A novel NASICON-type Na3MnTi0.5Zr0.5(PO4)3 cathode material with multivalent redox reaction for high performance sodium-ion batteries

Abstract

Na₃MnZr(PO₄)₃, a typical manganese-based NASICON-type material, has consistently been at the forefront of research on cathode materials for sodium-ion batteries due to the abundant manganese reserve and high operating voltage. However, the severe Jahn-Teller effect, poor electronic conductivity and kinetic limitation of Na₃MnZr(PO₄)₃ impose constraints on its rate capability and cycling performance, thereby hindering its practical application. To address this challenge, a ternary NASICON-type material Na₃MnTi_0.5Zr_0.5(PO₄)₃/C, with a multi-metal synergistic effect, is proposed in this study. The substitution of Ti at Zr site significantly mitigates the Jahn-Teller effect induced by Mn³⁺. Furthermore, the stability of the ZrO bond is enhanced, leading to a more robust crystal structure overall. Cyclic voltammetry and constant-current intermittent titration techniques reveal that the appropriate Ti substitution markedly boosts the electronic conductivity and Na⁺ diffusion coefficient of the electrode material, thereby mitigating polarization effects and expediting electrode reaction rates. Leveraging the multi-effect of Ti substitution, the prepared Na₃MnTi_0.5Zr_0.5(PO₄)₃/C presents an improved electrochemical performance. Notably, Na₃MnTi_0.5Zr_0.5(PO₄)₃/C enables a high discharge capacity of 71.0 mAh g⁻¹ at 10C and maintains 78.8 % capacity after 1000 cycles at 2C rate. This investigation establishes a robust theoretical foundation for comprehending the synergistic effects of multimetal systems in NASICON materials and offers insights into the development of cost-effective, high-performance cathode materials.