In Situ Surface Modification for Improving the Electrochemical Performance of Ni-Rich Cathode Materials by Using ZrP2 O7.

Ni-rich layered LiNi0.8 Mn0.1 Co0.1 O2 (NCM811) cathode material has promising prospects for high capacity batteries at acceptable cost. However, LiNi0.8 Mn0.1 Co0.1 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 .