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Garcia-Gil et al – High Aspect-ratio Germanium-Tin Alloy Nanowires: Potential as Highly Efficient Li-Ion Battery Anodes, Advanced Materials Interfaces, 2022, 9, 2201170

Adrià Garcia-Gil1,2, Subhajit Biswas1,2,* David McNulty3, Ahin Roy4, Kevin M. Ryan3, Valeria Nicolosi4, and Justin D. Holmes1,2

1School of Chemistry & Tyndall National Institute, University College Cork,  Cork T12 YN60, Ireland.
2AMBER Centre, Environmental Research Institute, University College Cork, Cork T23 XE10, Ireland.
3Bernal Institute & Chemical Sciences Department, University of Limerick, Limerick V94 T9PX, Ireland
4School of Chemistry and CRANN Trinity College Dublin, Dublin 2, Dublin T23 XE10, Ireland.
Corresponding author: Subhajit Biswas (s.biswas@ucc.ie)

Received: May 26, 2022, Revised: July 4, 2022, Published Online: September 7, 2022
Link: https://onlinelibrary.wiley.com/doi/epdf/10.1002/admi.202201170

Here, the fabrication of a high aspect ratio (>440) Ge1−xSnx nanowires with super-thin (≈9 nm) diameter, much below the Bohr radius, using a simple solvothermal-like growth method under supercritical toluene conditions at a reaction temperature of 440 °C is reported. Ge1−xSnx nanowires are grown with varying amounts of Sn in Ge lattice, between 3.1 to 10.2 at%. The growth of the Ge1−xSnx alloy nanowires is achieved without any additional catalysts, and directly on current collector substrates (titanium) for application as Li-ion battery anodes. The electrochemical performance of the binder-free  Ge1−xSnx nanowires as an anode material for Li-ion batteries is investigated via galvanostatic cycling and detailed analysis of differential capacity plots. The dimensions of the nanowires, and the amount of Sn in Ge, are critical to achieving a high specific capacity and capacity retention. Ge1−xSnx nanowires with the highest aspect ratios and with the lowest Sn content (3.1 at%) demonstrate exceptional capacity retention of ≈90 % and 86 % from the 10th to the 100th and 150th cycles respectively, while maintaining a very high specific capacity value of 1176 and 1127 mAh g−1 after the 100 and 150 cycles respectively.

Illustration of the two proposed nanowire growth mechanisms. a) Corresponds to the nanowires (3.1 at% Sn incorporation) grown from an initial solution of 95:5 (Ge:Sn precursors) which generated Ge nanoparticle seed. b) Corresponds to the nanowires (7.9 and 10.1 at% Sn incorporation) grown from initial solutions of 90:10 and 85:15 (Ge:Sn precursors) respectively generating Sn seeds.