Na3.5(MnVFeTi)0.5(PO4)3: A Multi-Transition-Metal-Ion-Engineered NASICON-Type Cathodes for Sodium Ion Batteries

Abstract

Electrochemically active Na-superionic conductor (NASICON)-type cathodes have the structural flexibility to include various transition elements, thus enabling high power outputs benefited by multi-electron redox reactions. This study amalgamated multiple transition metal ions to construct a new NASICON-type cathode i. e., carbon coated Na_3.5(MnVFeTi)_0.5(PO₄)₃ (NMVFTP/C) for Na-ion batteries (NIBs). The NMVFTP/C cathode engineered in this study demonstrated stable Na⁺-storage capacity, including long-term cycling stability up to 4000 cycles at 3000 mA g⁻¹ with 96 % capacity retention and a high-rate output capacity of 85.16 mAh g⁻¹ at 2500 mA g⁻¹. To elucidate the ion transport process within the cathode, density functional theory modeling was employed. The low energy barrier for the diffusion of Na⁺ in the NMVFTP/C materials was proved to be a key factor supporting our material's superior electrochemical performances.