Electrochemical behavior of lithium-iron oxide electrode and measurement of chemical diffusion coefficient of lithium

Abstract

Various compositions of iron oxide based materials as a cathode of litthium secondary battery have been fabricated and tested with electrochemical method. A layered form of LIFeO2 was synthesized by mixing and heating the initial materials of FeCl3 6H2O3 LiOH and NaOH at low temperature. The effect of changing the precuresors composition was investigated. As a result, when increasing the additive amount of NaOH, the capacity of the electrode is dedreased but the performance and declining rate of capacity became smaller. LiFeO2 synthesized with the weight ratio of NaOH/FeCl3/LiOH, 2/1/7 showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles. Charge-discharge tests of lithium cell with LiFeO2 cathode having the layer structure were performed. This cell showed the reversivility in the range of 1.5-4.5 V of cell voltage. By using CPR method, chemical diffusion doefficients were measured in 1 M LiPF6/EC/DEC solution. The value of chemical diffusion coefficient decreased with increasing the lithium content x, in 0.5<x<1, and was around 10-11cm2/s.