Nitrogen-Annealed Zinc–Nickel Porous Nanosheets for Electronic State-Enhanced High-Conductivity Anode Energy Storage Mechanism Study

Abstract

This study systematically investigates the role of nitrogen annealing in enhancing the structural and electrochemical properties of ZnNiO₂/NF composite anode materials synthesized via hydrothermal methods. By comparing air-annealed and nitrogen-annealed (400 and 600 °C) samples, it is demonstrated that nitrogen annealing at 400 °C induces the densely stacked nanosheet morphology with optimized lattice regularity, which can significantly improve the charge transport kinetics and the interfacial stability. Electrochemical evaluations reveal an outstanding initial discharge capacity of 1873.6 mAh g^–1, retaining 1363.12 mAh g^–1 after 40 cycles, significantly surpassing the performance of air-annealed (1024.5 mAh g^–1) and high-temperature nitrogen-annealed (600 °C, 1000 mAh g^–1) counterparts. Density functional theory (DFT) calculations elucidate that nitrogen doping introduces impurity energy levels near the Fermi surface, which lowers the diffusion barrier of lithium ions and increases the adsorption energy, resulting in an improvement of the chemical reaction rate and Li⁺ diffusion rate at the material surface.