Diffusion kinetics governing the diffusivity and diffusion anisotropy of alloying anodes in Na-ion batteries

Park, Jun-Hyoung,Choi, Yong-Seok,Byeon, Young-Woon,Ahn, Jae-Pyoung,Lee, Jae-Chul unknown 2019 Nano energy Vol.65 No.-

<P><B>Abstract</B></P> <P>Diffusion in alloying anode materials was previously viewed as solute diffusion in conventional alloys. However, solute diffusion, neglecting the presence of a thin intermediate reaction layer between the unreacted anode material and inflowing carrier ions, is insufficient to account for the diffusion kinetics in alloying anodes and their influence on the electrochemical properties of batteries. Here, by performing a comparative study on Na-Sb and Na-Sn battery systems displaying differing diffusion kinetics, we establish the relationship between diffusion kinetics and electrochemical properties for batteries. <I>In situ</I> microelectrochemical experiments show that sodiation in Na-Sb and Na-Sn systems is governed by an interface-controlled reaction (ICR) and a diffusion-controlled reaction (DCR), respectively, causing them to display significantly different diffusion rates, diffusion anisotropy, and possibly self-limiting diffusion of carrier ions. Density functional theory calculations are performed to elucidate the structural origin of the observed diffusion behaviors. It is found that the different degrees of structural stability evaluated for the propagating interfaces of the two systems are responsible for the differing diffusion kinetics, which in turn determine the respective diffusion rates and diffusion anisotropy of the anode materials. The present study provides crude yet quantitative guidelines for selecting battery materials and can be used to develop fast-charging batteries with high stability and improved cycle life.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Relationship between diffusion kinetics and electrochemical properties of alloying anodes is established. </LI> <LI> Diffusion behaviors and associated diffusion kinetics of Sb and Sn anodes are explored using <I>in situ</I> sodiation experiments. </LI> <LI> First-principles calculations are conducted to elucidate the structural origins of the observed diffusion behaviors. </LI> <LI> Systems obeying diffusion-controlled reaction generally display faster diffusion rates and isotropic diffusion. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

First principles calculation of boron diffusion in fcc-Fe

Xin Zhang,Xianglong Li,Ping Wu,Sen Chen,Shiping Zhang,Ning Chen,Xiulan Huai 한국물리학회 2018 Current Applied Physics Vol.18 No.10

The diffusion mechanism of boron in fcc-Fe was studied by first-principles calculations. The sites where B atoms tend to occupy and the diffusion behavior were calculated. Results indicated that the main mechanism of boron diffusion in fcc-Fe was the B–monovacancy complex mechanism instead of the interstitial mechanism. The diffusion coefficient D1 of the B–monovacancy complex mechanism was calculated without considering the backward jump of the B atoms. The calculated D1=1.26×10−4×exp(–2.01eV/kBT) m2·s−1 is consistent with the reported results from experiments.

Theoretical studies on the stabilization and diffusion behaviors of helium impurities in 6H-SiC by DFT calculations

Obaidullah Obaid,Zhao RuiXuan,Li XiangCao,Wan ChuBin,Sui TingTing,Ju Xin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

In fusion environments, large scales of helium (He) atoms are produced by a radical transformation along with structural damage in structural materials, resulting in material swelling and degradation of physical properties. To understand its irradiation effects, this paper investigates the stability, electronic structure, energetics, charge density distribution, PDOS and TDOS, and diffusion processes of He impurities in 6HSiC materials. The formation energy indicates that a stable, favorable position for interstitial He is the HR site with the lowest energy of 2.40 eV. In terms of vacancy, the He atom initially prefers to substitute at pre-existing Si vacancy than C vacancy due to lower substitution energy. The minimum energy paths (MEPs) with migration energy barriers are also calculated for He impurity by interstitial and vacancymediated diffusion. Based on its calculated energy barriers, the most possible diffusion path includes the exchange of interstitial and vacancy sites with effective migration energies ranging from 0.101 eV to 1.0 eV. Our calculation provides a better understanding of the stabilization and diffusion behaviors of He impurities in 6H-SiC materials

Leakage Flow Influence on SHF pump model performances

Dupont, Patrick,Bayeul-Laine, Annie-Claude,Dazin, Antoine,Bois, Gerard,Roussette, Olivier,Si, Qiaorui Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.3

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 9.06 code (RANS frozen and unsteady calculations). Some results were already presented at the XXth IAHR Symposium for three flowrates for RANS frozen and URANS calculations. In the present paper, comparisons between URANS calculations with and without leakages and experimental results are presented and discussed for these flow rates. The performances of the diffuser obtained by numerical calculations are compared to those obtained by the three-holes probe measurements. The comparisons show the influence of fluid leakages on global performances and a real improvement concerning the efficiency of the diffuser, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up.

Leakage Flow Influence on SHF pump model performances

Dupont, Patrick,Bayeul-Laine, Annie-Claude,Dazin, Antoine,Bois, Gerard,Roussette, Olivier,Si, Qiaorui Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.4

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 9.06 code (RANS frozen and unsteady calculations). Some results were already presented at the XXth IAHR Symposium for three flowrates for RANS frozen and URANS calculations. In the present paper, comparisons between URANS calculations with and without leakages and experimental results are presented and discussed for these flow rates. The performances of the diffuser obtained by numerical calculations are compared to those obtained by the three-holes probe measurements. The comparisons show the influence of fluid leakages on global performances and a real improvement concerning the efficiency of the diffuser, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up.

Surface Dynamics of Cu and Ag Atoms on Hydroxylated MgO(001) Surfaces

전준진,유병덕 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.1

Density-functional theory calculations were performed to investigate the surface dynamics of Cu and Ag (X_M) atoms on MgO(001) surfaces with surface-functional hydroxyl groups. The adsorption, diffusion, bonding, and electronic structure of X_M on these surfaces are presented. The results indicate a large energy gain in the adsorption of X_M on MgO_hdr(001) with respect to X_M on MgO(001). This suggests that the adsorption of X_M is stronger on MgO_hdr(001). Further analysis shows that in the presence of surface hydroxyl groups, X_M atoms preferentially form X_MOH complexes instead of X_M dimers. The surface diffusion barriers of X_MOH on MgO(001) [X_M on MgO_hdr(001)] are calculated. CuOH is found to have a higher surface diffusion energy barrier than AgOH, but a slightly lower energy barrier to diffusion than AuOH. Therefore, sintering of Ag on MgO_hdr(001) surfaces is expected to be different from that of Cu or Au. Finally, the electronic structures and charge rearrangements of X_M on MgO_hdr(001) are presented and compared with those of Au on MgO_hdr(001).

Leakage Flow Influence on SHF pump model performances

Annie-Claude Bayeul-Lainé,Patrick Dupont,Antoine Dazin,Gérard Bois,Olivier Roussette,Qiaorui Si 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 9.06 code (RANS frozen and unsteady calculations). Some results were already presented at the XXth IAHR Symposium for three flowrates for RANS frozen and URANS calculations. In the present paper, comparisons between URANS calculations with and without leakages and experimental results are presented and discussed for these flow rates. The performances of the diffuser obtained by numerical calculations are compared to those obtained by the three-holes probe measurements. The comparisons show the influence of fluid leakages on global performances and a real improvement concerning the efficiency of the diffuser, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up.

Leakage Flow Influence on SHF pump model performances

Patrick Dupont,Annie-Claude Bayeul-Lainé,Antoine Dazin,Gérard Bois,Olivier Roussette,Qiaorui Si 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.3

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 9.06 code (RANS frozen and unsteady calculations). Some results were already presented at the XXth IAHR Symposium for three flowrates for RANS frozen and URANS calculations. In the present paper, comparisons between URANS calculations with and without leakages and experimental results are presented and discussed for these flow rates. The performances of the diffuser obtained by numerical calculations are compared to those obtained by the three-holes probe measurements. The comparisons show the influence of fluid leakages on global performances and a real improvement concerning the efficiency of the diffuser, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up.

Adsorption of Transition-Metal Atoms on MgO(001) Surfaces: Atomic Structures, Diffusion and Electronic Structures

박진우,유병덕 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

The adsorption structures and diffusion of transition-metal (TM) adatoms on defect-free MgO(001) surfaces were investigated in this study by using ab initio electronic structure calculations based on the density functional theory. The preferential adsorption of TM on top of a surface oxygen atom was found, which coincides with the results of previous works. The surface diffusion occurred along the channel that passed through a hollow site and the energy barriers ranged from 0.12 to 0.83 eV. We also found that whereas Ni adatoms effectively switched on the spin polarization to reduce the diffusion barrier on the surface, all the other TM adatoms kept their spin state during the surface diffusion. Also examined were the electronic properties of the TM adatoms on MgO(001). We found that the energy levels of the TM adatoms in the gap region of MgO(001) depended on the adsorption sites and that the shapes of the electronic structures significantly varied with the adsorption sites.

Investigation of the interstitial oxygen behaviors in vanadium alloy: A first-principles study

Xingming Zhang,Yifan Li,Qiaoling He,Ruilian Li,Lei Deng,Liang Wang,Xunlin Liu,Jianfeng Tang,Huiqiu Deng,Wang-Yu Hu 한국물리학회 2018 Current Applied Physics Vol.18 No.2

This study aims at characterizing the interstitial Oxygen (O) behaviors in the Vanadium (V) Alloy by means of the first-principles calculations. For this, the interations between vacancy (Vac) and O interstitil atom are studied in detail to obtain the binding energies and stable structures of the complexes. It can be seen that monovacancy binding with two O atoms occupied the opposing octahedral stie are particularly stable, and is liable to form VacO2 cluster in the V alloys. According to the mass action analysis, the predicted temperature dependence of the concentration for VacOn complexes are presented. Apart from monovacancy, we also consider the trapping behavior of vacancy cluster on the O atoms. The results also prove that one vacancy can trap two O atoms in the V alloys. Based the diffusion theory, we obtain the diffusion coefficients as a function of temperature with or without the vacancy effect in the V alloys. The predicted O diffusion coefficients in defect-free V alloys from our first-principles calculations are in excellent ageement with the experimental data, meanings that the vacancy-limited mechanism does not play the key role for O diffusion in V alloys. Regarding the interactions between vacancy, solutes and O atom, combining with the diffusion barriers of O affected by vacancy and solute, we infer the formation mechanism of the precipitates in the V alloys.