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Ahad et al – Lithiophilic Nanowire Guided Li Deposition in Li Metal Batteries – Small (2022): 2205142

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Syed Abdul Ahad1,2, Shayon Bhattacharya1,3, Seamus Kilian1,2, Michela Ottaviani1,2, Kevin M. Ryan1,2, Tadhg Kennedy1,2, Damien Thompson1,3, and Hugh Geaney*,1,2

1Bernal Institute, University of Limerick, Limerick V94 T9PX, Ireland
2Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Ireland
3Department of Physics, University of Limerick, Limerick V94 T9PX, Ireland
Corresponding Author: H. Geaney (hugh.geaney@ul.ie)

Received: August 22, 2022 Revised: November 3, 2022 Published online: November 18, 2022
Link to Paper: https://onlinelibrary.wiley.com/doi/epdf/10.1002/smll.202205142

Abstract

Lithium (Li) metal batteries (LMBs) provide superior energy densities far beyond current Li-ion batteries (LIBs) but practical applications are hindered by uncontrolled dendrite formation and the build-up of dead Li in “hostless” Li metal anodes. To circumvent these issues, we created a 3D framework of a carbon paper (CP) substrate decorated with lithiophilic nanowires (silicon (Si), germanium (Ge), and SiGe alloy NWs) that provides a robust host for efficient stripping/plating of Li metal. The lithiophilic Li22Si5, Li22(Si0.5Ge0.5)5, and Li22Ge5 formed during rapid Li melt infiltration prevented the formation of dead Li and dendrites. Li22Ge5/Li covered CP hosts delivered the best performance, with the lowest overpotentials of 40 mV (three times lower than pristine Li) when cycled at 1 mA cm−2/1 mAh cm−2 for 1000 h and at 3 mA cm−2/3 mAh cm−2 for 500 h. Ex situ analysis confirmed the ability of the lithiophilic Li22Ge5 decorated samples to facilitate uniform Li deposition. When paired with sulfur, LiFePO4, and NMC811 cathodes, the CP-LiGe/Li anodes delivered 200 cycles with 82%, 93%, and 90% capacity retention, respectively. The discovery of the highly stable, lithiophilic NW decorated CP hosts is a promising route toward stable cycling LMBs and provides a new design motif for hosted Li metal anodes.
Keywords: Carbon frameworks, Li metal, Lithiophilic, Nanowires

Figure 1. Synthesis and phase characterization of different NW-coated CP substrates (CP-Si, CP-SiGe, CP-Ge). a) Schematic illustration of the steps involved in the synthesis process of Si, SiGe alloy and Ge NWs coated CP substrates. b) Photographic images of steps involved in the fabrication of NW-coated CP substrates (substrate area: 0.71 cm2). SEM images of c) CP-Si d) CP-SiGe and e) CP-Ge. f) XRD analysis of CP, CP-Sn, CP-Si, CP-SiGe, and CP-Ge NWs between 20° and 70° with the corresponding standard patterns of pure Si and pure Ge phases.

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