In Situ Nanoscale Imaging of Cultivated, As-Grown Diatom Frustules Electrochemical Lithiation/Delithiation in Li Ion Battery Anodes

Silicifying diatoms are unicellular algae that can be cultivated sustainably to aid the battery materials supply chain. Diatom silica frustules (DSF) are explored as active materials or templates for Li ion battery anodes due to the high lithium storage capacity of SiO2, particle size diversity, and porosity, and high potential to reduce carbon footprint associated with Si materials production. However, to practically benefit from their complex hierarchical structures in battery electrodes, an understanding of scale-dependent lithiation and delithiation processes is required at the single particle level with high spatial resolution. Here, we used in situ scanning ion conductance and electrochemical cell microscopy to simultaneously image structure and map electrochemical activity upon lithiation and delithiation of untreated DSF collected from as-grown diatom monoculture. Our results demonstrate a direct correlation between structure, composition, and electrochemical activity of DSF as active particles in half cells and their contribution to full-cell battery electrochemistry that can be maintained reversibly with appreciable capacities upon battery cycling. This opens possibilities to directly assess the electrochemical properties of DSF in situ that will enable us to select and tailor optimum structures for high-performance and sustainable battery applications.