Physicochemical dual cross-linking polymer stabilizing the Si-C-Cu interfaces for long-life silicon anode

Abstract

Polymer binders possess significant potential in alleviating the volume expansion issues of silicon-based anodes, yet remain challenging due to insufficient interfacial interactions with individual components (Si, C, and Cu) of the anode. Herein, we report the synthesis of a stable three-dimensional network structure of the PAA-PEA (polyacrylic acid-polyether amines) polymer binder through intermolecular physicochemical dual cross-linking. By incorporating polar functional groups, the binder molecules not only form strong C–O–Si, N–Si, O=C–O–C, and O=C–O–Cu covalent bonds but also enhance non-covalent interactions with Si, C, and Cu, thereby improving adhesion between the binder and each interface of the anode. Furthermore, weak hydrogen bonds, acting as “sacrificial bonds”, dissipate energy and disperse accumulated stress, improving the material flexibility. Due to the high mechanical stability of the framework, which combines both rigidity and flexibility and the coupling effect at the three interfaces, the movement and separation of electrode components are effectively restrained, significantly enhancing the cycling stability of silicon-graphite anodes. The PAA-PEA 2000 electrode exhibits a capacity retention of 78% after 500 cycles at a current density of 0.2 A g⁻¹. This work provides insights into the mechanism of binders and guides the design of polymer binders for high-performance Si-based electrodes.