In this talk, we examine the role of nanoscale porosity as a route to improving the stability of high-volume-change alloy anodes.  We specifically employ selective dealloying of mixed metal precursors as a scalable route to nanoporous main group materials that can be alloyed with lithium or sodium.  These main group anodes are being considered as replacements for graphite in traditional lithium ion batteries due to their extremely high capacity that can exceed 2000 Ah/L in practical devices.  Unfortunately, alloy-type anodes suffer from short lifetimes due to large volume changes during lithiation or sodiation.  One solution is to use nanoscale porosity to help accommodate those large volume changes.  Here we specifically focus on nanoporous Sn and nanoporous SbSn, both of which are synthesized by selective etching, and both of which can be alloyed with either lithium or sodium to produce very high capacity anodes.  Using synchrotron based transmission X-ray microscopy (TXM), we are able to directly image changes in both individual grains, and in the nanoscale pore structure itself upon cycling.  We find that porous materials expand much less than bulk materials, because the pores help accommodate the strain.  More importantly, we find that porous alloys like nanoporous SbSn are more stable than pure metals because the two components, which alloy at different potentials, help stabilize the pores system so that the alloy can expand into the pores without causing them to break or fracture. This results in significantly improved cycle stability and provides a practical route to optimizing the properties of high capacity energy storage materials.

Improving stability in high volume change alloy anodes through the use of nanoporous electrodes and <i>operando</i> TXM imaging

2019 Fall National Meeting

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Improving stability in high volume change alloy anodes through the use of nanoporous electrodes and operando TXM imaging