Deformation mechanism maps for alkali metals

Sargent, Philip; Ashby, Michael F.

doi:10.1016/0036-9748(84)90494-0

Cited by 42 publications

(35 citation statements)

References 16 publications

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“…In our MD simulations, we observed dislocation loops climbing inside Li metal, consistent with the findings by Sargent et al. [ 33 ] that the Li metal creep behavior is controlled by dislocation climb. Masias et al.…”

Section: Resultssupporting

confidence: 92%

“…The formation and movements of ½ <111>, <100>, and <110> dislocation loops are observed, confirming the role of creep deformation under the external pressure (Figure S8, Supporting Information). [ 33–35 ] For an incoherent interface with an interfacial adhesion energy of 0.77 J m −2 , an external pressure P of 50 MPa is adequate to fully suppress the pore formation in our simulation (Figure 3b). This level of critical pressure is consistent with the pressure of 35 MPa reported in experiments [ 24 ] that achieve stable cycling of the Li‐garnet LLZO cells, which has an interfacial adhesion energy of 0.67 to 0.98 J m −2 (Table S1, Supporting Information) by DFT calculations.…”

Section: Resultsmentioning

confidence: 86%

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Interfacial Atomistic Mechanisms of Lithium Metal Stripping and Plating in Solid‐State Batteries

et al. 2021

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All‐solid‐state batteries based on a Li metal anode represent a promising next‐generation energy storage system, but are currently limited by low current density and short cycle life. Further research to improve the Li metal anode is impeded by the lack of understanding in its failure mechanisms at lithium–solid interfaces, in particular, the fundamental atomistic processes responsible for interface failure. Here, using large‐scale molecular dynamics simulations, the first atomistic modeling study of lithium stripping and plating on a solid electrolyte is performed by explicitly considering key fundamental atomistic processes and interface atomistic structures. In the simulations, the interface failure initiated with the formation of nano‐sized pores, and how interface structures, lithium diffusion, adhesion energy, and applied pressure affect interface failure during Li cycling are observed. By systematically varying the parameters of solid‐state lithium cells in the simulations, the parameter space of applied pressures and interfacial adhesion energies that inhibit interface failure during cycling are mapped to guide selection of solid‐state cells. This study establishes the atomistic modeling for Li stripping and plating, and predicts optimal solid interfaces and new strategies for the future research and development of solid‐state Li‐metal batteries.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 86%

Interfacial Atomistic Mechanisms of Lithium Metal Stripping and Plating in Solid‐State Batteries

et al. 2021

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“…In addition, Herke, Kirchner, and Schoeck present stress−strain curves of Na in tension at various temperatures, but no strain rate is explicitly stated. 40 Furthermore, the plot units are not clearly defined, but the trend presented appears to show that the critical resolved shear stress was approximately constant between 200 and 300 K. 40 Lastly, Sargent and Ashby 41 conduct creep tests at room temperature but do not present other important mechanical information (such as stress−strain curves).…”

Section: ■ Introductionmentioning

confidence: 99%

Elastic and Plastic Characteristics of Sodium Metal

Fincher

Zhang

Pharr

et al. 2020

ACS Appl. Energy Mater.

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Sodium metal holds promise as an anode material for rechargeable batteries due to its large theoretical charging capacity, low electrochemical potential, earth abundance, and low cost. However, a number of concerns remain that must be addressed prior to practical implementation, particularly Na's propensity to form unstable morphologies during electrochemical deposition. Given the importance of mechanical deformation in this process, unlocking the potential of sodium metal as an anode material requires a thorough understanding of its mechanical properties. To this end, we evaluate the mechanical properties of sodium metal at room temperature through a combination of bulk compression, microhardness, and nanoindentation tests. With regard to elastic properties, nanoindentation testing produced an elastic modulus of 3.9 ± 0.5 GPa. With regard to plastic properties, bulk compression testing revealed the flow stress at 0.08 strain as varying between 102 and 254 kPa at strain rates between 10 −4 and 10 −2 s −1 . Nanoindentation indicated a decrease in hardness from 26.6 to 2.3 MPa at target P ̇/P = 0.05 s −1 as the indentation depth increased from 0.25 to 10 μm, while microhardness testing indicated hardness values between 1.6 and 1.1 MPa at depths varying between 50 and 130 μm. We perform finite element simulations to relate length scales in these measurements (e.g., depth) to physical lengths scales relevant to battery applications. We also found that Na exhibits a marked strain-rate sensitivity, with a strainrate sensitivity exponent of m = 0.14 from nanoindentation and m = 0.20 from bulk compression. Likewise, indentation demonstrated that Na is even more susceptible to creep than is Li metal. Overall, our studies indicate that Na metal is extremely soft, readily creeps, and exhibits pronounced size effects. We discuss the implications of these properties relative to other candidate anode materials of rechargeable batteries. Most notably, Na's greater propensity to creep than Li, in turn, has implications for charging rate capability in solid-state batteries.

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“…For lithium, room temperature is approximately 0.65⋅Tm (melting temperature in K). Typical deformation mechanism maps of metals [30] show that at such high homologous temperatures, deformation is not solely based on dislocation glide. In addition, three diffusive processes are active already at lower stresses: These are (i) GB diffusion (in bulk materials known as Coble creep) and (ii) dislocation creep (climb).…”

Section: Discussionmentioning

confidence: 99%

The Growth Mechanism of Lithium Dendrites and its Coupling to Mechanical Stress

Becherer

Kramer

Mönig

2021

Preprint

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Operando high-resolution light microscopy with extended depth of field is used to observe large regions of an electrode during electrodeposition of lithium. The analysis of the morphology of the evolving deposit reveals that besides electrochemistry, mechanics and crystalline defects play a major role in the growth mechanism. Based on the findings, a growth mechanism is proposed that involves the diffusion of lithium atoms from the lithium surface into grain boundaries and the insertion into crystalline defects in the metal. Crystalline defects are a result of plastic deformation and hence mechanical stimulation augments the insertion of lithium.

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Deformation mechanism maps for alkali metals

Cited by 42 publications

References 16 publications

Interfacial Atomistic Mechanisms of Lithium Metal Stripping and Plating in Solid‐State Batteries

Interfacial Atomistic Mechanisms of Lithium Metal Stripping and Plating in Solid‐State Batteries

Elastic and Plastic Characteristics of Sodium Metal

The Growth Mechanism of Lithium Dendrites and its Coupling to Mechanical Stress

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