Research on the Thermal Safety of Ion-Doped Na3V2(PO4)3 for Sodium-Ion Batteries

Na3V2 (PO4)3 (NVP) is considered to be a promising cathode material for sodium-ion batteries (SIBs). Ion doping can effectively improve its structural deformation, poor conductivity, and electrochemical performance. However, the research on the effect of ion doping on the thermal stability of NVP is still limited. In this paper, Mg/Ti co-doped and Mn/Ti co-doped modified NVP with carbon nanotubes (CNTs) (MgTi@ CNTs and MnTi@CNTs) were prepared, respectively, and X-ray diffraction (XRD) results proved that MgTi@CNTs and MnTi@CNTs have good structural stability and crystallinity. The electrochemical performance indicates that the dual strategy of p-n-type co-doping and CNT coating provides superior sodium storage performance, enhancing both electronic conductivity and ion diffusion. Secondly, based on the safety point of view, the thermal stability of p-n-type ion-doped NVP and its mixed system with electrolyte in a charged state was studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and accelerated calorimeter (ARC). The results show that the optimized MgTi@CNTs and MnTi@CNTs electrodes exhibit excellent thermal stability in the absence of electrolytes, indicating their high intrinsic safety. However, it is worth noting that in the electrode/electrolyte system, p-n-type ion-doped NVP have higher reactivity with the electrolyte, and their comprehensive thermal safety is lower than that of NVP. Therefore, in practical applications, it is necessary to comprehensively consider the thermal stability of the material and the thermal safety of its mixed system with the electrolyte. This paper provides a data basis for the practical application of NVP in SIBs.