Exploring low-cost high energy NASICON cathodes for sodium-ion batteries via a combined machine-learning, ab initio, and experimental approach

Abstract

Sodium-ion batteries (SIBs) display the essential properties required of a reliable energy-storage device, such as vast availability, good voltage output, and cost-effectiveness. Although initial SIB cathodes delivered a significantly lower capacity than their lithium-ion battery counterparts, new high-capacity cathode materials for SIBs continue to be developed today. This study employed a combined machine-learning (ML), ab initio density functional theory (DFT), and experimental approach to develop low-cost and high-energy cathode materials, i.e. Na_3.5MnV_0.5Ti_0.5(PO₄)₃ (NMVTP), Na_3.5MnV_0.5Fe_0.5(PO₄)₃ (NMVFP), and Na_3.5MnV_0.5Al_0.5(PO₄)₃ (NMVAP). Among these materials, the carbon-coated Na_3.5MnV_0.5Ti_0.5(PO₄)₃ (NMVTP/C) with the most stable formation energy (−1.99 eV) registered an exceedingly high specific capacity of 133.14 mA h g⁻¹, a satisfactory Na⁺ (de)insertion voltage of 3.42 V, and a superior energy output of 455 W h kg⁻¹ in the half-cell configuration. NMVTP/C also exhibits a rapid sodium storage capability for 8000 cycles with a capacity retention of 75% at a considerably high current rate of 14C and an impressive rate proficiency of 59.2 mA h g⁻¹ at 17.5C.