Charge-discharge Characteristics Research Articles

Spectroscopic analyses of 0.5Li[Ni 0.8Co 0.15Zr 0.05]O 2–0.5Li[Li 1/3Mn 2/3]O 2 composite cathodes for lithium rechargeable batteries

In this work we have investigated the lithium ion intercalation behavior in wet chemical synthesized 0.5Li[Ni 0.8Co 0.15Zr 0.05]O 2–0.5Li[Li 1/3Mn 2/3]O 2 composite cathodes. Impedance spectroscopy in conjunction with micro-Raman spectroscopy and X-ray photoelectron spectroscopy measurements are performed to understand the lithium ion intercalation behavior in these composite cathodes. The Rietveld refinement of the X-ray diffractograms of the cathode powder indicates a hexagonal layered structure and minimal transitional metal cation disorder between lithium and (transition) metal layers. Probing the localized region by micro-Raman spectroscopy, it is found that in virgin cathode, monoclinic Li[Li 1/3Mn 2/3]O 2 forms composite with hexagonal layered Li[Ni 0.8Co 0.15Zr 0.05]O 2 component. Interestingly, these cathodes transform into a hexagonal layered structure upon charging ∼ 4.8 V. The galvanostatic charge–discharge characteristics of these composite cathode is reported in the cut-off voltage limits of 4.8–1.45 V. Detailed X-ray photoelectron spectroscopy analyses of the valence states of the constituent elements are performed in virgin, fully charged and partial discharged states of the cathodes. Through the XPS analyses, the charge and discharge capacities of these cathodes are found to be due to Ni 3+/Ni 4+, Co 3+/Co 4+ and Ni 2+/Ni 3+ redox couples. The capacity of these composite cathodes is deteriorated when cycled repeatedly between the voltage limits of 4.8–1.45 V. The probable reasons for such findings are discussed.

Charge-discharge Behaviors of Coin-type Air Rechargeable Batteries Using Hydrogen Storage Alloy

Coin-type of air secondary batteries using hydrogen storage alloys as the negative electrode’s material were designed and fabricated, and the charge-discharge characteristics were evaluated under constant current operation. The positive electrode consisted of a nickel-based gas diffusion electrode using Ir2Bi2O7−z as oxygen evolution and reduction catalyst. A stable charge and discharge voltages were observed, and the discharge voltage and power density were improved by using a membrane separator, in which an alkaline solution was impregnated, between the positive and negative electrodes. A high power density up to 81 W dm−3 and a good charge-discharge cycling behaviors were also obtained.

Physical and Electrolytic Properties of Partially Fluorinated Methyl Propyl Carbonate and Its Application to Lithium Batteries

The physical and electrolytic properties, and charge-discharge characteristics for secondary lithium batteries of partially fluorinated methyl propyl carbonate (MPC) derivatives were examined. Dielectric constants of the fluorinated MPC derivatives except 2,2,3,3,3-pentafluoropropyl methyl carbonate (PFPMC) tend to increase with increasing the number of fluorine atom. Viscosity of PFPMC with the highest molar volume is lower than those of other fluorinated MPC derivatives. Donor numbers (DN) of the fluorinated MPC derivatives were estimated by 29Si NMR chemical shifts of triphenylsilanol. DN of the fluorinated MPC derivatives except PFPMC tends to decrease with increasing the number of fluorine atom. 3-Fluoropropyl methyl carbonate (FPMC) shows the highest specific conductivity at the temperature above about 25°C. Oxidative decomposition potentials of the fluorinated MPC derivatives tend to increase with increasing the number of fluorine atom. PC-FPMC electrolyte shows higher lithium electrode cycling efficiency. Every PC-based fluorinated MPC derivative electrolyte shows higher discharge capacities for Li|LiCoO2 cells.

Charge–discharge characteristics of a layered-structure electroplated Cu/Sn anode for Li-ion batteries

An electroplated copper/tin (Cu/Sn) anode with a layered structure is described that minimizes the high-voltage irreversible capacity observed in an electroplated Sn anode at a potential over 1 V. The high-voltage irreversible capacity is caused by the electrolyte decomposition at the catalytic site of the Sn anode. In the electroplated Cu/Sn anode, the upper Cu layer effectively suppresses the exposure of the newly formed Sn surfaces, resulting in the absence of the high-voltage irreversible capacity. Therefore, the electroplated Cu/Sn anode exhibits a higher cycle performance than the electroplated Sn anode.

ZnO particles of wurtzite structure as a component in ZnO/carbon nanotubecomposite

Composites based on carbon nanotubes and ZnO particles with needle shapes wereprepared for applications in energy storage. Depending on the temperature (85 or25 °C) at which the reactionbetween NaOH and ZnCl2 was carried out, particles with two different morphologies: needle-shaped (NS) anddouble-pyramid-shaped (DPS), respectively, are obtained. Scanning electron microscopy,photoluminescence, UV–Vis absorption spectroscopy, x-ray diffraction and Raman light scatteringstudies reveal that the NS and DPS particles belong to ZnO with wurtzite (WZ) structure andε-Zn(OH)2 as precursors of ZnO, respectively. Using the ZnO/carbon nanotubecomposite as a negative electrode and an electrolytic solution containingLiPF6, the charge–discharge characteristics of rechargeable lithium ions cells were determined.Additional information concerning the electrochemical reactions at the interface of the twoelectrodes was obtained by cyclic voltammetry.

Non-aqueous vanadium acetylacetonate electrolyte for redox flow batteries

The electrochemistry of a single-component redox flow battery employing vanadium(III) acetylacetonate in acetonitrile and tetraethylammonium tetrafluoroborate has been investigated. The electrode kinetics of the anodic and cathodic reactions were studied using cyclic voltammetry. The V(II)/V(III) and V(III)/V(IV) couples were quasi-reversible and together yielded a cell potential of 2.2 V. The diffusion coefficient for vanadium acetylacetonate was estimated to be in the range of 1.8–2.9 × 10 −6 cm 2 s −1 at room temperature. The charge–discharge characteristics of this system were evaluated in an H-type glass cell, and coulombic efficiencies near 50% were achieved.

Surface Enhanced Raman Scattering Studies on Poly(3,4-ethylene dioxythiophene)/Single-Walled Carbon Nanotubes Composites and Their Application to Rechargeable Lithium Batteries

In this paper, surface enhanced Raman scattering (SERS) studies on the chemical polymerization of 3,4-ethylene dioxythiophene (EDOT) in the presence of single-walled carbon nanotubes (SWNTs) are reported. Both a non-covalent and covalent functionalization of SWNTs with poly(3,4-ethylene dioxythiophene) (PEDOT) is invoked as a result of the following variations induced in the SERS spectra of PEDOT and SWNTs: (i) the appearance of a Raman line at 140 cm(-1) indicating the formation of a new covalent bond between PEDOT and SWNTs; (ii) an increase in the intensity of the Raman line at 705 cm(-1), associated with the deformation vibration mode of C-S-C bond, the result of a steric hindrance effect induced by the bonding of PEDOT on SWNTs; and (iii) the enhancement of the Raman band with maximum at 1540 cm(-1) (G- component) in SWNTs when the PEDOT weight in the PEDOT/SWNTs composite increases. Using the PEDOT/SWNTs composite as a positive electrode and an electrolytic solution containing LiPF6, the charge-discharge characteristics of the rechargeable lithium cells are determined. High specific discharge capacity are reported for the PEDOT/SWNTs composite (ca. 218 mAh g(-1)) in comparison with PEDOT doped with FeCl4- ions (ca. 25 mAh g(-1)).

Effect of electrochemical conditions on the performance worsening of Si/C composite anodes for lithium batteries

An effective and practical method for producing Si/C composites with 10–15 wt% of silicon nanoparticles embedded in a carbon matrix is developed. The procedure consists of mechanically mixing Si with pitch followed by dispersing in toluene and final heat-treatment between 1000 and 1100 °C. The homogeneity of the materials was confirmed by optical microscopy and HRTEM. X-ray photoelectron spectroscopy, X-ray diffraction and N2 adsorption at 77 K were applied for determining the structural and textural characteristics. The lithium insertion/deinsertion performance was monitored from the galvanostatic charge–discharge characteristics using a Si/C–lithium two-electrode cell, and varying the electrochemical parameters. Silicon essentially enhances the electrode capacity (Crev up to 600 mAh/g for 15% Si), the effect being proportional to the component content, but it affects the cycle life. The first cycle reversible capacity increases with the decrease of current density and discharge cut-off potential. However, using such conditions during cycling leads to rapid saturation of the silicon particles, from which the decay of the electrochemical performance starts. It is demonstrated that the evolution of reversible and irreversible capacity is strongly dependent on the kinetics of lithium diffusion in silicon particles and on the discharge potential cut-off.

Preparation of LiFe PO4Using Chitosan and its Cathodic Properties for Rechargeable Li-ion Batteries

The LiFeP<TEX>$O_4$</TEX> powder was synthesized by using the solid state reaction method with Fe(<TEX>$C_2O_4){\cdot}2H_2O,\;(NH_4)_2HPO_4,\;Li_2CO_3$</TEX>, and chitosan as a carbon precursor material for a cathode of a lithium-ion battery. The chitosan added LiFePO4 powder was calcined at 350 <TEX>${^{\circ}C}$</TEX> for 5 hours and then 800 <TEX>${^{\circ}C}$</TEX> for 12 hours for the calcination. Then we calcined again at 800 <TEX>${^{\circ}C}$</TEX> for 12 hours. We characterized the synthesized compounds via the crystallinity, the valence states of iron ions, and their shapes using TGA, XRD, SEM, TEM, and XPS. We found that the synthesized powders were carbon-coated using TEM images and the iron ion is substituted from 3+ to 2+ through XPS measurements. We observed voltage characteristics and initial charge-discharge characteristics according to the C rate in LiFeP<TEX>$O_4$</TEX> batteries. The obtained initial specific capacity of the chitosan added LiFeP<TEX>$O_4$</TEX> powder is 110 mAh/g, which is much larger than that of LiFeP<TEX>$O_4$</TEX> only powder.

Synthesis and characterization of Li 4Ti 5O 12

Lithium titanate, Li 4Ti 5O 12 was prepared by the sol–gel method. The precursor was sintered at various temperatures (700, 800, 900 and 1000 °C) for 1 h and was also sintered at various times from 1 to 5 h at 800 °C. TGA and XRD were used to characterize the prepared samples. From TGA studies it was observed that the thermogram was no longer dependent on temperature from 600 °C onwards. The XRD patterns showed peaks attributable to Li 4Ti 5O 12 phase for all prepared samples. Charge–discharge characteristics of the cells fabricated with the prepared lithium titanate were studied.

All solid-state sheet battery using lithium inorganic solid electrolyte, thio-LISICON

Abstract All solid-state sheet lithium battery was developed using inorganic solid electrolyte, thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S 4 ), Li–Al anode, and Mo 6 S 8 cathode materials, and the sheet manufacturing process was established. The new sheet-configuration was consisted of the cathode with the grid of current collector, electrolyte sheet with or without mechanical support, and aluminum/lithium composite sheet anode. A sheet battery with a dimension of 30 mm × 30 mm showed good charge–discharge characteristics without any capacity fading at a current of 0.1 mA.

Synthesis and Electrochemical Studies of Nano-Scale Carbon-Coated LiFePO&lt;SUB&gt;4&lt;/SUB&gt; Electrodes for Li-Ion Batteries

Regardless of high capacity and stability during lithium extraction, LiFePO4 materials have difficulty in the applications for high electrical density because of low electrical conductivities. In order to optimize this problem, we synthesized carbon coated LiFePO4 by adding humic acid using solid state reaction method. We characterized the synthesized compounds via the crystallinity, the valence states of Fe ions, and their shapes. We found the carbon coating using X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). We also found that the iron ion is substituted from 3+ to 2+ through XPS measurement. We showed that the carbon coating increased the electrochemical behavior by measuring the charge-discharge characteristics.

Improvement of Energy Storage Flywheel System With SMB and PMB and Its Performances

Our group has developed a new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB). The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. The permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of PMB and SMB. Dynamics and charge-discharge characteristics are improved and discussed in this paper.

High voltage spinel cathode materials for high energy density and high rate capability Li ion rechargeable batteries

Abstract We have synthesized LiMn 1.5 Ni 0.4 Cr 0.1 O 4 cathode material for high energy density Li ion rechargeable batteries using sol–gel method. The synthesized materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, cyclic voltammetry and charge–discharge characteristics. It was found that phase pure materials were obtained an annealing temperature of 875 °C for 15 h. The maximum discharge capacity at a constant charge–discharge current rate 1 C , 0.5 C , and 0.2 C were found to be about 99 mAh g −1 , 110 mAh g −1 , and 131 mAh g −1 , respectively. The capacity retentions after 50 charge–discharge cycles were found to be about 99%, 97%, and 97.3% at discharge current rates of 0.2 C , 0.5 C , and 1 C . The stable electrochemical behavior of the above cathode material even at high C rate, showed that it could be used for high energy density and high rate capability Li ion rechargeable batteries.

Electrochemical performances of inorganic membrane coated electrodes for li-ion batteries

In the present study, we prepared new Li-ion batteries with inorganic membrane-coated electrodes fabricated by the direct coating of a 400-nm-sized Al2O3 particles onto the anodes and studied their charge–discharge characteristics for the first time. Being made of 94 wt.% Al2O3 powder and 6 wt.% polymeric binder, the membranes on the anodes showed excellent wettability with the liquid electrolytes, due to their high porosity and capillarity. The Li-ion batteries prepared by the assembly of the inorganic membrane-coated electrodes showed excellent charge–discharge behavior compared to conventional Li-ion batteries with a polymeric separator. However, their high-rate performance was affected by the binder contents in the inorganic membranes. The thermal properties of the Li-ion battery with the inorganic membrane-coated electrodes were compared with those of a conventional one with a polymeric separator.

Physical and Electrolytic Properties of Partially Fluorinated Organic Solvents and Its Application to Secondary Lithium Batteries: Partially Fluorinated Dialkoxyethanes

This paper investigated the physical and electrolytic properties, and charge-discharge characteristics for secondary lithium batteries of partially fluorinated 1-ethoxy-2-methoxyethane (EME) and 1,2-diethoxyethane (DEE) derivatives newly synthesized by us. Dielectric constants of fluorinated EME and DEE derivatives are almost independent of the number of fluorine atom. Viscosities of the fluorinated derivatives with three fluorine atoms are not affected by the molecular weights of them. Donor numbers of the fluorinated derivatives were estimated by 29Si NMR chemical shifts of triphenylsilanol. Conductivities of the fluorinated derivatives are dependent on the donor numbers of them. Oxidative decomposition voltages tend to increase with increasing the number of fluorine atom. EC-based equimolar binary derivative solutions with three fluorine atoms show higher lithium electrode cycling efficiencies. In general, EC-based fluorinated EME and DEE derivative solutions show higher discharge capacities and cycling efficiencies for Li | LiCoO2 cells.

Investigations on 0.5 Li ( Ni0.8Co0.15Zr0.05 ) O2 – 0.5 Li ( Li1 ∕ 3Mn2 ∕ 3 ) O2 Cathode for Li Rechargeable Batteries

In the present work we have reported the electrochemical characteristics of 0.5–0.5 cathodes for lithium rechargeable batteries. In the pristine cathodes the formal oxidation state of Mn ions are , whereas Ni and Co are in the valence state. Rietveld refinement of the powders indicates a hexagonal layered structure (space group ) and minimal cation disorder between lithium and transition-metal layers. Raman analysis confirms the composite nature of pristine cathode laminates which contain (LMO)- and (LNCZO)-rich regions. The galvanostatic charge–discharge characteristic of these composite cathodes is reported in various cutoff voltage limits. When these composite cathodes are charged to , electrochemical extraction of Li takes place from active (LNCZO) as well as inactive (LMO) components. The charge and discharge capacitates of these cathodes are found to be due to , , and redox couples. Reasonably good cyclability of these composite cathodes is obtained when cycled in the cutoff voltage limits of . The cyclability of these composite cathodes are deteriorated when these composite cathodes are charged above and deep discharged up to , followed by repeated cycling in these voltage limits. The probable reasons for such findings are discussed.

Synthesis of γ-CoOOH and its effects on the positive electrodes of nickel batteries

High-valence (3.40) cobalt compounds were synthesized by a chemical precipitation (CP) method. Nickel hydroxide electrodes were then prepared using the synthesized compounds as conducting agents. The effects of high-valence cobalt additions on electrode properties, such as charge–discharge characteristics, electrode reaction reversibility, and cyclic voltammetric performance, were investigated by cyclic voltammetry, X-ray diffraction (XRD), and resistance measurement. The results demonstrate that the addition of high-valence cobalt helps to form a conductive network in the electrode, thus greatly increasing the cycling performance and simultaneously accomplishing an extremely high utilization of the active material in the positive electrode. For comparison, active materials of Co(OH)2, β-CoOOH, and CoO were also included in the test. It was found that cobalt with a valence of 3.40 has a higher performance within one cycle. The utilization of the active material can reach 100.6% at a discharge rate of 0.2 C.

ELECTRICAL DOUBLE LAYER CAPACITOR WITH PROTON CONDUCTING κ-CARRAGEENAN–CHITOSAN ELECTROLYTES

Charge–discharge characteristics of electrical double layer capacitors (EDLCs) using κ-carrageenan–chitosan based electrolyte is the focus of the present work. Chitosan and κ-carrageenan were blended to obtain films with high mechanical strength. The room temperature conductivity of 0.5 g chitosan + 0.5 g κ-carrageenan (CCPA) film and 0.5 g chitosan + 0.5 g κ-carrageenan + 0.1765 g ammonium nitrate (CCPAAN) film are (1.38 ± 0.36) × 10-6 S cm -1 and (2.39 ± 0.83) × 10-4 S cm -1, respectively. The conducting species is H + and conduction occurs via a Grotthuss mechanism. The resistance of the phenol resin based activated carbon electrode film is between 15 to 20 Ω. The capacitance of the EDLCs is stable over 20 cycles. The average discharge capacitance of the EDLC employing CCPAAN electrolyte and activated carbon electrodes is between 13 to 18.5 F g-1.

Electrolytic characteristics of fluoromethyl methyl carbonate for lithium rechargeable batteries

Monofluorinated solvents exert the polar effect on various properties. We have investigated the electrolytic properties of fluoromethyl methyl carbonate (FMMC, monofluorinated dimethyl carbonate) and its application to lithium rechargeable batteries. We describe the dependence of electrolytic conductivity on the temperature, the molar concentrations of three lithium salts, and the molar fractions of the binary solvents. The conductivities of the FMMC solutions were higher than those of the dimethyl carbonate (DMC) counterparts at low concentrations of the lithium salts but lower at high concentrations. The threshold concentration, below which monofluorination evoked the increase in the conductivity, depended on the degree of ionic dissociation of the lithium salt. The anodic stability of FMMC was higher than that of DMC. The deintercalation and intercalation of Li + in a LiCoO 2 cathode proceeded more stably in an ethylene carbonate (EC)–FMMC (molar ratio 1:1) binary solution containing 1 mol dm −3 LiPF 6 than in the EC–DMC counterpart. The cycling efficiency of a lithium anode and the performance of Li/LiCoO 2 coin cells were investigated by using the EC–chain carbonate binary solutions. The use of FMMC as the co-solvent improved the charge–discharge characteristics.