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The cathode materials of Li1+x Ni0.25Mn0.75O2.25+x/2 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) with different content of lithium have been synthesized in this paper. The materials with different lithium content show distinct differences in structure and charge/discharge characteristics. The layered-spinel composite structure has been detected in the Li1+x Ni0.25Mn0.75O2.25+x/2 electrodes, when the lithium content is lower than 1.5. The coulomb efficiency of Li1+x Ni0.25Mn0.75O2.25+x/2 electrode is increased with the content of lithium decreasing. The cyclic and rate performances of layered-spinel composite electrodes Li1+x Ni0.25Mn0.75O2.25+x/2 (0 ≤ x ≤ 0.4) are better than that of layered Li1.5Ni0.25Mn0.75O2.5. Among the layered-spinel composite electrodes, Li1.3Ni0.25Mn0.75O2.4 electrode shows the best capacity retention (98.2% for 40 cycles) and rate capacity (102 mAh g−1 at 10 C), while that of Li1.5Ni0.25Mn0.75O2.5 are 94.5% for 40 cycles and 11 mAh g−1 at 10 C. Electrochemical impedance spectroscopy (EIS) results show that the charge transfer resistance (R ct) of Li1.3Ni0.25Mn0.75O2.4 electrode is lower than that of Li1.5Ni0.25Mn0.75O2.5. The enhanced cyclic and rate performances of Li1.3Ni0.25Mn0.75O2.4 cathode are attributed to the lower R ct, three-dimensional interstitial space of LiNi0.5Mn1.5O4 phase and the lower content of Li2MnO3 in Li1.3Ni0.25Mn0.75O2.4 cathode material.
Abstract Security officers will learn all about the different aspects surrounding parking and traffic control. Properly using personal protective equipment, retro-reflective vests, and personal traffic control equipment are topics of discussion. Controlling vehicles and pedestrians is also highlighted in this chapter.
In this work, three-dimensional (3D) tubular molybdenum disulfide (MoS2)/PPy composites have been prepared, in which the MoS2 is as the framework to promote the insertion and extraction of electrolyte ions, and PPy spherical particles or nanowires are synthesized by an in-situ oxidative polymerization method in the presence of the MoS2. FT-IR, XRD, XPS, FESEM and HRTEM are used to characterize the structures and morphologies of the as-prepared materials. The combination of conductive PPy and 3D tubular MoS2 leads to a significant synergistic effect. For MoS2/PPy particle composites, the best performance (specific capacitance of 350F/g at a current density of 1A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS2 being 2:1. While for MoS2/PPy nanowire composites, the best performance (specific capacitance of 462F/g at 1A/g and a good cycling stability of 82% after 2000 cycles at 3A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS2 being 5:1, which shows much better supercapacitor performance than the MoS2/PPy composite. Moreover, the composite electrode material delivers an energy density as high as 25.5 Wh/kg at a power density of 266.3W/kg and maintains 14.5 Wh/kg at a high power density of 4002W/kg. These performances feature the composite as advanced negative electrode materials and are superior to previous reports.
The combination of LiMn0.67Fe0.33PO4 positive and Li4Ti5O12 negative electrode is studied in terms of its entropy change behavior, which affects the reversible heat generation of a lithium-ion cell. This electrode combination is especially interesting for large applications, as it is proposed to be a very safe choice having still an adequate energy density. The entropy change of LiMn0.67Fe0.33PO4 and Li4Ti5O12 electrode materials is measured at different states of charge using a potentiometric method. The results are compared with conventional electrode materials, LiFePO4 and artificial graphite. The entropy change of LiMn0.67Fe0.33PO4 is found to follow the distinct plateaus of Fe2+/Fe3+ and Mn2+/Mn3+ redox couples and to be clearly different from LiFePO4. This difference is suggested to be due to single-phase solid solution regions, originating from effects of substituting Mn for Fe. For Li4Ti5O12, mostly a constant entropy change typical for a two-phase reaction is observed, except for the region near 0% state of charge. The data from individual electrodes is used to simulate and compare the entropy change behavior and thus the reversible heat generation rate of different electrode combinations.
ABSTRACT Co3O4 nanofibers are prepared by electrospinning technique and they are characterized by thermogravimetry analysis (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) studies. BET analysis revealed that Co3O4 nanofibers have high specific surface area. Electrochemical properties of the electrospun Co3O4 nanofibers electrode performance are characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements in a 6M KOH electrolyte using a three-electrode system. The electrospun Co3O4 nanofibers exhibit a specific capacitance of 407Fg−1 at a scan rate of 5mVs−1. Futhermore, the Co3O4 nanofibers show an excellent cycle stability and better capacity rentation with 94% after 1000 continuous charge-discharge cycles at a constant current density of 1 Ag−1. Moreover, the enhanced supercapacitor performance is mainly due to its unique nanofibers structure provides larger reactive surface area capable of fast ion and electrone transfer. The results are compared with the existing reported systems in the literature.
Graphene oxide/polypyrrole nanowire composite material (GO/PPy) is synthesized using an in situ chemical polymerization method. The field-emission scanning electron microscope (FE-SEM) and transmission electron microscopy (TEM) results demonstrate that the PPy nanowires with 40 nm in diameter are uniformly dispersed on the surface of GO nanosheets, which greatly increases the surface area of the material and the charge transfer reaction. This two-dimensional structure exhibits better electrochemical performance than the pure individual components. According to the galvanostatic charge/discharge analysis, the GO/PPy composite has a good supercapacitive performance with a specific capacitance of 728 F g−1 at a discharge current density of 0.5 A g−1, higher than that of PPy nanowires (251 F g−1). At a discharge current density of 2.5 A g−1, the GO/PPy composite also has a high specific capacitance of 675 F g−1. Significantly, the GO/PPy electrode shows excellent cycling stability (7% capacity loss after 1000 cycles) due to the GO layer releasing the intrinsic differential strain of PPy chains during long-term charge/discharge cycles.
The same experimental techniques as used earlier to characterize the composition and properties of the so-called solid electrolyte interphase (SEI) layer formed at the graphite-anode–electrolyte interface of a Li-ion battery are used here to acquire some degree of understanding of interface phenomena occurring on the cathode side of the cell, even though the validity of the SEI-layer concept is still somewhat tenuous in this “cathode” context. We here probe cathode-related SEI phenomena for the three cases: LiMn2O4, LiCoO2/LiNi0.8Co0.2O2, and carbon-coated LiFePO4. The various layer types formed have been analyzed systematically for different salts, solvents, cycling modes, storage times, temperatures, etc., using photoelectron spectroscopy (PES). Depth-profiling of the layers formed was achieved using Al Kα radiation in conjunction with Ar-ion sputtering; non-destructive depth-profiling was made possible using synchrotron radiation, and applied to the important case of carbon-coated LiFePO4. A number of trends have emerged from our studies, and some general models are proposed to reflect features characteristic of the various systems studied. Our results are related to the more familiar SEI-layer formed on graphite.
Instruments for monitoring the clinical status of adolescents with emotional problems are needed. The Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM) according to theory measures problems/symptoms, well-being, functioning and risk. Documentation of whether the theoretical factor structure for CORE-OM is applicable for adolescents is lacking.
Nitrogen-doped amorphous mesoporous hollow carbon nanospheres are prepared through the unique polymerization reaction between 3-aminophenol and formaldehyde, the selective removal effect of acetone as well as a simple carbonization process. Ultrafine TiO2 nanocrystalline with average size of 7.4 nm are further uniformly, sparsely, tightly anchored onto hollow carbon nanospheres through hydrolysis deposition of titanium tetraisopropanolate followed by a controllable crystallization. As anode material for lithium ion batteries, TiO2@hollow carbon nanospheres exhibit high charge-discharge capacity, stable cycling performance and excellent rate capability. The average discharge capacity over 200 cycles at 1C is 242 mAh g−1, 2C and 5C are 188 and 170 mAh g−1. After rate test and subsequent 1500 continuous cycles at 10C, TiO2@hollow carbon nanospheres still deliver discharge capacity of 146.1 mAh g−1 with a high capacity retention of 80.6% and a very low capacity decay of 0.012% per cycle. The superior lithium storage properties should be attributed to synthetic effects of ultrafine TiO2 nanocrystalline and hollow carbon nanospheres. This work can give rise to the new understanding about design and synthesis of next-generation, high-power TiO2-based advanced anode for lithium ion batteries.
Multi-walled carbon nanotube (MWCNT)/MnO2 supercapacitor electrodes containing MnO2 nanoflakes in the MWCNT network are fabricated through the oxidation of manganese acetate with poly(4-styrenesulfonic acid) (PSS) dispersed MWCNTs. The structural evolution of the electrodes under charge/discharge (reduction/oxidation) cycles and its impact on the electrodes’ electrochemical properties are evaluated. Structural evolution involves the dissolution of MnO2 upon reduction, the diffusion of the reduced Mn species from the MWCNT network toward the electrolyte solution, and the deposition of MnO2 on the electrode surface upon oxidation. Electrode structural changes, including the electrode dissolution and the growth of the MnO2 crystals, are scan rate dependent and have deteriorating effect on the electrode's electrochemical properties including the specific capacitance and cyclic stability.
The influence of some organic expanders on the formation of lead-sulphate has been studied by means of potentiostatic transients. The experimental data have been discussed according to the theories which have been proposed in the literature for the electro-crystallisation of lead-sulphate and lead. The discussion of the data obtained confirms the inhibiting effect of the expanders on lead sulphation. In fact, the tests showed that, when the expanders are added to the electrolyte, a longer time is required to reach the current maximum of the i(t) curve and a reduction of its intensity. According to the theoretical interpretation, this finding indicates a decreasing of the kinetic constant of the solid state process. The analysis of the i(t) transients obtained during the sulphate reduction revealed an influence of expanders only when the sulphate layers has been formed in their presence. Thus, it seems that the adsorption of the organic expanders on lead is of primary importance for their action while adsorption on lead-sulphate appears to be negligible.
With the aim of increasing the self-consumption rate of grid-connected Photovoltaic (PV) home systems, two main options can be implemented: the inclusion of an energy storage system, in particular a battery bank, and the adoption of a Demand Side Management (DSM) strategy. However, both the reshaping of the load consumption curve with the displacement of deferrable loads and the optimal management of the battery bank require estimation of the daily PV generation profile. The assessment of the on-site energy production can be carried out based on weather forecast data. However, the latter are characterized by uncertainty, which may affect the achievable self-consumption rate. This work investigates the influence of weather forecast errors on the performance of home PV systems equipped with a battery bank and characterized by a certain share of deferrable loads. Two different weather forecast services are considered, referring to the annual meteorological conditions occurring in Rome, and energy consumption data for 150 different households are analysed. The self-consumption rate is maximized by solving a suitable optimization problem, while different combinations of relative battery capacity, PV-to-load ratio and share of deferrable loads are considered. Two different approaches—deterministic and stochastic—are adopted and compared with an ideal approach where the PV generation profile is perfectly forecasted. The results show that the adoption of the deterministic approach leads to a reduction in the achievable self-consumption rate in the range of 0.5–4.5% compared to the ideal approach. The adoption of a stochastic approach further reduces the deviations from the ideal case, especially in the case of consumption profiles with a high share of deferrable loads. Finally, a preliminary economic analysis proves that the use of a battery bank is not yet a cost-effective solution and a price reduction of the current battery prices is therefore required.
Renewable energy based power generation system holds the most promising solution for remote area power supply. In this study, the long term operation performance of a 19.8kWp standalone solar photovoltaic (SAPV) system in a remote island is investigated. The methodology for evaluating system performance is introduced, and then the detailed assessment results are presented, accompanying with analysis and discussion. Results show that the photovoltaic (PV) array operated well with AC power generation efficiency of about 10% and overall system efficiency is about 7.7%. The reference yield, array yield and final yield are 4.08, 3.05, and 2.45kWh/kWp/day, respectively, therefore the resultant performance ratio is 60%, demonstrating that the performance of SAPV plant is satisfactory during the reporting period. However, after long term performance monitoring and analysis, the limitation of SAPV system begins to arise due to lack of grid management and compensations from other energy sources, suggesting that it would be better to develop or integrate it into a microgrid system with hybrid sources if possible.
Na0.44MnO2 has aroused global interest as a promising cathode material for sodium ion batteries due to its unique tunnel structure. Rod-like Na0.44MnO2 is synthesized here via a simple, fast and environment-friendly oxalate precursor-based process, and the electrochemical performances, as well as the structural evolution within the electrode redox process and the chemical mechanism for material synthesis, are systematically investigated. The Na0.44MnO2 material prepared at 900 °C for 3 h (denoted as NMO-9003) possesses the highest reversible capacity of 120 mAh g−1 at 0.2 C and an optimal rate capacity of 106 mAh g−1 at 1 C, while its long-term capacity retention is 86% after 500 cycles at 20 C, indicating superior structural reversibility. In addition, the NMO-9003 sample shows the fastest cationic diffusion rate at approximately 1.2 × 10−13 cm2 s−1. The density functional theory (DFT)-based calculation is adopted to explore the lattice variation of Na0.44MnO2 upon the electrode process, which confirms that the host structure bears a minor volume change approximately 7% from 2.0 to 3.8 V, well demonstrating the origin of excellent reversibility.
We report the decoration of commercial graphite microspheres (GMs) with Si particles as anode materials for Li-ion batteries. The Si particles are obtained from solid Si waste of organosilane industry that is acid-washed to remove the impurities and further ground. The GMs with a size of 5–40 μm as main active material, Si particles with a size of 1–10 μm as an additive, and sucrose dissolved in water as a binder are mixed and followed by carbonization to obtain Si/C composites containing graphite, Si, and amorphous carbon generated from sucrose. It is found that the composite containing 60.5 wt% of GMs, 22.1 wt% of Si, and 17.4 wt% of amorphous carbon obtained at 800 °C for 5 h shows the best electrochemical performance with a specific capacity of 522.6 mA h g−1 at the current density of 50 mA g−1 and 306.9 mA h g−1 at 500 mA g−1, much higher than those of GMs. Its capacity retention at 500 mA g−1 attains 93.9% after 20 cycles. The work demonstrates the possibility for utilization of the industrial Si waste to enhance graphite anode materials in Li-ion batteries.
The electrochemical performance of a novel all solid-state sodium-ion symmetrical battery with Na3Zr2Si2PO12 (NASICON) as a solid electrolyte and Na3V2(PO4)3 (NVP) as the active electrode material was examined. The all solid-state cell was fabricated by a combination of screen printing and hot pressing. The electrochemical characterization of the NVP active material in the metallic sodium half-cells at 80°C indicated that this NASICON-related phosphate undergoes reversible sodium extraction/insertion reactions at electrode potentials of 1.6 and 3.4V vs. Na. These insertion properties allowed the NVP to function successfully as the active material for both the positive and negative electrodes in a sodium-ion cell configuration. A charge–discharge cycling test of the fabricated symmetrical all solid-state cell was carried out at room temperature within the voltage range of 0.01 and 1.9V. It was found that the cell can work as a secondary battery and showed first discharge capacities of 68 and 32mAhg−1 at the current densities of 1.2 and 10μAcm−2, respectively. Furthermore, the lack of reactivity between the all-solid-state cell components during long-term cycling was confirmed.
Recently, metal organic framework (MOF) materials in nano-scale have gained enormous interest in Li-ion batteries (LIBs), while those in bulks usually exhibit poor Li-ion storage performance. Herein, we report how to obtain impressive Li-ion storage performance by using MOF bulks firstly. Through suitable design, incorporating small inorganic nano-domains with various dimensions into the MOF bulks, the forming metal inorganic-organic hybrid composites (M-IOHCs) could store Li-ions twice more than that of the metal based MOF (M-MOF) bulks. Except for the good Li-ion storage performance, exemplified M-IOHCs also exhibit enhancing cyclibility of more than 400 cycles with tripled capacity and 100% capacity retention. The enhanced Li-ion storage capability and cyclibility is attributed not only to local phase segregation in MOF bulks induced by ultra small inorganic nano-domains and the self-nano-crystallization of MOF bulks and the later forming inorganic nanocrystals themselves, but also to the stabilized frameworks comprised of metal oxide inorganic nanocrystals and enwrapped C-N organic species which brought up no aggregation or grow-up of the inorganic active materials common in new generation electrode materials. Application of the M-IOHCs in full cells was exemplified by Ni-IOHCs anode and commercial LiFePO4 cathode, which delivers excellent energy and power performance.
This paper describes a flexible and lightweight fabric supercapacitor electrode as a possible energy source in smart garments. We examined the electrochemical behavior of porous carbon materials impregnated into woven cotton and polyester fabrics using a traditional printmaking technique (screen printing). The porous structure of such fabrics makes them attractive for supercapacitor applications that need porous films for ion transfer between electrodes. We used cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy to study the capacitive behaviour of carbon materials using nontoxic aqueous electrolytes including sodium sulfate and lithium sulfate. Electrodes coated with activated carbon (YP17) and tested at ∼0.25 A·g−1 achieved a high gravimetric and areal capacitance, an average of 85 F·g−1 on cotton lawn and polyester microfiber, both corresponding to ∼0.43 F·cm−2.
La0.8GdxMg0.2Ni3.15Co0.25Al0.1 (x = 0–0.4) hydrogen storage alloys are prepared by induction melting followed by annealing treatment at 1173 K for 8 h. The effects of non-stoichiometry on phase structure and electrochemical properties with Gd addition are investigated systematically. The results show that Gd addition exerts significant effects on the phase component of the alloys. A appropriate amount of Gd addition (x = 0.1) can increase the abundance of (La,Mg)2Ni7-type phase while that of (La,Mg)5Ni19-type phase decreases. The further increase of Gd content (x ≥ 0.2) results in appearance of (La,Mg)Ni3-type, (La,Mg)7Ni16-type and La2MgNi2-type phases. Electrochemical tests reveal that the maximum discharge capacity and cycle life of the alloy electrodes can benefit from the right amount of Gd addition (x = 0.1), both of which are deteriorative with further increasing Gd content. However, the excess amount of Gd (x ≥ 0.2) jeopardizes the high rate dischargeability of the alloy electrodes obviously owing to the increase of charge transfer resistance on alloy surface.
The anodic behaviors of aluminum current collector for lithium ion batteries were investigated in a series of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide room temperature ionic liquids (RTILs) and EC+DMC electrolytes. It was found that the aluminum corrosion, which occurred in EC+DMC electrolytes containing LiTFSI, was not observed in the RTIL electrolytes. Further research showed that a passive film with amide compounds as main components formed firmly on aluminum surface during the anodic polarization in the RTIL electrolytes, which inhabited the aluminum corrosion. In addition, the additives generally used in the batteries, such as ethylene carbonate, ethylene sulfite and vinyl carbonate, as well as temperature did not obviously affect the aluminum passive film, the oxidation of the RTILs increased at the elevated temperature, which only resulted in the corrosion potential of aluminum in the RTIL electrolytes shifted to more negative potential, a passive film still firmly formed on the aluminum surface to surpassed the further oxidation of the aluminum current collector. Those results lead to a potential for the practical use of LiTFSI salt in the room temperature ionic liquid electrolytes for lithium ion batteries.
Wind energy is rapidly growing in recent years. Among different types of wind turbines, due to several advantages, permanent magnet synchronous generator (PMSG) is attractive concept. Since the penetration level of wind power in the grid is increased, therefore, wind power can influence to the grid and vice versa. Some of the important problems in the grid are fault condition and voltage sags. These conditions may affect the operation of wind turbine. In order to enhance low voltage ride through (LVRT) capability in PMSG-based wind turbines, various approaches have been proposed in the last years. In this paper, the review and comparison of several LVRT capability enhancement methods is performed. The two foremost types of LVRT capability enhancement methods are external devices based methods and modified controller based methods. The main objectives of this paper are to introduce performances of different LVRT capability enhancement methods and use of some LVRT capability enhancement methods in PMSG based wind turbine which are applied in other kind of wind power generators. The external devices based methods can be effective but some of these methods are of significant cost. According to the literatures, modified controller based methods can reduce the LVRT capability enhancement cost. Several modified controller based methods have been proposed for LVRT capability enhancement. To compare the mentioned methods, several simulations are performed in MATLAB software. From the review of simulation results, series connection of FACTS devices and modification of back-to-back converter controllers are the highly efficient LVRT capability enhancement approaches.