Electronic Structure Modeling of Electrochemical Reactions at Electrode/Electrolyte Interfaces in Lithium Ion Batteries

Leung, Kevin

doi:10.1021/jp308929a

Cited by 149 publications

(190 citation statements)

References 110 publications

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“…The higher average m.p.e. in the conventional electrolyte system, along with the very slow F À release during EC/DEC (1 M LiPF 6 ) decomposition as proposed in literature 44 , suggests the formation of an SEI composed primarily of broken-down organic molecules. Conversely, the controlled mass gains, lower average m.p.e.…”

Section: Articlesupporting

confidence: 57%

“…2. To model our electrolyte molecules in direct contact with a pristine anode surface 43,44 , we first optimize PYR 13 þ /FSI À and PYR 13 þ /TFSI À ion pairs on the Li 13 Si 4 surface (Fig. 2e,g, respectively).…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, TFSI À forms different products, including -SO 2 CF 3 groups, at much slower timescales. While some of the latter reduced fragments may eventually yield F À according to mechanisms proposed by Markevich et al 41 , slower F À release, similar to the slow PF 6 À decomposition in organic electrolyte 44 , is expected by TFSI À . We speculate that the fast release of F À and SO 2 may be correlated to the high cycling performance exhibited by the Si-PYR 13 FSI system.…”

Section: Articlementioning

confidence: 86%

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Stable silicon-ionic liquid interface for next-generation lithium-ion batteries

et al. 2015

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We are currently in the midst of a race to discover and develop new battery materials capable of providing high energy-density at low cost. By combining a high-performance Si electrode architecture with a room temperature ionic liquid electrolyte, here we demonstrate a highly energy-dense lithium-ion cell with an impressively long cycling life, maintaining over 75% capacity after 500 cycles. Such high performance is enabled by a stable half-cell coulombic efficiency of 99.97%, averaged over the first 200 cycles. Equally as significant, our detailed characterization elucidates the previously convoluted mechanisms of the solid-electrolyte interphase on Si electrodes. We provide a theoretical simulation to model the interface and microstructural-compositional analyses that confirm our theoretical predictions and allow us to visualize the precise location and constitution of various interfacial components. This work provides new science related to the interfacial stability of Si-based materials while granting positive exposure to ionic liquid electrochemistry.

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Section: Articlesupporting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Section: Articlementioning

confidence: 86%

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Stable silicon-ionic liquid interface for next-generation lithium-ion batteries

et al. 2015

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“…16,18,21,31,[38][39][40][41][42][43] Moreover, there is an increasing number of studies, both experimental and theoretical, on Li-ion transport within the electrolyte and in the electrodes. Other investigations focus on the boundary between the liquid electrolyte and the electrode, even the SEI as a whole, 21,25,42,[66][67][68][69][70][71] yet little attention has been put toward explaining transport mechanisms and predicting diffusion coefficients in the individual interphase components. Lithium ion diffusion in the SEI is thought to occur through grain boundaries, through porous regions, or through interstitials and vacancies.…”

mentioning

confidence: 99%

Ion Diffusivity through the Solid Electrolyte Interphase in Lithium-Ion Batteries

Benitez

Seminario

2017

J. Electrochem. Soc.

126

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Understanding the transport properties of the solid electrolyte interphase (SEI) is a critical piece in the development of lithium ion batteries (LIB) with better performance. We studied the lithium ion diffusivity in the main components of the SEI found in LIB with silicon anodes and performed classical molecular dynamics (MD) simulations on lithium fluoride (LiF), lithium oxide (Li 2 O) and lithium carbonate (Li 2 CO 3 ) in order to provide insights and to calculate the diffusion coefficients of Li-ions at temperatures in the range of 250 K to 400 K, which is within the LIB operating temperature range. We find a slight increase in the diffusivity as the temperature increases and since diffusion is noticeable at high temperatures, Li-ion diffusion in the range of 1300 K to 1800 K was also studied and the diffusion mechanisms involved in each SEI compound were analyzed. We observed that the predominant mechanisms of Li-ion diffusion included vacancy assisted and knock-off diffusion in LiF, direct exchange in Li 2 O, and vacancy and knock-off in Li 2 CO 3 . Moreover, we also evaluated the effect of applied electric fields in the diffusion of Li-ions at room temperature. The continuous demand for smart phones, tablets and other mobile devices has enormously promoted the improvement of Li-ion batteries. Moreover, volatile oil prices, pollution and climate change concerns have further increased the need for energy storage devices for renewable energies and electric vehicles. The latter applications require batteries with even higher energy density, better cycle life, better power performance, lower cost and improved safety.1 Therefore, improving and increasing the fundamental scientific knowledge of lithium ion batteries is essential for their continual advancement.A key component in lithium ion batteries is the solid electrolyte interphase (SEI) film. The SEI film is a thin passivating layer that is initially formed, on both anode and cathode surfaces, from the reduction of the electrolyte during the first charging/discharging cycles. [2][3][4][5][6][7][8][9] It consists of a mixture of inorganic and organic products, such as LiF, Li 2 O and LiCO 3 , and (CH 2 OCO 2 Li) 2 , ROCO 2 Li and ROLi, where R is an organic group such as CH 2 , CH 3 , CH 2 CH 2 , CH 2 CH 3 , CH 2 CH 2 CH 3 that depends on the electrolyte solvent.10-24 Proposed structure models suggest that a dense layer of inorganic products is found near the electrode (inner layer) followed by a porous organic layer near the electrolyte/SEI interface (outer layer). [19][20][21] In carbon anodes, the SEI layer prevents further decomposition of the electrolyte by hindering electron transport from the electrode to the electrolyte, and by blocking the travel of solvent molecules to the active surface of the anode, where they can react with lithium ions and electrons. 25 In silicon anodes, i.e., the huge volume expansion of the anode creates cracks in the SEI layer and generates new surfaces which are freshly exposed to the electrolyte. 26 In both carbon and si...

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“…Models are available at different scales based on molecular dynamics (MD), density functional theory (DFT), kinetic Monte Carlo (kMC), and partial differential equations (PDEs). MD simulations have been used to determine and analyze basic atomistic z E-mail: u.krewer@tu-braunschweig.de processes 6,10,11 and usually assume ideal surfaces or solutions. DFT has been applied to determine energy barriers and standard state potentials 12 and transport processes in the solid film.…”

mentioning

confidence: 99%

Multi-Scale Simulation of Heterogeneous Surface Film Growth Mechanisms in Lithium-Ion Batteries

Röder

Braatz

Krewer

2017

J. Electrochem. Soc.

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A quantitative description of the formation process of the solid electrolyte interface (SEI) on graphite electrodes requires the description of heterogeneous surface film growth mechanisms and continuum models. This article presents such an approach, which uses multi-scale modeling techniques to investigate multi-scale effects of the surface film growth. The model dynamically couples a macroscopic battery model with a kinetic Monte Carlo algorithm. The latter allows the study of atomistic surface reactions and heterogeneous surface film growth. The capability of this model is illustrated on an example using the common ethylene carbonatebased electrolyte in contact with a graphite electrode that features different particle radii. In this model, the atomistic configuration of the surface film structure impacts reactivity of the surface and thus the macroscopic reaction balances. The macroscopic properties impact surface current densities and overpotentials and thus surface film growth. The potential slope and charge consumption in graphite electrodes during the formation process qualitatively agrees with reported experimental results. A long lifetime for lithium-ion batteries is key to reducing battery cost and increasing acceptance for new applications. The most important but still not well understood aging phenomenon is the growth of a solid film at graphite negative electrodes.1-3 Graphite is the common negative electrode and operates at conditions outside the electrochemical stability window of the electrolyte.2,4 Its decomposition takes place at the surface of the electrode particles and leads to the formation of a surface film, i.e. solid electrolyte interface (SEI). The SEI is mainly built during the first cycles prior to use and is considered to be part of the manufacturing process. 5 The aim of the formation process is to create an interface that is a good lithium-ion conductor but insulating for electrons and prohibits direct contact between electrode and electrolyte in order to provide good performance and long lifetime.4 Different compositions of the film have been proposed by different research groups. 6,7 Since the composition and structure and so the film characteristic is determined during the first cycles, 7 a detailed understanding of this growth mechanism is needed to improve cycling performance.The SEI is formed by a complex mechanism. 5 An atomistic reaction mechanism involves lithium salt and solvent as reactants as well as a variety of different organic and inorganic intermediates and solid products. 7,8 The observation of the formation process is challenging, because of the film's thickness of only several nanometers. Additionally, macroscopic properties such as particle size or operating conditions, e.g. C-rate and environmental temperature, have an important impact on the formation process.3,4 Although SEI film formation has been studied for decades using experimental and simulation-based methods, the exact mechanism of chemical and electrochemical reactions and the growth of the solid fi...

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Electronic Structure Modeling of Electrochemical Reactions at Electrode/Electrolyte Interfaces in Lithium Ion Batteries

Cited by 149 publications

References 110 publications

Stable silicon-ionic liquid interface for next-generation lithium-ion batteries

Stable silicon-ionic liquid interface for next-generation lithium-ion batteries

Ion Diffusivity through the Solid Electrolyte Interphase in Lithium-Ion Batteries

Multi-Scale Simulation of Heterogeneous Surface Film Growth Mechanisms in Lithium-Ion Batteries

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