Triune ethylenediamine tetraacetic acid boosting stabilized V-O skeleton of Na₃V₂(PO₄)₃ with V³⁺/V⁴⁺/V⁵⁺ polyvalent transition characteristics and superior cyclic lifespan

Nowadays, the low intrinsic electronic conductivity of Na₃V₂(PO₄)₃ (NVP) significantly limits its wide application. Herein, ethylenediamine tetraacetic acid (EDTA) is utilized simultaneously as a chelating agent, carbon source, and nitrogen source. EDTA possesses a robust capacity for metal ion chelation, enabling the formation of stable complexes with various metal ions, thereby reducing their reactivity in chemical processes. This stability is beneficial for regulating the redox states of metal ions in certain reactions. In various chemical processes, EDTA can influence the redox properties of metal ions by modulating their coordination environment. Furthermore, the nitrogen atoms within EDTA serve as electron donors, supplying charge carriers that reduce the bandgap, thereby effectively enhancing the electronic conductivity of carbon materials. The X-ray absorption fine structure (XAFS) measurement further verifies the significantly improved V–O band and solid skeleton of NVP52 sample. The porous morphology supplies more active sites for Na⁺ de-intercalation and modified the infiltration effects between electrolyte and active materials. Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrate the highly reversible redox process involving V³⁺/V⁴⁺/V⁵⁺, during which the stress–strain is quite low. NVP52 sample achieves extraordinary capacity retention of 97.08%, 95.09%, 93.91%, and 90.83% at rates of 1, 12, 30, and 60 C after 300, 800, 1100, and 1500 cycles. Furthermore, three types of full cells including NVP52//CHC, NVP52//FeSe₂, and NVP52//NVP52 all release superior sodium storage property, indicating the wide usability of NVP52 material. Simultaneously, the application of accelerating rate calorimetry (ARC) has substantiated the material’s thermal stability, safety during use, and overall performance, thereby highlighting its positive attributes.