Solvothermal water-diethylene glycol synthesis of LiCoPO 4 and effects of surface treatments on lithium battery performance.

Olivine-structured LiCoPO 4 is prepared via a facile solvothermal synthesis, using various ratios of water/diethylene glycol co-solvent, followed by thermal treatment under Ar, air, 5%H 2 /N 2 or NH 3 . The diethylene glycol plays an important role in tailoring the particle size of LiCoPO 4 . It is found that using a ratio of water/diethylene glycol of 1 : 6 (v/v), LiCoPO 4 is obtained with a homogenous particle size of ∼150 nm. The bare LiCoPO 4 prepared after heating in Ar exhibits high initial discharge capacity of 147 mA h g -1 at 0.1C with capacity retention of 70% after 40 cycles. This is attributed to the enhanced electronic conductivity of LiCoPO 4 due to the presence of Co 2 P after firing under Ar. The effects of carbon, TiN and RuO 2 coating are also examined. Contrary to other studies, it is found that the solvothermally synthesised LiCoPO 4 samples produced here do not require conductive coatings to achieve good performance.