Abstract
Mn-containing sodium superionic conductor (NASICON) compounds have shown considerable potential as cathode for sodium-ion batteries (SIBs) owing to higher working voltage (V5+/V4+: 3.9V), lower cost, and lower toxicity compared to full vanadium-based NASICON Na3V2(PO4)3. Taking Na3.3V1.7Mn0.3(PO4)3 (NVMP) as an example, its practical application is still restricted by poor electronic conductivity, sluggish intrinsic Na+ diffusion, and poor high-voltage stability. In this work, a high entropy strategy is proposed to develop Na3.3V1.613Mn0.3(Cr, Fe, Co, Ni, Zr)0.1(PO4)3 (HE-NVMP) cathode for not only enabling more and rapid Na+ migration but also significantly improving deep desodiation stability. Based on theoretical calculations and experimental findings, such high entropy modification can efficiently alter the coordination environments of both V/Mn and Na sites for reducing Na+ diffusion energy barrier, increasing the occupancy of Na+ at Na(2)sites, and consolidating the structure stability. Thus, the obtained HE-NVMP delivers superior high-rate capability (91.7 mAh g-1) up to 50 C and excellent cycling performance (capacity retention: 81.2%) after 10000 cycles at 20 C at the cutoff voltage of 4.1V. More importantly, such cathode also exhibits superior sodium storage properties at a higher cutoff voltage (4.5V) with electrochemical polarization with 75% reduction at 1 C and higher capacity retention of 80.3% after 2000 cycles at 20 C compared to pristine counterpart, indicating a great potential for practical rechargeable batteries with excellent overcharge resistance capability.
Published Version
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