In this talk, we explore how control over nanoscale structure can improve cycling stability in high-energy-density, large volume-change alloy anodes.  We specifically focus on heavier main-group alloys composed of SbSn or pure Sb because of their metallic conductivity.  To improve cycling stability, we created nanoporous (NP) materials using selective dealloying, which is a facile and scalable synthetic approach.  We then apply <i>operando</i> transmission X-ray microscopy (TXM) to follow structural change during electrochemical cycling.  TXM imaging indicates that the pores in NP-SbSn are well preserved upon lithiation and delithiation, a result that stands in sharp contrast to pure NP-Sn, which show significant pore fracture upon cycling.  Operando X-ray diffraction indicates that the Sb and Sn lithiate at different potentials, so that there is always a non-reactive component stabilizing the pore systems.  Interestingly, while all Sb alloys are crystalline, the Sn component of NP-SbSn becomes amorphous upon cycling, and the amorphous fraction may increase ductility, further stabilizing the pore system.  In agreement with this idea, NP-Sb shows very different behavior when cycled through crystalline versus amorphous intermediates.  When cycled with Li, which goes through a series of crystalline phases, NP-Sb shows significant particle fracture, even in nanoporous form.  In contrast, NP-Sb cycled with Na, which shows amorphous intermediates, is highly resistant to cracking, despite the fact that it shows larger overall volume expansion.  Together, these examples illustrate how a combination of nanoscale and atomistic structural control can lead to enhanced cycling stability in high volume change anode materials.

Using transmission X-ray microscopy to understand structural change during electrochemical cycling in nanoporous alloy anodes based on Sb and Sn

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.