Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na0.66CoxMn0.66– xTi0.34O2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na0.66CoxMn0.66– xTi0.34O2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na0.66Co0.22Mn0.44Ti0.34O2 with a P2-type layered structure delivers a reversible capacity of 120 mAh g−1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g−1 can still be obtained, indicating a promising rate capability. The low valence Co2+ substitution results in the formation of average Mn3.7+ valence state in Na0.66Co0.22Mn0.44Ti0.34O2, effectively suppressing the Mn3+-induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na0.66Co0.22Mn0.44Ti0.34O2 during charge/discharge is contributed by Co2.2+/Co3+ and Mn3.3+/Mn4+ redox couples. This is the first time that the highly reversible Co2+/Co3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.
|Publication status||Published - 2017 Nov|
Bibliographical noteFunding Information:
The work at Fudan University was supported by the NSFC (No. 51502039) and 1000 Youth Talents Plan. The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies through Advanced Battery Material Research (BMR) program under Contract No. DE-SC0012704. The authors thank Beamlines BL14W1 and BL14B1 of the Shanghai Synchrotron Radiation Facility in China and technical supports by beamline scientists Sungsik Lee and Benjamin Reinhart at 12BM of Advanced Photon Source at the Argonne National Laboratory, supported by the U.S. Department of Energy, Basic Energy Science, under Contract No. DE-AC02-06CH11357.
© 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
All Science Journal Classification (ASJC) codes
- Medicine (miscellaneous)
- Chemical Engineering(all)
- Biochemistry, Genetics and Molecular Biology (miscellaneous)
- Materials Science(all)
- Physics and Astronomy(all)