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

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-08, Vol.470, p.144209, Article 144209
• Main Authors: Lee, Sanghyun, Hwang, Jeonguk, Park, Changyong, Ahn, Suhyun, Do, Kwanghyun, Kim, Sungwook, Ahn, Heejoon
• Format: Article
• Language: English
• Subjects: Electrostatic attraction; Lithium-ion batteries; Molybdenum disulfide nanosheets; Nanosheet coating; Ni-rich layered cathode
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2023.144209

Surface coating is an efficient approach to improve the electrochemical performance of Ni-rich NCM cathode materials for lithium-ion batteries, but most of the previously reported coating methods have complex procedures and require a time- and energy-consuming post-calcination process. We propose a novel method for coating the surface of Ni-rich NCM particles using chemically exfoliated and polyethyleneimine-modified 1T-MoS2 nanosheets through a simple mixing method. [Display omitted] •The ceMoS2-PEI nanosheet-coated Ni-rich NCM cathode material was synthesized.•This is the first metallic 1T-MoS2 nanosheet coating report on Ni-rich NCM surfaces.•The ceMoS2-PEI layer protected the Ni-rich NCM and improved the Li+/e- transfer kinetics.•The NCM/ceMoS2-PEI electrode exhibited excellent cycle stability and high rate capability.•Post-cycle analysis proved that various degradation mechanisms were effectively suppressed. 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 effectivel