Hollow core-shell Si-PEI@ZIF-67 with cross-linking effect for high-performance Li-ion batteries

Abstract

Owing to its extremely high theoretical capacity (4200 mAh g−1), silicon (Si) has emerged as a promising candidate for lithium-ion batteries (LIBs) anodes. However, challenges such as a volumetric expansion of up to 300 % and poor electrical conductivity have impeded its application. Here, hollow core-shell Si-PEI@ZIF-67 synthesized via a simple one-pot method utilizing the unique properties of ZIF-67, including its porous nature, high surface area, and well-ordered structure, ZIF-67 coating effectively mitigates the volume expansion of nano-Si during cycles. Hollow core-shell structure can accelerate ion transfer and alleviate volume expansion. Moreover, Co2+ enrichment in the coating promotes the formation of a strong cross-linking network with the binder sodium alginate. This interaction not only enhances the adhesion between active material and current collector but also accelerates ion transport. Si-PEI@ZIF-67 composites demonstrate outstanding lithium storage performance in LIBs, achieving a stable capacity of 1134.4 mAh g−1 after 500 cycles at 1000 mA g−1. In addition, the discharge capacity of 828.7 mAh g−1 is maintained after 200 cycles at the high current density of 5000 mA g−1. The innovative synthesis method, utilizing ZIF-67 as a coating for nano-Si and establishing an interconnected network with the binder, offers a novel approach for other anodes.