Selenium 도핑에 의한 3V급 스피넬 망간상에서 Jahn-Teller distortion 극복

Abstract

Recently, the spinel LiMn2O4 and its derivatives are the most actively studied cathode materials for lithium secondary batteries because of their low cost, abundance and nontoxic. However, wider usage of these materials has been limited because of their poor cycling performance. In the charge and discharge processes, lithium ions are reversibly inserted into and extracted out of LixMn2O4 spinel phase in two composition ranges of 0≤X≤1 and 1≤X≤2 which induce two voltage plateaus located at 4 and 3 V, respectively. It has been proposed that the reasons for the capacity fading are instability of organic-based electrolyte, dissolution of electrode surface in electrolyte, etc. at 4V range. However, In the 3 V range, lithium ion is inserted into empty 16c octahedral sites of LixMn2O4 (i.e., 1≤X≤2), and there is a severe crystallographic Jahn-Teller distortions. Thus LiMn2O4 spinel phase is more stable on the higher plateau and its use is limited to the 4V range. In this work, we have synthesized selenium doped spinel Li1.0SexMn2-xO4 powders using a sol-gel method with glycolic and polyacrylic acid. The structural and electrochemical properties of the synthesized powders were measured and correlated to explain the electrochemical activity of the materials. This materials shows that the discharge capacity of 120, 100 mAh/g using polyacrylic and glycolic acid, respectively, with excellent cyclability in the 3 V range.