Lithium carbonate is an unavoidable impurity at the cathode side. It can react with LiPF₆-based electrolyte and LiPF₆ powder to produce LiF and CO₂, although it presents excellent electrochemical inertness. Samples of Li₂CO₃-coated and LiF-coated LiNi_0.8Co_0.1Mn_0.1O₂ were prepared to compare their influence on a cathode's behavior. After 200 cycles at 1C, in contrast to 37.1% of capacity retention for the Li₂CO₃-coated material, the LiF-coated LiNi_0.8Co_0.1Mn_0.1O₂ retained 91.9% of its initial capacity, which is similar to the fresh sample. This demonstrates that decomposition of Li₂CO₃ can seriously deteriorate cyclic stability if this occurs during working.