title: Mechanically and chemically robust sandwich-structured C@Si@C nanotube array Li-ion battery anodes.
abstract: Stability and high energy densities are essential qualities for emerging battery electrodes. Because of its high specific capacity, silicon has been considered a promising anode candidate. However, the several-fold volume changes during lithiation and delithiation leads to fractures and continuous formation of an unstable solid-electrolyte interphase (SEI) layer, resulting in rapid capacity decay. Here, we present a carbon-silicon-carbon (C@Si@C) nanotube sandwich structure that addresses the mechanical and chemical stability issues commonly associated with Si anodes. The C@Si@C nanotube array exhibits a capacity of ∼2200 mAh g(-1) (∼750 mAh cm(-3)), which significantly exceeds that of a commercial graphite anode, and a nearly constant Coulombic efficiency of ∼98% over 60 cycles. In addition, the C@Si@C nanotube array gives much better capacity and structure stability compared to the Si nanotubes without carbon coatings, the ZnO@C@Si@C nanorods, a Si thin film on Ni foam, and C@Si and Si@C nanotubes. In situ SEM during cycling shows that the tubes expand both inward and outward upon lithiation, as well as elongate, and then revert back to their initial size and shape after delithiation, suggesting stability during volume changes. The mechanical modeling indicates the overall plastic strain in a nanotube is much less than in a nanorod, which may significantly reduce low-cycle fatigue. The sandwich-structured nanotube design is quite general, and may serve as a guide for many emerging anode and cathode systems.
authors: Department of Materials Science and Engineering, ‡Department of Mechanical Sciences and Engineering, §Frederick Seitz Materials Research Laboratory, ⊥Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors: Jinyun
authors: J
authors: Liu
authors: Nan
authors: N
authors: Li
authors: Matthew D
authors: MD
authors: Goodman
authors: Hui Gang
authors: HG
authors: Zhang
authors: Eric S
authors: ES
authors: Epstein
authors: Bo
authors: B
authors: Huang
authors: Zeng
authors: Z
authors: Pan
authors: Jinwoo
authors: J
authors: Kim
authors: Jun Hee
authors: JH
authors: Choi
authors: Xingjiu
authors: X
authors: Huang
authors: Jinhuai
authors: J
authors: Liu
authors: K Jimmy
authors: KJ
authors: Hsia
authors: Shen J
authors: SJ
authors: Dillon
authors: Paul V
authors: PV
authors: Braun
keywords: Li-ion battery; capacity; nanotube; plastic strain; silicon anode