High-Performance Anodes for Lithium-Ion Batteries Based on Nano-Porous Amorphous Silica

Abstract

The high theoretical capacity and low discharge potential of silica (SiO2) draw major interest these days as a serious competitor to Si-based anodes. The drastic volume expansion of Si during cycling leads to capacity fading and pulverization and thus requires advanced treatment to make it a viable electrode in Li-ion batteries1-4. Abundantly available diatomaceous earth was explored as an anode which can substitute the existing graphite based anode, providing better electrochemical performance in terms of capacity, cyclability and stability. As silica is an insulator, it is necessary to provide a conductive coating on the particles. Various amounts of corn-starch was added, followed by heat treatment in Ar atmosphere, to form a thin continuous conductive layer of carbon on the particles. Also, conventional binders are not compatible with Si or silica-based materials, hence other types of binders and binder additive must explored. Here we have used a naturally grown algae-based aqueous binder to prepare the electrodes, which is compatible with the diatomaceous earth and gives it increased stability during lithiation and de-lithiation. Specific discharge capacities of these materials have shown values of 600-800 mAhg-1, which is more than twice the value of the existing graphite based anodes. Upon extended cycling the reversible capacity, for uncoated as well as coated silica, starts to increase from approximately the forth cycle due to chemical reactions causing a Si phase to form. The porous morphology and natural nano-structure of the diatomaceous earth anode can accommodate the volume expansion and preserve the solid electrolyte interface. The high reversible capacity, good cycle performance and simple processing of these electrodes make the diatomaceous earth a potential environmentally friendly anode material for lithium-ion batteries. 1. Favors, Z., et al. (2014). Sci. Rep. 4. 2. Yan, N., et al. (2013). Sci. Rep. 3. 3. Liu, X., et al. (2014). Nano Energy 4. 4. Epur, R., et al. (2012). Materials Science and Engineering: B 177(14).