Insights into the structural degradation and dual modification to enhance structural and cycling stability in LiNi0.8Co0.1Mn0.1O2

LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), as a Ni-rich layered cathode, has the advantages of high specific capacity, low cost and environmental friendliness, and is considered one of the most promising cathode materials for high energy density lithium ion batteries . However, the higher nickel content will reduce the cyclic stability of the cathode material. Additionally, the mechanical stress caused by the anisotropic volume change will lead to the formation of micro-cracks in the material, resulting in side reactions between electrode materials and electrolyte. Herein, the microstructure evolution of NCM811 during the charging process is investigated using in-situ transmission electron microscopy (TEM). The electrochemical performance of NCM811 is then improved by doping Nb using the solid phase sintering method. Afterwards, the Nb-doped NCM811 composite electrode is coated with Al 2 O 3 by atomic layer deposition method. This double modification strategy can maintain the structural stability in bulk phase, and prevent the direct contact of the NCM811 particle surface with electrolyte to inhibit the side reaction. The dual modified sample exhibits superior cyclability, retaining 95.0 % of its capacity after 200 cycles at 1C, and demonstrates better rate capability compared to pristine NCM811. This study holds significant value in guiding the modifications and further application of NCM811. • The microstructure evolution of NCM811 was investigated using in-situ TEM. • The electrochemical performance of NCM811 was improved by dual modification. • The modified samples maintain the structural stability and inhibit the side reaction. • The dual modified sample exhibits superior cyclability and better rate capability.