Insights into the Degradation Mechanism of Nanoporous Alloy-Type Li-Ion Battery Anodes

While nanostructured alloy-type anodes are considered potential high-capacity alternatives to intercalation-type graphite anodes, large volume changes inherent to alloy-type anode cycling result in poor cycling performance. In this work, model nanoporous gold anodes are used to investigate the degradation behavior of nanostructured alloy-type anodes during cycling. Transmission electron microscopy and small-angle X-ray scattering are performed across several length scales on anodes cycled to various sequential charge states. By coupling these data sets, we propose a general model for the degradation of the solid-electrolyte interphase (SEI) and morphology during the early stages of cycling in nanoporous alloy-type anodes: (1) during lithiation, active material nanoparticles created by material pulverization during volume expansion become trapped in a thick SEI layer; and (2) during delithiation, a bimodal, hierarchical nanoporous morphology forms, and the SEI and nanoparticles formed during lithiation delaminate from the framework due to volume contraction.

Automated summary

In this study, model nanoporous gold anodes were used to investigate the degradation behavior of nanostructured alloy-type anodes during cycling. Transmission electron microscopy and small-angle X-ray scattering were used across several length scales to study anodes cycled to various sequential charge states. By coupling these data sets, a general model for the degradation of the solid-electrolyte interphase (SEI) and morphology during the early stages of cycling in nanoporous alloy-type anodes was proposed.