A Li-ion battery (LIB) anode particle made of graphite is studied to analyze the role of stress concentrations due to voids on the electrochemical behavior. Numerical experiments are carried out on a cylindrical particle of radius (R) with a central hole of radius (r). First, a charge-discharge (CD) voltammetry experiment is simulated; following which the particle is first discharged and then charged (DC). These experiments are conducted for various (r/R) ratios. The results show that for DC case, the effects of stresses on the electrochemical response decreases with the increase in (r/R) ratio, while for the CD case the effects may increase or decrease depending on (r/R) ratio and particle size. Specifically, for particle size less than 5µm the effect of stress reduces with increase in (r/R) ratio and for particle sizes between 5 and 25µm the effect of stress may increase or decrease depending on (r/R) ratio. © The Electrochemical Society

Narasimhan Swaminathan

Department of Mechanical Engineering

Mohammad Ayub Ansari

Pramod Yallappa Kumbhar

Electric discharges

Electrodes

particle size

Stress concentration

Charge-discharge

Computational studies

CYLINDRICAL PARTICLES

EFFECT OF STRESS

Electrochemical behaviors

ELECTROCHEMICAL RESPONSE

LI-ION BATTERY ELECTRODES

Numerical experiments

Lithium-ion batteries

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IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

ECS Transactions

Several numerical voltammetry simulations are used to evaluate the role of stress concentrations on the electrochemical response of an anode particle with geometric discontinuities. The effect of two-way stress-diffusion interaction, on the magnitudes of the mechanical stresses induced, is also estimated. Effects of stresses on electrochemical response increases (decreases) with the sweep rate when the particle was first discharged (charged). Stress concentrations are analyzed for several particle and hole sizes, and hole locations. It was found that the dependence of electrochemical response on stress is influenced more by the size of the hole rather than its position. When two-way interactions between stresses and diffusion were considered, the peak stresses induced were found to be 0.3 to 0.5 times the value induced when the influence of stress on diffusion was neglected. Overall, the study shows that stress-concentrations significantly affects the electrochemical behavior of a particle. Further, numerical modeling should include a two-way interaction between stress and diffusion so as to not overpredict stresses in an electrode particle. © The Author(s) 2019.

Journal of the Electrochemical Society

Role of stress concentrations on the electrochemical response of a li-ion battery anode particle

A cylindrical composite anode with a graphite shell (radius Rs) and a silicon core (radius Rc) is used to explain the physics involved in the interactions between mechanics, electrochemistry and particle geometry. Potentiostatic and potentiodynamic simulations are used to illustrate the role of elastic driving forces on the concentration, stress distributions and the current-voltage relations. Potentiostatic simulations show that, concentration and stress distributions are altered by the intercalation stresses. Potentiodynamic simulations are conducted by either charging and then discharging or, discharge followed by charging the particle. Voltammograms show that the presence of intercalation stresses alters the electrochemical response significantly. The magnitude of this alteration depends on particle size, sweep rate and on whether the particle is charged or discharged first. The difference between peak anodic current density (Δimax) in the voltammograms obtained from including stresses in the formulation and that from excluding it, is used to quantify stress-electrochemistry interactions. The parameter Δimax is mapped for various values of Rc and [Formula presented], for a given sweep rate, suggesting a design space from which the core and the shell geometries with an acceptable level of stress-electrochemistry interactions can be chosen. Higher sweep rates may enhance Δimax depending on whether the particle is charged or discharged first. © 2019 Elsevier B.V.

Solid State Ionics

Stress-electrochemistry interactions in a composite electrode for Li-ion batteries

A computational study on the effect of stress concentrations on elasticity-electrochemistry interactions in Li-ion battery electrode particle

Journal	ECS Transactions
Publisher	Electrochemical Society Inc.
ISSN	19386737
Open Access	No