Browsing by Author "Zhang, WL"

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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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    A niobium oxide with shear structure and planar defects for high-power lithium ion batteries
    (Royal Society of Chemistry, 2021-11-16) Li, TT; Nam, G; Liu, KT; Wang, JH; Zhao, B; Ding, Y; Soule, L; Avdeev, M; Luo, Z; Zhang, WL; Yuan, T; Jing, PP; Kim, MG; Song, YY; Liu, ML
    The development of anode materials with high-rate capability is critical to high-power lithium batteries. T-Nb2O5 has been widely reported to exhibit pseudocapacitive behavior and fast lithium storage capability. However, the other polymorphs of Nb2O5 prepared at higher temperatures have the potential to achieve even higher specific capacity and tap density than T-Nb2O5, offering higher volumetric power and energy density. Here, micrometer-sized H-Nb2O5 with rich Wadsley planar defects (denoted as d-H-Nb2O5) is designed for fast lithium storage. The performance of H-Nb2O5 with local rearrangements of [NbO6] octahedra blocks surpasses that of T-Nb2O5 in terms of specific capacity, rate capability, and stability. A wide range variation in valence of niobium ions upon lithiation was observed for defective H-Nb2O5 via operando X-ray absorption spectroscopy. Operando extended X-ray absorption fine structure and ex-situ Raman spectroscopy reveals a large and reversible distortion of the structure in the two-phase region. Computation and ex-situ X-ray diffraction analysis reveals that the shear structure expands along major lithium diffusion pathways and contracts in the direction perpendicular to the shear plane. Planar defects relieve strain through perpendicular arrangements of blocks, minimizing volume change and enhancing structural stability. In addition, strong Li adsorption on planar defects enlarges intercalation capacity. Different from nanostructure engineering, our strategy to modify the planar defects in the bulk phase can effectively improve the intrinsic property. The findings in this work offer new insights into designing fast Li-ion storage materials in micrometer sizes through defect engineering, and the strategy is applicable to the material discovery for other energy-related applications. © Royal Society of Chemistry 2021