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Title: Defect-Tolerant Diffusion Channels for Mg2+ Ions in Ribbon-Type Borates: Structural Insights into Potential Battery Cathodes MgVBO4 and Mgx Fe2–xB2O5

The reversible room temperature intercalation of Mg2+ ions is difficult to achieve, but may offer substantial advantages in the design of next-generation batteries if this electrochemical process can be successfully realized. Two types of quadruple ribbon-type transition metal borates (MgxFe2-xB2O5 and MgVBO4) with high theoretical capacities (186 mAh/g and 360 mAh/g) have been synthesized and structurally characterized through the combined Rietveld refinement of synchrotron and time-of-flight neutron diffraction data. Neither MgVBO4 nor MgxFe2-xB2O5 can be chemically oxidized at room temperature, though Mg can be dynamically removed from the latter phase at elevated temperatures (approximately 200 - 500 °C). Findings show that Mg diffusion in the MgxFe2-xB2O5 structure is more facile for the inner two octahedral sites than for the two outer octahedral sites in the ribbons, a result supported by both the refined site occupancies after Mg removal and by bond valence sum difference map calculations of diffusion paths in the pristine material. Mg diffusion in this pyroborate MgxFe2-xB2O5 framework is also found to be tolerant to the presence of Mg/Fe disorder since Mg ions can diffuse through interstitial channels which bypass Fe-containing sites.
Authors:
 [1] ;  [2] ;  [3]
  1. Stony Brook Univ., NY (United States). Dept. of Chemistry
  2. Stony Brook Univ., NY (United States). Dept. of Chemistry; Univ. of Cambridge (United Kingdom)
  3. Stony Brook Univ., NY (United States). Dept. of Chemistry; Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
OSTI Identifier:
1239784
Report Number(s):
BNL--111676-2015-JA
Journal ID: ISSN 0897-4756; R&D Project: CO009; KC0302010
Grant/Contract Number:
SC0012583; AC02- 98CH10086; AC05- 00OR22725; AC02- 06CH11357
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 27; Journal Issue: 13; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
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:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY