Supporting Information Yb 0.0061 (6) 0.0093 (6) 0.0085 (6) 0.0017 (7) 0.000 0.000 Pd1 0.0048 (6) 0.0098 (5) 0.0099 (7) 0.000 0.000 0.0009 (4) Pd2 0.0061 (9) 0.0102 (9) 0.0058 (11) 0.000 0.000 −0.0016 (8) Ga1 0.0037 (6) 0.0091 (6) 0.0172 (8) 0.0003 (6) 0.0010 (8) 0.0004 (5) Ga2 0.0071 (11) 0.0103 (9) 0.0112 (12) 0.000 0.000 0.0001 (9) Ga3 0.015 (4) 0.014 (3) 0.021 (4) 0.003 (3) 0.000 0.000 Ga4 0.015 (6) 0.012 (5) 0.016 (6) 0.000 0.000 0.000 Yb(a) 0.0029 (10) 0.0097 (11) 0.0076 (10) 0.000 0.000 0.000 Ga3(a) 0.008 (4) 0.007 (3) 0.005 (4) −0.003 (3) 0.000 0.000 Ga3(b) 0.002 (4) 0.015 (4) 0.012 (4) −0.005 (3) 0.000 0.000 Ga4(a) 0.001 (3) 0.009 (3) 0.005 (3) −0.010 (3) 0.000

Synthetic control of the silver content in silver hollandite, AgxMn8O16, where the silver content ranges from 1.0 ≤ × ≤ 1.8 is demonstrated. This level of compositional control was enabled by the development of a lower temperature reflux based synthesis compared to the more commonly reported hydrothermal approach. Notably, the synthetic variance of the silver content was accompanied by a concomitant variance in crystallite size as well as surface area and particle size. In order to verify the retention of the hollandite structure, the first Rietveld analysis of silver hollandite was conducted on samples of varying composition. The impacts of silver content, crystallite size, surface area, and particle size on electrochemical reversibility were examined under cyclic voltammetry and battery testing.

Energy dispersive X-ray diffraction (EDXRD) with photons of high energy and high flux is used to map crystalline discharge products within alkaline AA cells following discharge at various rates: C/160, C/80, C/40, C/20, C/10, and C/5. During the study, the sealed cells are never opened and thus never exposed to air. The technique's resolution allows the various manganese oxide discharge products to be distinguished, which has previously proven difficult. In particular, colocalized Mn 3 O 4 (hausmannite) and ZnMn 2 O 4 (hetaerolite) phases are resolved at C/160, C/80, and C/40 rates. Following more rapid discharge at C/20, no hausmannite is observed: instead, two well-defined zones result, one consisting only of hetaerolite, and the other only of α-MnOOH (groutite), with a small transition region where both phases are detected. Modeling suggests the observed hetaerolite-groutite boundary positions are consistent with hetaerolite formation in regions of greater active material utilization. Radial hetaerolite and hausmannite profiles are calculated and found to be a function of the discharge current, which also determines discharge capacity. Results also show formation of a α-MnOOH phase from oxidation states MnO 1.7 to MnO 1.53 with relatively little γ-MnOOH character.The Zn-MnO 2 alkaline chemistry has been a staple of portable, high energy density batteries for half a century. Currently there is also interest in using this chemistry for large-scale storage, as the basis materials are safe and inexpensive at scale. At low depth of discharge (DOD) the ε(γ)-MnO 2 discharge product is MnOOH, which forms in the MnO 2 crystal lattice, creating a continuous, non-stoichiometric solid solution of MnO 2 and MnOOH. 1 However, as the MnOOH fraction increases and it becomes the majority component, an array of other lower oxides form such as Mn(OH) 2 and Mn 3 O 4 . While Mn(OH) 2 is considered a reversible product, meaning it can be reoxidized to MnO 2 , Mn 3 O 4 is not reversible and is therefore a discharge end-product. Mn 3 O 4 is known as hausmannite, a stable spinel-type material. Hetaerolite or ZnMn 2 O 4 is a spinel structure as is hausmannite, with a zinc atom replacing the divalent manganese atom. 2-7 In Zn-MnO 2 batteries, hetaerolite is also formed, as the anode is a source of zinc ions. 8-11 Both hausmannite and hetaerolite have resistivities six orders of magnitude higher than the active material MnO 2 , around 10 8 ohm-cm, and can lead to a loss of conductivity in the electrode and therefore failure. 12-14 Hetaerolite is known to limit MnO 2 discharge in the second electron regime, therefore limiting the capacity of Zn-MnO 2 batteries.The reaction pathways relating the myriad manganese oxide discharge products, listed in Table I, are not fully understood despite being a subject of interest for decades. The reasons for continued persistence toward eliminating this mystery are the desires to 1) increase cycle life of the system and to 2) increase available capacity for primary applications. When discharged cathodes...

Single crystals of MAl2S4 (M = Mn2+, Fe2+, Co2+) were synthesized using the chemical vapor transport method and characterized using high-resolution synchrotron X-ray diffraction to determine the structure. All the compounds have a layered slab structure separated by a van der Waals gap, which results in highly two-dimensional magnetism. Magnetic susceptibility measurements indicate spin-glass behavior below T* values of ∼2 K, ∼ 10.5 K, and ∼5 K for MAl2S4 (M = Mn2+, Fe2+, Co2+), respectively, and heat capacity measurements indicate no long-range magnetic ordering observed down to 0.4 K. These results can be attributed primarily to site disorder due to mixing of M2+ and Al3+ ions (M = Mn2+, Fe2+, Co2+) and low dimensionality with geometrical frustration also playing a role. Interestingly, MnAl2S4, with almost isotropic S = 5/2 spin, has the highest frustration parameter among the series of compounds and is a possible candidate for a two-dimensional Heisenberg spin glass system.

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Silver vanadium phosphorous oxides (AgwVxPyOz) are notable battery cathode materials due to their high energy density and demonstrated ability to form in-situ Ag metal nanostructured electrically conductive networks within the cathode. While analogous silver vanadium diphosphate materials have been prepared, electrochemical evaluations of these diphosphate based materials have been limited. We report here the first electrochemical study of a silver vanadium diphosphate, Ag2VP2O8, where the structural differences associated with phosphorous oxides versus diphosphates profoundly affect the associated electrochemistry. Reminiscent of Ag2VO2PO4 reduction, in-situ formation of silver metal nanoparticles was observed with reduction of Ag2VP2O8. However, counter to Ag2VO2PO4 reduction, Ag2VP2O8 demonstrates a significant decrease in conductivity upon continued electrochemical reduction. Structural analysis contrasting the crystallography of the parent Ag2VP2O8 with that of the proposed Li2VP2O8 reduction product is employed to gain insight into the observed electrochemical reduction behavior, where the structural rigidity associated with the diphosphate anion may be associated with the observed particle fracturing upon deep electrochemical reduction. Further, the diphosphate anion structure may be associated with the high thermal stability of the partially reduced Ag2VP2O8 materials, which bodes well for enhanced safety of batteries incorporating this material.

Magnetite (Fe3O4) is an abundant, low cost, environmentally benign material with potential application in batteries. Recently, low temperature coprecipitation methods have enabled preparation of a series of nanocrystalline magnetite samples with a range of crystallite sizes. Electrochemical cells based on Li/Fe3O4 show a linear increase in capacity with decreasing crystallite size at voltages ≥1.2 V where a 2× capacity improvement relative to commercial (26.2 nm) magnetite is observed. In this report, a combination of X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) is used to measure magnetite structural changes occurring upon electrochemical reduction, with parent Fe3O4 crystallite size as a variable. Notably, XAS provides evidence of metallic iron formation at high levels of electrochemical reduction.

We report temperature and thermal-cycling dependence of surface and bulk structures of double-layered perovskite Sr 3 Ru 2 O 7 single crystals. The surface and bulk structures were investigated using low-energy electron diffraction (LEED) and single-crystal X-ray diffraction (XRD) techniques, respectively. Single-crystal XRD data is in good agreement with previous reports for the bulk structure with RuO 6 octahedral rotation, which increases with decreasing temperature (~ 6.7(6) at 300 K and ~ 8.1(2) at 90 K). LEED results reveal that the octahedra at the surface are much more distorted with a higher rotation angle (~ 12 between 300 and 80 K) and a slight tilt ((4.5±2.5) at 300 K and (2.5±1.7) at 80 K). While XRD data confirms temperature dependence of the unit cell height/width ratio (i.e. lattice parameter c divided by the average of parameters a and b) found in a prior neutron powder diffraction investigation, both bulk and surface structures display little change with thermal cycles between 300 and 80 K. PACS number(s): 61.05.cp, 61.05.jh, 68.47.Gh Page 2 of 25The ruthenate Ruddlesden-Popper (RP) series Sr n+1 Ru n O 3n+1 (n = 1, 2, 3, …) exhibit rich electronic and magnetic properties covering a range from diamagnetic superconductor 1 (n = 1) to paramagnetic conductor with antiferromagnetic (AFM) correlation 2 (n = 2) to ferromagnetic (FM) metal 3,4 (n = 3, ∞). Extensive studies on the single-layered (n = 1) Sr 2 RuO 4 and the isovalently doped (Sr,Ca) 2 RuO 4 system reveal that the lattice degree of freedom plays a critical role in their physical properties, both in bulk 5,6 and on the surface 7,8,9 . Theoretical calculations 10 also indicate that the rotation and tilt of RuO 6 octahedra in (Sr,Ca) 2 RuO 4 are closely coupled to the ferromagnetism and antiferromagnetism, respectively. Therefore, precise determination of the structural properties of the RP series is the key towards understanding of their exotic physical properties.The motivation for investigating the structural properties of double-layered (n = 2) Sr 3 Ru 2 O 7 is multifold. First of all, it displays unique physical properties, different from the rest of the RP series. Although there is no long-range magnetic ordering under ambient pressure, a short-range AFM-type correlation develops below ~ 20 K, as probed by magnetic susceptibility 2,11 and neutron scattering measurements 12 . Application of hydrostatic and uni-axial pressure can drive the system into a ferromagnetically ordered state 11,13 . The application of magnetic field leads to similar result -the system undergoes a metamagnetic transition 14 . These clearly indicate that the system has two competing magnetic interactions (AFM versus FM), which are coupled with the structural properties. Second, the bulk crystal structure of Sr 3 Ru 2 O 7 has been modeled after data collection with various diffraction techniques into three different space groups since the first report in 1990 15 . The space groups reported include I4/mmm (tetragonal, No. 139) [15][16][17] Pban (...