treated mixed material; adding a carbon-based material to the pulverized mixed material; and heat-treating a mixture of the carbon-based material and the pulverized mixed material again. The method according to the present invention enables the positive electrode active material to obtain good crystallinity by increasing reactivity between materials included in the mixed material, and promotes atomization of diameters of crystal grains grown to large sizes and recovery of crystallinities of the crystal grains and is able to support carbon on surfaces of crystallized particles of the mixed material by heat-treating the mixed material at the high temperature. Therefore, the method according to the present invention not only facilitates intercalation/deintercalation of lithium in the obtained positive electrode active material, but also is able to prepare the positive electrode active material for the power storage device with improved electron conductivity. Further, the method according to the present invention can obtain lithium ion secondary batteries with high discharge capacities by manufacturing lithium ion secondary batteries by using the obtained positive electrode active material for the power storage device. 용량 특성 및 전자 전도성이 향상된 축전 장치용 정극 활물질의 제작 방법을 제공하는 것을 과제의 하나로 한다. 화학식 LiMSiO로 표현되는 규산리튬 화합물을 포함하는 축전 장치용 정극 활물질의 제작 공정에 있어서, 혼합 재료를 고온에서 열처리한 후, 분쇄 처리를 행하고, 탄소계 재료를 첨가하여 다시 열처리를 행함으로써, 혼합 재료에 포함되는 물질간의 반응성을 높여, 결정성을 양호하게 함과 함께, 고온 처리에 의해 크게 성장한 결정립 직경의 미립자화 및 결정성의 회복을 도모하면서, 결정화된 혼합 재료의 입자 표면에 탄소를 담지시킬 수 있다. 이에 의해, 얻어진 정극 활물질에 있어서의 리튬의 탈삽입을 용이하게 함과 함께, 전자 전도성을 향상시킨 축전 장치용 정극 활물질을 제작하는 것이 가능하다. 또한, 얻어진 축전 장치용 정극 활물질을 사용하여 리튬 이온 이차 전지를 제작함으로써, 방전 용량이 높은 리튬 이온 이차 전지를 얻을 수 있다.