Preparation of ultra-thin layer MoS2/SnS/rGO electrode materials using ionic liquids
Metal sulfides (MSs) are considered as a promising anode material for sodium ion batteries (SIBs) due to their good reversibility, large theoretical capacity and high electrochemical activity. Graphene with sp2-hybridized carbon monolayer two-dimensional structure can greatly improve the electrochemical performance of MSs by enhancing the electron capacity, and is widely studied as a conductive additive or buffer layer for MSs. Liquid-phase growth of MSs on graphene oxide (GO) is one of the effective methods to obtain MSs/rGO composites. However, the high surface tension of water and the increase of surface energy of aqueous solvent during deoxidation can cause uncontrolled accumulation and aggregation of graphene layers during the preparation process. Therefore, a low surface energy (LSE) system for the preparation of graphene MSs composites is urgently needed to integrate the structural advantages of graphene and its related materials
The group of Professor Xinglong Wu at Northeast Normal University has proposed a low surface energy method to prepare ultrathin MoS2/SnS/rGO ternary hybrid nanoflakes with the help of ionic liquids capable of storing sodium. The ionic liquid of 1-Butyl-3-methylimidazolium dihydrogen phosphate ([Bmim]H2PO4) with low surface tension not only reduces the surface tension of the solvent, but also promotes the exfoliation of graphene layers, which facilitates the uniform growth of MSs on the reduced graphene layers and plays an important role in acting as a bridging agent.
As shown in Figure 2 below, the researchers used atomic force microscopy to probe the size and thickness of the ternary hybrids. The graphene layers in the composites obtained by the ordinary hydrothermal method would undergo severe aggregation; whereas the MoS2/SnS/rGO hybrids prepared by adding ionic liquids have a very smooth surface structure, which basically avoids the aggregation and accumulation of graphene layers. It can be seen that the addition of [Bmim]H2PO4 ionic liquid can effectively reduce the surface tension, which is beneficial to the preparation of ultrathin layered hybrid composites.
Figure 2. (b) AFM images of (b) MoS2/SnS/rGO and (c) H-MoS2/SnS/rGO height and width distributions, (d) SEM images, (e) TEM images
Subsequently, the researchers used Na3V2(PO4)2O2F as the cathode material to form a full cell to evaluate the practical application of MoS2/SnS/rGO. The cycling performance of the full cell evaluated at 1 A g-1 showed that a current of up to 366.1 mAh g-1 could be maintained after 50 cycles, with a capacity retention of 77.2%. The above outstanding electrochemical performance of the full cell confirms the great potential of ultrathin nanosheets MoS2/SnS/rGO as anode candidates for practical SIBs full cells
Figure 2. (a) Schematic diagram of MoS2/SnS/rGO//Na3V2(PO4)2O2F cell, (b) voltage distribution of Na3V2(PO4)2O2F half-cell, MoS2/SnS/rGO//Na3V2(PO4)2O2F full-cell and MoS2/SnS/rGO half-cell.(c) multiplicative performance, (d) cycling performance
In conclusion, this low surface energy strategy proposed in the paper uses ionic liquids to fabricate bimetallic sulfides MoS2/SnS/rGO anchored on the heterogeneous structure of graphene layers. The tight bond between the metal sulfide and the rGO matrix ensures rapid electron transfer while guaranteeing structural integrity, which leads to excellent multiplicative performance and long-cycle stability. The proposed low surface energy strategy provides a new solution to construct graphene-based or graphene-related materials for high-performance energy storage devices.
Link to original article: https://www.sciencedirect.com/science/article/pii/S1385894721057685
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Author: Yang Yan, Pei-Quan Li, Zhen-Yi Gu, Wen Liu, Jun-Ming Cao, and Xing-Long Wu
DOI: 10.1016/j.cej.2021.134195
Even for the new substance mentioned in the article.1-Butyl-3-methylimidazolium dihydrogen phosphate ([Bmim]H2PO4), our laboratory can also produce it.
if you are interested in it, please contact me and I will send you the catalog of ionic liquids.
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Contact Person: Leon Li