Pore collapse and regrowth in silicon electrodes for rechargeable batteries

S. C. DeCaluwe; B. M. Dhar; L. Huang; Y. He; K. Yang; J. P. Owejan; Y. Zhao; A. A. Talin; J. A. Dura; H. Wang

doi:10.1039/C4CP06017B

Pore collapse and regrowth in silicon electrodes for rechargeable batteries†

S. C. DeCaluwe,‡^abc B. M. Dhar,‡^de L. Huang,^d Y. He,^df K. Yang,^d J. P. Owejan,^g Y. Zhao,^f A. A. Talin,^hi J. A. Dura*^b and H. Wang*^cde

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* Corresponding authors

^a Department of Mechanical Engineering, Colorado School of Mines, Golden, CO, USA

^b Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
E-mail: jdura@nist.gov

^c Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA
E-mail: wangh@umd.edu

^d Institute for Materials Research and Dept. of Mechanical Engineering, State University of New York, Binghamton, NY, USA

^e Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, USA

^f Department of Physics and Astronomy, University of Georgia, Athens, GA, USA

^g Department of Mechanical and Electrical Engineering Technology, State University of New York, Alfred, NY, USA

^h Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD, USA

ⁱ Sandia National Laboratories, Livermore, CA, USA

Abstract

Structure and composition of an 11 nm thick amorphous silicon (a-Si) thin film anode, capped with 4 nm of alumina are measured, in operando, by neutron reflectivity (NR) and electrochemical impedance spectroscopy in a lithium half-cell. NR data are analyzed to quantify the a-Si thickness and composition at various states of charge over six cycles. The a-Si anode expands and contracts upon lithiation and delithiation, respectively, while maintaining its integrity and low interfacial roughness (≤1.6 nm) throughout the cycling. The apparently non-linear expansion of the a-Si layer volume versus lithium content agrees with previous thin-film a-Si anode studies. However, a proposed pore collapse and regrowth (PCRG) mechanism establishes that the solid domains in the porous Li_xSi film expand linearly with Li content at 8.48 cm³ mol⁻¹ Li, similar to crystalline Si. In the PCRG model, porosity is first consumed by expansion of solid domains upon lithiation, after which the film as a whole expands. Porosity is reestablished at 5–28% upon delithiation. Data show that the alumina protective layer on the a-Si film functions as an effective artificial solid electrolyte interphase (SEI), maintaining its structural integrity, low interfacial roughness, and relatively small transport resistance. No additional spontaneously-formed SEI is observed in this study.

Physical Chemistry Chemical Physics

Pore collapse and regrowth in silicon electrodes for rechargeable batteries†

Abstract

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Pore collapse and regrowth in silicon electrodes for rechargeable batteries

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