Optimized Hydrogen and Covalent Bond Co-crosslinked Binder with Self-Healing Property for a High-Performance Si Anode of Lithium-Ion Batteries

The commercial application of Si-based lithium-ion batteries (LIBs) has been seriously constrained due to the performance degradation of the Si anode caused by the volumetric stress of Si (de)lithiation. To address this bottleneck, we have explored a novel polymer binder of CSP (Carboxymethyl cellulose-Sodium tetraborate-Poly(vinyl alcohol)) with high self-healing efficiency and elucidated the intrinsic mechanism underlying the improvement of its self-healing efficiency. By regulating the covalent-to-hydrogen bond ratio in CSP, the adsorption distance of physical and chemical bonds in the binder can be optimized, enabling the binder to achieve a self-healing efficiency of 91.1% and a balance between rigidity and flexibility, which is consistent with the results revealed by density functional theory (DFT) simulations. Consequently, the composition-optimized CSP226 binder maintains the structural integrity and cycling stability of the Si anode, achieving a reversible capacity of 1209.9 mAh g–1 at 1.0 A g–1 after 400 cycles and a high area capacity above 5.79 mAh cm–2 at a Si loading amount of 1.87 mg cm–2. A full cell with a Si anode and NCM811 cathode delivers 219.4 mAh g–1 with a 93.1% capacity retention after 100 cycles.