Realizing reasonable redistribution of platform capacity through valence structure optimization for low strain Na3MnZr(PO4)3 cathode material

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 499; p. 156347
• Main Authors: Deng, Mengting, Sui, Yulei, Rao, Kexin, Wang, Yian, Fei, Wenbin, Sun, Keyi, Yang, Zonglin, Zhang, Xiaoping, Wu, Ling
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: Cathode materials; Na-ion batteries; Na3MnZr(PO4)3; Solid-state method; V-substitution; Na3MnZr(PO4)3; V-substitution; Cathode materials; Solid-state method; Na-ion batteries
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.156347

[Display omitted] •Na3Mn1-xZr1-xV2x(PO4)3@C-N is firstly prepared by a simple solid-phase method.•The capacity of ∼ 3.5 V platform (V3+/V4+ & Mn2+/Mn3+) is increased by 135.3 %.•V-substitution can diminish the proportion of Mn3+/Mn4+ in the redox process.•The Jahn-Teller effect of Na3MnZr(PO4)3 is effectively restrained.•V-substitution is beneficial to the rapid transformation of electron and Na+. Na3MnZr(PO4)3, a manganese-based NASICON phosphate cathode material, is recognized for its significant research value, characterized by an appropriate voltage window, affordability, and friendly environmentally attributes. Nevertheless, Na3MnZr(PO4)3 shares a common drawback with other Mn-based NASICON materials, namely the detrimental Jahn-Teller effect and lower electronic conductivity, alongside its particular sodium de-intercalation process, which further diminishes the cycling stability. Furthermore, the material featuring a dual voltage platform is susceptible to considerable voltage fluctuations within the battery module during backend applications, adversely affecting the stability of overall performances. This study proposes the incorporation of vanadium (V) to refine the valence state structure, thereby mitigating the above limitations. Elemental substitution of V3+ at the transition metal site diminishes the proportion of Mn3+/4+ in the redox process, meanwhile, the V3+/4+ and Mn2+/3+ voltage platforms can be integrated, thus the capacity contribution in the 3.5 V range (135.3 % increase in capacity contribution) is enhanced. This alteration in the desodiation process lessens the tendency of sodium ions to relax from Na1 to Na3 and then back to Na1, thereby minimizing volume changes during charge and discharge cycles. The optimized sample, Na3Mn0.8Zr0.8V0.4(PO4)3, demonstrates a commendable initial discharge capacity (104.6 mAh/g at 0.1C) and exceptional cycling stability, with a capacity retention rate of 70.0 % after 2000 cycles at 2C. This investigation offers effective strategies for the allocation of capacity and rational utilization of multi-electron reaction materials, facilitating their practical applications.