Issue 26, 2013

Predictions of particle size and lattice diffusion pathway requirements for sodium-ion anodes using η-Cu6Sn5 thin films as a model system

Abstract

Geometrically well-defined Cu6Sn5 thin films were used as a model system to estimate the diffusion depth and diffusion pathway requirements of Na ions in alloy anodes. Cu6Sn5 anodes have an initial reversible capacity towards Li of 545 mA h g−1 (Li3.96Sn or 19.8 Li/Cu6Sn5), close to the theoretical 586 mA h g−1 (Li4.26Sn), and a very low initial irreversible capacity of 1.6 Li/Cu6Sn5 (Li0.32Sn). In contrast, the reaction with Na is limited with a reversible capacity of 160 mA h g−1 compared to the expected 516 mA h g−1 (Na3.75Sn). X-ray diffraction and 119Sn-Mössbauer spectroscopy measurements show that this limited capacity likely results from the restricted diffusion of Na into the anode nanoparticles and not the formation of a low Na-content phase. Moreover, our results suggest that the η-Cu6Sn5 alloy should have optimized particle sizes of nearly 10 nm diameter to increase the Na capacity significantly. An alternative system consisting of a two-phase mixture of Cu6Sn5 and Sn of nominal composition ‘Cu6Sn10’ has been studied and is able to deliver a larger initial reversible storage capacity of up to 400 mA h g−1. Finally, we have demonstrated that the presence of Cu in Cu6Sn5 and ‘Cu6Sn10’ suppresses the anomalous electrolyte decomposition normally observed for pure Sn.

Graphical abstract: Predictions of particle size and lattice diffusion pathway requirements for sodium-ion anodes using η-Cu6Sn5 thin films as a model system

Supplementary files

Article information

Article type
Paper
Submitted
18 Apr 2013
Accepted
24 Apr 2013
First published
02 May 2013

Phys. Chem. Chem. Phys., 2013,15, 10885-10894

Predictions of particle size and lattice diffusion pathway requirements for sodium-ion anodes using η-Cu6Sn5 thin films as a model system

L. Baggetto, J. Jumas, J. Górka, C. A. Bridges and G. M. Veith, Phys. Chem. Chem. Phys., 2013, 15, 10885 DOI: 10.1039/C3CP51657A

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