Synthesis and electrochemical characterizations of dual doped Li_1.05Fe_0.997Cu_0.003PO₄

Dual doped Li_1.05Fe_0.997Cu_0.003PO₄ material was synthesized at 660 °C in Ar atmosphere by a solid-state method. It showed well developed XRD patterns without any impurity peaks such as FeP or metallic Fe₂P at 2θ = 41°, which enhance the electrochemical capacity of the Li/LiFePO₄ system. Li_1.05Fe_0.997Cu_0.003PO₄ was composed of many large polycrystalline-type particles with sizes between 200 and 300 nm and small particles from 20-50 nm distributed among the larger particles. The Li/Li_1.05Fe_0.997Cu_0.003PO₄ cell showed the highest initial discharge capacity, greater than 145 mAh/g, which was substantially higher than the Li/LiFePO₄ cell, 19 mAh/g, under the same test conditions. This might result from enhancement of the contact area and electrical conductivity between the small particles in the Li_1.05Fe_0.997Cu_0.003PO₄ from the small amount of Li and Cu substitution.