Intelligent stress-adaptive binder enabled by shear-thickening property for silicon electrodes of lithium-ion batteries

Elastic binders with supramolecular interactions are widely explored to mitigate the stress caused by the volume expansion of electrode materials, such as Si, S, or Li metals, in next-generation secondary batteries. Herein, a new class of elastic binders is proposed with an automatic stress-control mechanism capable of responding in real time to dynamic local stress variations. Specifically, this study focuses on the shear-thickening behavior, wherein polymers automatically amplify their viscoelasticity in response to local shear-stress changes. To realize an intelligent stress-adaptive binder, starch analogs exhibiting shear-thickening properties and unique crystallinity are employed as binders for highly expandable Si anodes. The shear-thickening mechanism is comprehensively investigated using deep-learning-based molecular dynamics (MD) simulations and in situ transmission electron microscopy (TEM) analysis, which determines the optimal conditions for effectively limiting dynamic local surface expansion. Among the starch analogs, the amylose and long-chain amylopectin (AMLAP) binder demonstrates improved high-rate capability (1710 mAh g${}^{-1}$ at 5 C) and superior reversible capacity (2025 and 1493 mAh g${}^{-1}$ after 100 and 500 cycles, respectively, at 1 C) with optimal shear-thickening properties. Furthermore, AMLAP exhibits favorable characteristics for affordable large-scale production. Hence, this study clearly demonstrates that the shear-thickening properties of binders can be considered a new factor in fabricating stable electrodes with extremely expandable materials. (© 2024 Wiley‐VCH GmbH)