Showing papers on "Ion published in 2016"
TL;DR: O2 removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) species.
Abstract: During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 A) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.
824 citations
TL;DR: Transient optoelectronic measurements combined with device simulations indicate that electric-field screening, consistent with ion migration, is similar in both high and low hysteresis CH3NH3PbI3 cells.
Abstract: Ion migration has been proposed as a possible cause of photovoltaic current–voltage hysteresis in hybrid perovskite solar cells. A major objection to this hypothesis is that hysteresis can be reduced by changing the interfacial contact materials; however, this is unlikely to significantly influence the behaviour of mobile ionic charge within the perovskite phase. Here, we show that the primary effects of ion migration can be observed regardless of whether the contacts were changed to give devices with or without significant hysteresis. Transient optoelectronic measurements combined with device simulations indicate that electric-field screening, consistent with ion migration, is similar in both high and low hysteresis CH3NH3PbI3 cells. Simulation of the photovoltage and photocurrent transients shows that hysteresis requires the combination of both mobile ionic charge and recombination near the perovskite-contact interfaces. Passivating contact recombination results in higher photogenerated charge concentrations at forward bias which screen the ionic charge, reducing hysteresis. Ion migration has been related to hysteresis in perovskite solar cells, but not all perovskite cells exhibit a hysteresis. Here, Caladoet al. show that ion migration occurs regardless of hysteresis, but photogenerated carriers screen the effects of ionic charge for some solar cell architectures.
604 citations
TL;DR: An optical frequency standard based on the E3 transition of a single trapped (171)Yb+ ion is experimentally investigated and a Ramsey-type excitation scheme that provides immunity to probe-induced frequency shifts is utilized.
Abstract: A twentyfold improvement in the accuracy of a single ytterbium ion atomic clock is achieved using the ion's electric octupole transition.
545 citations
TL;DR: The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength.
Abstract: Rational design and construction of Z-scheme photocatalysts has received much attention in the field of CO2 reduction because of its great potential to solve the current energy and environmental crises. In this study, a series of Z-scheme BiOI/g-C3N4 photocatalysts are synthesized and their photocatalytic performance for CO2 reduction to produce CO, H2 and/or CH4 is evaluated under visible light irradiation (λ > 400 nm). The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength. Emphasis is placed on identifying how the charge transfers across the heterojunctions and an indirect Z-scheme charge transfer mechanism is verified by detecting the intermediate I3(-) ions. The reaction mechanism is further proposed based on the detection of the intermediate (•)OH and H2O2. This work may be useful for rationally designing of new types of Z-scheme photocatalyst and provide some illuminating insights into the Z-scheme transfer mechanism.
524 citations
TL;DR: In this paper, the ability of Li-ion batteries to stabilize the oxygen holes generated by Li-removal and to achieve a reversible oxo-to peroxo-like (2O2−/(O2)n−) transformation is elucidated by means of a metal-driven reductive coupling mechanism.
Abstract: The energy density delivered by a Li-ion battery is a key parameter that needs to be significantly increased to address the global question of energy storage for the next 40 years. This quantity is directly proportional to the battery voltage (V) and the battery capacity (C) which are difficult to improve simultaneously when materials exhibit classical cationic redox activity. Recently, a cumulative cationic (M4+/M5+) and anionic (2O2−/(O2)n−) redox activity has been demonstrated in the Li-rich Li2MO3 family of compounds, therefore enabling doubling of the energy density with respect to high-potential cathodes such as transition metal phosphates and sulfates. This paper aims to clarify the origin of this extra capacity by addressing some fundamental questions regarding reversible anionic redox in high-potential electrodes for Li-ion batteries. First, the ability of the system to stabilize the oxygen holes generated by Li-removal and to achieve a reversible oxo- to peroxo-like (2O2−/(O2)n−) transformation is elucidated by means of a metal-driven reductive coupling mechanism. The penchant of the system for undergoing this reversible anionic redox or releasing O2 gas is then discussed with regards to experimental results for 3d- and 4d-based Li2MO3 phases. Finally, robust indicators are built as tools to predict which materials in the Li-rich TM-oxide family will undergo efficient and reversible anionic redox. The present finding provides insights into new directions to be explored for the development of high-energy density materials for Li-ion batteries.
417 citations
Book•
10 Apr 2016
TL;DR: In this paper, a two-phase liquid-metal magnetohydrodynamic (MHD) generator is used to eliminate dissipative boundary layer electrical shunts by displacing the slow moving, conducting liquid boundary layer adjacent the insulating walls of the generator with a thin gas layer.
Abstract: Dissipative boundary layer electrical shunts are eliminated in a two-phase liquid-metal magnetohydrodynamic (MHD) generator by displacing the slow moving, conducting liquid boundary layer adjacent the insulating walls of the generator with a thin gas layer. This is accomplished by injecting an inert gas into the generator channel in the direction of flow of the working fluid through the insulating walls at several locations through a narrow slit extending across the insulating walls.
384 citations
TL;DR: In this article, the authors investigated the role of ion motion in anomalous hysteresis in perovskite solar cells through a combination of electrical transport modelling and experimental measurements.
Abstract: The hypothesis that ion motion is responsible for anomalous hysteresis in the current–voltage curves of perovskite solar cells is investigated through a combination of electrical transport modelling and experimental measurements. In a combined computational and experimental study, good agreement is obtained between experiment and the results of a charge transport model covering mixed ionic-electronic conduction. Our model couples electrons, holes and defect mediated ion motion suggesting that slow moving ions are indeed the origin of the hysteresis. The magnitude of the ion diffusion coefficient required to match experiment and theory, ∼10−12 cm2 s−1, depends on the cell, but is similar to that predicted by microscopic theory of vacancy mediated diffusion. The investigation is extended to preconditioning procedures which are known to substantially influence the hysteresis. The method developed for solving the stiff equations in the drift diffusion model is widely applicable to other double layer problems occurring in electrochemical applications such as the evolution of transmembrane potentials in living cells.
370 citations
TL;DR: In this paper, an ordered mesoporous thin films of MoS2 can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g−1 for Li-ions and 118 m Ah g− 1 for Na-ions at 1 mV s−1.
Abstract: The ion insertion properties of MoS2 continue to be of widespread interest for energy storage. While much of the current work on MoS2 has been focused on the high capacity four-electron reduction reaction, this process is prone to poor reversibility. Traditional ion intercalation reactions are highlighted and it is demonstrated that ordered mesoporous thin films of MoS2 can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g−1 for Li-ions and 118 mAh g−1 for Na-ions at 1 mV s−1. Utilizing synchrotron grazing incidence X-ray diffraction techniques, fast electrochemical kinetics are correlated with the ordered porous structure and with an iso-oriented crystal structure. When Li-ions are utilized, the material can be charged and discharged in 20 seconds while still achieving a specific capacity of 140 mAh g−1. Moreover, the nanoscale architecture of mesoporous MoS2 retains this level of lithium capacity for 10 000 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for both ions in MoS2 is due to a pseudocapacitive mechanism.
363 citations
TL;DR: It is demonstrated that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn4+ with oxide ions without the sacrifice of electronic conductivity.
Abstract: Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g-1 based on solid-state redox reaction of oxide ions.
303 citations
TL;DR: In this paper, the structure, transport properties and different reported possible fading mechanisms of LNMO cathode are discussed detailedly, and the major goal of this review is to highlight new progress in using proposed strategies to improve the cycling stability and rate capacity of LiNi 0.5 O 4 (LNMO)-based batteries, including synthesis, control of special morphologies, element doping and surface coating etc., especially at elevated temperatures.
288 citations
TL;DR: The Li-excess oxide compound is one of the most promising positive electrode materials for next generation batteries exhibiting high capacities of >300 mA h g−1 due to the unconventional participation of the oxygen anion redox in the charge compensation mechanism as discussed by the authors.
Abstract: The Li-excess oxide compound is one of the most promising positive electrode materials for next generation batteries exhibiting high capacities of >300 mA h g−1 due to the unconventional participation of the oxygen anion redox in the charge compensation mechanism. However, its synthesis has been proven to be highly sensitive to varying conditions and parameters where nanoscale phase separation may occur that affects the overall battery performance and life. In addition, several thermodynamic and kinetic drawbacks including large first cycle irreversible capacity, poor rate capability, voltage fading, and surface structural transformation need to be addressed in order to reach commercialization. This review will focus on the recent progress and performance trends over the years and provide several guidelines and design considerations based on the library of work done on this particular class of materials.
TL;DR: Mesoporous soft carbon (MSC) as discussed by the authors was prepared from mesophase pitch using nano-CaCO3 as the template, and the crystalline structure of soft carbon consists of a disordered region with a large interlayer distance benefitting sodium ion insertion/extraction and a graphitic region with good electrical conductivity.
Abstract: Mesoporous soft carbon (MSC) was prepared from mesophase pitch using nano-CaCO3 as the template. The crystalline structure of soft carbon consists of a disordered region with a large interlayer distance benefitting sodium ion insertion/extraction and a graphitic region with good electrical conductivity favoring high rate performance. Additionally, the mesoporous structure not only shortens the path of ion diffusion but also facilitates the penetration of non-aqueous electrolytes, which can further enhance the electrochemical performance of MSC. Benefiting from its unique microstructure, the MSC delivers a reversible capacity of 331 mA h g−1 at 30 mA g−1, and retains a capacity of 103 mA h g−1 at 500 mA g−1 after 3000 cycles, indicating its excellent rate capability and cycling performance. Therefore, soft carbon with appropriate structure is expected to be another choice for anode materials of sodium ion batteries.
TL;DR: In this paper, the adverse effects of anode lithium plating on the electrochemical performance of lithium-ion batteries are presented, and various in situ and ex situ techniques for characterizing and detecting anode-lithium plating are summarized.
Abstract: Lithium-ion batteries (LIBs) are attractive candidates as power sources for various applications, such as electric vehicles and large-scale energy storage devices. However, safety and life issues are still great challenges for the practical applications of LIBs. Metallic lithium plating on the negative electrode under critical charging conditions accelerates performance degradation and poses safety hazards for LIBs. Therefore, anode lithium plating in LIBs has recently drawn increased attention. This article reviews the recent research and progress regarding anode lithium plating of LIBs. Firstly, the adverse effects of anode lithium plating on the electrochemical performance of LIBs are presented. Various in situ and ex situ techniques for characterizing and detecting anode lithium plating are then summarized. Also, this review discusses the influencing factors that induce anode lithium plating and approaches to mitigating or preventing anode lithium plating. Finally, remaining challenges and future developments related to anode lithium plating are proposed in the conclusion.
TL;DR: It is revealed that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP, which is much shorter than what it was thought to take.
Abstract: Understanding the influence of light on ion migration in organic–inorganic halide perovskite (OIHP) materials is important to understand the photostability of perovskite solar cells. We reveal that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP. The activation energies derived from conductivity measurement under 0.25 Sun decrease to less than one half of the values in the dark. A typical ion drift velocity in CH3NH3PbI3 polycrystalline films is 1.2 μm s−1 under 1 Sun, compared with 0.016 μm s−1 under 0.02 Sun. Ion migration across the photoactive layers in most OIHP devices thus takes only subseconds under 1 Sun illumination, which is much shorter than what it was thought to take. Most important of all, ion migration through a single crystal surface is still too slow to be observed even after illumination for two days due to the large ion diffusion activation energy, >0.38 eV.
TL;DR: Using mid-infrared laser–induced electron diffraction (LIED), the molecular structure of acetylene (C2H2) is imaged 9 femtoseconds after ionization and measurements are in excellent agreement with a quantum chemical description of field-dressed molecular dynamics.
Abstract: Visualizing chemical reactions as they occur requires atomic spatial and femtosecond temporal resolution. Here, we report imaging of the molecular structure of acetylene (C 2 H 2 ) 9 femtoseconds after ionization. Using mid-infrared laser–induced electron diffraction (LIED), we obtained snapshots as a proton departs the [C 2 H 2 ] 2+ ion. By introducing an additional laser field, we also demonstrate control over the ultrafast dissociation process and resolve different bond dynamics for molecules oriented parallel versus perpendicular to the LIED field. These measurements are in excellent agreement with a quantum chemical description of field-dressed molecular dynamics.
TL;DR: It is shown that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes, and the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment.
Abstract: One-atom-thick crystals are impermeable to atoms and molecules, but hydrogen ions (thermal protons) penetrate through them. We show that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes. Using electrical measurements and mass spectrometry, we found that deuterons permeate through these crystals much slower than protons, resulting in a separation factor of ≈10 at room temperature. The isotope effect is attributed to a difference of ≈60 milli–electron volts between zero-point energies of incident protons and deuterons, which translates into the equivalent difference in the activation barriers posed by two-dimensional crystals. In addition to providing insight into the proton transport mechanism, the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment.
TL;DR: In this article, the formation of a functional solid electrolyte interphase (SEI) in sodium ion batteries is hampered by the higher solubility of SEI components such as sodium salts in comparison to the lithium analogues.
Abstract: It is often stated that formation of a functional solid electrolyte interphase (SEI) in sodium ion batteries is hampered by the higher solubility of SEI components such as sodium salts in comparison to the lithium analogues. In order to investigate these phenomena, SEI formation and functionality, as well as cell self-discharge, are studied for the sodium ion system with comparative experiments on the equivalent lithium ion system. By conducting a set of experiments on carbonaceous anodes, the impact of SEI dissolution is tested. The results show that the SEI layer in sodium ion cells is inferior to that in lithium ion counterparts with regards to self-discharge; sodium cells show a loss in capacity at a dramatic rate as compared to the lithium counterparts when they are stored at sodiated and lithiated states, respectively, for a long time with no external applied current or potential. Also, synchrotron-based hard X-ray photoelectron spectroscopy measurements indicate that the major factor leading to inc...
TL;DR: It is shown that controlling the defect configuration in graphene is critical to overcome a fundamental limitation posed by quantum capacitance and opens new channels for ion diffusion.
Abstract: Defects are often written off as performance limiters. Contrary to this notion, it is shown that controlling the defect configuration in graphene is critical to overcome a fundamental limitation posed by quantum capacitance and opens new channels for ion diffusion. Defect-engineered graphene flexible pouch capacitors with energy densities of 500% higher than the state-of-the-art supercapacitors are demonstrated.
TL;DR: It is worth noting that NNU-1 not only shows a highly selective fluorescence quenching effect to Fe3+ ion in aqueous solution but also resists the interference of other metals including Fe2+ ion.
Abstract: A new metal–organic framework [Zn5(hfipbb)4(trz)2(H2O)2] (NNU-1) [H2hfipbb = 4,4′-(hexafluoroisopropylidene)bis(benzoic acid), Htrz = 1H-1,2,3-triazole] was assembled by hydrothermal synthesis. Single-crystal X-ray diffraction analysis reveals that NNU-1 displays a twofold interpenetrating three-dimensional (3D) framework with a {424·64}-bcu topology. Interestingly, the 3D framework contains a two-dimensional (2D) layered structure that consists of alternating left- and right-handed double helical chains. On the basis of the hydrophobic −CF3 groups from H2hfipbb ligand, NNU-1 possesses excellent stability in water. It is worth noting that NNU-1 not only shows a highly selective fluorescence quenching effect to Fe3+ ion in aqueous solution but also resists the interference of other metals including Fe2+ ion. Accordingly, NNU-1 probably functions as a potential promising fluorescence sensor for detecting Fe3+ ion with high sensitivity and selectivity.
TL;DR: In this paper, the authors designed a full sodium-ion battery based on nanostructured Na2Ti3O7 and VOPO4 materials as the anodes and cathodes, owing to their advantageous electrochemical features.
Abstract: In virtue of the abundant sodium resources, sodium ion batteries (SIBs) have been considered to be one of the promising alternatives to lithium ion batteries (LIBs). However, current research concentrates mostly on sodium ion half-cells, and the development of sodium ion full cells with high performance remains a critical challenge. Here we rationally designed a full sodium-ion battery based on nanostructured Na2Ti3O7 and VOPO4 materials as the anodes and cathodes, owing to their advantageous electrochemical features. The full cell outputs one of the highest operating voltages close to 2.9 V and delivers a large reversible capacity of 114 mA h g−1 at a rate of 0.1C. It also shows outstanding rate capability (∼74 mA h g−1 at 2C rate) and excellent cycling stability (92.4% capacity retention after 100 cycles). A high energy density of 220 W h kg−1 is achieved, which is comparable to the state-of-the-art LIBs. Moreover, the temperature-dependent charge–discharge tests indicate excellent capacity retentions in a wide temperature range of −20 to 55 °C.
TL;DR: In this article, the effect of NaFSI salt concentration in methylpropylpyrrolidinium (C3mpyr) FSI ionic liquid (IL) on the reversible plating and dissolution of sodium metal, both on a copper electrode and in a symmetric Na/Na metal cell, was investigated.
Abstract: Ambient temperature sodium batteries hold the promise of a new generation of high energy density, low-cost energy storage technologies. Particularly challenging in sodium electrochemistry is achieving high stability at high charge/discharge rates. We report here mixtures of inorganic/organic cation fluorosulfonamide (FSI) ionic liquids that exhibit unexpectedly high Na+ transference numbers due to a structural diffusion mechanism not previously observed in this type of electrolyte. The electrolyte can therefore support high current density cycling of sodium. We investigate the effect of NaFSI salt concentration in methylpropylpyrrolidinium (C3mpyr) FSI ionic liquid (IL) on the reversible plating and dissolution of sodium metal, both on a copper electrode and in a symmetric Na/Na metal cell. NaFSI is highly soluble in the IL allowing the preparation of mixtures that contain very high Na contents, greater than 3.2 mol/kg (50 mol %) at room temperature. Despite the fact that overall ion diffusivity decreases...
TL;DR: Operando23Na solid-state NMR and pair distribution function analysis experiments provide insights into the structure of hard carbon anodes in sodium-ion batteries.
TL;DR: In this article, the structural evolution localized at surface regions through electron diffraction and high resolution imaging analyses with aberration-corrected transmission electron microscopy and scanning transmission electron microscope were investigated.
TL;DR: An overview of the studies of ion pairing in aqueous media of the past decade is presented, and the importance of specific ion-pairing interactions between cations like Li(+) and Na(+) and anionic carboxylate and phosphate groups for the structure and functioning of large (bio)molecular systems is discussed.
Abstract: We present an overview of the studies of ion pairing in aqueous media of the past decade. In these studies, interactions between ions, and between ions and water, are investigated with relatively novel approaches, including dielectric relaxation spectroscopy, far-infrared (terahertz) absorption spectroscopy, femtosecond mid-infrared spectroscopy, and X-ray spectroscopy and scattering, as well as molecular dynamics simulation methods. With these methods, it is found that ion pairing is not a rare phenomenon only occurring for very particular, strongly interacting cations and anions. Instead, for many salt solutions and their interfaces, the measured and calculated structure and dynamics reveal the presence of a distinct concentration of contact ion pairs (CIPs), solvent shared ion pairs (SIPs), and solvent-separated ion pairs (2SIPs). We discuss the importance of specific ion-pairing interactions between cations like Li+ and Na+ and anionic carboxylate and phosphate groups for the structure and functioning...
TL;DR: It is demonstrated that a diglyme solvent shell encapsulating a sodium ion acts as a "nonstick" coating to facilitate rapid ion insertion into crystalline few-layer graphene and bypass slow desolvation kinetics.
Abstract: A maximum sodium capacity of ∼35 mAh/g has hampered the use of crystalline carbon nanostructures for sodium ion battery anodes. We demonstrate that a diglyme solvent shell encapsulating a sodium ion acts as a “nonstick” coating to facilitate rapid ion insertion into crystalline few-layer graphene and bypass slow desolvation kinetics. This yields storage capacities above 150 mAh/g, cycling performance with negligible capacity fade over 8000 cycles, and ∼100 mAh/g capacities maintained at currents of 30 A/g (∼12 s charge). Raman spectroscopy elucidates the ordered, but nondestructive cointercalation mechanism that differs from desolvated ion intercalation processes. In situ Raman measurements identify the Na+ staging sequence and isolates Fermi energies for the first and second stage ternary intercalation compounds at ∼0.8 eV and ∼1.2 eV.
TL;DR: The role of tunnel cations in governing the electrochemical properties of electrode materials is reported by focusing on potassium ions in α-MnO2, and the presence of cations inside 2 × 2 tunnels of manganese dioxide increases the electronic conductivity, and improves lithium ion diffusivity.
Abstract: Metal oxides with a tunnelled structure are attractive as charge storage materials for rechargeable batteries and supercapacitors, since the tunnels enable fast reversible insertion/extraction of charge carriers (for example, lithium ions). Common synthesis methods can introduce large cations such as potassium, barium and ammonium ions into the tunnels, but how these cations affect charge storage performance is not fully understood. Here, we report the role of tunnel cations in governing the electrochemical properties of electrode materials by focusing on potassium ions in α-MnO2. We show that the presence of cations inside 2 × 2 tunnels of manganese dioxide increases the electronic conductivity, and improves lithium ion diffusivity. In addition, transmission electron microscopy analysis indicates that the tunnels remain intact whether cations are present in the tunnels or not. Our systematic study shows that cation addition to α-MnO2 has a strong beneficial effect on the electrochemical performance of this material.
TL;DR: In this article, a finite volume method (FVM) for a pseudo-two-dimensional (P2D) Li-ion battery model suitable for the development of model-based advanced battery management systems is presented.
Abstract: Consumer electronics, wearable and personal health devices, power networks, microgrids, and hybrid electric vehicles (HEVs) are some of the many applications of lithium-ion batteries. Their optimal design and management are important for safe and profitable operations. The use of accurate mathematical models can help in achieving the best performance. This article provides a detailed description of a finite volume method (FVM) for a pseudo-two-dimensional (P2D) Li-ion battery model suitable for the development of model-based advanced battery management systems. The objectives of this work are to provide: (i) a detailed description of the model formulation, (i i) a parametrizable Matlab framework for battery design, simulation, and control of Li-ion cells or battery packs, (i i i) a validation of the proposed numerical implementation with respect to the COMSOL MultiPhysics commercial software and the Newman’s DUALFOIL code, and (iv) some demonstrative simulations involving thermal dynamics, a hybrid charge-discharge cycle emulating the throttle of an HEV, a model predictive control of state of charge, and a battery pack simulation. © 2016 The Electrochemical Society. [DOI: 10.1149/2.0291607jes] All rights reserved.
TL;DR: In this article, a charge localization mechanism due to fluctuations of the A-cations is proposed to screen carrier recombination, and the dynamics of the organic cations and that related to ion/defect migration are essentially coupled, with the methylammonium cations providing a local screening mechanism that may further speed up the ionic migration.
Abstract: Perovskite photovoltaics have made giant leaps in efficiency in just a few years from their inception. The employed solution synthesis techniques lead to inherently “soft” structures, which are properly sampled by dynamical approaches. The presence of two types of mobile ions, that is, the (organic) A-cations and ion/defects species in both the organic and inorganic lattices, gives rise to a broad spectrum of dynamical features. A charge localization mechanism due to fluctuations of the A-cations is proposed to screen carrier recombination. Defect/ion migration probably underlies the slow materials response under light irradiation related also to solar cell hysteresis. We also show how the dynamics of the organic cations and that related to ion/defect migration are essentially coupled, with the methylammonium cations providing a local screening mechanism that may further speed up the ionic migration. The use of less polar and less orientationally mobile A-cations may possibly slow down ion migration.
TL;DR: In this paper, two new chemically stable naphthalimide-based crystalline covalent organic frameworks (COFs) were first synthesized through a simple solvothermal route.
Abstract: Sustainable and resourceful organic materials are of long-standing interest for lithium-ion batteries. However, the lack of structural stability and cyclic capability is still the bottleneck for their practical use. Here, two new chemically stable naphthalimide-based crystalline covalent organic frameworks (COFs) were first synthesized through a simple solvothermal route. Excellent electrochemical performances were achieved as cathode materials for Li-ion batteries, mainly due to their open ordered nanoporous framework and robust structure. Moreover, their electrochemical performance can be improved by simply altering the linker of COFs at the molecular level. This work provides a possible approach to obtain the desired performance by structural modulation of organic materials.