Symposium SB10: New E-Textile Materials and Devices for Wearable Electronics

Felice Torrisi, Imperial College London

Two-Dimensional Field-Effect Heterostructures for Wearable and Textile Electronics

Written by Henry Quansah Afful

Wearable electronics are required to be, amongst other things, highly stretchable, biocompatible, and washable. Considering all these requirements, textiles are the most optimal substrates being used for these electronics. Employing two-dimensional (2D) material inks such as graphene and other layered materials for the electronic circuit design reduces the cost of production. These 2D materials show a lot of promise in tunability and multifunctionality. Using microfluidic exfoliation, graphene platelets can be obtained from graphite and the aspect ratio of these platelets can be tuned to have corresponding changes in electrical conductivity. In addition, bandgaps of the wearable electronics can be tuned by designing layered materials. Felice Torrisi demonstrated an inkjet printing approach for printing graphene oxide on a cotton substrate. The surface of the cotton was modified with cations to develop a positive charge whereas that of the graphene oxide ink was negatively charged. This was found to improve the adhesion of the ink on the cotton substrate considerably, resulting in stable electronic properties over 20 wash cycles. In addition, Torrisi showed how cotton wool could be mixed with graphene ink to produce graphene-cotton fiber via a wet-spinning approach. This significantly improved the flexibility of graphene.

Symposium EN03: Beyond Li-Ion Batteries—Low Cost Alternatives Based on Other Chemistries

Daniel Sykes, University College London

A Computational Study of the Intrinsic Defect Chemistry of Promising Sodium-Ion Cathode Material Na₂FePO₄F

Written by Senam Tamakloe

In the past few years, sodium-ion batteries (SIBs) have attracted significant attention due to their virtually unlimited resources. The commercial market has a wide variety of sodium-containing resources making electrode preparation scalable. The exploration and development of sodium-based electrodes for SIBs is currently a prevalent research topic. In particular, the Na₂FePO₄F cathode serves as an attractive candidate for SIBs, owing to its more stable cycling performance and high discharge voltage. Density functional theory (DFT) is a modern quantum mechanical approach that has widely gained acceptance from the materials science community as a useful tool for explaining the chemical potential stability and the intrinsic vacancy defects, for example. The ability to study intrinsic defects at the level of atoms and molecules is essential for the advancement in energy storage. To characterize the electronic structures of this fluoride-phosphate structure and explain electron interactions and charge localization, all calculations are performed using the hybrid HSE06 (Heyd-Scuseria-Ernzerhof) functional. By employing DFT, Daniel Sykes offers new insights in understanding the doping effect for potential improvements in the sodium-ion diffusivity and electronic properties for SIB cathodes.

Symposium EQ10: Phase-Change Materials for Brain-Like Computing and Memory Applications

Tiantian Li, Xi'an University of Posts and Telecommunications

Low-Entropy Phase Transition in Indium Selenide for Integrated Photonic Memory

Written by Senam Tamakloe

Tiantian Li leads us through the quest for improved optical phase change materials (O-PCM). These materials serve as an attractive candidate in memory and logic units for optical signal processing and storage. Some applications include nonvolatile optical memory, nonvolatile photonic switch, neuromorphic photonics, reconfigurable photonics devices, and recently optical neurosynaptic networks capable of supervised and unsupervised learning. Li and her colleagues have investigated the two-layered crystalline states of indium (iii) selenide materials for optical memory. Key achievements noted from this work include the demonstration of nonvolatile switching of the hybrid In₂Se₃-Si resonator driven by a single nanosecond pulse. Li’s materials are a vast improvement compared to amorphous-crystallization transitions. Experimental and computational data were collected by differential scanning calorimetry, x-ray diffraction, and density functional theory. These results elucidate the finding of low entropic structural transitions in the layered In₂Se₃ structures for producing the energy efficiency and speed constraints of memristive circuits and devices.

Symposium EN03: Beyond Li-Ion Batteries—Low Cost Alternatives Based on Other Chemistries

Yinan Liu, Colorado School of Mines

Lithium Insertion into Nearly Empty Type II Silicon Clathrate

Written by Senam Tamakloe

A primary initiative for current energy storage research is discovering new anode materials for Li-ion batteries. An emerging class of silicon-based cage compounds known as clathrates can serve as promising candidates. An empirical investigation of type II silicon clathrate (e.g., Li_xSi₁₃₆) as a potential anode material for electrochemical application is showcased. This hybrid Si-Li clathrate contains lithium atoms situated in the interstitial gaps while silicon atoms collectively form as a host structure. The exploration of the initial stage of diffusion was studied and confirmed using time-of-flight secondary ion mass spectrometry), x-ray diffraction along with Raman spectroscopy that offered useful insights into the Li diffision into the anti-bonding state of Si clathrate causing a reduced structural stability. Interestingly, the behavior of Li in the clathrate cages was studied using electron paramagnetic resonance) showing that unpaired electrons and magnetic nuclei causes hyperfine interactions while Yinan Liu later noted that the Li atoms doubled its occupancy in the Si clathrate cage after diffusion. The findings of this work offer a renewed understanding on occupying clathrate cages, opening the door for the possibility of exploring a variety of different interstitial guest atoms.

Symposium DS01: Modern Materials Thermodynamics

Axel van de Walle, Brown University

Computational Tools for the Generation and Visualization of High-Dimensional Phase Diagrams

Written by Senam Tamakloe

Large, high-dimensional data sets comprising of chemical structures and related characteristics are being produced in the sciences at an increasingly high rate. There is, however, a lack of methods available to show such data while maintaining both global and local characteristics with a reasonable degree of detail and computational cost to permit further examination and interpretation. In this session, the presenter introduces a new data visualization technique as a potential solution for this issue based on the special quasirandom structure (SQS). Researchers provide a variety of computer programs that make it possible to build high-dimensional CALPHAD (calculation of phase diagram) databases from first-principles computations by adding “short-range-order corrections, rigorous handling mechanical instabilities, and interactive visualization of high-dimensional phase diagram.” Ultimately this proposed visualization tool allows for interactive three-dimensional cross-section exploration of higher-dimensional phase diagrams.

Symposium SB10: New E-Textile Materials and Devices for Wearable Electronics

Stephen Beeby, University of Southampton

E-Textiles Power Modules—Removing the Reliance on Conventional Batteries

Written by Henry Quansah Afful

Electronic textiles (e-textiles) is a rapidly growing field of research with a large innovation space in multifunctionality. The electronic circuits and systems in the textiles are required to be invisible to the user to avoid reducing the aesthetic appeal of the clothing. However, the batteries used are so bulky that they end up being visible to users and defeating the purpose of having concealed wearables. There has therefore been the drive away from these traditional batteries into alternative textile-based energy storage devices such as supercapacitors. Piezoelectric materials can be used to convert kinetic energy associated with straining the textile into electrical energy that can be stored. Stephen Beeby showed that ferroelectric materials are able to store more energy in multiple stress states with much increased sensitivity to strains than piezoelectric materials. He also gave an overview of other power harvesting technologies including triboelectric (rubbing textiles together), photovoltaic and wireless power harvesting (capturing electromagnetic energy). “The choice of energy harvesting technique is dependent on the application and the energy sources available,” Beeby says. He also showed that a porous polymer membrane can be employed to convert any textile into an e-textile.

Symposium CH03: Advanced Characterizations of Heterogeneities in Electrochemical Energy Storage Materials

Chongmin Wang, Pacific Northwest National Laboratory

Cryo and In Situ Electron Microscopy Diagnosis Guided Design of Materials for Rechargeable Battery

Written by Aashutosh Mistry

The complexity of materials in batteries, both chemical and geometrical, makes it nearly impossible to probe using a single technique. Hence, Chongmin Wang and his colleagues use a combination of techniques that complement each other to construct a more descriptive picture of the interactions underlying a new battery type. Wang discusses two interesting examples of how their approach pans out in examining new battery types—one with lithium and another with silicon as the negative electrodes. For the lithium electrodes, while we know mechanical effects do contribute to their growth, we do not sufficiently understand the mechanical behavior of lithium for the range of geometries and conditions experienced in batteries. The researchers cleverly used the tip of the atomic force microscope as a mechanical cantilever to probe the mechanical behavior of lithium under different conditions. For example, the research group found that even with the same materials, the mechanical behavior of lithium is strongly dependent on the morphology of the deposited lithium. This is particularly intriguing and suggests that maybe one mechanical strategy is not sufficient to control its growth given the underlying geometrical inhomogeneities and morphology-dependent mechanical behavior.

Symposium EN03: Beyond Li-Ion Batteries—Low Cost Alternatives Based on Other Chemistries

Anton Van der Ven, University of California, Santa Barbara

Comparisons of Li, Na, K and Mg-Ion Insertion into Layered and Spinel Intercalation Compounds

Written by Aashutosh Mistry

Developing a new battery is an arduous process, and we preferably wish to make surgical modifications without having to reinvent everything from scratch for a new battery. One such surgical modification is to use the same intercalation materials but replace the working ion, for example, swapping lithium for the sodium ion. Such an approach allows us to lean on the decades-long development efforts in lithium-ion batteries. However, even such a seemingly minor change alters the behavior of the same materials now intercalating a different ion, and we still have to understand the material behavior in this new context. Anton Van der Ven and his research group have been making such connections. Using first-principles statistical mechanical theories, they have carefully examined how thermodynamics and kinetics of ion intercalation change across lithium, sodium, and magnesium ions. Such fundamental studies are useful in elucidating the design space available for building next-generation batteries.

Symposium DS03: Artificial Intelligence Approaches for Energy Materials

Alejandro Franco, Universite de Picardie Jules Verne

Multi-Objective Optimization of Lithium Ion Battery Manufacturing by Using Machine Learning Coupled to Physics-Based Process Modeling

Written by Aashutosh Mistry

Did you know that during battery manufacturing, nearly 5% of batteries are scrap? An aspirational goal is to be able to accurately control the battery manufacturing process using models for battery processing. Alejandro Franco and his group have been on this mission for a few years now. In this talk, Franco discussed the array of physics-based battery models they have been developing in recent years. Specifically, he showed five models for describing the battery manufacturing at different lengthscales: (i) molecular dynamics describing the electrode slurry to tune the corresponding interparticle forces; (ii) coarse-grained model for slurry evaporation and resultant distribution of materials phases in the porous electrode; (iii) discrete element model to describe calendaring of such a porous electrode and predict changes in the distribution of materials; (iv) lattice Boltzmann model to model subsequent infiltration of electrolyte in this porous electrode; and (v) finite element method solution to describe the electrochemical performance of such a porous electrode. While each of these represents a detailed calculation, they are not suited for on-the-fly control of battery manufacturing. To bridge that gap, Franco and his team train data-driven models based on these detailed physics-based calculations. It would be interesting to see how these models help transform battery manufacturing practices.

Symposium EN05: Solid-State Batteries—Life, Safety and Scalability

Anton Resing, Boston University

Solid-State Electrodes and Electrolytes with Tunable and Low-Tortuosity Micro-Architected Structures from Nonequilibrium Processing

Written by Aashutosh Mistry

As we aspire to transition to solid-electrolyte-based batteries, a key challenge is to tune the relative arrangement of different materials phases for efficient transport processes. Specifically, we have to ensure appropriate contact between energy-storing active particles and adjoining solid-electrolyte domains, efficient ion transport pathways through the solid-electrolyte, and electron conduction pathways through the carbon networks. While liquid-electrolyte-based batteries have been optimized for these aspects over the years, we still have to figure these out for solid-electrolyte-based batteries. A simple but effective solution could be to produce electrodes and solid-electrolyte structures such that the two interlace together. Anton Resing and his colleagues have developed an organo-gel-based processing scheme to fabricate such structures. Subsequently, the solid-electrolyte and electrode structures are interlaced and sintered with polyethylene glycol (that acts as a glue to ensure a conformal contact at the interface). The research team is currently investigating the electrochemical performance of such solid-electrolyte-based batteries to assess the effectiveness of this fabrication strategy.