Deformation and stress in electrode materials for Li-ion batteries

Mukhopadhyay, Amartya; Sheldon, Brian W.

doi:10.1016/j.pmatsci.2014.02.001

Cited by 567 publications

(491 citation statements)

References 210 publications

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“…Potentiostatic conditions.-These conditions involve the specification of the concentration on the electrode outer surface (r = R) for all t. We use, c(R, t) = c m [18] J | r =0 = 0 [19] Since Eq. 9 is a transient problem initial conditions must also be specified.…”

Section: Boundary Conditionsmentioning

confidence: 99%

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Elasticity and Size Effects on the Electrochemical Response of a Graphite, Li-Ion Battery Electrode Particle

Swaminathan

Balakrishnan

George

2015

J. Electrochem. Soc.

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The interactions between electrochemical response, elasticity and particle size of a cylindrical, Li-ion battery, graphite electrode particle is studied. First, a potentiostatic study is conducted to demonstrate the role of higher-order stress terms of the chemical potential on the distributions of flux, stresses and concentrations. Then, two cyclic voltammetry experiments are simulated to study the effects of elasticity on the voltammograms. In the first, the electrode is discharged and then charged, while the second, involves the opposite. Effects of elasticity on the anodic (discharging) portion of the voltammograms are more pronounced in the first experiment when compared to the second. The effects of the elasticity also vary with particle size in different ways for the two experiments. In the first, the effects of stresses on the anodic current increases with particle size and then reaches a plateau at around 30 μm. In the second, a maximum effect of elasticity is seen for a particle size of 5 μm. Our study shows that, stresses induced due to diffusion of Li atoms not only affect the mechanical integrity of the electrode particle, but also change the way the particle responds to an applied external potential, thereby affecting its electrochemical response. Interactions of chemistry and mechanics in Li ion battery (LIB) electrodes has gained a lot of interest recently.1-16 Chemical expansions of varying degrees have been observed and quantified in some of the existing electrode materials (graphite) and in prospective electrode materials like Sn, Al and Si.17 The intercalation and de-intercalation of Li ions into and out of the electrode causes local chemical strains in the latter. During the functioning of the LIB, gradients in Li concentration that arise lead to non-uniform strains throughout the electrode particle. When these chemically induced strains are not accommodated by appropriate deformation of the solid, stresses are induced which can result in local failure and degradation in the performance of the electrode and hence the battery. Local changes in Li concentration also alter the mechanical properties of the electrodes. For a recent, detailed review on the effects of stress-diffusion interactions in Li-ion battery materials and the various experimental techniques involved in their quantification please see Ref. 18. The effects of Li diffusion induced stresses (DIS) are well understood and modeled through the framework of thermoelasticity. The changes in concentration are treated in a manner analogous to changes in temperature, and hence chemical strains are introduced into the constitutive equations of elasticity in the form of eigen strains. The elastic equilibrium equations are then solved in order to predict the stresses, displacement and strains. Stresses also affect the thermodynamics of the electrodes. For example, stresses alter the electrochemical potential of Si by 50mV or more.19 Another associated effect is stress induced diffusion (SID), where the elastic stresses developed in the elec...

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Section: Boundary Conditionsmentioning

confidence: 99%

“…For a recent, detailed review on the effects of stress-diffusion interactions in Li-ion battery materials and the various experimental techniques involved in their quantification please see Ref. 18. The effects of Li diffusion induced stresses (DIS) are well understood and modeled through the framework of thermoelasticity.…”

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confidence: 99%

Elasticity and Size Effects on the Electrochemical Response of a Graphite, Li-Ion Battery Electrode Particle

Swaminathan

Balakrishnan

George

2015

J. Electrochem. Soc.

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“…On the other hand, it is accepted in general that the physical and electrochemical properties of LiMn2O4 are determined by such factors as particle size, lattice parameter, stoichiometry, average Mn valence, surface morphology, and homogeneity [1][2][3][4][5]. In practice, these factors are closely related to the synthesis method and condition, such as starting material, content of lithium, heating temperature, holding time, and cooling rate [6][7][8][9][10][11][12].…”

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Synthesis and Characterization of Stoichiometric Spinel-LiMn<sub>2</sub>O<sub>4</sub>

et al. 2017

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In this study, spinel LiMn2O4 powder was synthesized from LiOH.H2O and MnOx by conventional and mechanical alloying (MA) methods, followed by heat treatment at 800 °C in O2 for four hours with cooling to room temperature in the furnace at 60 °C/h. It is found that both samples do not show phase transition in low temperature, and this occurred for different reasons. In the MA sample, the presence of Fe as contamination increased the Mn valence and hindered the occurrence of phase transition. The conventional sample does not show phase transition at low temperature due to stoichiometric content, without any contamination. In general, the absence of phase transition occurred due to synthesis condition employed in this study.

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“…6 A promising possibility to prevent pulverization is to reduce the structure size of the electrode material and to introduce high porosity. 7,8 High porosity reduces concentration gradients by reducing the diffusion lengths and it weakens the constraints by offering free space in the vicinity of the electrode.…”

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confidence: 99%

“…by the current collector) or the lithium is inhomogeneously distributed in the host material, the change in volume is accompanied by stresses. 6 Possible consequences are the evolution of cracks in the material which can lead to pulverization of the electrode material and consequently loss of capacity. 6 A promising possibility to prevent pulverization is to reduce the structure size of the electrode material and to introduce high porosity.…”

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confidence: 99%

The Electro-Chemo-Mechanical Coupling in Lithium Alloy Electrodes and Its Origins

Kitzler

Maawad

Többens

et al. 2015

J. Electrochem. Soc.

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A method to identify and separate the influence of changes in the surface stress from the bulk stress in a model lithium-ion battery electrode during electrochemical cycling was developed. The strategy for this separation is based on the different influence of surface and bulk stresses on the coupling between electrode potential and mechanical strain as measured by dynamic electro-chemo-mechanical analysis and the coupling between the transferred electric charge and the elastic strain as determined by wide angle X-ray scattering. Using both methods, it was possible to uncover the behavior of an apparent surface stress evoked by the bulk stress due to grain boundary alloying of lithium in a gold film. Additionally, the analysis allowed for a determination of a range in surface stress due to underpotential deposition of one monolayer of lithium as the interval between −3.1 to Lithium-ion batteries are widely used, though the amount of electric charge they can store is still far away from their theoretical capacity.1,2 In order to increase the capacity of lithium-ion battery anodes, the commonly used graphite needs to be replaced. A very promising alternative are materials which can form alloys with lithium. 3,4 There are several possible candidates. 5 Among the most important ones are silicon, germanium, tin, aluminum, and antimony. The theoretical volumetric lithium storage capacity of these materials is several times higher than that of the currently used anodes. In case of silicon, more than ten times that of graphite relative to the weight of the host material. This storage capability of the afore mentioned materials is based on their ability to store more than one, in case of silicon, germanium, and tin up to 4.4 lithium atoms per host atom. The obvious drawback of these materials is the huge volume change during lithium loading which can easily exceed 100%.If the electrode material is constrained (e.g. by the current collector) or the lithium is inhomogeneously distributed in the host material, the change in volume is accompanied by stresses.6 Possible consequences are the evolution of cracks in the material which can lead to pulverization of the electrode material and consequently loss of capacity. 6 A promising possibility to prevent pulverization is to reduce the structure size of the electrode material and to introduce high porosity. 7,8 High porosity reduces concentration gradients by reducing the diffusion lengths and it weakens the constraints by offering free space in the vicinity of the electrode. However, this strategy also increases the surface to volume ratio, and therefore drastically increases the impact of the surface stress, which can have an important impact on the stability of the electrode material.9 Additionally, the stress interacts with the chemical potential via the strain energy. 10 Therefore, the equilibrium lithium concentration is a function of the stress state which, in general, is inhomogeneous within the electrode material. Recent simulations performed by Gau and Zhou 11 indicat...

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Deformation and stress in electrode materials for Li-ion batteries

Cited by 567 publications

References 210 publications

Elasticity and Size Effects on the Electrochemical Response of a Graphite, Li-Ion Battery Electrode Particle

Elasticity and Size Effects on the Electrochemical Response of a Graphite, Li-Ion Battery Electrode Particle

Synthesis and Characterization of Stoichiometric Spinel-LiMn<sub>2</sub>O<sub>4</sub>

The Electro-Chemo-Mechanical Coupling in Lithium Alloy Electrodes and Its Origins

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