Abstract
Sodium batteries have been regarded as promising candidates for large-scale energy storage application, provided cathode hosts with high energy density and long cycle life can be found. Herein, we report NASICON-structured Na 3 MnZr(PO 4 ) 3 as a cathode for sodium batteries that exhibits an electrochemical performance superior to those of other manganese phosphate cathodes reported in the literature. Both the Mn 4+ /Mn 3+ and Mn 3+ /Mn 2+ redox couples are reversibly accessed in Na 3 MnZr(PO 4 ) 3 , providing high discharge voltage plateaus at 4.0 and 3.5 V, respectively. A high discharge capacity of 105 mAh g -1 was obtained from Na 3 MnZr(PO 4 ) 3 with a small variation of lattice parameters and a small volume change on extraction of two Na + ions per formula unit. Moreover, Na 3 MnZr(PO 4 ) 3 exhibits an excellent cycling stability, retaining 91% of the initial capacity after 500 charge/discharge cycles at 0.5 C rate. On the basis of structural analysis and density functional theory calculations, we have proposed a detailed desodiation pathway from Na 3 MnZr(PO 4 ) 3 where Mn and Zr are disordered within the structure. We further show that the cooperative Jahn-Teller distortion of Mn 3+ is suppressed in the cathode and that Na 2 MnZr(PO 4 ) 3 is a stable phase.
| Original language | English |
|---|---|
| Pages (from-to) | 18192-18199 |
| Number of pages | 8 |
| Journal | Journal of the American Chemical Society |
| Volume | 140 |
| Issue number | 51 |
| Early online date | 2 Dec 2018 |
| DOIs | |
| Publication status | Published - Dec 2018 |
Bibliographical note
Acknowledgements:The synthesis, analysis, and electrochemical characterization of the electrode material were supported by the U.S. Department of Energy, Office of Basic Energy Sciences (Grant number DE-SC0005397). J.B.G and G.H also acknowledge support from the Robert A. Welch Foundation (Grants F-1066 and F-1841). The calculations were done at the National Energy Research Scientific Computing Center and the Texas Advanced Computing Center.
Data Availability Statement
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.8b11388.Experimental details; computational methodology; TGA of the cathode material; XRD pattern and TEM image of the cycled cathode; structure of supercells for DFT calculations; XPS spectra of the cathode at different charging state; crystallographic data of the cathode material; comparison with other cathode materials; magnetic moment and Bader charge calculations (PDF).