Analysis of the Lithium-Ion Insertion Silicon Composite Electrode/Separator/Lithium Foil Cell

Chandrasekaran, Rajeswari; Fuller, Thomas F.

doi:10.1149/1.3589301

Cited by 60 publications

(44 citation statements)

References 45 publications

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“…In conventional porous-electrode theory the homogenized governing equations are used, and since the active particles are represented within the subgrid of the electrolyte domain, the faradaic current at the electrode-electrolyte interfaces appear as source terms in the conservation equations, while in the non-homogenous model charge transfer is modeled as an interface condition, not as a source term. 17 From concentrated solution theory, conservation of electric current and Li + flux is given by the following equations [17][18][19] :…”

Section: Finite Element Modelmentioning

confidence: 99%

“…The Butler-Volmer formulation determines the current through the electrode-electrolyte interface. 19 In order to model the dependence of intercalation flux on graphene plane orientation, the Butler-Volmer original formulation is modified by multiplying the term n • e θ (n is the intercalation surface normal vector and e θ is the unit vector that runs along the graphene planes); this ensures that the intercalation flux vanishes when the planes run perpendicular to the surface normal ( Fig. 2a).…”

Section: Finite Element Modelmentioning

confidence: 99%

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Direct In Situ Observation and Numerical Simulations of Non-Shrinking-Core Behavior in an MCMB Graphite Composite Electrode

Harris

Rahani

Shenoy

2012

J. Electrochem. Soc.

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Most models of battery charging assume a shrinking core model with a Lithium-rich shell and Li-poor core. In this study, we provide direct experimental evidence from in situ optical measurements and that suggests that the lithiation of (spherical) MCMB (meso carbon micro beads) particles do not follow the shriking-core model, even for particles which eventually become uniformly lithiated. We observe "hot spots" which expand until the particles are fully charged. The observations are explained using a microstructural model of MCMB particles that 1) accounts for their polycrystalline nature, 2) anisotropy in diffusion and 3) dependence of the intercalation rate at the surface on the orientation of the graphene planes. We show that our model reproduces the key features of the charging process observed in experiments. Implications of these results to Li-plating are discussed.

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Section: Finite Element Modelmentioning

confidence: 99%

Section: Finite Element Modelmentioning

confidence: 99%

Direct In Situ Observation and Numerical Simulations of Non-Shrinking-Core Behavior in an MCMB Graphite Composite Electrode

Harris

Rahani

Shenoy

2012

J. Electrochem. Soc.

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“…This will enable a clear explanation of the domain notation and boundary condition of the problem. From concentrated solution theory, conservation of electric current and Li + flux is given by the following equations: 23,25,26 ∇. (i el ) = 0…”

Section: Microstructural Modelmentioning

confidence: 99%

“…(N el ) = 0, [2] in which i el is the solution (electrolyte) phase current density, N el is the molar flux of lithium ion (Li+), c Li+ denotes Li + concentration in the electrolyte, φ el is the electric potential of the electrolyte phase, σ el is the electrolyte conductivity, D el is the electrolyte salt diffusivity, f A is the mean molar activity coefficient for the salt, t + is the transport number for Li + (assumed to be 0.38 26 ), and F is the Faraday's constant (96487 C/mol). According to Goldin et al, 23 f A can be assumed as a constant so that the thermodynamic term ∂ln f A ∂lnc Li+ is negligible.…”

Section: Microstructural Modelmentioning

confidence: 99%

“…4 is solved using only G . The Butler-Volmer formulation determines the current through the electrode-electrolyte interface 26 as [5] in which i 0 is the exchange current density for lithium insertion in the electrode, α a and α c are anodic and cathodic transfer coefficients for the electrochemical reactions at the composite electrode, R is the universal gas constant (8.314 J/K/mol), and η is the surface overpotential in the composite electrode defined as…”

Section: Microstructural Modelmentioning

confidence: 99%

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Role of Plastic Deformation of Binder on Stress Evolution during Charging and Discharging in Lithium-Ion Battery Negative Electrodes

Rahani

Shenoy

2013

J. Electrochem. Soc.

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We studied the mechanical damage within a lithium-ion graphite-based porous electrode during electrochemical cycling. The effects of charging-discharging rate and the variation in graphite diffusivity on average stress in the electrode cell were investigated. In particular, differences between spatial and average stress evolution in graphite particles were explored. We considered two different microstructures: a) graphite particles connected together with binder bridges and b) graphite particles encased in binder shells. Electrochemical charging-discharging in a composite electrode was simulated by spatially resolving the electrode and electrolyte phases. As indicated by experimental measurements, the binder is assumed to follow an elastic-plastic stress-strain relation. Average stress developed in the electrode was calculated for different binder yield-stress levels and an appropriate yield-stress value was chosen on the basis of experimental findings of the literature. We find the stress in the particles can be of the order of 43 MPa, and can be particularly large in regions where the particles come in close contact with their neighbors. The average stress in the electrodes, however, is the range of 10 MPa and is largely determined by the mechanical properties, in particular the yield stress of the binder. Computed stress profiles were compared qualitatively with experimental measurements using the wafer-curvature method. Elastic stresses and plastic strains predicted by 3D models are shown to be close to those predicted using simpler 2D models of the microstructure.Lithium-ion batteries have gained prominence in electronic devices such as cell phones and laptop computers owing to their high energy density that reduces their weight by half and their volume by 20% compared to other batteries, such as nickel-cadmium and nickel-metal-hydride. Lithium-ion batteries also present an attractive solution as renewable energy sources for the transportation industry. Lithium diffuses into the electrode, and hence they undergo volumetric expansion resulting in stress and large plastic deformations, which can potentially lead to the failure of electrodes and of the binder that holds the particles together. [1][2][3][4][5] To address the stability of lithium-ion batteries and to study the stress response during the electrochemical intercalation and deintercalation processes, theoretical and numerical investigations were conducted at particle and electrode levels.The mechanical properties of different binder types have been extensively studied. 6-10 Experimental investigation shows that in a lithium-ion battery electrode, binders form thin non-continuous layers on the particle surface. 11,12 Modeling the realistic morphology of binders is an extremely difficult task, which requires using image processing techniques. 13,14 To avoid this difficulty, Awarke et al. 11 assumed that the electrode pore volumes are fully occupied by binders that could overstate the stiffness of the electrode. They presented a 3D mesoscale model of th...

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Voltage Hysteresis of Silicon Nanoparticles: Chemo‐Mechanical Particle‐SEI Model

Köbbing,

Latz,

Horstmann

2023

Adv Funct Materials

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Silicon is a promising anode material for next‐generation lithium‐ion batteries. However, the volume change and the voltage hysteresis during lithiation and delithiation are two substantial drawbacks to their lifetime and performance. The reason for the voltage hysteresis in amorphous silicon nanoparticles covered by a solid‐electrolyte interphase (SEI) is investigated. Concentration gradients inside the nanoscale silicon cannot produce the massive stresses necessary to cause the reported voltage hysteresis. The chemo‐mechanical model shows that plastic deformation of the stiff, inorganic SEI during lithiation and delithiation reproduces the observed silicon open‐circuit voltage hysteresis. Additionally, the viscous behavior of the SEI explains the difference between the voltage hysteresis observed at low currents and after relaxation. It is concluded that the visco‐elastoplastic behavior of the SEI is the origin of the voltage hysteresis in silicon nanoparticle anodes. Thus, consideration of the SEI mechanics is crucial for further improvements.

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Analysis of the Lithium-Ion Insertion Silicon Composite Electrode/Separator/Lithium Foil Cell

Cited by 60 publications

References 45 publications

Direct In Situ Observation and Numerical Simulations of Non-Shrinking-Core Behavior in an MCMB Graphite Composite Electrode

Direct In Situ Observation and Numerical Simulations of Non-Shrinking-Core Behavior in an MCMB Graphite Composite Electrode

Role of Plastic Deformation of Binder on Stress Evolution during Charging and Discharging in Lithium-Ion Battery Negative Electrodes

Voltage Hysteresis of Silicon Nanoparticles: Chemo‐Mechanical Particle‐SEI Model

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