Zaid Mohammad, Karuppusamy Masiyappan, Patra Biplab, Garlapati Kiran Kumar, Murugan Natarajan Arul, Senguttuvan Premkumar, Pol Vilas G, Martha Surendra Kumar
Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana, 502284, India.
Department of Computational Biology, Indraprastha Institute of Information Technology Delhi, New Delhi, 110020, India.
Small. 2025 Jul 9:e2504006. doi: 10.1002/smll.202504006.
Sodium vanadium fluorophosphate (NaVO(PO)F, NVOPF), with a NASICON framework, is a promising cathode material due to its robust 3D structure, high operating potential (∼3.8 V), and theoretical energy density (≈494 Wh kg). However, its commercial viability is limited by low electronic conductivity and a reduced practical energy density. To address these limitations, vanadium in NVOPF is partially substituted with cost-effective Mn and Cr via a one-pot solvothermal method. This co-doping induces lattice distortion, enhances Na⁺ diffusion kinetics, and improves ionic/electronic conductivity, as confirmed by DFT calculations. The optimized NaVMnCrO(PO)F (NVMC-95) cathode delivers an initial discharge capacity of 120 mAh g at 0.1 C and 87 mAh g at 20 C, with 94% capacity retention after 500 cycles at 1 C and 76% after 2000 cycles at 5 C. The co-doped NVOPF exhibits excellent thermal stability at 40 °C, retaining 91% of its capacity over 400 cycles at 2 C. In a full-cell configuration (NVMC-95//hard carbon), the system delivers 110 mAh g⁻¹ at 3.75 V, retaining 97% capacity over 100 cycles at 0.2 C. Mn/Cr co-doping synergy in NaVO(PO)F enhances Na⁺ transport, reduces impedance, accelerates diffusion kinetics, and stabilizes cycling, enabling durable NASICON-type cathodes with extended cycle life for practical applications.
氟磷酸钒钠（NaVO(PO)F，NVOPF）具有NASICON结构，由于其坚固的三维结构、较高的工作电位（约3.8 V）和理论能量密度（约494 Wh kg），是一种很有前景的阴极材料。然而，其商业可行性受到低电子导电性和降低的实际能量密度的限制。为了解决这些限制，通过一锅溶剂热法用具有成本效益的锰和铬对NVOPF中的钒进行部分替代。如DFT计算所证实的，这种共掺杂会引起晶格畸变，增强Na⁺扩散动力学，并改善离子/电子导电性。优化后的NaVMnCrO(PO)F（NVMC - 95）阴极在0.1 C时的初始放电容量为120 mAh g，在20 C时为87 mAh g，在1 C下500次循环后容量保持率为94%，在5 C下2000次循环后为76%。共掺杂的NVOPF在40°C时表现出优异的热稳定性，在2 C下400次循环中保持其容量的91%。在全电池配置（NVMC - 95//硬碳）中，该系统在3.75 V时的放电容量为110 mAh g⁻¹，在0.2 C下100次循环后容量保持率为97%。NaVO(PO)F中的Mn/Cr共掺杂协同作用增强了Na⁺传输，降低了阻抗，加速了扩散动力学，并稳定了循环，从而实现了具有长循环寿命的耐用NASICON型阴极，可用于实际应用。
