Retention Of Initial Capacitance Research Articles

Rechargeable hybrid aqueous batteries

A new aqueous rechargeable battery combining an intercalation cathode with a metal (first order electrode) anode has been developed. The concept is demonstrated using LiMn2O4 and zinc metal electrodes in an aqueous electrolyte containing two electrochemically active ions (Li+ and Zn2+). The battery operates at about 2 V and preliminarily tests show excellent cycling performance, with about 90% initial capacity retention over 1000 charge–discharge cycles. Use of cation-doped LiMn2O4 cathode further improves the cyclability of the system, which reaches 95% capacity retention after 4000 cycles. The energy density for a prototype battery, estimated at 50–80 Wh kg−1, is comparable or superior to commercial 2 V rechargeable batteries. The combined performance attributes of this new rechargeable aqueous battery indicate that it constitutes a viable alternative to commercial lead-acid system and for large scale energy storage application.

Preparation of novel SnO2–B2O3 core–shell nanocomposite and their lithium storage ability

Herein we reported a novel SnO2–B2O3 core–shell nanocomposite synthesized with a modified molten-salt decomposition method, in which SnO2 particles were firstly dispersed in the molten SnSO4–B2O3 system, followed by solidification of a hard B2O3 shell. By limiting the volume expansion of SnO2 particles with the super-hard B2O3 layer, the electrochemical performances of the SnO2–B2O3 electrode were enhanced significantly, in terms of both the initial discharge capacity and capacity retention. The 100th cycle reversible capacity of the SnO2–B2O3 electrode remained as high as 537mAhg−1 at a current density of 156mAg−1. This method is greatly promising for a large-scale synthesis of nanosized SnO2 anode materials.

Cycling Performance of Li4Ti5O12Electrodes in Ionic Liquid-Based Gel Polymer Electrolytes

electrodes in ionic liquid-based gel polymer electrolytes exhibitedreversible cycling behavior with good capacity retention. Cycling data and electrochemical impedancespectroscopy analyses revealed that the optimum content of the cross-linking agent necessary to ensure bothacceptable initial discharge capacity and good capacity retention was about 8 wt %. Key Words : Anode, Ionic liquid, Gel polymer electrolyte, Lithium-ion battery, Li

Development of nano-composite adsorbent for removal of heavy metals from industrial effluent and synthetic mixtures; its conducting behavior

A semi-crystalline stable composite cation exchange adsorbent for the treatment of heavy metal ions has been synthesized at pH 1.0 by sol–gel method which was characterized by FTIR, XRD, SEM, TGA and TEM analysis. Ion exchange capacity, pH titration, elution behavior and distribution studies were also carried out to determine the primary ion-exchange characteristics of the material. The material shows exchange capacity of 1.47meqg−1 (for Na+ ions). The composite material exhibits improved ion-exchange capacity, chemical and thermal stability. It can be used up to 200°C with 88% retention of initial ion-exchange capacity. pH titration data reveal its bifunctional behavior. The distribution coefficient values (Kd) of metal ions have been determined in various solvent systems. On the basis of Kd values the material was selective for Ba(II), Hg(II), and Pb(II) ions. The limit of detection (LOD) and the limit of quantification (LOQ) for Pb(II) was found to be 0.97 and 2.93μgL−1, respectively. A number of important and analytically difficult quantitative separations of metal ions have been achieved using columns packed with this exchanger. The composite cation exchanger is applied for the treatment of sewage water and synthetic mixture successfully and can be used as a conducting material.

Nanocrystalline ruthenium oxide dispersed Few Layered Graphene (FLG) nanoflakes as supercapacitor electrodes

Significant enhancement in supercapacitor performance was achieved via the synthesis of nanocrystalline RuO2 on vertically aligned Few Layered Graphene (FLG) nanoflakes, synthesized on bare n-type heavily doped silicon substrates by microwave plasma chemical vapour deposition. The RuO2 nanoparticles (diameter <2 nm) were deposited using a combination of low base pressure radio frequency magnetron sputtering and subsequent electrochemical cycling in acidic media. The well-dispersed RuO2 nanoparticles on FLGs achieve a specific capacitance of the order of 650 F g−1. The specific capacitance of RuO2–FLGs is significantly higher than pristine sputtered RuO2 (∼320 F g−1) and FLGs (∼6 F g−1) indicative of the synergistic effect between the FLGs and RuO2. In addition, the fabricated RuO2–FLG supercapacitors show excellent cycling capability with approximately 70% retention of initial specific capacitance over 4000 cycles at high charging–discharging rates of 500 mV s−1. The superior electrochemical performance is attributed to the good electronic conductivity of the FLGs as well as high utilization of well-dispersed RuO2 nanoparticles on FLGs.

Nano-Carbon Coating Layer Prepared by the Thermal Evaporation of Fullerene C&lt;SUB&gt;60&lt;/SUB&gt; for Lithium Metal Anodes in Rechargeable Lithium Batteries

A nano carbon coating layer was prepared by the thermal evaporation of fullerene C60 on the surface of lithium metal anodes for rechargeable lithium batteries. The morphology and structure of the carbon layer was firstly investigated by Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the nano-carbon coating layer on the electrochemical performance of the lithium electrode were then examined by charge-discharge tests and impedance spectroscopy. Raman spectra of carbon coating layer showed two main peaks (D and G peaks), indicating the amorphous structure of the film. A honey comb-like structure of carbon film was observed by TEM photographs, providing a transport path for the transport of lithium ions at the electrode/electrolyte interface. The carbon coated lithium electrodes exhibited a higher initial coulombic efficiency (91%) and higher specific capacity retention (88%) after the 30th cycle at 0.2 C-rate between 3.4 and 4.5 V. Impedance measurements showed that the charge transfer resistance was significantly reduced after cycle tests for the carbon coated electrodes, revealing that the more stable solid electrolyte (SEI) layer was established on their surface. Based on the experimental results, it suggested that the presence of the nano-carbon coating layer might suppress the dendritic growth on the surface of lithium metal electrodes, as confirmed by the observation of SEM images after cycle tests.

Preparation and characterization of a special structural poly(acrylonitrile)-based microporous membrane for lithium-ion batteries

In this work, a special structural poly(acrylonitrile) (PAN)-based microporous membrane for lithium-ion batteries is prepared from PAN emulsion by simple casting and extracting techniques. It is found that the microporous membrane is fabricated by PAN particles with uniform size (about 580 nm), and a lot of micropores exist among the particles. The Gurley number of the microporous membrane obviously depends on the amount of additive but the porosity does not. The PAN-based microporous membrane is activated by non-aqueous liquid electrolyte to form microporous gel electrolyte (MGE), and its ionic conductivity increases with the decrease of the Gurley number. The resulting MGE shows typical thermal shut-down action because of the swelling–incorporating behaviors of PAN-based particles by the help of the solvent of liquid electrolyte at high temperature. In addition, the electrochemical stability window of the MGE can extend to 5.5 V vs. Li+/Li. The test cell using MGE as separator shows high initial discharge capacity (143 mAh g-1 based on LiCoO2) and high capacity retention ratio (around 94.8% at the 50th cycle). Generally, the special structural microporous membrane is promisingly used to prepare high-safety lithium-ion batteries.

Facile scalable synthesis of magnetitenanocrystals embedded in carbon matrix as superior anode materials for lithium-ion batteries

A simple and scalable process was developed for the synthesis of highly crystalline magnetite nanocrystals embedded in a carbon matrix using low cost starting materials; the resulting nanocomposite showed a very high specific capacity of 863 mA hg(-1) in the initial cycle and high capacity retention of 90% after 30 cycles.

Electrochemical hydrogen storage capacities of Mg2Ni and MgNi alloys synthesized by mechanical alloying

Mg2Ni and MgNi alloys were synthesized by the mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. The XRD peaks indicated that MgNi alloy was mainly in the amorphous characteristics while Mg2Ni alloy was composed of mixture of amorphous and nano-crystalline structures. The development of the amorphous structure in MgNi alloy was very fast and the maximum storage capacity was reached at 15 h ball milling. The maximum storage capacity of Mg2Ni alloy was observable after at least 40 h ball milling. Both the initial discharge capacity and capacity retention rate of MgNi alloy were much greater than those of Mg2Ni alloy. This observation was mainly attributed to the relatively reversible charge/discharge behavior of MgNi alloy. The charge transfer resistance of Mg2Ni alloy was greater than that of MgNi alloy especially at the higher depths of discharges. The presence of free electro-catalytically active Ni particles on MgNi alloy surface was thought as the main reason for the facilitated hydrogen charge transfer reactions on this alloy.

Magnetic field assisted chemical reduction preparation of Co–B alloys as anode materials for alkaline secondary battery

In this work, we reported the magnetic field assisted preparation of amorphous Co–B alloy by reducing CoCl 2 with alkaline sodium borohydride (NaBH 4) in solution. The prepared Co–B alloy has been characterized by scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) adsorption, energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electrochemical measurements. It was found that the Co–B alloy prepared under an external magnetic field shows a large amount of nanowire-like structures. Meanwhile, its B content and specific surface area are 24% and 99.6 m 2/g, respectively. On the contrary, the Co–B alloy prepared without the magnetic field exhibits many aggregates consisting of nanoparticles, and its B content and specific surface area are only 15.4% and 38.5 m 2/g, respectively. Particularly, electrochemical measurements indicate that the Co–B alloy prepared under the magnetic field exhibits better high-rate dischargeability. At a high rate of 650 mA/g, its initial discharge capacity and capacity retention after 100 cycles are 287 mAh/g and 84%, respectively, significantly higher than that of Co–B alloy prepared without magnetic field. Even at a discharge rate as high as 6 C (1800 mA/g), the Co–B alloy prepared under a magnetic field can still deliver a reversibly electrochemical capacity of 243 mAh/g, which can be attributed to its larger specific area, its enhanced B content and its nanowire structures.

Influence of synthesis conditions on electrochemical properties of high-voltage Li1.02Ni0.5Mn1.5O4 spinel cathode material

Abstract Li1.02Ni0.5Mn1.5O4 spinel cathode materials were successfully synthesized by a citric acid-assisted sol–gel method. The structure and morphology of the materials have been examined by X-ray diffraction and scanning electron microscopy, respectively. Electrochemical properties of the materials were investigated using cyclic voltammetry and galvanostatic charge/discharge measurements at two different temperatures (25 and 55 °C) using lithium anode. The initial capacity and capacity retention are highly dependent on the particle size, particle size distribution, crystallinity and purity of the materials. The Li1.02Ni0.5Mn1.5O4 materials synthesized both at 800 and 850 °C have shown best electrochemical performance in terms of capacity and capacity retention between 3.5 and 4.9 V with a LiPF6 based electrolyte.

Influence of Sputtering Conditions on Structural and Electrochemical Properties of the Si Anode Film for Lithium Secondary Batteries

)Abstract This study investigated the dependence of the various sputtering conditions (Ar pressure:2~10 mTorr, Power: 50~150 W) and thickness (50~1200 nm) of Si thin film on the electrochemical properties,microstructural properties and the capacity fading of a Si thin film anode. A Si layer and a Ti buffer layerwere deposited on Copper foil by RF-magnetron sputtering. At 10 mTorr, the 50 W sample showed the bestcapacity of 3323 mAh/g, while the 100 W sample showed the best capacity retention of 91.7%, also at 10 mTorr.The initial capacities and capacity retention in the samples apart from the 50 W sample at 10 mTorr wereenhanced as the Ar pressure and power increased. This was considered to be related to the change of themicrostructure and the surface morphology by various sputtering conditions. In addition, thinner Si film anodesshowed better cycling performance. This phenomenon is caused by the structural stress and peeling off of theSi layer by the high volume change of Si during the charge/discharge process.Key wordslithium ion battery, silicon anode, deposition condition, sputtering.

Filter paper templated interconnected nanocrystalline LiMn2O4 with high coulombic efficiency and rate capability

A novel filter paper templating method has been developed to prepare nanocrystalline LiMn2O4. Whatman 42 filter paper impregnated with the precursor gel produces ultrafine powder (80–100 nm) when calcined at 800 °C. The structure and morphology of the powder and the template have been studied in detail by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). A single phase cubic spinel with interconnected powder morphology is found. The electrochemical properties have been studied using 2032 coin type cells in the potential window of 3.4 to 4.5 V versusLi/Li+. Sharp oxidation–reduction peaks at 4.09/3.90V and 4.22/4.04V in the cyclic voltagram indicate high crystallinity and good reversibility of the cathode. A typical cell shows an initial discharge capacity of 97 mAh/g with ∼98% columbic efficiency. Rate capability study of the synthesized cathode has been performed by cycling the cell for 130 cycles at different current densities (0.1–1.5 mA/cm2) and it is observed that 80–100% retention of initial capacity is possible when cycled at 0.1–0.6 mA/cm2. A capacity fading of only 0.03 mAh/g per cycle is observed even at 1.5 mA/cm2 (8C). Thus, we have shown that simple filter paper templating technique can produce nanocrystalline LiMn2O4 with high coulombic efficiency (100–95%) and rate capability.

Synthesis and characterization of LiNi 0.6Mn 0.4− xCo xO 2 as cathode materials for Li-ion batteries

LiNi 0.6Co x Mn 0.4− x O 2 ( x = 0.05, 0.10, 0.15, 0.2) cathode materials are prepared, and their structural and electrochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetric (DSC) and charge–discharge test. The results show that well-ordering layered LiNi 0.6Co x Mn 0.4− x O 2 ( x = 0.05, 0.10, 0.15, 0.2) cathode materials are successfully prepared in air at 850 °C. The increase of the Co content in LiNi 0.6Mn 0.4− x Co x O 2 leads to the acceleration of the grain growth, the increase of the initial discharge capacity and the deterioration of the cycling performance of LiNi 0.6Mn 0.4− x Co x O 2. It also leads to the enhancement of the ratio Ni 3+/Ni 2+ in LiNi 0.6Co x Mn 0.4− x O 2, which is approved by the XPS analysis, resulting in the increase of the phase transition during cycling. This is speculated to be main reason for the deteriotion of the cycling performance. All synthesized LiNi 0.6Co x Mn 0.4− x O 2 samples charged at 4.3 V show exothermic peaks with an onset temperature of larger than 255 °C, and give out less than 400 J g −1 of total heat flow associated with the peaks in DSC analysis profile, exhibiting better thermal stability. LiNi 0.6Co 0.05Mn 0.35O 2 with low Co content and good thermal stability presents a capacity of 156.6 mAh g −1 and 98.5% of initial capacity retention after 50 cycles, showing to be a promising cathode materials for Li-ion batteries.

Electrochemical performance of SrF2-coated LiMn2O4 cathode material for Li-ion batteries

SrF2-coated LiMn2O4 powders with excellent electrochemical performance were synthesized. The electrochemical performance of SrF2-coated LiMn2O4 electrodes was studied as function of the level of SrF2 coating. With increasing the amount of the coated-SrF2 to 2.0% (molar fraction), the discharge capacity of LiMn2O4 decreases slightly, but the cycleability of LiMn2O4 at elevated temperature is improved obviously. In view of discharge capacity and cycleability, the 2.0% (molar fraction) coated sample shows optimum cathodic behaviors. When being cycled at 55 °C, as-prepared LiMn2O4 remains only 79% of its initial capacity after 20 cycles, whereas the 2.0% (molar fraction) coated sample shows initial discharge capacity of 108 mA-h/g, and 97% initial capacity retention.

Effect of Catalyst on the Performance of Rechargeable Lithium/Air Batteries.

Rechargeable lithium batteries are now a major technology, driven by their superior energy density compared with alternative rechargeable batteries. There is much interest in increasing further the energy density. This is limited by the positive electrode, LiCoO2, which can cycle only around 0.5 Li per formula unit. Intensive research world-wide on new intercalation cathodes will increase the amount of Li that may be stored, but only by a factor of 2. Replacing the intercalation cathode with an O2 electrode could raise the capacity 5-10-fold. Here we explore the influence of the catalyst could have on the performance of a non-aqueous O2 electrode on a Li/O2 cell. Of the catalysts studied, the highest capacity retentions were observed with Fe3O4, CuO and CoFe2O4 (6.67% per cycle). Co3O4 gives the best compromise between initial capacity (2000mAhg-1) and capacity retention (6.5% per cycle), as well as the lowest charging voltage 4V.

Three-dimensional Porous Cu 6Sn 5 Alloy Anodes for Lithium-ion Batteries

Three-dimensional porous Cu 6Sn 5 alloy electrodes were prepared by electroplating using copper foam as the current collector. The micro-holes and small islands on surface of the Cu 6Sn 5 alloy largely increased the surface area of the electrode, and significantly improved the ability of the electrode in buffering the volume change in the process of charge/discharge when the Cu 6Sn 5 alloy was employed as the anode in a lithium-ion battery. Galvonostatic charging/discharging results demonstrated that the initial discharge (lithiation) and charge (delithiation) specific capacities of the Cu 6Sn 5 alloy electrode were 620 mAh·g −1 and 560 mAh·g −1, respectively. It demonstrated that the Cu 6Sn 5 alloy electrode exhibited a large initial coulomb efficiency (90.3%) and good capacity retention. Scanning electron microscopy (SEM) results illustrated that the Cu 6Sn 5 alloy deposited on copper foam substrate was more stable than that on a conventional copper substrate, and displayed no obvious exfoliation after 50 charge/discharge cycles.

An O 2 cathode for rechargeable lithium batteries: The effect of a catalyst

The energy density of current rechargeable lithium batteries is limited by the capacity of the LiCoO 2 positive electrode (140 mA h g −1). The best intercalation electrode is only likely to increase this by a factor of 2 (1Li/Tm). Replacing the intercalation cathode with an O 2 electrode could raise the capacity 5–10-fold. Here, we explore the influence of the catalyst could have on the performance of a non-aqueous O 2 electrode on a Li/O 2 cell. Of the catalysts studied the highest initial capacity was observed with Fe 2O 3 (2700 mA h g −1), the highest capacity retention with Fe 3O 4, CuO and CoFe 2O 4 (6.67% per cycle). Co 3O 4 gives the best compromise between initial capacity (2000 mA h g −1) and capacity retention (6.5% per cycle), as well as the lowest charging voltage 4 V. All capacities expressed per gram of carbon and at a rate of 70 mA g −1.

A new class of cathode materials for rechargeable magnesium batteries: Organosulfur compounds based on sulfur–sulfur bonds

A class of energy storage materials, organosulfur compounds with S–S bonds, has been proposed as novel cathode materials for rechargeable magnesium batteries. The cleavage and recombination of S–S bonds formed during discharge and charge process are the key components for the capacity. The cathode performance of three organosulfur materials, i.e. 2,5-dimercapto-1,3,4-thiadiazole (DMcT), poly-2,2′dithiodianiline (PDTDA) and a conductive sulfur-containing material (CMS) were characterized here. Among them, DMcT compounded with polyaniline (PAn) can provide a relatively flat discharge potential at about 1.4 V vs. Mg/Mg 2+. PDTDA exhibits better kinetics and electrical conductivity based on the intramolecular electrocatalytic effect of the aniline moiety on thiolate anions. CMS compounded with PAn produces stable backbones to provide electrically conducting channels and higher disulfide bond content; it exhibits nearly 120 mAh/g initial discharge capacity and good capacity retention. We expect that further improvements to the capacity and cyclability will make organosulfur compounds potential cathode materials for magnesium batteries.

High rate capability of the Mg-doped Li–Mn–O spinel prepared via coprecipitated precursor

Coprecipitation was applied to prepare Mg–Mn hydroxide precursor for optimal synthesis of Mg-doped Li–Mn–O spinel. The as-obtained precursor was then mixed with LiOH followed by an annealing at 850 oC for 15 h. The spinel prepared from coprecipitated precursor can deliver over 100 mAh g −1 at a discharge rate as high as 10 C (1.2 A g −1) and retain 100% of the initial capacity in the 45th cycle while the spinel prepared directly from the as-purchased metal salts yields both smaller initial capacity and lower capacity retention after cycling. It was found that the crystallinity is higher and the charge transfer resistance is lower for the spinel prepared via coprecipitated precursor, which maybe resulted from the more homogeneous distribution of metal ion in such a spinel, than that in the spinel prepared from as-purchased reagents.