Charge-discharge Characteristics Research Articles

Preparation, characterization and electrochemical property of Sn–Fe–Mo–Al 2O 3 multi-phase composites

A novel technique has been developed to synthesize Sn–Fe–Mo–Al 2O 3, while nanoscale dispersion of a highly active tin phase was finely distributed in a stable inert multi-phase. The precursor was prepared by co-precipitation method with SnCl 4, FeCl 3, AlCl 3 and (NH 4) 6Mo 7O 24 as the raw materials. Sn–Fe–Mo–Al 2O 3 mixture was produced by reducing the precursor with H 2. The product was characterized by X-ray diffraction (XRD), ICP and scanning electron microscopy (SEM). The performance of the electrode was investigated. The Sn–Fe–Mo–Al 2O 3 electrode was found to have an initial charge capacity of over 461 mAh/g, and a reversible volumetric capacity of 2090 mAh/cm 3, which is two times larger than that of graphite electrode (800 mAh/cm 3). The coulomb efficiency in the first cycle was over 55%, but its cyclability was not improved significantly. In order to enhance the cycle performance, we investigated the anode after heat treated at 270 °C for 12 h. Under the same condition, the first charge–discharge characteristics were almost equivalent to the as-coated anode, and the retention capacity ratio after 20 cycles was improved from 41.1% to 86.5%. The heat-treated Sn–Fe–Mo–Al 2O 3 electrode exhibited better cycle life. The electrochemical reaction of the Sn–Fe–Mo–Al 2O 3 electrode with Li may obey the alloying–dealloying mechanism of Li x Sn( x⩽4.4) formation in the other tin-based electrodes.

Vertically aligned double-walled carbon nanotube electrode prepared by transfer methodology for electric double layer capacitor

We successfully prepared a vertically aligned double-walled carbon nanotube (DWCNT) sheet by a transfer procedure from a silicon substrate as a DWCNT seedbed that was covered with catalyst grains to an aluminum sheet as a current collector for application to a high-performance electrode for an electric double layer capacitor (EDLC). The charge–discharge characteristics and EDLC performances of the aligned DWCNT electrode were evaluated and compared with those of a vertically aligned multi-walled CNT (MWCNT) electrode. The gravimetric capacitance of the DWCNT electrode was ca. four times larger than that of the MWCNT electrode. The rate capability of the DWCNT electrode was found to be excellent. This is mainly ascribed to our transfer technique.

Lithium insertion into silicon films produced by magnetron sputtering

Using the method of magnetron-plasma sputtering of polycrystalline silicon target, amorphous silicon films 32–214 nm thick were produced on various (copper and titanium, polished and rough) substrates. A study of their charge-discharge characteristics under the galvanostatic conditions showed that all thin-filmed electrodes are capable of reversible lithium insertion. The amount of lithium inserted in the first cycles is close to the theoretical one. An analysis of composition and morphology of surface layer and also the behavior of reversible and irreversible capacities during cycling showed that the degradation of capacity is caused by the exfoliation of films from the substrate (the effect is more pronounced for the specimens with polished substrates) and somewhat breaking (cracking) of films. The thicker are the films, the severer is the disruption of silicon films in the cycling. The adhesion of films to the substrate surface is favored by the film roughness. At sufficiently high adhesion of films, their electrochemical properties only slightly depend on the nature (copper or titanium) of substrate.

Characteristics of Li0.98Cu0.01FePO4 prepared from improved co-precipitation

Pure lithium iron phosphates and stoichiometric Cu-doped lithium iron phosphates were synthesized via improved co-precipitation, followed by sintering at high temperature for crystallization. The improved co-precipitation process allowed the homogeneous mixing of the ingredient reactants at atomic level. All samples were pure single phase indexed with orthorhombic Pnmb space group. The particle size of the Li 0.98 Cu 0.01 FePO 4 was drastically fine with100–200 nm, compared with the undoped LiFePO 4 . The electrochemical performance of Li 0.98 Cu 0.01 FePO 4 , including reversible capacity, cycle number and charge–discharge characteristics, exhibited better than those of LiFePO 4 .

Electrochemical properties of fluoropropylene carbonate and its application to lithium-ion batteries

We have investigated the monofluorination effect of propylene carbonate (PC) on the electrolytic properties and on the performance of lithium-ion cells. The anodic stability of fluoropropylene carbonate (FPC) is higher than that of PC. The use of FPC as a high-polarity solvent decreases the electrolytic conductivity but improves the charge–discharge characteristics of the lithium-ion cells.

Electrochemical binding and wiring in battery materials

Binders in battery electrodes not only provide mechanical cohesiveness during battery operation but can also affect the electrode properties via the surface modification. Using atomic force microscopy (AFM), we study the surface structuring of three binders: polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC) and gelatin. We try to find correlation between the observed structures and the measured electrochemical charge–discharge characteristics. We further measure the binding ability of gelatin adsorbed from solutions of different pHs. While the best binding ability of gelatin is obtained at pH about 9, the least polarization is observed at pH 12. Both properties are explained based on the observed gelatin structuring as a function of pH. In the second part of this study, gelatin is used as a surface agent that dictates the organization of nanometre-sized carbon black particles around micrometre-sized cathodic active particles. Using microcontact impedance measurements on polished pellets we show that using gelatin-forced carbon black deposition the average electronic resistance around LiMn 2O 4 particles is decreased by more than two orders of magnitude. We believe that it is this decrease in resistance that improves significantly the rate performance of various cathode materials, such as LiMn 2O 4 and LiCoO 2.

Interfacial reactions at electrode/electrolyte boundary in all solid-state lithium battery using inorganic solid electrolyte, thio-LISICON

Electrode/electrolyte interface was studied for all solid-state batteries using inorganic solid electrolyte with the crystalline thio-LISICON and glassy Li–Si–P–S–O systems. The formation of the interfacial phase depends on the electrolyte. The thio-LISICON (Li 3.25Ge 0.25P 0.75S 4) and the Li–Al negative electrode provided the best electrode/electrolyte interface for fast charge–discharge characteristics, while the SEI phase formed at the Li–Al/Li 3PO 4–Li 2S–SiS 2 glass boundary caused high interfacial resistance. The formation of the SEI phase is general behavior at the electrode/electrolyte interface of solid-state batteries, and the fast electrochemical reaction is attained as a result of optimization of the electrode/electrolyte combination.

Organic Electrolytes of Secondary Lithium Batteries

This paper reviews the electrolytes in view of their charge-discharge characteristics, electrochemical and physical properties for the applications to secondary lithium batteries in about past decade. Also this paper mainly encompasses on the lithium organoborates and fluorinated organic solvents for electrolytes of lithium batteries.

Mechanical analysis and in situ structural and morphological evaluation of Ni–Sn alloy anodes for Li ion batteries

In lithium ion batteries, it has previously been shown that Ni–Sn thin film anodes containing 62 at.% Sn show outstanding electrochemical characteristics, e.g. good capacity and endurance, during charge–discharge cycling. However, their mechanical response, which is likely related to their lifetime in service, has so far received relatively little attention. To address this, nanoindentation and nanowear techniques have been used to characterize the mechanical properties of thin Ni–Sn films electrodeposited on a copper substrate. In situ morphology analysis together with in situ stress measurement has been performed to assess the properties of Ni–Sn thin film anodes during electrochemical cycling. The change in mechanical properties, residual stress and fracture behaviour of the anodes is related to the phase changes which occur during charge–discharge cycling. The correlation between the mechanical properties of the films and their charge–discharge characteristics serves as a useful indicator for optimized design of a Sn-based intermetallic anode film for lithium ion secondary batteries.

Solid-State NMR and Electrochemical Dilatometry Study on Li + Uptake/Extraction Mechanism in SiO Electrode

This work reports the uptake/extraction mechanism in silicon monoxide as the negative electrode in lithium secondary batteries. A combined study of solid-state - and -nuclear magnetic resonance (NMR), electrochemical dilatometry, and charge-discharge cycling consistently demonstrates that the domain in irreversibly reacts with to produce lithium silicates and in the first discharging period, whereas the elemental Si domain reversibly reacts, delivering the same charge-discharge characteristics to those of conventional amorphous Si electrodes. The volume expansion accompanied by the irreversible reaction is less significant than that caused by the lithiation of Si domain. The postmortem analysis made on cycled electrodes reveals a phase segregation between the lithium silicates/ and lithiated Si phase. It is likely that the lithium silicates/ phase plays a buffering role against the volume change of Si matrix, but the crack formation at the phase boundaries and eventual pulverization are still a problem to be solved.

Preparation of Anode Material for Lithium Secondary Battery using Pitch-coated Graphite Residue Compounds

The properties and electrochemical characteristics of anode material using pitch-coated graphite residue compounds by heat-treatment at <TEX>$600^{\circ}C$</TEX> for 1 hour were investigated. The distance of layers of pitch-coated graphite residual compounds was 3.3539 <TEX>${\AA}$</TEX>, which was as same as that of graphite. Its electrochemical and charge discharge characteristics were tested according to different four types of carbon material, natural graphite, pitch-coated graphite, amorphous graphite and pitch-coated graphite residual compounds, respectively. So it was shown the best charge-discharge characteristics in all of the samples. For the electrochemical and charge-discharge characteristics, although pitch-coated graphite residual compounds had different carbon contents 70% and 80%, these two samples were shown good electrochemical and charge-discharge characteristics.

Exploration of artificial neural network [ANN] to predict the electrochemical characteristics of lithium-ion cells

CoO anode, as an alternate to the carbonaceous anodes of lithium-ion cells has been prepared and investigated for electrochemical charge–discharge characteristics for about 50 cycles. Artificial neural networks (ANNs), which are useful in estimating battery performance, has been deployed for the first time to forecast and to verify the charge–discharge behavior of lithium-ion cells containing CoO anode for a total of 50 cycles. In this novel approach, ANN that has one input layer with one neuron corresponding to one input variable, viz., cycles [charge–discharge cycles] and a hidden layer consisting of three neurons to produce their outputs to the output layer through a sigmoid function has been selected for the present investigation. The output layer consists of two neurons, representing the charge and discharge capacity, whose activation function is also the sigmoid transfer function. In this ever first attempt to exploit ANN as an effective theoretical tool to understand the charge–discharge characteristics of lithium-ion cells, an excellent agreement between the calculated and observed capacity values was found with CoO anodes with the best fit values corresponding to an error factor of <1%, which is the highlight of the present study.

Development of all-solid lithium-ion battery using Li-ion conducting glass-ceramics

We have developed a high performance lithium-ion conducting glass-ceramics. This glass-ceramics has the crystalline form of Li 1+ x+ y Al x Ti 2− x Si y P 3− y O 12 with a NASICON-type structure, and it exhibits a high lithium-ion conductivity of 10 −3 S cm −1 or above at room temperature. Moreover, since this material is stable in the open atmosphere and even to exposure to moist air, it is expected to be applied for various uses. One of applications of this material is as a solid electrolyte for a lithium-ion battery. Batteries were developed by combining a LiCoO 2 positive electrode, a Li 4Ti 5O 12 negative electrode, and a composite electrolyte. The battery using the composite electrolyte with a higher conductivity exhibited a good charge–discharge characteristic.

Novel Low-Temperature Synthesis and Characterization of Lithium Cobalt Dioxide for Lithium Rechargeable Batteries

Lithium cobalt oxide is synthesized by a novel solution combustion procedure. In this synthesis, a solution mixture of lithium nitrate, cobalt nitrate and glycine fuel is heated to 500, 600 and 700 °C for 3 hours to obtain an ordered crystalline-layered compound. Physical properties of the synthesized cathode materials were evaluated using a XRD, SEM and particle size analyzer. The charge-discharge cycling characteristics of the synthesized lithium cobalt oxide heated at 700 °C exhibited better performance than other materials.

Improvement of electrochemical characteristics of natural graphite negative electrode coated with polyacrylic acid in pure propylene carbonate electrolyte

In order to improve the negative electrode characteristics of a graphite electrode in a propylene carbonate (PC)-containing electrolyte, we have prepared a graphite negative electrode coated with a water-soluble anionic polymer as a binder for composite graphite electrodes. The electrochemical characteristics of the coated graphite were evaluated by cyclic voltammetry and charge–discharge cycle tests. The coated graphite negative electrode showed a stable Li + ion intercalation/deintercalation reaction without the exfoliation of the graphene layers caused by the co-intercalation of the PC solvent in the LiClO 4/PC solution. The charge–discharge characteristic of the coated graphite negative electrode in a PC-containing electrolyte was almost the same as that in ethylene carbonate-based electrolyte.

Enhanced charge-discharge characteristics of RuO2 supercapacitors on heat-treated TiO2 nanorods

Electrochemical capacitors based on RuO2 were prepared onto electrospun TiO2 nanorods. Further heat treatment of the TiO2 at 800°C under nitrogen was found to greatly improve the electrochemical performance of the RuO2 electrodes, especially at fast charge-discharge rates. The specific capacitance was found to decrease by only 33% when the scan rate increased from 10to1000mVs−1 (from 687to460Fg−1). The characteristic response time of the RuO2 electrode was found to be 0.15s when a heat-treated TiO2 substrate was used, which is 20 times better than that of the pristine TiO2 used.

Effect of chemical oxidation for nano-size γ-Fe 2O 3 as lithium battery cathode

Surface treatment of nano-crystalline γ-Fe 2O 3 was examined to improve its electrochemical performances for lithium battery. Removal of residual phases on the surface by chemical oxidation with NO 2BF 4 was confirmed by TG measurement and FT-IR spectroscopy, and the process improved charge–discharge characteristics; higher capacity and better reversibility were obtained. The charge–discharge mechanism was studied by X-ray diffraction measurement and Mössbauer spectroscopy. The reversible charge–discharge reaction of the nano-size γ-Fe 2O 3 was proceeded by a phase transition between the spinel and the disordered rock-salt type, which was previously claimed to be an irreversible process for the bulk materials. The nano-size effect of the phase transitions and the charge–discharge mechanism will be discussed.

Li-Ion Rechargeable Battery with LiMn[sub 1.5]Ni[sub 0.46]Rh[sub 0.04]O[sub 4] Spinel Cathode Material

Limn 1.5 Ni 0.46 Rh 0.04 O 4 cathode material was synthesized by the sol-gel method and used in Li-ion coin cells. The structural and electrochemical studies were carried out using X-ray diffraction and X-ray photoelectron spectroscopy of the cathode material and charge-discharge characteristics of the assembled battery. The lattice parameter before and after charge-discharge cycles were found to be about 8.217 and 8.202 A, respectively. The initial discharge capacity was found to be about 153 mAh/g and the capacity retention was about 93.5% after 50 charge-discharge cycles.

Synthesis and characterization of Nd doped LiMn2O4 cathode for Li-ion rechargeable batteries

Abstract Spinel powders of LiMn 1.99 Nd 0.01 O 4 have been synthesized by chemical synthesis route to prepare cathodes for Li-ion coin cells. The structural and electrochemical properties of these cathodes were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, cyclic voltammetry, and charge-discharge studies. The cyclic voltammetry of the cathodes revealed the reversible nature of Li-ion intercalation and deintercalation in the electrochemical cell. The charge-discharge characteristics for LiMn 1.99 Nd 0.01 O 4 cathode materials were obtained in 3.4–4.3 V voltage range and the initial discharge capacity of this material were found to be about 149 mAh g −1 . The coin cells were tested for up to 25 charge-discharge cycles. The results show that by doping with small concentration of rare-earth element Nd, the capacity fading is considerably reduced as compared to the pure LiMn 2 O 4 cathodes, making it suitable for Li-ion battery applications.

Effect of the modification of metal-hydride electrodes based on Ti2Ni alloys on their discharge characteristics

We have developed a new computerized PGStat-8 device for the high-cycle charge-discharge of electrodes under galvanostatic or potentiostatic conditions and, with its help, have investigated the charge-discharge characteristics of metal-hydride electrodes based on Ti2Ni-type alloys. We show the effect of partial replacement Ti → Zr or V and Ni → Co or Cu, modification with oxygen, homogenizing annealing, polymeric addition, and metallic binder on the discharge capacity and cyclic stability of the prepared metal-hydride electrodes.