Correlating Nanoscale Structures with Electrochemical Properties of Solid Electrolyte Interphases in Solid-State Battery Electrodes.

Here, we investigate the nonlinear relationship between the content of solid electrolytes in composite electrodes and the irreversible capacity via the degree of nanoscale uniformity of the surface morphology and chemical composition of the solid electrolyte interphase (SEI) layer. Using electrochemical strain microscopy (ESM) and X-ray photoelectron spectroscopy (XPS), changes of the chemical composition and morphology (Li and F distribution) in SEI layers on the electrodes as a function of solid electrolyte contents are analyzed. As a result, we find that the solid electrolyte content affects the variation of the SEI layer thickness and chemical distributions of Li and F ions in the SEI layer, which, in turn, influence the Coulombic efficiency. This correlation determines the composition of the composite electrode surface that can maximize the physical and chemical uniformity of the solid electrolyte on the electrode, which is a key parameter to increase electrochemical performance in solid-state batteries.

Influence of inhomogeneity of the polymerization light beam on the microhardness of resin cement under a CAD-CAM block.

STATEMENT OF PROBLEM: The beam profile of a light polymerization unit shows an inhomogeneous distribution. Therefore, the light passing through indirect restorations may be inhomogeneous and affect the polymerization of the resin cement. PURPOSE: The purpose of this in vitro study was to investigate the effects of the inhomogeneous distribution of irradiance passing through a computer-aided design and computer-aided manufacturing (CAD-CAM) block on the microhardness of resin cement. MATERIAL AND METHODS: IPS e.max CAD (A3 LT, A3 HT), Celtra Duo (A3 LT), LAVA Ultimate (A3 LT), and Vita Enamic (A3 T) blocks were tested and cut into 1.0-, 1.5-, 2.0-, and 4.0-mm thicknesses (N=100). The resin cements were Variolink N base (light-polymerized) and RelyX U200 (dual-polymerized). The light transmission, irradiance, and beam profile of each block were measured. For microhardness measurement, 5 points (-4 mm, -2 mm, 0 mm, +2 mm, and +4 mm) that coincided with the distance from the center to the periphery of the tip were marked on the specimen's surface. At each point, microhardness was measured 24 hours after polymerization. Repeated measured 1-way ANOVA with the LSD test was performed to analyze the effect of measuring points on the microhardness (α=.05). RESULTS: The microhardness of the resin cements decreased with an increase of the CAD-CAM block thickness (P<.05). Resin cements under a 1-mm CAD-CAM block showed relatively uniform microhardness, whereas those under 2-mm and 4-mm blocks showed inhomogeneous microhardness (P<.05). CONCLUSIONS: Inhomogeneous light transmission from a light polymerization unit through CAD-CAM blocks resulted in the nonuniform microhardness of resin cement.

Graphene Oxide Induced Surface Modification for Functional Separators in Lithium Secondary Batteries.

Functional separators, which have additional functions apart from the ionic conduction and electronic insulation of conventional separators, are highly in demand to realize the development of advanced lithium ion secondary batteries with high safety, high power density, and so on. Their fabrication is simply performed by additional deposition of diverse functional materials on conventional separators. However, the hydrophobic wetting nature of conventional separators induces the polarity-dependent wetting feature of slurries. Thus, an eco-friendly coating process of water-based slurry that is highly polar is hard to realize, which restricts the use of various functional materials dispersible in the polar solvent. This paper presents a surface modification of conventional separators that uses a solution-based coating of graphene oxide with a hydrophilic group. The simple method enables the large-scale tuning of surface wetting properties by altering the morphology and the surface polarity of conventional separators, without significant degradation of lithium ion transport. On the surface modified separator, superior wetting properties are realized and a functional separator, applicable to lithium metal secondary batteries, is demonstrated as an example. We believe that this simple surface modification using graphene oxide contributes to successful fabrication of various functional separators that are suitable for advanced secondary batteries.

Preparation and Electrochemical Behaviors of Sulfur-Containing Electrodes as a Function of Thermal Treatment Temperature.

Zeolitic imidazolate framework-sulfur composites were synthesized by a simple solvothermal reaction. Furthermore, following thermal treatment enable electrochemical properties to be improved. In order to investigate optimal temperature, we conducted thermal treatment as a function of different temperature. The morphology of the composites was examined by Field Emission Scanning Electron Microscopy and Fourier Transform Infra-red Spectroscopy. Electrochemical characterizations were also conducted by cyclic voltammetry and Galvanostatic charge-discharge tests. Based on these electrochemical experiments, the sample treated at 900 °C indicated the highest initial specific capacity and retention property in this study. From the results of this study, sulfurcontaining composite treated at higher temperature showed the better characteristics of electrochemical performance.

Bimodal phase separated block copolymer/homopolymer blends self-assembly for hierarchical porous metal nanomesh electrodes.

Transparent conducting electrodes (TCEs) are essential components in various optoelectronic devices. Nanostructured metallic thin film is one of the promising candidates to complement current metal oxide films, such as ITO, where high cost rare earth elements have been a longstanding issue. Herein, we present that multiscale porous metal nanomesh thin films prepared by bimodal self-assembly of block copolymer (BCP)/homopolymer blends may offer a new opportunity for TCE. This hierarchical concurrent self-assembly consists of macrophase separation between BCP and homopolymer as well as microphase separation of BCP, and thus provides a straightforward spontaneous production of a highly porous multiscale pattern over an arbitrary large area. Employing a conventional pattern transfer process, we successfully demonstrated a multiscale highly porous metallic thin film with reasonable optical transparency, electro-conductance, and large-area uniformity, taking advantage of low loss light penetration through microscale pores and significant suppression of light reflection at the nanoporous structures. This well-defined controllable bimodal self-assembly can offer valuable opportunities for many different applications, including optoelectronics, energy harvesting, and membranes.

Synergistic multi-doping effects on the Li7La3Zr2O12 solid electrolyte for fast lithium ion conduction.

Here, we investigate the doping effects on the lithium ion transport behavior in garnet Li7La3Zr2O12 (LLZO) from the combined experimental and theoretical approach. The concentration of Li ion vacancy generated by the inclusion of aliovalent dopants such as Al(3+) plays a key role in stabilizing the cubic LLZO. However, it is found that the site preference of Al in 24d position hinders the three dimensionally connected Li ion movement when heavily doped according to the structural refinement and the DFT calculations. In this report, we demonstrate that the multi-doping using additional Ta dopants into the Al-doped LLZO shifts the most energetically favorable sites of Al in the crystal structure from 24d to 96 h Li site, thereby providing more open space for Li ion transport. As a result of these synergistic effects, the multi-doped LLZO shows about three times higher ionic conductivity of 6.14 × 10(-4) S cm(-1) than that of the singly-doped LLZO with a much less efforts in stabilizing cubic phases in the synthetic condition.

Flexible binder-free metal fibril mat-supported silicon anode for high-performance lithium-ion batteries.

We report the fabrication of a flexible and binder-free metal fibril mat-supported Si anode (Si@SFM) by a simple process. The fabricated Si@SFM anode showed a high discharge capacity, ∼3000 mAh g(-1) at a current rate of 300 mA g(-1), and exhibited stable capacity retention, 90% at a 1 C rate (2000 mA g(-1)) after 200 cycles. The rate capability of the electrode was still high even when both the charge and the discharge current rates were markedly increased at the same time (1234 mAh g(-1) for charge-discharge time of ∼12 min). Moreover, owing to its mechanical flexibility, the Si@SFM can be adopted as a key component of flexible lithium-ion batteries (LIBs). After cell packaging, the rechargeable flexible battery under bending stress showed only a little capacity fading (86% of initial capacity) at 1000 mA g(-1) over 150 cycles. These results suggest that the Si@SFM electrode is readily suitable for use in rechargeable flexible LIBs.

Graphite/silicon hybrid electrodes using a 3D current collector for flexible batteries.

A flexible hybrid anode from graphite and thin film silicon is realized by the concept of a 3D sandwich current collector by the combination of micro-contact printing and RF magnetron sputtering. Flexible lithium-ion batteries with a new hybrid anode demonstrate not only enhanced specific capacity but also improved rate capability compared to that of a conventional graphite anode under bending deformation.

Study on improved electrochemical properties of graphene nanosheet/nickel oxide composite as electrode materials.

Graphene nanosheets (GNS)/nickel oxide (NiO) composites were synthesized by a chemical method with a various amount of nickel precursor. For all composites, NiO nanoparticles were well decorated on the surface of graphene nanoplatelets. The structure and morphology analysis was performed by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). We confirmed that pure NiO particles are aggregated with each other and NiO particles dispersed on GNS prevent graphene from restacking in the composite. Electrochemical properties were also examined by cyclic voltammetry (CV). The optimum ratio of GNS to NiO was 1:20 (2 g of NiCl2 x 6H2O), showing the highest specific capacitance of 1034.7 Fg(-1) at 2 mV s(-1). This value was much higher than that of pure NiO and GNS, respectively. However, as the amount of nickel precursor increased, the specific capacitance displayed a decreasing tendency. It was probably due to the large agglomeration of NiO particles in high content of NiCI2 x 6H2O.

Imprintable, bendable, and shape-conformable polymer electrolytes for versatile-shaped lithium-ion batteries.

A class of imprintable, bendable, and shape-conformable polymer electrolyte with excellent electrochemical performance in a lithium battery system is reported. The material consists of a UV-cured polymer matrix, high-boiling point liquid electrolyte, and Al2 O3 nanoparticles, formulated for use in lithium-ion batteries with 3D-structured electrodes or flexible characteristics. The unique structural design and well-tuned rheological characteristics of the UV-curable electrolyte mixture, in combination with direct UV-assisted nanoimprint lithography, allow the successful fabrication of polymer electrolytes in geometries not accessible with conventional materials.

Precursor solvent influence on preparation and electrochemical properties of platinum nanoparticles electrodes.

The crystalline sizes and loading efficiencies of metallic nanoparticles for fuel cell catalysts have been measured by changing solvent species containing precursors. By changing the solvent species containing carbon particles and metal salt, the microstructure and the according electrochemical property of catalysts could be controlled. Four kinds of solvent were investigated in this study. Pt catalysts that were deposited on carbon blacks supports by using an ethylene glycol solution showed the highest deposition efficiency, 85% and smallest crystalline size, 2.85 nm of particles. From the experimental result, it was concluded that the electrochemical performance of catalysts was dependent on the crystalline size and deposition efficiency of metal particles, by changing solvent species.

Simple approach for enhancement of light harvesting efficiency of dye-sensitized solar cells by polymeric mirror.

A Polymeric mirror from 1D photonic crystal exhibiting full specular reflection is applied on the exterior of the counter electrode of a dye-sensitized solar cells (DSSCs). Reflection of exiting light from the cell allows for the reuse of the light and thereby significantly increases the efficiency of the DSSCs (from 8.07% to 8.85%). Furthermore, it is also found to be effective even with incorporation of an internal scattering layer, which is widely used within a TiO2 anode layer for enhancing light trapping in DSSCs (from 9.17% to 9.53%).

Polyaniline doped with dimethyl sulfate as a nucleophilic dopant and its electrochemical properties as an electrode in a lithium secondary battery and a redox supercapacitor.

The physical properties of polyaniline (PAn) powder, doped by nucleophilic doping of dimethyl sulfate (DMS), were characterized, as well as its electrochemical behaviors, to investigate the possibility of a power source device adopting the PAn-DMS electrodes. It is shown that the nucleophilic addition of DMS into PAn concurrently resulted in an increase of the charge transport properties (e.g., electrical conductivity) and enhanced the processability (e.g., lowering of the melting point). The surface structure of PAn-DMS electrodes showed that the compactness of the electrode surface was helpful in increasing the capacity of lithium rechargeable batteries, whereas the porous behavior was valuable to improve the capacitance of a redox supercapacitor. Depending on the power source devices using the lump- and sheet-type PAn-DMS electrodes, the following optimized performances were obtained: more than 80 mA h g-1 after 50 cycles for lithium secondary battery use and approximately 115 F g-1 initially and approximately 94 F g-1 after 5000 cycles at a current density of 2.5 mA cm-2 for application as a redox supercapacitor, which were the highest reported performances for all PAn-based electrodes.