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Facile synthesis of Co9S8@NC anode with enhanced sodium storage and long cycling life Mingtao Duan1, Yanshuang Meng1,2,*

1 2

, Jian Hu1, Guixiang Zhao1, and Fuliang Zhu1,2

School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China

Received: 17 May 2020

ABSTRACT

Accepted: 3 November 2020

Transition metal sulfides (TMSs) are presently under extensive research and have been regarded as the prospective anode candidates for sodium ion batteries (SIBs). However, the poor intrinsic electrical conductivity and huge volume expansion of metal sulfides electrodes during the discharge-charge process eventually cause pulverization of active materials and quick capacity decay, which severely limit their further practical application. In this study, ultrafine Co9S8 nanoparticles embedded in N-doped carbon layer (Co9S8@NC) were facilely synthesized via a simple one-step solid phase calcination method with glucose as the carbon source and thiourea served as N, S-containing precursor. The Co9S8@NC hybrid with small nanoparticle size could aid in the quick penetration of the electrolyte and shorten the pathway of Na ions diffusion; Meanwhile, the N-doped disordered carbon layer could maintain structural integrity and favor the electron transport of the nanocomposite during the electrochemical reaction. The Co9S8@NC composite is firstly investigated as anode for SIBs. They exhibit a satisfied discharge/charge specific capacity of 285.3/276.3 mAh g-1 after 160 cycles at 170 mA g-1, and its discharge/charge specific capacity is capable to maintain 160.8/158.5 mAh g-1 even after 1000 cycles at 1000 mA g-1. Further kinetics analyses based on CV demonstrate that the partial pseudocapacitive behaviors partially accounts for the remarkable Na storage performances.

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Springer Science+Business

Media, LLC, part of Springer Nature 2020

1 Introduction Although lithium-ion batteries (LIBs) have occupied the leading position in portable electronics and green electric vehicles during the past decades, the future

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https://doi.org/10.1007/s10854-020-04826-1

large-scale commercial applications and sustainable development of LIBs are severely restricted by the limitation of lithium resource and the growing cost of lithium salt [1–4]. In recent years, sodium-ion batteries (SIBs) have attracted extensive attentions as one

J Mater Sci: Mater Electron

potential alternatives to conventional LIBs due to their low cost of sodium (Na) precursors, natural abundance and similar intercalation chemistry as LIBs [5, 6]. Note that the electrode materials are the key factor to determine the properties of SIBs. To date, a wide range of electrode materials have been explored to reach high-performance SIBs, which includes insertion-type materials TiO2 [7, 8], graphite [9], conversion-type materials Ni3S2 [10], Fe2O3 [11] as