Mitigating storage-induced degradation of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode material by surface tuning with phosphate

Abstract The Ni-rich LiNi0.8Co0.1Mn0.1O2 layered oxide (NCM811) is attracting considerable attention as a high-capacity cathode material for rechargeable Li-ion batteries. However, due to its inherent structural/chemical/electrochemical instability, NCM811 with high Ni content suffers from significant performance degradation upon storage even in ambient atmospheres as well as during charge–discharge cycling. Herein, we demonstrate a simple but effective surface-tuning approach to mitigate storage-induced degradation of NCM811, which is based on the conversion of undesirable Li residues to a protective Li3PO4 nanolayer via phosphate treatment. The accelerated storage stability test shows that phosphate-modified NCM811 exhibits remarkably improved electrochemical performance (capacity, cycle life, and rate capability) over the pristine one after being stored under harsh environmental conditions. A combined analytical study indicates that surface tuning through phosphate treatment enhances the storage stability of NCM811 by eliminating impurity-forming Li residues and producing a Li3PO4 nanolayer that inhibits parasitic reactions at the electrode–electrolyte interface. Furthermore, Li3PO4 provides an effective barrier to H2O and CO2 infiltration into the particle agglomerates, thereby suppressing the loss of particle integrity.