Intermolecular interaction engineering to enhance lithium-ion storage in two-dimensional oxidized silicon nanosheet anodes

Abstract

Unlike conventional Si anodes for use in Li-ion batteries, 2D oxidized Si nanosheets, i.e., siloxene, undergo negligible volume expansion during cycling owing to their unique geometries and chemical structures. Never-theless, siloxene receives less attention than other Si-based nanostructures, partly because the interactions of siloxene with conventional binders and their effects on charge storage are largely unexplored. Herein, the intermolecular interactions of siloxene with four typical binders (alginate, carboxymethyl cellulose, polyacrylic acid, and alpha-polyvinylidene fluoride) are investigated to enhance the electrochemical performance using a simple method. The binders are selected using two criteria, i.e., polarity and functional groups, and they exhibit different intermolecular interactions with siloxene. Particularly, alginate forms the strongest intermolecular bonds, which are attributed to dipole-dipole attractions between the H atoms in siloxene and the OH groups in alginate. The trend of the intermolecular binding strengths of the binders is consistent with those of the cycling stabilities and rate performances. The alginate-based siloxene electrode displays an excellent charge capacity retention of 66 % after 500 cycles at 200 mA g-1, which is unprecedented for pristine siloxene anodes. This study provides useful guidelines for designing binders for use in electrode materials with chemical structures similar to that of siloxene.