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35 results on '"Hu, Qingmiao"'

13. Si‐Based High‐Entropy Anode for Lithium‐Ion Batteries

Author

Lei, Xincheng, primary, Wang, Yingying, additional, Wang, Jiayi, additional, Su, Yi, additional, Ji, Pengxiang, additional, Liu, Xiaozhi, additional, Guo, Shengnan, additional, Wang, Xuefeng, additional, Hu, Qingmiao, additional, Gu, Lin, additional, Zhang, Yuegang, additional, Yang, Rui, additional, Zhou, Gang, additional, and Su, Dong, additional

Published
2023
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16. Si‐Based High‐Entropy Anode for Lithium‐Ion Batteries.

Author

Lei, Xincheng, Wang, Yingying, Wang, Jiayi, Su, Yi, Ji, Pengxiang, Liu, Xiaozhi, Guo, Shengnan, Wang, Xuefeng, Hu, Qingmiao, Gu, Lin, Zhang, Yuegang, Yang, Rui, Zhou, Gang, and Su, Dong

Subjects
LITHIUM-ion batteries, ANODES, TRANSMISSION electron microscopy, ENERGY density, STRUCTURAL stability, TRANSITION metals
Abstract

Up to now, only a small portion of Si has been utilized in the anode for commercial lithium‐ion batteries (LIBs) despite its high energy density. The main challenge of using micron‐sized Si anode is the particle crack and pulverization due to the volume expansion during cycling. This work proposes a type of Si‐based high‐entropy alloy (HEA) materials with high structural stability for the LIB anode. Micron‐sized HEA‐Si anode can deliver a capacity of 971 mAhg−1 and retains 93.5% of its capacity after 100 cycles. In contrast, the silicon–germanium anode only retains 15% of its capacity after 20 cycles. This study has discovered that including HEA elements in Si‐based anode can decrease its anisotropic stress and consequently enhance ductility at discharged state. By utilizing in situ X‐ray diffraction and transmission electron microscopy analyses, a high‐entropy transition metal doped Lix(Si/Ge) phase is found at lithiated anode, which returns to the pristine HEA phase after delithiation. The reversible lithiation and delithiation process between the HEA phases leads to intrinsic stability during cycling. These findings suggest that incorporating high‐entropy modification is a promising approach in designing anode materials toward high‐energy density LIBs. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Chemical Origin of Termination-Functionalized MXenes: Ti3C2T2as a Case Study

Author

Hu, Tao, Li, Zhaojin, Hu, Minmin, Wang, Jiemin, Hu, Qingmiao, Li, Qingzhong, and Wang, Xiaohui

Abstract

MXenes represent a burgeoning family of two-dimensional (2D) functional materials with a variety of applications that highly rely on termination-mediated surface functionalization, but the understanding of termination is limited. Here, we take Ti3C2T2(T= O, F, OH, and H) as an example of MXenes, to demonstrate how termination stabilizes the Ti3C2monolayer matrix by saturating the nonbonding valence electrons of the surface Ti atom by the low-energy orbitals of the termination. This is achieved by orbitally resolved density of states analysis by simply yet efficiently manipulating the internal coordination of the octahedral crystal field to match exactly the Cartesian coordination. Highly degenerate 3d orbitals of surface Ti split in such a way that it exhibits pseudogaps whose widths predict a stability order Ti3C2O2> Ti3C2F2> Ti3C2(OH)2> Ti3C2H2> Ti3C2, consistent with Bader charge analysis, thermodynamic calculations, and experimental results. This new criterion could have implications in the general context of ubiquitous termination phenomena of MXenes and other relevant termination-functionalized 2D materials.

Published
2017
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35. Composition dependent elastic modulus and phase stability of Ni2MnGa based ferromagnetic shape memory alloys

Author

Hu, QingMiao, Luo, HuBin, Li, ChunMei, Vitos, Levente, and Yang, Rui

Abstract

Abstract: Ni2MnGa based ferromagnetic alloys are ideal candidates for applications such as actuators, magnetic refrigerators or magnetostrictive transducers due to their attractive properties such as magnetic field induced shape memory effect and large magnetocaloric effect. The properties of these alloys (e.g., the martensitic transformation temperature T M ) sensitively depend on the composition. Understanding the composition dependence of these properties so as to design the alloy as desired is one of the main research topics in this area. In recent years, we have investigated the composition dependent elastic modulus and phase stability of Ni2MnGa-based alloys by using a first-principles method, in hope of clarifying their connection to the properties of these alloys. In this article, we review the main results of our investigations. We show that the tetragonal shear modulus C′ is a better predictor of the composition dependent T M than the number of valence electrons per atom (e/a) since the general T M ∼C′ correlation works for some of the alloys for which the T M ∼e/a correlation fails, although there exist several cases for which both the general T M ∼C′ and T M ∼e/a correlations break down. Employing the experimentally determined modulation function, the complex 5-layer modulated (5M) structure of the martensite of Ni2MnGa and the Al-doping effect on it are studied. We find that the shuffle and shear of the 5M structure are linearly coupled. The relative stability of the austenite and the martensites is examined by comparing their total energies. The non-modulated martensite β″′ with the tetragonality of the unit cell c/a>1 is shown to be globally stable whereas the 5M martensite with c/a<1 is metastable. The critical Al atomic fraction over which the martensitic transformation between the 5M martensite and austenite cannot occur is predicted to be 0.26, in reasonable agreement with experimental findings.

Published
2012
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