Supersaturated bridge-sulfur and vanadium co-doped M0S 2 nanosheet arrays with enhanced sodium storage capability
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Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Engineering Research Center of Hierarchical Nanomaterials, School of Materials Science and Engineering, East China University of Science & Technology, Shanghai 200237, China 2 Christopher Ingold Laboratory, Department of Chemistry, University College London, 20 Gordon Street, London WC1H0AJ, U.K. § Yuru Dong and Zhengju Zhu contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 23 June 2020 / Revised: 04 August 2020 / Accepted: 07 August 2020
ABSTRACT The low specific capacity and sluggish electrochemical reaction kinetics greatly block the development of sodium-ion batteries (SIBs). New high-performance electrode materials will enhance development and are urgently required for SIBs. Herein, we report the preparation of supersaturated bridge-sulfur and vanadium co-doped MoS2 nanosheet arrays on carbon cloth (denoted as V-MoS2+x/CC). The bridge-sulfur in MoS2 has been created as a new active site for greater Na+ storage. The vanadium doping increases the density of carriers and facilitates accelerated electron transfer. The synergistic dual-doping effects endow the V-MoS2+x/CC anodes with high sodium storage performance. The optimized V-MoS2.49/CC gives superhigh capacities of 370 and 214 mAh·g–1 at 0.1 and 10 A·g–1 within 0.4–3.0 V, respectively. After cycling 3,000 times at 2 A·g–1, almost 83% of the reversible capacity is maintained. The findings indicate that the electrochemical performances of metal sulfides can be further improved by edge-engineering and lattice-doping co-modification concept.
KEYWORDS MoS2, bridge-sulfur, high specific capacity, sodium-ion battery, cycle life
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Introduction
Rechargeable sodium ion batteries (SIBs) as replacement candidates for lithium ion batteries (LIBs) have been intensively investigated in view of abundant sodium resource, high economic benefits, and sodium-free dendrites [1–4]. However, owing to the weaker binding to the substrate and larger radius of Na+ compared to Li+, commercial graphite for lithium-ion batteries exhibits obvious thermodynamic and kinetic deficiencies for sodium storage [5–7]. Therefore, exploiting new highperformance electrode materials is pivotal in promoting practical application of SIBs. In recent years, two-dimensional (2D) molybdenum disulfide (MoS2) has been considered as a promising anode material for SIBs due to its large interlayer distance (0.62 nm), weak van der Waals forces and four electrons conversion reactions enabling facile Na+ insertion/extraction and contributing to a high theoretical specific capacity (e.g. 670 mAh·g−1) [8–12]. Nevertheless, the conversion reaction below 0.4 V is usually accompanied by non-negligible volume changes and the dissolution of intermediate polysulfides, consequentially leading to structure pulverization and rapid capacity decay [13, 14]. Although manipulating the cut-off voltage to guarantee the intercalation reaction above 0.4 V is able to improve the
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