High Performance Tin-coated Vertically Aligned Carbon Nanofiber Array Anode for Lithium-ion Batteries
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.520
High Performance Tin-coated Vertically Aligned Carbon Nanofiber Array Anode for Lithium-ion Batteries Gaind P. Pandey1, Kobi Jones1, Emery Brown2, Jun Li2 and Lamartine Meda1
1
Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125
2
Department of Chemistry, Kansas State University, Manhattan, KS 66506
ABSTRACT
This study reports a high-performance tin (Sn)-coated vertically aligned carbon nanofiber array anode for lithium-ion batteries. The array electrodes have been prepared by coaxial sputter-coating of tin (Sn) shells on vertically aligned carbon nanofiber (VACNF) cores. The robust brush-like highly conductive VACNFs effectively connect high-capacity Sn shells for lithium-ion storage. A high specific capacity of 815 mAh g-1 of Sn was obtained at C/20 rate, reaching toward the maximum value of Sn. However, the electrode shows poor cycling performance with conventional LiPF 6 based organic electrolyte. The addition of fluoroethylene carbonate (FEC) improve the performance significantly and the Sn-coated VACNFs anode shows stable cycling performance. The Sn-coated VACNF array anodes exhibit outstanding capacity retention in the half-cell tests with electrolyte containing 10 wt.% FEC and could deliver a reversible capacity of 480 mAh g-1 after 50 cycles at C/3 rate. INTRODUCTION To meet the increasing demands of high-energy density lithium-ion batteries (LIBs) for electric vehicles and energy storage systems several higher capacity anode materials such as lithium (Li), silicon (Si), germanium (Ge) and tin (Sn) have been studied to replace the graphite currently used in the commercial LIBs [1-3]. Among Lialloying anodes (Si, Ge, Sn etc.), Sn recently has been considered as a promising anode material because of the high theoretical specific capacity of 994 mAh g -1 for its alloy
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Li22Sn5 [4, 5]. Although its abundant nature makes Sn an attractive anode material, the application of Sn as an anode is still far from realization. One of the critical issues is the huge volume expansion (>300%) and aggregation of Sn nanoparticles during lithium alloying (insertion) and dealloying (extraction) processes and, hence induces severe anisotropic stress, leading to particle pulverization, solid electrolyte interphase (SEI) destabilization, and consequently fast capacity fading in the initial cycles [3]. Various nanostructured Sn materials including nanoparticles, nanowires, and nano-sheets have been developed to reduce the internal stress and to make use of their large specific surface area and short Li+ diffusion length in solids [3-5]. Various forms of carbon materials have also been incorporated with nanostructured Sn to form composite anode materials. Here we demonstrate the hybrid c
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