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Ahad et al. – Amorphization driven Na-alloying in SixGe1−x alloy nanowires for Na-ion batteries – J. Mater. Chem. A, 2021, 9, 20626-20634.

Syed Abdul Ahad, Seamus Kilian, Maria Zubair, Vasily A Lebedev, Karrina McNamara, Kevin M Ryan, Tadhg Kennedy, Hugh Geaney
Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick V94 T9PX, Ireland. E-mail: Hugh.Geaney@ul.ie
Received 4th May 2021 , Accepted 6th August 2021
DOI: 10.1039/D1TA03741B
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Here we report the use of 1D SixGe1−x (x = 0.25, 0.5, 0.75) alloy nanowires (NWs) as anode materials for Na-ion batteries (NIBs). The strategy involves the synthesis of crystalline SixGe1−x NWs via the solution–liquid–solid (SLS) mechanism, followed by amorphization to activate the material for Na-ion cycling within a NIB. This study demonstrates the successful activation of SixGe1−x amorphous NW alloys, with a-Si0.5Ge0.5 delivering 250 mA h g−1 as compared to a-Ge NWs delivering only 107 mA h g−1 after 100 cycles. Also, amorphization proved to be a critical step, since crystalline NWs failed to activate in NIBs. However, Si NWs performed poorly during Na-ion cycling even after amorphization, and this behavior was explained by poor comparative Na-ion diffusivity. Further investigations on the impact of the relative content of Ge within the amorphized SixGe1−x NWs, Na-ion diffusivity and electrode degradation during cycling were also performed. Notably, the incorporation of Ge in the a-SixGe1−x alloy boosted Na ion diffusivity in the amorphized alloy, resulting in improved cycling performance and rate capability as compared to parent a-Si and a-Ge NWs.