The fabrication of hierarchical MoO2@MoS2/rGO composite as high reversible anode material for lithium ion batteries

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.

Boosting potassium-storage performance via confining highly dispersed molybdenum dioxide nanoparticles within N-doped porous carbon nano-octahedrons

The development of durable and stable metal oxide anodes for potassium ion batteries (PIBs) has been hampered by poor electrochemical performance and ambiguous reaction mechanisms. Herein, we design and fabricate molybdenum dioxide (MoO₂)@N-doped porous carbon (NPC) nano-octahedrons through metal-organic frameworks derived strategy for PIBs with MoO₂ nanoparticles confined within NPC nano-octahedrons. Benefiting from the synergistic effect of nanoparticle level of MoO₂ and N-doped carbon porous nano-octahedrons, the MoO₂@NPC electrode exhibits superior electron/ion transport kinetics, excellent structural integrity, and impressive potassium-ion storage performance with enhanced cyclic stability and high-rate capability. The density functional theory calculations and experiment test proved that MoO₂@NPC has a higher affinity of potassium and higher conductivity than MoO₂ and N-doped carbon electrodes. Kinetics analysis revealed that surface pseudocapacitive contributions are greatly enhanced for MoO₂@NPC nano-octahedrons. In-situ and ex-situ analysis confirmed an intercalation reaction mechanism of MoO₂@NPC for potassium ion storage. Furthermore, the assembled MoO₂@NPC//perylenetetracarboxylic dianhydride (PTCDA) full cell exhibits good cycling stability with 72.6 mAh g^-1 retained at 100 mA g^-1 over 200 cycles. Therefore, this work present here not only evidences an effective and viable structural engineering strategy for enhancing the electrochemical behavior of MoO₂ material in PIBs, but also gives a comprehensive insight of kinetic and mechanism for potassium ion interaction with metal oxide.