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Electrochemical characteristics of low crystalline carbonaceous materials and carbonized non-graphitizable carbons as negative electrodes of rechargeable lithium-ion cells are reviewed, particularly from the viewpoint of the relationship linking the electrochemical characteristics and nano-structural features of these materials. These low crystalline materials show very attractive characteristics for negative electrodes of lithium-ion cells, e. g., reversible capacity higher than that of graphite (LiC6, 372mAh/g). In addition, carbonized non-graphitizable carbons display a significant capacity below 0.1V (vs. Li/Li+). These features are very important to improve specific energy of lithium-ion cells. 7Li-nuclear magnetic resonance (7Li-NMR) observation on lithium insertion into those materials suggested that lithium species in those materials are quite different from that in graphite. Lithium species in low crystalline carbonaceous materials have an ionic character. On the other hand, lithium in carbonized non-graphitizable carbons is classified into two species. One of the lithium species is the same as that in graphitizable carbons. However, the other lithium species are inferred to be lithium clusters, which gave 7Li-NMR peaks at 190 and 280ppm (vs. aq. LiCl) at -130°C. The structural characteristics, which form ionic lithium species and lithium clusters, are discussed.

Li1−yNi0.5Mn0.4Ti0.1O2 (y=0 and 0.5) was synthesized and characterized using X-ray diffraction, XAFS, and SQUID measurements. The samples were single-phase and adopted the α-NaFeO2 structure. Li1−yNi0.5Mn0.4Ti0.1O2 (y=0 and 0.5) can be represented as Li(Ni2+0.5Mn4+0.4Ti4+0.1)O2 and Li0.5(Ni3+0.5Mn4+0.4Ti4+0.1)O2, respectively. Structural analysis demonstrated that the lattice parameter a decreased from 2.895 to 2.856 A, the lattice parameter c increased from 14.317 to 14.509 A, and the Ni–O bond length decreased from 2.06 to 1.94 A with de-lithiation. The low occupation of Ni on the 3a site was confirmed from the ferromagnetic behavior caused by the 180° Ni2+(3a)–O–Mn4+(3b)–O–Ni2+ (3a) superexchange interaction. These results indicated that lithium de-intercalation from LiNi0.5Mn0.4Ti0.1O2 was controlled mainly by changing the valence state of Ni from 2+ to 3+.

Charge–discharge cycle performance was examined for the cell Li 1.08 Mn 1.92 O 4 /1 M LiPF 6 in EC:DEC(1:1)/MCMB. The structure and magnetic properties were determined before and after cycling using X-ray diffraction and SQUID measurements. After both 340 cycles at RT and 150 cycles at 55 °C, single-phase properties were observed for all samples, but samples in the discharged state showed broadening of X-ray diffraction peaks with decrease in the capacity retention ratio. Decreases in lattice parameter and increases in magnetic susceptibility were clearly observed for samples in the discharged state with decreased capacity retention ratios, while small changes in lattice parameter and magnetic susceptibility were observed for samples in the charged state. It was shown that Li intercalation/de-intercalation becomes difficult with cycling in the shallow charged state. Furthermore, it was suggested that the cell capacity decreases because of the disorder in the Li ion conductive pathway caused by the impaired stability of the samples.

The layered oxides LiNi1−xMnxO2 (x = 0.1–0.5) were synthesized and characterized using synchrotron X-ray diffraction, TOF neutron diffraction, SQUID magnetometry, ICP spectroscopy, XAFS, and electrochemical measurements. All the samples were single-phase and adopted the α-NaFeO2 structure; LiNi1−xMnxO2 can be represented as Li(Ni2+xNi3+1−2xMn4+x)O2. Structural analysis using synchrotron and neutron diffraction data demonstrated that the lattice parameters of LiNi0.5Mn0.5O2 are a = 2.892 A and c = 14.302 A and that the chemical composition can be expressed by referring to the Wyckoff positions 3a and 3b as [Li0.91Ni0.09]3a[Li0.09Mn0.5Ni0.41]3bO2. The lattice parameters a and c and the fraction of Ni at the 3a site of LiNi1−xMnxO2 increased with Mn content up to the x = 0.4 composition and then showed little change between x = 0.4 and 0.5. An increase in the Ni–O distance was observed with increasing x. The appearance of ferromagnetism was clearly observed at x = 0.4–0.5 as the Ni2+ and Mn4+ content increased. The discharge capacity of the Li/LiNi1−xMnxO2 cell decreased from 190 mAh g−1 (x = 0.1) to 140 mAh g−1 (x = 0.5).

Charge-discharge behaviors for tin-12% iron alloy films on electrolytic copper foils prepared by electroplating, which were low cost and made of environmentally friendly alloy, were investigated for X-ray a diffraction measurement, cyclic voltammetry and charge-discharge tests. Tin-12% iron alloy plating anodes showed a discharge capacity of 374 mAh/g after 50 cycles with metallic lithium as counter electrodes. From the results of cyclic voltammograms for tin-12% iron alloy plating anodes, the current value for lithium deposition increased around 0.26 V in the first cycle and increased around 0.68 V in the second cycle. The current value for lithium deposition in tin plating anodes increased around 0.66 V in the first cycle. These results suggested that iron was separated from tin-iron alloy plating film in the first charge and electric conductivity of tin-lithium intermetallic compounds formed bycharge-discharge reactions was improved by the dispersion of iron particles between these compounds. At a discharge rate of 5C(50 A/m2) tin-12% iron alloy plating anodes showed a discharge capacity of 285 mAh/g after 50 cycles and was applicable for high discharge rate. A coin-type cell(CR 2032) with a tin-12% iron alloy plating anode and a LiCoO2 cathode showed a discharge capacity of 273 mAh/g and coulombic efficiency of 90.4% after 95 cycles in charge-discharge tests at a constant charge capacity of 302 mAh/g. Therefore, tin-12% iron alloy plating anodes can be expected to substitute for carbon as high capacity anodes for advanced lithium secondary batteries.

High-temperature storage of the lithium manganese spinel cathode was examined for Li 1.02− x Mn 1.98 O 4 using 1 M LiPF 6 in EC:DEC (1:1) electrolyte solution. The structure, magnetic properties, and valence state of Mn were determined before and after the storage using Mn K -edge XANES, X-ray diffraction, SQUID, ICP spectroscopy, and electrochemical measurements. After the storage at 80 °C for 6 days, single-phase property was observed at x =0 and 0.96 in Li 1.02− x Mn 1.98 O 4 , while multi-phase property was observed between the compositions, x =0.18 and 0.63. Shallow de-lithiated region near x =0.18 was easily affected by the storage; the Li/Li 1.02− x Mn 1.98 O 4 cell showed large capacity failure from 111 to 40 mAh/g after the storage which corresponded to the phase transition with the increase in the valence state of Mn after the storage. Magnetic measurement was found to be quite sensitive and effective to detect the subtle structural changes caused by the high-temperature storage.

A series of gel polymer electrolytes containing PVdF as homo polymer, a mixture of 1:1 Ethylene Carbonate (EC) : Propylene Carbonate (PC) as plasticizer and lithium-bistrifluoromethane sulphone imide [imide — LiN (CF3SO2)2] has been developed. Amounts of polymer (PVdF), plasticizer and the imide lithium salt have been varied as a function of their weight ratio composition in this regard. Dimensionally stable films possessing appreciable room temperature conductivity values have been obtained with respect to certain weight ratio compositions. However, conductivity data have been recorded at different possible temperatures, i.e., from 20 °C to 65 °C. XRD and DSC studies were carried out to characterize the polymer films for better amorphicity and reduced glass transition temperature, respectively. The electrochemical interface stability of the PVdF based gel polymer electrolytes over a range of storage period (24 h – 10 days) have been investigated using A.C. impedance studies. Test cells containing Li/gel polymer electrolyte (GPE)/Li have been subjected to undergo 50 charge-discharge cycles in order to understand the electrochemical performance behaviour of the dimensionally stable films of superior conductivity. The observed capacity fade of less than 20% even after 50 cycles is in favour of the electrochemical stability of the gel polymer electrolyte containing 27.5% PVdF −67.5 % EC+PC −5% imide salt. Cyclic voltammetry studies establish the possibility of a reversible intercalation — deintercalation process involving Li+ ions through the gel polymer electrolyte.

18650-type cylindrical cells using LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) and hard carbon as positive and negative electrode material, respectively, were fabricated and degraded by cycle tests. The capacity of the cells remained more than 95% and 85% after cycle tests at 25 and 50 °C, respectively. After the cycle tests, Li-deficient cubic phase was observed on the surface of NMC. This phenomenon should be related to the degradation mechanism of this type of cell.

The synthesis of LiFeVO4 composition has been performed in air starting from Li2CO3, Fe2O3, and V2O5 and using the standard solid-state reaction route reported by Refs. [13] , [14] , [15] . Identical X-ray diffraction pattern has been obtained, however our careful analysis with MDI Jade 5.0 software does not agree with previously reported pure LiFeVO4 samples. The powder pattern has been perfectly indexed using the single crystal data of LiVO3 (C2/c, a = 10.16718 A, b = 8.415725 A, c = 5.884155 A and β = 110.489°) and α-Fe2O3 (R-3c, a = 5.035 A, c = 13.75 A).

Thermal stability of cathode materials, including LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , V 2 O 5 , V 6 O 13 , and Li x MnO 2 in contact with poly(ethylene oxide) (PEO) based solid polymer electrolyte was systemically investigated by means of thermal analysis in combination with X-ray diffraction technique (XRD). The differential scanning calorimetry (DSC) analysis showed significant exothermic reaction of both LiNiO 2 and LiCoO 2 in contact with the polymer electrolyte. LiMn 2 O 4 was less reactive compared with LiNiO 2 and LiCoO 2 . V 2 O 5 , V 6 O 13 , and Li x MnO 2 were also found less reactive, especially in their discharge states. The XRD results indicated that the thermal decomposition products of the cathode material were the low valance metal oxides, suggesting the exothermic reaction was an oxidation reaction of the polymer electrolyte with active material. The decomposition temperature is somehow dependent on the potential of the cathode active materials. Cyclic voltammetry reveals that PEO based solid polymer electrolyte is stable up to 5.0 V versus Li/Li + at a blocking electrode, whereas it decomposes at ca 3.8 V when contacted with a carbon composite electrode.

A complex of polymer, plasticizer and lithium salts can be used as a solid gel polymer electrolyte in lightweight and rechargeable lithium batteries. Considerable research has been directed towards the development of a gel polymer with high conductivity at room temperature. In this work, a gel polymer electrolyte using polyvinylidene fluoride (PVdF)-1000 (KF), a plasticizer of 1:1 ethylene carbonate (EC) and propylene carbonate (PC), and LiBF 4 salt is optimized. Gel electrolytes have high ionic conductivity, good mechanical stability, a wide electrochemical stable window, and a stable lithium interface. The results of preliminary charge–discharge of cells are discussed in detail.

Lithium fully inserted into both graphitizable and non-graphitizable carbons has been investigated by 7 Li -NMR spectroscopy at low temperatures. It was found that lithium only in the non-graphitizable carbons heat-treated at ca. 1000°C showed peak separation phenomena at temperatures below −30°C. This peak separation is explained as exchange of lithium nuclei between different kinds of lithium species in the carbons. In addition, an equilibrium relationship between the lithium species in the non-graphitizable carbons was found in the temperature range from −30 to −150°C.

Lithium intercalation of natural graphite and well-graphitized vapor-grown carbon fibers has been investigated by solid-state {sup 7}Li-NMR and by cyclic voltammetry. Chemical shift of {sup 7}Li in Li-graphite intercalation compounds (Li-GICs) of natural graphite occurs in two regions, >40 and

By means of a surfactant-assisted hydrothermal method, we have successfully synthesized sodium manganese oxide nanorods with 2 × 4 tunnel structure using layered manganese oxide as starting material. The nanorods have diameters of ca. 20 nm and lengths up to 1 μm. Not only the morphological change of manganese oxide from particle to rod but also the structural change from layer to tunnel have simultaneously been achieved during the hydrothermal treatment. The specific capacitance of thus obtained nanorods reaches to 140 F/g. About 57% of the capacitance at 1 mV/s could be maintained when the scan rate was increased to 100 mV/s.

KC8 and KC24 were allowed to react with several unsaturated hydrocarbons. After contact with isoprene, styrene or 1,3-butadiene, potassium—graphite intercalation compounds (GICs) expanded slowly along the c-axis direction. Molecules of unsaturated hydrocarbons are considered to be introduced into the interlayer spacing of GICs and polymerized progressively. When acrylonitrile, 1-butene or isobutene is used as the unsaturated hydrocarbon, the interaction between GICs and hydrocarbons is quite different. Monomer molecules are polymerized only in the vicinity of the sample edge, which enhances the stability of potassium—GICs in water. Two other kinds of interaction between alkali metal—GICs and unsaturated hydrocarbons, i.e. intercalation with and without oligomerization, are also reported elsewhere by several authors. We classified the interaction into four categories mainly according to the reactivity of unsaturated hydrocarbon for polymerization.

Non-graphitizable carbon fibers heat-treated between 1000 and 1200 °C gave capacity higher than the capacity of LiC6 (372 mAh g−1) with a significant capacity below 0.1 V during oxidation. 7Li nuclear magnetic resonance (7Li-NMR) observation on lithium insertion into the carbon fibers suggested that lithium in the carbons are classified into two species. One of the lithium species was the same as that in graphitizable carbons. However, the other lithium species was quite different from that in graphitizable carbons, because the line shifts in the 7Li-NMR spectra of the carbon fibers fully lithiated to 0 V were between 80–110 ppm (versus LiCl); these shifts are larger than the maximum shift of lithium in graphitizable carbons (∼45 ppm). In particular, a significant capacity below 0.1 V corresponded to the formation of a new lithium species.

Crystallographic and electrochemical characteristics of a carbon as a by-product of a SiC production in an Acheson-style furnace were examined as an anode material of rechargeable lithium-ion batteries. The X-ray diffraction pattern of the carbon indicates that the carbon is highly graphitized. The fine powder (9.4μm in average) of the carbon gave a reversible capacity of ca. 370 mAh g-1 between the cut-off voltages, 0 and 2.5V (vs. Li/Li+), in 1 mol dm-3-LiClO4/ethylene carbonate + diethylcarbonate (50: 50 mixture in volume) electrolyte. Moreover, the potential change of the carbon during the electrochemical intercalation and deintercalation of lithium was almost the same as that of natural graphite showing slopes and plateaus. These results indicate that the carbon is an artificial graphite as well graphitized as natural graphite.

In the last two decades, demand for rechargeable batteries with high specific energy or high energy density has been increasing for applications in portable electronic devices such as mobile phones (feature phones and smartphones), notebook personal computers (PCs), and tablet PCs. Since these electronic devices possess relatively large and bright display panels (liquid-crystal or organic electroluminescence), smaller and lighter rechargeable batteries are required to lengthen the devices’ battery life. Furthermore, the need is rapidly increasing for electrochemical power sources applied to electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in HEVs (PHEVs). In particular, the European Union (EU) CO2 emission regulation proposed for 2020 has made a strong impact on future automotive power trains, and EVs and PHEVs are thought to be indispensable for meeting this regulation.

The stacking order of graphite layers in mesocarbon microbeads (MCMBs) heat-treated between 700 and 3,000 C was examined by analyses of X-ray diffraction measurements, and lithium insertion into the MCMBs has been observed using solid-state {sup 7}Li-nuclear magnetic resonance ({sup 7}Li-NMR) spectroscopy. In MCMBs heat-treated above 2,000 C, the fully lithiated MCMBs showed two bands at ca. 45 ppm (vs. KiCl) and ca. 27 ppm in their {sup 7}Li-NMR spectra. The profile of the band at 45 ppm was very close to that for the first-stage lithium graphite intercalation compound (Li-GIC), though the other band at 27 ppm could not be assigned to any phases of Li-GICs. From these results, it is suggested that the structures of the MCMBs heat-treated above 2,000 C for lithium insertion are classified as graphitic structure, which has the AB stacking order of graphite layers, and turbostatic structure with a random stacking sequence of graphite layers; the fully lithiated compositions of both structures were estimated as LiC{sub 6} and ca. Li{sub 0.2}C{sub 6}, respectively. Although MCMB heat-treated at 700 C gave a higher capacity than LiC{sub 6}, the line shift in the {sup 7}Li-NMR spectra indicated that lithium stored in the MCMB displayed an ionic more » character. Capacity change of the MCMBs during charge-discharge cycling up to 20 cycles and capacity loss at higher current densities (

The crystal structures and electron density distributions of the layered oxide Li1−yNi0.5Mn0.5O2 (y = 0.5) were studied using a combination of Rietveld analysis of high-resolution synchrotron powder X-ray diffraction data and the maximum entropy method (MEM). Structural analysis revealed that Li1−yNi0.5Mn0.5O2 (y = 0.5) has the lattice parameters a = 4.934 A, b = 2.852 A, c = 5.090 A, β = 108.8° and adopts the space group C2/m. The chemical formula can be expressed as [Ni0.0815]2a{Li0.5Ni0.0115}4i[Mn0.5Ni0.407□0.093]2dO2. The electron density map obtained using MEM clearly shows that most of the Li ions migrate from the octahedral 2a site to the tetrahedral 4i site during Li de-intercalation.

Ionic liquids (ILs) have been studied as a unique electrolyte for a lithium battery for a past two decades 1). The thermal stability and less-volatility have been expected to improve safety of a conventional lithium ion battery system using flammable non-aqueous electrolytes. For example, using bis(trifluoromethylsulfonyl)imide (TFSA-) –ILs as a electrolyte, LiFePO4 half cell could be charged and discharge over 100 °C 2). In this study, we will report that another unique and important features of a zero-solvent electrolyte like ILs was indicated at a high voltage (> 4.7 V) charging and discharging cycle using a transition metal oxide cathode as a LCO and NMC. A modification of NMC by coating with Al2O3 particle successfully improved the high voltage operation over 4.2 V as already reported 3). However, we found that a LCO and also NMC cathode without any coating could be stable over 4.7 V charging and discharging cycle even in 1-ethyl-3-methylimidezolium bis(fluoromethylsulfonyl)amide ([EMI][FSA]) containing a certain amount of Li[FSA]. This finding indicate that a catalytic site for oxidation decomposition of a conventional organic electrolyte on a transition metal oxide, which was deactivate by a surface coating with Al2O3, did not affect the oxidation of the ionic liquids electrolyte, which did not contain any organic solvents. On the other hand, a cycle stability at a high temperature over 45 °C was effectively stabilized by a surface coating on NMC with ZrO2. The result implies that the surface modification of a transition metal cathode effectively protected the structural disorder of a cathode material by a high temperature condition. These results show that using zero-solvent electrolyte like ILs might be a useful tool to elucidate the effect of surface modification in an organic solvent electrolyte. Acknowledgment This work was supported by the “Research & Development Initiative for Scientific Innovation of New Generation Batteries (RISING)” project of the New Energy and Industrial Technology Development Organization (NEDO). 1) H. Matsumoto, in Electrolytes for Lithium-ion Batteries, eds. T. R. Jow, K. Xu, O. Borodin and M. Ue, Springer, 2014, ch.4. 2) H. Matsumoto and K. Kubota, ECS Transactions, 64(4), 425 (2014). 3) K. Araki, N. Taguchi, H. Sakaebe, K. tatsumi, Z. Ogumi, J. Power Sources, 269 (2014) 236.

A lithium-ion rechargeable battery based on carbon anode, a viable replacement for lithium metal anode, has been developed. Lithium-ion rechargeable batteries are considered to have high capacity and high safety. For this reason, we have investigated rechargeable batteries with higher energy density, and studied host carbon materials for the anode, in particular. In this investigation, the vapour-grown carbon fibre was used as the anode material. This carbon fibre after graphitization showed high capacity (363 mAh/g carbon) and low potential (versus Li Li + ). It showed good stability during cycling, and is expected to be a suitable anode material in lithium-ion rechargeable batteries. Further, a coin-type cell was prepared with this carbon anode and LiCoO2 cathode, and the performance during galvanostatic charge/discharge cycling observed. This coin-type battery has a high energy density.

Chopped vapor-grown carbon fibers (VGCFS) were studied as anodes for secondary lithium ion batteries using a 1 mol/dm{sup 3} LiClO{sub 4} in a 1:1 (by volume) mixture of ethylene carbonate (EC) and diethylcarbonate (DEC) electrolyte. VGCFs were prepared from hydrocarbons by a vapor-grown method and chopped to ca. 10 {mu}m length. Three different diameters of the VGCFS, 1, 2, and 3 {mu}m (1GWH, 2GWH, and 3GWH, respectively) were used. The VGCFs chopped after graphitization (the 2A method-VGCFs) displayed a higher capacity than those chopped before (the 1A method-VGCFs). In particular, 2GWH-2A gave a capacity of 363 mAh/g carbon, 1.6-fold higher than the capacity of 2GWH-1A; this is almost equal to the theoretical intercalation capacity of an ideal graphite (LiC{sub 6}). The cyclic voltammogram of 2GWH-2A showed the most significantly different profile from that of natural graphite among all of the VGCFs. It is suggested that a new structural change is induced in the well-graphitized VGCFs during the chopping process that affects the lithium storage reaction.

Graphite whiskers, produced by Nikkiso Co., Ltd., (sample code 2GWH-2A) have been investigated with respect to their electrochemical characteristics in different types of liquid electrolytes: LiClO4, LiPF6, LiAsF6, LiBF4, LiCF3SO3 in ethylene carbonate-diethyl carbonate and in solid electrolytes. A high capacity (363 mAh/g) is obtained when a liquid electrolyte was used and 330 mAh/g at 80 °C in the case of a polymer electrolyte. The coulombic efficiency during the first cycle is lower when polymer electrolyte is used. 2GWH-2A shows very different performances in LiClO4 and in LiPF6 electrolytes. The degree of intercalation depends upon of the nature of the binder, composition of the electrode and electrolyte. The color of the carbon electrode also changed from black to gold in the presence of some lithium salt electrolytes, when lithium was fully intercalated into the electrode. The galvanostatic charge/discharge tests show a large plateau near 0 V. On measuring the slow cyclic voltammogram of the 2GWH-2A, five cathodic peaks were observed.

Carbon is one of the best candidate materials for the negative electrode of rechargeable lithium batteries; however, the electrochemical characteristics are not fully understood in terms of the structure of the materials. The relationship linking the volume ration of the graphitic structure (P{sub 1}) of mesocarbon microbeads (MCMBS) and the electrochemical characteristics has been examined, and it was found that the capacity in the range between 0 to 0.25 V (vs. Li/Li{sup +}) in 1 mol/dm{sup 3} LiClO{sub 4}/ethylene carbonate (EC) + 1,2-diethoxyethane (DEE) electrolyte increased with an increase of the P{sub 1} of the MCMBs. This result shows that the lithium storage mechanism in this potential range is the lithium-intercalation reaction into the graphitic layers with the AB or ABC stacking. On the other hand, MCMB heat-treatment temperature (HTT) 1,000 C showed much larger capacity in the range between 0.25 to 1.3 V than higher HTT MCMBs, and it is suggested the interaction among each graphite layer is weaker in nongraphitized carbon than that in well-graphitized ones.

Lithium intercalation of natural graphite and well-graphitized vapor-grown carbon fibers has been investigated by solid-state {sup 7}Li-NMR and by cyclic voltammetry. Chemical shift of {sup 7}Li in Li-graphite intercalation compounds (Li-GICs) of natural graphite occurs in two regions, >40 and

Electrical resistivity of graphite is presented in the temperature range 900-2800K. In an atmosphere of nitrogen, electrical resistivity of isotropic graphite IG-110 increases with an increase in temperature. On the other hand, the temperature dependence of electrical resistivity in an atmosphere of argon is different: a significant decrease of electrical resistivity was observed above ca. 2400K. It was suggested that argon was not inert at temperatures above about 2400K, and affected the resistivity of graphite through some ionization or other reactions.This atmosphere dependence of the electrical resistivity at elevated temperatures is thought to be generall phenomenon in measuring the resistivity of graphite, because the atmosphere dependence was also observed for other artificial graphites.

The proposed intermediate for the hydrocyanation of PhCCH and cyanation of PhC(Br)CH 2 by cyanocobaltate has been isolated as K 3 [CH 2 C(Ph)Co(CN) 5 ]·2H 2 O. The effect of the CN:Co ratio on its formation from PhCCH and on its decomposition to form nitriles has indicated that [CH 2 C(Ph)Co(CN) 5 ] 3− is not a real intermediate in formation of PhC(CN)CH 2 , and that the importance of a ratio of CN:Co

Valence state changes in Li1−yNi1/3Mn1/3Co1/3O2 were investigated using hard and soft X‐ray absorption fine structure (XAFS) measurements. Reversible changes in the M–O bond lengths and in the position of the M L‐edge peak (M = Ni, Co) were observed during the first charge and discharge cycle. These results demonstrate that Li de‐intercalation/intercalation proceeds mainly by changes in the valence states of the Ni and Co cations. In addition, it has been shown that the host material LiNi1/3Mn1/3Co1/3O2 had a surface structure free of Li2CO3.

New cyclic quaternary ammonium salts, composed of N-alkyl-(alkyl ether)-N-methylpyrrolidinium, -oxazolidinium, -piperidinium, or -morpholinium cations (alkyl=nC 4 H 9 , alkyl ether=CH 3 OCH 2 , CH 3 OCH 2 CH 2 ) and a perfluoroalkyltrifluoroborate anion ([R F BF 3 ] - , R F =CF 3 , C 2 F 5 , nC 3 F 7 , nC 4 F 9 ), were synthesized and characterized. Most of these salts are liquids at room temperature. The key properties of these salts-phase transitions, thermal stability, density, viscosity, conductivity, and electrochemical windows-were measured and compared to those of their corresponding [BF 4 ] - and [(CF 3 SO 2 ) 2 N] - salts. The structural effect on all the above properties was intensively studied in terms of the identity of the cation and anion, variation of the side chain in the cation (i.e., alkyl versus alkyl ether), and change in the length of the perfluoroalkyl group (R F ) in the [R F BF 3 ] - ion. The reduction of Li + ions and reoxidation of Li metal took place in pure N-butyl-N-methyl-pyrrolidinium pentafluoroethyltrifluor-oborate as the supporting electrolyte. Such comprehensive studies enhance the knowledge necessary to design and optimize ionic liquids for many applications, including electrolytes. Some of these new salts show desirable properties, including low melting points, high thermal stabilities, low viscosities, high conductivities, and wide electrochemical windows, and may thus be potential candidates for use as electrolytes in high-energy storage devices. In addition, many salts are ionic plastic crystals.

A series of new hydrophobic ionic liquids comprising N-alkyl(alkyl ether)-N-methylpyrrolidinium and perfluoroethyltrifluoroborate were prepared and characterized. The new [C2F5BF3]−-based salts sho...

New hydrophobic ionic liquids consisting of trialkyl(2-methoxyethyl)ammonium ([R1R2R3NCH2CH2OCH3]+, R1, R2, R3 = CH3 or C2H5) cation and perfluoroethyltrifluoroborate ([C2F5BF3]−) anion were prepar...

A series of twenty two hydrophobic ionic liquids, 1-alkyl(alkyl ether)-3-methylimidazolium ([C(m)mim]+ or [C(m)O(n)mim]+; where Cm is 1-alkyl, Cm = nCmH(2m+1), m = 1-4 and 6; C(m)O(n) is 1-alkyl ether, C2O1 = CH3OCH2, C3O1 = CH3OCH2CH2, and C5O2 = CH3(OCH2CH2)2) perfluoroalkyltrifluoroborate ([RFBF3]-, RF = CF3, C2F5, nC3F7, nC4F9), have been prepared and characterized. Some of the important physicochemical properties of these salts including melting point, glass transition, viscosity, density, ionic conductivity, thermal and electrochemical stability, have been determined and were compared with those of the reported [BF4](-)-based ones. The influence of the structure variation in the imidazolium cation and the perfluoroalkyltrifluoroborate ([RFBF3]-) anion on the above physicochemical properties was discussed. The key features of these new salts are their low melting points (-42 to 35 degrees C) or extremely low glass transition (between -87 and -117 degrees C) without melting, and considerably low viscosities (26-77 cP at 25 degrees C).

In general, a carbon whisker is prepared from hydrocarbons using a vapor-grown method and chopped to a suitable length. Two procedures were examined to prepare the whiskers: in the normal procedure (1A), whiskers were graphitized after the chopping process, and in the other process (2A), they were chopped after the graphitization. The carbon whisker of 2 μm in length by the 1A procedure (2GWH-1A) showed an average capacity of 248 mAh g−1. On the other hand, the whisker of the same diameter by the 2A process (2GWH-2A) showed a much higher capacity of 363 mAh g−1: this value is 1.6 times of that of 2GWH-1A. This modification method may open a new probability to higher performance carbon materials for the anode.

Introduction Lithium titanium oxides such as spinel-type Li4Ti5O12 and ramsdellite-type Li2Ti3O7 have been extensively investigated as electrode materials for rechargeable Li-ion batteries. In recent, another metastable phase of Li2Ti3O7 with Na2Ti3O7-type layered structure have been reported with the structural details and electrochemical Li-ion insertion properties [1]. On the other hand, NaLiTi3O7 has been investigated as electrode materials for rechargeable Li-ion batteries [2]. This Ti4+/Ti3+ electrode showed lower operating voltage compared to Li4Ti5O12. In addition, NaLiTi3O7 has a three-dimensional tunnel structure which is thought to be favorable for fast Li-ion transfer. This compound can be prepared by a conventional solid state reaction. Li2Ti3O7 with the NaLiTi3O7-type structure may be prepared by ion exchange of NaLiTi3O7 (Fig. 1). Higher Li-ion insertion capacities similar to that observed in Li2Ti3O7 with Na2Ti3O7-type layered structure can be expected. However, to our knowledge, synthesis, the structural details and electrochemical Li-ion insertion reactions in this compound have not been reported yet. In the present study, we have successfully synthesized single-phase sample of Li2Ti3O7 with the NaLiTi3O7-type structure and determined its crystal structure by Rietveld analysis. Furthermore, the Li-ion insertion properties of this compound have been clarified for the first time. Experimental The precursor NaLiTi3O7 was first prepared by a conventional solid state reaction by using a method similar to that reported previously [3]. A mixture of Na2CO3 (99.9% pure), Li2CO3 (99.99% pure) and TiO2 (99.99% pure) in a molar ratio of 1.01:1.03:3 was heated at 950°C for 24 h in air. Then, the lithiated Li2Ti3O7 samples were prepared from NaLiTi3O7 via ion exchange at a low temperature. Sodium/lithium ion exchange experiments were performed using the molten salt of LiNO3. Ion exchange reaction was performed at 400°C for 6h in air. After heat treatment, the reaction mixture was washed with ethanol and then dried at 80°C for 1 day in air. Further Li-ion exchange treatment was accomplished by heating the as prepared Li2Ti3O7 in molten LiNO3at 380°C for 6 h in air. The phase purity and crystal structure of the obtained samples were characterized by powder X-ray diffraction (XRD) using a Bruker AXS D8 ADVANCE diffractometer with Cu Kα radiation source filtered by a Ni thin plate (Cu Kα radiation, operating conditions: 40 kV, 55 mA). The particle morphology and chemical composition were verified by scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDX; Keyence VE-8800). The chemical and structural characteristics were evaluated using ICP, DTA and FTIR measurements. Electrochemical lithium insertion/extraction experiments were performed using lithium coin-type cells (CR2032-type). The working electrode were made of 80wt% active materials, 10wt% carbon black (Super-P) as a conductive agent, and 10wt% poly(vinylidene difluoride) as a binder. Copper foil was used as a current collector, and the area of the electrode was a diameter of 14 mm. The counter electrode was a Li foil having a diameter of 16 mm. The separator was a microporous polypropylene sheet. A solution of 1 M LiPF6 in a 1:2 mixture of ethylene carbonate (EC) and dimethycarbonate (DMC) by volume (Mitsubishi Chemical Co., Ltd.) was used as the electrolyte. Cells were constructed in a dry room, and electrochemical measurements were carried out with a current density of 10 mA g−1between 0.5 and 2.0 V at 25°C after standing 6h under an open circuit condition. Results and discussion Figure 2 presents the XRD patterns of the NaLiTi3O7 and Li2Ti3O7 samples. These data suggested that the products were single-phase samples of NaLiTi3O7 and Li2Ti3O7. Chemical analysis confirmed that the removal of Na was not complete at the present experimental condition. The electrochemical measurements revealed that the initial Li insertion capacities were 152 mAh g−1 and 243 mAh g−1 for NaLiTi3O7 and Li2Ti3O7, respectively, which were equivalent to 1.62 and 2.45 electron transfer per each formula unit. In addition, reversible Li-ion insertion and extraction reactions were observed in these samples, although a capacity loss of approximately 50 mAh g−1 and 75 mAh g−1 for the first cycle was observed in NaLiTi3O7 and Li2Ti3O7, respectively. Acknowledgement This work was supported by the “Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING project)” of the New Energy and Industrial Technology Development Organization (NEDO; Japan). References [1] K. Chiba et al., Solid State Ionics, 178, 1725 (2008). [2] S.Y. Yin et al., Electrochem. Commun., 11, 1251 (2009). [3] L.M. Torres-Martínez et al., Solid State Sci. 8, 1281 (2006).

Improvement technique of the life of Li-ion batteries has been intensively studied. Modification of the surface of positive electrode material including coating is effective to this purpose. In that process, it is very important to compare the bulk and surface structure of the positive electrode with/without surface modification to understand this effect. For basic information concerning the effect of surface modification, authors have applied Transmission Electron Microscopy (TEM) to visualize the structural distribution inside the positive electrode particles after degradation [1]. As a model material, we synthesized sub-micron size particle of positive electrode such as LiCoO2 by Pechini sol-gel method [2, 3] that could provide the suitable sample for TEM observation without damages from sample preparation like ion-milling or FIB. Analytical TEM measurements by scanning transmission microscopy (STEM) with electron energy-loss spectroscopy (EELS) equipped with monochromator were applied. Li-K EELS peak around 62 eV was clearly found and this peak intensity changed with Li charge-discharge state. The EELS mapping from the spectrum imaging method using this Li-K region spectra showed a distribution of Li in the particle or among particles during the charge discharge cycle. We discuss precisely the change of chemical states at the surface and Li ion distribution inside particles of positive electrode material with/without surface modification using Si, Zr, Al, Mg oxide during charge-discharge cycle. References [1] N. Taguchi, T. Akita, H. Sakaebe, K. Tatsumi, Z. Ogumi, J. Electrochem. Soc., 160, A2293 (2013). [2] Y. Sun, I. Oh, S. Hong, J. Mat. Sci., 31, 3617 (1996).

1. Introduction Lithium sulfide (Li2S) is one of the promising cathode active materials for high-energy rechargeable lithium batteries, because it has a high theoretical capacity (ca. 1170 mAhg-1) and has an advantage that a variety of anode materials without lithium sources are applicable in the practical battery system [1]. However, this material is both electronically and ionically resistive, which gives rise to low active material utilization in the cells [2]. Several attempts have been performed to enhance the conductivity of Li2S, such as forming composites with several metals (Li2S-Fe, Li2S-Cu) [1,2] or carbon [3-5]. Recently, we have tried to prepare the composite with FeS2 (Li2S : FeS2 = 1 : 1 molar ratio) using the spark-plasma-sintering (SPS) process and found that the cells showed the initial charge capacity of ca. 330 mAhg-1 [6]. For improving the charge capacity, preparation of the composite with Li2S-rich composition is required. In the present work, we tried to prepare the Li2S-FeS x -C (x = 1, 2) composites with a Li2S : FeS x = 4 : 1 molar ratio using the combination processes of the SPS and the mechanical milling, and examined their electrochemical properties. 2. Experimental Li2S and FeS2 (or FeS) with a molar ratio of 4 : 1 were mixed thoroughly, and the mixture was then treated by the SPS process [6] at 600oC. The resulting pellet was ground and mixed with carbon (acetylene black) powder with a weight ratio of Li2S-FeS x : C = 9 : 1, and then it was mechanically milled for 8 h to yield the Li2S-FeS x -C composites. All the procedures were carried out in an argon atmosphere, because Li2S is very sensitive to atmospheric moisture. The obtained composite samples were characterized by XRD, as well as Fe and S K-edge XAFS measurements. Electrochemical lithium insertion / extraction reactions were carried out using lithium coin-type cells with 1M LiPF6 / (EC + DMC) electrolyte at a current density of 46.7 mAg-1 (corresponding to 0.04C) initially with charging. For improving the electrochemical performances, we applied pre-cycling treatment to the present Li2S-FeS x -C composite sample cells, whereby cycle capability of some oxide cathode active materials (such as Li(NiCoMn)O2) was successfully improved [7]. 3. Results and Discussion The obtained Li2S-FeS x -C composite samples were black in color, and their XRD patterns showed that they consisted of Li2S (antifluorite structure) with low crystallinity. The atomic ratio, estimated by ICP and atomic absorption spectroscopy, was Li : Fe : S = 7.8 : 1.0 : 4.8 for the Li2S-FeS x -C composite sample with Li2S : FeS = 1 : 4. Since the initial composition was Li : Fe : S = 8 : 1 : 5, this result indicates that negligibly slight amounts of Li and S (ca. 3 – 4%) were lost during the SPS and the following milling processes. The electrochemical tests for the Li2S-FeS x -C sample cells showed that the initial charge capacity was ca. 600 mAhg-1, which was much higher than the previously reported Li2S-FeS2 (1 : 1 molar ratio) sample cells (ca. 330 mAhg-1) [6]. The discharge capacity was ca. 330 mAhg-1 with the normal electrochemical cycling, and it was enlarged to ca. 730 mAhg-1 after the pre-cycling treatment, Fig. 1. This result indicates that the pre-cycling treatment was effective for improving the electrochemical performances of the Li2S-FeS x -C composite cells. Ex-situ XRD measurements showed that the peaks ascribed to Li2S disappeared after the normal electrochemical cycling, while they were still observable after the pre-cycling treatment. Also, ex-situ S K-XAFS measurements showed the reversible changes of the valence states of S atom with the pre-cycling treatment. Therefore, the pre-cycling treatment of the Li2S-FeS x -C sample was effective for maintaining the antifluorite structure, as well as for improving the reversibility of the valence states of S atom, which would be responsible for improving the electrochemical performances of the Li2S-FeS x -C composite sample cells. References [1] A. Hayashi et al., J. Power Sources, 183, 422 (2008). [2] M. N. Obrovac and J. R. Dahn, Electrochem. Solid-State Lett., 5, A70 (2002). [3] T. Takeuchi et al., J. Power Sources, 195, 2928 (2010). [4] J. Hassoun et al., J. Power Sources, 196, 343 (2011). [5] M. Nagao et al., J. Mater. Chem., 22, 10015 (2012). [6] T. Takeuchi et al., J. Electrochem. Soc., 159, A75 (2012). [7] A. Ito et al., J. Power Sources, 183, 344 (2008). Acknowledgment This work was financially supported by R&D project for lithium batteries (RISING Project) by METI and NEDO.

Achieving high capacity by making use of multi electron processes has been desired to enhance the energy density of lithium-ion batteries. Recently, layered lithium metal oxides with more than one equivalent of lithium per transition metal have been actively researched and developed as new positive-electrode materials with capacities of more than 200 mAh g−1. However, it is still difficult to achieve reversible capacity of more than 300 mAh g−1. To achieve the high capacity, the redox reaction of anions in addition to that of transition metals is needed to be used; that is, the charge and discharge with processes involving more than two-electrons should be required in materials. Therefore, the challenging is development of new electrode active materials which can show redox reactions with more than two electron processes. Metal sulfides are attractive candidates for positive-electrode materials [1, 2]. Their high capacities originate from charge and discharge processes that involve more than one electron; for example, crystalline TiS3 charges and discharges with high reversible capacities of greater than 300 mAh g−1, which corresponds to ca.1.5 electron redox reaction. In this study, amorphous titanium polysulfides a-TiSx (x = 3, 4) and niobium polysulfides a-NbSy(y = 3, 4, 5) were prepared by a mechanical milling process and their electrochemical properties were examined using the cells with carbonate-based electrolytes. Amorphous titanium and niobium polysulfides were mechanochemically synthesized at room temperature using a planetary ball mill apparatus. Sulfur (S8) and titanium disulfide (TiS2) or niobioum disulfide (NbS2) were used as starting materials. The XRD measurements indicated that the diffraction peaks attributable to S8 and TiS2 or NbS2disappeared by mechanical milling, suggesting that the samples became amorphous. Fig. 1 shows charge-discharge curves of the cells using crystalline NbS2 reagent, amorphous NbS3, NbS4, and NbS5. The capacity increases with increasing sulfur/metal ratio and the cell using amorphous NbS5 shows a high capacity of ca 600 mAh g-1. The amorphous TiS4 discharged and charged with a high reversible capacity of ca. 700 mAh g-1in the 1.5–3.0 voltage range [3]. The cell using the amorphous metal polysulfides charged and discharged despite of the use of a carbonate-based electrolyte. Coulombic efficiency of the composite was higher than that of a sulfur electrode because the dissolution of the polysulfide into electrolytes was suppressed. Designing amorphous polysulfides is an effective way to develop novel sulfide-based electrode materials with high capacity. References [1] M. S. Whittingham, Prog. Solid State Chem. 12 (1978)41–99. [2] M.H. Lindic, H. Martinez, A. Benayad, B. Pecquenard, P. Vinatier, A. Levasseur, D. Gonbeau, Solid State Ionics, 176 (2005) 1529–1537. [3] A. Sakuda, N. Taguchi, T. Takeuchi, H. Kobayashi, H. Sakaebe, K. Tatsumi, Z. Ogumi, Electrochem. Commun. 31 (2013) 71–75.

Introduction In order to enhance cycleability of positive electrode materials, coating of metal oxides [1], phosphates [2], and fluorides [3] have been reported to be effective on depressing degradation of positive electrode materials. However, so far, mechanisms of surface modification by coatings have not been clarified well. In recent, we have reported that Al oxides coating significantly suppressed the increase of cracks in LiNi1/3Co1/3Mn1/3O2 particle, and that both capacity and area specific impedance retentions of LiNi1/3Co1/3Mn1/3O2during charge-discharge cycles were improved by the coating [4]. In this paper, effect of coating of various metal oxides on electrochemical characteristics and cycleability enhancement of LiNi1/3Co1/3Mn1/3O2 particles during high voltage charge higher than 4.5 V (vs. Li+/Li) have been examined. Furthermore, effects of coating of various metal oxides on crystal structure deformation at the surface of LiNi1/3Co1/3Mn1/3O2during the charge-discharge cycles were investigated by s-TEM/EELS. Experiments Precursors of metal oxides (Al oxides, Zr oxides, etc.) were coated on LiNi1/3Co1/3Mn1/3O2 particles by sol-gel methods. The precursors coated LiNi1/3Co1/3Mn1/3O2 particles were calcined at 500°C to obtain metal oxides coated LiNi1/3Co1/3Mn1/3O2. Coat layers of metal oxides and surface area of LiNi1/3Co1/3Mn1/3O2 were observed by high resolution s-TEM. Electrochemical characteristics of bare and metal oxides coated LiNi1/3Co1/3Mn1/3O2 were examined in pouch cells with using Li metal counter electrode. The electrolyte used was 1M-LiPF6/EC+DMC +EMC (1:1:1 by volume). The cells were cycled between discharge cutoff voltage of 2.5 V and charge cutoff voltages of 4.5, 4.6 and 4.7 V. Results and discussion Figure 1 shows an s-TEM image and EDX mappings (Al, Ni, and Co) of cross section of Al oxides coated LiNi1/3Co1/3Mn1/3O2. The high resolution s-TEM/EDX observation revealed that coated Al oxides exist as a solid solution (LiTMO2-LiAlO2) from the surface to depth of several nm. Figure 2 shows effect of Al oxides coating on capacity retention of LiNi1/3Co1/3Mn1/3O2 during the charge-discharge cycles. Bare LiNi1/3Co1/3Mn1/3O2 electrodes displayed clear capacity fading during the charge-discharge cycles under the high voltage charge conditions. On the other hand, LiNi1/3Co1/3Mn1/3O2 coated by Al oxides of 0.5 w/o showed enhanced cycleability even in charge cutoff voltages of 4.5 and 4.6 V, while capacity fading of the Al coated LiNi1/3Co1/3Mn1/3O2was not negligible in charge cutoff voltage of 4.7 V. AC impedance analysis showed that capacity fading of LiNi1/3Co1/3Mn1/3O2 was attributed to increases of polarization resistance of LiNi1/3Co1/3Mn1/3O2 electrodes. Since crystal structure deformation was observed at the surface of degraded LiNi1/3Co1/3Mn1/3O2 particles by s-TEM/EELS, increase of polarization is thought to be attributed to this crystal structure deformation. Al oxides coating effects on the crystal structure deformation at the surface of LiNi1/3Co1/3Mn1/3O2will be discussed in comparison with Zr oxides coating effects. Acknowledgements This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) project of NEDO, Japan. References 1) L. A. Riley et al., J. Power Sources, 196, 3317 (2011). 2) J. Y. Shi et al., J. Power Sources, 195, 6860 (2010). 3) S.-U. Woo et al., J. Electrochem. Soc., 154, A1005 (2007). 4) K. Araki et al., J. Power Sources, to be submitted.

An asymmetric amide anion, FTA− {[(FSO2)(CF3SO2)N]−}, has a significant ability to reduce the melting points of an aliphatic quaternary ammonium salts even for a symmetric tetraethylammonium. Much ...

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A series of new hydrophobic ionic liquids comprising N-alkyl(alkyl ether)-N-methylpyrrolidinium and perfluoroethyltrifluoroborate were prepared and characterized. The new [C2F5BF3]−-based salts sho...

New hydrophobic ionic liquids, 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, n-propyl, n-butyl, n-hexyl) trifluoromethyltrifluoroborate ([CF3BF3]−), have been synthesized by a metathesis reac...

The new compounds Li(2-x)Na(x)Ni[PO(4)]F (x = 0.7, 1, and 2) have been synthesized by a solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data. Li(1.3)Na(0.7)Ni[PO(4)]F crystallizes with the orthorhombic Li(2)Ni[PO(4)]F structure, space group Pnma, a = 10.7874(3), b = 6.2196(5), c = 11.1780(4) Å and Z = 8, LiNaNi[PO(4)]F crystallizes with a monoclinic pseudomerohedrally twinned structure, space group P2(1)/c, a = 6.772(4), b = 11.154(6), c = 5.021(3) Å, β = 90° and Z = 4, and Na(2)Ni[PO(4)]F crystallizes with a monoclinic twinned structure, space group P2(1)/c, a = 13.4581(8), b = 5.1991(3), c = 13.6978(16) Å, β = 120.58(1)° and Z = 8. For x = 0.7 and 1, the structures contain NiFO(3) chains made up of edge-sharing NiO(4)F(2) octahedra, whereas for x = 2 the chains are formed of dimer units (face-sharing octahedra) sharing corners. These chains are interlinked by PO(4) tetrahedra forming a 3D framework for x = 0.7 and different Ni[PO(4)]F layers for x = 1 and 2. A sodium/lithium disorder over three atomic positions is observed in Li(1.3)Na(0.7)Ni[PO(4)]F structure, whereas the alkali metal atoms are well ordered in between the layers in the LiNaNi[PO(4)]F and Na(2)Ni[PO(4)]F structures, which makes both compounds of great interest as potential positive electrodes for sodium cells.