PC Solution Research Articles

Impact of Sc Doping in Layered Nameo2 Oxides on Their Electrode Performance

In recent years, Na-ion batteries (SIBs) are expected to be an alternative to Li-ion batteries for certain applications[1]. A possible candidate of the cathode materials for SIBs is transition metal layered oxides Na x MeO2 (Me = metal element(s)). Among them, O3-type Na[Ni1/2Mn1/2]O2 is considered promising due to its high energy density[2]. In order to improve cycle performance, controlling the morphology and surface modification are known to be effective for improving cycle performance. Our group has studied improvement of cycle performance through a technique known as heteroatomic substitution, thus we here focus on Sc3+ which has not been a lot of attention. While Sc3+ is redox-inactive within the layered oxide[3], partial substation with inactive Mg2+ and Ti4+ improves cycle stability[4]. In this study, we synthesized O3-Na[(Ni1/2Mn1/2)1-xScx]O2 and studied the effect of Sc3+ substitution on the electrochemical performance of O3-Na[Ni1/2Mn1/2]O2 and compared with the case of the doping in other O3 and P2-type Mn based oxides. O3-Na[(Ni1/2Mn1/2)1-xScx]O2 (x = 0, 0.08, 0.11) samples were synthesized using Na2CO3, Ni(OH)2, Mn2O3 and Sc2O3 as starting materials, based on the synthesis method of the non-doped O3-Na[Ni1/2Mn1/2]O2 as we previously reported[2]. To assess the electrochemical properties of P’2-Na2/3[Mn1-x Me x ]O2 samples, we employed a working electrode consisted of active materials, acetylene black, and PVdF in 80:10:10 wt.% on Al foil. Na metal served as a counter electrode, with a 1.0 mol dm-3 NaPF6 PC solution as an electrolyte. XRD patterns of O3-Na[(Ni1/2Mn1/2)1-xScx]O2 are shown in Fig. 1 (a). Major diffraction peak can be indexed as rhombohedral Na[Ni1/2Mn1/2]O2 with space group of R-3m, confirming O3-type layered oxide. It also confirms that Sc3+ occupied the transition metal layer (Ni, Mn site) through the Rietveld refinements. At x = 0.11, other O3 phase with a different lattice parameter was identified as an impurity, indicating that Sc is substituted for Ni/Mn up to about 8% in O3-Na[Ni1/2Mn1/2]O2 despite being able to directly crystalize O3-NaScO2 via solid state reactions. Sc3+ (0.745 Å) which has a large ionic radius than Ni2+ (0.690 Å) and Mn4+ (0.645 Å), resulted in the enlarged lattice constant a (Fig. 1 (a), inset). Fig. 1 (b) shows the cycle performance with initial charge/discharge curves of O3-Na[(Ni1/2Mn1/2)1-xScx]O2 electrode in Na cell. In the charge/discharge curve, in non-substituted x = 0 (NNMO), a stepwise curve was observed, whereas in Sc-substituted x = 0.08 (NNMSO8), curve shape changed smoothly. The capacity retention after 50 cycles was remarkably improved from 41.0% to 70.7% by the Sc doping. From analyses of the structural change during cycling, we found that the disappearance of Na/vacancy ordering and the reduction in volume change have led to enhance cycle stability of NNMO by Sc3+ doping. Based on the results obtained so far, we attempted to compare the effects of further Sc3+ substitution into other materials, P’2/P2-Na2/3MnO2 [5]. From considering the characteristics of each non-doped materials, we verified how Sc3+ substitution affects the cycle performance for each layered oxide. We will further discuss the electrochemical performance when coating with scandium oxide like NaxScO2 is applied to the O3-Na[Ni1/2Mn1/2]O2, in order to understand the impact of Sc3+ on electrochemical properties of layered oxide.

P'2-Na2/3[Mn1-X Sc x ]O2 Electrode in Sodium-Batteries

In recent years, Na-ion batteries (SIB) are expected to be an alternative to Li-ion batteries. One of the cathode materials for SIB is transition metal layered oxides Na x TMO2 (TM = transition metal). In order to improve their capacity, efforts have been made to utilize the redox process(es) of not only TM ions but also oxide ions (oxygen redox). In addition, partial replacement of TMs with electrochemically inactive elements has been investigated to enhance cycle stability. Our group reported P2-type Na x MnMeO2 (Me = Li, Mg) exhibit higher capacity than existing materials via using additional redox of oxide ions (1, 2). Another example delivering high capacity reported in our group is P’2-type Na2/3MnO2, where the average oxidation states of Mn is about +3.37 and a co-operative Jahn-Teller distortion (CJTD) of Mn3+ (t2g 3-eg 1) is shown (3). In this study, we synthesized P’2-Na2/3Mn1-x Sc x O2 and studied the effect of Sc substitution on the electrochemical properties of P’2-Na2/3MnO2. P’2-Na2/3Mn1-x Sc x O2 (x = 0, 0.08, 0.11) samples were synthesized using Na2CO3, Mn2O3, and Sc2O3 as starting materials, based on the synthesis method of the non-doped P’2-Na2/3MnO2 as we previously reported (3). For galvanostatic cycling tests, a working electrode consisted of active materials, acetylene black, and PVdF in 80:10:10 wt.% on Al foil. Na metal was used as a counter electrode, and an electrolyte used was 1.0 mol dm-3 NaPF6 PC solution. XRD patterns of P’2-Na2/3Mn1-x Sc x O2 are shown in Fig. 1 (a). Major diffraction peaks can be indexed as orthorhombic Na2/3MnO2 with space group of Cmcm, confirming P’2-type layered oxides. Note that non-substituted Na2/3MnO2 shows a superstructure peak at 23.9º in 2θ attributed to in-plane superstructure (3). At x = 0.11, impurity of Sc2O3 is observed, indicating that Sc is substituted for Mn up to about 8% in P’2-Na2/3MnO2. Sc3+ ions which has a large ionic radius than Mn3+ ions and no Jahn-Teller distortion, resulted in the enlarged lattice constant a (Figure 1 (a), inset) and the reduced lattice distortion (4). Fig. 1 (b) shows the discharge capacity and the coulombic efficiency of P’2-Na2/3Mn1-x Sc x O2 Electrode in Na cell. The capacity retention after 50 cycles for the non-substituted x = 0 (non-sub) and Sc-substituted x = 0.08 (Sc-sub) in the voltage range of 1.5 – 4.4 V was 66.4% and 85.4%, respectively. In-situ XRD data can support better cycling life. The Sc-sub exhibited better rate characteristics than the non-sub, indicating that there is an optimal amount of Sc to improve the electrochemical properties. Looking at the initial charge/discharge curves at different cutoff voltages (Fig. 1 (c)), setting the upper cutoff voltage beyond 3.47 V, causes a significant polarization due to the phase transition from P’2 to OP4. From the cycle stability tests at different upper cutoff voltages (Fig. 1 (d)), the upper cutoff limit of 4.0 V demonstrates notable capacity fade than that of 4.4 V. One possible reasons should be changing the surface chemistry of electrode by applying higher voltage than 4.0 V. We will further discuss the effects of Sc substitution and charge/discharge voltage range on the electrochemical properties.References Yabuuchi, S. Komaba, et al., J. Mater. Chem., 2, 16851 (2014).Yabuuchi, S. Komaba, et al., Adv Energy Mater., 4, 1301453 (2014).Kumakura, S. Komaba, et al., Angew. Chem. Int. Ed., 55, 12760 (2016).S. Kumakura, S. Komaba, et al., Chem Mater., 29, 8958 (2017). Figure 1

A polysaccharide/chitin hydrogel wound dressing from a Periplanattica americana residue: coagulation, antioxidant activity, and wound healing properties

Pharmaceuticals derived from the raw materials of Periplanattica americana have been applied for wound healing, liver disease treatment, and antitumor therapy. However, the resulting residues of P. americana have not been well exploited. We found that P. americana residues comprised high amounts of chitin (PC) and polysaccharides (PAP) exhibit good biological activity. Compared to shrimp-derived chitin, PC has a smaller molecular weight (Mv), lower crystallinity, and looser molecular structure, demonstrating stronger antioxidant activity and degradability. After adding the PAP, the PC solution rapidly lost fluidity and formed a hydrogel (P/PCGEL) that had antioxidation, biodegradability, and injectability properties and exhibited rapid coagulation, good water absorption and retention, and a low hemolysis rate (HR). In vivo studies reported that the P/PCGEL reduced edema during burns, accelerated collagen synthesis and deposition, reduced reactive oxygen species (ROS) levels, and increased superoxide dismutase (SOD) levels, thereby reducing the inflammatory response, avoiding oxidative stress, and effectively promoting wound healing. Furthermore, the P/PCGEL demonstrated good biocompatibility, rapid biodegradation, and injectability, thereby reducing the risk of trauma and infection engendered by repeated wound opening and dressing changes. These properties also demonstrated the potential application for this hydrogel in preparing injectable hydrogel excipients. Hence, this study provided a hydrogel-formed wound dressing comprising pure natural ingredients and offering convenient administration, economic availability, and strong tissue repair ability.

Thermal risk evaluation of concentrated electrolytes for Li-ion batteries

Concentrated electrolytes have been attracting increasing attention due to their unique properties. However, despite the concern about their thermal stability, few research has been done on their exothermic behaviors, especially with the coexistence of electrodes. Herein, we report the results of detailed investigation into the thermal properties of LiBF 4 , LiPF 6 , LiTFSI, and LiFSI/carbonate concentrated solutions and their thermal behaviors with the coexistence of fully lithiated graphite. Concentrated LiBF 4 solutions showed no practical application possibilities because they were unstable on C 6 Li. Increasing the salt concentration decreased the thermal stability of LiPF 6 /PC solutions with the coexistence of C 6 Li. The organic salt dominated the thermal behavior of the solution when mixed with C 6 Li. A drastic exothermic reaction happened at 210–220 °C when C 6 Li was mixed with LiFSI solutions, indicating a very high thermal risk of LiFSI carbonate solutions as LIB electrolytes. In contrast, LiTFSI solutions showed much milder reactions with C 6 Li. On the other hand, because of the different LiF content in SEI, the exothermic onset temperature of the C 6 Li mixture with the concentrated solution increased in the order of LiFSI > LiTFSI > LiPF 6 . Comprehensively, concentrated LiTFSI electrolytes should be a good choice for LIB from the standpoint of battery safety. • TG-DSC analysis on Li salt-carbonate solutions with/without C 6 Li were performed. • Concentrated LiBF 4 and LiPF 6 electrolytes had poor temperature tolerance on C 6 Li. • LiFSI solutions could protect C 6 Li until 150 °C and then drastically reacted. • LiTFSI/DMC solutions showed excellent thermal stability up to 400 °C. • Highly concentrated LiTFSI electrolytes should be a good choice for safer LIB.

Anticancer activities of a metal-free phthalocyanine on MCF-7 and MDA-MB-231 cells and singlet oxygen production as a photosensitizer in PDT

Cancer, which is often described as an uncontrollable rapid proliferation of cells, is currently the leading cause of death in the world together with cardiac disease. Therefore, the main purpose of the current research work was to study the anticancer effects of a first-time-synthesized phthalocyanine (Pc) as photosensitizer in PDT against cancer and evaluate its effects on human cells in vitro. Quantum yields of singlet oxygen photogeneration were in air using the relative method with standard-ZnPc as reference and DPBF as chemical quencher for singlet oxygen. The concentration of DPBF was prepared almost 3 x 10-5 molar to avoid chain reactions induced by DPBF in the presence of singlet oxygen. Solutions of Pc as sensitizer (absorbance = 2.0 at the irradiation wavelength) containing DPBF were prepared in the dark and irradiated in the Q band region using the setup described. DPBF degradation at 417 nm was monitored with UV-Vis spectrophotometry. For in vitro studies, nine different MFPc-1 concentrations (0.2 µM- 0.4 µM- 0.8 µM- 1.6 µM- 3.2 µM- 6.4 µM- 12.8 µM- 25.6 µM- 51.2 µM) applied to MCF-7 and MDA-MB-231 breast cancer cell lines for 24 hours and MTT assay was carried out. After determination of optimum concentration, mitotic index, and apoptotic index values of cell lines were determined with administration of these concentrations. Singlet oxygen quantum yield (Φ), which is a measure of the efficiency, of MFPc-1 was found 0.50, although MFPc-1 is being metal-free phthalocyanine. For in vitro studies after the application of different concentrations to MCF-7 and MDA-MB-231 for 24 hours, the optimum concentration was determined as 12 µM for both cell lines by the MTT assay. After application of the determined optimum concentration for 24, 48 and 72 hours, there was a significant decrease in the mitotic index values and significant increase in the apoptotic index values of both MCF-7 and MDA-MB-231 breast cancer cell lines.

Lightweight Blockchain Processing. Case Study: Scanned Document Tracking on Tezos Blockchain

To bridge the current gap between the Blockchain expectancies and their intensive computation constraints, the present paper advances a lightweight processing solution, based on a load-balancing architecture, compatible with the lightweight/embedding processing paradigms. In this way, the execution of complex operations is securely delegated to an off-chain general-purpose computing machine while the intimate Blockchain operations are kept on-chain. The illustrations correspond to an on-chain Tezos configuration and to a multiprocessor ARM embedded platform (integrated into a Raspberry Pi). The performances are assessed in terms of security, execution time, and CPU consumption when achieving a visual document fingerprint task. It is thus demonstrated that the advanced solution makes it possible for a computing intensive application to be deployed under severely constrained computation and memory resources, as set by a Raspberry Pi 3. The experimental results show that up to nine Tezos nodes can be deployed on a single Raspberry Pi 3 and that the limitation is not derived from the memory but from the computation resources. The execution time with a limited number of fingerprints is 40% higher than using a classical PC solution (value computed with 95% relative error lower than 5%).

Soybean-derived phospholipids complexed poly (lactic-co-glycolic acid) nanofibrous scaffolds for tissue engineering applications

Polymeric scaffolds play a vital role in tissue engineering. Electrospun poly (lactic-co-glycolic acid) (PLGA) membranes can be a promising scaffold. However, their applications are restricted due to poor hydrophilicity and single function. In this study, we show for the first time how blending of L-α-phosphatidylcholine (PC) to PLGA to yield hybrid scaffolds alters the physical properties and wettability and consequently affects the biodegradability and biocompatibility. Soybean-derived phospholipids complexed PLGA nanofibrous scaffolds (PLGA-PC) were readily fabricated by electrospinning polymer solutions of PLGA and PC in different ratios. The obtained scaffolds exhibited a dramatic decrease in fibre diameter and a significant increase in porosity and hydrophilicity as the PC component was added. Although the mechanical strength of PLGA scaffolds decreased due to the incorporation of PC, the PLGA-PC groups showed tensile strength above 2.5 MPa in both dry and wet states. Based on in vitro degradation, we found that it was accelerating for PLGA-PC scaffolds with PC content increased. Additionally, these scaffolds presented superior blood compatibility and cytocompatibility. The explored research on phospholipids complexed scaffolds can readily extend to other polymers and provides a feasible strategy to construct optimal microenvironments for seeded cells, indicating promising use in various tissue engineering.

Diffusion of ions and solvent in propylene carbonate solutions for lithium-ion battery applications

Diffusion of lithium ions in organic solvent solutions is important to the performance of lithium ion batteries. In this article, fully atomistic molecular dynamics (MD) simulations were employed to study the diffusive behavior of LiPF6 electrolyte salt and propylene carbonate in solutions at different temperatures in direct comparison to experimental diffusivity data. Organic solutions at 1 M concentrations were considered at the operational conditions of Lithium ion batteries. We show that non-polarizable scaled charge force fields can predict, quantitatively, the diffusion of Li+ and PC solvent in a range of operational temperatures. Such type of force fields are much less computational demanding than polarizable or ReaxFF models. Diffusion follows an Arrhenius type of behavior. van Hove autocorrelation functions show a nonGaussian type of movement for ions and PC solvent. The Li+ is moving by a mixed-vehicular mechanism. Moreover, the nearest neighbour distances of the Li+- carbonyl oxygen in these PC solutions is predicted accurately using the scaled charges GAFF, in agreement to experiments. Furthermore, quantitative prediction of modeled ionic conductivity in comparison to experiments can be achieved in a range of temperatures.

Large ultrafast nonlinear optical response and excellent optical limiting behaviour in pyrene-conjugated zinc(II) phthalocyanines at a near-infrared wavelength

The design and synthesis with full structural utilization of a new type of nonlinear photonic material, Zinc(II) phthalocyanine macrocycle (Pc-pyrene), bearing binary oriented (up/down) pyrene units is reported. The novel pyrene-based macrocycle has been successfully obtained in high yield upon coupling multiple azido pyrene derivatives on a previously fabri-cated alkynyl-substituted macrocyclic platform (Pc1) via multiple tandem Cu(I)-catalysed azide-alkyne cycloaddition (CuAAC) reactions. The ultrafast nonlinear optical characteristics of both Pc1 and Pc-pyrene have been investigated in solution using a near-infrared femtosecond pulsed laser. The femtosecond Z-scan results reveal a low optical limiting threshold and a good set of figures of merit that make these macrocycles feasible for optical limiting as well as switching applications. In a major breakthrough, ultrafast laser-induced deformations in Pc-pyrene-embedded PMMA films results in a very large enhancement of the three-photon absorption coefficient at 800 nm by up to ~105 times that of Pc solutions. Furthermore, the deformed Pc-pyrene PMMA films having the advantage of flexibility and possess an excellent optical limiting threshold (0.0018 J/cm2), much lower than various previously reported values, which enables them to be one of the best optical limiters.

HISTSFC: Optimization for ND Massive Spatial Points Querying

Space Filling Curve (SFC) mapping-based clustering and indexing works effectively for point clouds management and querying. It maps both points and queries into a one-dimensional SFC space so that B+- tree could be utilized. Based on the basic structure, this paper develops a generic HistSFC approach which utilizes a histogram tree recording point distribution for efficient querying. The goal is to resolve the issue of skewed data querying. Besides, the paper proposes an agile method to compute a continuous Level of Detail (cLoD), and integrates it into HistSFC to support smooth rendering of massive points. Results indicate that for range queries, HistSFC decreases the False Positive Rate (FPR) of selection by maximally 80%, compared to previous approaches. It also performs significantly faster than the state-of- the-art Oracle SDO_PC solution. With improved performance on visualization and k Nearest Neighbour (kNN) search, HistSFC can therefore be used as a new standard solution.

Two Open Solutions for Industrial Robot Control: The Case of PUMA 560

In this paper we present two different, software and reconfigurable hardware, open architecture approaches to the PUMA 560 robot controller implementation, fully document them and provide the full design specification, software code and hardware description. Such solutions are necessary in today’s robotics and industry: deprecated old control units render robotic installations useless and allow no upgrades, advancements, or innovation in an inherently innovative ecosystem. For the sake of simplicity, just the first robot axis is considered. The first approach described is a PC solution with data acquisition I/O board (Humusoft MF634). This board is supported with Matlab Real-Time Windows Toolbox for real-time applications and thus whole controller was designed in Matlab environment. The second approach is a robot controller developed on field programmable gate arrays (FPGA) board. The complexity of FPGA design can be overcome by using a third party software package, such as self-developed Matlab FPGA Real Time Toolbox. In both cases, parameters of motion controller are calculated by using simulation of the PUMA 560 robot first axis motion. Simulations were conducted in Matlab/Simulink using Robotics Toolbox.

Role of polyethylene oxide content in polypyrrole linear actuators

Current research on conducting polymer composite actuators has been mainly focused on achieving increased linear actuation with improved electrical, physical and chemical properties. Polyethylene oxide (PEO) has been shown to enhance both mechanical and electrical properties of conducting polymers at certain concentrations. However, as some of these effects peak off, the optimal concentration is difficult to determine. In this study, polypyrrole (PPy)-PEO composite films, doped with dodecylbenzene sulfonate, were electropolymerized from solutions with different concentrations of PEO. The obtained films were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman, FTIR and energy dispersive X-ray spectroscopy (EDX). Electrochemical impedance spectroscopy (EIS) and modified scanning ionic conductance microscopy (mSICM) allowed the determination of electronic and ionic conductivities of the samples. Their electro-chemo-mechanical deformations (ECMD) were investigated under cyclic voltammetry. In aqueous electrolyte, the samples showed expansion/contraction during reduction/oxidation, respectively (cation-driven), while opposite behaviour - expansion/contraction during oxidation/reduction (anion-driven) behaviour was observed in propylene carbonate solutions. These films obtained from solutions with a PEO content of 5% showed the highest deformations (strain and stress). They also presented the highest ionic and electronic conductivities and redox charge density. The ECMD deformation per unit of redox charge was much higher in PC solutions than in aqueous solutions: more PC molecules are exchanged for osmotic balance per unit of redox charge.

Homogeneous Liquid-Liquid Extraction of Metal Ion Utilizing Upper Critical Solution Temperature of Propylene Carbonate

ABSTRACTThis study was undertaken to investigate the extraction of In3+ and Ga3+ by 7-(4-ethyl-1-methyloctyl)-8-hydroxy-quinoline (Kelex100), which has been found to be a slow extraction process. Homogeneous liquid-liquid extraction utilizing upper critical solution temperature of 4-methyl-1,3-dioxolan-2-one (propylene carbonate, abbreviated as PC) was used to eliminate the interface and speed up the extraction, since distribution between two phases was thought to be the rate-determining step. The effect of contact time on the percentage of metal extraction was examined at 80ºC using Kelex100 dissolved in toluene and PC solutions and the difference between two solvents was evaluated. The results clearly show that the use of homogeneous liquid-liquid extraction using PC with Kelex100 is faster than traditional two phase extraction.

WO3 all-solid-state electrochromic devices made of capillary phenomena

An all-solid-state electrochromic device with a mixture of UV curable resin and liquid electrolytes as new electrolyte, tungsten trioxide as an electrochromic material, and LiClO4 as an electron donor was reported. PMMA was simply mixed with a PC solution to improve the electrolyte stability. Capillarity was used to make the device, and ultraviolet light was used to complete the packaging. The device is made of capillary phenomena and encapsulated by ultraviolet light. The composition, morphology, and transmittance of the films and the response time of the device were measured. A new type of electrolyte was prepared that greatly reduces the encapsulation time and solves the leakage problem by encapsulation. The final device has excellent optical memory, can complete the colouring fading cycle within 10 s, and has a transmittance between 10% and 90% at 800 nm and between 65% and 95% at 400 nm.

Li-Ion solvation in propylene carbonate electrolytes determined by molecular rotational measurements.

Lithium-ion batteries are an attractive power source for a wide variety of applications. Expanding the performance limit of current Li-ion batteries requires ion-solvent interaction, which governs the ion transport behavior of electrolytes, to be fully understood. We herein examine the coordination number of the Li+ ion in LiPF6-PC solutions using femtosecond vibrational spectroscopy. Surprisingly, we found that the coordination number of PC in the first solvation shell of Li+ decreases from 4 to 2 as the salt concentration increases. At dilute salt concentrations, the Li(PC)4+ complex with a tetrahedral geometry is dominant, while at high salt concentrations, the presence of anions in the first solvation shell modifies the solvation structure, leading only 2 PC molecules to coordinate to Li+ directly. The variety of the solvation structure provides a rational explanation for the ionic conductivity changing as the salt concentration increases.

Operand AFM Observation of Electrodeposited Lithium Metal

Lithium metal anode is attractive due to its very negative potential and high capacity density, and however, secondary batteries with lithium metal anode are not practically used. One of the biggest obstacle against the wide spread in the market is dendrite formation at the anode during charging.[1] Many researches have been carried out where the mechanism of the dendrite formation of lithium metal were investigated in order to suppress the dendrite formation. Particularly the nano-scale and/or initial behavior of dendrite formation is of importance to elucidate the mechanism. Recently, peakforce-tapping mode AFM (atomic force microscopy) has been commercialized, where the damage to the sample surface from the AFM tip is much smaller than the damage in other conventional mode of AFM.[2] In this study, peakforce-tapping mode AFM was utilized to investigate the initial behavior of lithium electrodeposition in nano-scale in operand. Lithium wire was cut in the electrolyte and was used as working electrode. Lithium wire was used as a counter electrode, and 0.1 M LiPF6/PC was used as electrolyte solution. Lithium was electrodeposited on working electrode with current density of 2.5 mA cm-2. The working electrode surface was observed by using peakforce-tapping mode AFM in operand. The height and adhesion mapping images were simultaneously obtained. Two types of protrusions were observed in the series of height mapping images. One type of protrusions increased in size during electrodeposition, while the other type of protrusions kept their size. A series of adhesion mapping images indicate that the former type of protrusions had less adhesive surface than the latter type of protrusions. Furthermore, once the electrodeposition was stopped, the adhesion force of former type of protrusions increases and became the similar adhesion force of latter type of protrusions.[3] In PC solutions, the lithium surface is considered to be coated by surface film. The results may indicate that the surface film on the growing deposits is different from that of static-state deposits. In the case where dendrites had been suppressed, the deposits had been widely and uniformly spread and there had been no contrast at the adhesion images. The AFM technique can be used to detect the dendrite formation even at the very initial state of electrodeposition.

Characterization of Polyacrylamide based Superabsorbent Polymers for potential use in PC Matrices with Supplementary Cementitious Materials

This paper compares three types of polyacrylamide based Superabsorbent Polymers (SAP) with different water absorption capacities for potential application in Portland cement composites. The analysed matrices contain Supplementary Cementitious Materials (SCM) such as ground granulated blast-furnace slag (GGBS), fly ash (FA type F), silica fume (SF) and lime (NHL 5). SAPs were characterized in terms of shape, size and molecular structure by the Laser Diffraction, SEM, and the Raman Spectroscopy techniques. Kinetics and capacity of SAPs absorption in different environments (deionised water, PC solution and various PC-SCMs solutions) were evaluated by the tea-bag method. pH of all solutions was determined after 24 hours. The effect of different SCMs on SAPs sorption behaviour has been presented. The experimental results show that SAPs do not affect pH of cementitious solutions. However, SCMs addition reduces SAPs' absorption capacity and increase their desorption features. This is related not only to the type of SCM, but also to the level of substitution.

Lithium Deposition and Dissolution in Highly Concentrated Electrolyte Solutions

Lithium metal has a high energy density (3860 mAh g-1, 2062 mAh cm-3), and is the most promising anode in advanced LIBs. It is also important as an anode in Li-S and Li-air batteries in the innovative batteries in the future. Dendrite formation is a serious problem in cycleability and safety for lithium metal anode. Lithium dendrites are formed by (1) inhomogeneous thickness of the SEI formed on lithium metal, (3) local current concentration to the edges of deposited lithium, (3) excess nucleation during deposition, etc. Concentrated electrolyte solutions have attracted attention as electrolytes for LIBs because they have many unique characteristics [1-4]. We have so far investigated concentrated electrolyte systems that are stable against 5 V-class spinal LiNi0.5Mn1.5O4 cathode [5-7]. It has been reported that the use of concentrated LiFSI/tetraglyme (G4) effectively suppress lithium dendrite formation [8]. Unfortunately ether compounds cannot be used for even 4 V-class positive electrodes such as LCO, NCA, and NMC. In this study, we investigated several concentrated systems using carbonate-based solutions to suppress the dendritic growth of lithium during electrochemical deposition. A thin layer of Au (ca. 30 nm) was deposited on Cu foil and used as a working electrode. Nearly saturated 7.8, 10, and 3.9 mol kg-1 solutions were prepared using PC, DMC, and EC+DEC (1:1 by volume) as solvents and LiFSI was used as an electrolyte. 1 M solutions (0.83, 0.93, and 0.86 mol kg-1, respectively) were also used for comparison. A coin-type three electrode cell was constructed using Li foil as a counter and a reference electrode. Lithium was deposited at a current density of 0.1 or 1.0 mA cm-2 for 10 h, and then dissolved at the same current density to a cut-off voltage of 1.0 V. Figure 1 shows SEM images of the electrode surfaces after the first lithium deposition. Dendrites were observed in each 1 M solution, but their formation was remarkably suppressed in each concentrated solution. These facts clearly show that the use of concentrated solution is effective for suppressing lithium dendrite formation. Figure 2 compares SEM images of the cross-sections of the electrodes after the 1st and 11th deposition in the concentrated solutions. The particle size of the deposited lithium was larger in 7.8 mol kg-1 PC and 10 mol kg-1 DMC solutions than in 3.9 mol kg-1 EC+DEC after the first deposition, and increased further after the 11th deposition. The high concentration seems to be effective for suppressing excess nucleation and enhancing the particle growth of lithium. In 3.9 mol kg-1 EC+DEC solution, the thickness of the lithium layer was thin after the first deposition, but increased significantly after the 11th deposition. Probably a large amount of decomposition products of the solvent was deposited in the gaps of lithium metal. Figure 3 shows coulombic efficiencies for lithium deposition/dissolution cycles in 1 M solutions and 7.8, 10 and 3.9 mol kg-1 solutions of LiFSI dissolved in PC, DMC, and EC+DEC (1:1). The coulombic efficiency was low in 1 M PC and DMC solutions, but increased significantly in 7.8 mol kg-1 PC and 10 mol kg-1 DMC solutions. It was high even in 1 M EC+DEC solution and slightly increased in the 3.9 mol kg-1 solution. The average coulombic efficiencies for the 10 cycles were 84.0%, 92.6% and 96.8% in 7.8 mol kg-1 PC, 10 mol kg-1 DMC and 3.9 mol kg-1 EC+DEC, respectively. The EC+DEC solution gave the highest coulombic efficiency, which is due to the formation of an effective SEI layer formed by the decomposition of EC. Unfortunately the solubility of LiFSI in EC+DEC is low (3.9 mol kg-1), which did not effectively suppress the excess nucleation as shown in Fig. 2. More concentrated EC-based solution will suppress the dendrite formation and give a high coulombic efficiency. This work was supported by NEDO, Japan.

High performance red phosphorus electrode in ionic liquid-based electrolyte for Na-ion batteries

Electrochemical performance of the red phosphorus electrode was examined in ionic-liquid electrolyte, 0.25 mol dm−3 sodium bisfluorosulfonylamide (NaFSA) dissolved N-methyl-N-propylpyridinium-bisfluorosulfonylamide (MPPFSA), at room temperature. We compared its electrochemical performance to conventional EC/PC/DEC, EC/DEC, and PC solutions containing 1 mol dm−3 NaPF6. The electrode in NaFSA/MPPFSA demonstrated a reversible capacity of 1480 mAh g−1 and excellent capacity retention of 93% over 80 cycles, which is much better than those in the conventional electrolytes. The difference in capacity retention for the electrolytes correlates to the different solid electrolyte interphase (SEI) layer formed on the phosphorus electrode. To understand the SEI formation in NaFSA/MPPFSA and its evolution during cycling, we investigate the surface layer of the red phosphorus electrodes with hard X-ray photoelectron spectroscopy (HAXPES) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). A detailed analysis of HAXPES spectra demonstrates that SEI layer consists of major inorganic and minor organic species, originating from decomposition of MPP+ and FSA−. Homogenous surface layer is formed during the first cycle in NaFSA/MPPFSA while in alkyl carbonate ester electrolytes, continuous growth of surface film up to the 20th cycle is observed. Possibility of red phosphorous electrode for battery applications with pure ionic liquid is discussed.

A Novel K-Ion Battery; Hexacyanoferrate(II)/Graphite Cell

Due to the extensive application of green energy technologies, the demand of large-scale energy storage systems is increasing. As far as now, the most successful and widely used battery system is Li-ion battery (LIB). When the energy storage system is enlarged, however, the cost performance becomes a more dominant factor, which is not apparently the advantage of LIB. Therefore, many novel battery systems with low cost materials have been developed recently, such as Na-ion batteries and aqueous batteries. However, the working voltage of these batteries is limited because of the 0.3-V higher potential of Na+/Na than that of Li+/Li or limited electrochemical window of H2O. Consequently, energy density of these battery systems is not satisfied. On the other hand, potassium is an earth abundant element with a lower standard electrode potential than that of lithium in PC solution [1]. Hence, the cost benefit and high working voltage are expected at the same time in K-ion batteries. We have studied the KIB materials since 2013 and recently reported graphite negative electrode delivering 250 mAh/g with excellent reversibility and rate-capability based upon stage-1 KC8 formation by electrochemical potassium intercalation [1]. Obviously, another key to obtain the successful K-ion batteries is development of the promising positive electrode materials. Considering the larger ionic size of K+ ­, the insertion materials should provide the large diffusion tunnels. As a suitable positive electrode, Prussian blue analogues with open framework structure exhibit excellent electrochemical performance in Na-, K-ion aqueous and non-aqueous batteries in previous reports [2,3]. Herein, we propose non-aqueous K-ion batteries by developing hexacyanoferrate(II) compounds, K1.75Mn[FeII(CN)6]0.93·0.16H2O and K1.64Fe[FeII(CN)6]0.89·0.15H2O (denoted as K-Mn[Fe(CN)6] and K-Fe[Fe(CN)6], respectively) as affordable positive electrode materials. Furthermore, we demonstrate 4-volt class K-ion full cells with K1.75Mn[FeII(CN)6]0.93·0.16H2O and graphite electrodes for the first time to prove their feasibility as a high energy density battery system. K-rich Prussian blues studied here were synthesized by precipitation method. Electrochemical measurements were carried out using 2032 coin cell with 0.7 M KPF6 in EC: DEC (1:1) solution as electrolyte and potassium metal as negative electrode. Prussian blue electrode consisted of 70 % active material, 20 % Ketjen black and 10 % PTFE binder. As shown in Figure 1a, K-Fe[Fe(CN)6] exhibits two voltage plateaux during charge at 3.5 and 4.1 V and corresponding discharge plateaux at 3.4 and 3.9 V, while K-Mn[Fe(CN)6] exhibits higher discharge plateaux at 4.0 and 3.9 V. Thanks to the higher working voltage and reversible capacity, K-Mn[Fe(CN)6] electrode shows higher energy density (vs. Na as negative electrode) than K-Fe[Fe(CN)6], which is 520 Wh kg-1. Such high energy density is comparable to that of commercial LiCoO2 in Li cell. As potassium metal is violently reactive with water than lithium and sodium metals, a metallic K battery is highly dangerous and unrealistic for practical use. We demonstrated K-ion full cells performance, i.e. K+-shuttlecock cell consisting of graphite/K-Mn[Fe(CN)6] electrodes on Al current collectors, as shown in Figure 1b. The full cell delivers a reversible capacity of 110 mAh (g of K-Mn[Fe(CN)6])-1 with a mean operating voltage of 3.5 V. The K-ion battery also demonstrates reversible charge-discharge profiles and acceptable capacity retention/efficiency over 60 cycles. In this presentation, we will present new potassium insertion materials, binders, and electrolytes for advanced battery demonstration, of which the charge/discharge voltage is compatible with the voltage of conventional Li-ion battery.