Layered hydrate vanadates are promising cathode materials for aqueous zinc-ion batteries (AZIBs). Various intercalants have been preinserted into the interplanar space of hydrate vanadates with significantly enhanced kinetics and stabilized structures. However, such an enhancement is induced by various intercalants, and the relationship between the property enhancement and the type of intercalant still needs to be revealed. In this work, the distortion of octahedra induced by the preintercalation of benzyltrimethylammonium (BTA+) cations into hydrate vanadium pentoxide (V2O5·nH2O, VOH) and the change in ligand field are studied using synchrotron X-ray pair distribution function (PDF) and X-ray absorption fine structure (XAFS). Variations in the local coordination of vanadium alter the ligand field, decreasing the energy of the lowest unoccupied orbitals (e*), which leads to an increased electrochemical potential. Additionally, the introduced BTA+ facilitates fast ion diffusion and stabilizes the layer structure. A cathode with a distorted local structure delivers a specific capacity of 408 mAh/g at 0.5 A/g, with a capacity retention of 95% after 3000 cycles at 8 A/g.
Revealing the mechanism of Mn doping in polyanionic NaFePO4 materials advances our fundamental understanding of electrochemical reactions. Herein, we propose the concept of heterotransition metal ligand field clusters (H-TMLFC) as a framework to investigate the structural evolution of transition metal (TM) ligand fields at the microscopic level. The introduced [MnO6] octahedra exhibit a distinctive half-filled frontier orbital configuration, thereby strengthening σ-bonding interactions and modulating the charge distribution between adjacent [FeO6] units. The redistribution of charge density around the edge-sharing oxygen atoms in [FeO6]–[MnO6] pairs enhances Fe–O covalency and mitigates Fe/Na antisite defects. As a result, H-TMLFC-derived NaFe0.95Mn0.05PO4 achieves an exceptional capacity of 148.9 mAh·g–1 (96.7% of the theoretical capacity) and exhibits superior long-term cycling stability. This work introduces a novel approach for designing high-performance sodium-ion batteries through TM doping, offering atomic-scale insights into the optimization of polyanionic cathode materials.
Molecular design is crucial for improving the performance of single-molecule magnets (SMMs). For dysprosium(III) SMMs, enhancing ligand-field axiality is a well-suited strategy to achieve high-performance SMMs. We synthesized a series of dysprosium(III) complexes, (NNTIPS)DyBr(THF)2 (1, NNTIPS = fc(NSiiPr3)2; fc = 1,1′-ferrocenediyl, THF = tetrahydrofuran), [(NNTIPS)Dy(THF)3][BPh4] (2), (NNTIPS)DyI(THF)2 (3), and [(NNTBS)Dy(THF)3][BPh4] (4, NNTBS = fc(NSitBuMe2)2), supported by ferrocene diamide ligands. X-ray crystallography shows that the rigid ferrocene backbone enforces a nearly axial ligand field with weakly coordinating equatorial ligands. Dysprosium(III) complexes 1–4 all exhibit slow magnetic relaxation under zero fields and possess high effective barriers (Ueff) around 1000 K, comparable to previously reported (NNTBS)DyI(THF)2 (5). We probed the influences of structural variations on SMM behaviors by theoretical calculations and found that the distribution of negative charges defined by rq, i.e., the ratio of the charges on the axial ligands to the charges on the equatorial ligands, plays a decisive role. Moreover, theoretical calculations on a series of model complexes 1′–5′ without equatorial ligands unveil that the axial crystal-field parameters B20 are directly proportional to the N–Dy–N angles and support the hypothesis that enhancing the ligand-field axiality could improve SMM performance.
危险品化学品经营许可证（带存储）