LiCoPO4 mechanical properties evaluated by nanoindentation

LiCoPO4 is a promising cathode material for use in high voltage Li-ion batteries. One of the problems with LiCoPO4 is limited cycle life. One possible cause for the limited cycle life of LiCoPO4 is mechanical degradation. As a consequence, the mechanical properties, elastic modulus, E, and fracture toughness, Kic, of hot-pressed dense (similar to 98%) polycrystalline (15-20 mu m) single phase LiCoPO4 were investigated. E for the hotpressed LiCoPO4 specimen is similar to 137 GPa while the E value for the LiCoPO4 specimen after annealing at 600 degrees C is 106 GPa. The fracture toughness of the hot-pressed LiCoPO4 sample is similar to 0.41 MPa m112, which increased to similar to 0.53 MPa 111112 after annealing. These low Ific values reveal that LiCoPO4 is a brittle material. It is believed that the decrease in E and increase in Kic with annealing is associated with a reduction in residual stress. Published by Elsevier Ltd and Techna Group S.r.l.