Enhanced electrochemical properties of a LiNiO2-based cathode material by removing lithium residues with (NH4)2HPO4

Lithium residues on the surface of LiNi0.8Co0.1Mn0.1O2 have been removed by adding (NH4)(2)HPO4 dissolved in ethanol. Upon precipitating the unmeasurable lithium residue with different amounts of (NH4)(2)HPO4, the performance of the LiNi0.8Co0.1Mn0.1O2 cathode materials show marked changes. Under the optimized condition, the modified materials exhibit enhanced cycling performance, although X-ray powder diffraction and transmission electron microscopy results demonstrate that the precipitated Li3PO4 is not coated on the surface of LiNi0.8Co0.1Mn0.1O2. The modified material exhibits 66.9% retention after 100 cycles at 2 C, while the pristine material shows only 48.1% retention. The results demonstrate that the removal of lithium residues from the surface of LiNiO2-based materials is effective in decreasing side reactions. This property will be valuable for increasing the available choices of coating methods and materials because the enhancement of the coating will be maximized if the lithium residue can be removed after coating.