Change In Charge State Research Articles

Spin-dependent magnetism and superparamagnetic contribution to the magnetocaloric effect of non-stoichiometric manganite nanoparticles

Despite extensive research on manganites owing to their potential use in modern technologies, some aspects of their behaviour associated with changes in spin, valence, and charge states remain unclear. In this work, we investigated the structural, magneto-transport, and magnetocaloric properties of La0.8-x□xNa0.2Mn1+xO3-Δ manganite nanoparticles with strong spin-electron coupling. It was found that the perovskite structure contained different valence manganese ions, MnB3+, MnB4+, and MnA2+, even in the pristine compound. With an increase in x, increases in the Curie temperature TC, spontaneous magnetization, and magnetic entropy change ΔSM, as well as a decrease in the metal-semiconducting temperature Tms, were detected. The change in the spin value of Mn ions during the transition from ferromagnetic-metallic (μFMexp < μFMtheor) to the paramagnetic-semiconducting (μPMexp > μPMtheor) state owing to the localization–delocalization process of eg-electrons on the Mn sites was found to indicate spin-dependent magnetism. The complex critical behaviour is manifested near TC with a second-order phase transition. An additional influence of the super-paramagnetism of nanoparticles on the magnetocaloric effect was determined.

Bioinformatic Analysis of Human Collagen Sequence Mutations on Osteogenesis Imperfecta

Collagen has been implicated in a number of pathological conditions. When an amino acid in triple helix is replaced with other amino acids, the collagen structure is destroyed. The deterioration in the collagen structure causes various hereditary diseases and dysfunctions. In this study, the mutations on the alpha-1 chain of type I collagen, which is the most common in the human body, were examined using Python programming language. Based on the previous studies, brittle bone disease (OI) type 2 caused by mutations in type-I collagen alpha-1 chains, has been focused on. UniprotKB database were used for the mutations reported. The mutations obtained were combined in an alpha-I chain and it was seen that the most mutated amino acid was glycine (Gly). Since glycine amino acid affects the stability of the helix structure of the collagen alpha-I chain, it can be considered to influence collagen-induced diseases. The most frequently recurring mutations (glycine (G)> arginine (R), glycine (G)> serine (S), glycine (G)>aspartate (D)) were detected. As a result of comparison, increase in molecular mass, change in isoelectric point, decrease in hydropathy index, change in charge state and acid-base properties were observed. The effect of these changed features on brittle bone disease (OI) has been interpreted.

Predicting Thermal Runaway Event in an Abused High Energy Li-Ion Cell

As the energy storage devices continue to "pack" more energy in a small space, any damage, battery component failure, manufacturing defect, or electrically abusing the battery can lead to catastrophic thermal runaway events. A catastrophic thermal event in a cell leads to high temperature, in some instances spewing of battery materials due to gas development from side reactions initiated due to high internal temperatures. Also, in a battery pack, a thermal runaway event can propagate from a single "failed" cell to the pack, leading to a more significant event. Mitigating a thermal runaway event is important in the commercial and automotive sectors. However, preventing such events in an electric aircraft (or air taxis) is paramount due to the lack of alternatives in the event of a failure.Battery prognostics algorithms allow to predict state-of-charge (SOC) and end-of-life (EOL) of a Li-ion battery in a UAV (unmanned air vehicle). For this presentation, we will extend this two-level battery prognostic algorithm to predict SOC, EOL, and maximum temperature during a simulated flight. The change in SOC and EOL is considered by decreasing the maximum stored charge and solid Li-ion diffusivity and increased internal resistance on cycling [1]. Cycling leads to an increase in the heat generated by an aged Li-ion cell with an NMC 811 cathode and a silicon-graphite anode. Aged cells lead to the increase in the thickness of the SEI layer, increase in the resistance of ion diffusion and reaction kinetics, and thermodynamic abuse due to fixed cycling voltages. Since SEI decomposition has the lowest onset temperature in the series of reactions leading to thermal runaway, the model considers the self-heating rate of the SEI decomposition. The parameters in the Arrhenius equation for the SEI heating rate depend on the number of cycles, the cell's operating temperature, and the cell's abuse history [2,3].Coupling the electrochemical, thermal, and aging model would allow the prognostic algorithm to predict the rise in the operating temperature for the same discharge profile for an electric aircraft. Which, in principle, could provide an early indication for a (possible) thermal runaway event.Predicting operating temperatures in addition to SOC, SOH, and EOL in battery management systems will allow better battery monitoring and strategies for mitigating catastrophic thermal runaway events.

Linear parameter-varying modeling and identification of lithium-ion battery for control-oriented applications

Model-based approaches are popularly used for real-time management of lithium-ion batteries. However, building accurate models to characterize the inherent nonlinear dynamic properties of electrochemical processes is still a challenge for control-oriented applications. Instead of building a model independently from physical laws or experimental data, a linear parameter-varying (LPV) modeling method for lithium-ion batteries is proposed in this research. In the LPV modeling structure, the nonlinear relationships are considered to be dependent on the so-called scheduling variables. In combination with the subspace identification algorithm, a global method is proposed to identify the LPV battery model based on a single data set with constantly changing scheduling variables. The validity of this modeling approach is verified by an experimental study of lithium iron phosphate (LiFePO4) cells. Experimental results reveal that state-of-charge (SOC) and SOC change rate are key scheduling variables that determine the model nonlinearities, and the identified model provides good results in terms of prediction accuracy and robustness. Meanwhile, comparison results show that the global LPV modeling approach can describe the nonlinear battery dynamics adequately with first-order model, which makes it a promising method for control-oriented applications.

Peeling graphite layer by layer reveals the charge exchange dynamics of ions inside a solid

Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations.

Comparative study of optical properties of substitutionally doped La2NiMnO6 double perovskite ceramic: A potential candidate for solar cells and dielectrics

With the curiosity to account for transition metal-based oxide double perovskites (A2BB΄O6) as better-performing semiconducting materials for light-driven devices and dielectrics, the study examined the optical properties of La2NiMnO6 doped substitutionally at A sites by Ca and Yb. The study is performed by making use of Density Functional Theory wherein the Local Density Approximation along with columbic corrections (LDA + U) was used to investigate the comparative effect of Ca and Yb dopants at A site of LMNO and the changes observed henceforth are vital keeping in view the effect of change of charge state at A site. The dielectric tensor suggests the isotropic behaviour of the material. In case of applied varying ac fields, the dielectric constant becomes a complex quantity and has two parts viz real and imaginary wherein the real part is associated with the degree of polarization and the imaginary part, on the other hand, is associated with the dielectric losses. The dielectric constants (both real and imaginary) were plotted against the frequency changes and the trends in absorption, refraction, dielectrics, and optical conductivities that emerge from this study have important electronic and optical implications. The dielectric relaxation which arises as a consequence of the inability of the dipoles to cope with the frequent oscillations of the perturbing field makes it possible for the material to be used in memory elements. Furthermore, the simpler and cost-efficient method of preparation (Solid State Reaction) with the high value of dielectric constant and optical conductivities in the visible spectral range favors the use of these materials in the case of energy storage devices and other optoelectronic devices like solar cells and can replace the toxic lead halide perovskite cells.

Intermetallic Charge Transfer in V-Substituted PbCrO3

PbCrO3 features an unusual charge distribution Pb0.52+Pb0.54+Cr3+O3 with Pb charge disproportionation at ambient pressure. A charge transfer between Pb and Cr is induced by the application of pressure resulting in Pb2+Cr4+O3 charge distribution and a large volume collapse. Here, structural and charge distribution changes in PbCr1-xVxO3 are investigated. Despite a cubic crystal structure in 0 ≤ x ≤ 0.60, discontinuous reduction in the unit cell volume was observed between x = 0.35 and 0.40. Hard X-ray photoemission spectroscopy confirmed the change in Pb charge state from the coexisting Pb2+ and Pb4+ at x = 0.35 to single Pb2+ at x = 0.40. This indicates that V substitution stabilizes the high pressure cubic Pb2+Cr4+O3-type phase. With further increase in the V substitution, the PbVO3-type polar tetragonal phase appeared at x = 0.80.

Oxygen Nonstoichiometry and Valence State of Manganese in La1-x Ca x MnO3+δ.

Perovskites of the ABO3 type, such as LaMnO3, can be used as air electrodes in solid oxide fuel cells and electrolyzers. Their properties can be tuned by A- and B-site substitutions. The influence of La substitution by Ca on the oxygen nonstoichiometry has been investigated frequently, but the results depend highly on the synthesis and atmospheric conditions. In this work, a series of La1–xCaxMnO3+δ (x = 0–0.5) was synthesized using conventional solid-state synthesis under an air atmosphere. The structures of the materials were studied in detail with powder X-ray diffraction. The initial oxygen nonstoichiometries were determined using thermogravimetric reduction. The samples were subsequently analyzed in terms of defect chemistry in dependence of temperature, atmosphere, and Ca content via thermogravimetric analysis. The changes in the manganese charge states were investigated by X-ray absorption near-edge spectroscopy experiments. The influence of intrinsic and extrinsic effects on the Mn-valence state of the differently Ca-substituted samples as calculated from thermogravimetric analysis and as determined directly from X-ray absorption near-edge spectroscopy is presented.

State-of-Charge Monitoring and Battery Diagnosis of Different Lithium Ion Chemistries Using Impedance Spectroscopy

For lithium iron phosphate batteries (LFP) in aerospace applications, impedance spectroscopy is applicable in the flat region of the voltage-charge curve. The frequency-dependent pseudocapacitance at 0.15 Hz is presented as useful state-of-charge (SOC) and state-of-health (SOH) indicator. For the same battery type, the prediction error of pseudocapacitance is better than 1% for a quadratic calibration curve, and less than 36% for a linear model. An approximately linear correlation between pseudocapacitance and Ah battery capacity is observed as long as overcharge and deep discharge are avoided. We verify the impedance method in comparison to the classical constant-current discharge measurements. In the case of five examined lithium-ion chemistries, the linear trend of impedance and SOC is lost if the slope of the discharge voltage curve versus SOC changes. With nickel manganese cobalt (NMC), high impedance modulus correlates with high SOC above 70%.

Measurements and modelling of the response of an ultrasonic pulse to a lithium-ion battery as a precursor for state of charge estimation

Lithium-ion batteries change their internal state during cycles of charge and discharge. The state of charge of a lithium-ion battery varies during the charging cycle and depends on the internal structure of the components which may degrade with use. Estimation of the state of charge is commonly performed by battery management systems that rely on charge counting and cell voltage measurement. Determining the physical state of the battery components is challenging. Recently, the response of an ultrasonic pulse to a battery has been successfully correlated with both change in state of charge and state of health, the quality of the approach is now well established. This study assesses the qualities contained within an ultrasound signal response by investigating the behaviour of ultrasonic waves as they pass through the components in a layered battery structure, as those components change with battery charge. A model has been developed to understand the nature of the ultrasound response and the features that provide a particular characteristic. This is useful as two apparently identical batteries can produce very different ultrasonic responses. Detailed data analysis has been performed to find which combination of data comparisons provides the strongest correlation with state of charge and guides decisions about future use of battery monitoring using ultrasound. Finally, a smart peak selection method has been developed to ensure that regardless of the nature of the ultrasound response, state of charge measurements are optimised by ensuring the regions of signal with best battery charge correlation are identified. This can greatly help with the automation of the process in a sensor-based battery management system.

Accurate Online Battery Impedance Measurement Method with Low Output Voltage Ripples on Power Converters

The conventional online battery impedance measurement method works by perturbing the duty cycle of the DC-DC power converter and measuring the response of the battery voltage and current. This periodical duty cycle perturbation will continuously generate large voltage ripples at the output of power converters. These large ripples will not easily be removed due to the high amplitude and wide frequency range and would be a challenge to meet tight output regulation. To solve this problem, this paper presents a new online battery impedance measurement technique by inserting a small switched resistor circuit (SRC) into the converter. The first contribution of this work is that the perturbation source is moved from the main switch to the input-side of the converter, so the ripples are reduced. The analysis and experimental results of the proposed method show a reduction of 16-times compared with the conventional method. The second contribution tackles the possible change of the battery state of charge (SOC) during the online battery measurement process, which will inevitably influence the impedance measurement accuracy. In this proposed method, battery impedance at multiple frequencies can be measured simultaneously using only one perturbation to accelerate measurement speed and minimize possible SOC change. The experimental impedance results coincide with a high-accuracy laboratory battery impedance analyzer.

The Role of Charge and Recombination‐Enhanced Defect Reaction Effects in the Dissociation of FeB Pairs in p‐Type Silicon under Carrier Injection

The dissociation of FeB pairs in p‐type silicon under injection is often explained by the charge state change of interstitial Fe (Fei) from positive to neutral. It is also sometimes interpreted as a recombination‐enhanced defect reaction (REDR) mechanism. The charge effect and the REDR have fundamentally different impacts on the dissociation/association reactions: the former changes the concentration of Fei+, whereas the latter changes the reaction rate constants. Herein, the two effects are investigated and compared through measuring and analyzing the dynamics of the reactions. The results confirm that the dissociation of FeB under carrier injection cannot be purely attributed to the change of charge states. The extracted dissociation/association rate constant ratio shows an approximately linear dependence on the recombination rate on each FeB pair, indicating the REDR effect. The results allow the two effects to be directly compared, highlighting the dominant role of the REDR effect in dissociating the pairs.

The influence of electrochemical cycling protocols on capacity loss in nickel-rich lithium-ion batteries.

The transition towards electric vehicles and more sustainable transportation is dependent on lithium-ion battery (LIB) performance. Ni-rich layered transition metal oxides, such as NMC811 (LiNi0.8Mn0.1Co0.1O2), are promising cathode candidates for LIBs due to their higher specific capacity and lower cost compared with lower Ni content materials. However, complex degradation mechanisms inhibit their use. In this work, tailored aging protocols are employed to decouple the effect of electrochemical stimuli on the degradation mechanisms in graphite/NMC811 full cells. Using these protocols, impedance measurements, and differential voltage analysis, the primary drivers for capacity fade and impedance rise are shown to be large state of charge changes combined with high upper cut-off voltage. Focused ion beam-scanning electron microscopy highlights that extensive microscale NMC particle cracking, caused by electrode manufacturing and calendering, is present prior to aging and not immediately detrimental to the gravimetric capacity and impedance. Scanning transmission electron microscopy electron energy loss spectroscopy reveals a correlation between impedance rise and the level of transition metal reduction at the surfaces of aged NMC811. The present study provides insight into the leading causes for LIB performance fading, and highlights the defining role played by the evolving properties of the cathode particle surface layer.

Joint estimation of SOC and SOH for lithium-ion batteries based on EKF multiple time scales

PurposeThe operation state of lithium-ion battery for vehicle is unknown and the remaining life is uncertain. In order to improve the performance of battery state prediction, in this paper, a joint estimation method of state of charge (SOC) and state of health (SOH) for lithium-ion batteries based on multi-scale theory is designed.Design/methodology/approachIn this paper, a joint estimation method of SOC and SOH for lithium-ion batteries based on multi-scale theory is designed. The venin equivalent circuit model and fast static calibration method are used to fit the relationship between open-circuit voltage and SOC, and the resistance and capacitance parameters in the model are identified based on exponential fitting method. A battery capacity model for SOH estimation is established. A multi-time scale EKF filtering algorithm is used to estimate the SOC and SOH of lithium-ion batteries.FindingsThe SOC and SOH changes in dynamic operation of lithium-ion batteries are accurately predicted so that batteries can be recycled more effectively in the whole vehicle process.Originality/valueA joint estimation method of SOC and SOH for lithium-ion batteries based on multi-scale theory is accurately predicted and can be recycled more effectively in the whole vehicle process.

Dynamic battery loss evaluation and its application for optimal online wind‐storage integrated scheduling

The life loss of batteries caused by the daily operation implies a reduction in capital value, which is essential for the economic performance of storage-containing systems. Most of current studies rarely considered it or simplified it to be proportional of throughput electricity, due to its multi-factor dependence and complexity to be incorporated into dispatch models. This study presents a dynamic loss evaluation model for batteries that considers the cumulative effect of state of charge (SOC) changes. First, based on the results of battery aging test, the loss coefficient subject to SOC is derived. The general formulation of analytical battery life loss is further presented by integrating the damage effect during the change in SOC. Finally, by means of self-optimal piecewise linearisation, the resultant life loss term is embedded in the online wind-storage integrated scheduling. Case studies demonstrate the desirable computational complexity of the proposed evaluation method and the adaptability in general economic dispatch.

Thiolate‐Protected Single‐Atom Alloy Nanoclusters: Correlation between Electronic Properties and Catalytic Activities

AbstractDue to their interesting chemical and optical properties, metal nanoclusters are used in various catalytic reactions and in energy conversion. By incorporating thiolate‐protecting ligands, their size and composition can be tuned. Doping these nanoclusters to form single‐atom alloy (SAA) nanoclusters is shown to further enhance these properties as a result from the synergy between the dopant and host atoms. In addition to their optical and chemical properties, SAA nanoclusters also have interesting electronic properties. However, these properties are often underdiscussed when studying SAA nanoclusters. This review provides an overview of representative studies done on the in‐depth understanding of the electronic properties and catalytic activities of Ag‐based and Au‐based thiolate‐protected SAA nanoclusters. The use of density functional theory (DFT), X‐ray absorption spectroscopy, and X‐ray photoelectron spectroscopy are employed to correlate the changes in charge states of thiolate‐protected SAA nanoclusters with their superior catalytic activity versus monometallic nanoclusters. DFT, UV–vis spectroscopy, and voltammetric methods link the changes in molecular energy levels of thiolate‐protected SAA nanoclusters to their enhanced catalytic performance over monometallic nanoclusters.

Determination of extent of PEGylation using denaturing capillary isoelectric focussing

Conjugated proteins and enzymes are often formed using N-hydroxysuccinimide (NHS) chemistry, which reacts with free primary amines resulting in a loss of charge and a reduction in isoelectric point (pI). Measurement of the extent of reaction of these conjugates is critical for biopharmaceutical developers. Due to this change in protein charge state, denaturing capillary isoelectric focussing (cIEF) offers a potentially straightforward and convenient approach for extent-of-reaction quantification. Here, we demonstrate the potential of this technique with poly(ethylene glycol) (PEG) conjugates of Erwinia chrysanthemil-asparaginase (ErA). Development of an appropriate sample preparation technique is critical to achieving reproducible cIEF electropherograms, particularly for denaturation-resistant proteins such as ErA, and an emphasis was placed on this during development of the PEG-ErA cIEF method. cIEF electropherograms demonstrating a distribution of PEGylation states in a bell-shaped curve were obtained, and assignment of PEGylation states to these peaks was critical to routine use of the method. The method is sensitive enough to resolve non-lysine adducts of PEG (such as those conjugated to histidine residues) and was shown to give reproducible results over a 2 year period. Biopharmaceutical developers should consider cIEF for extent of reaction monitoring and measurement for conjugates of free amine groups.

Temperature-Resolved Proton Transfer Reactions of Biomolecular Ions.

Temperature-resolved proton transfer reactions of multiply-protonated angiotensin I, disulfide-intact and -reduced lysozyme, and ubiquitin ions to primary, secondary and aromatic amines were examined in the gas phase. Absolute reaction rate constants for the proton transfer were determined from the intensities of the parent and product ions in mass spectra. Dramatic changes were observed in the distribution of product ions and the reaction rate constants. In particular, the rate constants for disulfide-intact lysozyme ions changed more drastically with the change in charge state and temperature compared to the corresponding values for disulfide-reduced ions. Proton transfer reactions were enhanced or suppressed as the result of the formation of complexes between the ions with gaseous molecules, which is related to changes in their conformation with changing.

Vacancy defect modulation in hot-casted NiO film for efficient inverted planar perovskite solar cells

Abstract Nickel oxide (NiOx) has exhibited great potential as an inorganic hole transport layer (HTL) in perovskite solar cells (PSCs) due to its wide optical bandgap and superior stability. In this study, we have modulated the Ni2+ vacancies in NiOx film by controlling deposition temperature in a hot-casting process, resulting the change of coordination structure and charge state of NiOx. Moreover, the change of the HOMO level of NiOx makes it more compatible with perovskite to decrease energy losses and enhance hole carrier injection efficiency. Besides, the defect modulation in the electronic structure of NiOx is beneficial for increasing the electrical conductivity and mobility, which are considered to achieve the balance of charge carrier transport and avoid charge accumulation at the interface between perovskite and HTL effectively. Both experimental analyses and theoretical calculations reveal the increase of nickel vacancy defects change the electronic structure of NiOx by increasing the ratio of Ni3+/Ni2+ and improving the p-type characteristics. Accordingly, an optimal deposition temperature at 120 °C enabled a 36.24% improvement in the power conversion efficiency compared to that deposited at room temperature (25 °C). Therefore, this work provides a facile method to manipulate the electronic structure of NiOx to improve the charge carrier transport and photovoltaic performance of related PSCs.

Empirical approach to determine open-circuit voltage of a vanadium-redox-flow battery for models, based on published data for anion-exchange and cation-exchange membranes and temperature dependency

Abstract Vanadium-redox-flow batteries (VRFB) are the most commercialized flow batteries. Many models are designed to improve several parameters and setups to increase the efficiency or decrease costs. The open circuit voltage (OCV) inside VRFB models is either modelled based on state of charge (SOC) or the vanadium ion concentrations. In both cases a form of the Nernst equation is used to approximate the OCV and feeding the Nernst equation with results from measurements or theory. Measurements to approximate the OCV at a SOC are state of the art. The theoretical input for the Nernst equation still lacks of precision and approaches to increase the precision, were studied in the last decade. Here an empirical approach shows possible improvements to link the measured OCV with the theoretical SOC. The improvements are performed by fitting mathematical functions to the differences between the theoretical and measured data with leas square. This is performed for anion exchange membranes (AEM) with great success. The mean error for the approach of Zlotorowicz et al. [1] is below 1% with a maximum error of 3%. The fitting functions is interpreted as effects influencing the energy conversion processes, like crossover, changes in material characteristics and further side reactions. Fitting the cation exchange membrane (CEM), using the same approach, proves to be more challenging. The mean error is 1.9 to 2.8% with a maximum error of 23%, which shows different approaches might improve CEM based VRFBs. The processes inside a stack with a CEM follow different processes than for AEMs and slight connection to other energy conversion systems with flow cells could be drawn. The temperature dependency shows further influences than defined in by the Nernst equation, for a VRFB. Depending on the approach the temperature shifts the OCV curve along the SOC range or changes all four fitting parameters. The results show possibilities and helps to choose from different approaches of modelling the correlation between ion concentration and SOC for AEM and CEM with temperature influences.