First-principles prediction of universal relation between exchange current density and adsorption energy of rare-earth elements in a molten salt

Kwon, Choah,Kang, Joonhee,Noh, Seung Hyo,Han, Byungchan Elsevier 2019 Journal of industrial and engineering chemistry Vol.70 No.-

<P><B>Abstract</B></P> <P>Using first-principles calculations we developed, for the first time, atomistic-level kinetics model to identify a key descriptor controlling electrochemical behaviors of various rare-earth ions solvated in molten salt electrolyte depositing on a solid electrode. We identified that the thermodynamic adsorption energies of rare-earth elements in the metallic electrode have a universal relation with exchange current densities. Our studies can be very useful guide to separate high-level radioactive nuclear materials and industrially valuable rare-earth materials, which can substantially relieve the environmental protection issues in nuclear waste disposal.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Micro-kinetic model to predict and unveil relation of exchange current densities of rare-earth elements in a molten salt. </LI> <LI> Unveiled key descriptor for electrochemical behavior by first-principles calculations. </LI> <LI> Designing principles for enhancing efficiency and environmental safety in separation process for radioactive species. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Based on the micro-kinetic model, relation between adsorption energy on W(110) electrode and exchange current density is shown in graphical abstract, which exchange current density is maximum at optimum adsorption energy and decreases when the adsorption energy is far from optimum adsorption energy.</P> <P>[DISPLAY OMISSION]</P>

Toward Numerically Accurate First-Principles Calculations of Nano-Device Charge Transport Characteristics: The Case of Alkane Single-Molecule Junctions

김용훈 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4

After briefly describing a first-principles computational package we have developed, we report its application to the coherent charge transport properties of single N-alkane molecules (N = 6, 8, 10 and 12) thiolate-bridged to flat Au(111) electrodes. The conductance scaling data are compared with those from recent experiments and other calculations. We describe several measures that resolve the so-called band lineup problem and explicitly demonstrate the errors arising from including an insufficient number of electrode metal atoms within the scattering region. After briefly describing a first-principles computational package we have developed, we report its application to the coherent charge transport properties of single N-alkane molecules (N = 6, 8, 10 and 12) thiolate-bridged to flat Au(111) electrodes. The conductance scaling data are compared with those from recent experiments and other calculations. We describe several measures that resolve the so-called band lineup problem and explicitly demonstrate the errors arising from including an insufficient number of electrode metal atoms within the scattering region.

First-principles prediction of universal relation between exchange current density and adsorption energy of rare-earth elements in a molten salt

권초아,강준희,노승효,한병찬 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.70 No.-

Usingfirst-principles calculations we developed, for thefirst time, atomistic-level kinetics model toidentify a key descriptor controlling electrochemical behaviors of various rare-earth ions solvated inmolten salt electrolyte depositing on a solid electrode. We identified that the thermodynamic adsorptionenergies of rare-earth elements in the metallic electrode have a universal relation with exchange currentdensities. Our studies can be very useful guide to separate high-level radioactive nuclear materials andindustrially valuable rare-earth materials, which can substantially relieve the environmental protectionissues in nuclear waste disposal.

First-Principles Study on the Thermal Stability of LiNiO₂ Materials Coated by Amorphous Al₂O₃ with Atomic Layer Thickness

Kang, Joonhee,Han, Byungchan American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.21

<P>Using first-principles calculations, we study how to enhance thermal stability of high Ni compositional cathodes in Li-ion battery application. Using the archetype material LiNiO<SUB>2</SUB> (LNO), we identify that ultrathin coating of Al<SUB>2</SUB>O<SUB>3</SUB> (0001) on LNO(012) surface, which is the Li de-/intercalation channel, substantially improves the instability problem. Density functional theory calculations indicate that the Al<SUB>2</SUB>O<SUB>3</SUB> deposits show phase transition from the corundum-type crystalline (c-Al<SUB>2</SUB>O<SUB>3</SUB>) to amorphous (a-Al<SUB>2</SUB>O<SUB>3</SUB>) structures as the number of coating layers reaches three. Ab initio molecular dynamic simulations on the LNO(012) surface coated by a-Al<SUB>2</SUB>O<SUB>3</SUB> (about 0.88 nm) with three atomic layers oxygen gas evolution is strongly suppressed at <I>T</I> = 400 K. We find that the underlying mechanism is the strong contacting force at the interface between LNO(012) and Al<SUB>2</SUB>O<SUB>3</SUB> deposits, which, in turn, originated from highly ionic chemical bonding of Al and O at the interface. Furthermore, we identify that thermodynamic stability of the a-Al<SUB>2</SUB>O<SUB>3</SUB> is even more enhanced with Li in the layer, implying that the protection for the LNO(012) surface by the coating layer is meaningful over the charging process. Our approach contributes to the design of innovative cathode materials with not only high-energy capacity but also long-term thermal and electrochemical stability applicable for a variety of electrochemical energy devices including Li-ion batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-21/acsami.5b02572/production/images/medium/am-2015-025723_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b02572'>ACS Electronic Supporting Info</A></P>

First-principles study of charge-ordered insulating phases in Ruddlesden-Popper LaSr2V2O7

Park Se Young 한국물리학회 2022 Current Applied Physics Vol.44 No.-

We investigate the electronic properties of Ruddlesden-Popper LaSr2V2O7 using first-principles density functional theory. By substituting La to Sr in the experimentally reported Ruddlesden-Popper Sr3V2O7 we find the charge-ordered insulating phases. The charge ordering is induced from the average nominal valence of V3.5+ by La-substitution, which in turn disproportionates to a 1:1 ratio of V4+ and V3+ sites. The charge ordering is accompanied by the uniaxial Jahn-Teller distortion compatible with the charge ordering pattern where compression (elongation) along the [110]-direction lowers dxz (dxy/dyz) orbitals with respect to the other t2g orbitals. The comparison of total energies with different charge and magnetic ordering patterns shows that the ground state is insulating with a checkerboard-type of charge ordering and an A-type (layered) antiferromagnetic ordering. Our work, proposing a new charge-ordered insulating phase by A-site substitution, provides an effective way to design insulating oxides with charge ordering.

Elastic and electronic properties of partially ordered and disordered Zr(C₁₋ <i> _x </i>N<i> _x </i>) solid solution compounds: A first principles calculation study

Kim, Jiwoong,Kwon, Hanjung,Kim, Jae-Hee,Roh, Ki-Min,Shin, Doyun,Jang, Hee Dong Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.619 No.-

<P><B>Abstract</B></P> <P>The elastic properties and electronic structures of partially ordered and disordered Zr(C<SUB>1−</SUB> <I> <SUB>x</SUB> </I>N<I> <SUB>x</SUB> </I>) solid solution compounds were investigated using first principles calculations to understand the effects of nitrogen content and atomic distribution. To obtain a proper exchange–correlation energy, we used local density and generalized gradient approximations with Perdew–Burke–Ernzerhof (LDA and GGA-PBE) parametrization. Partially ordered and disordered structures of Zr(C<SUB>1−</SUB> <I> <SUB>x</SUB> </I>N<I> <SUB>x</SUB> </I>) compounds were expressed using unit cell and special quasi-random structure (SQS) models, respectively. We demonstrated that although the disordered models have P1 symmetry with different model sizes and cell shapes compared with ordered models, they reproduce the equilibrium structure and elastic properties of the Zr(C<SUB>1−</SUB> <I> <SUB>x</SUB> </I>N<I> <SUB>x</SUB> </I>) compounds with B1 (Fm-3m) symmetry. However, clear differences exist in the electronic structures. Therefore, the atomic configuration is essential for calculating the electronic structures of the Zr(C<SUB>1−</SUB> <I> <SUB>x</SUB> </I>N<I> <SUB>x</SUB> </I>) compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Elastic and electronic properties of Zr(C<SUB>1−<I>x</I> </SUB>N<SUB> <I>x</I> </SUB>) compounds by first principles. </LI> <LI> We elucidate the effects of atomic configuration on compound properties. </LI> <LI> Ordered and disordered models are depicted by unit cell and special quasi-random structures. </LI> <LI> Disordered structures are suitable models to estimate compound elastic properties. </LI> <LI> The atomic configuration is essential to obtain accurate electronic structures. </LI> </UL> </P>

알루미늄 도핑된 스피넬 구조에서의 얀-텔러 효과의 이해

김두호(Duho Kim),임진명(Jin-Myoung Lim),황태순(Taesoon Hwang),조경재(Kyeongjae Cho),조맹효(Maenghyo Cho) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Through first-principles calculations and experimental observations, we present the fundamental understanding of mechanism of the suppression of Jahn-Teller effects using Al doping in the cubic spinel oxide (LiMn2O4). The Al-doped spinel exhibits better cycle stability as compared with the pristine spinel. Considering partial density of states (PDOS) and band fillings of the two oxides from the first-principles calculations, the pristine spinel is entirely suffered from Jahn-Teller distortion by Mn3+, indicating the anisotropic electronic structure. On the other hand, the Al-doped spinel shows suppressed Jahn-Teller effects, presenting the isotropic electronic structure. These findings based on the mechanistic understanding of Jahn-Teller effects are expected to be a basic solution and design new cathodes for the electrochemically enhanced properties in Li-ion batteries.

First-principle study on catalytic activity of functionalized Ti3C2 MXene as cathode catalyst for Li–O2 batteries

Yang Yingying,Chen Jian,Gao Qiqian,Feng Yu,Xing Fei,Yao Man 한국물리학회 2022 Current Applied Physics Vol.34 No.-

Two-dimensional layered Ti3C2, one representative MXene, is notable as promising cathode catalyst for rechargeable lithium-oxygen (Li–O2) batteries. Using first-principles calculations, we construct cathode electrochemical interface catalytic model to simulate the structural evolution during discharging and charging processes, and the calculated ORR, OER and TOT overpotentials are used to quantitatively assess the catalytic activity of Ti3C2 MXene with and without O, F and OH functional groups. Interestingly, we find that the catalytic activity follows such a trend: Ti3C2O2>Ti3C2F2>Ti3C2(OH)2>Ti3C2, which suggests that O-terminated Ti3C2 MXene has great advantages and potentiality for catalyzing ORR and OER in Li–O2 batteries. This is caused by Ti3C2O2 surface shows stronger oxidation capability toward O22 compared to Ti3C2F2, Ti3C2(OH)2 and Ti3C2. The present study may provide a guideline to accelerate ORR and OER reactions of Ti3C2 MXene as cathode catalyst in Li–O2 batteries, with O-terminated group being taken into consideration.

First-principles study of the field-induced current-switch by dithiocarboxylate anchoring group in molecular junction

Caijuan Xia,Changfeng Fang,Peng Zhao,Desheng Liu 한국물리학회 2010 Current Applied Physics Vol.10 No.3

Based on non-equilibrium Green’s function and first-principles calculations, we investigate the electronic transport properties of 4,40-biphenyl bis (dithiocarboxylate) (BDCT) molecular junction with the fieldinduced geometry relaxation. The results indicate that the external field has noticeable effects on the molecular structure, coupling strengths and bonding distances. More importantly, it is found that the inclusion of field-induced molecular geometry relaxation can predict a current-switch behavior, which may have some potential applications in future molecular circuit.

First-principles study on the reaction mechanisms of the electrode materials for Li-ion batteries

서동화 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

With the growing interest in power sources for large applications such as electric vehicle (EV), lithium-ion batteries are finding new opportunities in this emerging area. Intensive research efforts are focused on developing suitable electrode material, the key component of lithiumion battery, for these applications. The electrode materials for lithiumion batteries for use in EV require high stability, high power, high energy, and low cost. In this talk, I will present the first-principles results on the oxygen redox activity in Li-excess cathode materials[1] and the reaction mechanism of lithium titanate anode materials[2]. Fundamental understanding of the electrode's reaction mechanism based on first-principles calculations can accelerate to develop high-performing electrode materials.