Surface Modification on Charge-Discharge Capacity of LiMn2O4 Electrode Material

• Main Authors: Hung-Chi Liao, 廖宏奇
• Other Authors: Tsang-Tse Fang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/15222930699720890605

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 93 === 　Spinel phase LiMn2O4 has been considered to replace LiCoO2 cathode material for lithium-ion rechargeable batteres because of its lower cost, high energy density and lower toxicity. The purpose of this study is to enhance the capacity by using the Pechini process and decrease the capacity fading effectively by surface modification of LiMn2O4 cathode material. 　Using Pechini process through the continuous stove heat treatment has been developed to synthesize LiMn2O4 powders. For the purpose to acquire completely LiMn2O4 powders, a post heat treatment should be performed. The powders (LMO800) with post heat treatment have superior discharge capacity. Through analyzing by XRD and manganese valence titration, it could be found that an increase in the crystallinity of the LiMn2O4 powders and manganese average valence of powders close to 3.5 after post heat treatment. The initial discharge capacity may be related to the crystallinity of the powders and manganese valence. 　In this study, the surface of LiMn2O4 (LMO800) was covered with lithium nickel manganese oxide prepared by the Pechini process. After 50 cycles at 25℃, the bare LiMn2O4 showed 88% of the initial discharge capacity and surface-modified LiMn2O4 showed 95% of the initial discharge capacity. After 50 cycles at 55℃, the bare LiMn2O4 showed only 70% of the initial discharge capacity and surface-modified LiMn2O4 showed 94% of the initial discharge capacity. Thus, electrochemical performance of the LiMn2O4 can be improved by the surface modification with Li-Ni-ion. This action improves cyclability for lithium battery performance and reduces capacity fades of LiMn2O4 at elevated temperatures. Through analyzing by ICP, XPS and EDS, it can be explained by suppression of Mn dissolution in the electrolyte.