Dual carbon decorated Na3.5Mn0.5V1.5(PO4)3 cathode with high-density and long-cycling span-life for sodium-ion batteries

Mn-based NASICON-structural cathodes are considered as the prospective candidate for sodium ion batteries in the matter of high working potential, low price, and environmental-kindly. Herein, the carbon nanotubes anchoring in the amorphous carbon coating Na_3.5Mn_0.5V_1.5(PO₄)₃ particle (NMVP@C@CNTs) is fabricated via the sol-gel procedure and post heat-treatment. After decorating CNTs forming 3D conductive framework can virtually ameliorate the electroconductivity of composite and facilitate the sodium ion diffusivity, thus significantly boosting the sodium storage properties. Via the stepwise redox reactions of V³⁺↔V⁵⁺ and Mn²⁺↔Mn³⁺, the as-prepared NMVP@C@CNTs cathode delivers the high discharge capacity (124.5 mAh g⁻¹ at 0.2C), high output potential (3.45V), dramatic rate capability (96.2 mAh g⁻¹ at 10C), and low fade rate of 0.003 % per cycle in the long-term cylcing at 10C. The results of X-ray diffraction during cycling imply that the NMVP@C@CNTs electrode undergoes a single-phase change and biphasic transition structural evolution. Furthermore, the fabricated NMVP@C@CNTs and hard carbon full cell demonstrates an output voltage of 3.34V, satisfactory energy density (348.7 Wh kg⁻¹), and appropriate cyclability of 89.6 % after 90 cycles at 2C. This work provides an economical and sustainable approach to explore Mn-based NASICON-structural cathodes for grid-scale energy storage devices.