Efficient and scalable encapsulation process of highly conductive 1T-MoS2 nanosheets on Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode materials for high-performance lithium-ion batteries

Abstract

Ni-rich LiNi1-x-yCoxMnyO2 (NCM) is an attractive cathode material that can meet the growing global demand of the Lithium-ion battery market owing to its high energy density and low cost. However, it still suffers from cyclic and thermal instability due to several issues, such as structural deterioration and excessive cathode electrolyte interface (CEI) layer formation arising from side reactions occurring at the NCM particle surface. In this study, molybdenum disulfide (MoS2) nanosheets with a metallic 1T phase are synthesized by chemical exfoliation, functionalized with polyethyleneimine (PEI), and uniformly coated on the surface of Ni-rich NCM particles through electrostatic interactions. As a result, the ceMoS2-PEI layer effectively alleviates the electrochemical performance degradation of NCM caused by irreversible phase transitions, microcrack formation, transition metal dissolution, and thick CEI layer formation by suppressing side reactions due to direct contact with the organic electrolyte or hydrofluoric acid on the surface of NCM. In addition, the ceMoS2-PEI layer provides a sufficient transport pathway for charge transfer and Li+ ion diffusion, thereby mitigating electrode polarization and impedance increase. Consequently, NCM/ceMoS2-PEI electrodes exhibit a high discharge capacity of 150.6 mAh g−1 at 5C and outstanding capacity retention of 96.9 % after 100 cycles at 1C. Moreover, further cycle tests in harsh environments, such as high mass loading and operating temperature, demonstrate that the ceMoS2-PEI layer coating more effectively improves the structural and thermal stability of the Ni-rich NCM in harsh environments.