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Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	Free-spin dominated magnetocaloric effect in dense Gd3+double perovskites Eliseanne C. Koskelo , Cheng Liu , Paromita Mukherjee , Nicola D. Kelly , Sian E. Dutton Chemistry Of Materials DOI: 10.1021/acs.chemmater.2c00261 Diamond Proposal Number(s): [28349] Show Abstract ▼ Abstract: Frustrated lanthanide oxides with dense magnetic lattices are of fundamental interest for their potential in cryogenic refrigeration due to a large ground state entropy and suppressed ordering temperatures but can often be limited by short-range correlations. Here, we present examples of frustrated fcc oxides, Ba2GdSbO6 and Sr2GdSbO6, and the new site-disordered analogue Ca2GdSbO6 ([CaGd]A[CaSb]BO6), in which the magnetocaloric effect is influenced by minimal superexchange (J1 ∼ 10 mK). We report on the crystal structures using powder X-ray diffraction and the bulk magnetic properties through low-field susceptibility and isothermal magnetization measurements. The Gd compounds exhibit a magnetic entropy change of up to −15.8 J/K/molGd in a field of 7 T at 2 K, a 20% excess compared to the value of −13.0 J/K/molGd for a standard in magnetic refrigeration, Gd3Ga5O12. Heat capacity measurements indicate a lack of magnetic ordering down to 0.4 K for Ba2GdSbO6 and Sr2GdSbO6, suggesting cooling down through the liquid 4-He regime. A mean-field model is used to elucidate the role of primarily free-spin behavior in the magnetocaloric performance of these compounds in comparison to other top-performing Gd-based oxides. The chemical flexibility of the double perovskites raises the possibility of further enhancement of the magnetocaloric effect in the Gd3+fcc lattices.	Mar 2022
I11-High Resolution Powder Diffraction	Sample dependence of magnetism in the next-generation cathode material LiNi0.8Nn0.1Co0.1O2 Paromita Mukherjee , Joseph A. M. Paddison , Chao Xu , Zachary Ruff , Andrew R. Wildes , David A. Keen , Ronald I. Smith , Clare P. Grey , Sian E. Dutton Inorganic Chemistry DOI: 10.1021/acs.inorgchem.0c02899 Diamond Proposal Number(s): [25186] Show Abstract ▼ Abstract: We present a structural and magnetic study of two batches of polycrystalline LiNi0.8Mn0.1Co0.1O2 (commonly known as Li NMC 811), a Ni-rich Li ion battery cathode material, using elemental analysis, X-ray and neutron diffraction, magnetometry, and polarized neutron scattering measurements. We find that the samples, labeled S1 and S2, have the composition Li1–xNi0.9+x–yMnyCo0.1O2, with x = 0.025(2), y = 0.120(2) for S1 and x = 0.002(2), y = 0.094(2) for S2, corresponding to different concentrations of magnetic ions and excess Ni2+ in the Li+ layers. Both samples show a peak in the zero-field-cooled (ZFC) dc susceptibility at 8.0(2) K, but the temperature at which the ZFC and FC (field-cooled) curves deviate is substantially different: 64(2) K for S1 and 122(2) K for S2. The ac susceptibility measurements show that the transition for S1 shifts with frequency whereas no such shift is observed for S2 within the resolution of our measurements. Our results demonstrate the sample dependence of magnetic properties in Li NMC 811, consistent with previous reports on the parent material LiNiO2. We further establish that a combination of experimental techniques is necessary to accurately determine the chemical composition of next-generation battery materials with multiple cations.	Dec 2020
I09-Surface and Interface Structural Analysis	Surface degradation of Li1–xNi0.80Co0.15Al0.05O2 cathodes: Correlating charge transfer impedance with surface phase transformations Shawn Sallis , N. Pereira , P. Mukherjee , Nicholas Quackenbush , N. Faenza , Christoph Schlueter , Tien-Lin Lee , W. L. Yang , F. Cosandey , G. G. Amatucci , Louis Piper Applied Physics Letters 108 DOI: 10.1063/1.4954800 Diamond Proposal Number(s): [12764] Show Abstract ▼ Abstract: The pronounced capacity fade in Ni-rich layered oxide lithium ion battery cathodes observed when cycling above 4.1 V (versus Li/Li+) is associated with a rise in impedance, which is thought to be due to either bulk structural fatigue or surface reactions with the electrolyte (or combination of both). Here, we examine the surface reactions at electrochemically stressed Li1– x Ni 0.8Co0.15Al0.05O2 binder-free powder electrodes with a combination of electrochemical impedance spectroscopy, spatially resolving electron microscopy, and spatially averaging X-ray spectroscopy techniques. We circumvent issues associated with cycling by holding our electrodes at high states of charge (4.1 V, 4.5 V, and 4.75 V) for extended periods and correlate charge-transfer impedance rises observed at high voltages with surface modifications retained in the discharged state (2.7 V). The surface modifications involve significant cation migration (and disorder) along with Ni and Co reduction, and can occur even in the absence of significant Li2CO3 and LiF. These data provide evidence that surface oxygen loss at the highest levels of Li+ extraction is driving the rise in impedance.	Jun 2016

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