Achieving Superconformal Sodium Deposition on Carbon Nanofiber Film by Constructing Axial Oxygen Coordinated Copper Atomic Sites

Abstract

Achieving superconformal deposition of metallic sodium on 3D matrices is a critical challenge for sodium metal batteries (SMBs). Herein, flexible 3D carbon nanofiber films anchored with axial O‐coordinated CuN4O2 single‐atom sites (CuN4O2‐CNF) by a ZnCl2‐mediated thermal activation strategy is designed. Unlike conventional planar CuN3 configurations obtained without ZnCl2, the axial O in CuN4O2 sites exhibits a high density of states near the Fermi level, modulating the electronic structure of neighboring Cu and N. This lowers Na+ adsorption energy, accelerates charge transfer and enhances electrolyte permeability, enabling superconformal sodium deposition. As a result, the CuN4O2‐CNF achieves an ultra‐low nucleation overpotential of 10 mV, a coulombic efficiency of 99.92% over 8,000 h, and exceptional cycling stability exceeding 10,000 h in symmetric cells. The full coin cells paired with a Na3V2(PO4)3 cathode retain 89.5 mA h g−1 after 1,000 cycles at 1 A g−1 and deliver 80.3 mA h g−1 at 5 A g−1, demonstrating superior rate capability. The pouch cells also maintain a stable capacity of 75.8 mA h g−1 after 150 cycles at 58.5 mA g−1. These results highlight the transformative potential of axial‐coordination for designing high‐performance metal batteries, offering insights into interfacial dynamics and host architectures for next‐generation energy‐storage systems.