Synergistic π-π and π-d Interactions Between Carbon Nanotubes and Coordination Polymers Crafting Core-Shell Nanostructured Cathode for High-Performance Sodium-Organic Batteries

Abstract

π-d conjugated coordination polymers hold promising electrode candidates for advanced sodium-ion batteries (SIBs) while they commonly encounter challenges such as restricted electron delocalization and utilization of redox-active sites during electrochemical cycling. Herein, we propose a core-shell composite (CNT@Ni-DHBQ) as the cathode for SIBs via in situ polymerization, in which 2,5-dihydroxy-1,4-benzoquinone (DHBQ) serves as the organic ligand, Ni²⁺ as the metal center, and carbon nanotubes (CNTs) as conductive scaffolds. The well-defined core-shell architecture offers a large specific surface area with numerous exposed sites, enabling fast electron transport and superior rate capability. In addition, robust π-π stacking between Ni-DHBQ and conductive CNT framework significantly enhances cycling stability. A reversible carbonyl (C=O) based redox mechanism in CNT@Ni-DHBQ during cycling is revealed by ex situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. This molecular- and microstructure-engineered strategy provides a feasible strategy to boost the energy-storage performance of organic cathodes in SIBs.