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What happens structurally and chemically during sodium uptake and release by Ni2P2S6: a combined X-ray diffraction, X-ray absorption, pair distribution function and MAS NMR analysis

DOI: 10.1039/D0TA07889A DOI Help

Authors: Wolfgang Bensch (Kiel University) , Jonas Van Dinter (University of Kiel) , Kevin Synnatschke (Heidelberg University) , Tobias Engesser (University of Kiel) , Sylvio Indris (Karlsruhe Institute of Technology) , Niklas Wolff (University of Kiel) , Ole Gronenberg (University of Kiel) , Martin Etter (Deutsches Elektronen-Synchrotron (DESY)) , Giannantonio Cibin (Diamond Light Source) , Lorenz Kienle (University of Kiel) , Claudia Backes (Heidelberg University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Materials Chemistry A

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 20060

Abstract: The layered compound Ni2P2S6 was electrochemically characterized for application as anode material in sodium-ion batteries (SIBs). A high reversible capacity of 621 mAh g 1 at 1 A g 1 was achieved after 190 cycles. The investigation of the complex reaction mechanism of the conversion reaction was performed applying complementary techniques including X-ray powder diffraction, pair distribution function analyses, X-ray absorption spectroscopy, 19F/23Na/31P MAS NMR, TEM and nano-EDX. The results highlight that Na uptake for up to 5 Na/formula unit (f.u.) led to reduction of Ni2+ to metallic Ni nanoparticles and concomitant formation of an intermediate compound Na4P2S6. Increasing the Na content to 12 Na/f.u. generates nanocrystalline Na2S, which is accompanied by loss of the long-range order of the pristine sample. In the completely discharged state elemental Ni and Na2S are present, but in contrast to literature reports, no evidence for the formation of NaxP phases was found. During the charge process, Ni3S2 is formed upon the release of ~11.7 Na/f.u. A very high specific capacity of 621 mAh g 1 at 1.0 A g 1 is obtained after 190 cycles, and Coulombic efficiencies reach nearly 100% after the 3rd cycle.

Diamond Keywords: Batteries; Sodium-ion

Subject Areas: Materials, Chemistry, Energy

Instruments: B18-Core EXAFS

Other Facilities: PETRA III

Added On: 22/10/2020 09:11

Discipline Tags:

Physical Chemistry Energy Energy Storage Materials Science Energy Materials Chemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)