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Title: Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques

Here, the structure of pristine AgFeO 2 and phase makeup of Ag 0.2FeO1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2O 3 phases) was investigated using synchrotron x-ray diffraction. A new stacking-fault model was proposed for AgFeO2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2FeO 1.6 were investigated using ex-situ, in-situ, and operando characterization techniques. An amorphous γ-Fe 2O 3 component in the Ag 0.2FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2FeO 1.6 composites demonstrated differences in the structural evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex-situ x-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in-situ high energy x-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+yFe IIIFe IIyO 2 phase. The Li 1+yFe IIIFe IIyO 2 phase can thenmore » reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2FeO 1.6 composite, a substantial amorphous γ-Fe 2O 3 component is observed which discharges to rock salt LiFe 2O 3 and Fe 0 metal phase in the 3.5 – 1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [2] ;  [4] ;  [1] ;  [1] ;  [4] ;  [4] ;  [4] ; ORCiD logo [5] ;  [6] ; ORCiD logo [6]
  1. Stony Brook Univ., NY (United States). Dept. of Chemistry
  2. Stony Brook Univ., NY (United States). Dept. of Materials Science and Engineering
  3. Brookhaven National Lab. (BNL), Upton, NY (United States). Energy Sciences Directorate
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
  5. Stony Brook Univ., NY (United States). Dept. of Chemistry; Stony Brook Univ., NY (United States). Dept. of Materials Science and Engineering; Brookhaven National Lab. (BNL), Upton, NY (United States). Energy Sciences Directorate
  6. Stony Brook Univ., NY (United States). Dept. of Chemistry; Stony Brook Univ., NY (United States). Dept. of Materials Science and Engineering
Publication Date:
Report Number(s):
BNL-114168-2017-JA
Journal ID: ISSN 1463-9076; PPCPFQ
Grant/Contract Number:
SC0012704; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 19; Journal Issue: 33; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE
OSTI Identifier:
1376184