Sustainable silicon micro-dendritic anodes integrated by a moderately cross-linked polymer binder with superior elasticity and adhesion

Abstract

The extensive application of silicon (Si) anodes is still impeded, although Si has long been considered as the most potential anode material for the high-energy lithium-ion batteries. In the composition of anodes, binders with a small proportion contribute no direct capacity to the cell, but play a vital role in addressing the issues associated with Si materials (e.g., huge volume expansion, unstable solid electrolyte interphase (SEI) layer and low electrical conductivity). Herein, we design a moderately cross-linked polymer binder polyacrylic acid (PAA)–sodium alginate (SA) to balance the degree of crosslinking and the number of free groups within this polymer structure via a simple esterification reaction, which can support micro-sized silicon dendrites (SD) to form a three-dimensional (3D) anode. The PAA-SA binder with a moderately cross-linked structure can simultaneously realize the mechanical strength, chemical stability, and polymer viscosity, resulting the Si anodes with restricted volume expansion and stable SEI layers during long cycles. Therefore, the SD/PAA-SA anode exhibited superior cycling performance (2929.8 mA h g−1 for 1st cycle, initial Coulombic efficiency of 80.1 % and 1419.8 mA h g−1 at 1 A g−1 after 200th cycle) and good mechanical properties. This work designs a water-soluble binder with a moderately cross-linked polymer structure, which can be applied to developing electrodes with compatible sustainability and electrochemical activity.