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Title: In Situ Tracking Kinetic Pathways of Li + /Na + Substitution during Ion-Exchange Synthesis of Li xNa 1.5–x VOPO 4 F 0.5

Ion exchange is a ubiquitous phenomenon central to wide industrial applications, ranging from traditional (bio)chemical separation to the emerging chimie douce synthesis of materials for batteries and other energy applications. The exchange process is complex, involving substitution and transport of different ions under non-equilibrium conditions, and thus difficult to probe, leaving a gap in mechanistic understanding of kinetic exchange pathways toward final products. Herein, we report in situ tracking kinetic pathways of Li +/Na + substitution during solvothermal ion-exchange synthesis of Li xNa 1.5-xVOPO 4F 0.5 (0 ≤ x ≤ 1.5), a promising multi-Li polyanionic cathode for batteries. The real-time observation, corroborated by first-principles calculations, reveals a selective replacement of Na + by Li +, leading to peculiar Na +/Li +/vacancy orderings in the intermediates. Contradicting the traditional belief of facile topotactic substitution via solid solution reaction, an abrupt two-phase transformation occurs and predominantly governs the kinetics of ion exchange and transport in the 1D polyanionic framework, consequently leading to significant difference of Li stoichiometry and electrochemical properties in the exchanged products. The findings may help to pave the way for rational design of ion exchange synthesis for making new materials.
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [4] ;  [5] ;  [6] ;  [3] ; ORCiD logo [4] ; ORCiD logo [3]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States); Seoul National Univ. (Korea, Republic of)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Seoul National Univ. (Korea, Republic of)
  5. Koreal Atomic Energy Research Inst. (Korea, Republic of)
  6. Brookhaven National Lab. (BNL), Upton, NY (United States); Koreal Atomic Energy Research Inst. (Korea, Republic of)
Publication Date:
Report Number(s):
BNL-114157-2017-JA; BNL-114529-2017-JA
Journal ID: ISSN 0002-7863; TRN: US1702362
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 36; Journal ID: ISSN 0002-7863
American Chemical Society (ACS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1413935