Two-Dimensional MoS₂ Nanosheets Derived from Cathodic Exfoliation for Lithium Storage Applications

The preparation of 2H-phase MoS₂ thin nanosheets by electrochemical delamination remains a challenge, despite numerous efforts in this direction. In this work, by choosing appropriate intercalating cations for cathodic delamination, the insertion process was facilitated, leading to a higher degree of exfoliation while maintaining the original 2H-phase of the starting bulk MoS₂ material. Specifically, trimethylalkylammonium cations were tested as electrolytes, outperforming their bulkier tetraalkylammonium counterparts, which have been the focus of past studies. The performance of novel electrochemically derived 2H-phase MoS₂ nanosheets as electrode material for electrochemical energy storage in lithium-ion batteries was investigated. The lower thickness and thus higher flexibility of cathodically exfoliated MoS₂ promoted better electrochemical performance compared to liquid-phase and ultrasonically assisted exfoliated MoS₂, both in terms of capacity (447 vs. 371 mA·h·g^-1 at 0.2 A·g^-1) and rate capability (30% vs. 8% capacity retained when the current density was increased from 0.2 A·g^-1 to 5 A·g^-1), as well as cycle life (44% vs. 17% capacity retention at 0.2 A·g^-1 after 580 cycles). Overall, the present work provides a convenient route for obtaining MoS₂ thin nanosheets for their advantageous use as anode material for lithium storage.