Developing low-resistance ion migration pathways using perfluorinated chain-decorated COFs for enhanced performance in zinc batteries

Abstract

Rechargeable aqueous zinc metal-based batteries present a promising alternative to conventional lithium-ion batteries due to their lower operating potentials, higher capacities, intrinsic safety, cost-effectiveness, and environmental sustainability. However, the use of aqueous electrolyte in zinc metal-based batteries presents its own unique set of challenges, which include the tendency for side reactions during discharge that encourages dendritic growth on Zn anodes, as well as sluggish kinetics caused by the large solvation shell of divalent Zn ions. Nanoporous materials can be deployed as coating on Zn anodes for enhancing both their performance and stability, particularly in addressing challenges associated with water reactivity and ion migration kinetics. In our study, we incorporated superhydrophobic fluorine chains into covalent organic frameworks (SPCOFs) to engineer nanochannels that facilitate efficient ion migration pathways. Molecular dynamics simulations demonstrate that these superhydrophobic fluorine chains significantly reduce interactions between the electrolyte and nanochannel walls, altering the confined electrolyte distribution. This modification enables rapid dehydration, reduces ion migration resistance, and promotes dense Zn deposition. The use of SPCOFs enable Zn batteries with exceptional stability, achieving over 5000 hours of runtime at high current densities and stable cycling across 800 cycles in full-cell configurations. This approach highlights the critical role of tailored nanochannel environments in advancing the functionality and durability of zinc metal-based batteries, offering a scalable and environmentally friendly alternative to traditional battery technologies.