Surface Coating and Electrochemical Properties of LiNi0.8Co0.15Al0.05O2 Cathode in Lithium-Ion Cells

LiNi0.8Co0.15Al0.05O2, as the cathode materials for lithium ion battery, were prepared from the precursors, Ni0.8Co0.15Al0.05(OH)2 which were synthesized by chemical co-precipitation method. LiNi0.8Co0.15Al0.05O2 particles are modified with AlF3 and AlPO4. Even though the initial discharge capacity of the coated LiNi0.8Co0.15Al0.05O2 was decreased that of the pristine material, the capacity retention and the thermal stability, in a highly oxidized state are both significantly improved. This effect is attributed to the thin coating layer protecting the oxidized cathode particles from being attacked by hydrogen fluoride in the electrolyte. The cycling behavior of the AlF3-coated LiNi0.8Co0.15Al0.05O2 is quite stable showing good capacity retention (96.3% of its initial capacity after 30 cycles).