Synthetic and electrochemical studies of nano-structured LiNiCoO2

• Main Authors: Chen hung ming, 陳宏明
• Other Authors: Liu mao huang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/95158117356559550113

碩士 === 輔仁大學 === 化學系 === 94 === Recently, many researchers are interested in nano-structured cathode materials for lithium ion battery, because the nano-structured cathode materials have the better electrochemical performances, especially related to the capacity at high-rate discharge. The nano-structured effects of material can decrease the polarizations in electrochemistry, but it is not clear of the electron-transfer and mass-transfer mechanisms. In this study, we synthesized the nano-structured LiNiCoO2 and investigated the nano-structured effects in the electrochemistry. The nano-structured LiNi0.8Co0.2O2 were prepared by mixing various nano-structured Ni0.8Co0.2(OH)2 with LiOH．H2O or Li2CO3 then calcined at 720~780 ℃ for 8 ~16 hr. The nano-structured LiNi0.8Co0.2O2 is a 1 ~ 10 μm secondary particle consisted of many 50 ~500 nm primary particles which can aggregate to a porous or dense structure. We had analyzed the chemical and physical properties (XRD/SEM/TEM/density/pH/particle size) of the nano-structured LiNi0.8Co0.2O2 and achieved the electrochemical experiments for these materials. At the same times, the impedance-analysis of nano-structured LiNi0.8Co0.2O2 had been studied and the charge-transfer resistances (Rct) and diffusibilities (DLi+) of lithium ion in layer structure had been calculated. For the nano-structured effects of the materials, a LiNi0.8Co0.2O2 with little primary particles which closely contact each others to decrease the grain boundaries can have the better cycle-life for charge-discharge, because the charge-transfer resistance (Rct) of this material is small and varies slowly for cycling. On the other hand, a LiNi0.8Co0.2O2 with the small primary particles and porous structure can have the high capacities at high-rate discharge, because this material has the good diffusion- path of lithium ion.