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The performance of a Li polymer primary cell with fire-retardant poly(acrylonitrile) (PAN)-based gel electrolytes is reported. By optimizing electrodes, electrolytes, the packaging material, and the structural design of the polymer cell, we succeeded in developing a “film-like” Li polymer primary cell with sufficient performance for practical use. The cell is flexible and less than 0.5mm thick, which makes it suitable for a power source for some smart devices, such as an IC card. Fast cation conduction in the gel electrolyte minimizes the drop of the discharge capacity even at −20°C. The high chemical stability of the gel electrolytes and the new packaging material allow the self-discharge rate to be limited to under 4.3%, which is equivalent to that of conventional coin-shaped or cylindrical Li-MnO2 cells.
This study investigated the pattern of acute cognitive function of an ecologically valid sample of 58 consecutively admitted adults completing a 24 day residential/day substance use disorder treatment program at a Veterans Affairs Medical Center and its change over the 24 days of monitored abstinence. Participants were assessed at entry with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) Form A and at treatment conclusion with the RBANS Form B and with the Similarities subtest of the Wechsler Adult Intelligence Scale-III (WAIS-III) and the Trail Making A and B tests at both time points. There were significant (p < 0.002) improvements in the RBANS Immediate Memory, Attention, and Total Index scores over the course of treatment and on the Similarities subtest and the Trail Making A and B tests with effect sizes ranging between 0.37 and 0.56. There was greater cognitive performance increase for participants in the lower versus upper quantiles at treatment entry on all cognitive measures.
The IR voltage drop from the anode and cathode of Li-ion capacitors during charge and discharge was studied. Li-ion capacitors were made with activated carbon cathode and hard carbon anode with different loadings of stabilized lithium metal powder (SLMP). It was found that the LICs with high SLMP loadings showed smaller voltage drop than LICs with low SLMP loadings. It was also found that at low SLMP loadings, the IR voltage drops at high cell voltages were smaller than that at low cell voltages; while at high SLMP loadings, small IR voltage drops were obtained for both low and high cell voltages. The electrochemical impedance spectroscopy confirmed that voltage drops are directly related to the internal resistances of Li-ion capacitors.
We report on the strategy of Cu doping inducing the nanosize effect of CoO and their application as anode for lithium ion batteries. With an increase of Cu-doped amount, the structures and morphologies of CoO have special changes. The 0.05 mol Cu-doped CoO shows straw-like bundle structure assembled by nanorods, and the nanorods consist of ultra small nanoparticles (about 6–8 nm). Meanwhile, it shows an excellent rates performance and cycle life. The capacity of 800 mA h g−1 is obtained at 0.5 C after 80 cycles. The highest discharge capacity is 580 mA h g−1 at 10 C and the discharge capacities are relatively stable for 1000 cycles as an anode for Li-ion battery. Therefore, the controllable Cu-doped CoO composite could be deemed to be a potential candidate as an anode material.
Three types of SnO2/TiO2 composite nanofibers (homogeneous SnO2/TiO2, heterogeneous SnO2/TiO2 and SnO2 NPs/TiO2) have been prepared via a facile electrospinning method combined with a sol-gel chemistry, whose electrochemical performance as anode materials in lithium-ion battery was evaluated and compared to that of pure TiO2 and SnO2electrospunnanofibers (NFs). Rutile phase TiO2nanofibers demonstrated an extremely stable but relatively low gravimetric specific capacity of ∼80 mAh g−1 when discharged at 100mAg−1. In contrast, rutile phase SnO2nanofibers showed a much more unstable but higher specific capacity, which dropped from initial 800 to ∼35 mAh g−1 after 50 cycles. The incorporation of structurally unstable SnO2 into stable TiO2 matrix can significantly improve both the cycling performance and specific capacity. These composite nanofibers possess a much higher initial gravimetric specific capacity (>500 mAh g−1) than rutile phase TiO2nanofibers and maintain superior capacity retention to pure SnO2 NFs. The enhanced cycling stability is attributed to the space confinement provided by the structurally stable TiO2, which finding can provide a beneficial guidance for future lithium ion battery electrode development.
Carbon-coated CaWO4 nano-crystalline phases have been synthesized by ambient temperature solution precipitation method, characterized by X-ray diffraction, SEM and thermogravimetry and their electrochemical properties were studied versus Li metal. Galvanostatic cycling at a current of 60mA/g in the voltage range 0.005–3.0V on the 5wt.% C-coated CaWO4 gave a reversible capacity of 230±5mAh/g corresponding to 2.5mol of Li, which is almost stable from 20 to 50 cycles. Under the same conditions, the 10wt.% C-coated CaWO4 showed a capacity of 355±5mAh/g (3.8mol of Li) during the initial cycles, but the capacity degraded at a rate of 1.6mAh/g per cycle in the range 5–100 cycles. A good operating voltage range was found to be 0.005–3.0V with average discharge and charge potentials being 0.6 and 1.3V, respectively. Coulombic efficiency in all cases was 96–98%. Cyclic voltammograms compliment the galvanostatic results. Impedance spectral data on the 10wt.% C-coated CaWO4 at different voltages during the first and 20th discharge–charge cycle have been interpreted in terms of the variations in the bulk and charge-transfer resistances of the composite electrode. A reaction mechanism involving the formation/decomposition of the oxide bronze, ‘Li x WO y ’ has been proposed to explain the electrochemical cycling.
Although (CF x ) n has the highest theoretical specific energy of all lithium primary batteries known, the practical specific energy (including packaging) is very small on the order of ∼10% for small capacity cells (<5Ah) and between 20 and 30% for large capacity cells (>100Ah). Even these can be achieved only at a very low discharge rate <C/250 (250h rate). If either the discharge rate is increased or the discharge temperature is reduced below 0°C the % delivered energy goes down even further. At Sandia National Laboratories we are performing research to improving % delivered energy by: (1) incorporating engineering solution and (2) adopting a new chemical approach. The engineering solution effort will not be discussed here except to mention that light weight metal such as titanium (Ti) will be considered for hardware instead of stainless steel. The chemical approach involves adding an anion-binding-agent (ABA) to the electrolyte solution to dissolve the LiF generated in the discharge reaction. We studied three boron containing neutral ABAs and the most promising ABA {Tris(1,1,1,3,3,3-hexafluoroisopropyl)borate} will be discussed further. The delivered capacity/energy (per unit weight of the cathode) is higher for SNL-built coin cells containing the ABA additive than for the commercial coin cells by 80%. These cells were tested at a C/44 rate. This improvement especially at a high discharge rate is attributed to the ability of the ABA to dissolve the LiF from plugging the cathode pores and thus keep the bulk of the cathode accessible for further discharge reaction. We have also tested commercial cells and commercial electrodes in coin cells. In general, at high rate discharge, the performance of SNL cells containing our electrolyte and electrode were better than the rest.
The aim of the study was to examine the various design features of ventilated garments on cooling performance. Five jackets with small ventilation units and closable openings were designed. The ventilation units with a flow rate of 12 l/s were placed at five different torso sites. They were examined on a sweating thermal manikin in four clothing opening conditions in a warm environment (T a = T manikin = 34 °C, RH = 60%, V a = 0.4 m/s). Total torso cooling was increased by 137–251%, and clothing total dynamic evaporative resistance was decreased by 43–69%. Neither the ventilation location nor the opening design had a significant difference on total torso cooling. The ventilation location had a significant difference on localized intra-torso cooling, but not the opening design. When the ventilation units were placed at the local zone where it was ventilated, that zone underwent the highest cooling than other local zones. The study indicated that the ventilation units should be placed at the region where it required the most evaporative cooling, e.g. along the spine area and the lower back. The openings could be adjusted (closed or opened) to make comfortable air pressure for the wearers but without making significant difference on the whole torso cooling under this flow rate. Relevance to industry Heat strain is frequently reported in hot environments, especially for those industries, such as construction, mining and steel. Clothing equipped with the small ventilation units could circulate the ambient air around the body and thus decrease heat strain and improve productivity.
Due to the energy crisis within recent decades, renewable energies such as solar, wind and tide energies have received a lot of attention. However, these renewable energies are dependent on the time and season. Consequently, energy storage systems are needed to fully utilize these energies including their connection with smart grids. Aqueous rechargeable lithium batteries (ARLBs) may be an ideal energy storage system due to its excellent safety and reliability. However, since the introduction of ARLBs in 1994, the progress on improving their performance has been very limited. Recently, their rate performance, especially superfast charging performance, reversible capacity and cycling life of their electrode materials were markedly improved. The present work reviews the latest advances in the exploration of the electrode materials and the development of battery systems. Also the main challenges in this field are briefly commented on and discussed.
The performance of cathodes for lithium-air cells is evaluated from an automotive perspective. Unique aspects of this work include the following. Novel cathode structures are fabricated to improve cell performance operating on air. Convective air flow, critical to automotive operation, is used to evaluate cathode performance, and techniques to mitigate the resulting solvent evaporation from the electrolyte are discussed. The peak power is measured using the standard USABC test procedure, a benchmark for evaluating automotive performance. The importance of the kinetic, ionic, and mass transfer impedances as a function of discharge current density is identified using Tafel slopes, reaction orders, and electrochemical impedance spectroscopy (EIS) data. The distinct processes in the EIS data are identified as the anode–separator interface and the cathode. For the lithium-air cells used in this work, the discharge is controlled by a combination of the ionic transfer impedance at the anode–separator interface and the kinetic and mass transfer impedances in the cathode. Finally, impedance data establish the importance of performing EIS during discharge, not at open circuit voltage, to accurately determine the processes controlling the discharge reaction. The implication of these results to automotive applications for lithium-air batteries is discussed.
Photoplethysmography can be used for measuring oxygen saturation or assessing autonomic function. Artifacts can render the photoplethysmogram (PPG) useless. Thus, algorithms capable of identifying artifacts are important. However, the published algorithms are limited in their abilities and study design. Therefore, the authors developed a novel embedded algorithm for pulse waveform (PWF) segmentation and artifact detection in real-time.
The electrocatalytic reduction of protons in 1.0M perchloric acid at glassy carbon electrodes anodically modified with a Co(II)/Pt(II) porphyrin show shifts of 400mV versus Ag/AgCl when compared to the same electrodes which have not been anodically modified. Anodic cycling of glassy carbon electrodes coated with the Co(II)/Pt(II) porphyrin in this study form stable electroactive films capable of improving both electroreduction of protons to hydrogen and oxygen to both peroxide and water. Electrooxidation of glassy carbon electrodes coated with the free base porphyrin show no improvement in catalytic ability for the reduction of protons in acidic solution or the reduction of molecular oxygen in basic solution. Glassy carbon electrodes coated with the Co(II)/Pt(II) porphyrin indicate, by rotating disk electrochemistry, that the electrocatalysis of oxygen is a two electron process leading to the formation of hydrogen peroxide. Koutecky–Levich plots of the data obtained from the reduction of oxygen at electrode surfaces coated with the Co(II)/Pt(II) porphyrin after oxidation of the surface indicate that 25% of the oxygen is reduced by four electrons directly to water while 75% of the oxygen is reduced by two electrons to hydrogen peroxide.
Fe3O4-reduced graphene oxide (rGO) composites have been synthesized via an ethylene glycol-mediated solvothermal-polyol method. The electrochemical performances of the as-prepared Fe3O4-rGO electrode and alumina (Al2O3) film coated Fe3O4-rGO electrode using atomic layer deposition (ALD) were investigated. The results indicated that the ALD coating of Al2O3 greatly improved the electrochemical properties (especially cycling stability) of Fe3O4-rGO composite electrode as an anode for lithium-ion battery (LIB), resulting in the increase of reversible capacity from 94.1mAhg−1 to 717.4mAhg−1 after 200 cycles. The Al2O3 films retain sufficiently integral to limit the excessive growth of the interfacial layer between Fe3O4 and electrolyte, which in turn improves the electrochemical kinetics at the electrode/electrolyte interface and maintains a relatively stable interfacial resistance during whole discharge/charge cycles. The results presented in this study pave a new way to improve the stability of nanostructured anodes for LIBs.
A novel manganese hexacyanoferrate/multi-walled carbon nanotubes (MnHCF/MWCNTs) nanocomposite was fabricated by mild chemical precipitation method at room temperature and further investigated as electrode materials for supercapacitors. The physical properties of as-fabricated materials were characterized by XRD, FTIR and FE-SEM techniques. Integrating these nanostructures resulted in a strong synergistic effect between the two materials, consequently leading to robust and superior composite materials with higher capacity compared with pure MnHCF and MWCNTs. Specific capacities of 370.4, 200.1 and 45.8 C g−1 were acquired for MnHCF/MWCNTs nanocomposite, MnHCF and MWCNTs, respectively. Most importantly, as-fabricated MnHCF/MWCNTs nanocomposite exhibited favorable rate capability (370.4 C g−1 and 270.6 C g−1 at 1.0 A g−1 and 6.0 A g−1, respectively) and excellent cycling stability (87.4% capacitance retention after 2000 cycles at 1.0 A g−1). The simple synthesis and excellent electrochemical properties made as-fabricated nanocomposite an attractive candidate in the fields of supercapacitors and new emerging areas.
The state-of-the-art graphite anode containing a small portion of silicon represents a promising way of applying high-capacity alloy anode in the next generation high energy density lithium-ion batteries. The conductive polymeric binders developed for Si anodes proved to be an effective binder for this graphite/nanoSi composite electrode. Without any acetylene black conductive additives in the electrode, a high areal capacity of above 2.5mAh/cm2 is achieved during long-term cycling over 100 cycles. This conductive polymer-enabled graphite/nanoSi composite electrode exhibits high specific capacity and high 1st cycle efficiency, which is a significant progress toward commercial application of Si anodes.
There is interest in developing a suitable battery system that can be used at temperatures of 250 °C or less to power instrumentation used in oil/gas and geothermal boreholes. The discharge performance of MnO2 cathodes with Li–Mg–B alloy anodes is examined using the LiNO3–KNO3 eutectic electrolyte over a temperature range of 150 °C–300 °C at current densities from 10 to 30 mA cm−2. In this study, we find that the cell can be activated at 150 °C and operate within the desired temperature range without any indication of possible hazards. However, we did observe that temperature and current density significantly affected cell capacity and voltage. Overall, the Li–Mg–B alloy/LiNO3–KNO3/MnO2 system shows great potential for powering instrumentation used in oil/gas and geothermal boreholes.
PVdF/SiO2 composite nonwoven membranes exhibiting high safety (thermal stability), high ionic conductivity and excellent electrochemical performances are firstly prepared by electrospinning poly(vinylidene fluoride) (PVdF) homopolymer and silicon dioxide (SiO2) sol synchronously for the separators of lithium-ion batteries (LIBs). Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and hot oven tests show that the PVdF/SiO2 composite nonwoven membranes are thermally stable at a high temperature of 400 °C while the commercial Celgard 2400 PP membrane exhibits great shrinkage at 130 °C, indicating a superior thermal stability of PVdF/SiO2 composite nonwoven membranes than that of Celgard membrane. Moreover, the composite membrane exhibits fairly high ionic conductivity (7.47 × 10−3 S cm−1) that significantly improves the performance of LIBs. The PVdF/SiO2 composite membranes are also evaluated to have higher level of porosity (75−85%) and electrolyte uptake (571−646 wt%), lower interfacial resistance compared to the Celgard separator. The lithium-ion cell (using LiFePO4 cathode) assembled with the composite membrane exhibits more stable cycle performance, higher discharge capacity (159 mAh g−1) and excellent capacity retention which proves that they are promising candidates for separators of high performance rechargeable LIBs.
The electrochemical flow capacitor (EFC) is an electrical energy storage concept recently introduced for grid-scale energy storage applications. The EFC utilizes flowable carbon-based electrodes as the active material in a flow battery type architecture for capacitive storage and recovery of energy. Charged slurry can be stored in external reservoirs until it is needed, enabling scalable energy storage to satisfy a variety of large-scale applications. Here, the capacitance and conductivity of EFC slurry electrodes were measured as a function of flow rate (from 0 to 10 ml min−1) and flow cell channel depth (electrode ‘thickness’, ranging from 0.5 to 3 mm). The effect of salt concentration in the electrolyte was also explored. The interfacial resistance associated with the current collector|slurry interface was found to constitute a large portion of the total cell resistance. Bulk slurry conductivity was found to vary significantly with changes in electrolyte concentration, flow rate and channel depth. Very respectable capacitance values of up to ∼30 F ml−1 (150 F g−1) were obtained during intermittent flow operation. However, significant underutilization of the slurry due to increased ohmic losses at larger channel depths was observed, as evidenced by a rapid decay in capacitance with increasing channel depth.
The F-doped layered cathode materials Li1.05(Ni0.5Mn0.5)0.95O2−x F x (0≤ x ≤0.1) with ball-like shape were successfully synthesized by carbonate co-precipitation method, followed by a high temperature calcination process. The effects of fluorine content on the crystal structure, morphology and electrochemical performance were extensively investigated. The XRD results reveal that all the materials synthesized have typical hexagonal structure without impurity. Fluorine-doped materials could have improved cycling performance compared with Li1.05(Ni0.5Mn0.5)0.95O2, and Li1.05(Ni0.5Mn0.5)0.95O1.95F0.05 shows the best electrochemical property. In addition, 3wt% FePO4-coated Li1.05(Ni0.5Mn0.5)0.95O1.95F0.05 has significantly improved rate capability and better thermal stability compared with pristine sample. Electrochemical impedance spectroscopy (EIS) measurements reveal that both fluorine substitution and FePO4 coating could suppress the increase of charge transfer resistance with cycling. Overall, the combination of fluorine doping and FePO4 coating was effective in improving both cycling performance and rate capability of Li1.05(Ni0.5Mn0.5)0.95O2.
A kind of organic-inorganic nanocomposite of methacrylisobutyl-polyhedral oligomeric silsesquioxane (MA-POSS) is synthesized and the nanocomposite as the modified filler is introduced into polymethyl methacrylate (PMMA) matrix to prepare gel polymer electrolyte (GPE) membrane used in lithium ion battery (LIB) through phase inversion method combined with liquid electrolyte adsorption. The results reflect that compared to the solvent evaporation technique, the electrochemical performances of the GPE corresponding to the membrane prepared by phase inversion method are more outstanding. Besides, the membrane also shows good mechanical strength. Compared to the GPE based on pure PMMA matrix, the comprehensive performances of the modified GPE are also enhanced a lot and the GPE with the mass of 10% MA-POSS exhibits the most favorable properties. The excellent performances are shown as follows: the ionic conductivity reaches to 2.77 × 10−3 S cm−1 at room temperature; the lithium ion transfer number is up to 0.40; the GPE is electrochemical stable below 5.5 V (vs. Li/Li+); the compatibility between GPE and lithium anode is satisfying and the ionic conductivity obeys the Arrhenius behavior.
Miniaturized energy storage is essential for the continuous development and further miniaturization of electronic devices. Electrochemical capacitors (ECs), also called supercapacitors, are energy storage devices with a high power density, fast charge and discharge rates, and long service life. Small-scale supercapacitors, or micro-supercapacitors, can be integrated with microelectronic devices to work as stand-alone power sources or as efficient energy storage units complementing batteries and energy harvesters, leading to wider use of these devices in many industries. In recent years, the research in this field has rapidly advanced and micro-supercapacitors with improved storage capacity and power density have been developed. The important factors affecting the performance of micro-supercapacitors are the intrinsic properties of electrode materials and electrolyte, architectural design of the device and the fabrication methods. This paper reviews the recent advances in fabrication of materials and devices and provides a critical analysis of reported performances of micro-supercapacitors.
Copper oxide nanowires with an average length of 7.4μm are prepared by in-situ thermal oxidation at 500°C for 6h in air, and their lithium storage performances are promoted by a further ammonia treatment. The morphologies, structures and lithium storage properties of copper oxide nanowire arrays are investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and a series of electrochemical measurements. The results show that after the reprocessing, the CuO nanowire arrays exhibit a higher reversible capacity of 645 mAhg−1 after 100 cycles at a current density of 50 mAg−1, excellent cyclability and high-rate capability. The good electrochemical performance and simple preparation process make it a promising anode material for lithium-ion batteries.