Browsing by Author "Navrotsky, A"

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    Marinite Li2Ni(SO4)2 as a new member of the bisulfate family of high-voltage lithium battery cathodes
    (American Chemical Society, 2021-07-31) Singh, S; Jha, PK; Avdeev, M; Zhang, WL; Jayanthi, K; Navrotsky, A; Alshareef, HM; Barpanda, P
    Development of sustainable, economic, and high-voltage cathode materials forms the cornerstone of cathode design for Li-ion batteries. Sulfate chemistry offers a fertile ground to discover high-voltage cathode materials stemming from a high electronegativity-based inductive effect. Herein, we have discovered a new polymorph of high-voltage m-Li2NiII(SO4)2 bisulfate using a scalable spray drying route. Neutron and synchrotron diffraction analysis revealed a monoclinic structure (s.g. P21/c, #14) built from corner-shared NiO6 octahedra and SO4 tetrahedra locating all Li+ in a distinct site. Low-temperature magnetic susceptibility and neutron diffraction measurements confirmed long-range A-type antiferromagnetic ordering in m-Li2NiII(SO4)2 below 15.2 K following the Goodenough–Kanamori–Anderson rule. In situ X-ray powder diffraction displayed an irreversible (monoclinic → orthorhombic) phase transformation at ∼400 °C. The m-Li2NiII(SO4)2 framework offers two-dimensional Li+ migration pathways as revealed by the bond valence site energy (BVSE) approach. The electronic structure obtained using first-principles (DFT) calculation shows a large electronic band gap (Eg ∼ 3.8 eV) with a trapped state near the Fermi energy level triggering polaronic conductivity. As per the DFT study, m-Li2NiII(SO4)2 can work as a 5.5 V (vs Li+/Li0) cathode for Li-ion batteries, with suitable electrolytes, coupling both cationic (NiII/III) and anionic (O–) redox activity. © 2021 American Chemical Society
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    Materials science of high-level nuclear waste immobilization
    (Materials Research Society, 2009-01) Weber, WJ; Navrotsky, A; Stefanovsky, S; Vance, ER; Vernaz, E
    With the increasing demand for the development of nuclear power comes the responsibility to address the issue of waste, including the technical challenges of immobilizing high-level nuclear wastes in stable solid forms for interim storage or disposition in geologic repositories. The immobilization of high-level nuclear wastes has been an active area of research and development for over 50 years. Borosilicate glasses and complex ceramic composites have been developed to meet many technical challenges and current needs, although regulatory issues, which vary widely from country to country, have yet to be resolved. Cooperative international programs to develop advanced proliferation-resistant nuclear technologies to close the nuclear fuel cycle and increase the efficiency of nuclear energy production might create new separation waste streams that could demand new concepts and materials for nuclear waste immobilization. This article reviews the current state-of-the-art understanding regarding the materials science of glasses and ceramics for the immobilization of high-level nuclear waste and excess nuclear materials and discusses approaches to address new waste streams. © 2009, Materials Research Society