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Title: Crystal engineering in 3D: Converting nanoscale lamellar manganese oxide to cubic spinel while affixed to a carbon architecture

Here, by applying differential pair distribution function (DPDF) analyses to the energy–storage relevant MnOx/carbon system— but in a 3D architectural rather than powder–composite configuration—we can remove contributions of the carbon nanofoam paper scaffold and quantify the multiphasic oxide speciation as the nanoscale, disordered MnOx grafted to the carbon walls (MnOx@CNF) structurally rearranges in situ from birnessite AMnOx (A = Na +; Li +) to tetragonal Mn 3O 4 to spinel LiMn 2O 4. The first reaction step involves topotactic exchange of interlayer Na + by Li + in solution followed by thermal treatments to crystal engineer the –10–nm–thick 2D layered oxide throughout the macroscale nanofoam paper into a spinel phase. The oxide remains affixed to the walls of the nanofoam throughout the phase transformations. The DPDF fits are improved by retention of one plane of birnessite–like oxide after conversion to spinel. We support the DPDF–derived assignments by X–ray photoelectron spectroscopy and Raman spectroscopy, the latter of which tracks how crystal engineering the oxide affects the disorder of the carbon substrate. We further benchmark MnOx@CNF with nonaqueous electrochemical measurements versus lithium as the oxide converts from X–ray–amorphous birnessite to interlayer-registered LiMnOx to spinel. The lamellar AMnOx displays pseudocapacitive electrochemical behavior, withmore » a doubling of specific capacitance for the interlayer–registered LiMnOx, while the spinel LiMn 2O 4@CNF displays a faradaic electrochemical response characteristic of Li–ion insertion. Our results highlight the need for holistic understanding when crystal engineering an (atomistic) charge–storing phase within the (architectural) structure of practical electrodes.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [3] ;  [3]
  1. Postdoctoral Associate of the National Research Council (NRC), Washington, D.C. (United States); U.S. Naval Research Lab., Washington, D.C. (United States)
  2. U.S. Naval Research Lab., Washington, D.C. (United States); Nova Research, Inc., Alexandria, VA (United States)
  3. U.S. Naval Research Lab., Washington, D.C. (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
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Accepted Manuscript
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Additional Journal Information:
Journal Volume: 18; Journal Issue: 32; Journal ID: ISSN 1466-8033
Royal Society of Chemistry
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
US Department of the Navy, Office of Naval Research (ONR); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Country of Publication:
United States