batterydata/paper-abstracts huggingface dataset:
Li metal has been regarded as the most promising anode material for next high-energy batteries. However, the dendrite growth during the lithium deposition and low Coulombic efficiencies have restricted their practical applications. In the paper, we investigate the electrodeposition process of lithium metal under different current density in detail and firstly use diethylenetriamine as additive to adjust the deposition of lithium metal in LiPF6-PC and LiPF6-EC/DEC electrolyte. The result shows that trace diethylenetriamine can react with lithium anode producing R-N-Li and LiF, which greatly improves the morphology of lithium deposition by adjusting the components of the SEI film. The content of fast ionic conductors in SEI film (e.g., R-N-Li and LiF) can be identified by the X-ray photoelectron spectroscopy. The electrochemical impedance spectroscopy confirms diethylenetriamine could increase the ionic conductivity of the interface between the anode and electrolyte. Galvanostatic curves also show that the LiPF6-PC electrolyte with 0.2 vol% diethylenetriamine and LiPF6-EC/DEC electrolyte with 0.1 vol% diethylenetriamine has better cycling stability than blank group.
We present a fully analytical, heuristic model – the “Analytical Transport Network Model” – for steady-state, diffusive, potential flow through a 3-D network. Employing a combination of graph theory, linear algebra, and geometry, the model explicitly relates a microstructural network's topology and the morphology of its channels to an effective material transport coefficient (a general term meant to encompass, e.g., conductivity or diffusion coefficient). The model's transport coefficient predictions agree well with those from electrochemical fin (ECF) theory and finite element analysis (FEA), but are computed 0.5–1.5 and 5–6 orders of magnitude faster, respectively. In addition, the theory explicitly relates a number of morphological and topological parameters directly to the transport coefficient, whereby the distributions that characterize the structure are readily available for further analysis. Furthermore, ATN's explicit development provides insight into the nature of the tortuosity factor and offers the potential to apply theory from network science and to consider the optimization of a network's effective resistance in a mathematically rigorous manner. The ATN model's speed and relative ease-of-use offer the potential to aid in accelerating the design (with respect to transport), and thus reducing the cost, of energy materials.
In this study, synthetic graphite and carbon nanotube (CNT) filled polyphenylene sulfide (PPS) based bipolar plates are produced by using co-rotating twin-screw extruder and injection molding. Graphite is the main conductive filler and CNTs are used as bridging filler between graphite particles. To improve the dispersion of the fillers and the flow behavior of the composite, titanate coupling agent (KR-TTS) is used. The concentration effect of CNTs and coupling agent on the properties of bipolar plates are examined. At 72.5 wt.% total conductive filler concentration, by addition of 2.5 wt.% CNT and 3 wt.% KR-TTS; through-plane and in-plane electrical conductivities increase from 1.42 S cm−1 to 20 S cm−1 and 6.4 S cm−1 to 57.3 S cm−1 respectively compared to sample without CNTs and additive. Extruder torque value and apparent viscosity of samples decrease significantly with coupling agent and as a result; the flow behavior is positively affected. Flexural strength is improved 15% by addition of 1.25 wt.% CNT. Differential scanning calorimeter (DSC) analysis shows nucleating effect of conductive fillers on PPS matrix. Corrosion measurements, cyclic voltammetry and galvanostatic charge–discharge tests are performed to examine the electrochemical stability and the performance of produced bipolar plates in all-vanadium redox flow battery.
Particles bond together when heated by a sintering process that is a combination of several atomic level events that include diffusion, creep, viscous flow, plastic flow and evaporation. Significant strengthening occurs in powder compacts due to sintering. Sintering consumes surface energy to build bonds between those particles. Small particles have more surface energy and sinter faster than large particles. Since atomic motion increases with temperature, sintering is accelerated by high temperatures. The thermodynamic driving force for sintering then is found in the surface area, interfacial energies and curvature gradients in the particle system. Actual atomic motion is by several transport mechanisms with concomitant microstructure changes.
Li4Ti5O12 as anode material for high power Li+-ion batteries is very promising due to its unique electronic properties. However, the lack of electronic conductivity as well as the low Li+-ion diffusion coefficient are major drawbacks in achieving high power densities. In this work, therefore, we prepared a nano-composite consisting of vertically aligned carbon nanotube arrays decorated with in-situ grown necklace type Li4Ti5O12 nanoparticles. Owing to this structure the electrodes exhibit outstanding rate performances with specific capacities of 110 mAh g−1 up to 300C and cycling performance with high capacity retention of 97% after 500 cycles at 10C. Thus, the combination of short Li+-ion diffusion distances within Li4Ti5O12 particles, remarkable electronic conductivity by carbon nanotubes directly grown on the current collector as well as a high contact surface area due to an open pore geometry is essential in achieving high power Li4Ti5O12 anodes.
Herein, we describe a new simple method to improve the irreversible performance of a SiO anode during the initial cycle. The solid state-reacted SiO material was synthesized from bare SiO and lithium powders (three samples with weight ratios of 7:1, 8:1, and 9:1 were prepared) using a heat treatment process at 600 °C. Irreversible phases such as lithium silicates (Li4SiO4 and Li2SiO3) and Li2O were formed upon the solid state reaction with SiO. Electrochemical tests using half-cells were performed to confirm the effects of the solid state-reacted SiO material. The initial Coulombic efficiencies of the three samples were 82.12% (7:1), 79.81% (8:1), and 78.95% (9:1), which were far higher than that of a bare SiO cell (58.52%). Furthermore, the electrochemical performance of a full cell using a 7:1 wt% SiO anode and a lithium cobalt oxide cathode was evaluated. The full cell exhibited an initial Coulombic efficiency of 93.62% and a capacity retention of 74.70% after 15 cycles, which were also far higher than those of a bare SiO cell (66.4% and 55.72%, respectively). A comparison of the solid state-reacted and bare SiO electrodes demonstrated that the pre-formed irreversible phases prevented the consumption of lithium ions during the 1st cycle.
Thin films of LiCoO2 prepared by the electron cyclotron resonance (ECR) sputtering method are investigated under various deposition conditions. Well-crystallized LiCoO2 films were obtained without a post-annealing process in a high microwave and RF power range with a low O2 to Ar ratio. All-solid-state thin-film lithium batteries using the LiCoO2 films (thickness: 6.2μm) provided a discharge capacity of about 250μAhcm−2 with good cyclability.
ABSTRACT Background This article discusses how to integrate clinical and administrative workstations into your dental practice from the planning phase to the implementation phase. The author discusses the costs that are associated with integrating technology, as well as the hardware components and configuration. He then discusses in greater detail the core clinical technologies and how they tie in together to facilitate building a cohesive digital patient record. Conclusions There are no shortcuts to successfully integrating technology into a dental practice. A significant commitment of time, energy and money is a prerequisite to building a secure and reliable computer network that incorporates all clinical and administrative applications. Practice Implications Technology is reinventing the world, and dentists need to keep pace with the people they serve. These new and not-so-new technologies will enhance dental services and productivity, which ultimately will raise the bar for the standard of care in dentistry.
This study investigates the governance role of a country’s legal and extra-legal institutions in explaining the variations in firms’ cost of equity capital induced by concentrated ownership structures from 21 countries. Using four implied cost of equity proxies, the results show that the large ownership-control divergence of the ultimate owner has a positive and significant impact on the firm’s cost of equity capital. The finding lends support to the entrenchment effect in that the concentrated ownership structure increases the firm’s external financing cost. Further analyses demonstrate that the higher equity cost induced by the ultimate ownership structure is significantly reduced by a country’s stronger legal and extra-legal institutions, highlighting the governance role played by a country’s institutions in reducing the firm’s external financing cost.
We have developed flexible polymer-gel electrolytes based on a polyacrylate cross-linked matrix that confines an ionic liquid doped with a lithium salt. Free-standing solid electrolyte membrane is obtained after UV photo-polymerization of acrylic monomers dissolved inside the ionic liquid/lithium salt mixture. The liquid precursor of the photo-ionogel may also be directly deposited onto porous composite electrode, which results in all-solid state electrode/electrolyte stacking after UV illumination. Minor variations in the polymer component of the electrolyte formulation significantly affect the electrochemical behavior in LiFePO4/lithium and lithium/lithium cells. The rate performance increases with an increase of the ionic conductivity, which decreases with the polymer content and decreases with increasing oxygen content in the polyacrylate matrix. Their fairly low modulus endow them weak and beneficial pressure-sensitive-adhesive character. X-Rays Tomography shows that the solid-state photo-ionogel electrolytes keep their integrity upon cycling and that their surface remains smooth. The coulombic efficiency of LiFePO4/lithium cells increases with an increase of the adhesive strength of the photo-ionogel, suggesting a relationship between the contact intimacy at the lithium/photo-ionogel interface and the efficiency of the lithium striping/plating. In lithium/lithium cells, only the photo-ionogels with the higher adhesion strength are able to allow the reversible striping/plating of lithium.
This article introduces a modified simulated annealing triple-optimizer for finding the optimal energy management strategy in terms of financial gain maximization in grid-connected, storage-augmented, photovoltaics-supplied prosumer building microgrids in a variable grid price scenario. For evaluating the performance of the optimizer, a number of test cases are specified offering different trading options to the prosumers. Obtained results are compared to a total state space search reference method and demonstrate that the simulated annealing approach was for all test cases able to find a globally optimal or close to optimal solution in significantly less computation time than the total space search reference method.
Acicular goethite (α-FeOOH) and worm-like maghamite (γ-Fe2O3) nanostructures have been prepared adopting a novel route, using Na2[Fe(HL)2(H2O)2] chelate complex in alkaline medium. It is found that concentration of hydrated Fe(III) ions increased with increasing temperature, which later play a key role in generation of different phases of iron oxide. Phase and morphology of the products are investigated using XRD, FTIR, SEM, and TEM analysis. Using UV–Vis spectra, various electronic transitions of goethite and maghamite particles are examined. Maghamite nanostructures exhibit superparamagnetic property at room temperature. On the basis of experimental observations and analytical data, growth mechanism of the nanostructures is discussed.
A method for preparing three-dimensional (3D) carbon-based architectures consisting of mesoporous carbon spheres intercalated between graphene sheets is demonstrated in this paper. Colloidally dispersed negatively charged graphene oxide (GO) sheets strongly interacted with positively charged mesoporous silica spheres (MSS) to form a MSS–GO composite. The MSS were then used as template for replicating mesoporous carbon spheres (MCS) via a chemical vapor deposition process, during which the GO sheets were reduced to reduced graphene oxide (RGO). Removal of the silica spheres left behind a 3D hierarchical porous carbon architecture with slightly crumpled graphene sheets intercalated with MCS. The 3D carbon structure contained a low amount of oxygen (3.2% of atomic ratio of O/C) than a RGO sample (10.1%), which was prepared by using the chemical reduction method with hydrazine as the reducing agent. Thermal annealing of the 3D carbon structure in ammonia atmosphere further reduced the O/C atomic ratio to 1.6%. The capacitive performance of the samples as supercapacitor electrodes was investigated using the cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. The 3D carbon structure showed a substantially lower equivalent series resistance and a higher power capability than the RGO electrode. In addition, the 3D carbon electrode exhibited an excellent electrochemical cyclability with 94% capacitance retention after 1000 cycles of galvanostatic charge–discharge. The method demonstrated in this work opens up a new route to the preparation of 3D graphene-based architectures for supercapacitor applications.
This work studies the use of various single-walled carbon nanotube (SWCNT) buckypapers as catalyst supports for methanol electro-oxidation in acid media. Buckypapers were obtained by vacuum filtration from pristine and oxidized SWCNT suspensions in different liquid media. Pt–Ru catalysts supported on the buckypapers were prepared by multiple potentiostatic pulses using a diluted solution of Pt and Ru salts (2 mM H2PtCl6 + 2 mM RuCl3) in acid media. The resulting materials were characterized via SEM, TEM, EDX and ICP-OES analysis. Well dispersed rounded nanoparticles between 2 and 15 nm were successfully electrodeposited on the SWCNT buckypapers. The ruthenium content in the bimetallic deposits was between 32 and 48 at. %, while the specific surface areas of the catalysts were in the range of 72–113 m2 g−1. It was found that the solvent used to prepare the SWCNT buckypaper films has a strong influence on the catalyst dispersion, particle size and metal loading. Cyclic voltammetry and chronoamperometry experiments point out that the most active electrodes for methanol electro-oxidation were prepared with the buckypaper supports that were obtained from SWCNT dispersions in N-methyl-pyrrolidone.
The influence of suspension dispersion technique on electrochemical performance of electrodes for lithium-ion batteries is investigated. Anatase TiO2 with particle diameters of 20nm is used as a model material and is dispersed with carbon black aggregates within an organic solution. Electrode structure is analyzed by scanning electron microscopy (SEM) and the electrochemical performance investigated by electrochemical impedance spectroscopy (EIS) and rate capability experiments. SEM investigations indicate that a conventional mixing technique with a turbo-stirrer disperses the TiO2 and carbon black agglomerates of nanoparticles within an order of 1μm and not within the primary particle size order lower than 100nm. EIS experiments show that dispersing the TiO2/carbon black suspensions with a commercial surfactant prior to electrode formation reduces specific impedance and charge transfer resistance of the electrodes. These electrodes are seen to have higher galvanostatic contributions than for electrodes dispersed without the surfactant. Improved break down of the TiO2 agglomerates occurs with more rigorous dispersion techniques and leads to improved electrochemical performance of the electrodes. Dispersion technique is argued to be a critical process in producing high performance electrodes with nanoparticles as active material.
Low cost, high performance supercapacitor electrodes were fabricated using coconut waste as precursor. Simple one step pyrolysis is adopted to get the spherical shaped particle where lignocellulosic nature of carbon converts into porous carbon nanospheres. Three types of coconut wastes, namely, coconut fiber (CF), coconut leaves (CL) and coconut stick (CS) have been studied and compared for their application in supercapacitors. Uniform spherical shape with particle size ranging from 30 to 60nm for leaves and sticks and ∼20nm for fibers was obtained. The electrochemical properties of the porous carbon nanospheres were studied using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). The porous carbon nanospheres derived from all the three biowaste samples show good electrochemical performance for supercapacitor application. Porous carbon nanospheres derived from coconut fiber exhibited maximum specific capacitance of 236 F/g followed by coconut stick and coconut leaves with 208 and 116 F/g respectively at a scan rate of 2mV/s. Further impedance studies showed a charge transfer resistance of 4.9 Ω for the porous carbon nanospheres derived from coconut fiber, while those from coconut leaves and coconut stick exhibited a slightly higher resistance of 6 and 14.2 Ω, respectively. The simple eco-friendly approach we have demonstrated for synthesizing coconut waste based carbon nanospheres makes them excellent candidates for future, low-cost, energy storage devices.
We utilized density functional theory to examine HF generation in lithium-ion battery electrolytes from reactions between H2O and the decomposition products of three electrolyte additives: LiPF6, LiPOF4, and LiAsF6. Decomposition of these additives produces PF5, AsF5, and POF3 along with LiF precipitates. We found PF5 and AsF5 react with H2O in two sequential steps to form two HF molecules and POF3 and AsOF3, respectively. PF5 (or AsF5) complexes with H2O and undergoes ligand exchange to form HF and PF4OH (AsF4OH) with an activation barrier of 114.2 (30.5) kJ mol−1 and reaction enthalpy of 14.6 (−11.3) kJ mol−1. The ethylene carbonate (EC) electrolyte forms a Lewis acid–base complex with the PF4OH (AsF4OH) product, reducing the barrier to HF formation. Reactions of POF3 were examined and are not characterized by complexation of POF3 with H2O or EC, while PF5 and AsF5 complex favorably with H2O and EC. HF formation from POF3 occurs with a reaction enthalpy of −3.8 kJ mol−1 and a 157.7 kJ mol−1 barrier, 43.5 kJ mol−1 higher than forming HF from PF5. HF generation in electrolytes employing LiPOF4 should be significantly lower than those using LiPF6 or LiAsF6 and LiPOF4 should be further investigated as an alternative electrolyte additive.
A novel cathode material, polysulfide polypyrrole was successfully designed and synthesized for high-energy lithium–sulfur secondary batteries. The product was characterized by FT-IR, element analysis and DSC. Character results show that the polymer was obtained with polypyrrole as backbone and S–S side groups attached to it. Polypyrrole backbone in this polymer was used not only as container but also as conductivity passage. Cycle performances of the polymer was examined as active cathode material in lithium batteries, charge–discharge experimental results indicate that the polymer has a specific capacity of 515mAhg−1 at the first cycle and 452mAhg−1 at the 20th cycle. The improved cycle properties compared to other polymer disulfides and polysulfide polymers supply a good foundation for practical application of this material in rechargeable lithium batteries.
Internal short circuit of large-format Li-ion pouch cells induced by mechanical abuse was simulated using a modified mechanical pinch test. A torsion force was added manually at ∼40% maximum compressive loading force during the pinch test. The cell was twisted about 5° to the side by horizontally pulling a wire attached to the anode tab. The combined torsion-compression force created small failure at the separator yet allowed testing of fully charged large format Li-ion cells without triggering thermal runaway. Two types of commercial cells were tested using 4–6 cells at each state-of-charge (SOC). Commercially available 18 Ahr LiFePO4 (LFP) and 25 Ahr Li(NiMnCo)1/3O2 (NMC) cells were tested, and a thermal runaway risk (TRR) score system was used to evaluate the safety of the cells under the same testing conditions. The aim was to provide the cell manufacturers and end users with a tool to compare different designs and safety features.
By using an electrodeposition method to form hexavanadates, followed by a thermal process, a range of bronze stoichiometries, M x V6O13+y , where M: K, Ni, or Mo, 0<x<0.5, 0.2<y<3.3 in the ternary system of V2O4–V2O5–M2O were prepared. These bronzes adhered well to a conducting substrate and could be directly fabricated into a coin cell without the need for binders or electronic conductors. The phase changes on discharge and the lithium insertion ability were influenced by the amount of the guest metal in the bronze structure. When the value of x was small (<0.5) reversible phase changes resembled those of V2O5 or V6O13 depending on the initial O2 content of the bronze after heating. The cycle life was adversely affected by the depth of discharge below 2.2V for the V2O5 type bronzes. The V6O13 bronze cathodes had better cycle lives at average operating voltages of about 2.5V and over 350Ah/kg for their initial cycles.
The fractional order expressed as a function of recursive factors defines the fractional morphology of charge distribution on porous electrodes. Electrode aging causes the fractality of charge distribution to gradually deviate from the original fractal dimension, consequently, the fractional order of the fractional order model varies with the cycle number of batteries. This paper aims to determine the relationship between the fractional order and electrode aging, and use the fractional order as an indicator for electrode aging. The transient discharge dataset of fully charged lithium-ion batteries is taken as the input signal of the identification system of the fractional order model. The identification of the fractional order is then performed with the least squares method. The results show that there is a stable monotonous relationship between the fractional order and the cycle number of batteries. Using the fractional order as an indicator for electrode aging can quickly evaluate the degradation level of electrodes without destroying the battery. Moreover, it is significant to find that the electrode life is terminated when the fractional order tends to be stable, and therefore, the fractional order is used to recognize the ongoing or abrupt degradation of batteries. The effectiveness of the proposed method is verified by the dataset of National Aeronautics and Space Administration (NASA) Ames Prognostics Center of Excellence and the dynamic stress test.
Coating and doping with zinc have been used to modify LiNi0.5Mn1.5O4 powders prepared at 700 and 800 °C. As previously found in the literature, surface treatment with zinc leads to a net improvement of the electrochemical performance of the 5-V electrode in lithium cells. X-ray diffraction reveals the occurrence of surface ZnO, which disappears after heating at 500 °C. This indicates that ZnO forms a coating, although zinc can also be incorporated in the LiNi0.5Mn1.5O4 framework. The electrochemical oxidation of both bare LiNi0.5Mn1.5O4 and zinc treated products has been followed by ex situ X-ray diffraction of charged electrodes. For both materials a decrease in the cubic unit cell parameter and the formation of two cubic phases during lithium extraction has been found. Lattice contraction is significantly larger in the sample modified with zinc. EIS measurements give direct evidence of the better stabilization of the electrode surface in the coated material.