Dynamic bonded supramolecular binder enables high-performance silicon anodes in lithium-ion batteries

摘要

Silicon-based lithium ion battery is reckoned as an ideal choice owing to its ultrahigh theoretical capacity and rich natural resources. However, its practical application is largely hampered by the low Coulombic efficiency (CE) and fast capacity decay arising from the substantial volumetric variations and the unstable solid-electrolyte interphase (SEI). Herein, we propose a binder-based optimization, where a three-dimensional (3D) binder network is devised with organic polyvinyl alcohol (PVA) backbones cross-linked by a functional boric acid (BA). Apart from the improved mechanics, B-OH bond is able to set a chemical bridge between the binder and Si surface by dehydration with Si-OH group, which enables the coherent link with Si surface. More importantly, the electron deficient B element readily accepts electrons during the cell formation and thus facilitates the buildup of an effective SEI film. The obtained lithium borate species significantly reduce the interfacial side reactions and improve the initial Coulombic efficiency (ICE). After optimization of the key parameters, a high ICE (92.76%) with excellent rate capability (similar to 2920.73 mAh g(-1) at 10 C) is obtained. After 500 cycles, the Si anode retained a capacity of similar to 1883.7 mAh g(-1), massively outperforming the pure PVA-based Si counterpart (similar to 317.9 mAh g(-1)).