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

Journal Article · Fri Jun 17 00:00:00 EDT 2016 · CrystEngComm

DOI:https://doi.org/10.1039/c6ce00861e· OSTI ID:1346731

Donakowski, Martin D. ^[1]; Wallace, Jean M. ^[2]; Sassin, Megan B. ^[3]; Chapman, Karena W. ^[4]; Parker, Joseph F. ^[3]; Long, Jeffrey W. ^[3]; Rolison, Debra R. ^[3]

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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)

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 Mn₃O₄ to spinel LiMn₂O₄. 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, with a doubling of specific capacitance for the interlayer–registered LiMnOx, while the spinel LiMn₂O₄@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.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: US Department of the Navy, Office of Naval Research (ONR); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1346731
• Journal Information: CrystEngComm, Vol. 18, Issue 32; ISSN 1466-8033
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY