Flower-like NiCo 2 S 4 nanosheets with high electrochemical performance for sodium-ion batteries
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Flower-like NiCo2S4 nanosheets with high electrochemical performance for sodium-ion batteries Yongqiang Miao1, Xiaosen Zhao1, Xin Wang1, Chenhui Ma1, Lu Cheng1, Gang Chen1, Huijuan Yue2 (), Lei Wang3, and Dong Zhang1 () 1
Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin Key Engineering Laboratory of New Energy Materials and Technologies, College of Physics, Jilin University, Changchun 130012, China 2 State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China 3 Key Laboratory of Eco-Chemical Engineering (Ministry of Education), College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 26 December 2019 / Revised: 26 June 2020 / Accepted: 2 July 2020
ABSTRACT A three-dimensional flower-like NiCo2S4 formed by two-dimensional nanosheets is synthesized by a facile hydrothermal method and utilized as the anode for sodium-ion batteries. Studies have shown that materials can achieve the best performance under the ether-based electrolyte system with voltage ranging from 0.3 to 3 V, which could effectively avoid the dissolution of polysulfides and over-discharge of the material. Here, sodium storage mechanism and charge compensation behaviors of this ternary metal sulfide are comprehensively investigated by ex situ X-ray diffraction. Moreover, ex situ Raman spectra, ex situ X-ray photoelectron spectroscopy and transmission electron microscopy measurements are used to related tests for the first time. Additionally, quantitative kinetic analysis unravels that sodium storage partially depends on the pseudocapacitance mechanism, resulting in good specific capacity and excellent rate performance. The initial discharge capacity is as high as 748 mAh·g−1 at a current density of 0.1 A·g−1 with the initial coulomb efficiency of 94%, and the capacity can still maintain at 580 mAh·g−1 with the Coulomb efficiency close to 100% after following 50 cycles. Moreover, by the long cycle test at a high current density of 2 A·g−1, the capacity can still reach at 376 mAh·g−1 after over 500 cycles.
KEYWORDS NiCo2S4, sodium-ion batteries, anode materials, sodium storage mechanism, pseudocapacitance
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Introduction
Nowadays, with the increasingly serious environmental problems and growing energy demand, sodium-ion batteries (SIBs) have become reasonable substitutes for lithium-ion batteries (LIBs) in large-scale grid storage applications due to their abundant resources and low cost of sodium-containing precursors. With the encouraging developments in SIBs, lots of problems in this system are still expected to be solved [1, 2]. On one side, excellent electrochemical properties can be taken through the use of cathode materials for SIBs, such as layered transition metal oxides and polyanionic compounds [3, 4]. However, on the flip side, anode materials, the important co
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