Stabilizing the surface of Ni-rich cathodes via facing-target sputtering for high-performance lithium-ion batteries

Abstract

Although efforts have been made to increase the Ni content in Ni-rich cathodes for Li-ion batteries with high specific capacities, an unstable surface of the cathode and electrolyte remains a significant challenge. To stabilize the surface, various protective layers – such as aluminum oxide (Al₂O₃) – have been introduced on the surface of Ni-rich cathodes. In this study, we used a facing-target sputtering (FTS) method to avoid the reaction of residual Li and moisture from the precursor for the coating method, and to build a dense, homogeneous, protective, ultrathin Al₂O₃ layer at the surface of NCM811. It was proven that FTS rules out the presence of the LiOH byproduct of residual Li on the NCM811 during surface modification. Ensuring interface protection by using FTS instead of atomic layer deposition with an H₂O-based precursor was identified as a crucial determinant of the NCM811 performance. Our findings present an updated and promising process for stabilizing the surface, demonstrating the need to select a technique to achieve surface passivation of Ni-rich cathodes and improvements in cycling performance.