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Lithium cobalt oxides (LiCoO2) possess a high theoretical specific capacity of 274 mAh g–1. However, cycling LiCoO2-based batteries to voltages greater than 4.35 V versus Li/Li+ causes significant structural instability and severe capacity fade. Consequently, commercial LiCoO2 exhibits a maximum capacity of only ~165 mAh g–1. Here, we develop a doping technique to tackle this long-standing issue of instability and thus increase the capacity of LiCoO2. La and Al are concurrently doped into Co-containing precursors, followed by high-temperature calcination with lithium carbonate. The dopants are found to reside in the crystal lattice of LiCoO2, where La works as a pillar to increase the c axis distance and Al as a positively charged centre, facilitating Li+ diffusion, stabilizing the structure and suppressing the phase transition during cycling, even at a high cut-off voltage of 4.5 V. This doped LiCoO2 displays an exceptionally high capacity of 190 mAh g–1, cyclability with 96% capacity retention over 50 cycles and significantly enhanced rate capability.
The performance of portable electronic equipment can often be improved by including an electrochemical capacitor alongside the battery. The capacitor extends battery life by reducing its peak output power. A CR2032 coin-type battery cell was used for the LiCoO2 cathode and Li anode. A mixture of 1M LiPF6-ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1 vol, Merk) was used as the electrolyte. The electrochemical characteristics of a supercapacitor are able to provide a much higher pulse current capability than the battery system. By combining a supercapacitor and a battery, the pulse performance of a battery can be significantly improved according to various pulse times.
Here, we develop a facile electrochemical polymerization method for the synthesis of polypyrrole (PPy) nanowires on Pd modified Nafion® membranes. Interestingly, with altering the deposition potential and temperature, we can easily tune the PPy nanowires from disordered nanostructures to well ordered vertically aligned nanowires. The various PPy nanowires show similar electronic conductivity but diverse hydrophobicity/hydrophilicity. The ordered PPy nanowires can significantly facilitate the mass transport and enhance the catalyst utilization. These two factors together make an obvious performance improvement of fuel cells.
A novel LiNO3-KNO3-Mg(OH)NO3 ternary molten salt system is used as electrolyte with Li-Mg-B alloy/MnO2 couples for possible use as a power source for geothermal borehole applications. Chemical-compatibility studies of these materials are conducted using simultaneous differential thermal analysis (DTA) and thermo gravimetric analysis (TGA). The ionic conductivity of the new electrolyte has been evaluated by electrochemical impedance spectroscopy (EIS) and its value range from 0.107 to 0.457 Scm−1 in the temperature range from 150 to 300°C. The discharge behavior of the system is studied over a temperature range of 150 to 300°C at current densities from 10 to 30mAcm−2. At 200 to 300°C, discharge behavior seems unaffected by discharge rate. However, the system has some specific restrictions associated with temperature.
Three-dimensional (3D) conductive network electrodes based on commercial nickel foam current collector supported Si nanowires (SiNWs) with carbon coating are evaluated as lithium-ion battery anodes. The Ni foam network current collector achieves a high silicon loading up to 5mg/cm2, without using any non-conductive binders. The pressed carbon coated SiNWs–Ni electrode shows outstanding electrochemical performance. It achieves an initial capacity of as high as 2486mAh/g. A reversible capacity of 1500mAh/g is still retained even after 50 cycles of charging and discharging. The good performance could be attributed to the 3D Ni–C network current collector structure that provides flexible room to effectively accommodate the volume change of Si nanowires and minimizes loss of electrical contact after long time cycling. The 3D composite network provides a new design principle of robust and scalable lithium-ion battery electrodes that can effectively relieve the significant volume change problem.
We demonstrate here the possibility of operating both high voltage spinel and high mass loading graphite electrodes in a 1 M LiPF6 in SL/DMC (1/1, wt/wt) electrolyte without the use of additive. A crucial point for practical graphite electrode operation is the use of the cheaper and environmentally friendly carboxymethyl cellulose (CMC)/styrene-butadiene rubber (SBR) combination instead of the PVDF-based electrodes used in most laboratory studies. With this type of anode we also show the operation of a full Li-ion cell operating at 4.5 V without any additive and show that most of the Li+ transport limitation observed in half-cells are in fact due to the Li metal counter electrode. The anode binder influence is to be considered for the development of high voltage electrolytes lacking good intrinsic SEI building properties, as the anode binder does not affect cathode performance, contrary to most additives. It opens the route for further improvement by use of SEI forming additives (molecular and salts), keeping in mind the requirement for the cathode.
The behavior of three gas diffusion electrodes (GDE) with macro- and mesopores is investigated by in situ electrochemical impedance spectroscopy (EIS) in the Li/O2 battery system while discharging. Using a three electrode setup the current response from the anode (Li metal) and cathode (GDE) can be separated and the changes of the electrochemical processes at the GDE during discharge can be observed, exclusively. We identify up to four processes with different time constants which we assign to the lithium ion migration through a surface layer, the charge-transfer from the carbon surface to the molecular oxygen, the lithium ion and oxygen diffusion towards the cathode surface and, in case of the mesoporous materials, the lithium ion movement inside the pores, along the pore axis. The latter finding reflects that pore clogging of such is a limiting factor for the discharge of the Li/O2 battery. A large mesopore volume as in the xerogel electrode, however, allows for a high storage capability and a long and constant oxygen reduction. We demonstrate that the three electrode EIS proves to be a powerful in situ diagnostic tool to determine the state and, hence, the reversibility of the reactions at the cathode.
We identify that reversible formation/decomposition of lithium oxide, pulverization of Fe3O4 nanoparticles, and electrolyte reactions, are contributors to the enhanced capacity observed in the Fe3O4 electrode upon long cycling. Introducing three-dimensional graphene foam to form a composite with Fe3O4 nanoparticles largely increases the capacity (~ 1220mAhg−1 vs. ~ 690mAhg−1) and promotes the cycling induced capacity enhancement (an earlier capacity rise and a faster rising rate) of the Fe3O4 electrode. Together with Fe3O4 nanoparticles, the presence of graphene effectively promotes the electrolyte reactions and reversible formation/decomposition of lithium oxide. At the same time, activation of GF also occurs in the presence of Fe3O4 nanoparticles, further increases the capacity of the nanocomposite.
A new template-approach was demonstrated to fabricate N-doped graphitic nanocages (NGNs) with designable doped structure for efficiently electrocatalyzing oxygen reduction and their graphitic structure has been prepared with in situ N-doping from floating catalytic pyrolysis of N-precursors, catalysts and carbon resources. Because of short time pyrolysis, the process of pyrolyzing N-precursors is incomplete, leading to the structure of N-doping is made up from inheriting incompletely pyrolyzed the precursor. Thus, its structure can be optimized by using a special precursor in this approach. Compared with nanocages prepared from acetonitrile, NGNs prepared from imidazole or pyrrole have pyrrolic structures, leading to their more efficient catalysis for oxygen reduction reaction (ORR). Furthermore, compared with N-doped structure prepared from pyrrole, the structure prepared from imidazole has one more N atom in each pyrrolic ring, which enhances O2 bridge adsorption and leads to the efficient ORR.
Lithium-ion batteries are important for energy storage in a wide variety of applications including consumer electronics, transportation and large-scale energy production. The performance of lithium-ion batteries depends on the materials used. One critical component is the electrolyte, which is the focus of this paper. In particular, inorganic ceramic and organic polymer solid-electrolyte materials are reviewed. Solid electrolytes provide advantages in terms of simplicity of design and operational safety, but typically have conductivities that are lower than those of organic liquid electrolytes. This paper provides a comparison of the conductivities of solid-electrolyte materials being used or developed for use in lithium-ion batteries.
Absorptive glass mat (AGM) separators are widely used for valve regulated lead acid (VRLA) batteries due to their remarkable fiber and structural characteristics. Discharge performance and recharge effectiveness of VRLA batteries essentially rely on the distribution and saturation levels of the electrolyte within the AGM separator. Herein, we report an analytical model for predicting the wicking characteristics of AGM battery separators under unconfined and confined states. The model of wicking behavior of AGM is based upon Fries and Dreyer's approach that included the effect of gravity component which was neglected in classic Lucas-Washburn's model. In addition, the predictive model of wicking accounted for realistic structural characteristics of AGM via orientation averaging approach. For wicking under confined state, the structural parameters have been updated under defined level of compressive stresses based upon the constitutive equation derived for a planar network of fibers in AGM under transverse loading conditions. A comparison has been made between the theoretical models and experimental results of wicking behavior under unconfined and confined states. Most importantly, the presented work has highlighted the questionable validity of classic Lucas-Washburn model for predicting the wicking characteristics of AGM separator over longer time duration.
The ZnO/SnO2 heterogeneous nanofibers (HNFs) have been prepared via an electrospinning method followed by calcination at 500°C in air. XRD, BET, SEM, TEM and electrochemical measurements were performed to characterize the new material, including structure, morphology and electrochemical properties. The spacing between adjacent SnO2 nanorods on mesoporous ZnO nanofibers is about twice the diameter of each SnO2 nanorod. The SnO2/ZnO11 (molar ratio of Sn: Zn=1:1) HNFs based electrodes exhibit excellent cycle performance and rate performance, which is attributed to the heterogeneous and mesoporous structure as well as the ultrafine ZnO NPs embedded in the HNFs matrix. Outstanding electrochemical performance as anode material for LIBs together with low cost, facile procedures and high reproducibility make the SnO2/ZnO HNFs have a prospect in the field of energy storage.
To improve the safety of lithium-ion batteries, cresyl diphenyl phosphate (CDP) was used as a flame retardant additive in a LiPF6 electrolyte solution. The flammability of the electrolytes containing CDP and the electrochemical performances of the cells, LiCoO2/Li, graphite/Li and the battery LiCoO2/graphite with these electrolytes, were studied by measuring the self-extinguishing time of the electrolytes, the variation of surface temperature of the battery and the charge/discharge curve of the cells or battery. It is found that the addition of CDP to the electrolyte provides a significant suppression in the flammability of the electrolyte and an improvement in the thermal stability of battery. On the other hand, the electrochemical performances of the cells become slightly worse due to the application of CDP in the electrolyte. This alleviated trade-off between the flammability and thermal stability and cell performances provides a possibility to formulate a nonflammable electrolyte by using CDP.
Biodiesel and ethanol are fuels in clear growth and evidence, basically due to its relation with the greenhouse effect reduction. There are several works regarding regulated pollutants emissions, but there is a lack of reports in non-regulated emissions. In a previous paper (Corrêa and Arbilla, 2006) the emissions of aromatic hydrocarbons were reported and in 2007 another paper was published in 2008 focusing carbonyls emissions (Corrêa and Arbilla, 2008). In this work four mercaptans (methyl, ethyl, n-propyl and n-butyl mercaptans) were evaluated for a heavy-duty diesel engine, fueled with pure diesel (D) and biodiesel blends (v/v) of 2% (B2), 5% (B5), 10% (B10), and 20% (B20). The tests were carried using a six cylinder heavy-duty engine, typical of the Brazilian fleet of urban buses, during a real use across the city. The exhaust gases were diluted near 20 times and the mercaptans were sampled with glass fiber filters impregnated with mercuric acetate. The chemical analyses were performed by gas chromatography with mass spectrometry detection. The results indicated that the mercaptans emissions exhibit a reduction with the increase of biodiesel content, but this reduction is lower as the mercaptan molar mass increases. For B20 results the emission reduction was 18.4% for methyl mercaptan, 18.1% for ethyl mercaptan, 16.3% for n-propyl mercaptan, and 9.6% for n-butyl mercaptan.
The reasons for and against composite indicators are briefly reviewed, as well as the available theories for their construction. After noting the strong normative dimension of these measures—which ultimately aim to ‘tell a story’, e.g. to promote the social discovery of a particular phenomenon, we inquire whether a less partisan use of a composite indicator can be proposed by allowing more latitude in the framing of its construction. We thus explore whether a composite indicator can be built to tell ‘more than one story’ and test this in practical contexts. These include measures used in convergence analysis in the field of cohesion policies and a recent case involving the World Bank’s Doing Business Index. Our experiments are built to imagine different constituencies and stakeholders who agree on the use of evidence and of statistical information while differing on the interpretation of what is relevant and vital.
Macroporous Li(Ni1/3Co1/3Mn1/3)O2 synthesized by a simple non-hydroxide route has been characterize as a high-energy and high-power positive electrode for rechargeable lithium batteries, exhibiting a discharge capacity of 195mAhg−1 at 1C (2244WhL−1) and 175mAhg−1 at 10C (2008WhL−1) and 99.99% capacity retention. Note the volumetric calculations are based on composite electrodes, not just the volume of the active material. Comparison between macroporous Li(Ni1/3Co1/3Mn1/3)O2 and the material synthesized by the conventional hydroxide method demonstrates that the latter shows a significant increase in polarization upon cycling whereas the former material does not. Cycling at 50°C shows that the macroporous material does exhibit more polarization at elevated temperatures. Macroporous Li(Ni1/3Co1/3Mn1/3)O2 has been tested with a graphite negative electrode in a rocking-chair cell. Cycling was inferior to that with a Li metal negative electrode, but the origin of this may lie with the negative electrode. Powder X-ray diffraction also collected on macroporous Li(Ni1/3Co1/3Mn1/3)O2 after 100 cycles to 4.2 and 4.6V, shows excellent structural stability, whereas cycling to 4.2V induces a reduction in the Li/Ni site exchange from 4% to 2%, no significant change occurs for cycling to 4.6V.
A sensitivity analysis of a mathematical model of a lithium–sulfur (Li–S) battery was performed, focusing on the precipitation rate constants and sulfur content, by investigating the response of the model to the variation of these parameters over a wide mathematical range. The necessity of rapid dissolution of elemental sulfur and rapid precipitation of reduced sulfur is discussed in detail. The sensitivity analysis suggests modifying the reduction reaction steps of sulfur can improve the predictions of the model of Li–S battery. Furthermore, an upper limit on the sulfur content of the cathode exists to ensure optimal performance. Although the model provides valuable knowledge concerning Li–S batteries, a modification to the assumed five-step reduction of sulfur combined with the consideration of the insulating nature of the active material is required to improve the model.
While there is strong evidence from rodent and human studies that a reduction in serotonin transporter (5-HTT) function in early-life can increase the risk for several neuropsychiatric disorders in adulthood, the effects of reduced 5-HTT function on behavior across developmental stages are underinvestigated. To elucidate how perinatal pharmacological and lifelong genetic inactivation of the 5-HTT affects behavior across development, we conducted a battery of behavioral tests in rats perinatally exposed to fluoxetine or vehicle and in 5-HTT−/− versus 5-HTT+/+ rats. We measured motor-related behavior, olfactory function, grooming behavior, sensorimotor gating, object directed behavior and novel object recognition in the first three postnatal weeks and if possible the tests were repeated in adolescence and adulthood. We also measured developmental milestones such as eye opening, reflex development and body weight. We observed that both pharmacological and genetic inactivation of 5-HTT resulted in a developmental delay. Except for hypo-locomotion, most of the observed early-life effects were normalized later in life. In adolescence and adulthood we observed object directed behavior and decreased novel object recognition in the 5-HTT−/− rats, which might be related to the lifelong inactivation of 5-HTT. Together, these data provide an important contribution to the understanding of the effects of perinatal and lifelong 5-HTT inactivation on behavior across developmental stages.
Flow batteries have different performance characteristics than established storage technologies such as lithium-ion and lead-acid. We model advanced lead-acid, lithium-ion, and flow batteries for commercial and industrial customers under various tariff scenarios providing retail and wholesale market services to determine if flow batteries can compete in the retail market. We find that flow batteries are uncompetitive with lithium-ion and lead-acid batteries across a range of use cases and modelling assumptions. Flow batteries at a 4-h duration must be less expensive than their competitors on a dollar per installed kWh basis, often by 20–30%, to break even with shorter duration li-ion or lead-acid despite allowing for deeper depth of discharge and superior cycle life. Our results are robust to assumptions of tariff rates, battery round-trip efficiencies, amount of solar generation and whether the battery can participate in the wholesale energy and ancillary services markets.
In this work, MnO2 nanoflakes are electrochemically deposited on preformed C/TiO2 shell/core nanowire arrays to form a shell/shell/core arrays electrode (MnO2/C/TiO2). Their structure and surface morphology are studied by using X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results suggest that MnO2 nanoflakes have well-distributed covered on the surface of C/TiO2 shell/core nanowire arrays. The MnO2/C/TiO2 shell/shell/core arrays are evaluated as a supercapacitor electrode material, which exhibits high specific capacitance of 639 F g−1 at a charge/discharge current density of 1 A g−1 and 78.7% specific capacitance retained after 1000 cycles. The superior pseudo-capacitive properties are attributed to the unique shell/shell/core structure for easy access of electrolyte ions, large surface to volume and high electrochemical activity. Our result shows that three-dimensional hierarchical nanostructures are being regarded advantageous for electrochemical energy applications.
The carbon-coated monoclinic Li3V2(PO4)3/C composite was prepared via rheological phase method with EDTA (ethylene diamine tetraacetic acid), a new type of carbon source. XRD patterns demonstrate the pure monoclinic structure of the sample. The images of SEM show the uniform and optimized particles size, which greatly improves the electrochemical performance. The TEM test shows the amorphous carbon around the surface of the particles. In the potential range of 3.0–4.3V, the initial discharge capacity is 129.1mAh/g at 0.1C which is almost near the theoretical capacity, and it keeps so fairly stable that a discharge capacity of more than 125mAh/g can still be held after 50 galvanostatical cycles. It also exhibits an excellent rate capability with high discharge capacities of more than 108mAh/g at 2C after 100cycles.
Manganese (Mn)-based cathodes with advantages of low-cost, environmental benign, high energy density are crucial for the commercial process of sodium ion batteries (SIBs). Layer-tunnel hybrid cathode, which aims to integrate high capacity of P2-type layered structure with excellent cycling stability, superior rate performance of tunnel structure, deserves great research efforts. To further enhance the respective performance, the ratio of layer-tunnel component in the hybrid Na0.6Mn1-x Ni x O2 was adjusted by a simple cationic Ni2+ doping route. The crystal structure and electrochemical behavior of Na0.6Mn1-x Ni x O2 were carefully detected, compared and analyzed. The comprehensive results evidenced that the layered component ratio would rapidly increase with Ni2+ doping. The structural parameters of pure phase would also be affected by varied Ni2+ content. And 5% Ni doping could be an optimized point in terms of reversible capacity, cycling stability, rate performance and reaction kinetics. This study would reveal the dual-function of cationic doping in both macro scale component ratio and atomic scale crystal lattice parameter, and grasp new insight into the design and optimization of high performance hybrid cathode for SIBs.
The Na2Co[Fe(CN)6] nanoparticles with a low content of Fe(CN)6 defects and coordinating water are synthesized by a facile electrostatic spray assisted coprecipitation (ESAC) method. X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, elemental analysis and galvanostatic cell cycling are used to characterize the structure and electrochemical performance of the Na2Co[Fe(CN)6] nanoparticles. The results show that the structure and electrochemical performance of the Na2Co[Fe(CN)6] electrodes are influenced significantly by the content of Fe(CN)6 defects and coordinating water. Na2Co[Fe(CN)6] nanoparticles obtained by ESAC method exhibit excellent electrochemical performance, which deliver a high initial coulombic efficiency of 89.3%, stable cycling performance with a reversible capacity of 104 mAh g−1 after 100 cycles and high rate capability of 75 mAh g−1 at 500 mA g−1.
Thermodynamics experiment and study were carried out for the lithium-ion (Li-ion) batteries that are expected as the power sources for electric and hybrid vehicles. It is confirmed that the heat coming in and going out depend on charging and discharging, respectively. And the thermal generation factors will be decomposed to three elements: reaction heat value Q r, polarization heat value Q p, and Joule heat value Q J. Furthermore, the contribution degree of each factor was able to be expressed quantitatively by dividing these thermal generation factors for charging and discharging. The accuracy of thermodynamics logic was verified since the thermodynamics calculation coincided with the experimental data of thermal generation for the practical Li-ion batteries for electric vehicles (EV). It is possible to utilize the calculation and simulation for the development of Li-ion battery and the establishment of thermal control technology not only for EV but also for hybrid electric vehicles (HEV).