Enhanced Charging Kinetics of Porous Electrodes: Surface Conduction as a Short-Circuit Mechanism

Mirzadeh, Mohammad; Gibou, Frédéric; Squires, Todd M.

doi:10.1103/physrevlett.113.097701

Cited by 74 publications

(139 citation statements)

References 36 publications

(50 reference statements)

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“…Other capabilities, such as simulating electrochemical impedance outputs or others of the many additions that have been made to the original model implemented by Doyle et al [51] could also be added. For capacitive energy storage and desalination, the electrolyte model could also be extended to allow for diffuse charge in the electrode/electrolyte interface [103,105] or the double layers of charged porous separators [99][100][101][102], which also activates additional mechanisms for ion transport by surface conduction and electro-osmotic flow [99,104,186], which are neglected in traditional battery models.…”

Section: Discussionmentioning

confidence: 99%

Multiphase Porous Electrode Theory

Smith

Bazant

2017

J. Electrochem. Soc.

176

232

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Porous electrode theory, pioneered by John Newman and collaborators, provides a macroscopic description of battery cycling behavior, rooted in microscopic physical models. Typically, the active materials are described as solid solution particles with transport and surface reactions driven by concentration fields, and the thermodynamics are incorporated through fitting of the open circuit potential. However, this approach does not apply to phase separating materials, for which the voltage is an emergent property of inhomogeneous concentration profiles, even in equilibrium. Here, we present a general framework, "multiphase porous electrode theory", based on nonequilibrium thermodynamics and implemented in an open-source software package called "MPET". Cahn-Hilliard-type phase field models are used to describe the active materials with suitably generalized models of interfacial reaction kinetics. Classical concentrated solution theory is implemented for the electrolyte phase, and Newman's porous electrode theory is recovered in the limit of solid solution active materials with Butler-Volmer kinetics. More general, quantum-mechanical models of faradaic reactions are also included, such as Marcus-Hush-Chidsey kinetics for electron transfer at electrodes, extended for concentrated solutions. The full model and implementation are described, and a variety of example calculations are presented to illustrate the novel features of the software compared to existing battery models. Lithium-based batteries have growing importance in global society 1 as a result of increased prevalence of portable electronic devices, 2 and their enabling role in the transition toward renewable energy sources.3 For example, lithium batteries can help mitigate intermittency of renewable energy sources such as solar power, and lithium battery powered electric vehicles are facilitating movement away from liquid fossil fuels for transportation. Each of these growing areas demands high performance batteries, with requirements specific to the particular needs of the application driving specialized battery design for sub-markets. Thus, it is critical that battery models be based on the underlying physics, enabling them to greatly facilitate cell design to take best advantage of the existing battery technologies.Lithium-ion batteries are generally constructed using two porous electrodes and a porous separator between them. The porous electrodes consist of various interpenetrating phases including electrolyte, active material, binder, and conductive additive. A schematic is shown in Figure 1. In a charged state, most of the lithium in the cell is contained in the active material within the negative electrode. During discharge, the lithium undergoes transport to the surface of the active material, electrochemical reaction to move from the active material to the electrolyte, transport through the electrolyte to the positive electrode, and reaction and transport to move into the active material of the positive electrode.4,5 Physical models must capture eac...

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Section: Discussionmentioning

confidence: 99%

Multiphase Porous Electrode Theory

Smith

Bazant

2017

J. Electrochem. Soc.

176

232

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“…This discrepancy comes as no surprise as the above σ(t) applies to planar electrodes: this model does not account for the huge surface area and for the ion transport through the porous structure of the supercapacitor electrodes. Simple extensions of the flat electrode setup were discussed, such as spherical and cylindrical electrodes [19,30] and a single cylindrical pore in contact with a reservoir [9]. Several theoretical works focused on the charging dynamics of porous electrodes [31][32][33][34][35][36][37].…”

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confidence: 99%

Blessing and Curse: How a Supercapacitor’s Large Capacitance Causes its Slow Charging

et al. 2020

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The development of novel electrolytes and electrodes for supercapacitors is hindered by a gap of several orders of magnitude between experimentally measured and theoretically predicted charging time scales. Here, we propose an electrode model, containing many parallel stacked electrodes, that explains the slow charging dynamics of supercapacitors. At low applied potentials, the charging behavior of this model is described well by an equivalent circuit model. Conversely, at high potentials, charging dynamics slow down and evolve on two relaxation time scales: a generalized RC time and a diffusion time, which, interestingly, become similar for porous electrodes. The charging behavior of the stack-electrode model presented here helps to understand the charging dynamics of porous electrodes and agrees qualitatively with experimental time scales measured with porous electrodes.

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“…The volume-averaging (homogenization) theory of ion transport in porous electrodes was first developed by Newman and co-workers. Mirzadeh et al 32 explored effects of surface conduction in accelerating the charging dynamics of porous electrodes. Biesheuvel et al 28 extended this work to account for Faradaic reactions at the electrodes' surfaces and overlapping electric double layers in nanoscale pores.…”

Section: Introductionmentioning

confidence: 99%

Capacitive charging and desalination dynamics of a packed-bed reactor

Bau

2015

Phys. Chem. Chem. Phys.

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We study theoretically the charging and desalination dynamics of a packed-bed reactor comprising two percolating granular aggregates that form two porous electrodes. The two porous electrodes are separated with an ion-permeable, electrically insulating spacer, are confined between two long, parallel, current collecting plates, and are saturated with an electrolyte solution. The porous electrodes are ideally polarizable. The electrolyte is binary, and dilute. The electric double layers next to the pore surface are thin. We use volume-averaging (homogenization) theory for porous electrodes and the Gouy-Chapman-Stern model for the electric double layer. Both the cases of finite and infinite aggregate electric conductivities subjected to step changes in the collecting plates' potentials are considered. We determine the potential and concentration distributions and the charging time as functions of space, time, and reactor characteristics. Significantly, we find that the charging time depends only weakly on the solid matrix conductivity as long as the solid matrix conductivity is of comparable magnitude or greater than that of the electrolyte. Furthermore, there is an optimal, finite solid matrix conductivity for which the charging time is minimized.

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Enhanced Charging Kinetics of Porous Electrodes: Surface Conduction as a Short-Circuit Mechanism

Cited by 74 publications

References 36 publications

Multiphase Porous Electrode Theory

Multiphase Porous Electrode Theory

Blessing and Curse: How a Supercapacitor’s Large Capacitance Causes its Slow Charging

Capacitive charging and desalination dynamics of a packed-bed reactor

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