Boosting cycle stability of NCM811 cathode material via 2D Mg-Al-LDO nanosheet coating for lithium-ion battery

Abstract

LiNi0.8Co0.1Mn0.1O2 (NCM811) often suffers from the poor cycle stability as the cathode material for the lithium-ion battery (LIB), while Al2O3 or MgO coating is the most common method to resolve such problem. However, the reported techniques often produced Al2O3 or MgO particles with the large size or zero dimensional (0 D) spheres, which resulted in ununiform or thick layer coating on the surface of NCM811. Herein, Mg-Al layered double oxide (Mg-Al-LDO) nanosheets derived from Mg-Al layered double hydroxide (Mg-Al-LDH) were firstly studied as a potential coating material because of their two dimensions (2D) and few-layer structures (less than 10 nm). The Mg-Al-LDO nanosheets were coated on NCM811 microspheres via the intercalation-exfoliation-calcination strategy. The Mg-Al-LDO nanosheets modified NCM811 samples exhibited enhanced cycle performances. The capacity retention improvements of this work (11–18%) were higher than those of the reports (0.7–15.6%). Typical sample showed the capacity retention of 95.5% after 50 cycles, and it increased by 18% compared with that of pristine NCM811 after 100 cycles within 2.75–4.3 V at 0.5 C rate. This improved cycle performance can be attributed to the unique thin and continuous Mg-Al-LDO nanosheets coated on NCM811, which not only inhibits HF corrosion and the residual alkali salt formation, but also reduces Ni2+/Li+ cation mixing. This method provides a new strategy for the surface modification of nickel-rich layered cathode materials.