Effects of Proton Irradiation on Structural and Electrochemical Charge Storage Properties of TiO\u3csub\u3e2 \u3c/sub\u3eNanotube Electrode for Lithium-Ion Batteries

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material’s electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradiation as it can produce a supersaturation of point defects in the target material. In this work we report the effect of low-energy proton irradiation on amorphous TiO2 nanotube electrodes at both room temperature and high temperature (250 ˚C). Upon room temperature irradiation the nanotubes demonstrate an irradiation-induced phase transformation to a mixture of amorphous, anatase, and rutile domains while showing a 35% reduction in capacity compared to anatase TiO2. On the other hand, the high temperature proton irradiation induced a disordered rutile phase within the nanotubes as characterized by Raman spectroscopy and transmission electron microscopy, which displays an improved capacity by 20% at ~ 240 mAh g-1 as well as improved rate capability compared to unirradiated anatase sample. Voltammetric sweep data was used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation has more contributions from diffusion in lithium charge storage. Our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for design of advanced electrode materials

Amorphous Boron Nanorod as an Anode Material for Lithium-Ion Batteries at Room Temperature

We report an amorphous boron nanorod anode material for lithium-ion batteries prepared through smelting non-toxic boron oxide in liquid lithium. Boron in theory can provide capacity as high as 3099 mAh g-1 by alloying with Li to form B4Li5. However, experimental studies of boron anode were rarely reported for room temperature lithium-ion batteries. Among the reported studies the electrochemical activity and cycling performance of bulk crystalline boron anode material are poor at room temperature. In this work, we utilized amorphous nanostructured one-dimensional (1D) boron material aiming at improving the electrochemical reactivity between boron and lithium ions at room temperature. The amorphous boron nanorod anode exhibited, at room temperature, a reversible capacity of 170 mAh g-1 at a current rate of 10 mA g-1 between 0.01 and 2 V. The anode also demonstrated good rate capability and cycling stability. Lithium storage mechanism was investigated by both sweep voltammetry measurements and galvanostatic intermittent titration technique (GITT). The sweep voltammetric analysis suggested that the contributions from lithium ions diffusion into boron as well as the capacitive process to the overall lithium charge storage are 57% and 43%, respectively. Results from GITT indicated that the discharge capacity at higher potentials (\u3e ~ 0.2 V vs, Li/Li+) could be ascribed to a capacitive process and at lower potentials (\u3c ~0.2 V vs, Li/Li+) to diffusion-controlled alloying reactions. Solid state nuclear magnetic resonance (NMR) measurement further confirmed that the capacity is from electrochemical reactions between lithium ions and the amorphous boron nanorod. This work provides new insights into designing nanostructured boron material for lithium-ion batteries

Theoretical understanding of correlation between magnetic phase transition and the superconducting dome in high-Tc cuprates

Many issues concerning the origin of high-temperature superconductivity (HTS) are still under debate. For example, how the magnetic ordering varies with doping and its relationship with the superconducting temperature; and why the maximal Tc always occurs near the quantum critical point. In this paper, taking hole-doped La2CuO4 as a classical example, we employ the first-principles band structure and total energy calculations and Monte Carlo simulations to explore how the symmetry-breaking magnetic ground state evolves with hole doping and the origin of a dome-shaped superconductivity region in the phase diagram. We demonstrate that the local antiferromagnetic ordering and doping play key roles in determining the electron-phonon coupling, thus Tc. Initially, the La2CuO4 possesses a checkerboard local antiferromagnetic ground state. As the hole doping increases, Tc increases with the increase of the density of states at the Fermi surface. But as the doping increases further, the strength of the antiferromagnetic interaction weakens. At the critical doping level, a magnetic phase transition occurs that reduces the local antiferromagnetism-assisted electron-phonon coupling, thus diminishing the Tc. The superconductivity disappears in the heavily overdoped region when the antiferromagnetic ordering disappears. These observations could account for why cuprates have a dome-shaped superconductivity region in the phase diagram. Our study, thus, contributes to a fundamental understanding of the correlation between doping, local magnetic ordering, and superconductivity of HTS.Comment: 14 pages, 3 figures in the main text; 11 pages, 7 figures in the supplementary material

Carbon-Coated FeP Nanoparticles Anchored on Carbon Nanotube Networks as Anode for Long-Life Sodium-Ion Storage

A novel electrode design strategy of carbon-coated FeP particles anchored on a conducting carbon nanotube network (CNT@FePC) is designed to achieve a superior sodium ion storage. Such a unique structure demonstrated excellent long-life cycling stability (a 95% capacity retention for more than 1200 cycles at 3 A g-1) and rate capability (delivered 272 mAh g-1 at 8 A g-1)

From Discrimination to Generation: Knowledge Graph Completion with Generative Transformer

Knowledge graph completion aims to address the problem of extending a KG with missing triples. In this paper, we provide an approach GenKGC, which converts knowledge graph completion to sequence-to-sequence generation task with the pre-trained language model. We further introduce relation-guided demonstration and entity-aware hierarchical decoding for better representation learning and fast inference. Experimental results on three datasets show that our approach can obtain better or comparable performance than baselines and achieve faster inference speed compared with previous methods with pre-trained language models. We also release a new large-scale Chinese knowledge graph dataset AliopenKG500 for research purpose. Code and datasets are available in https://github.com/zjunlp/PromptKG/tree/main/GenKGC.Comment: Accepted by WWW 2022 Poste

The interface states in gate-all-around transistors (GAAFETs)

The atomic-level structural detail and the quantum effects are becoming crucial to device performance as the emerging advanced transistors, representatively GAAFETs, are scaling down towards sub-3nm nodes. However, a multiscale simulation framework based on atomistic models and ab initio quantum simulation is still absent. Here, we propose such a simulation framework by fulfilling three challenging tasks, i.e., building atomistic all-around interfaces between semiconductor and amorphous gate-oxide, conducting large-scale first-principles calculations on the interface models containing up to 2796 atoms, and finally bridging the state-of-the-art atomic level calculation to commercial TCAD. With this framework, two unnoticed origins of interface states are demonstrated, and their tunability by changing channel size, orientation and geometry is confirmed. The quantitative study of interface states and their effects on device performance explains why the nanosheet channel is preferred in industry. We believe such a bottom-up framework is necessary and promising for the accurate simulation of emerging advanced transistors