Stoichiometric Layered Potassium Transition Metal Oxide for Rechargeable Potassium Batteries

Kim, Haegyeom,Seo, Dong-Hwa,Urban, Alexander,Lee, Jinhyuk,Kwon, Deok-Hwang,Bo, Shou-Hang,Shi, Tan,Papp, Joseph K.,McCloskey, Bryan D.,Ceder, Gerbrand American Chemical Society 2018 Chemistry of materials Vol.30 No.18

<P>K-ion batteries are promising alternative energy storage systems for large-scale applications because of the globally abundant K reserves. K-ion batteries benefit from the lower standard redox potential of K/K<SUP>+</SUP> than that of Na/Na<SUP>+</SUP> and even Li/Li<SUP>+</SUP>, which can translate into a higher working voltage. Stable KC<SUB>8</SUB> can also be formed via K intercalation into a graphite anode, which contrasts with the thermodynamically unfavorable Na intercalation into graphite, making graphite a readily available anode for K-ion battery technology. However, to construct practical rocking-chair K-ion batteries, an appropriate cathode material that can accommodate reversible K release and storage is still needed. We show that stoichiometric KCrO<SUB>2</SUB> with a layered O3-type structure can function as a cathode for K-ion batteries and demonstrate a practical rocking-chair K-ion battery. In situ X-ray diffraction and electrochemical titration demonstrate that K<SUB><I>x</I></SUB>CrO<SUB>2</SUB> is stable for a wide K content, allowing for topotactic K extraction and reinsertion. We further explain why stoichiometric KCrO<SUB>2</SUB> is unique in forming the layered structure unlike other stoichiometric K-transition metal oxide compounds, which form nonlayered structures; this fundamental understanding provides insight for the future design of other layered cathodes for K-ion batteries.</P> [FIG OMISSION]</BR>

1H NMR Measurements of the Phase Transition of (NH₄)₃H(SO₄)₂ Single Crystals

S. H. Choi,Moohee Lee,Ae Ran Lim,K. S. Han,S. K. Kwon,S. K. Nam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

$^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K. $^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K.

1H Nuclear Magnetic Resonance study of Ferroelectric (NH4)3H(SO4)2

S. H. Choi,K. S. Han,S. K. Kwon,S. K. Nam,H. H. Choi,Moohee Lee,Ae Ran Lim 한국자기공명학회 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.2

1H nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal (NH4)3H(SO4)2. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the 1H NMR MAS spectrum at 340 K. As temperature decreases, the 1H NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of T1 for ammonium and hydrogen-bond protons are similar in the whole range of temperature. T1 of 1H NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then T1 shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and T1 clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.

[ $^1H$ ] Nuclear Magnetic Resonance Study of Ferroelectric $(NH_4)_3H(SO_4)_2$

Choi, S.H.,Han, K.S.,Kwon, S.K.,Nam, S.K.,Choi, H.H.,Lee, Moo-Hee,Lim, Ae-Ran Korean Magnetic Resonance Society 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.2

[ $^1H$ ] nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal $(NH_4)_3H(SO_4)_2$. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the $^1H$ NMR MAS spectrum at 340 K. As temperature decreases, the $^1H$ NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of $T_1$ for ammonium and hydrogen-bond protons are similar in the whole range of temperature. $T_1$ of $^1H$ NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then $T_1$ shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and $T_1$ clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.

Jacobi–Stirling numbers, Jacobi polynomials, and the left-definite analysis of the classical Jacobi differential expression

Everitt, W.N.,Kwon, K.H.,Littlejohn, L.L.,Wellman, R.,Yoon, G.J. Koninklijke Vlaamse Ingenieursvereniging 2007 Journal of computational and applied mathematics Vol.208 No.1

<P><B>Abstract</B></P><P>We develop the left-definite analysis associated with the self-adjoint Jacobi operator Ak(α,β), generated from the classical second-order Jacobi differential expression<SUB>ℓα,β,k</SUB>[y](t)=1<SUB>wα,β</SUB>(t)((-(1-t<SUP>)α+1</SUP>(1+t<SUP>)β+1</SUP><SUP>y′</SUP>(t)<SUP>)′</SUP>+k(1-t<SUP>)α</SUP>(1+t<SUP>)β</SUP>y(t))(t∈(-1,1)),in the Hilbert space Lα,β2(-1,1)≔<SUP>L2</SUP>((-1,1);<SUB>wα,β</SUB>(t)), where <SUB>wα,β</SUB>(t)=(1-t<SUP>)α</SUP>(1+t<SUP>)β</SUP>, that has the Jacobi polynomials {Pm(α,β)}m=0∞ as eigenfunctions; here, α,β>-1 and <I>k</I> is a fixed, non-negative constant. More specifically, for each n∈N, we explicitly determine the unique left-definite Hilbert–Sobolev space Wn,k(α,β)(-1,1) and the corresponding unique left-definite self-adjoint operator Bn,k(α,β) in Wn,k(α,β)(-1,1) associated with the pair (Lα,β2(-1,1),Ak(α,β)). The Jacobi polynomials {Pm(α,β)}m=0∞ form a complete orthogonal set in each left-definite space Wn,k(α,β)(-1,1) and are the eigenfunctions of each Bn,k(α,β). Moreover, in this paper, we explicitly determine the domain of each Bn,k(α,β) as well as each integral power of Ak(α,β). The key to determining these spaces and operators is in finding the explicit Lagrangian symmetric form of the integral composite powers of <SUB>ℓα,β,k</SUB>[·]. In turn, the key to determining these powers is a double sequence of numbers which we introduce in this paper as the <I>Jacobi–Stirling numbers</I>. Some properties of these numbers, which in some ways behave like the classical Stirling numbers of the second kind, are established including a remarkable, and yet somewhat mysterious, identity involving these numbers and the eigenvalues of Ak(α,β).</P>

RNPS1 is modulated by ubiquitin-specific protease 4

Kwon, S. K.,Kim, E. H.,Baek, K. H. North-Holland Pub 2017 FEBS letters Vol. No.

<P>RNA-binding protein with serine-rich domain 1 (RNPS1) is a component of pre-splicing and post-splicing multiprotein complexes, which activates constitutive and alternative splicing. RNPS1 participates in the formation of the spliceosome and activates the pre-mRNA splicing process. In the present study, we found that ubiquitin-specific protease 4 (USP4) is a binding partner of RNPS1. Although RNPS1 is polyubiquitinated by both K48- and K63-linkages, USP4 exclusively deubiquitinates K63-linked polyubiquitin chains of RNPS1. We also demonstrate that the catalytic activity of USP4 on ubiquitinated RNPS1 is elevated by squamous cell carcinoma antigen recognized by T cells 3 (Sart3).</P>

Substrate specificity of a recombinant d-lyxose isomerase from Providencia stuartii for monosaccharides

Kwon, H.J.,Yeom, S.J.,Park, C.S.,Oh, D.K. Society for Bioscience and Bioengineering, Japan ; 2010 Journal of bioscience and bioengineering Vol.110 No.1

The specific activity and catalytic efficiency (k<SUB>cat</SUB>/K<SUB>m</SUB>) of the recombinant putative protein from Providencia stuartii was the highest for d-lyxose among the aldose substrates, indicating that it is a d-lyxose isomerase. Gel filtration analysis suggested that the native enzyme is a dimer with a molecular mass of 44 kDa. The maximal activity for d-lyxose isomerization was observed at pH 7.5 and 45 <SUP>o</SUP>C in the presence of 1 mM Mn<SUP>2+</SUP>. The enzyme exhibited high isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration, such as d-lyxose, d-mannose, l-ribose, d-talose, and l-allose (listed in decreasing order of activity). The enzyme exhibited the highest activity for d-xylulose among all pentoses and hexoses. Thus, d-lyxose was produced at 288 g/l from 500 g/l d-xylulose by d-lyxose isomerase at pH 7.5 and 45 <SUP>o</SUP>C for 2 h, with a conversion yield of 58 % and a volumetric productivity of 144 g l<SUP>-1</SUP> h<SUP>-1</SUP>. The observed k<SUB>cat</SUB>/K<SUB>m</SUB> (920 mM<SUP>-1</SUP> s<SUP>-1</SUP>) of P. stuartiid-lyxose isomerase for d-xylulose is higher than any of the k<SUB>cat</SUB>/K<SUB>m</SUB> values previously reported for sugar and sugar phosphate isomerases with monosaccharide substrates. These results suggest that the enzyme will be useful as an industrial producer of d-lyxose.

SA350 LF3 강 수송용기의 동적파괴인성평가

김국철(K.C. Kim),석진익(J.I. Suk),권희경(H.K. Kwon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.11

A spent nuclear fuel cask should safe in the case of most severe accident loading during transportation. Therefore, in order to verify the integrity of the shipping cask manufactured by doosan heavy industries for the first time in Korea, rapid loading K1C tests has performed as material property evaluation. In this paper, the dynamic fracture toughness obtained by rapid loading K<SUB>IC</SUB> tests is discussed. The procedure of the integrity evaluation of the shipping cask is as follow: First, the maximum flaw size for the full area of forging product of the shipping cask is measured by nondestructive examination. Second, the dynamic fracture toughness test is carried out at -40℃. Third, FEM is performed for the model of the shipping cask with the maximum size flaw measured by NDE under seismic loading. Finally, the integrity of the shipping cask is evaluated by comparing maximum stress intensity factor calculated by FEM with dynamic fracture toughness measured by the experiment. In the integrity evaluation, our company has carried out nondestructive examination and dynamic fracture toughness test, and GNB Company in Germany has carried out FEM analysis. From the evaluation, the integrity of shipping cask was confirmed.

Novel method for investigation of a K-Mg-based CO₂ sorbent for sorption-enhanced water-gas shift reaction

Byun, C.K.,Kwon, S.J.,Im, H.B.,Ahn, H.S.,Ryu, H.J.,Yi, K.B. Pergamon Press 2016 RENEWABLE ENERGY Vol.87 No.1

CO<SUB>2</SUB> sorption reactions at 20 bar and two different temperatures (i.e., 180 and 220 <SUP>o</SUP>C) using a K-Mg-based CO<SUB>2</SUB> sorbent were carried out in a custom-designed high-pressure thermogravimetric analyzer (pressurized bubbling fluidized bed reactor on a scale) coupled with a gas chromatograph. The experimental apparatus, including the thermogravimetric analyzer, was custom-designed to measure weight changes caused by either CO<SUB>2</SUB> sorption or water sorption or both. Analysis of the CO<SUB>2</SUB> sorption reaction revealed that water sorption takes place rapidly with a moderate CO<SUB>2</SUB> sorption rate at the early stage of the reaction. Then, the reaction migrates to CO<SUB>2</SUB> sorption with simultaneous water desorption. Therefore, the mechanism of the CO<SUB>2</SUB> sorption reaction is assumed to consist of fast hydration of K<SUB>2</SUB>CO<SUB>3</SUB> and MgO, formation and decomposition of KHCO<SUB>3</SUB>, and finally carbonation of Mg(OH)<SUB>2</SUB> resulting in MgCO<SUB>3</SUB> as the main product. K<SUB>2</SUB>CO<SUB>3</SUB> is assumed to provide an efficient pathway for CO<SUB>2</SUB> and water to travel into the core region of the sorbent via a reversible reaction between K<SUB>2</SUB>CO<SUB>3</SUB> and KHCO<SUB>3</SUB>.

Holographic entanglement entropy of anisotropic minimal surfaces in LLM geometries

Kim, C.,Kim, K.K.,Kwon, O-K. North-Holland Pub. Co 2016 Physics letters. Section B Vol.759 No.-

<P>We calculate the holographic entanglement entropy (HEE) of the Z(k) orbifold of Lin-Lunin-Maldacena (LLM) geometries which are dual to the vacua of the mass-deformed ABJM theory with Chern-Simons level k. By solving the partial differential equations analytically, we obtain the HEEs for all LLM solutions with arbitrary M2 charge and k up to mu(2)(0)-order where mu(0) is the mass parameter. The renormalized entanglement entropies are all monotonically decreasing near the UV fixed point in accordance with the F-theorem. Except the multiplication factor and to all orders in mu(0), they are independent of the overall scaling of Young diagrams which characterize LLM geometries. Therefore we can classify the HEEs of LLM geometries with Z(k) orbifold in terms of the shape of Young diagrams modulo overall size. HEE of each family is a pure number independent of the 't Hooft coupling constant except the overall multiplication factor. We extend our analysis to obtain HEE analytically to mu(4)(0)-order for the symmetric droplet case. (C) 2016 The Author(s). Published by Elsevier B.V.</P>