A thermal-electrochemical model that gives spatial-dependent growth of solid electrolyte interphase in a Li-ion battery

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160

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In this study, a phase-field model is developed to simulate the microstructure morphology evolution that occurs during solid electrolyte interphase (SEI) growth. Compared with other simulation methodologies, the phase-field method has been widely applied in the solidification modeling that has great relevance to SEI formation. The developed model can simulate SEI structure and morphology evolution, and can predict SEI thickness growth rate. X-ray photoelectron spectroscopy (XPS) experiments are performed to confirm the major SEI species as LiF, Li 2 O, ROLi, and ROCO 2 Li. Transmission electron microscopy (TEM) experiment is performed to present the SEI layer structures. The experiments reduce the complexity of the model development and provide validation to some extent. Fick's law and mass balance are applied to investigate lithium-ion concentration distributions and diffusion coefficients in different types of SEI layers predicted by the phase-field simulations. Simulation results show that lithium-ion diffusion coefficients between 298 K and 318 K are 1. 340-7.328 Lithium-ion batteries (LIBs) are widely used in many applications, such as cell phones, electric vehicles (EVs), and other energy storage modules. However, LIBs suffer from severe performance degradation due to undesired chemical reactions, 1 ageing, 2,3 corrosion, 4-6 compromised structural integrity, 7,8 and thermal runaway. 9-11 The degradation occurs during both calendar and cycling lifespans, and reduces the longevity of LIBs. Recently, much attention has been focused on LIB material decomposition, 12 e.g., the formation and growth of new components [13][14][15][16][17][18][19] due to undesired side reactions. 1,20 The main degradation mechanisms in LIBs vary with different active materials, 2 however, it is well known that a carbonaceous lithium-intercalation electrode in contact with electrolyte solution becomes covered by a passivation layer called a solid electrolyte interphase (SEI). While SEI can prevent the exfoliation of graphite materials and inhibit further electrolyte decomposition.21 SEI layer growth can also cause battery capacity fade and increase cell internal resistance. 17,[22][23][24][25][26] Therefore, the study of SEI plays a key role in battery degradation and other related performance improvement research. Many studies have been published in SEI computational and experimental studies, including but not limited to. [27][28][29][30] Many researchers have investigated SEI in LIBs in terms of structure, 7,8,29,31-33 formation and composition, 20,22,27 and thickness growth prediction and measurement. 15,16,34,35 SEI is believed to have a multilayered structure: a compact layer of inorganic components (e.g., LiF, Li 2 O) close to graphite electrode followed by a porous organic layer (e.g., ROLi, ROCO 2 Li) close to the electrolyte solution phase. 22,29,[31][32][33] The composition of SEI depends on the electrode materials and electrolyte composition.27 Broussely et al. investigated the mechanism of lithium loss in LIBs during ...

“…Here, we assume the resistance of SEI layer is proportional to its thickness. 36,38,59 Adopting our previous studies, 36,38 the resistance of SEI layer can be estimated by…”

Section: Resultsmentioning

confidence: 99%

“…E act is the corresponding activation energy, which is 4 kJ/mol for solid phase. 38 Calculated resistances at various temperatures are shown in Figure 16. The resistances decrease with rising temperatures for all three different SEI structures.…”

Section: Resultsmentioning

confidence: 99%

Simulation and Experiment on Solid Electrolyte Interphase (SEI) Morphology Evolution and Lithium-Ion Diffusion

Guan

Liu

Lin

2015

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160

118

“…59,60 F, R and T represent Faraday's constant, the universal gas constant and the absolute temperature, respectively. Specific values for i 0,SEI will be given in the Results and discussion section by Equation 11.…”

Section: Model Developmentmentioning

confidence: 99%

“…the sudden decrease -in usable capacity after several hundred cycles. 53,55,59,61,63 In these models, this non-linear aging behavior can be emulated by a high power fade, though, which shortens charging and discharging due to high overpotentials that decrease the usable capacity. 43,61 Measurements in literature ascribe this non-linear aging behavior to lithium plating 64,65 as well as to degradation mechanisms on the cathode.…”

Section: Model Developmentmentioning

confidence: 99%

A SEI Modeling Approach Distinguishing between Capacity and Power Fade

Kindermann

Keil

Frank

et al. 2017

In this paper we introduce a pseudo two-dimensional (P2D) model for a common lithium-nickel-cobalt-manganese-oxide versus graphite (NCM/graphite) cell with solid electrolyte interphase (SEI) growth as the dominating capacity fade mechanism on the anode and active material dissolution as the main aging mechanism on the cathode. The SEI implementation considers a growth due to non-ideal insulation properties during calendar as well as cyclic aging and a re-formation after cyclic cracking of the layer during graphite expansion. Additionally, our approach distinguishes between an electronic (σ SEI ) and an ionic (κ SEI ) conductivity of the SEI. This approach introduces the possibility to adapt the model to capacity as well as power fade. Simulation data show good agreement with an experimental aging study for NCM/graphite cells at different temperatures introduced in literature. © The Author Lithium-ion batteries are one of the most promising candidates for energy storage in future stationary storage systems and electric vehicles.1-3 Enormous research efforts have been conducted to get a thorough understanding of the system "lithium-ion cell" and to further develop it for higher energy and power density, higher safety standards as well as longer cycle life. 4 The aging behavior of lithium-ion batteries has been a focus issue of battery research since the introduction of lithium-ion cells by Sony in 1991. 5 Reviews by Agubra et al., 6,7 Arora et al., 8 Aurbach et al., 9,10 Birkl et al., 11 Broussely et al., 12 Verma et al. 13 and Vetter et al. 14 are just a few examples of the extensive literature regarding aging behavior. Commonly accepted and experimentally verified aging phenomena as mentioned in the previously cited literature are electrolyte decomposition leading to solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) growth, solvent co-intercalation, gas evolution with subsequent cracking of particles, a decrease of accessible surface area and porosity due to SEI growth, contact loss of active material particles due to volume changes during cycling, binder decomposition, current collector corrosion, metallic lithium plating and transition-metal dissolution from the cathode. The listed aging mechanisms can be assigned to three different categories that are a loss of lithium-ions (LLI), an impedance increase and a loss of active material (LAM). 12,[15][16][17][18] The LLI is synonymous to a decrease in the amount of cyclable lithium-ions as they are trapped in a passivating film on either of the electrodes or in plated metallic lithium. Due to the growth of the passivating layers and/or the formation of rock-salt in the cathode (residue of the cathode active material after transition-metal dissolution), kinetic transport of lithium-ions through those inactive areas is limited and results in an impedance rise. An LAM can be caused by the dissolution of transition-metal-ions from the cathode bulk material, changes in the electrode composition and/or changes in crystal structure of the a...

“…Their common feature is that they couple a one dimensional model of charge and mass transport through the electrode to a one dimensional model of spherical diffusion inside active particles, resulting in a pseudo two-dimensional porous electrode (P2D) model. [23][24][25][26] Under low to moderate working conditions, the P2D model can be reduced to a single particle (SP) model. 27,28 In this approach, the electrode is represented by identical spherical particles, whose accumulated surface area is equivalent to the total active area of the solid phase in the porous electrode.…”

mentioning

confidence: 99%

Statistical Physics-Based Model of Solid Electrolyte Interphase Growth in Lithium Ion Batteries

Tahmasbi

Kadyk

Eikerling

2017

The article presents a statistical physics-based model for the growth of the solid electrolyte interphase (SEI) in the negative electrode of lithium ion batteries. During battery operation, the SEI thickness grows by the reaction between lithium ions, electrons and solvent species on the surface of active particles at the negative electrode. The growth of the SEI layer causes a loss of lithium ions that induces capacity fade. In addition, it increases the ion transport resistance and decreases the total porosity. Our model employs a population balance formalism based on the Fokker-Planck Equation to describe the propagation of the particle density distribution function in the electrode. Structure-transforming processes at the level of individual particles are accounted for by using a set of kinetic and transport equations. These processes alter the particle density distribution function, and cause changes in battery performance. A parametric study of the model singles out the first moment of the initial SEI thickness distribution as the determining factor in predicting the capacity fade. The model-based treatment of experimental data allows analyzing processes that control SEI growth and extracting their controlling parameters. Lithium ion batteries (LIBs) are highly touted energy storage devices for portable electronics and electric vehicles.1 The LIB system consists of a negative electrode, a positive electrode, a separator, an electrolyte, and two current collectors. The most commonly used electrolytes are comprised of lithium salts, such as LiPF 6 in a solution of ethylene carbonate (EC) and dimethyl carbonate (DMC).1 The electrodes consist of randomly distributed and interconnected particles of active material, which store and release the lithium ions.Aging and degradation of LIBs have become major concerns for the operation of electric vehicles (EVs), which must fulfill exacting requirements in terms of durability, cyclability and overall lifetime. Battery aging is linked to the (electro-)chemical and mechanical degradation of the electrodes and the electrolyte.2 Three main degradation mechanisms prevail at the particle level during the cycling of LIBs:(1) growth of the solid electrolyte interphase (SEI) at the negative electrode, 2,3 (2) formation of cracks in the SEI layer at the negative electrode, 4 and (3) dissolution and isolation of nanocrystalline particles at the positive electrode.5 These processes lead to capacity fade and power loss.At the beginning of the battery life, particularly during the first cycle, the electrolyte undergoes reduction at the electrode/electrolyte interface, because the negative electrode operates at potentials that are outside of the electrochemical stability window of electrolyte components. This reduction is accompanied by the irreversible consumption of lithium ions.6 This process forms a passivating surface layer known as the solid electrolyte interphase. The SEI layer grows further during charging, thereby reducing the amount of active lithium ions. Moreover, this l...