A lithiation/delithiation mechanism of monodispersed MSn5 (M = Fe, Co and FeCo) nanospheres

Fengxia Xin; Xiaoliang Wang; Jianming Bai; Wen Wen; Huajun Tian; Chunsheng Wang; Weiqiang Han

doi:10.1039/C4TA06960A

A lithiation/delithiation mechanism of monodispersed MSn₅ (M = Fe, Co and FeCo) nanospheres†

Fengxia Xin,^a Xiaoliang Wang,‡^a Jianming Bai,^b Wen Wen,^c Huajun Tian,^a Chunsheng Wang*^d and Weiqiang Han*^a

* Corresponding authors

^a Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, P. R. China
E-mail: hanweiqiang@nimte.ac.cn

^b National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA

^c Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, P. R. China

^d Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA
E-mail: cswang@umd.edu

Abstract

A designed Sn based alloy host as a higher capacity and longer cycle life next generation lithium-ion battery, consisting of monodisperse nanospheres of intermetallic MSn₅ (M = Fe, Co and FeCo) phases was synthesized by a nanocrystal conversion chemistry method using preformed Sn nanospheres as templates. The same crystal structure, identical particle surface morphology and the similar particle size distribution (30–50 nm) of these intermetallic MSn₅ (M = Fe, Co and FeCo) phases are ideal for comparison of the electrochemical performance, reaction mechanism, thermodynamics and kinetics during lithiation/delithiation. Importantly, MSn₅ (M = Fe, Co and FeCo) phases with defect structures Fe_0.74Sn₅, Co_0.83Sn₅ and Fe_0.35Co_0.35Sn₅, exhibit the highest theoretical capacity of >917 mA h g⁻¹ among the reported M–Sn (M is electro-chemically inactive) based intermetallic anodes. The ex situ XRD and XAFS illustrate the complete reversibility of MSn₅ (M = Fe, Co and FeCo) phases during lithium insertion/extraction for the first cycle. The Fe_0.35Co_0.35Sn₅ anode can take advantage of both high capacity of Fe_0.74Sn₅ and long cycle life of Co_0.83Sn₅, providing 736 mA h g⁻¹ and maintaining 92.7% of initial capacity after 100 cycles with an average capacity loss of only 0.07% per cycle. The excellent electrochemical performance of the Fe_0.5Co_0.5Sn₅ system is attributed to higher reversibility, lower reaction resistance. This work provides a novel insight toward designing and exploring an optimal Sn based alloy anode for next generation Li-ion batteries.

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Article information

DOI: https://doi.org/10.1039/C4TA06960A
Article type: Paper
Submitted: 17 Dec 2014
Accepted: 15 Feb 2015
First published: 17 Feb 2015

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J. Mater. Chem. A, 2015,3, 7170-7178

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A lithiation/delithiation mechanism of monodispersed MSn₅ (M = Fe, Co and FeCo) nanospheres

F. Xin, X. Wang, J. Bai, W. Wen, H. Tian, C. Wang and W. Han, J. Mater. Chem. A, 2015, 3, 7170 DOI: 10.1039/C4TA06960A

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Journal of Materials Chemistry A