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

Abstract

Lithium residues on the surface of LiNi_0.8Co_0.1Mn_0.1O₂ have been removed by adding (NH₄)₂HPO₄ dissolved in ethanol. Upon precipitating the unmeasurable lithium residue with different amounts of (NH₄)₂HPO₄, the performance of the LiNi_0.8Co_0.1Mn_0.1O₂ 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 LiNi_0.8Co_0.1Mn_0.1O₂. 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.