Organic Species-Intercalated Vanadium Oxide for Sodium-Ion Battery: Mixed-Anion Coordination Effect, Enhanced d‑p Orbital Hybridization, and Topotactic Phase Conversion Induced by N‑Substitution

• Published in: Inorganic chemistry 2023-12, Vol.62 (49), p.20105-20119
• Main Authors: Li, Kai, Liu, Changlin, Lv, Jia, Cao, Tong, Zhang, Yunhuai, Gong, Yun, Zheng, Lirong
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c02974

Sodium-ion battery (SIB) is a reasonable alternative to lithium-ion battery (LIB) in the field of grid-scale energy storage systems. Unfortunately, the development of appropriate cathode material is a bottleneck in the field of SIB. In the present work, (p-TQ)-VO, formulated as (p-TQ)0.2V2O5·0.38H2O, was synthesized based on a facile hydrothermal reaction of V2O5 and methylhydroquinone (p-HTQ). And when V2O5 was replaced by VN, (p-TQ)-VN, formulated as (p-TQ)0.22V2(O/N)5, was prepared instead. The (p-TQ)-VO sample displays good electrochemical performance as the SIB cathode. And (p-TQ)-VN shows a much higher capacity at a small current density, and it can maintain structural integrity with partial topotactic phase transformation into Na x V2O5 during the discharge/charge process. A series of characterizations of (p-TQ)-VO and (p-TQ)-VN reveals the successful intercalation of p-TQ into the layered V2O5 with a (001) lattice spacing of 13.7 and 10.7 Å, respectively. In (p-TQ)-VN, partial terminal oxygen (Ot) atoms from the V–O–V layer have been substituted by N atoms, which can boost the orbital hybridization of V 3d and Ot 2p, shorten the V–Ot bonds in the c-axial direction, and elongate the V–O bonds in the ab plane with compressed {VO4N2} octahedra, giving rise to mixed-anion coordination effect. As a result, the enhanced electron densities around the Ot atoms of the V–O–V layer can facilitate the affinity toward the inserted Na+ ions, leading to partial phase conversion into NaNO2/NaNO3. Moreover, density functional density (DFT) calculations reveal that the N-incorporation can improve electron conductivity with richer molecular orbital energy levels, resulting in multistep redox reactions and enhanced capacity.