Search

In this study, a flower-like Au/CeO2 supported catalyst composite anode was prepared to explore its impact on thermal runaway triggered by overcharging and flame. Through structural and performance characterization, it was found that the catalyst has a high specific surface area and good CO catalytic oxidation capability, with a CO removal rate higher than 99.97% at room temperature. Through electrical performance testing, it was discovered that, compared to batteries without the catalyst, batteries using the composite anode did not exhibit significant capacity degradation. In overcharge testing, the catalyst prolonged the voltage rise time and peak voltage occurrence time of the battery. In thermal runaway testing, the addition of the catalyst delayed the detection time of CO and significantly reduced the concentration of thermal runaway products, especially the peak concentration and integrated concentration of CO, demonstrating its effectiveness in reducing thermal runaway products. Therefore, this study provides a new approach for improving the safety of lithium-ion batteries. The catalyst exhibits good performance in reducing toxic gases generated after thermal runaway and delaying the occurrence of thermal runaway, providing strong support for the safe application of lithium-ion batteries. [ABSTRACT FROM AUTHOR]

O artigo busca discutir desafios metodológicos relacionados ao estudo comparado da overcharging norte-americana. Sem discrepar do que ocorre em relação à análise comparada do sistema jurídico estadunidense, o estudo comparado da overcharging possui limitações e demanda cuidados específicos. No entanto, o emprego de métodos que diminuam o risco de equívocos e que permitam uma melhor compreensão dos institutos jurídicos norte-americanos pode contribuir decisivamente para o alcance das finalidades do estudo comparativo.

In this study, a flower-like Au/CeO2 supported catalyst composite anode was prepared to explore its impact on thermal runaway triggered by overcharging and flame. Through structural and performance characterization, it was found that the catalyst has a high specific surface area and good CO catalytic oxidation capability, with a CO removal rate higher than 99.97% at room temperature. Through electrical performance testing, it was discovered that, compared to batteries without the catalyst, batteries using the composite anode did not exhibit significant capacity degradation. In overcharge testing, the catalyst prolonged the voltage rise time and peak voltage occurrence time of the battery. In thermal runaway testing, the addition of the catalyst delayed the detection time of CO and significantly reduced the concentration of thermal runaway products, especially the peak concentration and integrated concentration of CO, demonstrating its effectiveness in reducing thermal runaway products. Therefore, this study provides a new approach for improving the safety of lithium-ion batteries. The catalyst exhibits good performance in reducing toxic gases generated after thermal runaway and delaying the occurrence of thermal runaway, providing strong support for the safe application of lithium-ion batteries.

O presente trabalho visa a avaliar se existe um risco relevante de ocorrência do overcharging nas práticas negociais do Direito Penal brasileiro, tomando como base a definição desse conceito no Direito norte-americano e as condições que favorecem sua existência nos Estados Unidos. Ao final, verifica-se em que medida essas condições se reproduzem no Direito brasileiro, especificamente em relação aos institutos da transação penal e do acordo de não persecução penal.

Overcharging is one of the most serious safety problems in large-scale application of lithium ion battery (LIB). An in-depth understanding of the failure mechanism of battery overcharge is necessary to guide the safe design of battery system. In this paper, the electrochemical performance of commercial 18650-type cylindrical battery with Li(Ni0.5Co0.2Mn0.3)O2 cathode and graphite anode as the background is evaluated with different state of charge (SOC). The dynamic thermal behavior of overcharge in adiabatic conditions is studied, and the cathode materials, separator and anode materials after long-term overcharge cycle are characterized to identify the side reactions in battery. The results show that the battery impedance increases with the increase of SOC, and thereby greatly accelerating the attenuation of battery capacity. When LIB is charged and discharged in adiabatic conditions, the battery surface temperature of 116% SOC is about 10.03 °C higher than that of 100% SOC. Therefore, the battery with higher SOC has higher heating and is easy to induce the thermal runaway reactions. During the overcharge cycle, electrolyte decomposition, transition metal dissolution and phase transformation occur at the cathode, and serious lithium plating occur at the anode, as a result, increasing battery impedance, accelerating aging and increasing heat production. These results provide feasible support for understanding the overcharge mechanism and battery management system.

Charged biopolymers able to adsorb solubilized metal cations instead of precipitating them as inorganic waste provide a sustainable option for conventional lime treatment of acidic metal-bearing effluents. We investigated the adsorption of trivalent iron (Fe3+) and lanthanum (La3+) on anionic TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl)-oxidized nanofibrillated cellulose (TONFC) from concentrated solutions at increasing ionic strengths (I). In the adsorption experiments, solutions containing 25–150 mM FeCl3 or LaCl3 as such (I0), or with I adjusted to 1 (I1) or 4 (I4) with NaCl, were treated with TONFC. Following filtration, the solutions were subjected to pH measurement and analysis for the TONFC-induced changes in Fe and La concentrations. The susceptibility of the retained metals to desorption was elucidated by back extraction. Adsorption of Fe3+ and La3+ significantly exceeded the negative charge density of TONFC, which led to positive overcharging of cellulose fibrils. The consequent Coulomb repulsion between the fibrils prevented their aggregation and enabled metal retention even under highly acidic conditions. At high I, Na + ions derived from the NaCl background were unable to compete with Fe3+ or La3+ for the sorption sites. Excess of Cl- ions, in turn, produced chloride complexes, particularly with Fe3+. They abated overcharging, which induced TONFC condensation and reduced Fe sorption within a critical concentration range. Above this range, Fe sorption recovered presumably due to partial redispersion of cellulose fibrils. Analogous condensation and redispersion of TONFC was not detected in the reaction with La3+. In conclusion, its overcharging tendency renders TONFC a superior agent for the treatment of highly concentrated metal-bearing effluents of very low pH. Successful utilization of the material as a water purification agent, however, requires understanding of the re-entrant behavior of TONFC with solutions of high I.

Battery overcharging can occur due to capacity and internal resistance variations among cells or battery management system failure that both accelerate battery degradation, which is more likely at low temperatures because of the large polarization effect. This study experimentally investigated the battery degradation characteristics during charging of LiFePO4 (LFP)/Graphite batteries at voltages of 3.65–4.8 V and Li(Ni0.5Co0.2Mn0.3)O2 (NCM)/Graphite batteries at 4.2–4.8 V at −10 °C with currents of 0.2–1 C. The results showed that the LFP cell capacities decreased linearly with an increasing number of cycles, while the NCM cell capacities faded in three trends with an increasing number of cycles under different conditions with linear fading, accelerated fading, and decelerated fading. The incremental capacity curves and differential voltage curves showed that the LFP cell degradation was mainly caused by the loss of lithium inventory (LLI), with some effect from the loss of active material (LAM). In the NCM cells, both the LLI and LAM significantly contributed to the degradation. Combined with internal battery morphology observations, the LAM mainly occurred at the anode, and the main side reactions leading to the LLI with lithium plating and solid electrolyte interface growth also occurred at the anode. [ABSTRACT FROM AUTHOR]

Asymmetric behaviors of capacitance and charging dynamics in the cathode and anode are general for nanoporous supercapacitors. Understanding this behavior is essential for the optimal design of supercapacitors. Herein, we perform constant-potential molecular dynamics simulations to reveal asymmetric features of porous supercapacitors and their effects on capacitance and charging dynamics. Our simulations show that, counterintuitively, charging dynamics can be fast in pores providing slow ion diffusion and vice versa. Unlike electrodes with single-size pores, multi-pore electrodes show overcharging and accelerated co-ion desorption, which can be attributed to the subtle interplay between the dynamics and charging mechanisms. We find that capacitance and charging dynamics correlate with how the ions respond to an applied cell voltage in the cathode and anode. We demonstrate that symmetrizing this response can help boost power density, which may find practical applications in supercapacitor optimization.

Battery safety tests are defined by several international standards in different ways and with heterogenous termination and failure criteria. In this work, lithium-ion cells were examined regarding their behavior in the event of overcharging and also in the event of an external short circuit with varied parameters specified by standards. The voltage, current, and temperature curves were evaluated. In addition, the changes in the cells were analyzed using electrochemical impedance spectroscopy (EIS). It is shown that the cells exhibit reproducible behavior in a clamped state. Further, it could be determined that the position of the cell opening during an overcharge has an influence on the further behavior of the cell. EIS data showed that the cells have a significantly higher internal resistance after an overcharge. The short-circuit tests at different ambient temperatures indicated that the internal resistance of the cell decreases with increasing temperature. However, no reproducible effects in impedance spectra were present after the short-circuit test. This work illustrates that the choice of test parameters and termination criteria undoubtedly influence the test results and thus may change the classification of cells as either safe or unsafe. Thus, cells may be classified as safe regarding a certain standard but unsafe regarding another. [ABSTRACT FROM AUTHOR]

The stability of colloidal dispersions in the presence of multivalent ions depends strongly on the electrostatic interactions between the suspended particles. Of particular interest are colloidal particles having dimensions in the nanometric range and with an anisotropic shape due to its high surface area per unit mass, for example clay, which has the key characteristic of a negatively charged surface, surrounded by an oppositely charged rim. In this study, we investigate the interactions in nanoplatelet dispersions for the model system of Laponite® clay with addition of mono- and multivalent salt. Molecular dynamics simulations with enhanced umbrella sampling have been utilised in combination with the experimental techniques of zeta-potential measurements, dynamic light scattering, and transmission electron microscopy. It was observed that tactoid formation and tactoidal dissolution due to overcharging occur upon the addition of trivalent salt. The overcharging effect was captured from calculated potential of mean force and confirmed from the zeta-potential, which changed sign from negative to positive when increasing the stoichiometric charge-ratio between the positive salt ions and the clay. Consequently, the gained information could provide useful physical insight of nanoplatelet interactions in the presence of multivalent ions. [ABSTRACT FROM AUTHOR]

The popularity and development of alternative energy vehicles have drawn critical attention to thermal safety concerns. The occurrence of fire and explosion due to thermal runaway propagation (TRP) has become a hurdle in developing new energy vehicles. Therefore, to study the TRP behavior of modules subjected to overcharged electrical abuse, we built a 1 × 5 pouch Li-ion battery module TRP model that combines a P2D electrochemical model and a 3D thermal runaway model. We present a complete analysis of TRP characteristics by examining TRP behavior under various design parameters such as thermal runaway trigger temperature (T TR), cell spacing (L), thermal conductivity (K), and heat dissipation coefficient (h). Increasing T TR can delay TR in each cell, effectively slowing the propagation speed, and TRP is prevented at T TR = 583 K. As L increases, the TRP is considerably extended, but TR in the overcharged cell is shortened. The higher K has a delaying impact on the TR of the overcharged cell but leads to a noticeably shorter TRP time. Higher h slows TRP and prolongs TR trigger time of the overcharged cell. We also investigated the intrinsic mechanism of TRP suppression by performing a heat flux analysis and screening several critical cases for TRP suppression. TRP's actual condition is delineated along a criticality line, distinguishing between propagation and non-propagation phases, and confirmed by experimental validation of typical TRP, critical TRP, and non-TRP cases. Furthermore, we studied the parameters requirement for battery module thermal management in the non-TRP region. These findings provide valuable insights for enhancing the safety design of battery systems and mitigating heat-related hazards. [Display omitted] • Develop a TRP model with P2D electrochemical and 3D thermal models. • Detailed analysis of thermal runaway propagation characteristics and behavior. • Screen several critical cases of TRP suppression. • Criticality boundary divides the TRP situation into safe and dangerous regions. • Obtain the non-TRP battery module design parameters requirements. [ABSTRACT FROM AUTHOR]

The role of hydrolyzable metal ions in the adsorption of anionic surfactants on a negatively charge surface is studied by electrophoresis and phase transfer experiments. The notion that the presence of such hydrolyzable species (activators) can promote flotation is not new, but a detailed mechanistic explanation is lacking. We relate the role of activators to the phenomenon of overcharging, which has been studied rather extensively within colloid and interface science. The experiments conducted in this article show that overcharging is a necessary condition for the adsorption of an anionic surfactant on a negatively charged surface and that the hydrophobization of the studied particles is most effective when overcharging is most pronounced.

The spontaneous encapsulation of genomic and non-genomic polyanions by coat proteins of simple icosahedral viruses is driven, in the first instance, by electrostatic interactions with polycationic RNA binding domains on these proteins. The efficiency with which the polyanions can be encapsulated in vitro, and presumably also in vivo, must in addition be governed by the loss of translational and mixing entropy associated with co-assembly, at least if this co-assembly constitutes a reversible process. These forms of entropy counteract the impact of attractive interactions between the constituents and hence they counteract complexation. By invoking mass action-type arguments and a simple model describing electrostatic interactions, we show how these forms of entropy might settle the competition between negatively charged polymers of different molecular weights for co-assembly with the coat proteins. In direct competition, mass action turns out to strongly work against the encapsulation of RNAs that are significantly shorter, which is typically the case for non-viral (host) RNAs. We also find that coat proteins favor forming virus particles over nonspecific binding to other proteins in the cytosol even if these are present in vast excess. Our results rationalize a number of recent in vitro co-assembly experiments showing that short polyanions are less effective at attracting virus coat proteins to form virus-like particles than long ones do, even if both are present at equal weight concentrations in the assembly mixture. [ABSTRACT FROM AUTHOR]

Using the hypernetted-chain/mean spherical approximation (HNC/MSA) integral equations we study the electrical double layer inside and outside a model charged cylindrical vesicle (nanopore) immersed into a primitive model macroions solution, so that the macroions are only present outside the nanopore, i.e., the vesicle wall is impermeable only to the external macroions. We calculate the ionic and local linear charge density profiles inside and outside the vesicle, and find that the correlation between the inside and outside ionic distributions causes the phenomena of overcharging (also referred to as surface charge amplification) and/or charge reversal. This is the first time overcharging is predicted in an electrical double layer of cylindrical geometry. We also report the new phenomenon of double overcharging. The present results can be of consequence for relevant systems in physical-chemistry, energy storage and biology, e.g., nanofilters, capacitors and cell membranes. [ABSTRACT FROM AUTHOR]

• A new solution to overcharging problem of cascaded latent heat storage system. • Overcharging time and overcharging time ratio reduce by up to 89.66% and 91.93% • Mean total heat storage rate increases by 67.69% during the melting process. • Tuned porosity arrangement prolongs discharging time and increases discharged heat. • Optimal tuned porosity arrangement is 0.90–0.95–0.97 for a three stage system. Cascaded latent heat storage (CLHS) has been used for building heating to balance renewable energy supply–demand mismatch and improve thermodynamic performance. In a cascaded latent heat storage system, the asynchronous phase transformation process of phase change materials (PCMs) at each stage leads to an overcharging problem, which reduces the heat storage rate and increases the heat loss. This study proposes a new solution to overcome this problem by embedding porous media with tuned porosity arrangement in cascaded PCMs. A 3-D transient numerical model is established to investigate the effects of tuned porosity arrangement on the charging and discharging performance of a CLHS system. The results show that this solution improves the synchronization of the phase transformation process of the PCMs to increase the latent heat storage rate and eventually the total heat storage rate of the system. Compared with a uniform porosity arrangement, the overcharging time and the overcharging time ratio of the system with tuned porosity arrangement decrease up to 89.66% and 91.93%, while the mean total heat storage rate increases by 73.21% during the melting process. In addition, the tuned porosity arrangement is beneficial to prolong heat supply time and increase the accumulated discharged heat. In all cases, the optimal tuned porosity arrangement is 0.90–0.95–0.97. The CLHS system with tuned porosity arrangement has the general good performance under different charging and discharging conditions. The proposed solution provides guidance for performance enhancement and optimization of CLHS systems for building heating. [ABSTRACT FROM AUTHOR]

• The overcharging behaviors of lithium-ion batteries are investigated. • The influence of overcharge depth and number of cycles are examined. • The EIS and IC-DV analysis are used to diagnose cells degradation. • Degradation modes during overcharging are identified and quantified. • Non-destructive fault diagnosis method is put forward. This paper explores the major degradation characteristics of commercial lithium-ion battery cells with nickel–cobalt-aluminum-oxide (NCA) electrode during cyclic overcharging, and proposes non-destructive methods for detecting overcharging degradation failure. The experimental results show that battery capacity drops significantly with increasing overcharge depth and number of cycles especially during the first three cycles and when the charging termination voltage is set to 5 V. At the same time, the cell overcharge tolerance decreases with the cyclic overcharging. The combination of the electrochemical impedance spectroscopy and the incremental capacity and differential voltage analysis is used to diagnose cell degradation during cyclic overcharging. Three main degradation modes are identified and quantified by extracting characteristic parameters such as internal resistance and peak, valley, and curve position changes of incremental capacity curves. It is concluded that loss of lithium inventory and loss of active materials are the most dominant degradation modes during cyclic overcharging. Besides, the sharp increase of the third peak on incremental capacity curves has been identified as a unique feature of overcharging degradation, which can be used for diagnosing cyclic overcharging-induced degradation for batteries with NCA cathode. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of different organic acids and their influence on the pH-dependent charging, salt tolerance and so the colloidal stability of magnetite nanoparticles are compared. Adsorption isotherms of citric acid – CA, gallic acid – GA, poly(acrylic acid) – PAA, poly(acrylic-co-maleic acid) – PAM and humic acid – HA were measured. The pH-dependent charge state of MNPs was characterized by electrophoretic mobility and their aggregation by dynamic light scattering. The salt tolerance was tested in coagulation kinetic experiments. Although the adsorption capacities, the type of bonding (either H-bonds or metal ion-carboxylate complexes) and so the bond strengths are significantly different, the following general trends have been found. Small amount of organic acids at pH<∼8 (the pH of PZC of magnetite) – relevant condition in natural waters – only neutralizes the positive charges, and so promotes the aggregation and sedimentation of nanoparticles. Greater amounts of organic acid, above the charge neutralization, cause the sign reversal of particle charge, and at high overcharging promote stabilization and dispersing. The thicker layer of PAA, PAM and HA provides better electrosteric stability than CA and GA. GA undergoes surface polymerization, thereby improving stabilization. The organic acids studied here eliminate completely the pH sensitivity of amphoteric magnetite, but only the polyanionic coverage provides significant increase in resistance against coagulating effects of salts at neutral pH commonly prevailing in natural waters. [Copyright &y& Elsevier]

Abstract: Charging and aggregation of negatively charged carboxyl latex particles in the presence of positively charged linear oligoamines containing 1–6 amine groups were investigated by electrophoretic mobility and dynamic light scattering. The oligoamines of low valence resemble simple inert salts and destabilize the suspensions by screening their charge. The oligoamines of higher valence induce overcharging at low concentrations, whereby destabilization is triggered by charge neutralization. At higher concentrations, destabilization is also induced by screening. The onset of first fast aggregation regime scales with the inverse six power of the valence in agreement with the Schulze–Hardy rule. The aggregation rates can be relatively well described by the DLVO theory which indicates that the interactions are governed by van der Waals and electrostatic double layer forces. [Copyright &y& Elsevier]

Abstract: Charging properties and colloidal stability of negatively charged polystyrene latex particles were investigated in the presence of linear poly(ethylene imine) (LPEI) of different molecular masses by electrophoresis and dynamic light scattering (DLS). Electrophoretic mobility measurements illustrate that LPEI strongly adsorbs on these particles leading to charge neutralization at isoelectric point (IEP) and charge reversal. Time-resolved DLS experiments indicate that the aggregation of the latex particles is rapid near the IEP and slows down away from this point. Surprisingly, the colloidal stability does not depend on the molecular mass, which indicates that the adsorbed LPEI layer is rather homogeneous. [Copyright &y& Elsevier]

Abstract: Surface charges and electrokinetic charges are very different double layer characteristics. It is mandatory to discriminate between them. If for a given system both of them are known, much relevant double layer information becomes accessible. The present state of this juxtapositioning is reviewed on the basis of real physical measurements with well-defined systems. The added information includes counterion adsorption and stagnant layer conduction. Special attention will be paid to overcharging, including an option for distinguishing between interpretation in terms of specific adsorption and ion correlations. [Copyright &y& Elsevier]

Abstract: Sulfate-terminated latex particles were investigated in the presence of poly(diallyldimethyl ammonium chloride) (PDADMAC) at pH 4.0 in aqueous KCl electrolyte solutions by dynamic light scattering and electrophoresis, in particular, at high ionic strengths. The polyelectrolyte adsorbs to the latex particles quantitatively until the adsorption plateau is reached. The adsorbed amount at this plateau and the corresponding layer thickness increase with increasing ionic strength. The resulting layers have a thickness of several nanometers. Colloidal stability is qualitatively consistent with electrostatic double layer forces, especially since the system can be fully destabilized at high ionic strengths even at high polyelectrolyte doses. Additional attractive forces due to lateral charge heterogeneities seem to contribute to the destabilization of the system, even for the adsorbed layers in the saturated state. However, this layer does not provide any additional stabilization mechanism due to steric repulsion forces, since the adsorbed polyelectrolyte layers are thin and laterally heterogeneous even in their saturated state. [Copyright &y& Elsevier]

Slight overcharging cycling occurs due to the malfunction of charge control, inconsistency of lithium-ion batteries and inappropriate battery management. It is important to find whether it causes heat accumulate, increases the temperature of battery and triggers thermal runaway. The results of thermal stability test of slightly overcharged batteries indicate that the thermal stability of slightly overcharged battery decreases due to the cathode structure change when the voltage is less than 4.6 V. When it is greater than 4.6 V, lithium plating also makes battery thermal stability decrease. The results of heat generation and thermal runaway tests of batteries with and without current interruption device indicate that the internal resistance increase after slight overcharging is why the heat generation of battery increases. The heat generation induced by side reaction increases when the temperature reaches the threshold. The temperature threshold of exothermic reactions decreases during charging compared to that during rest with the same state of charge (SOC). Although the cycling is interrupted, thermal runaway still occurs. The battery with lower temperature and higher SOC is more dangerous than that with higher temperature and lower SOC in some cases. It is important to control SOC and temperature during charging. • Lithium plating and cathode structure affect thermal stability of the overcharged battery. • Ohmic heat dominates the heat generation during slight overcharging cycling. • Thermal stability of battery decreases during charging compared to rest. • Both high temperature and SOC influence thermal stability of battery. • Abnormal heat generation during CV mode can be used as fault diagnosis parameter. [ABSTRACT FROM AUTHOR]

Abstract: A discussion is given of the experimental evidence for overcharging, also known as charge reversal. The phenomenon is very common. The most general explanation is specific chemical adsorption. However, overcharging can also be explained on the basis of ion-ion correlations, which is rather a physical type of interpretation, and which can also be specific. Several theories have been developed for that. So, there is the luxury problem that two alternative explanations are available for the same observation. The purpose of this paper is to consider the various approaches critically and try to devise experimental options to discriminate between the two interpretations. [Copyright &y& Elsevier]

Previous studies on the surface charge and electrokinetic charge on silver iodide as a function of the pAg in the presence of some monovalent and trivalent cations as the counterions were extended to include the influence of pH. The main reason for this study was to investigate the possible propensity of overcharging by adsorption of hydrolyzed counterions. It was found that for K+ as the counterion the double layer properties could be well represented in terms of a simple Gouy-Stern model, without accounting for hydrolysis. However, with Al3+ or La3+ as the counterions, adsorption of hydrolyzed species takes place when the pH is high enough, leading to electrokinetic charge reversal. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a model for flooded and VRLA batteries that is parameterized by impedance spectroscopy and includes the overcharging effects to allow charge-acceptance simulations (e.g. for regenerative-braking drive-cycle profiles). The full dynamic behavior and the short-term charge/discharge history is taken into account. This is achieved by a detailed modeling of the sulfate crystal growth and modeling of the internal gas recombination cycle. The model is applicable in the full realistic temperature and current range of automotive applications. For model validation, several load profiles (covering the dynamics and the current range appearing in electrically assisted or hybrid cars) are examined and the charge-acceptance limiting effects are elaborately discussed. The validation measurements have been performed for different types of lead–acid batteries (flooded and VRLA). The model is therefore an important tool for the development of automotive power nets, but it also allows to analyze different charging strategies and energy gains which can be achieved during regenerative-braking. [Copyright &y& Elsevier]

Abstract: Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophoretic measurements as well as Monte Carlo simulations of the electrokinetic potential for the surface of calcium silicate hydrate (Ch name="sbnd" />H), which is the major constituent of hydrated cement. In the simulations, the surface charge of Ch name="sbnd" />H nanoparticles in equilibrium with the ionic solution is determined by a single site characteristic and electrostatic interactions between all explicit charges at the surface and in the electric double layer. We will show that ordinary electrostatic interactions are enough to describe all experimental observations. Actually, an excellent agreement is found between experimental and simulated results without any fitting parameter, both with respect to surface titration and electrokinetic behaviour. The agreement extends over a wide range of electrostatic coupling, from a weakly charged surface with mainly monovalent counter-ions to a highly charged one with divalent counter-ions. [Copyright &y& Elsevier]

Abstract: Overcharging, also called charge reversal or charge inversion, is the occurrence of electric double layers in which, as measured by electrokinetics or interaction, there is more countercharge than charge on the surface. The trend is that the propensity of overcharging increases with the valency of the counterion. For the interpretation of this phenomenon, disparate explanations have been forwarded and elaborated that, briefly, can be distinguished as “chemical” (specific adsorption, …) and “physical” (ion correlations, …). In the present paper, an analysis of this disparity will be given. In particular, types of experiments will be proposed which can help to discriminate. [Copyright &y& Elsevier]

Abstract: This paper presents for the first time an impedance-based non-linear model for lead-acid batteries that is applicable in all operational modes. An overcharging model describes the accumulation and depletion of the dissolved Pb2+ ions. This physical model has been added to the earlier presented model to expand the model validity. To properly represent the charge acceptance during dynamic operation, a concept of “hardening crystals” has been introduced in the model. Moreover, a detailed gassing and oxygen recombination model has been integrated. A realistic simulation of the overcharging behavior is now possible. The mathematical description is given in the paper. Simplifications are introduced that allow for an efficient implementation and for model parameterization in the time domain. A comparison between experimental data and simulation results demonstrates the achieved accuracy. The model enhancement is of major importance to analyze charging strategies especially in partial-cycling operation with limited charging time, e.g. in electrically assisted or hybrid cars and autonomous power supply systems. [Copyright &y& Elsevier]

Abstract: The modified Gouy–Chapman (MGC) theory has been used to study the electrical double layer near two charged plates immersed in a model electrolyte. The effects of assigning to the cations and anions different distances of closest approach to the charged surfaces are examined. The dependence of overcharging and charge reversal on the system parameters such as concentration, ion size and valence, is investigated both inside and outside the charged slit. [Copyright &y& Elsevier]

Abstract: Complexation between sodium carboxymethylcellulose (NaCMC) and ellipsoidal particles of oppositely charged β-FeOOH is studied using electric light scattering and electrophoresis. We focus on the complex behavior for overcharging of the particle surface. In this case, the fraction of condensed counterions on NaCMC is found to remain unchanged during polymer adsorption onto a weakly charged particle surface. Using the theory of Sens and Joanny, we evaluate the fraction of condensed counterions and compare it with results for nonadsorbed NaCMC. The polarization of condensed counterions along the chain of the adsorbed macromolecule is proved to create the electro-optical effect in suspensions stabilized by NaCMC adsorption. [Copyright &y& Elsevier]

Several theories (developed in the context of the so-called primitive models) argue that the classical Poisson–Boltzmann (PB) approach could fail to describe the electrical double layer in the case of high surface charge densities and/or ionic strengths. Under such conditions, the concentration of counterions in the vicinity of the surface would be larger than expected. What is more, the particle charge could be overcompensated (which is known as overcharging). This would lead to a considerable reduction in the magnitude of the ζ-potential (as compared with PB predictions) and, even, a reversal in its sign. Although these predictions are quite remarkable, these new approaches have been applied just scarcely in practice. Obviously, electrophoresis offers an excellent possibility of testing these theories. Accordingly, we have measured the electrophoretic mobility for latex particles with moderate and large surface charge densities at high ionic strengths. A commercial setup specifically designed for measuring extremely low mobilities has been used. The results have been interpreted with the help of the so-called hyper-netted-chain/mean-spherical approximation (HNC/MSA), a theory that includes ion size effects. In this way, overcharging has been experimentally investigated. Although the HNC/MSA is not a completely successful approach, our analysis suggests that the role of ion size correlations is important, particularly in electrolytes with a counterion valency of 2 or greater. [Copyright &y& Elsevier]

The influence of electrolyte additives on the safety and cycle life of 4V-class lithium cells is examined. The electrolyte solution employed was 1 MI LiClO4-propylene carbonate, the most widely used electrolyte in lithium battery research. The additives studied were ten organic aromatic compounds including biphenyl, cyclohexylbenzene and hydrogenated diphenyleneoxide. For safety, focus was given to the overcharging tolerance of the lithium cells. Biphenyl is well-known as an overcharge protection additive. The purpose of this work was to find additives with a higher oxidation potential and longer charge-discharge cycle life than biphenyl. The oxidation potentials and currents of the additives were measured to determine whether or not these compounds work as overcharge protection additives. Charge-discharge cycling efficiencies were examined for lithium metal anodes. The results showed that cyclohexylbenzene and hydrogenated diphenyleneoxide have a higher oxidation potential and a higher lithium cycling efficiency than biphenyl. [ABSTRACT FROM AUTHOR]

Electric light scattering method is used to study complexation between polyelectrolyte molecules and oppositely charged ellipsoidal particles. Attention is focused on the charge inversion that occurs when polyelectrolytes of different charge density, chain length and flexibility adsorb on oxide particles in water medium. In particular, we are interested in the similarity observed between the electrical properties of adsorbed and nonadsorbed polymers in regime of the surface charge overcompensation. The electro-optical results show that, at plateau adsorption, the particles assume the charge characteristic of the polymer. The extension of the adsorbed layer into a vertical direction, in which case the overcharging is caused by dangling loops and tails, is supposed to explain this observation. [Copyright &y& Elsevier]

Beginning with a construction based on a C-size (LR-14) battery container ('can'), encased in a strong PMMA-support and fitted with a removable cell top equipped with a manometer and a gas-outlet valve, a second and, finally, a more refined third generation cell was developed. The final (3rd generation) design provides additional options for experimental work. For example, the system can be flushed with inert gas; a regulating gas-flow valve has been fitted to feed precisely a gas chromatograph with the gaseous reaction products and a reference electrode to measure anode and cathode potentials individually has also been incorporated. Since AA cells (LR-6) are the dominant monocell battery size, test cells of the second generation were fitted with an adapter to accomodate either a C- or an AA-size. However, the most recent system was designed exclusively for AA-sized cans. The different cell designs are described and examples of their practical application (e.g., overcharge experiments) are given. [ABSTRACT FROM AUTHOR]

Abstract: Starting from a number of empirical papers by Matijević et al., the issue of coagulation of hydrophobic colloids by multivalent inorganic counterions is revisited. More recent information is also considered, and some important trends are confirmed and made more quantitative. It can be concluded that the high coagulating power of multivalent ions is mostly not a direct result of their high valence but caused by their propensity of building complexes with water that adsorb specifically. This mechanism requires a revision of the Schulze–Hardy rule interpretations. In addition, this finding helps to define conditions where overcharging by multivalent counterions can be attributed to ion correlations. [Copyright &y& Elsevier]