3D porous spheroidal Na4Mn0.9Ce0.1V(PO4)3@CeO2/C cathode for high-energy Na ion batteries

Abstract

The NASICON-type Na₄MnV(PO₄)₃ (NMVP) possesses potential as a cathode material in SIBs, and is known for its stable 3D Na⁺ superconductive framework, high voltage platform, and relatively low cost and toxicity. Nevertheless, the intrinsic poor electronic conductivity and Jahn–Teller effect from Mn³⁺ during cycling limit its further application. Herein, to address such issues, a well-designed 3D porous spheroidal Ce³⁺-doped NMVP@CeO₂/C cathode was constructed via a simple spraying drying-assisted route. As proved, the synergistic effect of Ce³⁺ doping in the crystal framework and CeO₂ surface coating was achieved simultaneously, which greatly improved the electronic conductivity, facilitated the ion diffusion transfer and stabilized the crystalline structure. As a result, the as-prepared sample delivered superior discharge performance (50.3 mA h g⁻¹ at 50C) and long circular life (91.0 mA h g⁻¹ after 2000 cycles at 5C with 86.7% capacity retention). Furthermore, the reversible biphasic reaction for cathodes was confirmed by Galvanostatic intermittent titration technique (GITT) and ex situ XRD. The DFT calculation revealed the influence of Ce³⁺-doping on the crystalline framework and electrochemical properties. Finally, the optimized NMVP cathode also showed great potential for practical utilization through the successful assembly of full cells.