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.