Search

Irreversible structural transformation in intercalation-type cathode materials, which has been frequently observed, has been perceived as a principal cause of capacity fading and voltage decay in (...

Calcium-ion batteries (CIBs) are under investigation as next-generation energy storage devices due to their theoretically high operating potentials and lower costs tied to the high natural abundanc...

Nonaqueous Mg batteries can theoretically reach high energy density with cost-effective materials, yet no such device to date has performance competitive with Li-ion technologies. A major barrier i...

Lattice Mg2+ in a tailored solid solution spinel, MgCrMnO4, is electrochemically utilized at high Mn-redox potentials in a nonaqueous electrolyte. Complementary evidence from experimental and theor...

The use of oxide cathodes in Mg batteries would unlock a potential energy storage system that delivers high energy density. However, poor kinetics of Mg diffusion in known solid oxide lattices stro...

Mg migration in oxide spinels is impeded by strong affinity between divalent Mg and oxygen, suggesting a necessity of exploring new chemistry of solid lattices for functional Mg-ion electrode mater...

Mg batteries utilizing oxide cathodes can theoretically surpass the energy density of current Li-ion technologies. The absence of functional devices so far has been ascribed to impeded Mg2+ migrati...

A promising high-voltage spinel oxide cathode material MgCrMnO4 with 18% Mg/Mn inversion was synthesized successfully. A new custom operando battery device was designed to study the cation migration mechanisms of the MgCrMnO4 cathode using 0.1 M Mg(TPFA)2 electrolyte dissolved in triglyme and activated carbon as the anode. For the first time in multivalent batteries, high-quality operando diffraction data enabled the accurate quantification of cation contents in the host structure. Besides the exceptional reversibility of 12% Mg2+ insertion in Mg1-xCrMnO4 (x ≤ 1), a partially reversible insertion of excess Mg2+ during overdischarging was also observed. Moreover, the insertion/extraction reaction was experimentally shown to be accompanied by a series of cation redistributions in the spinel framework, which were further supported by density functional theory calculations. The inverted Mn is believed to be directly involved in the cation migrations, which would cause voltage hysteresis and irreversible structural evolution after overdischarging. Tuning the Mg/Mn inversion rate could provide a direct path to further optimize spinel oxide cathodes for Mg-ion batteries, and more generally, the operando techniques developed in this work should play a key role in understanding the complex mechanisms involved in multivalent ion insertion systems.

We report the discovery of a new zero-strain cathode, LiCo1–xAlxO2 (0 < x ≤ 0.5), which has a lithiated spinel structure synthesized at “low temperature” (LT). Lithiated spinel LiCo1–xAlxO2 operate...

While α-V2O5 has traditionally been considered as a promising oxide to reversibly intercalate high levels of Mg2+ at high potential, recent reports indicate that previously observed electrochemical...

Building a stable chemical environment at the cathode/electrolyte interface is directly linked to the durability of Li-ion batteries with high energy density. Recently, colloidal chemistry methods have enabled the design of core-shell nanocrystals of Li1+ xMn2- xO4, an important battery cathode, with passivating shells rich in Al3+ through a colloidal synthetic route. These heterostructures combine the presence of redox-inactive ions on the surface to minimize undesired reactions, with the coverage of each individual particle in an epitaxial manner. Although they improve electrode performance, the exact chemistry and structure of the shell as well as the precise effect of the ratio between the shell and the active core remain to be elucidated. Correlation of these parameters to electrode properties would serve to tailor the heterostructure design toward complete shutdown of undesired reactions. These knowledge gaps are the target of this study. Li1+ xMn2- xO4 nanocrystals with Al3+-rich shells of different thicknesses were synthesized. Multimodal characterization comprehensively revealed the elemental distribution, electronic state, and crystallinity in the heterostructures, which confirmed the potential of this approach to finely tune passivating layers. All of the modified nanocrystals improved the capacity retention while retaining charge storage compared to the bare counterpart, even under harsh conditions.

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+. Incorpo...

Undesired reactions at the interface between a transition metal oxide cathode and a nonaqueous electrolyte bring about challenges to the performance of Li-ion batteries in the form of compromised durability. These challenges are especially severe in extreme conditions, such as above room temperature or at high potentials. The ongoing push to increase the energy density of Li-ion batteries to break through the existing barriers of application in electric vehicles creates a compelling need to address these inefficiencies. This goal requires a combination of deep knowledge of the mechanisms underpinning reactivity, and the ability to assemble multifunctional electrode systems where different components synergistically extend cycle life by imparting interfacial stability, while maintaining, or even increasing, capacity and potential of operation. The barriers toward energy storage at high density apply equally in Li-ion, the leading technology in the battery market, and in related, emerging concepts for high energy density, such as Na-ion and Mg-ion, because they also conceptually rely on electroactive transition metal oxides. Therefore, their relevance is broad and the quest for solutions inevitable. In this Account, we describe mechanisms of reaction that can degrade the interface between a Li-ion battery electrolyte and the cathode, based on an oxide with transition metals that can reach high formal oxidation states. The focus is placed on cathodes that deliver high capacity and operate at high potential because their development would enable Li-ion battery technologies with high capacity for energy storage. Electrode-electrolyte instabilities will be identified beyond the intrinsic potential windows of stability, by linking them to the electroactive transition metals present at the surface of the electrode. These instabilities result in irreversible transformations at these interfaces, with formation of insulating layers that impede transport or material loss due to corrosion. As a result, strategies that screen the reactive surface of the oxide, while reducing the transition metal content by introducing inactive ions emerge as a logical means toward interfacial stability. Yet they must be implemented in the form of thin passivating barriers to avoid unacceptable losses in storage capacity. This Account subsequently describes our current ability to build composite structures that include the active material and phases designed to address deleterious reactions. We will discuss emerging strategies that move beyond the application of such barriers on premade agglomerated powders of the material of interest. The need for these strategies will be rationalized by the goal to effectively passivate all interfaces while fully controlling the chemistry that results at the surface and its homogeneity. Such outcomes would successfully minimize interfacial losses, thereby leading to materials that exceed the charge storage and life capabilities possible today. Practically speaking, it would create opportunities to design batteries that break the existing barriers of energy density.

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.

Building a stable chemical environment at the cathode/electrolyte interface is directly linked to the durability of Li-ion batteries with high energy density. Recently, colloidal chemistry methods have enabled the design of core-shell nanocrystals of Li

Recent progress in the field of scanning/transmission electron microscopy (S/TEM) has resulted in intense electron probes providing an ultra-high spatial (e.g. sub-Å) and energy (3 meV) resolution, with a previously unattainable signal-to-noise ratio. Furthermore, the STEM-based methods: direct imaging of both heavy and light elements, and both the energy-dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies are becoming the most promising characterization tools for battery materials, providing an unprecedented opportunity to probe the evolution of structure and electronic state of the cathodes following their electrochemical activity. The current talk will focus on the electron microscopy characterization of various materials that are considered as potential cathodes for the multivalent batteries, including transition metal (TM) oxides and polyanionic compounds. Materials were characterized using aberration-corrected JEOL JEM-ARM200CF, equipped with a cold field emission and operated at 200 kV, in pristine, cycled, and in-situ irradiated phases exploring their structure, chemistry, and electronic states. The in-situ technique mimics the electrochemical cell and allows for single-particle tracking of the dynamic processes occurring upon oxygen loss from the material providing helpful knowledge to further strengthen the understanding of the electrochemical activity of the cathodes. Several imaging modes, including high/low angle annular dark field (H/LAADF) and annular bright field (ABF), in conjunction with EELS/EDX, were used extensively for the analysis. Various parameters such as TM valence, phase transition, oxygen deficiency, and multivalent ion intercalation will be discussed.

The capability of the tailored solid-solution spinel, MgCrMnO4, is evaluated by theoretical and experimental approaches. Lattice Mg2+ in the designed oxide is electrochemically utilized at high potentials in a non-aqueous electrolyte. Complementary evidence supports bulk Mg2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg2+ and O2- exists. Mg/Mn antisite inversion in the spinel is lowered via post-annealing to further improve Mg+2 mobility. Spinel lattice is preserved upon removal of Mg2+ without any phase transformations, denoting structural stability at the charged state at a high potential. In the remagnesiated state, insertion of Mg2+ into interstitial sites in the spinel is detected possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.

Multivalent (MV) ion batteries have been under intense scrutiny because the modeling effort predicted that a high Mg2+ diffusion mobility in spinel cathodes and a higher specific energy density can be achieved. Recently new cathodes have been tested against Mg, with novel cathodes such as layered oxides MoO2.8F0.2,1 MgCr2-xVxO4,2 and conversion-type cathodes.3 Previously chloride containing electrolytes4 were dominant in multivalent ion batteries because of their facile deposition and high Coulombic efficiency towards the anode. However, the corrosion issue of Cl- limits their application. Here we report the development of chloride-free multivalent salts with a weakly coordinating anion that shows exceptional electrochemical properties. Moreover, the passivation-free properties of these anions make them efficient in assessing the Mg2+ mobility inside a solid solution electrode. Further development on other multivalent cations will also be demonstrated. Together with cathodes, these electrolyte developments would pave the way for a holistic approach towards high energy density multivalent batteries. References T. Incorvati, L. F. Wan, B. Key, D. Zhou, C. Liao, L. Fuoco, M. Holland, H. Wang, D. Prendergast, K. R. Poeppelmeier, Chemistry of Materials 2015, 28, 17-20. J. Kwon, K.-C. Lau, H. Park, Y. A. Wu, K. L. Hawthorne, H. Li, S. Kim, I. L. Bolotin, T. T. Fister, P. Zapol, R. F. Klie, J. Cabana, C. Liao, S. H. Lapidus, B. Key, J. T. Vaughey, Chemistry of Materials 2019. DOI:10.1021/acs.chemmater.9b04206 Pan, J. Huang, Z. Feng, L. Zeng, M. He, L. Zhang, J. T. Vaughey, M. J. Bedzyk, P. Fenter, Z. Zhang, C. Liao, Advanced Energy Materials 2016, 6. Pan, J. Huang, N. Sa, S. M. Brombosz, J. T. Vaughey, L. Zhang, A. K. Burrell, Z. Zhang, C. Liao, * Journal of The Electrochemical Society 2016, 163, A1672-A1677. -C. Lau, T. J. Seguin, E. V. Carino, N. T. Hahn, J. G. Connell, B. J. Ingram, K. A. Persson, K. R. Zavadil, C. Liao, * J. Electrochem. Soc. 2019, 166, A1510-A1519.

The market for electric vehicles has increased significantly in the recent decade. Thus lithium-ion batteries with high energy and power density, with the ability to withstand extreme cycling environments are necessary to compete with the flexibility of the fossil fuel reliant combustion engine. The main instabilities in the Li-ion battery can be traced to the electrode-electrolyte interface, here electroactive transition metals react with the electrolyte resulting in irreversible transitions forming insulating layers, or solid cathode electrolyte interfaces (CEI), that inhibit ion transport. Cathode material dissolution may also occur at the surface due to acidic attack from the HF byproduct from the decomposition of the LiPF6 electrolyte. During electrochemical cycling, uneven lithium diffusion causes the surface to become more reduced than the core which leads to structural changes which impedes ion transport. These structural changes cause nonuniform contraction and expansion of the lattice loosening connections between the transition metal oxide layers eventually leading to severe macroscopic cracking. This effect has been seen at lower cycling rates when particle size is increased. The cracks allow the electrolyte to permeate the particle allowing CEI formation within the particle greatly decreasing the cathode life. A solution to these detrimental surface interactions is by replacing the electroactive transition metal content at the surface with inactive ions improving the interfacial stability. To prevent significant decreases in storage capacity the coating is a thin passivating barrier. Previously our group has introduced a strategy toward stabilizing the electrode-electrolyte interface using Ni0.25Mn0.25Co0.50O nanocrystals (NC) of active material. Each individual NC is passivated by an epitaxial grown conformal ultrathin Al2O3 shell with a final composition of LiCo0.5Ni0.25Mn0.25O2 with a concentration gradient of Al3+ ions toward the outer layers after high temperature lithiation. This material showed increased cycling stability under harsh conditions of increased cycle rate and temperature. While this research had promising results, industrial methods are currently better suited to produce well defined dense secondary particle structures with a spherical morphology, made up of agglomerated nanoparticles. While many coating methods being researched on these secondary structures require coating materials to be deposited on as-made, pre-lithiated cathode material, this method makes it difficult to completely coat all surfaces, while losing the ability to control surface chemistry and homogeneity. Here an optimized systematic study was performed to form an aluminum shell in the same process of growth of NixMnzCoy(OH)2 (NMC) precursors. This procedure affords precise control over shell thickness and concentration gradient architectures. The core-shell precursors are reacted with LiOH in a high-temperature solid-state reaction, allowing the aluminum shell to diffuse into the surface lattice which will further suppress phase distortion in the bulk. The higher concentration of Al3+ at the surface protects against side reactions with the electrolyte. These secondary structured LiNi0.25Mn0.25Co0.50O2 were electrochemically tested using both Li-metal half cells and graphite anode full cells and the results were compared to nanocrystalline primary particles of a similar composition. While aluminum coatings have been studied on cathode material previously, it is still a challenge to determine finite spatial changes in distribution of elements within individual particles in 3D with current conventional methods available, such as SEM-EDS analysis. In this study, synchrotron-based imaging methods of X-ray fluorescence (XRF) nanoprobe cross-sectional mapping, XRF tomography, and transmission X-ray elemental tomography were used to evaluate aluminum coated gradient NMC material and other stabilized architectures of interest such as full concentration gradient NMC material. For tomographic measurements particles were loaded into 50-micron capillaries allowing for high throughput imaging. These techniques allowed for little sample manipulation which preserved sample morphology in pristine state. Increased resolution offered further insight into elemental distribution and extent of aluminum migration after high temperature lithiation. Advancements in these imaging techniques can better inform the future of stabilized cathode architecture design. Figure 1

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.

We report on the aerosol synthesis and optical characterization of ZnO/unoxidized graphene (UG) platelets nanocomposite films with high optical transparency (>85% at visible wavelengths). The ZnO/UG composite films, in which UG nanoplatelets are embedded in nano-grained ZnO, were fabricated from colloidal suspensions of UG platelets with an aqueous zinc precursor. From photoluminescence (PL) spectra of the UG composite films, it was found that PL intensity decreases with the addition of UG platelets. The features of PL intensity in the UG composites are in contrast to that of ZnO/graphene oxide (G-O) platelets composites, and can be explained by the absence of an oxygen vacancy filling effect, due to the unoxidized nature of UG and an increase in defect sites in its composites. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Zero-strain electrode materials that exhibit extremely small volume changes during intercalation reactions provide unique opportunities for highly stable lithium batteries. In particular, intecalation-induced strain in electrodes is a major factor in the degradation of advanced lithium batteries. For example, recent studies of high-performance Ni-rich layered cathodes unequivocally show a clear correlation between particle fracture, due to anisotropic volume expansion of polycrystalline grains, and continuously increasing cathode impedance.[1] Such chemo-mechanical behavior of electrode materials is even more critical to all-solid-state batteries in which the solid-solid interface between the electrode and solid electrolyte is prone to cracking and disintegration, even with small volume mismatches during electrochemical cycling. The best known zero-strain electrode material is the Ti-based spinel, Li4Ti5O12, that has been developed as a stable anode. Recently, LiRh2O4 spinel has been reported as a zero-strain cathode that operates at 3.2 V vs. Li/Li+,[2] however, its practical use is limited by the high cost of the precious metal, rhodium. A more feasible zero-strain cathode candidate is the ‘low-temperature’ (LT) form of LiCoO2, which adopts a cubic, lithiated spinel structure, Li2[Co2]O4.[3,4] On lithium extraction, LT-LiCoO2 provides an attractive 3.6 V vs Li. However, despite the high operating voltage and minimal volume change, this zero-strain material has received little attention since its discovery because of its poor cycling stability. In this presentation we report that cation substitution greatly improves the electrochemical perperties of LT-LiCo1-xMxO2 electrodes (M = cations). The different effects of various cation substituents on electrode performance will be compared and the zero-strain intercalation mechanism in LT-LiCo1-xMxO2 will be discussed. References [1] D. Miller, C. Proff, D.P. Abraham, and J. Bareno, Adv. Energy Mater., 3, 1098 (2013). [2] Y. Gu, K. Taniguchi, R. Tajima, S.-i. Nishimura, D. Hashizume, A. Yamada, and H. Takagi, J. Mater. Chem. A 1, 6550 (2013). [3] R.J. Gummow, M.M. Thackeray, W.I.F. David, and S. Hull, Mater. Res. Bull., 27, 327 (1992). [4] E. Lee, J. Blauwkamp, F.C. Castro, J. Wu, V.P. Dravid, P. Yan, C. Wang, S. Kim, C. Wolverton, R. Benedek, F. Dogan, J.S. Park, J.R. Croy, and M.M. Thackeray, ACS Appl. Mater. Inter., 8, 27720 (2016).

Carbamoylphosphate (CMPO) [CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl)acetamide]silane, as a functional self-assembled molecules, grafted mesoporous silicates were prepared by simple hydrolysis and condensation reaction. Pore sized tailored mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The surface area of ordered mesoporous silicates was ranged from 680 to 1310 with different pore diameters that estimated to be ca. 2.3~9.1 nm by BJH method. Among the OMMs host materials, SBA-15(II) has higher loading ratio (~35 wt%) of CMPO derivative than other OMMs. Accessibility to CMPO silane functional groups in the surface of mesoporous silicas was studied by lanthanide ions sorption experiments. All of the CMPO modified OMMs favors the smaller Eu(III) and Nd(III) cations than La(III) for relative larger ionic radius.

In this study, we have successfully developed 3-[131I]iodo-tyrosine grafted Fe3O4@SiO2 nanocomposites for dual potential tumor imaging agent for SPECT and MRI. Fe3O4 nanoparticle was synthesized through thermal decomposition and Fe3O4@SiO2 was prepared by reverse microemulsion method. After conjugating aminopropyltriethoxysiliane, L-tyrosine was introduced by amide coupling reaction. Finally, [131I]iodide was labeled on L-tyrosine grafted Fe3O4@SiO2 nanocomposite by aromatic iodination using chloramine-T.

Stabilization of high energy cathode-electrolyte interface is required to meet the criteria for the power source and stable cycling performance in Li-ion batteries. [1] The undesired reactions at the interface could be minimized by introducing redox-inactive ions on the surface of active materials without affecting original properties. [2] To demonstrate the roles of passivating layers more effectively, high energy nanocrystals were introduced due to its high surface area that can induce access of charges with electrolytes, accelerating chemical degradation at the interface. [3] A synthetic method based on colloidal chemistry was employed to grow a thin shell enriched in Al3+ in the same reaction environment where the particles were grown in dispersible form, ensuring effective coverage of all surfaces. The resultant core-shell nanocrystal consists of active lithium transition metal oxides as a core and enriched Al3+ shells as a passivating layers to suppress the unfavorable reaction on the surface. Careful post-synthetic annealing was used to produce the final heterostructures and tailor the specific chemistry of the shells. The modified nanocrystals improved capacity retentions in various conditions, such as elevated temperature and high applying potentials compared to the bare counterpart where a shell is not presented, strongly suggesting a role of protective layers. The chemical identity and specific structural information of the bulk and passivation layers were mainly characterized by a combination of solid state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and X-ray absorption spectroscopy (XAS). Reference Lee, K. T.; Jeong, S.; Cho, J. Acc. Chem. Res, 2013, 46, 1161-1170. Kim, C.; Phillips, P. J.; Xu, L. P.; Dong, A. G.; Buonsanti, R.; Klie, R. F.; Cabana, J. Chem. Mater, 2015, 27, 394-399. Bruce, P. G.; Scrosati, B.; Tarascon, J. M. Angew. Chem. Int. Ed, 2008, 47, 2930-2946.

A novel synthetic route has been developed to prepare α-cobalt hydroxide with intercalated nitrate anions. It was success-fully synthesized by γ-ray irradiation under simple conditions, i.e., air atmosphere, without base. Under γ-ray irradiation, it leads to the formation of layered cobalt hydroxynitrate compounds which have small crystalline size and have the role of a generator of hydroxyl anion. Structural and morphological characterizations were performed by using power X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). The component and thermal stability of the sample were respectively measured by Fourier trans-form infrared (FT-IR) spectroscopy, elemental analysis, and thermal analyses, including thermogravimetry (TG) and differential thermal analysis (DTA).

The carbamoylphosphosphonate silane (CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl) acetamide) modified mesoporous silica was prepared via a post-synthesis grafting method for the effective purification of rare earth elements. The guest CMPO analogue was synthesized by direct coupling reaction of 2-(diphenylphosphoryl) acetic acid and 3-(triethoxysilyl)propan-1-amine. Various mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The resulting surface-modified mesoporous materials were characterized with respect to their structural integrity, surface area, and pore size and the concentration of the CMPO silane species. These CMPO functionalized periodic mesostructured silicates offer the potential of applications as catalysts, sensors, or environmental sorbents.

SnO 2 -pillared titanate nanohybrid has been prepared by reacting the exfoliated layered titanate sheets with the nanosized SnO 2 sol particles. The stable two-dimensional colloidal nanosheets could be obtained by intercalating tetrabutylammonium cation into the layered protonic titanate, H x Ti 2− x /4 □ x /4 O 4 ·H 2 O ( x =0.67) with a lepidocrocite-like structure, and by successive exfoliation process in an aqueous solution. Monodispersed SnO 2 nano sol particles were prepared by hydrolysis of SnCl 4 ·5H 2 O in the presence of sodium hydroxide, and then the exfoliated titanate suspension was mixed with SnO 2 nano sol solution until the flocculated products formed. The final product was heated at various temperatures in order to complete the grafting reaction of intercalated SnO 2 nano sol on the interlayer surface of layered titanate. Inductive coupled plasma, X-ray diffraction, thermal analysis and N 2 -adsorption–desorption isotherms were carried out to study the hybridizing process and the structure of SnO 2 -pillared titanate nanohybrid.

Stable cycling performance with high power density in lithium ion battery (LIBs) is required to meet the criteria for the power source such as electric vehicles. But generally, high power density is hindered by slow diffusion of lithium ions in micrometric electrode materials. [1] From this perspective, nanoparticle electrode materials can enhance the rate of lithium ions because of shortened diffusion pathway of lithium ion. Besides, high surface area of electrode induces facile access of charge via large contact area with electrolyte and conducting additives like carbon. 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 cathode species and decomposition of electrolyte mainly occur through energetically unstable surfaces of the active material. [2] In order to minimize side reactions that can negatively affect electrochemical performance, introducing 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] A strategy toward the stabilization of electrode-electrolyte interfaces has been devised by introducing core-shell nanocrystals, consisting of electroactive lithium transition metal oxide cores and ultra-thin inactive epitaxial oxide shells on the surface. Spinel Li1+xMn2-xO4 nanocrystals were used as a core component, with an Al-rich shell as passivation layers to minimize unfavorable reaction on the surface of cathode particles. The electrochemical performance shows that Spinel Li1+xMn2-xO4 nanoparticle with conformal shell reveals improved capacity retention and rate capability even at elevated temperature, compared to a bare counterpart. Reference 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).

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

High power density and excellent cycling stability in lithium ion battery (LIBs) are required to meet the criteria for the power source such as electric vehicles. Higher power density is generally hindered by sluggish diffusion of Li ions in micrometric materials commonly adopted in LIBs.[1] Size reduction of active materials can significantly improve the rate of lithium ions because of the shortened length of diffusion path. In the meantime, high surface area enables facile access of charges via large contact area with the electrolyte or electronic conducting additives. In this perspective, much effort have been devoted to the nanosized particles, which report the high power density that cannot be achieved from the micrometric counterparts. However, in return, increased surface area of particles can lead to the vigorous unfavorable interfacial reaction that mainly occurs through the energetically unstable surface such as dissolution of active materials and decomposition of electrolyte.[2] Reducing the active transition metal in the vicinity of the surface by partially replacing inactive ions can improve the interfacial stability, but must be prepared as the form of thin passivating barriers to preserve storage capacity. Post-synthetic coating procedure with stable phases such as Al2O3 and MgO, has been performed on the surface of particles as the most common approach,[3] however, it is difficult for coating phases to access buried interfaces because of agglomerated feature of the particles. Herein, Mn3O4 nanocrystals (NCs) were synthesized by thermal decomposition of manganese acetate in oleylamine and an ultra-thin shell layers that are enriched in aluminum were introduced, finally leading to the formation of core-shell (C-S) NCs. The particle size of Mn3O4 and C-S NCs were approximately 21 nm and 24 nm, respectively, as shown in Figure 1. The atomic ratio of Al/Mn in C-S NCs was found to be ~0.2 by energy dispersive X-ray spectroscopy (EDX). The crystal structures of Mn3O4 and C-S NCs were studied using X-ray diffraction (XRD) in Figure 2, both of which matched with a tetragonal spinel structures (I41amd, JCPDS card # 55492) without any peaks related to Al2O3. In order to study composition and microstructure of the shell layer, the scanning transmission electron microscopy (STEM) will be carried out. C-S LiMn2O4 NCs are prepared by mixing precursor C-S NCs and Li sources followed by thermal treatment. The electrochemical properties will be evaluated in Li metal half cells compared to the counterpart without shell layer. The effect of the shell layer on the electrochemical stability will be discussed. Fig. 1. TEM images of (a) Mn3O4 and (b) C-S NCs. Magnified images are shown in the insets (Scale bars of (a) and (b) are 5 nm and 10 nm, respectively). Fig. 2. XRD patterns of (a) Mn3O4 and (b) C-S NCs, which match well with a tetragonal phase Reference: 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). Peter G. Bruce, Bruno Scrosati, and Jean-Marie Tarascon, Angew. Chem. Int. Ed, 2930-2946, 47 (2008). Jun Liu and Arumugam Manthiram, Chem. Mater. 1695-1707, 21 (2009). Figure 1

Graphene/inorganic hybrid structures have attracted increasing attention in research aimed at producing advanced optoelectronic devices and sensors. Herein, we report on aerosol synthesis of new graphene-embedded zinc oxide (ZnO) films with higher optical transparency (80% at visible wavelengths), improved electrical conductivity (2 orders of magnitude, ∼ 20 kΩ/□), and enhanced photoluminescence (∼ 3 times), as compared to bare ZnO film. The ZnO/graphene composite films, in which reduced graphene oxide nanoplatelets (∼ 4 nm thick) are embedded in nanograined ZnO (∼ 50 nm in grain size), were fabricated from colloidal suspensions of graphene oxide with an aqueous zinc precursor. These new luminescent ZnO/graphene composites, with high optical transparency and improved electrical conductivity, are promising materials for use in optoelectronic devices.