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Kim, Jaewon,Lee, Kyung Eun,Kim, Kyung Hwan,Wi, Sungun,Lee, Sangheon,Nam, Seunghoon,Kim, Chunjoong,Kim, Sang Ouk,Park, Byungwoo Elsevier 2017 Carbon Vol.114 No.-
<P>Graphene has been intensively adopted into boosting the electrochemical performances of battery electrode materials due to its superior nature. In the case of Li4Ti5O12 (LTO), the application of graphene has been specifically focused on ameliorating the low electronic conductivity of LTO. So far, these attempts aiming to increase the composite's electronic conductivity involved thick graphene layers, which inevitably hindered Li-ion diffusion and eventually harmed the electrochemical kinetics in LTO's surface. In this work, high quality minimum-impurity graphene oxide was prepared by means of thorough cleaning and dialysis, which enabled each single-layered graphene to successfully wrap individual LTO particles. The resulting single-layer graphene-wrapped LTO exhibits an excellent specific capacity of 130 mAh g(-1) even at a lithiation/delithiation of 30 degrees C. Such a high rate capability is one of the highest values among the reported LTO with comparable sizes (similar to 200 nm). To uncover the reasons for such high performance, electrochemical properties from varied graphene contents were juxtaposed for comparison, and as a result, number of graphene layers and the corresponding kinetic parameters were found correlated. With adequate validity, single graphene layer was revealed to be the uttermost optimum for both Li+ diffusion and electronic conduction. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Kim, Soo,Kim, Chunjoong,Jhon, Young-In,Noh, Jae-Kyo,Vemuri, Sesha Hari,Smith, Robert,Chung, Kyung Yoon,Jhon, Myung S.,Cho, Byung-Won The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.48
<P>Li<SUB>2</SUB>MnO<SUB>3</SUB>-stabilized LiCoO<SUB>2</SUB> electrode materials were synthesized using the method of mechanochemical process. Li<SUB>2</SUB>MnO<SUB>3</SUB> was prepared and the mechanochemical process was carried out with LiCoO<SUB>2</SUB>, which yielded the layered–layered integrated structure nanocomposites. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy studies confirmed the structural integration of 0.5Li<SUB>2</SUB>MnO<SUB>3</SUB>·0.5LiCoO<SUB>2</SUB> electrode materials. We also performed the high temperature heat treatment, where our 0.5Li<SUB>2</SUB>MnO<SUB>3</SUB>·0.5LiCoO<SUB>2</SUB> electrode materials showed improvement in the discharge capacity (∼180 mA h g<SUP>−1</SUP>) with good cycleability. To obtain a physical insight into the performance of the nanocomposite structure, we carried out first principles calculations to obtain activation energy barriers of Li<SUP>+</SUP> de-/intercalation, which suggested that utilizing both Li<SUB>2</SUB>MnO<SUB>3</SUB> and LiCoO<SUB>2</SUB> components can enhance the Li<SUP>+</SUP> diffusion for the layered–layered integrated structure.</P> <P>Graphic Abstract</P><P>Li<SUB>2</SUB>MnO<SUB>3</SUB>-stabilized LiCoO<SUB>2</SUB> electrode materials were synthesized using the method of mechanochemical process. First principles calculations were carried out to further obtain the physical insight of the layered-layered system. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm35654f'> </P>
Kim, Chunjoong,Phillips, Patrick J.,Xu, Linping,Dong, Angang,Buonsanti, Raffaella,Klie, Robert F.,Cabana, Jordi American Chemical Society 2015 Chemistry of materials Vol.27 No.1
<P>Chemical degradation at electrode/electrolyte interfaces in high-energy storage devices, such as Li-ion batteries, imposes durability challenges that affect their life and cost. In oxide electrodes, degradation is linked to the presence of redox active transition metals at the surface. Here, we demonstrate a strategy toward the stabilization of interfaces using core–epitaxial shell nanocrystals. The core of the nanocrystal is composed of an electroactive oxide, which is passivated by an ultrathin epitaxial oxide shell enriched in a redox inactive ion. This approach imparts interfacial stability while preserving the high storage capability and fast carrier transport of the material, compared to unmodified versions. The validity of the concept is proved with Li<SUB>1+<I>x</I></SUB>Mn<SUB>2–<I>x</I></SUB>O<SUB>4</SUB> nanocrystals with a 1–2 nm Al-rich shell, which showed reduced sensitivity to harsh environments, compared to bare counterparts. The approach is generalizable to any transition-metal-based battery system where electrode–electrolyte interactions must be controlled.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-1/cm503615w/production/images/medium/cm-2014-03615w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm503615w'>ACS Electronic Supporting Info</A></P>
Critical Size of a Nano SnO<sub>2</sub> Electrode for Li-Secondary Battery.
Kim, Chunjoong,Noh, Mijung,Choi, Myungsuk,Cho, Jaephil,Park, Byungwoo WILEY-VCH Verlag 2005 Chem Inform Vol.36 No.38
<P>For Abstract see ChemInform Abstract in Full Text.</P>
Kim, Chunjoong,Adil, Abdullah A.,Bayliss, Ryan D.,Kinnibrugh, Tiffany L.,Lapidus, Saul H.,Nolis, Gene M.,Freeland, John W.,Phillips, Patrick J.,Yi, Tanghong,Yoo, Hyun Deog,Kwon, Bob Jin,Yu, Young-Sang American Chemical Society 2018 Chemistry of materials Vol.30 No.5
<P>Oxides undergoing reversible electrochemical cycling of Mg<SUP>2+</SUP> ions would enable novel battery concepts beyond Li<SUP>+</SUP>, capable of storing large amounts of energy. However, materials showing this chemical reactivity are scarce. Suitable candidates require small particles to shorten transport lengths, together with chemically complex structures that promote cation mobility, such as spinel. These goals pose a challenge for materials chemists. Here, nanocrystals of spinel-type Mg<SUB>0.5</SUB>Mn<SUB>2.5</SUB>O<SUB>4</SUB> were prepared using colloidal synthesis, and their electrochemical activity is presented. Cycling in an aqueous Mg<SUP>2+</SUP> electrolyte led to a reversible transformation between a reduced spinel and an oxidized layered framework. This reaction involves large amounts of capacity because of the full oxidation to Mn<SUP>4+</SUP>, through the extraction of both Mg<SUP>2+</SUP> and, in the first cycle, Mn<SUP>2+</SUP> ions. Re-formation of the spinel upon reduction resulted in enrichment with Mg<SUP>2+</SUP>, indicating that its insertion is more favorable than that of Mn<SUP>2+</SUP>. Incorporation of water into the structure was not indispensable for the transformation, as revealed by experiments in non-aqueous electrolytes and infrared spectroscopy. The findings open the door for the use of similar nanocrystals in Mg batteries provided that electrolytes with suitable anodic stability are discovered, thereby identifying novel routes toward electrode materials for batteries with high energy.</P> [FIG OMISSION]</BR>
고엔트로피세라믹을 이용한 암염 구조 양극 소재 연구 동향
김민정(Minjeong Kim),구자훈(Jahun Koo),강민정(Minjeong Kang),송주아(Juah Song),김천중(Chunjoong Kim) 한국세라믹학회 2022 세라미스트 Vol.25 No.1
Development of lithium-ion rechargeable batteries with high energy storage capability are required in timely manner. Recently, it has been experimentally and computationally proven that oxides with the disordered rock salt structure can be charged and discharged in the Li-ion battery system. In particular, the high entropy disordered rock salt cathode has unique structure property, where both Li-ion and transition metal are randomly located on the cation sites. Such disordering in metal sites can migrate the Li-ion in a percolating way albeit with sluggish kinetics. Therefore, the high entropy disordered rock salt structure has attracted great attention due to its high energy density and stable structure. In this paper, we introduce a simple and effective strategy in the selection of transition metals for high entropy cathodes to achieve desired electrochemical properties.
Hwang, Taehyun,Cho, Duckhyung,Kim, Jinhyun,Kim, Jaewon,Lee, Sangheon,Lee, Byungho,Kim, Kyung Hwan,Hong, Seunghun,Kim, Chunjoong,Park, Byungwoo Elsevier 2016 Nano energy Vol.25 No.-
<P><B>Abstract</B></P> <P>An organic-inorganic hybrid perovskite is considered as a next generation solar energy harvester due to the high power conversion efficiency. The starting precursor solution for the organolead halide perovskite is of significant interests because the ionic components in the precursor can critically affect the nanostructures and thereby the optoelectronic properties. In this work, the basic and well-known precursor solution for CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) comprised of CH<SUB>3</SUB>NH<SUB>3</SUB>I and PbCl<SUB>2</SUB>, is specifically analyzed to unravel the phenomena in the Cl-mediated solutions. The shift in equilibrium between lead-halide complex and the solvent results into the CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) grain evolution with Cl incorporation, which is confirmed through x-ray fluorescence and diffraction. The effects of Cl on the optoelectronic properties are further verified by conductive atomic force microscopy, and the existing Cl leads to the 30-times-increased and inhomogeneously distributed photocurrent for CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) grains compared with CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>. Moreover, photocurrent noise from the mixed-halide perovskite is reduced than that from the triiodide perovskite phase. Combining the microstructural evolution with the optoelectronic properties of mixed-halide perovskite, it is concluded that additional Cl reduces the defects of recombination centers resulting high photocurrent.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) grain evolution from the equilibrium shift in the precursor. </LI> <LI> Grain-dependent and inhomogeneous conductive-AFM photocurrents in CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl). </LI> <LI> Defects reduction in CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) than CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> by scanning noise microscopy. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Microstructural and optoelectronic roles of chlorine in CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> perovskite are explored. The Cl-mediated CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) grain evolution is investigated from the shift in equlibrium between lead-halide complex and the solvent of the precursor. The evidences for the Cl incorporation in the crystalline phase are further characterized by x-ray fluorescence and diffraction. Optoelectronic properties are compared between CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) and CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>, and 30-times-enhanced photocurrent in the CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>(Cl) grains are observed with inhomogeneous distribution, compared with CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>. The origin of high optoelectronic responses is explained by the Cl-induced reduction of defects and recombination centers, as confirmed by the noise-microscopy comparison.</P> <P>[DISPLAY OMISSION]</P>