Browsing by Author "Ren, Yang"
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- Effect of the grain arrangements on the thermal stability of polycrystalline nickel-rich lithium-based battery cathodesHou, Dong; Xu, Zhengrui; Yang, Zhijie; Kuai, Chunguang; Du, Zhijia; Sun, Cheng-Jun; Ren, Yang; Liu, Jue; Xiao, Xianghui; Lin, Feng (Springer, 2022-06-15)One of the most challenging aspects of developing high-energy lithium-based batteries is the structural and (electro)chemical stability of Ni-rich active cathode materials at thermally-abused and prolonged cell cycling conditions. Here, we report in situ physicochemical characterizations to improve the fundamental understanding of the degradation mechanism of charged polycrystalline Ni-rich cathodes at elevated temperatures (e.g., ≥ 40 °C). Using multiple microscopy, scattering, thermal, and electrochemical probes, we decouple the major contributors for the thermal instability from intertwined factors. Our research work demonstrates that the grain microstructures play an essential role in the thermal stability of polycrystalline lithium-based positive battery electrodes. We also show that the oxygen release, a crucial process during battery thermal runaway, can be regulated by engineering grain arrangements. Furthermore, the grain arrangements can also modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered oxide cathode materials.
- A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-xLiNbO3 solid solutionGe, Wenwei; Ren, Yang; Zhang, Jialiang; Devreugd, Christopher P.; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-05-15)A monoclinic ferroelectric phase with space group Pm has been discovered in lead-free (K0.5Na0.5)NbO3-5%LiNbO3 solid solution ceramics by high energy synchrotron x-ray powder diffraction measurements. At ambient temperature, the lattice parameters of this monoclinic structure were (a(m), b(m), c(m); beta) = (4.015 angstrom, 3.944 angstrom, 3.987 angstrom; 90.34 degrees). This monoclinic phase transformed to a tetragonal (P4mm) one on heating between 340 K and 360K. The results demonstrate the presence of structurally bridging low symmetry monoclinic phase in (K0.5Na0.5)NbO3-x%LiNbO3 solid solution system: indicating a means to achieve high piezoelectricity in Pb-free systems via domain engineering. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4716027]
- Regulating the Hidden Solvation-Ion-Exchange in Concentrated Electrolytes for Stable and Safe Lithium Metal BatteriesAmine, Rachid; Liu, Jianzhao; Acznik, Ilona; Sheng, Tian; Lota, Katarzyna; Sun, Hui; Sun, Cheng-Jun; Fic, Krzysztof; Zuo, Xiaobing; Ren, Yang; Abd El-Hady, Deia; Alshitari, Wael; Al-Bogami, Abdullah S.; Chen, Zonghai; Amine, Khalil; Xu, Gui-Liang (2020-07)Lithium-sulfur batteries are attractive for automobile and grid applications due to their high theoretical energy density and the abundance of sulfur. Despite the significant progress in cathode development, lithium metal degradation and the polysulfide shuttle remain two critical challenges in the practical application of Li-S batteries. Development of advanced electrolytes has become a promising strategy to simultaneously suppress lithium dendrite formation and prevent polysulfide dissolution. Here, a new class of concentrated siloxane-based electrolytes, demonstrating significantly improved performance over the widely investigated ether-based electrolytes are reported in terms of stabilizing the sulfur cathode and Li metal anode as well as minimizing flammability. Through a combination of experimental and computational investigation, it is found that siloxane solvents can effectively regulate a hidden solvation-ion-exchange process in the concentrated electrolytes that results from the interactions between cations/anions (e.g., Li+, TFSI-, and S2-) and solvents. As a result, it could invoke a quasi-solid-solid lithiation and enable reversible Li plating/stripping and robust solid-electrolyte interphase chemistries. The solvation-ion-exchange process in the concentrated electrolytes is a key factor in understanding and designing electrolytes for other high-energy lithium metal batteries.
- Resolving atomic-scale phase transformation and oxygen loss mechanism in ultrahigh-nickel layered cathodes for cobalt-free lithium-ion batteriesWang, Chunyang; Han, Lili; Zhang, Rui; Cheng, Hao; Mu, Linqin; Kisslinger, Kim; Zou, Peichao; Ren, Yang; Cao, Penghui; Lin, Feng; Xin, Huolin L. (2021-06-02)Doped LiNiO2 has recently become one of the most promising cathode materials for its high specific energy, long cycle life, and reduced cobalt content. Despite this, the degradation mechanism of LiNiO2 and its derivatives still remains elusive. Here, by combining in situ electron microscopy and first-principles calculations, we elucidate the atomic-level chemomechanical degradation pathway of LiNiO2-derived cathodes. We uncover that the O1 phase formed at high voltages acts as a preferential site for rock-salt transformation via a two-step pathway involving cation mixing and shear along (003) planes. Moreover, electron tomography reveals that planar cracks nucleated simultaneously from particle interior and surface propagate along the [100] direction on (003) planes, accompanied by concurrent structural degradation in a discrete manner. Our results provide an in-depth understanding of the degradation mechanism of LiNiO2-derived cathodes, pointing out the concept that suppressing the O1 phase and oxygen loss is key to stabilizing LiNiO2 for developing next-generation high-energy cathode materials.
- Spatial and Temporal Analysis of Sodium-Ion BatteriesHou, Dewen; Xia, Dawei; Gabriel, Eric; Russell, Joshua A.; Graff, Kincaid; Ren, Yang; Sun, Cheng-Jun; Lin, Feng; Liu, Yuzi; Xiong, Hui (American Chemical Society, 2021-11-12)As a promising alternative to the market-leading lithiumion batteries, low-cost sodium-ion batteries (SIBs) are attractive for applications such as large-scale electrical energy storage systems. The energy density, cycling life, and rate performance of SIBs are fundamentally dependent on dynamic physiochemical reactions, structural change, and morphological evolution. Therefore, it is essential to holistically understand SIBs reaction processes, degradation mechanisms, and thermal/mechanical behaviors in complex working environments. The recent developments of advanced in situ and operando characterization enable the establishment of the structure-processing-property- performance relationship in SIBs under operating conditions. This Review summarizes significant recent progress in SIBs exploiting in situ and operando techniques based on X-ray and electron analyses at different time and length scales. Through the combination of spectroscopy, imaging, and diffraction, local and global changes in SIBs can be elucidated for improving materials design. The fundamental principles and state-of-the-art capabilities of different techniques are presented, followed by elaborative discussions of major challenges and perspectives.
- Ultrahigh electromechanical response in (1-x)(Na0.5Bi0.5)TiO3-xBaTiO(3) single-crystals via polarization extensionGe, Wenwei; Luo, Chengtao; Zhang, Qinhui; Devreugd, Christopher P.; Ren, Yang; Li, Jiefang; Luo, Haosu; Viehland, Dwight D. (American Institute of Physics, 2012-05-01)The dielectric, ferroelectric, and electric field-induced strain response of [001]-and [101]-oriented 0.944Na(0.5)Bi(0.5)TiO(3)-0.056BaTiO(3) (0.944NBT-0.056BT) single crystals were investigated as a function of temperature and dc bias (E). An ultrahigh electromechanical response with large amplitude longitudinal piezoelectric coefficients as high as d(33)=2500 pm/V was found in [001](PC) oriented 0.944NBT-0.056BT single crystals near a depolarization temperature of T-d = 130 degrees C. In-situ XRD revealed that the enhanced piezoelectric properties resulted from a polarization extension between a polar pseudocubic phase with a slight tetragonal (P4bm) distortion and a polar tetragonal one with a large tetragonal distortion of c/a = 1.02. Our findings indicate a potential approach to high performance lead-free piezoelectrics, via polarization extension. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709619]