Enhanced structure and electrochemical stability of single crystal nickel-rich cathode material by La2Li0.5Co0.5O4 surface coating

The emergence of single crystal nickel-rich cathode materials preparation offsets the poor cycle performance of traditional ternary cathode materials, with an efficient enhancement of the energy density. Despite all this, the stability of single crystal Ni-rich materials is still hard to fully meet the commercial requirements. We select La and Co elements for co-coating single crystal cathode materials by an efficient method, La2Li0.5Co0.5O4 coating layer with a thickness of about 5 nm is successfully formed on the single crystal nickel-rich samples. The coating layer effectively protect nickel-rich materials from the corrosion of electrolyte and retain a high Li-ion conductivity during charge/discharge processes. Besides, the part of residual lithium reacts with La and Co, forming La2Li0.5Co0.5O4 coating layer, and decorates the materials surface. Eventually, the single crystal NCM811 with 2 wt% La2Li0.5Co0.5O4 coating affords a terrific cyclic stability after 200 cycles. The capacity retention is 81.15% at 1 C with voltage range of 2.8–4.3 V, obtaining an 18% performance improvement compare with that of pristine material. Moreover, the rate performance and first charge/discharge efficiency are improved to a certain extent. The co-coating process with La and Co is a competitive approach to modify the performance of single crystal nickel-rich cathode materials and contribute to the commercial application of the NCM811 materials.