Coin Type Research Articles

Solid Electrolytes for Thin Film Li-Ion Batteries with Novel Si and SiC Based Anodes

Recent advances in microelectromechanical systems technology have led to development of diverse small-scale devices that include microsensors, micromachines and devices for medical application. For these devices, there is an urgent need of new micro lithium-ion batteries (MLIBs) with high energy density and low cost. To avoid the leakage problems which could worsen both the operation and safety of microdevices powered powered by MLIB the use of solid electrolyte is highly desirable. In this work, ceramic solid state and polymer solid electrolytes were prepared and deposited on the surface of SiC thin film anode by various techniques: in situ polymerization, drop coating technique, electropolymerization, magnetron spattering etc. Despite the advantages of high capacity and low voltage of Si anode, its practical application restricted by severe volume expansion and mechanical degradation upon lithium alloying and de-alloying processes. In this term flexible thin polymer electrolyte could be a promising solution. A combination of nanoparticulate and thin film structure can provide significant mechanical stability to Si and mitigate its limitations. Physical properties of the obtained samples were characterized by Raman spectroscopy, X-ray diffraction, atomic force microscopy and scanning/transmission electron microscopy techniques. Further, assembling CR2032 coin type cell, the electrochemical properties of the cell with obtained samples were evaluated as a part of all solid-state thin film battery. Acknowledgements This research was funded by the target program №0115РК03029 "NU­ Berkeley strategic initiative in warm ­dense matter, advanced materials and energy sources for 2014­-2018" from the Ministry of Education and Science of the Republic of Kazakhstan.

Li/Ag2VO2PO4 Batteries: The Roles of Composite Electrode Constituents on Electrochemistry

Silver vanadium phosphorous oxide, Ag2VO2PO4, was used as a bimetallic cathode system to systematically study the impact of the constituents of a composite electrode, including polymeric and conductive additives, on the electrochemical polarization and the bimetallic discharge progression of the battery. Ag2VO2PO4 has been developed as a cathode material intended for use in batteries that power implantable cardiac defibrillators (ICDs). This application demands primary battery systems that are reliable over long periods of implantation and are able to deliver high current pulses to charge the capacitors of the device. With these requirements in mind, primary Li/ Ag2VO2PO4 batteries are particularly promising because of their high capacity (270 mAh/g), excellent rate capability with pulses >30 mA sq. 1/cm, and lower cathode dissolution compared to the commercially used Li/Ag2V4O11system. Ag2VO2PO4 is especially well suited for studies of discharge progression in bimetallic cathode systems. Notably, it can be discharged as a pure electroactive material in the absence of a conductive additive as it generates an in situ conductive matrix via a reduction displacement reaction resulting in the formation of Ag0 nanoparticles. The electrochemical reduction of Ag+ and V5+ in Ag2VO2PO4 has previously been determined to take place sequentially at low rates, with reduction of Ag+ to Ag0 through a reduction-displacement reaction occurring first but with a small level of V5+ reduction occurring concurrently. The Ag0nanoparticles formed can be detected by diffraction based techniques and can be spatially resolved by in situ Energy Dispersive X-ray Diffraction (EDXRD) to assess the homogeneity of discharge. EDXRD provides unique insight into the state of the electrode by enabling evaluation of discharged phases as a function of spatial location. Furthermore, the white beam energy of the synchrotron light source can penetrate the steel casing of the battery, providing in situ measurements of coin type cells without the need for specially designed X-ray windows. Three different electrode compositions were investigated: Ag2VO2PO4 only, Ag2VO2PO4 with binder, and Ag2VO2PO4 with binder and carbon. Constant current discharge, pulse testing and impedance spectroscopy measurements were used to characterize the electrochemical properties of the electrodes as a function of depth of discharge. In situ EDXRD was used to spatially resolve the discharge progression within the cathode by following the formation of Ag0. Ex situ X-ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure (EXAFS) modeling were used to quantify the amount of Ag0 formed. Results indicated that the metal center reduced (V5+ or Ag+) were highly dependent on composite composition (presence of PTFE, carbon), depth of discharge (Ag0 nanoparticle formation), and spatial location within the cathode.

Study of Capacity Retention of Mcmb Anode Using Various Nanostructured Conductive Additives

The global lithium-ion battery industry is growing at an impressive rate and is expected to grow even further in the near future. The main reasons for this are the high energy density and excellent cycling performance that these batteries exhibit. Researchers are experimenting with a handful of ideas that could make batteries vastly better than they are today, which could lead to more affordable electric cars and cheaper ways to store the intermittent energy1. The use of lithium-ion batteries (LIBs) in the automotive sector has been receiving quite significant attention. However, limitation of low electronic conductivity of electrodes has prohibited rapid commercialization of LIBs for automotive applications (such as EVs, HEVs, PHEVs, etc.) where high power density is required2. In addition, the lower electronic conductivity of active materials makes it difficult to achieve their theoretical capacities at implementation. A number of methods, such as surface coating with conductive material3, lattice doping4, addition of metallic particles (copper and nickel)5 were adopted to improve the conductivity of active materials with reasonable success. In this work, we examine the capacity retention characteristics of mesocarbon microbeads (MCMB) by the use of various nanostructure conductive additives such as carbon black (CB), multiwalled carbon nanotubes (MWCNTs) and graphene in a CR2016 type coin. Figure 1(a) shows the plot of electrical conductivity of MCMB anode with various proportion of CB and CNT. For the purpose of meaningful comparison, the weight percent of conducting agent in MCMB with CB, MCMB with CB and CNT, and MCMB with CNT composite anode remains the same. When some content of CB is replaced by CNT, electrical conductivity improves because of formation of hybrid conductive that meets both the long-range and short-range conduction requirement. In Figure 1(b) the experimental cycling behaviour for discharge capacity of MCMB-4 wt.% CB and MCMB-(3 wt.% CB+1 wt.% CNT) anode at 1C and 4C rate for first 50 cycles are compared and the effect of composite anodes with hybrid conductive network at 1C rate show 348 mAhg-1 capacity for initial cycle whereas electrodes with CB as additive exhibit about 337 mAhg-1. The MCMB-(CB+CNT) anode exhibits almost 99% capacity retention while MCMB-CB display the capacity retention of 92.6% after 50 cycles at 1C rate. Similarly, at 4C rate the initial capacity and capacity retention for mix conductive additives are superior as shown in Figure 1(b). The improvement of capacity retention performance is mainly because of improved electrical conductivity on addition of CNT due to their higher conductivity and high aspect ratio in comparison to CB. The cycling performance of MCMB anode with graphene as conductive additive will also be presented. Electrochemical impedance spectroscopy (EIS) will be employed to analyze the aging effects and rate of capacity degradation of cells by quantifying the growth of internal resistances with cycling. The morphological and structural changes of electrodes due to cycling will be examined by characterization at fresh and cycled stages. Reference [1] H. Y. Tran, G. Greco, C. Täubert, M. W. Mehrens, W. Haselrieder, A. Kwade, “Influence of electrode preparation on the electrochemical performance of LiNi0.8Co0.15Al0.05O2 composite electrodes for lithium-ion batteries” J. Power Sources 210 (2012) 276. [2] S. E. Cheon, C. W. Kwon, D. B. Kim, S. J. Hong, H. T. Kim, S. W. Kim, “Effect of binary conductive agents in LiCoO2 cathode on performances of lithium ion polymer battery” Electrochim. Acta 46 (2000) 599. [3] H. Momose, H. Honbo, S. Takeuchi, K. Nishimura, T. Horiba, Y. Muranaka, Y. Kozono, H. Miyadera, “X-ray photoelectron spectroscopy analyses of lithium intercalation and alloying reactions on graphite electrodes” J. Power Sources 68 (1997) 208. [4] Y. P. Wu, E. Rahm, R. Holze, “Effects of heteroatoms on electrochemical performance of electrode materials for lithium ion batteries” Electrochim. Acta 47 (2002) 3491. [5] F. Joho, B. Rykart, R. Imhof, P. Novak, M. E. Spahr, A. Monnier, “Key factors for the cycling stability of graphite intercalation electrodes for lithium-ion batteries”. J. Power Sources 81 (1999) 243. Figure 1

Dimensional stability and electrochemical behaviour of ZrO2 incorporated electrospun PVdF-HFP based nanocomposite polymer membrane electrolyte for Li-ion capacitors

Different weight percentages of ZrO2 (0, 3, 5, 7 and 10 wt%) incorporated electrospun PVDF-HFP nanocomposite polymer membranes (esCPMs) were prepared by electrospinning technique. They were activated by soaking in 1 M LiPF6 containing 1:1 volume ratio of EC : DMC (ethylene carbonate:dimethyl carbonate) to get electrospun nanocomposite polymer membrane electrolytes (esCPMEs). The influence of ZrO2 on the physical, mechanical and electrochemical properties of esCPM was studied in detail. Finally, coin type Li-ion capacitor cell was assembled using LiCo0.2Mn1.8O4 as the cathode, Activated carbon as the anode and the esCPME containing 7 wt% of ZrO2 as the separator, which delivered a discharge capacitance of 182.5 Fg−1 at the current density of 1Ag−1 and retained 92% of its initial discharge capacitance even after 2,000 cycles. It revealed that the electrospun PVdF-HFP/ZrO2 based nanocomposite membrane electrolyte could be used as a good candidate for high performance Li-ion capacitors.

Lityum iyon piller için kalay (II) oksit kompozit anot elektrotlarının üretimi ve karakterizasyonu

In this study, the core component of the composite, tin (II) oxide powders synthesized through a facile chemical reduction methods for Li-ion batteries. As the shell structure, surfaces of the as-synthesized tin (II) oxide particles were coated with carbon through microwave assisted carburization process. The surface morphologies and phase components of the as-synthesized tin (II) oxide/carbon composites were investigated via scanning electron microscopy and X-ray diffraction methods, respectively. CR2016 type coin cells were prepared by using tin (II) oxide/carbon composite powders and electrochemical tests were performed at room temperature via 8-channel MTI BST8‒MA electrochemical test station between 10 mV and 2.5 V potential range by applying fixed 1 C state of charge conditions. The results have shown that tin (II) oxide/carbon composite structure have significantly improved the specific capacities to 396 mAh g-1 after 100 cycles.

THE ICONOGRAPHIC CHOICES OF THE MINUCII AUGURINI: RE-READING RRC 242 AND 243

The coinage of the Minucii Augurini (RRC 242 and 243) has received extensive scholarly commentary (Crawford 1974, 273-6; Wiseman 1996; Evans 2011; Elkins 2015, 21-2), but a holistic comparative approach to the iconography of these two types leads to new conclusions regarding likely compositional prototypes in other media, the motivations behind the design choice, and the attributes and identification of the figures. All this helps explain compositional variations between the two coin types that previous scholars have found problematic. A wide range of comparative evidence is used including glass paste intaglios, Etruscan tomb decoration, relief depictions and archaeological finds of priestly implements, further coin imagery, and literary testimony, especially Plut. Mor . 89F.

TRAJAN'S COLUMN VERSUS NUMISMATIC PROGRAMME. PROTOTYPES IN THE TRAJANIC IMPERIAL IDEOLOGY

Using comparative analysis between scenes on Traja’s Column and certain coin types, the paper identifies that numismatic sources have served in many cases to design images on the Column. The powerful meaning of symbols on coins – with a long-established tradition – was well used by the sculptors of the Column as it had a strong impact on the audience.

THE HEIGHT OF DENIER TOURNOIS MINTING IN GREECE (1289–1313) ACCORDING TO NEW ARCHAEOMETRIC DATA

The years 1289–1313 witnessed particularly prolific minting activities at different southern and central Greek mints on behalf of different polities. The coin issues are of great economic and political relevance, and therefore of interest to modern historians. Our understanding of these is based on traditional sources, either numismatic (types and finds), or historical. This paper aims to investigate the possibilities of adding further details to the picture through archaeometry. Specifically, tournois pennies of the three main mints of the region (Clarentza, Thebes, Naupaktos) excavated at Ancient Corinth were analysed according to two different non-destructive methods, X-ray fluorescence spectrometry (XRF) and laser-induced breakdown spectroscopy (LIBS). The resulting relative silver percentages and the fingerprints of the trace elements have supported our attempts to put the different coin types in chronological order and to add detail to the context and intent for each one of these. A vivid picture of monetary production emerges. The different issuing authorities were usually intent on maintaining a decent standard while variously trying to put pressure on rivals or to harmonise their productions with their allies. All the analysed mints were commercial in character, though they were subject to the great political changes affecting Greece in this period, the ambitions of the Angevin dynasty, the various challenges which it faced in Athens, the Peloponnese and the western Mainland, and finally the destructive arrival of the Catalans. In times of need, specifically military, these same mints could therefore rely on further bullion which reached them through internal or external political channels.

Preparation of activated carbon from bamboo-cellulose fiber and its use for EDLC electrode material

Carbonization and post activation of bamboo-cellulose fiber was carried out. The carbonization was performed at 600°C, 800°C and 1000°C in argon atmosphere. Then, they were activated by heating solid mixture of carbonized bamboo and sodium hydroxide (NaOH) at 720°C in argon atmosphere. The largest specific surface area of the resulting activated carbon (carbonized at 600°C) was 2366m2/g with the micropore volume of 0.71cm3/g and mesopore volume of 0.06cm3/g. It was found that the carbonization temperature is very important to obtain nanoporous carbon with large specific surface area. The distributions of interlayer spacing were estimated from the power spectra of the TEM images of the carbonized samples. It showed the interlayer spacing of basic structural unit (BSU) decreased from 0.49nm (BC-0600) through 0.47nm (BC-0800) to 0.45nm (BC-1000). The activated carbon was used as the host material of the electrodes of coin type electric double-layer capacitor (EDLC) with organic electrolyte. The observed specific capacitance was 43F/g (23F/cm3) for the activated carbon (carbonized at 600°C), comparable to 44F/g (22F/cm3) of commercial activated carbon (MSP). The corresponding values for the activated carbons (carbonized at 800°C and 1000°C) were 40F/g (23F/cm3) and 17F/g (12F/cm3), respectively.

Inferring objects from a multitude of oscillations

Oscillations often provide us with information of the origin. For instance, electrical oscillations measured by electroencephalograms and electrocardiograms afford clues to cognitive disorders and cardiac dysfunction, respectively. In particular, vibrations in air-pressure or sounds present rich information about circumstances. Here, we consider the problem of inferring types of coins from the sounds of their collision, and search for mechanisms that make such an inference possible. By devising a Bayesian learning algorithm and using a deep neural network, we reveal that optimizing the inference naturally leads the machines to select frequencies at which individual coins exhibit specific peaks in their sound spectra, indicating that inferences can be efficiently made by detecting the resonance sounds inherent in different coins. Both learning machines achieve high performances in correctly inferring coins. The developed methods are general and may be applicable to not only other sound identification tasks, but also various oscillatory phenomena, such as correlating brain activity to behavior as in the brain–computer interfaces.

Trebizond or Northern Syria? A new coin type of the Counts of Edessa and the attribution of a group of 11th / 12th century copper coins

On considère ici une monnaie de bronze qui porte au droit la représentation grossière d’un personnage en cotte de mailles au droit et au revers une croix ornée, cantonnée de la la légende ΙΣ ΧΣ ΝΙΚΑ. C’est le second exemplaire connu de ce type, frappé sans aucun doute par les comtes d’Édesse. Cette monnaie n’est pas seulement un supplément au répertoire du comté croisé, elle éclaire aussi l’interprétation d’un groupe de pièces de bronze autrefois attribué par S. Bendall à Trébizonde. En effet, étant donné que notre pièce et ce groupe dit de Trébizonde portent la même ligature des lettres N et I au revers, l’attribution de ce dernier doit être mise en question.

コイン型リチウム一次電池用正極合材用造粒工法の検討

コイン型リチウム一次電池用正極合材用造粒工法の検討

On Chronology of Coins of Volodymyr Olgerdovych (1362-1394)

Analysis of the finds made it possible to determine seven types of the 14th century Kyiv coins. Type I are represented by imitations of coins struck by Jani Beg (1342–1357), khan of Golden Horde, in Gulistan. The striking of this type is dated to the 1360s and 1370s. The obverse of type II contains a Cyrillic inscription and the Prince’s sign. On the reverse, there is an imitation of Horde’s Muhammad Bulak coin of 773 (1371/1372). Coins of this type are dated to the 1370s. Type III includes coins with the Prince’s sign and a plaiting with a legend containing the name of the Prince around it. They can be dated by the 1380s or probably by the early 1390s. Type IV includes the coins with the Prince’s sign and «IS» and a legend with the Prince’s name around it. They can be dated by the period from the end of the 1370s to the beginning of the 1390s. The coins of type V with the Prince’s sign and a cross with four points and with a legend containing the Prince’s name around it, as well as coins of type VI and VII, namely, bracteates with Prince’s sign or cross, are dated to the 1390s.

Is There a Need for Repeat Radiologic Examination of Children with Esophageal Coin Foreign Body?

Objectives To determine factors associated with the passage of coins. To determine the need for repeat preoperative chest x-ray (CXR) for esophageal coin foreign body. Setting Academic tertiary care center. Design Case series with chart review. Subjects and Methods Patient information was retrieved from an Institutional Review Board-approved database. We identified 1359 children with esophageal coin foreign bodies from 2001 to 2013. Patients with both initial diagnostic and immediate preoperative CXR were included. Results A total of 406 patients met inclusion criteria. The average age was 47 months (range, 1.8-194 months). On preoperative CXR, the position changed in 29 patients (7%). Age, type of coin, and location of coin were all statistically significant factors affecting the passage of the coin ( P < .0001). Coins in the distal esophagus were 9.3 times more likely to pass than coins in the proximal esophagus. The longer the object was in the esophagus, the less likely it was to pass. Conclusions This study characterizes when esophageal coins may pass. Age, type of coin, location of coin at initial x-ray, and length of time are all important considerations to determine if the coin will pass. This information may be used to counsel families about the likelihood of coins to pass and whether repeat x-ray is necessary prior to surgical removal. Additionally, it may be more cost-effective to obtain repeat films in select patients and prevent those from going to the operating theater who are more likely to pass the coin spontaneously.

Electrochemical and Impedance Investigation of Ni-Rich LiNi1-x-YCoxAlyO2 Cathode Material for Lithium-Ion Batteries

Recently, the lihtium-ion batteries (LIBs) are applied from the power sources of portable electronic devices to large-scale energy storage devices such as electrical vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and energy storage system (ESS), based on the cost, safety, and energy density. LiNiO2 has been considered as a promising cathode material for large-scale LIBs due to its low cost and high specific capacity (275 mAh/g) [1]. However, it has several problems, such as difficult synthesis, low thermal stability in chaged state, and capacity fading upon long-term cycling. In order to overcome these problems, several partial substitutions (Co, Mn, Fe, Al, etc.) for nickel have been investigated [2-5]. Among those partial subtitutions, Co has been proven to be a promising cadidate for LIB due to the improved thermal stability of LiNiO2 in the delithiated state. In addition, it was reported that a small amount of Al3+ doping leads to retain Ni in 3+ state and as a result, the stabilization of layerd structure and electrochemical properties of LiNi1-xCoxO2 is improved [6]. In this work, LiNi1-x-yCoxAlyO2 (0.08≤x≤0.15, 0.15≤y≤0.05) powders were prepared by a co-precipitation method in aqueous solution to employ as a cathode material for Li-S batteries. Ni1-xCox(OH)2 precursor was firstly prepared by co-precipitation and then aqueous solution containing Al was added in Ni1-xCox(OH)2 precursor. The pH of Al solution was controlled in a range of 8-10. Final solution was filtered, washed and dried. LiNi1-x-yCoxAlyO2 cathode materials were obtained after calcining Ni1-x-yCoxAly(OH)2 with LiOH (Li/M=1~1.1) under air atmosphere at 700 oC for 20 h. For electrode fabrication, LiNi1-x-yCoxAlyO2 cathode materials, super-P carbon black, and polyvinylidene fluoride (PVdF, Mw: ~ 400,000, Sigma Aldrich) were ground with N-methyl-2-pyrrolidone (NMP, SAMCHUN PURE CHEMICAL) as a solvent. Lithium foil, polyethylene (PE, W-SCOPE, KOREA), and 1.15M LiPF6/EC-EMC (3:7) were used as a counter electrode, separator, and electrolyte, respectively. The morphology of LiNi1-x-yCoxAlyO2 cathode material was characterized using a field emission-scanning electron microscopy (FE-SEM, Carl Zeiss, LEO-1530) and focused ion beam milling (FIB, Carl Zeiss, 1540 EsB). The particle size of LiNi1-x-yCoxAlyO2 synthesized in this work ranged at 5~10 um. The electrical conductivity of the LiNi1-x-yCoxAlyO2 cathode materials were also analyzed by a powder resistivity measurement system (HAN TECH, HPRM-M2). Cycle performance tests were carried out using the 2030 coin type cell by CC/CV method in a potential range of 3.0~4.3 V at 0.1 C rate. Cyclic voltammetry (CV, WonATech, WBCS 3000) was conducted at a scanning rate of 0.1 mV s-1. In addition, electrochemical impedance spectroscopy (EIS, Metrohm Autolab B.V., PGSTAT302N) was performed with a frequency range of 0.5 mHz to 100 kHz at an amplitude of 10 mV. The prepared LiNi1-x-yCoxAlyO2 cathode materials exhibit an excellent performance with a high specific capacity of over 180 mAh g-1 at the first cycle and with a cycling retention higher than 80%.

Cycle Performance of Metal-Substituted LiCoPO4 of Coarse Particles

Introduction LiCoPO4 has been focused as a promising cathode material to realize lithium-ion batteries with high energy density due to the high specific capacity of 167 mA h g-1 and a high operating potential of Co2+/Co3+ redox at 4.8 V vs. Li/Li+. However, the high operating potential sometimes results in a large irreversible capacity from the oxidative decomposition of electrolyte solutions during charge process. The decomposition occurs on the surface of electrode, so that coarse particles of active materials with low surface areas reduces the irreversible capacity. Based on this discussion, we synthesized the size-controlled LiCoPO4 and LiCoPO4 partially substituted with Fe and Ni by hydrothermal method1) . The particle sizes can be controlled by hydrothermal duration. The effect of particle size on the irreversible capacity derived from the oxidative decomposition of electrolyte solutions was investigated. Experimental LiCoPO4 was prepared from Li3PO4, CoSO4･7H2O. LiCo0.9M0.1PO4 (M=Fe or Fe) were prepared by replacing 10% of CoSO4･7H2O with FeSO4･7H2O or NiSO4･5H2O. Li3PO4, CoSO4･7H2O, FeSO4･7H2O (NiSO4･5H2O) were mixed in a molar rate of 1 : 0.9 : 0.1. The prepared solution was heated for 48 hours at 200 ºC with stirring in an autoclave. The product was collected by centrifugation and freeze-drying. Then, the resulting sample was mixed with sucrose and heated at 700 ºC for 1 h under 97 % Ar + 3% H2 atmosphere to form a carbon layer on the particle surface. The crystal structure, morphology, composition, and surface area of each sample were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma emission spectrometer (ICP) and the BET method, respectively. The state of carbon on the LiCo0.9M0.1PO4 particle was investigated by Raman spectroscopy. The carbon-coated samples were mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 15% and 10% to make composite electrodes, The electrochemical properties were characterized with 2032 coin type cell in a potential range of 2.5 ~ 5.1 V at 30 ºC. Results and discussions Figure 1 shows XRD patterns of the products. All peaks were assigned to those of LiCoPO4 and no impurity was observed. In addition, the substitutions of Co in LiCoPO4 with Ni and Fe were confirmed from the peak shifts to higher and lower angles, respectively. Those substitutions were also confirmed by ICP analysis. The carbon-coating on the particle surface was confirmed by Raman spectroscopy for all samples after the heat treatment at 700 ºC with sucrose. The specific surface areas of samples were characterized by BET measurements to be 8.75 m2 g-1(LiCoPO4), 5.40 m2 g-1 (LiCo0.9Ni0.1PO4), 1.00 m2 g-1 (LiCo0.9Fe0.1PO4), respectively. The particle size was increased by the metal replacement. Figure 2 shows the cycleability of the cells for LiCoPO4, LiCo0.9Ni0.1PO4 and LiCo0.9Fe0.1PO4 cathodes. The initial discharge capacity of LiCo0.9Fe0.1PO4 / C represented the largest value of 148 mAh g-1. The irreversible capacity of LiCoPO4 in the initial cycle was about 196 mAh g-1. In contrast, LiCo0.9Ni0.1PO4 / C and LiCo0.9Fe0.1PO4 / C showed the smaller irreversible capacities of 112 mAh g-1 and 76 mAh g-1, respectively. This result suggests that the irreversible capacity of the metal substitution products in the initial cycle was less than that of no-metal substitution product. Figure 3 shows the SEM image of the LiCo0.9Fe0.1PO4 / C particle after the cycle test. No crack in the particle was observed. Thus, the deterioration of the discharge capacity may not be due to the deterioration of the particles. LiCo0.9M0.1PO4 particle size was increased by both longer hydrothermal treatment duration and metal-substitution. The BET surface area of particle was decreased to 1.00 m2 g-1 from 8.75 m2 g-1. The decomposition of the electrolytic solution during charge was reduced with decreasing of BET surface area corresponding to electrochemical surface area. The irreversible capacity in the initial cycle was decreased to 76 mAh g-1 from 196 mAh g-1. Furthermore, it has been reported that Fe-doping improves the Li conductivity and electronic conductivity of LiCoPO4 2). These improvements are also possible reasons. Reference 1) J. L. Allen, T. R. Jow, J. Wolfenstine, J Power sources, 196 (2011) 8656-8661. 2) Y. M. Kang, Energy Environ. Sci, 4 (2011) 4978-4983 Figure 1

Reduced Graphene Oxide Sheets Attached Tin Oxalate Dihydrate As a High Capacity Anode for Lithium Ion Rechargeable Batteries

Lithium ion batteries have been widely applied as power sources for electronic devices to electric vehicle because of their high energy density, and long cycle life. Commercial graphite is the most commonly used as the anode material for lithium ion batteries. However graphite has its low theoretical capacity (372 mAh g-1). Therefore, to satisfy the growing power requirements, we need to explore alternative materials to replace graphite anode. For these reason, the silicon-based materials, transition metal oxides have been intensively investigated to replace the commercial graphite due to their high capacities, 700 ~ 1000 mAh g-1. Metal oxalate MC2O4 (M : Mn, Fe, Co, Ni, Sn, Cu, Zn) are also interesting because of high capacity. In this study, we synthesize tin oxalate by hydrothermal reaction, of SnCl2ㆍ6H2O (0.001 M), NaC2O4 (0.005 M), distilled water (9 ml), and ethylene glycol (EG, 16 ml) were mixed in a beaker and the mixed solution was stirred at room temperature for 6 h to form transparent solution. This solution was filled in a Teflon-lined autoclave (100ml capacity). This autoclave was sealed and heated at 100 oC - 200 oC for 12 h. After then, the autoclave was cooled to room temperature. The reacted solution were filtered and washed several times with de-ionized water and then dried at 80 oC for 24 h in a convection oven. Also, various contents of rGO were attached by layer by layer method. The obtained powder was analyzed by X-Ray diffraction (XRD, Rigaku, D-max 2000) using CuKα radiation. The XRD data were obtained with 0.03 step size and a 1 s count time. The particle morphologies of the products were analyzed by scanning electron microscopy (SEM, Hitachi, S-4700) and transmission electron microscopy (TEM, Hitachi, H-800). Electrochemical properties were measured in 2032 coin type cell. Electrodes were fabricated from a mixture of the prepared SnC2O4ㆍ2H2O powders (80 wt%), ketjen black (5 wt%), super-P (5 wt%) and polyacrylic acid (10 wt%) in distilled water. The obtained slurry was then applied onto Copper foil and dried in a vacuum oven at 80 oC for 1 h. The electrode was further dried over night at 80 oC under vacuum. The used electrode solution was 1M LiPF6 in a 3 : 7 volume mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixture. The XRD pattern of the products showed single phase SnC2O4ㆍ2H2O and rGO attached both were obtained without impurity. The fabricated cells were charged and discharged in the range of 0 - 3 V applying a constant current of 100 mAg-1 at 25 oC. The bare sample delivered capacity approximately 643 mAh g-1 at initial charge. Also, the delivered capacities increased to 1170, 1220, 1440 mAh g-1 with increasing the amount of rGO (10, 20, 30 wt%). The rate capability demonstrate that the 30 wt% rGO composite SnC2O4ㆍ2H2O / rGO electrode delivered 467 mAh g-1 at 10 C-rate. Figure 1

NaCrO2 Cathode for High-Rate Sodium-Ionbatteries

Layered lithium intercalation compounds LiMeO2 (where Me is transition element) materials have been widely studied and applied as cathode materials for practical lithium ion batteries. Cost of lithium resource, however, has doubled since commercialization in 1991, and tight supply is expected due to the ever increasing demands of electric vehicles and energy storage systems. Indeed, the lithium resource is unevenly distributed in Southern America. Meanwhile, sodium resources are abundant and unlimited everywhere. Recently, layered NaMeO2 materials are being intensively studied because of reversible Na+ insertion/extraction, in particular, NaCrO2 (R-3m) in Na cell. Here, we report physical and electrochemical properties of NaCrO2. The NaCrO2 powder was synthesized by solid-state method. Stoichiometric mixture of Na2CO3 and Cr2O3 powders were pelletized, and the pellet was heated at 900 oC in Ar. All chemicals and products were handled in an Ar-filled gloved box to avoid air exposure. Phase identification of the products was made using X-ray diffraction (XRD) with Cu Kα radiation and the collected XRD data were analyzed by the Rietveld refinement. Electrochemical test were carried out in coin type sodium cells. Galvanostatic electrochemical charge and discharge tests in 1M NaClO4 in PC solution were carried out at room temperature. XRD pattern of the produced NaCrO2 demonstrated a phase-pure product and it was crystallized to O3 type layer structure with space group of R-3m. The delivered capacity was approximately 110 mAh (gNaCrO2) -1 in voltage range of 2 – 3.6 V and 97 % of the capacity was retained during 50 cycles. Also, the Na/NaCrO2 cell exhibited surprising high rate properties, namely, 84 % of capacity retention at 100 C-rates. Details will be discussed in the conference site. Figure 1

Synthesis and Electrochemical Properties of Li2MnO3 Li4Mn5O12 Binary System As Positive Electrode Materials for Lithium Ion Battery

Synthesis and Electrochemical Properties of Li2MnO3―Li4Mn5O12 Binary System as Positive Electrode Materials for Lithium Ion Battery Masaki Okada and Yuya Sakaguchi Inorganic Materials Research Laboratory, TOSOH CORPORATION Lithium ion batteries are their high energy density compared with other batteries, progressed recently applied to applications requiring large capacity like for electric power storage system and electric vehicle. The positive electrode materials for a lithium ion battery, lithium metal oxide containing a large amount of rare metallic element such as cobalt or nickel are mainly investigated. Positive electrode material containing a large amount of these rare elements is very difficult to achieve both high energy density and low cost. As a positive electrode material that does not contain a rare metallic element, it is being studied of Li2MnO3 with a layered rock-salt structure. Li2MnO3 shows a large discharge capacity of more than 250mAh/g in the first cycle, but the capacity decreases with charge and discharge cycles. [1-3] In this work, we studied the Li2MnO3―Li4Mn5O12 binary system (Li4/3-4X/5Mn2/3O2-2X/5, 0<X<1) of the positive electrode materials based on Li2MnO3. Li4/3-4X/5Mn2/3O2-2X/5 can be suppressed capacity fading as compared with the conventional Li2MnO3. It may be able to achieve both low cost and high energy density. Li4/3-4X/5Mn2/3O2-2X/5 was prepared by reacting of mixture of MnCO3･0.5H2O and LiOH･H2O as raw material. The mixture was fired at 400～600ºC for 32h in air stream. Crystal structure and multilayered particle structure were investigated through TEM and N2adsorption-desorption isotherm analysis, respectively. The electrochemical characterization of positive electrode material was performed on CR2032 coin type cells. From the TEM images of the prepared samples, the presence of two crystal phases was observed. In addition, the electron diffraction pattern is attributed to the rock salt and the spinel phase, the possibility of a two-phase coexistence structure of Li2MnO3 and Li4Mn5O12 having a twin structure has been suggested. The initial charge and discharge capacity of Li4/3-4X/5Mn2/3O2-2X/5 was reduced as compared with Li2MnO3, but cycle stability was improved (X=0.36, 170mAh/g@50th, 50mA/g, RT). In additionally, capacity fading is suppressed by magnesium substitution of a part of manganese, the substituted sample showed stable cycling at about 200mAh/g (X=0.36, Mg 8mol %). In the viewpoint of the crystal structure and multilayered particle structure, the effect of the characters on capacity and cycle ability will be discussed. [1] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2009 156(6) A417-A424 [2] Denis Y.W. Yu et.al. J. Electrochem. Soc. 2010 157(11) A1177-A1182 [3] Denis Y.W. Yu et.al., J. Electrochem. Soc. 2011 158(9) A1015-A1022

Influence of Surface Area of Mesopore Volume on Discharge Characteristics for Lithium-Air Secondary Battery

Introduction Lithium-air secondary batteries have been expected to the next generation secondary battery due to extremely high theoretical energy density. The carbon material is generally used as a positive electrode material because of low cost and high conductivity. However, the overpotential is high because Li2O2 is deposited on the positive carbon electrode during discharge process and then blocks the diffusion path for lithium ion, oxygen, and electrolyte. Therefore, the structure of carbon material affects the electrochemical performance of lithium-air secondary battery. The relationship between the mesopore sutructure of the carbon material and the electrochemical performance is not clear. In this study, we prepared the various carbon electrodes using the porous carbons (CNovel) having larger surface area and pore volume and the conventional carbon material (acetylene black (AB)), and compared their electrochemical performances. Experimental CNovel MH (MH), CNovel P(2)010 (P(2)010), CNovel P(4)050 (P(4)050), and AB were used as the carbon materials. The carbon materials and polyvinylidene fluoride were mixed in an N-methyl-2-pyrrolidone solution. The obtained slurry was coated on the carbon paper and dried in vacuum at 80 oC overnight. After drying, the loading of the carbon material on the carbon paper was about 0.5 mg cm-2. The carbon electrodes were transferred into an argon-filled glovebox. The CR2032 coin type cell was assembled in the glovebox under argon atmosphere by using the obtained carbon electrodes (16 mm in diameter) as a positive electrode, lithium metal foil (16 mm in diameter) as a negative electrode, 1 mol dm-3 LiCF3SO3 dissolved in tetraethylene glycol dimethyl ether (TEGDME) as an electrolyte, and glass fiber filter (Whatman GF/A) as a separator. The separator was saturated with 1 mol dm-3 LiCF3SO3/TEGDME. For the electrochemical measurements, the discharge-charge tests were carried out in dry air atmosphere at 25 oC in the 2.0-4.5 V voltage range at the current density of 100 mA g-1. The specific capacity was calculated by the loading of the carbon material. Results and Discussion Fromthe pore size distribution of various carbon materials, the modal pore size of MH and P(2)010 was about 4 nm, while that of P(4)050 was about 50 nm. From the nitrogen adsorption-desorption isotherms, the order of the surface area of mesopore (mesopore range: 2-50 nm) was as follows: P(2)010 > MH > P(4)050 > AB. From the first discharge curves of various carbon electrodes (current density: 200 mA g-1), the discharge plateau voltages of P(2)010, MH, P(4)050, and AB electrodes were 2.69, 2.67, 2.68, and 2.58 V, respectively. Fig. 1 shows the relationship between the pore structure (the surface area of mesopore and the mesopore volume) of carbon materials and the first discharge capacity. The first discharge capacities of P(2)010, MH, P(4)050, and AB electrodes are 4231, 3652, 3552, and 2484 mAh g-1, respectively. The CNovel electrodes show higher first discharge voltage and capacity than the AB electrode. From Fig. 1a, the first discharge capacity increases with increasing the surface area of mesopore. The first discharge capacity is more strongly related to the surface area of mesopore than the mesopore volume. It was suggested that the increase in the thickness of the Li2O2 layer enhanced the overpotential. Therefore, the discharge reaction was cut off at the certain thickness of the Li2O2 layer. Based on these results, it was found out that the surface area of mesopore of the carbon material is more important parameter than volume for lithium-air secondary battery, since the thickness of the Li2O2 layer directly affects overpotential. References 1) J. Xiao et al., J. Electrochem. Soc., 157,A487-A492 (2010). 2) L. Wang et al., J. Power Sources, 234,8-15 (2013). 3) P. Guan et al., Electrochim. Acta, 129,326 (2014). 4) I. Landa-Medrano et al., J. Electrochem. Soc., 162,A3126-3132 (2015). Acknowledgments This research was partially supported by ALCA-SPRING, JST. Figure 1