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The surfaces of LiCoO 2 particles were modified to improve the charge-discharge cycling properties of Li-ion batteries containing LiCoO 2 cathodes. The sol-gel technique was used to modify the surface of LiCoO 2 particles with magnesium oxide. Capacity retention during cycling of the magnesium oxide-coated LiCoO 2 cathode was superior to that of a cathode comprising pristine LiCoO 2 . Moreover, results obtained from TEM measurements indicate that the Li concentration was relatively homogeneous in the magnesium oxide-coated LiCoO 2 particles after cycling tests. The crystallographic planes of the coating were found to be coherently oriented with those of the substrate, MgO(111)[1−10]//LiCoO 2 (003)[100]. Therefore, we believe that a thin cover of Mg on the surface of LiCoO 2 stabilizes the surface, contributing to the homogeneity of charge and discharge reactions.

LiNi 1/3 Co 1/3 Mn 1/3 O 2 particles were coated with Al 2 O 3 nanoparticles by means of a mechanochemical bonding process; SEM confirmed that the Al 2 O 3 particles were uniformly coated over the surface of the LiNi 1/3 Co 1/3 Mn 1/3 O 2 powder. During subsequent electrochemical testing using pouch cells, uncoated LiNi 1/3 Co 1/3 Mn 1/3 O 2 exhibited a gradual capacity fading and an increase in area specific impedance (ASI) at a 50% state of charge. Under the same conditions, the increase in ASI of the Al 2 O 3 modified samples was significantly suppressed, although the initial performance (charge/discharge capacity and ASI) slightly deteriorated. The Al 2 O 3 coating was also effective in improving the cyclability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 at elevated temperatures by reducing the extent of cracking.

Composite electrodes composed of amorphous titanium polysulfide (a-TiSx) and titanium disulfide (TiS2) were designed for application in all-solid-state batteries. The conductivity of the a-TiSx/TiS2-based working electrode was higher than that of the amorphous TiS4 (a-TiS4); the reversible capacity of the cell using a-TiSx/TiS2 electrode was higher than that of the cell using a-TiS4. Designing nanocomposite materials such as the a-TiSx/TiS2 described in this paper is an effective way to improve the performance of all-solid-state batteries.

Graphite–solid electrolyte (SE) composite anode, prepared by spark-plasma-sintering (SPS) process, was applied to all-solid-state lithium secondary batteries with lithium sulfide (Li 2 S) positive electrode. The electrochemical tests demonstrated that the graphite–SE/Li 2 S cells showed the discharge capacity of ca . 750 mAh·g − 1 -Li 2 S with the average voltage of ca . 1.98 V. Although the discharge capacity was lower than that of the In/Li 2 S cells ( ca . 920 mAh·g − 1 -Li 2 S), the estimated energy density was higher than that ( ca . 1490 and 1220 mWh·g − 1 -Li 2 S for graphite–SE/Li 2 S and In/Li 2 S cells, respectively), due mainly to its higher average voltage. The graphite–SE/Li 2 S cells showed improved rate capability as compared with the cells with the graphite + SE blended powder, which was attributable mainly to the reduced interfacial resistance between the graphite and SE particles caused by the SPS process.

40%-titanium substituted Li 2 MnO 3 (Li 1+ x (Ti 0.4 Mn 0.6 ) 1− x O 2 , 0 x L -edge energy-loss near-edge structure (ELNES). The morphology change of a primary particle was observed around the Mn reduction phase.

Non-graphitizable carbon (hard carbon) as a negative electrode material for lithium-ion batteries is investigated by X-ray photoelectron spectroscopy, and hard X-ray photoelectron spectroscopy (HX-PES). HX-PES spectra have peaks of both the solid electrolyte interphase on the hard carbon surface and the hard carbon itself. The change in spectrum with state of charge is observed by HX-PES. Hard carbon has two types of lithium insertion site; between graphene sheets and into nano-scale voids. These spectroscopic results are consistent with the lithium insertion mechanism into hard carbon.

Composite electrodes based on amorphous titanium polysulfide and acetylene black were mechanically prepared, and their performance was investigated. The amorphous TiS4 and acetylene black composites were discharged and charged with a high reversible capacity of 563 mAh g−1 in the 1.9–3.0 voltage range. The Coulombic efficiency of the composite was higher than that of a sulfur electrode because the dissolution of the polysulfide into electrolytes was suppressed. Amorphization and dispersion of carbon inside the particles were effective in improving the performance of the titanium polysulfide electrodes. Keywords: Lithium batteries, Titanium sulfide, Polysulfide, Lithium–sulfur batteries

Li 1.20 − y Ni 0.17 Co 0.10 Mn 0.53 O 2 ( y = 0.1–0.93) were prepared electrochemically and characterized using synchrotron XRD and XAFS measurements. Structural analysis using XRD data demonstrated that the lattice parameters of Li 1.20 Ni 0.17 Co 0.10 Mn 0.53 O 2 are a = 0.285214(7) nm and c = 1.42173(3) nm and that the chemical composition can be expressed referring to the Wyckoff positions 3 a and 3 b as [Li 0.988 Ni 0.012 ] 3 a [Li 0.212 Ni 0.158 Mn 0.53 Co 0.10 ] 3 b O 2 . The M ( M = Ni, Co, and Mn) K and L-edge XAFS results suggested that the Li de-intercalation from Li 1.20 Ni 0.17 Co 0.10 Mn 0.53 O 2 proceeded mainly by the oxidation of Ni and Co ions up to y = 0.4 and then by the removal from oxygen from the lattice up to y = 0.93. On the other hand, the O K-edge XANES results indicated no increase in Li 2 CO 3 or Li 2 O on the surface of the positive electrode materials with Li de-intercalation. These results demonstrate that the XAFS method using a combination of soft and hard X-ray is effective way of clarifying the Li de-intercalation/intercalation of the positive electrode materials.

Layered oxides, ruthenium-substituted Li 2 MnO 3 , were synthesized at 800 °C and 1200 °C. Their phase relation and electrical and electrochemical properties were investigated. Li 2 Mn 1− x Ru x O 3 synthesized at 800 °C clearly separated into two phases, manganese-rich and ruthenium-rich phases, except for the narrow composition range of 0 ≤ x ≤ 0.05, while Li 2 Mn 1− x Ru x O 3 synthesized at 1200 °C formed two solid solutions in the whole composition range across a structural transition between x = 0.6 and 0.8. The electrical resistivity of Li 2 Mn 1− x Ru x O 3 decreased with increasing ruthenium content. Li 2 Mn 0.2 Ru 0.8 O 3 ( x = 0.8) synthesized at 1200 °C showed the lowest resistivity of 5.7 × 10 2 Ω cm at room temperature. The discharge capacity and cycling performance were improved by the ruthenium substitution. Li 2 Mn 0.4 Ru 0.6 O 3 ( x = 0.6) exhibited a discharge capacity of 192 mAh g −1 in the initial cycle and 169 mAh g −1 in the tenth cycle with high and almost constant charge–discharge efficiencies of 99% from the second to tenth cycle at a current rate of 1/10 C . The ruthenium substitution to Li 2 MnO 3 is quite effective to improve electrical conductivity and charge–discharge performance.

Equal amounts of Fe- and Ni-substituted Li2MnO3 (chemical formula: Li1+x[(Fe1/2Ni1/2)yMn1−y]1−xO2, 0 F m 3 ¯ m ). Electrochemical characterization as a positive electrode shows that the Li2O extraction region disappears above y = 0.6 on initial charging and that the energy density is decreased drastically above the composition on initial discharging. The optimized transition metal ratios are y = 0.4 and 0.5 because the initial average discharge voltage increases with y and the maximum initial cycle efficiency is attained. In the optimized composition, the Fe- and Ni-substituted Li2MnO3 is a 3.5 V class positive electrode, with similar charge and discharge profiles to those of the most attractive active material, NMC positive electrode (chemical formula: Li1+x[(Co1/2Ni1/2)yMn1−y]1−xO2, 0

Electrochemically active lithium sulfide–carbon (Li2S–C) composite positive electrodes, applicable for rechargeable lithium-ion batteries, were prepared using spark-plasma-sintering (SPS) process. The electrochemical tests demonstrated that the SPS-treated Li2S–C composites showed the initial charge and discharge capacities of ca. 1200 and 200 mAh g−1, respectively, though Li2S has been reported to show no significant charge capacities when conventionally mixed with carbon powder. Such activation of Li2S was attributed principally to strong bindings between Li2S and carbon powders, formed by the SPS treatment. The ex situ XRD measurements showed that some amounts of Li2S were still remained unchanged and any elemental sulfur was not detected even at fully charged state, which was similar to Li/S cells.

Fe-substituted Li2MnO3 including a monoclinic layered rock-salt structure (C2/m), (Li1+x(FeyMn1−y)1−xO2, 0 F m 3 ¯ m ) and monoclinic ones at high Fe content above 30% (y ≥ 0.3), while the sample was assigned as a monoclinic phase (C2/m) at low Fe content less than 20%. In the monoclinic Li2MnO3-type structure, the Fe ion tends to substitute a Li (2b) site, which corresponds to a center position of Mn4+ hexagonal network in Mn–Li layer. The electrochemical properties including discharge characteristics under high current density (

Cylindrical lithium-ion cells with a lithium–nickel–cobalt–aluminum oxide (LiNi0.8Co0.15Al0.05O2) and a non-graphitizable carbon (hard carbon) as the positive and negative electrodes, respectively, were degraded by the storage tests with 50% state-of-charge (SOC). The degraded cells were disassembled and positive electrodes obtained were examined. The cation distribution of lithium and nickel in the positive electrode was clarified using neutron and synchrotron X-ray diffraction measurements. The degree of lithium and nickel disordering varied with the storage condition. X-ray absorption near-edge structure (XANES) analysis demonstrated that the structural change was mainly located near the surface of the positive electrode and the valence state of Ni and Co ions did not change with the storage test. The disordering of the cations near the surface was closely related to the power fade of the cell. The storage condition is an important factor in the power fade of lithium-ion cells.

Layered lithium cobalt oxide (LiCoO2) cathode films were successfully deposited onto an aluminum substrate with a large surface area by electrostatic spray deposition (ESD). Highly porous films were prepared by ESD using cobalt acetate tetrahydrate (CoOAc) and lithium hydroxide monohydrate (LiOH) dissolved ethyl alcohol (15 vol.%) and di(ethylene glycol)butyl ether (85 vol.%) as a precursor solution. An LiCoO2 film, the crystal structure of which contained a combination of layered and spinel regions, was synthesized by heat treatment for 2 h at 400 °C. Charge–discharge curves showed that the capacity of this film was 120 mAh g−1. Heat treatment at 650 °C was shown to be a low enough temperature for the resulting film to be used with an aluminum substrate and to allow the retention of the morphology of the surface on which the film is deposited. The discharge capacity for the layered LiCoO2 region of this film was 140 mA g−1 at a rate of 1C and it achieved a good cycle and a rate performance without the need for auxiliary materials.

Inorganic compounds on the surfaces of the cathode materials LiNi 0.80 Co 0.15 Al 0.05 O 2 and LiCoO 2 were studied using Li and 0 K-edge X-ray absorption near edge structure (XANES) measurements. Rietveld analysis revealed that the LiNi 0.80 Co 0.15 Al 0.05 O 2 sample contained 2% Li 2 CO 3 , while the LiCoO 2 sample was single-phase. The Li and O K-edge XANES spectra indicated that the surface of LiCoO 2 was almost free of residual Li 2 CO 3 . In contrast, the presence of both residual Li 2 CO 3 and an additional cubic phase were observed, respectively, on and near the surface of LiNi 0.80 Co 0.15 Al 0.05 O 2 . These results demonstrate that the XANES technique, using a combination of the total electron yield and fluorescence methods, is an effective tool for probing the surfaces of cathode materials.

Novel electrolyte materials, room temperature ionic liquids (RTILs) were applied to the Li battery system and their characteristics in Li-metal batteries are discussed, partly reviewing authors work in the past. Quaternary ammonium (QA) cation-imide RTIL was focused on because of the excellent stability in cathodic environment of Li. Li/LiCoO2 cell performance and Li cycling efficiency using the selected QA-imide RTIL was almost satisfactory. In addition, thermal stability of selected QA-imide RTIL with the charged positive electrode and Li was the advantage for Li battery. On the other hand, further improvement in the conducting properties is required with balanced approach for both electrochemical stability and thermal stability in order to use the RTIL electrolyte practically in batteries.

The specific capacity of Li 0.44 Mn 1− y Ti y O 2 (0 y 3 –LiOH salt at a low temperature. High-purity specimens of the lithium-inserted Li 0.44+ x Mn 1− y Ti y O 2 have been successfully prepared. We have conducted a systematic experimental study of the structural and electrochemical properties of these compounds. The inserted lithium content, x , in Li 0.44+ x Mn 1− y Ti y O 2 increases together with the substituted Ti content, y . The initial charge capacity increases from 130 mAh g −1 ( y = 0) to 145 mAh g −1 ( y = 0.22) for the Li 0.44+ x Mn 1− y Ti y O 2 compounds. The maximum discharge capacity that has been achieved is 180 mAh g −1 in the case of Li 0.72 Mn 0.78 Ti 0.22 O 2 between 2.5 and 4.8 V with a fixed current density of 30 mA g −1 ( C /6) at 30 °C. The discharge capacity at the 4 V plateau region (about 100 mAh g −1 ) in the lithium-inserted Li 0.55 MnO 2 has been improved to twice that in as-prepared Li 0.44 MnO 2 (about 50 mAh g −1 ). The structural differences between Li 0.44 MnO 2 and Li 0.55 MnO 2 are discussed based on XRD Rietveld analysis results.

X-ray photoemission spectroscopic and high-resolution hard X-ray photoemission spectroscopic studies of positive electrodes in LiNi0.73Co0.17Al0.10O2 and hard carbon based batteries were carried out to elucidate the mechanism of battery degradation. Li2CO3, hydrocarbons, ROCO2Li, polycarbonate-type compounds and LiF were observed on positive electrode surfaces and the amount of carbonates was found to have increased after cycle testing. Above 60 °C, signs of electrolyte decomposition were indicated. Near the surface of the positive electrodes, a Li-deficient cubic phase is present and grows with degradation. Capacity and power fade could be related to the amount of species on the surface and the thickness of the Li-deficient cubic phase near the surface.

A mixture of flammable organic solvent and nonflammable room temperature ionic liquid (RTIL) has been investigated as a new concept electrolyte to improve the safety of lithium-ion cells. This study focused on the use of N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide (PP13-TFSI) as the RTIL for the flame-retardant additive. It was found that a carbon negative electrode, both graphite and hard carbon, could be used with the mixed electrolyte. A 383562-size lithium-ion trial cell made with the mixed electrolyte showed good discharge capacity, which was equivalent to a cell with conventional organic electrolyte up to a discharge current rate of complete discharge in 1 h. Moreover, the mixed electrolyte was observed to be nonflammable at ionic liquid contents of 40 mass% or more. Thus the mixed electrolyte was found to realize both nonflammability and the good discharge performance of lithium-ion cells with carbon negative electrodes. These results indicate that RTILs have potential as a flame-retardant additive for the organic electrolytes used in lithium-ion cells.

Cylindrical lithium-ion (Li-ion) cells with a nickel-cobalt oxide (LiNi0.73Co0.17Al0.10O2) positive electrode and a non-graphitizable carbon (hard carbon) negative electrode were degraded using cycle tests. The degraded cells were disassembled and examined; most attention was paid to the positive electrodes in order to clarify the origin of the power fade of the cells. X-ray absorption near-edge structure (XANES) analysis demonstrated that the crystal structure of the electrode at the surface changed from rhombohedral to cubic symmetry. Furthermore, a film of lithium carbonate (Li2CO3) covered the surface of the positive electrode after the cycle tests. Using a combination of X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and glow discharge optical emission spectrometry (GD-OES) measurements, a schematic model of the changes occurring in the surface structure of the positive electrode during the cycle tests was constructed. The appearance of both an electrochemically inactive cubic phase and lithium carbonate films at the surface of the positive electrode are important factors giving rise to power fade of the positive electrode.

Fe-substituted Li2MnO3 (Li1+x(FeyMn1−y)1−xO2, 0 ≤ x ≤ 1/3, 0.3 ≤ y ≤ 0.7) was synthesized using a combination of coprecipitation, hydrothermal, and heat-treatment methods. It exhibits high initial specific capacity greater than 200 mAh g−1 and small capacity, which fades up to the 50th cycle (>150 mAh g−1 at the 50th cycle) under electrochemical cycle testing at 60 °C. The attractive electrode properties appeared by controlling the chemical composition (x > 0.05, 0.3 ≤ y ≤ 0.5) and high specific surface area (>20 m2 g−1). The Fe-substituted Li2MnO3 is an attractive candidate as a novel 3 V-class positive electrode material.

Li1−yNi0.45Mn0.45Al0.1O2 was synthesized and characterized using both XRD and XANES measurements. The Li/Li1−yNi0.45Mn0.45Al0.1O2 cell showed a discharge capacity of 125 mAh/g in the voltage range 4.5–2.5 V. The Ni K and LII,III-edge XANES results indicated that the Li de-intercalation from LiNi0.45Mn0.45Al0.1O2 proceeded mainly by the valence state change of Ni ions over the whole composition range. Structural analysis clarified that most of the Li ions and a small fraction of the Ni ions migrated from the octahedral 3a site to the tetrahedral 6c site with Li de-intercalation. This observed structural change was similar to that of Li1−yNi0.5Mn0.5O2, indicating that this structural change is characteristic in the Li(NiMn)O2 system.

We present electrochemical properties of lithium alanate (LiAlH4) dissolved in aprotic ethers – diethyl ether (Et2O) and tetrahydrofuran (THF) – under an Ar atmosphere of 1 atm at 298 K. Specific conductivities of both LiAlH4–THF and LiAlH4–Et2O solutions are measured by AC four-terminal method. Cyclic voltammetry is performed with using a beaker-type electrochemical cell consisted of a Ni wire, Ni mesh and Li wire as a working, counter and reference electrode, respectively. In order to clarify the electrochemical behavior, anodic polarization of LiAlH4–THF solution is measured. The current density of 1.0 M LiAlH4–THF solution reaches to 1 A cm−2, which is higher than the LiAlH4–Et2O solution. Quantitative analysis of H2 gas generated on the working electrode during the potentiostatic electrolysis tells that the number of electrons involved in the anodic reaction at the limiting current is one in case of the LiAlH4–THF solution. We propose conceivable electrochemical reactions of LiAlH4 in the non-aqueous ethereal solutions.

A charge–discharge cycling test of a Li/LiCoO 2 cell containing ionic liquids based on bis(fluorosulfonyl)imide ([FSI] − ) as the electrolyte media, revealed significantly better rate properties compared to those of cells using conventional ionic liquids. The use of an 1-ethyl-3-methylimidazolium (EMI + ) salt permitted the retention of 70% of the discharge capacity at a 4 C current rate. In contrast, similar performance of cells containing N -methyl- N -propylpyrrolidinium (Py 13 + ) and N -methyl- N -propylpiperidinium (PP 13 + ) salts of [FSI] − was limited to operation at 2 and 1 C current rates, respectively. However, the charge/discharge cycling stability of the cell with Py 13 [FSI] was much better than that of the cell using EMI[FSI].

The specific capacity of Fe-substituted Li 2 MnO 3 (Li 1.2 Fe 0.4 Mn 0.4 O 2 ) was improved by adjusting the preparation temperature of Fe–Mn co-precipitate below RT in order to suppress the spinel ferrite formation, which hinders the formation of homogeneous and reactive precursor. The degradation of discharge capacity with cycle could be suppressed by nominal 5% Al, Ni and Co doping. This means that Fe-substituted Li 2 MnO 3 will be considered to be one of the near future positive electrodes for practical use by careful optimization of its preparation condition and chemical composition.

LiMn 2 O 4 films with vertically aligned holes were formed by electrostatic spray deposition (ESD) and subsequent annealing. Different surface morphologies, such as dense grains, 1 μm-diameter pores with 1 μm-thick walls, and 5 μm pores with 3 μm walls, were formed by varying the lithium sources in the precursor solution. The randomly oriented pores in the films prepared using ESD were rearranged in vertical stacks after annealing to produce crystalline LiMn 2 O 4 . This process would be suitable for constructing three-dimensional interfaces between active materials and solid-state electrolytes.

The properties of the Li/LiCoO 2 cell containing several RTILs with three different anions were investigated. Introducing the asymmetric nature to anionic species using amide improved the viscosity and conductivity of the RTIL, however, the rate properties of the cell was not enhanced very much. Declined cathodic stability seems to be responsible for the result. In the case of the stable system consisting of quaternary ammonium cation and imide anion, both of cycling properties and Coulombic efficiency during the cycling were satisfactory and the viscosity dominated the rate properties of the cell. The performance of the Li/LiCoO 2 cell in this study was almost consistent with the stability of Li-electrolyte interface evaluated by ac impedance measurement.

The physical and electrochemical properties of room temperature ionic liquids (RTILs) based on asymmetric amide anions (TSAC: 2,2,2-trifluoro- N -(trifluoromethylsulfonyl)acetamide, C1C2: N -(trifluoromethylsulfonyl)pentafluoroethylsulfonamide) and aliphatic onium cations, such as ammonium, phosphonium, and sulfonium, were reported. The melting point of the C1C2 salts decreased compared to the corresponding TFSI salts (TFSI: bis(trifluoromethylsulfonyl)imide), however, the viscosity was about twice that of the TFSI salts. Relatively low viscosity RTILs based on aliphatic onium cations could be prepared using the TSAC anion and tetraalkylammonium cation containing an alkoxy group. The linear sweep voltammogram of these RTILs with and without Li-TFSI were investigated in order to estimate the electrochemical windows and possible use as a lithium battery electrolyte.

Composite positive electrodes LiFePO 4 /C, applicable for rechargeable lithium-ion batteries cycled at high current density, were prepared using spark-plasma-sintering (SPS) technique. LiFePO 4 /C composite positive electrodes with carbon content of 20 wt.% was synthesized at 600 °C in the SPS process, and it was found that LiFePO 4 particles were covered with fine carbon particles and they formed agglomerates with the size of about 10 μm. It resulted in higher electrode density. Charge/discharge tests for the cell using LiFePO 4 /C composite positive electrodes showed superior cycle performance at the rates of 17–850 mAh g −1 (0.1–5 C) compared with the cell using the conventionally blended LiFePO 4 + C composite positive electrodes. The improvement of the cell performance was attributed to strong binding between LiFePO 4 and carbon powders. Consequently, the electrical network remained almost unchanged during electrochemical redox cycling, even at high current rates.

Structural changes in Li 1− y Ni 0.5 Mn 0.5 O 2 with Li de-intercalation were studied using X-ray diffraction, XAFS, and magnetic measurements. The Li de-intercalation from LiNi 0.5 Mn 0.5 O 2 proceed mainly by a valence state change of Ni ions from Ni 2+ to Ni 3+ up to y =0.5 from the XANES and magnetic results. Structural analysis clarified that a second order phase transition from trigonal to monoclinic was observed between y =0.2 and 0.3 and that a small fraction of the Li ions start to migrate from the octahedral 2 a site to the tetrahedral 4 i site at y =0.3 and most of the Li ions occupied the tetrahedral 4 i site at y =0.5 with Li de-intercalation. The EXAFS analysis clarified the valence state change and the range of phase transition during the Li de-intercalation, from the changes in the bond distance of the first neighbor for each transition metal. This Li de-intercalation mechanism is characteristic of this system and has not been reported for Li 1− y MO 2 (M=Co and Ni).

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.

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.

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.

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.

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.

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.

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

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.

Stage 2 FeCl3-graphite intercalation compound (GIC) was chemically reduced with lithium-naphthalene complex in THF and 1-MB. The GIC was also reduced electrochemically in THF, PC and EC+DEC, containing 1 mol/dm3 of LiClO4. When the reduction was performed in THF chemically or electrochemically, fine iron particles were obtained in the graphite matrix. The mean diameter of the particles is in the range of 11-13nm in this case, while 4nm for 1-MB. For PC and EC+DEC, no iron particle was observed in the product. The difference would be related to the co-intercalation of the solvent. In the reduction process, THF is incorporated together with lithium in the interlayer spacing of FeCl3-GIC. The co-intercalated THF molecules facilitate the reduction of FeCl3 by lithium in the graphite gallery probably because FeCl3 is soluble in THF, and relatively large iron particles are obtained.