Role of atomic level simulation in development of batteries (original) (raw)
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Chemistry of Materials, 2019
Polymer electrolytes constitute an attractive alternative to current liquid electrolytes used in Li-ion batteries. Unfortunately, the lithium-ion conductivities of the state-of-the-art polymer electrolytes are few orders of magnitude lower than those of liquid electrolytes at room temperature. In this work, we focus on poly(ethylene oxide) (PEO), which has shown the highest lithium ion conductivity in polymer electrolytes so far. At high salt concentrations, the lithium conductivity of a PEO electrolyte is strongly reduced because of the formation of ionic aggregates. Using molecular dynamics simulations and rigorously taking into account ionic correlations, we show how introducing a secondary site with a specific chemical structure in the backbone of PEO can greatly enhance the lithium conductivity of such concentrated electrolytes. In addition, we demonstrate how results based on the Nernst−Einstein equation can be highly misleading in the concentrated regime. We identify PEO-based carbonate and sulfonyl variants that, respectively, allow for significant ion dissociation and high cation transference number.
Phys. Chem. Chem. Phys., 2015
There is an increasing worldwide demand for high energy density batteries. In recent years, rechargeable Li-ion batteries have become important power sources, and their performance gains are driving the adoption of electrical vehicles (EV) as viable alternatives to combustion engines. The exploration of new Li-ion battery materials is an important focus of materials scientists and computational physicists and chemists throughout the world. The practical applications of Li-ion batteries and emerging alternatives may not be limited to portable electronic devices and circumventing hurdles that include range anxiety and safety among others, to their widespread adoption in EV applications in the future requires new electrode materials and a fuller understanding of how the materials and the electrolyte chemistries behave. Since this field is advancing rapidly and attracting an increasing number of researchers, it is crucial to summarise the current progress and the key scientific challenges related to Li-ion batteries from theoretical point of view. Computational prediction of ideal compounds is the focus of several large consortia, and a leading methodology in designing materials and electrolytes optimized for function, including those for Li-ion batteries. In this Perspective, we review the key aspects of Li-ion batteries from theoretical perspectives: the working principles of Li-ion batteries, the cathodes, anodes, and electrolyte solutions that are the current state of the art, and future research directions for advanced Li-ion batteries based on computational materials and electrolyte design.
Materials for Lithium Ion Batteries: Challenges for Numerical Simulations
Zeitschrift für Physikalische Chemie, 2012
ABSTRACT We present an overview of numerical challenges in simulating electronic and transport properties of battery assemblies. Li diffusion paths within inorganic materials (olivine phosphates) are investigated using a dedicated accelerated molecular dynamics approach. The need of many-body electronic structure calculations is illustrated for the evaluation of intercalation potentials (LDA/GGA+U) and of transport properties (LDA+DMFT). Steps towards the improvement of silicon based anodic materials are shown. All in all, the framework of an ab initio simulation platform for materials for power storage is sketched.
Ion Transport in Organic Electrolyte Solutions for Lithium-ion Batteries and Beyond
Journal of Energy and Power Technology, 2021
The performance of metal-ion batteries at low temperatures and their fast charge/discharge rates are determined mainly by the electrolyte (ion) transport. Accurate transport properties must be evaluated for designing and/or optimization of lithium-ion and other metal-ion batteries. In this review, we report and discuss experimental and atomistic computational studies on ion transport, in particular, ion diffusion/dynamics, transference number, and ionic conductivity. Although a large number of studies focusing on lithium-ion transport in organic liquids have been performed, only a few experimental studies have been conducted in the organic liquid electrolyte phase for other alkali metals that are used in batteries (such as sodium, potassium, magnesium, etc.). Atomistic computer simulations can play a primary role and predict ion transport in organic liquids. However, to date, atomistic force fields and models have not been explored and developed exhaustively to simulate such organic...
Molecular modeling studies of polymer electrolytes for power sources
Electrochimica Acta, 2005
Density functional theory and classical molecular dynamics simulations permit us to elucidate details of ionic and molecular transport useful for the design of polymer electrolyte membranes. We consider two systems of current interest: (a) ionic transport in polyethylene-oxide compared to that in a polyphosphazene membrane targeted to be a good ionic carrier but a bad water carrier and (b) transport of oxygen and protons through hydrated nafion in the vicinity of a catalyst phase. It is shown that in polyphosphazene membranes, nitrogen atoms interact more strongly with lithium ions than ether oxygens do. As a result of the different complexation of Li + with the polymer sites, Li + has a much higher diffusion coefficient in polyphosphazene than in polyethylene oxide electrolyte membranes, with the consequent relevance to lithium-water battery technology. For the hydrated membrane/catalyst interface, our simulations show that the Nafion membrane used in low-temperature fuel cells interacts strongly with the catalytic metal nanoparticles directing the side chain towards the catalyst surface. Results at various degrees of hydration of the membrane illustrate the formation of water clusters surrounding the polymer hydrophilic sites, and reveal how the connectivity of these clusters may determine the transport mechanism of protons and molecular species.
Characterisation and modelling of the transport properties in lithium battery gel electrolytes
Electrochimica Acta, 2004
A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no full characterisation or modelling study could be found in the literature. In this paper, which is the first part of a study of the transport in the ternary gel system PMMA/PC/LiClO 4 , the liquid electrolyte PC/LiClO 4 is characterised and modelled for concentrations between 0.1 and 2 M according to a previously employed methodology, based on electrochemical measurements. A model using concentration dependent interaction parameters proved to describe the results in the whole concentration region well. The cationic transport number and salt diffusivity were determined to be approximately 0.3 and 1e−10 m 2 /s, respectively. The mean ionic activity factor variations prove to be substantial. Furthermore, it was demonstrated that the inter-ionic friction was important to consider at concentrations above 1 M. The fundamental friction parameters determined in this part will be used in the following part of the study to describe the friction between ions and solvent.
Structure and Dynamics of Lithium Polymer Electrolytes
ECS Proceedings Volumes, 1999
The atomic structure and dynamics o f PEO-L1CIO4 and PEO-LiTFSI polymer electrolytes have been investigated by neutron scattering experiments and ab initio quantum chemical calculations. The Li+ ions are bonded to, on average, five ether-oxygen atoms o f the polymer host with an average bond length o f 2.1 A. No cation-anion pairing is observed. On a time scale o f 0.01-0.1 ns, the segmental motion o f the PEO chains is significantly altered by the introduction o f the salts compared to pure PEO. The cross-links through the L i-0 coordination bonds are believed to be responsible for the change in the dynamics. These results are consistent with a mechanism in which Li+ ion transport takes place through the dynamical formation and disruption o f L i-0 bonds.
The Journal of Physical Chemistry B, 2012
Improving ionic conductivity and lithium ion mobility in polymer electrolytes is important for their practical use for polymer electrolytes. In this study, a combination of molecular dynamics and Monte Carlo simulations were used to bring insight into lithium ion transport in poly(ethylene oxide) LiClO 4 polymer electrolytes next to both acidic and basic treated model alumina solid surfaces at 323, 348, and 373 K. The acidic treated system had hydrogens present on its surface, while the basic treated system did not. The results found reduced ion mobility near the surfaces and little change to overall conductivity away from the surface. However, ion diffusion was somewhat enhanced for the acidic treated system at 323 K in comparison with systems without any surface present, despite that close to the surface it was reduced. This was linked to long-ranged structural ordering of ions in the system brought on by strong interactions with the surface, which resulted in oscillations in lithium and ClO 4 − densities that were out of phase, reducing ion binding and enhancing diffusivities.
The sei model—application to lithium-polymer electrolyte batteries
Electrochimica Acta, 1995
In this work we studied interfacial phenomena in PEO-based composite polymer electrolytes (cpe) which were stabilized by a high-surface-area oxide matrix such as alumina or magnesia. In order to avoid both consumption of the electrolyte salt (by reaction with Li) and anode passivation, we used only thermodynamically stable anions such as I-and Br-. Two types of solid electrolytes have been studied: composite solid electrolytes (csetsalt-rich electrolytes which have an n to LiI ratio of 2.5-3 (n in P(EO)n), and t + close to unity and cpes which have an n to LiI ratio of 6-20. Using an ac technique and assuming a simple equivalent circuit, we determined the apparent thickness of the SE1 (L,,,), its resistance (Rs,,), apparent conductivity (usa,) and the apparent energy of activation for conduction (Eas,,). The effects of: inorganic oxide matrix, LiX salt, co-polymers and plasticizers on osE,, E$,, , L,,, and RsE, were determined.