Symposium EN06—Solid-State Batteries—From Electro-Chemo Mechanics to Devices

Munekazu Motoyama, Kyushu University

The Influence of Temperature on Li Plating/Stripping at Metal/Oxide Solid Electrolyte Interfaces

Written by Xinzi He

Oxide solid electrolytes (Li-ion conductors) are non-flammable and have no risk of releasing toxic gas. Munekazu Motoyama started the talk with two mechanisms of short-circuiting: the isolated void formation on the interface and hydrostatic pressure of Li at the flaw. Prof. Motoyama then introduced his systematical study on how different factors, including temperature, area, pressure, and interface wetting, would influence the critical current density (CCD) for short-circuiting using Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte. The CCD was found to increase with the increase of the temperature and the increase of the LLZT thickness. Moreover, the activation energies of the CCDs were also discussed. An important founding is that the improvement of the wettability between Li and LLZT does not help increase the CCD. At the end, Prof. Motoyama and the audience also discussed the experiment setup on the electrode constructions.


Symposium SF07—In Situ Material Performance and Dynamic Structure Characterization Under Coupled Extremes

Daniel Kiener, Montanuniversity Leoben

Size Affected Toughening and Strain Rate Sensitivity of Silicon

Written by Henry Quansah Afful

It is a well-known phenomenon that nanostructured materials are much stronger than their bulk counterparts but this usually limits their fracture toughness. Can we emit dislocations that will blunt the crack tip and thereby increase the fracture toughness in these nanostructured materials? Kiener demonstrates this phenomenon in nanostructured silicon (Si) using in situ transmission electron microscope (TEM) at room temperature. Kiener created a notch in the material along some crystallographic orientation to act as a stress concentration site. TEM images reveal the nucleation of dislocations from the crack tip in <250 nm-thick Si which blunted the crack tip and increased the fracture toughness by a factor of 3 from what is observed in bulk Si. Dark field mode in TEM revealed the absence of these dislocations prior to the bending test proving that these were formed during the test. The presence of this intrinsic toughening mechanism in Si makes it more damage-tolerant and useful for microelectromechanical devices.


Symposium EN06—Solid-State Batteries—From Electro-Chemo Mechanics to Devices

Peter Bruce, University of Oxford

Factors Influencing the Critical Current in Lithium Anode Ceramic Electrolyte Solid-State Batteries

Written by Xinzi He

The critical current density (CCD) for solid-state batteries pairing with a lithium anode is always discussed in the scenario of dendrite penetration. Peter Bruce started the talk by pointing out that the void formation on the lithium stripping side can be another critical reason that makes the CCD smaller than the dendrite-penetration-controlled one. Moreover, using x-ray computed tomography, the location where dendritic cracks initiate and propagate were revealed. The cracks were found driven by Li at the back of the crack, not the tip. An important lesson found is lower stacking pressure can be more favorable to achieving higher CCD without crack propagation. In the end, together with the session chair Prof. Matt McDowell (Georgia Institute of Technology) and Prof. Xin Li (Harvard University), Prof. Bruce discussed how the cell structures design—with and without lateral restriction—may influence these crack phenomena.


Symposium SF09—High Entropy Materials II—From Fundamentals to Potential Applications

Dmitri Louzguine-Luzgin, Mathematics for Advanced Materials-OIL, National Institute of Advanced Industrial Science and Technology

High Entropy Approach Starting from a Corner of the Phase Diagram in Designing High Strength Fe–Based Alloys

Written by Henry Quansah Afful

Solid solutions can be easily formed by following Hume-Rothery rules and this also applies to high entropy alloys (HEA). In essence, the atomic radii of the solute and solvent must not be different by more than 15% and crystal structures must be similar. The low yield strength of HEAs has been attributed to the disorder in these compositions and introducing some amount of ordering (small or medium range) can enhance the strength. Louzguine-Luzgin tested some HEAs having the Fe–Mn–Al–C base system, and by starting from the corner of the phase diagram, added varying amounts by mass of Co and Ni to replace a portion of Fe and Mn. The compositions tested had both face centered cubic (FCC) and body centered cubic (BCC) phases but the BCC phase was ordered. The Fe–Mn–Co–Al–C alloys formed had high tensile plasticity of 10% and high yield and ultimate strength values of up to 1590 MPa and 1650 MPa, respectively. Louzguine-Luzgin attributed the high strength values to solid solution hardening and deformation strengthening from the thermomechanical treatments.


Symposium EN05—Emerging Materials for Electrochemical Energy Storage Devices—Degradation and Failure Characterization—From Composition, Structure and Interfaces to Deployed Systems

Yazhou Zhou, Stevens Institute of Technology

Suppressing Volume Change in the Li Metal Anode via Three-Dimensional Current Collector Construction for Anode-Free Batteries

Written by Xinzi He

Yazhou Zhou started the talk with the introduction of the challenges of poor Coulombic efficiency and substantial volume change toward the practical application of anode-free batteries. Yazhou utilized a novel technique of electro-writing to fabricate a three-dimensional (3D) current collector. The complex 3D polymer structures consist of polymer microfibers with a uniform diameter of ~20 µm, which enables the stable formation of uniform solid-electrolyte interphases (SEI) and allows extended (>150 times) cycle life at 1 mA cm-2. In the end, Yazhou emphasized the great opportunities this unique method could provide for scalable and safe anode-free batteries.


Symposium EN06—Solid-State Batteries—From Electro-Chemo Mechanics to Devices

Tuncay Koç, College de France

In the Search for the Best Solid Electrolyte-Layered Oxide Pairing for Assembling Practical All-Solid-State Batteries

Written by Xinzi He

Tuncay Koç started the talk with a discussion on the main barriers to developing all-solid-state batteries (ASSB). The compatibility was studies of three inorganic solid-state electrolytes (SSEs) (β-Li3PS4, Li6PS5Cl, and Li3InCl6) as part of the cathode composite paired with coated-layered oxide (LiNi0.6Mn0.2Co0.2O2—NMC622). Systematically comparison was made with both solvent-assisted and solvent-free synthesized SSEs for their structures, morphologies, and electronic-ionic conductivities. Some main findings include the chemical incompatibility of Li3InCl6 toward the two sulfide-based electrolytes (β-Li3PS4 or Li6PS5Cl), the critical role of the electron conductor in the cathode composite, and the effectiveness of a protecting coating layer on NMC622. Stable cycling of 380 cycles with ~8.4% fading was achieved for a 3.2 mAh cm-2‑loaded NMC622 cell under room temperature.


Symposium SF13—From Actuators and Energy Harvesting Storage Systems to Living Machines

Yue Liu, Helmholt-Zentrum Hereon

Actuating Micro-Bowls with a Temperature-Memory

Written by Henry Quansah Afful

In nature, several organisms change their shape to adjust to environmental conditions and shape memory materials including shape memory polymers (SMP) attempt to mimic this. Typically, the material is strained in a process known as programming and it recovers its original shape when some stimulus such as heat is applied. However, programming micro/nano SMPs is extremely challenging. Liu demonstrates how the atomic force microscope can help program these materials as well as characterize the behavior in situ. The shape memory effect was explored to ensure the sequential release of sub-micron particles. These particles were initially programmed by compression followed by nanoindentation into a bowl-shaped substrate (micro-bowl) at different temperatures. When the micro-bowl was heated to the same programming temperature, the trapped particles were released with diameters dependent on the size of the cavity created from nanoindentation. Liu demonstrated that the depth of the cavity and geometry of the micro-bowl also respond to temperature changes. This concept can be explored for potential on-demand carriers in drug delivery for instance.

 


Symposium EN05—Emerging Materials for Electrochemical Energy Storage Devices—Degradation and Failure Characterization—From Composition, Structure and Interfaces to Deployed Systems

Jelena Popović-Neuber, Max-Planck-Institute for Solid State Research

Insights in Solid Electrolyte Interphase Evolution on Alkali Metals with Liquid and Solid Electrolytes  

Written by Xinzi He

Jelena Popović-Neuber systematically studied the solid electrolyte interphase (SEI) growth and associated ion transport on Li and Na metal in contact with glyme and carbonate-based electrolytes under galvanostatic and OCV conditions by electrochemical impedance spectroscopy (EIS), ex situ x-ray photoelectron spectroscopy, and focused ion beam scanning electron microscopy. Moreover, the existence of SEI on K electrode in contact with glyme-based electrode was discussed. Finally, the artificial SEI was mentioned and Popović-Neuber pointed out that density is still a major problem that needs further improvements. At the Q&A session, Popović-Neuber and the audience also discussed the interpretation of the EIS data, and the characteristic frequency was pointed out as a main factor to be paid attention.


Symposium SF09—High Entropy Materials II—From Fundamentals to Potential Applications

Haruyuki Inui, Kyoto University

Plastic Deformation of Single Crystals of Equiatomic and Non-Equiatomic High- and Medium Entropy Alloys of the Cr-Mn-Fe-Co-Ni and Its Sub-Systems

Written by Henry Quansah Afful

Some face centered cubic (FCC) high entropy alloys (HEA) possess high strength and ductility at low temperatures in addition to high fracture toughness. Haruyuki Inui points out that single crystal mechanical data is useful in tracking the correlations between various parameters and these mechanical properties. He introduced one such parameter—the Mean Square Atomic Displacement (MASD)—as a useful predictor of the mechanical behavior in these HEAs. Inui demonstrated that the MSAD is independent of the number of elements in HEAs but rather depends on the elements constituting the alloy. Part of the reason is that the MSAD has a strong correlation with increasing atomic number. Also, MSAD values can be used to predict the strength of these HEAs because of a strong correlation between these but there has to be further modification to ensure it predicts the right order of increase in strength. The critical resolved shear stress in these alloys tested had both temperature and strain-rate dependence similar to observations in typical FCC solid solutions. CrCoNi was the strongest of the alloys.


Symposium SF13—From Actuators and Energy Harvesting Storage Systems to Living Machines

Sung-Hoon Ahn, Seoul National University

Material-Form-Scale Effects of Shape Memory Alloy (SMA) Actuators

Written by Henry Quansah Afful

Several engineering applications—aerospace, wearables, biomedical devices—exist for flexible, stretchable and “human muscle-like” actuators. However, it is very difficult to obtain these characteristics in some materials. Ahn addressed the role that the form, scale, and composition of materials used play in producing such multi-functional actuators with interesting behaviors. He showed that different material compositions (binary, ternary, or multinary) could have different actuation strains and phase transformation/working temperature ranges. Also, the form of the material designed affects its modes of actuation—contraction, bending, twisting and rotation—and a soft smart composite designed in Ahn’s laboratory demonstrates this. He also addressed the misconception that Shape Memory Alloys (SMA) have slower actuation by demonstrating that fabricating very thin SMA wires increases the switching frequency to several hertz. Furthermore, at such scales, the strain recovery can be in response to a remote laser beam instead of direct heat application. These ideas of form, scale, and type of material can all be merged to inform SMA design and enlarge their application space.