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

Currently, Si (or SiO, 1 < < 2) and graphite composite (Si/C) electrodes (e.g., Si/C450 and Si/C600 with specific capacities of 450 and 600 mAh g 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) 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)] achieves improved mechanical and adhesive properties and decreased Si/C anode volume expansion, compared to the linear binder counterpart. Impressively, the P(SH-BA) 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 LiNiCoMnO cathode (15 mg cm) 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.