Multifunctional Cross-Linking Composite Binder Enables the Stable Performance of Si-Based Anodes for High-Energy-Density Lithium-Ion Batteries

The intrinsic volumetric stress during cycling is the main obstacle for developing Si-based materials as high-energy-density lithium-ion battery anodes. Elastic binders have been demonstrated as an efficient approach to alleviate the stress of Si. Herein, we design a tough 3D hard/soft polymeric network (LPTS) using lithiated poly(acrylic acid), silk sericin, and highly branched tannic acid. Covalent cross-linking provides a robust mechanical strength to endure the large stress. The formed multiple hydrogen bonds with bonding energies between 3.46 and 25 kcal mol–1 can effectively dissipate the stress through sequential hydrogen bond disassociation. The multifunctional LPTS binder maintains the integrity of the Si-based electrodes during repeated discharging/charging. Additionally, Li+ can be transferred via a Li-conducting group (−COOLi), thereby enhancing the ionic conductivity of electrodes. Consequently, the Si/LPTS electrode exhibits an improved initial Coulombic efficiency and excellent durability over 400 cycles. Meanwhile, this binder is also suitable for Si–C anodes, enabling stable cycling at a high areal capacity >3.6 mAh cm–2 and delivering 72.2% capacity retention for the LFP||Si–C/LPTS full cell after 200 cycles. This study provides insight into developing efficient Si-based binders that are facile and low-cost for next-generation high-energy-density systems.