In Situ Surface Modification for Improving the Electrochemical Performance of Ni‐Rich Cathode Materials by Using ZrP₂O₇

Abstract

Ni-rich layered LiNi_0.8 Mn_0.1 Co_0.1 O₂ (NCM811) cathode material has promising prospects for high capacity batteries at acceptable cost. However, LiNi_0.8 Mn_0.1 Co_0.1 O₂ cathode material suffers from surface structure instability and capacity degradation upon cycling. In this study, in situ ZrP₂ O₇ coating is introduced to provide a protective structure. The optimum modification amount is 1.0 wt %. A series of characterization methods (X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy) verify the generation and structure of the coating layer. Electrochemical performance tests demonstrate that the cycle retention rate increases from 66.35 to 86.92 % after 100 cycles at 1 C rate. The dense inorganic pyrophosphate layer not only has chemical stability against the electrolyte but also eliminates surface residual lithium. The protective layer and the matrix are strongly joined by high-temperature heating, thereby giving a certain mechanical strength and protecting the overall structure of the topography. Therefore, the cycle and rate performance are enhanced by the modification with ZrP₂ O₇ .