Covalently Cross-Linked Chemistry of a Three-Dimensional Network Binder at Limited Dosage Enables Practical Si/C Composite Electrode Applications

Currently, Si (or SiO_x, 1 < x < 2) and graphite composite (Si/C) electrodes (e.g., Si/C450 and Si/C600 with specific capacities of 450 and 600 mAh g^-1 at 0.1 C, respectively) have become the most promising alternative to traditional graphite anodes toward high-energy lithium-ion battery (LIB) applications by virtue of their higher specific capacity compared to graphite ones and improved cycle performance compared to Si (or SiO_x) ones. However, such composite electrodes remain challenging to practical for implementation owing to electrode structure disintegration and interfacial instability caused by a large volume change of inner Si-based particles. Herein, we develop a covalent-bond cross-linking network binder for Si/C450 and Si/C600 electrodes via reversible addition-fragmentation chain transfer (RAFT) polymerization. The as-developed binder with a 3 mol % cross-linker of other monomers [termed P(SH-BA_3%)] achieves improved mechanical and adhesive properties and decreased Si/C anode volume expansion, compared to the linear binder counterpart. Impressively, the P(SH-BA_3%) binder at only 3 wt % dosage enables 83.56% capacity retention after 600 cycles at 0.5 C in Si/C450 anode based half-cells and retains 86.42% capacity retention at 0.3 C after 200 cycles and 80.95% capacity retention at 0.5 C after 300 cycles in LiNi_0.8Co_0.1Mn_0.1O₂ cathode (15 mg cm^-2) based homemade soft package full cells. This work provides insight into binder cross-linking chemistry under limited dosage and enlightens cross-linking binder design toward practical Si/C electrode applications.