Cross-Linkable Binders for Si Anodes in High-Energy-Density Lithium-Ion Batteries.

Although silicon (Si) has a high theoretical capacity, the large volume expansion during lithiation has greatly hindered its application in high-energy-density lithium-ion batteries (LIBs). Among the strategies for improving the performance of Si anode, the role of binders should not be underestimated. Here, a novel strategy for designing a cross-linkable binder for Si anode has been proposed. The binder with hydroxyl and nitrile groups can be in situ covalently cross-linked through the amide group in the batteries. The cross-linked binder (-POAH) shows high elasticity and strong adhesion to Si particles and the current collector. Si||Li half coin cells using the -POAH binder have excellent cycle performance and the capacity retention ratio is 67.1% after 100 cycles at 0.2 C. Scanning electronic microscopy images show that the -POAH binder can contribute to suppressing the pulverization of the Si anode. Moreover, the investigation with X-ray photoelectronic spectrum demonstrates that the decomposition of the liquid electrolyte on Si anode has been mitigated and the -POAH binder can promote the formation of a more stable SEI film. Our strategy of endowing the binder with good elasticity through in situ cross-linking has opened up a new route for developing binders, which will definitely promote the application of Si anodes in high-energy-density LIBs.