Electrochemically driven chemical transformations play the key role in controlling storage of energy in chemical bonds and subsequent conversion to power electric vehicles and consumer electronics. The promise of coupling anionic oxygen redox with cationic redox to achieve a substantial increase in capacities has inspired research in a wide range of electrode materials. A key challenge is that these studies have focused on polycrystalline materials, where it is hard to perform precise structural determinations, especially related to the location of light atoms. Here a different approach is utilized and a highly ordered single crystal, Na 2− x IrO 3 is harnessed, to explore the role of defects and structural transformations in layered transition metal oxide materials on redox‐activity, capacity, reversibility, and stability. Within a combined experimental and theoretical framework, it is demonstrated that 1) it is possible to cycle Na 2− x IrO 3 , offering proof of principle for single‐crystal based batteries 2) structural phase transitions coincide with Ir 4+ /Ir 5+ redox couple with no evident contribution from anionic redox 3) strong irreversibility and capacity fade observed during cycling correlates with the Na + migration resulting in progressive growth of an electrochemically inert O3‐type NaIrO 3 phase.

In this report, the feasibility of reversible Ca2+ or Zn2+ intercalation into a crystalline cubic spinel Mn2O4 cathode has been investigated using electrochemical methods in an aqueous electrolyte. A combination of synchrotron XRD and XANES studies identified the partial structural transformation from a cubic to a tetragonally distorted spinel Mn3O4, accompanied by the reduction of Mn4+ to Mn3+ and Mn2+ during discharge. TEM/EDX measurements confirmed that practically no Ca2+ was inserted upon discharge. However, non-negligible amounts of Zn were detected after Mn2O4 was reduced in the Zn2+ electrolyte, but through the formation of secondary phases that, in some cases, appeared adjacent to the surface of a cathode particle. This report aims to identify bottlenecks in the application of manganese oxide cathodes paired with Ca or Zn metal anodes and to justify future efforts in designing prototype multivalent batteries.

Magnesium-ion batteries are a promising energy storage technology because of their higher theoretical energy density and lower cost of raw materials. Among the major challenges has been the identification of cathode materials that demonstrate capacities and voltages similar to lithium-ion systems. Thiospinels represent an attractive choice for new Mg-ion cathode materials owing to their interconnected diffusion pathways and demonstrated high cation mobility in numerous systems. Reported magnesium thiospinels, however, contain redox inactive metals such as scandium or indium, or have low voltages, such as MgTi2S4. This article describes the direct synthesis and structural and electrochemical characterization of MgCr2S4, a new thiospinel containing the redox active metal chromium and discusses its physical properties and potential as a magnesium battery cathode. However, as chromium(III) is quite stable against oxidation in sulfides, removing magnesium from the material remains a significant challenge. Early attempts at both chemical and electrochemical demagnesiation are discussed.

Oxides undergoing reversible electrochemical cycling of Mg2+ ions would enable novel battery concepts beyond Li+, 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 Mg0.5Mn2.5O4 were prepared using colloidal synthesis, and their electrochemical activity is presented. Cycling in an aqueous Mg2+ 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 Mn4+, through the extraction of both Mg2+ and, in the first cycle, Mn2+ ions. Re-formation of the spinel upon reduction resulted in enrichment with Mg2+, indicating that its insertion is more favorable than that of Mn2+. 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.

Stabilization of electrode-electrolyte interfaces is required to increase the energy stored in battery electrodes. Introducing redox-inactive ions on the electrode surface minimizes deleterious side reactions without affecting the bulk properties. A synthetic challenge exists to grow such layers conformally at each primary particle, to fully passivate interfaces that are buried in the final electrode architecture. The development of methods of sequential colloidal growth of complex oxides and overlayers, enabled by surfactant interactions, would provide novel means to advance toward this goal. Here, nanocrystals composed of LiCoO2, a commercially relevant material for high energy devices, were grown with a shell enriched in Al3+, deposited conformally through a one-pot colloidal synthetic method. The effects of synthetic conditions on the composition of the Al-rich shell and the corresponding electrochemical performance were investigated. The modified nanocrystals showed enhanced electrochemical properties, while maintaining carrier transport.

Unlike the more established lithium-ion based energy storage chemistries, the complex intercalation chemistry of multivalent cations in a host lattice is not well understood, especially the relationship between the intercalating species solution chemistry and the prevalence and type of side reactions. Among multivalent metals, a promising model system can be based on nonaqueous Zn2+ ion chemistry. Several examples of these systems support the use of a Zn metal anode, and reversible intercalation cathodes have been reported. This study utilizes a combination of analytical tools to probe the chemistry of a nanostructured δ-MnO2 cathode in association with a nonaqueous acetonitrile–Zn(TFSI)2 electrolyte and a Zn metal anode. As many of the issues related to understanding a multivalent battery relate to the electrolyte–electrode interface, the high surface area of a nanostructured cathode provides a significant interface between the electrolyte and cathode host that maximizes the spectroscopic signal of any s...

Recently, new energy storage chemistries based on nonaqueous electrolytes and multivalent metals (e.g., Mg, Zn, Ca and Al) have drawn the attention of the researchers as a promising advanced energy storage technology due to their higher theoretical volumetric capacity, limited dendrite formation and low cost.1 A major developmental need for these systems is the identification of electrolytes compatible with both electrodes while showing reversible deposition/dissolution on an anode and multivalent intercalation into a cathode.1,2 In the case of nonaqueous Mg or Ca ion-based systems, electrolyte compatibility issues (e.g., low Coulombic efficiency, a high overpotential and corrosion) have held back the development of Mg or Ca metal batteries.3 However, the nonaqueous Zn2+ ion chemistry utilized in a Zn metal cells with a reversible intercalation cathode is an exception with a number of promising features including highly-efficient reversible Zn deposition/dissolution on a Zn metal anode with a wide electrochemical window,3 similar ionic radius compared with Li+ and Mg2+ ions,4 relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)5 and high volumetric capacity.1 Considering these advantages, a nonaqueous Zn system provides an opportunity to delve into the mechanisms in multivalent-ion cell chemistry and solve the present issues in multivalent cell design and prototyping.3 In this study, the intercalation chemistry on a variety of cathodes materials (e.g., V2O5, Mn2O4 and FePO4) have been investigated in various nonaqueous Zn electrolytes. The electrochemical and transport properties of the electrolytes (e.g., reversible Zn deposition, anodic/cathodic stability, ionic conductivity and diffusion coefficient) were characterized utilizing the experimental and computational analysis.3 Among various Zn metal cells, a Zn/nanostructured bilayered V2O5 cell with a selected acetonitrile(AN)-Zn(TFSI)2 electrolyte demonstrates good reversibility and stability for 120+ cycles with nearly 100% Coulombic efficiency and ~170 mAhg-1 of gravimetric capacity, albeit operating at a cell voltage of 0.7 V vs. Zn/Zn2+.6 A Zn/nanostructured layered δ-MnO2 cell with an AN-Zn(TFSI)2 electrolyte also shows good reversibility (~100% Coulombic efficiency) and stability for 50+ cycles with ~100 mAhg-1 capacity with an operating voltage of 1.2 V vs. Zn/Zn2+.7 By utilizing a combination of analytical tools, we address numerous factors affecting capacity fade, and issues associated with the second phase formation including Mn dissolution in Zn/δ-MnO2 cells that have been extensively cycled.7 References 1. J. Muldoon, C. B. Bucur and T. Gregory, Chem. Rev. 2014, 114, 11683-11720. 2. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279. 3. S.-D. Han, N. N. Rajput, X. Qu, B. Pan, M. He, M. S. Ferrandon, C. Liao, K. A. Persson and A. K. Burrell, ACS Appl. Mater. Inter. 2016, 8, 3021-3031. 4. R. D. Shannon, Acta Cryst. 1976, A32, 751-767. 5. Z. Rong, R. Malik, P. Canepa, G. Gautam, M. Liu, A. Jain, K. Persson and G. Ceder, Chem. Mater. 2015, 27, 6016-6021. 6. P. Senguttuvan, S.-D. Han, S. Kim, A. L. Lipson, S. Tepavcevic, T. T. Fister, I. D. Bloom, A. K. Burrell and C. S. Johnson, Adv. Energy Mater. 2016, 6, 1600826. 7. S.-D. Han, S. Kim, D. Li, V. Petkov, H. D. Yoo, P. J. Phillips, H. Wang, J. J. Kim, K. L. More, B. Key, R. F. Klie, J. Cabana, V. Stamenkovic, T. T. Fister, N. M. Markovic, A. K. Burrell, S. Tepavcevic, J. T. Vaughey, 2017, in revision.

Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V2O5, combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electron energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V2O5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV2O5 sample. Results suggest that the electrochemically cycled orthorhombic V2O5 cathode shows a local formation of the theoretically predicted epsilon-Mg0.5V(2)O(5) phase; however, the intercalation levels of Mg are lower than different from the chemically synthesized sample, which is found to represent the delta-MgV2O5 phase. predicted. This phase is

Lithiated ternary oxides containing nickel, cobalt, and manganese are intercalation compounds that are used as positive electrodes in high-energy lithium-ion batteries. These oxides undergo changes, when they are stored in humid air or exposed to moisture, that adversely affect their electrochemical performance. There is a newurgency to better understanding of these "weathering" mechanisms as manufacturing moves toward a more environmentally benign aqueous processing of the positive electrode. Delithiation of the oxide and the formation of lithium salts (such as hydroxides and carbonates) coating the surface, are known to occur during moisture exposure. The redox reactions which follow this delithiation are believed to trigger all the other transformations. In this article we suggest another possibility: namely, the proton-lithium exchange. We argue that this hypothesis provides a simple, comprehensive rationale for our observations, which include contraction of the c-axis (unit cell) lattice parameter, rock salt phase formation in the subsurface regions, presence of amorphous surface films, and the partial recovery of oxide capacity during electrochemical relithiation. The detrimental effects of water exposure need to be mitigated before aqueous processing of the positive electrode can find widespread adoption during cell manufacturing. (C) The Author(s) 2017. Published by ECS. All rights reserved.

Epitaxial strain, layer confinement, and inversion symmetry breaking have emerged as powerful new approaches to control the electronic and atomic-scale structural properties of complex metal oxides. Trivalent rare-earth (RE) nickelate RENiO3 heterostructures have been shown to be exemplars since the orbital occupancy, degeneracy, and, consequently, electronic/magnetic properties can be altered as a function of epitaxial strain, layer thickness, and superlattice structure. One recent example is the tricomponent LaTiO3-LaNiO3-LaAlO3 superlattice which exhibits charge transfer and orbital polarization as the result of its interfacial dipole electric field. A crucial step towards control of these parameters for future electronic and magnetic device applications is to develop an understanding of both the magnitude and range of the octahedral network's response towards interfacial strain and electric fields. An approach that provides atomic-scale resolution and sensitivity towards the local octahedral distortions and orbital occupancy is therefore required. Here, we employ atomic-resolution imaging coupled with electron spectroscopies and first-principles theory to examine the role of interfacial charge transfer and symmetry breaking in a tricomponent nickelate superlattice system. We find that nearly complete charge transfer occurs between the LaTiO3 and LaNiO3 layers, resulting in a mixed Ni2+/Ni3+ valence state. We further demonstrate that this charge transfer is highly localized with a range of about 1 unit cell within the LaNiO3 layers. We also show how Wannier-function-based electron counting provides a simple physical picture of the electron distribution that connects directly with formal valence charges. The results presented here provide important feedback to synthesis efforts aimed at stabilizing new electronic phases that are not accessible by conventional bulk or epitaxial film approaches.

Journal Article Aberration corrected STEM and High Resolution EELS study Investigating Magnesium Intercalation in Vanadium Pentoxide Cathode Get access Arijita Mukherjee, Arijita Mukherjee Department Of Physics, University Of Illinois At Chicago, 845 West Taylor Street, Chicago, Illinois 60607,United States Search for other works by this author on: Oxford Academic Google Scholar Niya Sa, Niya Sa Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States Search for other works by this author on: Oxford Academic Google Scholar P J Phillips, P J Phillips Department Of Physics, University Of Illinois At Chicago, 845 West Taylor Street, Chicago, Illinois 60607,United States Search for other works by this author on: Oxford Academic Google Scholar Justin Andrews, Justin Andrews Department Of Chemistry, Texas A&M University, Ross Street, College Station, Texas 77840 Search for other works by this author on: Oxford Academic Google Scholar Sarbajit Banerjee, Sarbajit Banerjee Department Of Chemistry, Texas A&M University, Ross Street, College Station, Texas 77840 Search for other works by this author on: Oxford Academic Google Scholar A K Burrell, A K Burrell Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States Search for other works by this author on: Oxford Academic Google Scholar R F Klie R F Klie Department Of Physics, University Of Illinois At Chicago, 845 West Taylor Street, Chicago, Illinois 60607,United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 22, Issue S3, 1 July 2016, Pages 1318–1319, https://doi.org/10.1017/S1431927616007431 Published: 25 July 2016

1. Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, MI 49933-1295, USA 2. Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, IL606077059, USA 3. Advanced Membranes and Porous Materials Center, King Abdullah University of Science & Technology, Thuwal, 23955-6900, Saudi Arabia 4. Department of Physics, University of Illinois at Chicago, Chicago, IL60607-7059, USA 5. Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA

Molybdenum Disulfide Catalyst for Lithium–Oxygen Batteries Mohammad Asadi1, Cong Liu2, Patrick Phillips3, Peter Zapol2, Robert F. Klie 3, Larry A. Curtiss2, Amin Salehi-Khojin1 1Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA 2Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA 3Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA Lithium–oxygen (Li-O2) batteries have been recognized as an emerging technology for energy storage systems owing to their high theoretical specific energy1 - 4. In this study, we discovered a system based on molybdenum disulfide (MoS2) nanoflakes and an ionic liquid (IL) that work together as an effective co-catalyst for discharge and charge in a Li-O2 battery. Cyclic voltammetry results show superior reaction rates for this co-catalyst at lower overpotentials for both oxygen reduction (15 mV) and evolution (20 mV) reactions compared to Au and Pt metal catalysts under identical experimental conditions. This MoS2/IL co-catalyst also performs remarkably well in the Li-O2battery system with 85% round-trip efficiency and reversibility up to 50 cycles. Deferential Electrochemical mass spectroscopy (DEMS), X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR) and Raman experiments were used to elucidate the cell performance. The results show the fully formation and decomposition of Li2O2 and demonstrate the cell cyclability and stability by the absence of any side products after 50 cycles charge and discharge. Atomic scale characterizations (STEM and EELS experiments) and DFT calculations were used to elucidate the mechanism by which the MoS2 nanoflakes and the ionic liquid electrolyte act together to promote the catalytic properties of the MoS2. The MoS2/IL co-catalyst discovered in this work provides new opportunities for exploiting the unique properties of ionic liquids such as their stability in Li-air batteries as well as activity of MoS2as a cathode material. Zu, C.-X. & Li, H. Thermodynamic analysis on energy densities of batteries. Energy Environ. Sci. 4, 2614 (2011). Rahman, M. A., Wang, X. & Wen, C. High Energy Density Metal-Air Batteries: A Review. J. Electrochem. Soc. 160, A1759–A1771 (2013). Zheng, J. P., Liang, R. Y., Hendrickson, M. & Plichta, E. J. Theoretical Energy Density of Li–Air Batteries. J. Electrochem. Soc. 155, A432 (2008). Shao, Y. et al. Electrocatalysts for Nonaqueous Lithium–Air Batteries: Status, Challenges, and Perspective. ACS Catal. 2, 844–857 (2012).

Chemical degradation at electrode/electrolyte interfaces in Li-ion batteries creates the challenge of designing stable cathode materials to avoid the loss of active cathode material at the interface of the cathode and electrolyte. Surface modification with non-active oxide is regarded as a valid strategy to decrease such degradation based on their role as electronic insulator between cathode and electrolyte. Although different oxides have been reported to enhance stability against chemical degradation, the realization of stability and durability of surface modified cathode materials is not well understood owing to the inhomogeneity and complex morphology of typical cathode powders and the resulting difficulty in properly characterizing the surface structure. Indeed, the specific chemical identity of the non-active oxide on the surface of cathode materials can vary. For instance, Al3+ can incorporate as amorphous Al2O3 or crystalline LiAlxCo1-xO2, among others. Herein, we directly synthesized well-defined LiCoO2 (LCO) nanocrystals with a hydrothermal process and employed as model cathode materials before coating 2nm uniform Al3+ oxide thin films on their surface and annealed at different temperatures. Phase analysis have confirmed that Al can be formed as Al2O3 at low temperature and as LiAlxCo1-xO2 at high temperature. Microscopy analysis presents direct proof of Al conformally coated on their surface. The electrochemical properties have demonstrated the different effect of coating with different Al-containing phases. Compared to bare LCO nanoplates, amorphous Al2O3 film coated on such nanoplates presents higher capacity and average stability whereas LiAlxCo1-xO2 coated film have much higher stability with average capacity. Data from atomic resolution TEM and solid state NMR will be discussed.

The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined with respect to layered-oxide cathode materials for battery applications. STEM-based methods are quickly becoming the most promising characterization tools for these materials, owed largely to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, and both energy-dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies. The current talk will focus on multiple Li-based, Mn-containing oxide cathode materials, for example, Li2MnO3 and Li(Ni0.5Co0.2Mn0.3)O2), characterized via STEM methods, in pristine, cycled, and in-situ irradiated states. The latter allows for single particle tracking of the dynamic processes occuring upon Li and O loss from the material, and is a form of accelerated ageing compared to the structural and electronic changes which occur upon electrochemical cycling. Various imaging modes, including high/low angle annular dark field (H/LAADF) and annular bright field (ABF), in conjunction with EELS/EDX, will be used extensively for this analysis, while parameters such as Mn valence, O presence, and light element occupation and intercalation will be discussed.

We examine the role of Ti doping in the incommensurately layered thermoelectric oxide material Ca3Co4O9 (CCO). The measured Seebeck coefficient of S = 135 μV/K in Ti-doped CCO thin films of composition Ca3Co3.8Ti0.2O9 indicates no significant enhancement of S compared to pristine CCO, thus confirming prior experimental results. Using a combination of aberration-corrected scanning transmission electron microscopy, electron energy-loss spectroscopy and first-principles computations, we determine the atomic and electronic structures of Ti-doped CCO, including the preferred location of Ti dopants and valence states of Ti and Co atoms. Our findings on the structural, electronic, and transport properties of the Ti-doped CCO are discussed in light of the previously published results.

Lithium- and Manganese-Rich Nickel-Manganese-Cobalt Oxides (LMR-NMC), nominally of composition x Li 2 MnO 3 •(1-x) LiMO 2 (with M a combination of Ni, Mn, and/or Co), present a high-voltage plateau (~4.5 V vs. Li/Li + ) in their capacity-voltage profile during the first delithiation cycle. This plateau is believed to result from activation of the Li 2 MnO 3 component, which makes additional lithium available for electrochemical cycling. Once activated (i.e., cycled beyond the activation plateau) the voltage v. capacity characteristic of LMR-NMC oxides is known to decrease continuously with cycling, resulting in a progressive loss of energy density. This phenomenon, commonly referred to as voltage fade, results in a gradual loss of energy density with cycling and constitutes one of the main barriers toward broad application of LMR-NMC as cathode materials for automotive applications. In this work we show evidence of voltage fade well below the activation plateau and its relation to structural changes during LMR-NMC cycling. We argue that voltage fade results from a gradual accumulation of spinel environments in the crystal structure. Some of these spinel sites result from lithium deficiencies during oxide synthesis and are likely to be at the particle surfaces; other sites result from the migration of transition metal atoms in the partially-delithiated LiMO 2 component into the lithium planes during electrochemical cycling. We also present evidence that these structural changes are related to the oxygen-to-metal ratio and could be driving oxygen evolution from LMR-NMC materials which, as a potential trigger of thermal runaway, is a process of fundamental concern for safety. Acknowledgment: The submitted issue has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-Eng-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, non-exclusive, irrevocable, worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Structured light provides an additional degree of freedom for modern optics and practical applications.The effective generation of orbital angular momentum (OAM) lasing, especially at a microand nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAMmode.The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAMmicrolaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.

Rhenium alloys exhibit a unique combination of chemical, physical, and mechanical properties that makes them attractive for a variety of applications. Herein, we present atomic‐scale structural and atomic part‐per‐million level three‐dimensional (3D) chemical characterization of a Re–Ni coating, combining aberration‐corrected scanning transmission electron microscopy (STEM) and atom‐probe tomography (APT). A unique combination of a columnar and multilayer structure is formed by single‐bath dc‐electroplating and is reported here for the first time. Alternating thicker Re‐rich and thinner Ni‐rich layers support a mechanism in which Ni acts as a reducing agent. The multilayers exhibit hetero‐epitaxial growth resulting in high residual shear stresses that lead to formation of corrugated interfaces and an outer layer with mud‐cracks.

Combined cycling stability at high energy density is required for lithium ion battery to meet the criteria for use in electric vehicles. In generally, material utilization and rate capability are enhanced at small particle sizes. [1] Reduced size of electrode materials can enhance the rate of lithium ions because of shortened diffusion pathway and increases surface area to induces facile access by the electrolyte. In contrast, chemical degradation at electrode-electrolyte interface is also facilitated by large contact area with nanoparticle electrode. Unfavorable interfacial reactions such as dissolution of active materials and decomposition of electrolyte mainly occur because the surface of active materials is energetically unstable. [2] In order to minimize side reactions that can negatively affect to electrochemical performance, replacing electrochemically inactive ions on the surface of active materials can improve the interfacial stability. However, this substitution should take place as thin passivating layers on individual particles to preserve storage capacity. [3] Herein, we demonstrate a strategy toward the stabilization of interfaces by introducing core-shell type of nanocrystals that is composed of electroactive transition metal oxide in core and ultra-thin inactive epitaxial oxide shell on the surface. To prove this concept, we introduce layered LixCoO2 nanocrystals as a core component, with Al-rich shells as passivation layer to minimize side reaction with electrolyte. The resulting materials shows stable cycling curves as well as higher capacity retention at high rate of charging and discharging reaction compared to bare LixCoO2. References 1. Isaac D. Scott, Yoon Seok Jung, Andrew S. Cavanagh, Yanfa Yan, Anne C. Dillon, Steven M. George, and Se-Hee Lee, Nano Letters, 414–418, 11 (2011). 2. Peter G. Bruce, Bruno Scrosati, and Jean-Marie Tarascon, Angew. Chem. Int. Ed, 2930-2946, 47 (2008). 3. Chunjoong Kim, Patrick J. Phillips, Linping Xu, Angang Dong, Raffaella Buonsanti, Robert F. Klie, and Jordi Cabana, Chem. Matter, 394-399, 27 (2014). Figure. (a) Evolution of specific capacity (solid symbol) and coulombic efficiency (open symbol) in cycling at C/20, (b) electron microscopic image, (c) EELS for Al and (d) EELS for Co atom of LixCoO2 with Al rich shell nanocrystals. Figure 1