리튬이차전지용 층상계 Li[NixCo(1-x)/3Mn2(1-x)/3]O2 양극활물질의 전기화학적 및 열적 특성에 관한 연구

Abstract

The electrochemical performance and thermal stability of the Li[NixCo(1-x)/3Mn2(1-x)/3]O2 (x=0.55, 0.65, 0.75 and 0.85) as a cathode materials for the lithium-ion battery were investigated. The prepared powders were synthesized by co-precipitation method and have well ordered O3 type α-NaFeO2 layered structure(R3m). With increasing Mn content, the electrochemical properties and thermal stabilities were excellent relatively. Especially, Li[Ni0.55Co0.15Mn0.30]O2 cell was superior. The large amount of inactive Mn4+ enhanced the structure in the layered oxide matrix and suppressed the charge transfer resistance between the active materials and electrolyte during the cycling tests. The TEM images show the phase transition of Mn-less materials from layered structure to spinel structure. The structure change can induce the volume expansion. Thus, the Mn-less materials(Li[Ni0.85Co0.05Mn0.10]O2) show poor cycling performance. Also, the thermal property is improved with increasing Mn content.