Journal
ENERGY STORAGE MATERIALS
Volume 23, Issue -, Pages 25-34Publisher
ELSEVIER
DOI: 10.1016/j.ensm.2019.05.041
Keywords
Sodium-ion batteries; Na3.5Mn0.5V1.5(PO4)(3) cathode; In situ XRD; X-ray absorption near-edge structure; DFT computations
Funding
- National Natural Science Foundation of China [21825102, 21805007, 21731001, 21590793]
- Young Elite Scientists Sponsorship Program by CAST [2018QNRC001]
- Fundamental Research Funds for the Central Universities [FRF-TP-18-001C2]
- DOE Office of Science [DE-AC02-06CH11357]
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Na3V2(PO4)(3) is one of the most promising cathodes for sodium-ion batteries (SIBs) due to its three-dimensional framework. To meet practical feasibility, the substitution of vanadium with low-cost active elements is urgent. Here the Na+ superionic conductor (NASICON)-type Na3.5Mn0.5V1.5(PO4)(3) nanoparticles homogeneously embedded in porous carbon matrix are prepared and investigated as a novel cathode for SIBs. The as-prepared Na3.5Mn0.5V1.5(PO4)(3)/C could deliver a desirable average discharge potential of 3.43 V vs. Na+/Na with fascinating rate capability of 92.7 mA h g(-1) at 60C and impressive capacity retention of 87.2% after 4000 cycles at 20C. In situ X-ray diffraction reveals that the electrochemical process undergoes highly reversible biphasic transition and single phase change with a relatively small volume change (8.21%), ensuring the high structural stability and excellent cyclic capability. The reversible evolution of Mn2+/(3+) and V3+/4+ redox couples upon Na+ extraction/insertion has been revealed by the confirmation of valence state via both ex situ X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. The superior performance of Na3.5Mn0.5V1.5(PO4)(3) could be attributed to the high electronic/ionic conductivity and low sodium-ion diffusion energy barrier, which is supported by the electrochemical impedance spectroscopy and cyclic voltammetry measurements, as well as density functional theory computations.
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