钙离子与三氟甲基磺酸根离子共插层V₃O₇纳米带用于高容量水系锌离子电池正极材料

Ca²⁺/OTf⁻ Co-Intercalated V₃O₇ for High-Capacity Aqueous Zinc-Ion Batteries

摘要: 七氧化三钒(V₃O₇，简称VO)作为一种典型的层状钒氧化物，具有高理论比容量和成本低等优点，是水系锌离子电池(AZIBs)正极材料的有力候选者之一。然而，其固有的层间距狭窄导致的锌离子扩散缓慢以及循环过程中钒溶解等问题严重制约了其进一步发展。针对此，本文采用一步水热法制备了钙离子(Ca²⁺)和三氟甲基磺酸根离子(OTf⁻)共插层的V₃O₇正极材料(SVO)。该正极材料具有更高的比容量和循环稳定性。具体来说，Ca²⁺作为层间支柱，可以显著扩大V₃O₇的层间距，从而提高Zn²⁺的扩散速率；OTf⁻的插入可中和共嵌入Ca²⁺的部分正电荷，有效抑制了因Ca²⁺嵌入引起的钒的过度还原与过量氧空位的生成，从而提升钒氧化物的氧化还原活性。通过XRD、Raman、TGA、XPS等表征测试，证实了Ca²⁺与OTf⁻在V₃O₇层间的成功共嵌入。最后，组装的Zn//SVO电池在0.5 A∙g⁻¹的电流密度下实现了497 mAh∙g⁻¹的高比容量，显著优于空白VO (372 mAh∙g⁻¹)和Ca²⁺插层的VO (466 mAh∙g⁻¹, CVO)。同时，该电池还表现出优异的倍率性能，在电流密度增加到10 A∙g⁻¹时，仍能保持213.8 mAh∙g⁻¹的比容量。此外，Zn//SVO电池在10 A∙g⁻¹的电流密度下经过12,000次循环后容量保持率高达87%，其稳定性远优于VO (34%)和CVO (43%)。

Abstract: Trivanadium heptaoxide (V₃O₇, abbreviated as VO), a typical layered vanadium oxide, exhibits the advantages of high theoretical specific capacity and low cost, making it one of the promising candidates for cathode materials in aqueous zinc-ion batteries (AZIBs). However, the slow diffusion of Zn²⁺ caused by its intrinsically narrow interlayer spacing and vanadium dissolution during cycling severely restrict its further development. To address these drawbacks, a V₃O₇ cathode material co-intercalated with calcium ions (Ca²⁺) and trifluoromethanesulfonate ions (OTf⁻), denoted as SVO, was synthesized via a one-step hydrothermal method in this work. The as-prepared cathode delivers enhanced specific capacity and cycling stability. Specifically, Ca²⁺ acts as an interlayer pillar to significantly expand the interlayer spacing of V₃O₇, thereby accelerating the diffusion kinetics of Zn²⁺. The intercalation of OTf⁻ neutralizes part of the positive charge from co-inserted Ca²⁺, effectively suppressing the over-reduction of vanadium and excessive generation of oxygen vacancies induced by Ca²⁺ intercalation, thus improving the redox activity of the vanadium oxide. Characterizations, including XRD, Raman spectroscopy, TGA, and XPS, verified the successful co-intercalation of Ca²⁺ and OTf⁻ into the interlayers of V₃O₇. Finally, the assembled Zn//SVO cell achieved a high specific capacity of 497 mAh∙g⁻¹ at a current density of 0.5 A∙g⁻¹, which was remarkably superior to those of pristine VO (372 mAh∙g⁻¹) and Ca²⁺-intercalated VO (466 mAh∙g⁻¹, CVO). Meanwhile, the cell exhibited outstanding rate capability, retaining a specific capacity of 213.8 mAh∙g⁻¹ even when the current density increased to 10 A∙g⁻¹. Furthermore, the Zn//SVO cell displayed a high capacity retention of 87% after 12,000 cycles at 10 A∙g⁻¹, and its cycling stability was far better than that of VO (34%) and CVO (43%).