bluuebunny/crossref_metadata_2025 huggingface dataset:
Advances in Reliability of Conducting Polymers and Conducting Polymer Based Capacitors in High Humidity Environment
Authors: Chacko Antony P , Jin Yang , Shi Yaru , Bunha Ajaykumar , Chen Qingping , Lessner Philip
Published: February 2020

Polymer tantalum capacitors are emerging as an excellent choice for circuit designs that requires stable capacitance, long life, high reliability and smaller size. Conductivity stability of PEDOT materials as well as polymer tantalum capacitors with PEDOT cathodes were investigated in this study for stability under high humidity high temperature conditions. PEDOT films and cathodes formed from insitu polymerization (PEDOT: TOS) and pre-polymerized dispersion (PEDOT: PSSA) were compared under 85°C/85%RH environment. Electrical measurements along with Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), UV Spectroscopy, Thermo-mechanical Analysis (TMA) and Thermal Imaging were used to characterize the samples. Resistance of the films formed from insitu polymerization increased significantly on exposure to 85C/85%RH compared to the films formed from pre-polymerized dispersion. However, the trend was reversed in the capacitors where cathodes formed by insitu polymerization was more stable than the cathodes from PEDOT: PSSA. Our studies suggest that delamination caused by the thermomechanical and voltage induced stress generated in these capacitors is primarily responsible for resistance degradation in polymer capacitors. These new insights led to the development of a new generation of PEDOT:PSSA polymer systems which significantly enhanced the reliability of polymer capacitors in harsh environments.
Highly Scalable Fabrication of Planar-Type Thermally Chargeable Supercapacitor Based on Graphene Oxide
Authors: Kim Suk Lae , Hsu Jui-Hung , Yu Choongho
Published: February 2020

The development of efficient and sustainable energy sources has become important to power the rapidly growing portable electronic devices. Newly developed thermally chargeable supercapacitors that can be charged by heat energy including human body heat have great potential to become standalone power sources for wearable electronics. However, the complex fabrication process of electrodes and devices limits the cost-effectiveness and scalability for widespread application. Here we demonstrate highly scalable fabrication of planar-type thermally chargeable supercapacitor (pTCSC) by using one-step laser printing method on graphene oxide films with a general DVD burner. We utilized the Soret effect in graphene oxide (GO) films, producing a very high thermally induced voltage (9 mV/K) under a temperature gradient. With a temperature gradient of 10 K, pTCSC device achieved a thermally charged voltage of 58 mV and stored charge of 154 µC/cm2. Also, higher voltage is thermally charged by simply connecting the multiple devices in series. We believe that our scalable fabrication of pTCSC devices suggests a future direction of sustainable energy devices utilizing thermal energy.
Effect of Electrode Composition on Heat Generation Rate in Electrical Double Layer Capacitors
Authors: Munteshari Obaidallah , Pilon Laurent
Published: February 2020

Electric double layer capacitors consist of two identical electrodes usually made of a mixture of (i) carbon-based material, (ii) binder, and (iii) other additives (e.g. carbon black). These constituents can influence the thermal behavior in the positive and negative electrodes. This study aims to investigate the effect of electrode composition on the thermal behavior of the EDLC electrodes using an isothermal calorimeter. The heat generation measurements were performed on five devices with different electrode compositions in 1M of LiPF6 in EC:DMC. First, the irreversible heat generation rate was in excellent agreement with Joule heating predicted from the internal resistance. The reversible heat generation rates in electrodes containing CMC were significantly different in the positive and negative electrodes. It was exothermic during charging and endothermic during discharging at the positive electrodes. By contrast, at the negative electrodes, it featured both exothermic and endothermic heat generation during both charging and discharging. However, in absence of CMC in the electrode, the reversible heat generation rates at the positive and negative electrodes were nearly identical. This can be attributed to that the charging mechanism in the absence of CMC was the same in both electrodes. However, in presence of CMC, the anionic functional groups formed in the electrodes interact with cations in the negative electrodes resulting in asymmetric heat generation associated with asymmetric charging mechanism.
Energy Storage and Heat to Power Conversion and with Non-Aqueous All Copper Redox Flow Batteries
Authors: Peljo Pekka , Maye Sunny , Atek Imene
Published: February 2020

In this presentation we will describe a new approach for conversion of heat into chemical energy, stored in a battery. A thermo-electrochemical system with a redox flow battery (RFB) is proposed to allow the conversion of heat at relatively low temperature into chemical energy. The electroactive species of the battery are copper ions in an organic solvent mixture containing acetonitrile as a complexing agent, resulting in a cell voltage of 1.2 V. Water is avoided because its presence reduces considerably the cell voltage. This non-aqueous hybrid redox flow battery can be utilized for electrochemical energy storage, and the efficiency of the system for this purpose will be discussed.

More interestingly, the battery can be also charged with heat. For thermal charging, the Cu(I) complex with acetonitrile can be destabilized by a heat source of around 170°C (or more). At these temperatures all the acetonitrile is distilled off and the destabilized Cu(I) species disproportionates into metallic Cu and Cu(II) species dissolved in the electrolyte. Following separation and recovery of the distilled acetonitrile the system can be discharged again. Now the chemical energy stored in the battery be converted into electricity with the Cu oxidation and Cu(II) reduction in the different half cells.

In this presentation we shall discuss the electrochemistry of copper in acetonitrile and propylene carbonate mixtures, the thermodynamic properties of the copper electrolytes as well as the heat required for the thermal regeneration, as has been evaluated by differential scanning calorimetry. Additionally, we will present our latest results with non-aqueous copper slurry electrolytes and report the efficiency of the full cycling consisting of electrochemical discharge followed by thermal charge.

The theoretical efficiency of the heat-to-power conversion has been evaluated as 30%, close to the Carnot efficiency with T
cold at 298 K and T
hot at 443 K. The losses of the cell will decrease the practical efficiency, so further improvement of the flow battery is required.
Coin-Type Cell Design and Engineering of Its Compartments for Rechargeable Seawater Battery
Authors: Han Jinhyup , Kim Youngsik
Published: February 2020

Seawater battery is a new concept energy storage device that uses seawater as a cathode material, one of the most abundant resources on the earth. It is crucial to design cells and optimize key components for the high performance rechargeable seawater batteries. Seawater batteries, which utilize natural seawater as the active material in an open-structured cathode, require a new platform for building and testing the cells other than existing Li-ion coin-type or pouch-type cells. So, we designed the coin-type seawater battery of a new platform, and we would like to introduce new findings based on our optimized cell. Engineering the cathode components—improving the wettability of cathode current collector and seawater catholyte flow—improves the voltage efficiency. In order to get reliable data from the materials that are the key elements in seawater batteries, a coin-type cell, a flow-cell tester, and their key compartments were designed and fabricated by trial and error and the testing environment was also determined.

We examined the wettability of seawater on the carbon felt (CF) cathode current collector and its effect on the charge-discharge cycling performance. The air-heating process of CFs made the surface hydrophilic, resulting in a reduced ΔV of the cell (~1.4 V) at a current rate of 0.025 mA cm-2, compared to the cell using a pristine CF (~1.6 V). We also showed that the flow of the seawater reduced ΔV (~0.7 V) by 36% from ~1.1 V under no flow state. Through these various experiments, we optimized the key factors affecting the seawater battery. Therefore, further experiments on promising materials in seawater batteries can be conducted using the customized coin-type cell, which is an essential prerequisite for the practical implementation of seawater batteries as the next generation Energy storage system (ESS).
Battery-like Response in Solid Oxide Fuel Cell Device
Authors: Guan Xiaofei , Jiang Jun , Ramanathan Shriram
Published: February 2020

The intermittency of renewable energy sources and the varying power demand throughout the day pose challenges for electrical grid stability as more and more renewable energy technologies are deployed. Existing solid oxide fuel cell technologies are slow in response to changes in current and voltage, and therefore cannot smooth out the difference between the power supply from renewables and the power demand. In this presentation, we will report a battery-like response as a new functionality incorporated into the fuel cell devices. It is realized by having in situ charge storage (e.g., metal hydrides) proximal to or integrated within the anode of the fuel cell. Electrochemical studies show a capacity density of 977 mAh g-1 in a 90-hour stable discharge. In addition, a fuel cell-battery hybrid electrochemical device was designed, and the voltage was stable at 0.86 V in the fuel cell mode and 0.73 V in the battery mode for 100 cycles over a course of 75 hours. Fuel cell with a battery mode represents a promising approach for easing the integration of intermittent renewables and enabling grid stability.
(Invited) High Energy Density Energy Storage Systems – Strategies for an Energy Independent Future
Authors: Kumta Prashant N
Published: February 2020

Energy storage is vital for realizing an energy independent future currently dominated by exploiting natural reserves supplemented by oil and gas exports. Since the commercialization of the first Li-ion battery (LIB) by Sony in 1991, there has been tremendous progress in the areas of cathode, electrolytes as well as anodes [1]. While lithiated transition metal oxides are still the flagship cathode systems largely focused on intercalation chemistry, newer chemistries exploiting alloying and zintl phase formation has been explored for use of silicon as an alternative anode. Similarly, there has been tremendous research in the area of alternative energy storage systems beyond lithium-ion intercalation chemistry. Lithium-sulfur batteries (LSB) as well as well as Li metal anodes have accordingly been the spotlight of much research activity in recent years. All systems are plagued by intransigent electronic conductivity and voltage-specific phase transition related kinetic limitations and physico-electrochemical challenges. Nano-engineered approaches appear primed for overcoming these hurdles.

We have thus, embarked on implementing dynamic theoretical and experimental strategies to develop engineered electronic and ionic conducting nanomaterials showing considerable promise. We have also developed myriad concepts over the years related to ex-situ synthesis of active-inactive nanocomposites, use of nanoscale droplets, nanoparticles, hollow Si nanotubes (h-SiNTs), cost-effective template derived nanoscale morphologies, scribable and flexible hetero-structured architectures displaying impressive capacities as high as ~3000 mAh/g with sustained cyclability and high rate capability in Si anodes[2]. Similarly, engineering approaches were implemented for generating sulfur cathodes in LSBs exploiting harnesses of inorganic, nanocomposite, tethered, and polymeric lithium ion conducting (LIC) matrices along with novel fine yarn-like and tethered architectures yielding 5.5 mAh/cm2 – 12 mAh/cm2 areal capacity as well as ~1200 mAh/g specific capacity with sulfur loadings as high as 20 mg/cm2 displaying up to 250 cycles cycling stability[3]. Engineered novel Li metal anodes are also studied as alternative safe anodes. Results of these studies will be discussed. Finally, the presentation will address the bright future of tailored functional engineered systems in the rapidly evolving digitized global internet era of the 21st century and the tremendous prospects for energy independence.

References

Wang, P.N. Kumta, et al. ACS Nano (2011);

Gattu, P.N. Kumta et al. Nano Research (2017)

M. Shanthi, P.N. Kumta et al. Electrochimica Acta (2017)
Analysis of Graphite Materials for Fast-Charging Capabilities in Lithium-Ion Batteries
Authors: Kirner Joel , Qin Yan , Su Xin , Zhang Linghong , Li Yangxing , Lu Wenquan
Published: February 2020

The application of lithium-ion batteries in electric vehicles calls for decreased cost, increased energy density, increased power density, as well as low-temperature and fast-charging capability. In regard to fast charging, it is generally understood that it is the kinetic overpotential at the graphite anode that limits the cycling rate in modern commercial battery formulations. In this work, we study the fast-charging capabilities of a series of doped and un-doped graphite samples from a commercial supplier, as part of a materials validation effort at Argonne National Laboratory. We combine materials characterization data from the raw samples with electrochemical characterization of graphite laminate electrodes in both half and full cell configurations to explore the causes of differences in rate performance and its impact on cycle life.

Acknowledgement:

We gratefully acknowledge the support from the U.S. Department of Energy’s (DOE) office of Energy Efficiency & Renewable Energy (EERE) Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory, a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357.
The Chemical stability of Commercial Polymer Electrolyte Membrane for Vanadium Redox Flow Battery (VRFB)
Authors: Jung Ho-Young , Lim Min-Hwa , Jung Ji-Hyun
Published: February 2020

In this study, various commercialized ion conductive membrane were analyzed by chemico-physical degradation. Chemico-physical degradation of Dupont’s Nafion 212 as a reference material, and F. Co. Ltd.’s cation exchange membrane F-1, anion exchange membrane F-2, and F-3 was analyzed to confirm the characteristics suitable for VRFB’s operation. To study ion exchange membrane’s degradation mechanism, experiments regarding hydrolytic stability, permeability and chemical stability of VO2
+ ion were also conducted. In order to compare the performance of VRFB’s long term operation, the membrane’s chemical stability was tested. After hydrolytic stability test, it was confirmed that there was a decrease in polymer’s weight and in distilled water’s pH, which leads to membranes’ degradation. To test the stability of polymer membrane and degradation mechanism, it was soaked in 0.1 M V(V) solution for 72 h. Then, change in concentration was measured by UV-vis Spectrum. Stability of F-series membrane showed higher stability than Nafion membrane, indicating a suitable membrane for VRFB’s long-term operation.
Shear-Thickening Electrolytes for Li-Ion Batteries
Authors: Sacci Robert L , Shen Brian H , Tenhaeff Wyatt , Veith Gabriel M.
Published: February 2020

Here, we will report on the electrodynamics of a shear-thickening electrolyte that may serve a multifunctional purpose in Li-ion batteries: a high conductive and impact resistance ion conductor. Perhaps more important than the continual improvement in charge and power density of batteries for consumer electronics and vehicles is the need to improve safety and reliability. The incorporation of safety features typically comes with added weight and handicapped performance. Multifunctional materials may aid in alleviating these particular drawbacks by providing both mechanical strength and contribution to charge storage or ion conduction. A common strategy in making batteries safer is the replacement of the liquid electrolytes with solid state ones, as this removes the need for volatile and flammable organics and may allow for the use of lithium metal. However solid state electrolytes currently are expensive and difficult to process and incorporate into large scale batteries.

We have developed shear-thickening lithium ion battery electrolytes for improved safety in high impact events. They are able to reversibly transition into a solid-like phase under high shear and then relax back into a liquid when free of stress. While we will demonstrate that this aids in the prevention of shorting and subsequent combustion of volatile electrolyte under such conditions, this presentation is focused on our investigation of the electrodynamics of shear-thickening electrolytes using conductivity under shear measurements. We incorporate finite element modeling to aid in interpreting the observation of an order of magnitude drop in ionic conductivity under shear-thickening conditions. We explain the substantial drop in conductivity under shear in terms of a change in effective viscosity, as suggested by Figure 1, though we acknowledge that a change in tortuosity is possible. The results here can be generally applied to any electrolyte that exhibits non-Newtonian hydrodynamic properties.

This material is based upon work supported by theU.S.Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program (BHS). The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. This work was supported by the U.S.Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering (RLS, GMV).

Figure 1
Understanding the Role of Aluminum in Positive Electrode Material Structures
Authors: Han Binghong , Key Baris , Vaughey John T. , Dogan Fulya
Published: February 2020

Application of aluminum substitution (doping) for transition metals are commonly used in lithium ion batteries to improve electrochemical performance, chemical and thermal stability of the cathode materials. However understanding the nature of surface and lattice aluminum environments or understanding possible aluminum diffusion on the interphase have been a challenge for aluminum bearing Li-ion battery materials such as LiNi1-y-zCoyAlzO2 (NCA), aluminum doped LiNixMnyCozO2 (NMC) and coated layered metal oxides. Solid state NMR spectroscopy is one of the few structural probes available that can qualitatively and quantitatively characterize lattice and non-lattice (i.e. surface, coatings, segregation, secondary phase etc.) aluminum coordinations. In the present study, we use NMR to gain new insights into transition metal (TM)-O-Al coordination’s, interfacial composition in pristine cathodes and evolution of lattice aluminum sites and solid electrolyte interface upon cycling. For each cathode composition, aluminum coordination of paramagnetic (lattice) and diamagnetic (non-lattice) nature have been investigated and their effect on cycling performance and surface film composition is reported.
Safe Impact Resistant Electrolytes (SAFIRE)
Authors: Veith Gabriel M. , Armstrong Beth , Kalnaus Sergiy , Wang Hsin , Tenhaeff Wyatt
Published: February 2020

We present work on the development of inherently safer multifunctional electrolytes which are designed to undergo a massive rheological response upon application of a shear force. These electrolytes are built from colloidal particles stabilized in an aprotic electrolyte. Upon impact the particles align forming an apparent solid. This solid barrier prevents electrodes from touching during an impact resulting in a spontaneous discharge and thermal runaway. This presentation will talk about the chemistry of these materials, the cycling of full cells, and ionic conductivity of the materials.

The work presented herein was funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR-0869-1617. The authors particularly thank Ping Liu, Susan Babinec, and Julian Sculley for their helpful discussions.
Poly(propylene carbonate) Interpenetrating Cross-Linked Poly(ethylene glycol) Based Polymer Electrolyte for Solid-State Lithium Batteries
Authors: Williams Jere A. , Yang Yiqun , Pandey Gaind P. , Meda Lamartine
Published: February 2020

Lithium-ion conducting solid polymer electrolytes (SPEs) are promising materials to replace flammable liquid electrolytes to solve the safety and performance issues in conventional rechargeable lithium batteries [1]. Poly(ethylene oxide) (PEO) has been studied extensively as baseline materials for SPEs. It is well known that pure PEO crystallizes at room temperature, hampering lithium ion migration and resulting in low ionic conductivity. This drawback hinders PEO based SPEs applied in real battery configuration that usually requires ionic conductivity greater than 10-4 S cm-1 at 25 ℃. In general, suppression of polymer crystallinity is favorable for SPEs to enhance the ionic conductivity [2]. Here, we synthesized a semi-interpenetrating polymer network (s-IPN) from the mixture of poly(propylene carbonate) (PPC), poly(ethylene glycol) methylether acrylate (PEGMEA), poly(ethylene glycol) diacrylate (PEGDA), and lithium bis(trifluoromethane) sulfonimidate (LiTFSI) salt using one-pot thermal curing method. The amorphous PPC performs as film forming agent, whereas the crosslinked network with PEG pendants provides lithium conducting channel. The s-IPN architecture inhibits the phase segregation of two different polymers. Curing temperature, crosslinker PEGDA content and salt concentration were optimized carefully to attain a flexible film with ionic conductivity reaching 5×10-6 S cm-1 at ambient temperature. The ionic conductivity and working potential window were correlated with the thermal and physical properties of the s-IPN electrolytes. Differential scanning calorimetry measurements have shown a decrease in the crystallinity of the s-IPN electrolytes. The electrolyte with higher salt concentration has lower ionic conductivity, consistent with higher glass transition temperature of PEG chain. The ionic conductivity was further enhanced by incorporating lithium ion conductive ceramic powder, lithium lanthanum zirconate (LLZO) as a filler into the s-IPN matrix, even though LLZO aggregation occurred during film forming. The optimized s-IPN has potential as a baseline material for future solid-state electrolyte designs.

Acknowledgements

We gratefully acknowledge the financial support from the NASA MIRO Program #NNX15AP44A and the National Science Foundation under Award #162-6449.

References

[1] Kang Xu. Electrolytes and Interphases in Li-Ion Batteries and Beyond. Chem. Rev. 2014, 114, 11503–11618

[2] Yu Wang, Wei-Hong Zhong. Development of Electrolytes towards Achieving Safe and High-Performance Energy-Storage Devices: A Review. CHEMELECTROCHEM 2015, 2, 22–36
Implications of Cation-Disordered Atomic Structure on Electrochemical Performance of LiNi0.5Co0.2Mn0.3O2 Cathode Material
Authors: Shim Jae-Hyun
Published: February 2020

Scanning transmission electron microscopy (STEM) with aberration correction is a powerful imaging method to resolve real-space local crystallography on the atomic scale with the high precision. Combining this imaging tool with electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDX), this approach revealed that the cation disorder phenomenon mainly occurs on the surface of the NCM materials (usually less than 10-nm deep to the surface) and the interlayer mixing between transition metals and Li and the related local structure changes is strongly dependent on the type of transition metals.1-3

In this work, the cation-disordered layer of the LiNi0.5Co0.2Mn0.3O2 cathode materials for Li ion battery is controlled by adjusting the ratio of lithium to transition metal, which has been found to have a definite relationship with battery performance. In addition to image analysis using STEM, atomic distribution analysis using EDS and distribution of the oxidation state by EELS were performed. In order to elucidate the origin of this effect from the view point of atomic structure. In particular, the structural characteristics were established through STEM image simulation software based on STEM results. The effect of the structure on the electronic conductivity was investigated by chemical calculation. In addition to the chemical calculated results, the physical phenomenon was observed through the current atomic force microscopy (C-AFM) experiment in the controlled region which is grainboundary in this study, and it was found that the electrochemical performance of the Li ion battery is improved due to the high electronic conductivity in the grain-boundary.

[1] Yan, P.; Zheng, J.; Lv, D.; Wei, Y.; Zheng, J.; Wang, Z.; Kuppan, S.; Yu, J.; Luo, L.; Edwards, D.; Olszta, M.; Amine, K.; Liu, J.; Xiao, J.; Pan, F.; Chen, G.; Zhang, J.-G.; Wang, C.-M. Chemistry of Materials 2015, 27, (15), 5393-5401.

[2] Xiong, X.; Wang, Z.; Yue, P.; Guo, H.; Wu, F.; Wang, J.; Li, X. Journal of Power Sources 2013, 222, 318-325.

[3] Chen, Z.; Wang, J.; Chao, D.; Baikie, T.; Bai, L.; Chen, S.; Zhao, Y.; Sum, T. C.; Lin, J.; Shen, Z. 2016, 6, 25771.
Self-Assembly of Flexible Free-Standing Three-Dimensional Porous MoS2-Reduced Graphene Oxide Film for High-Performance Lithium-Ion Batteries
Authors: Chao Yunfeng , Jalili Rouhollah , Ge Yu , Wang Caiyun , Zheng Tian , Wallace Gordon
Published: February 2020

Free-standing and flexible battery electrodes are highly pursued due to its good electrochemical performance and transformation ability. Two-dimensional materials such as transition metal dichalcogenides (TMDs) and graphene with large surface area and good mechanical properties provide a good solution for this problem. The high lithium storage of MoS2 is attractive for achieving high capacity while the high conductivity of graphene is of favorable for good rate capability. The excellent mechanical properties of graphene are able to form a stable structure contributing to long cycle life, flexibility and get rid of substrates [1, 2].

A self-assembly process was developed to produce MoS2/ reduced graphene oxide (MG) hydrogel films in this work. Making use of the ordered structure existed in liquid crystalline graphene oxide (LCGO) dispersion [3], a layer structure with small MoS2 nanosheets sandwiched between large LCGO nanosheets could be easily obtained by simply mixing their dispersion together. A heating process at 70 ℃ was used to accelerate the self-assembly process. The unique layer structure turned into a three-dimensional porous structure during the self-assembly process and preserved after freeze-drying, which could effectively increase the surface area of active materials for high performance.

This work develops a simple, straightforward and cost-effective method to fabricate self-assembled, layer-by-layer, free-standing porous MG hydrogel films. The structure displayed excellent electrochemical properties as a lithium-ion battery electrode [4]: a high discharge capacity of 800 mAh g-1 at a current density of 100 mA g-1; and an excellent cycling stability with slightly increased capacity (112.5%) after 500 cycles at a current density of 400 mA g-1. Such enhancement can be ascribed to the synergistic effect between these two components and gradual perfection of the ordered structure. This approach enables the exploitation of the LC order of GO sheets to organize and align 2D MoS2 in-between GO sheets, which may provide a new avenue for the development of 3D porous flexible composite electrode materials with high performance using the unique LCGO.

References:

[1]. N. A. Kumar, M. A. Dar, R. Gul and J. B. Baek, Materials Today, 2015, 18, 286-298.

[2]. M. Yang, S. Ko, J. S. Im and B. G. Choi, Journal of Power Sources, 2015, 288, 76-81.

[3]. R. Jalili, S. H. Aboutalebi, D. Esrafilzadeh, K. Konstantinov, J. M. Razal, S. E. Moulton and G. G. Wallace, Materials Horizons, 2014, 1, 87-91.

[4]. Y. Chao, R. Jalili, Y. Ge, C. Wang, T. Zheng, K. Shu and G. G. Wallace, Advanced Functional Materials, 2017, 27, 1700234.
Synthesis of Molybdenum Carbide and Formation of an Epitaxial Mo2c/MoS2 Hybrid Structure Via Carburization of Molybdenum Disulfide
Authors: Jeon Jaeho , Lee Jinhee , Choi Seunghyuk , Lee Byoung Hun , Song Young Jae , Cho Jeong Ho , Jang Yun Hee , Lee Sungjoo
Published: February 2020

The epitaxial formation of metallic molybdenum carbide (Mo2C, a 2D MXene material) is achieved via chemical conversion of molybdenum disulfide with thermal annealing under CH4 and H2. A fully converted metallic Mo2C and Mo2C/MoS2 hybrid junctions could be provided with the adjusting of synthesis area of Mo2C the thermal annealing period. Mo2C film shows a metallic property as the outstanding electrode with a low sheet resistance (123.6 Ω/cm2) and carrier concentration of 5.84Х1013 /cm2. Mo2C/MoS2 hybrid junctions display a low contact resistance (1.2 kΩ∙μm) and low Schottky barrier height (26 meV), indicating the material’s potential utility as a critical hybrid structural building block in future device applications. Mo2C grows and forms a Mo2C/MoS2 hybrid structure were simulated by density functional theory calculations to model the mechanisms. The results show that Mo2C conversion is initiated at the MoS2 edge and undergoes sequential hydrodesulfurization and carbide conversion steps, and an atomically sharp interface with MoS2 forms through epitaxial growth of Mo2C. This work provides the area-controllable synthesis of a manufacturable MXene from a transition metal dichalcogenide (TMD) material and the formation of a metal/semiconductor junction structure. The present results will be of critical importance for future 2D heterojunction structures and functional device applications.
(Invited) The Impact of the Phase and Stacking of 2D Materials on Their Properties and Applications
Authors: Jin Song
Published: February 2020

The interesting and tunable properties of layered metal dichalcogenides (MX2) and other layered materials heavily depend on their phase and layer stacking. We discovered that chemical exfoliation of layered MX2 nanosheets and simultaneous conversion from the semiconducting 2H polymorph to the metallic 1T polymorph grants greatly enhanced activity for electrocatalytic hydrogen evolution reaction (HER). We have also developed layer-controlled vertical heterostructures of MX2 by van der Waals epitaxy that have strong electronic interactions across the heterojunctions. We explain how the layer stacking and physical properties of MX2 are influenced by screw dislocations. A one-to-one correlation of atomic force microscopy and high- and low-frequency Raman spectroscopy of many dislocated WSe2 nanoplates reveals variations in the number and shapes of dislocation spirals and different layer stackings that are determined by the number, rotation, and location of the dislocations. These lead to three class of behaviors: plates with triangular dislocation spirals have non-centrosymmetric stacking that gives rise to strong second-harmonic generation, plates with hexagonal dislocation spirals form the bulk 2H layer stacking commonly observed, and plates containing mixed dislocation shapes have intermediate non-centrosymmetric stackings with mixed properties. We also explain layer stackings also determine the etching behaviors of multilayer WSe2 materials that result in complex chemically derived kirigami structures.
(Invited) Nanostructured Graphene-Coated Cathodes for High-Performance Lithium-Ion Batteries
Authors: Hersam Mark C.
Published: February 2020

Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at -20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation.
Black Phosphorus p-Doping By Integration of MoS2 Nanoparticles
Authors: Jeon Sumin , Kim Minwoo , Jia Jianyuan , Park Jin-Hong , Song Young Jae , Lee Sungjoo
Published: February 2020

A new doping method of BP by integration of density-controlled monolayer MoS2 nanoparticles (NPs) is demonstrated. MoS2 NPs with different density were synthesized by chemical vapor deposition (CVD) and transferred onto a few-layer BP channel, which induced a p-doping effect. The hole concentration of BP was controlled with different densities of MoS2 NPs in a range of 1012 - 1013 cm-2. The doping mechanism was explained by a charge transfer by work function differences between BP and MoS2 NPs, which was confirmed by Kelvin probe force microscopy (KPFM) and electrical measurements. Raman and X-ray photoelectron spectroscopy (XPS) were measured to confirm the oxidation on the edge of MoS2 NPs and a doping effect of MoS2 NPs on a BP channel. This result shows promising possibility for BP device functionalization by decorating various NPs, which will enhance the device performance such as photoresponsivity, or chemical sensitivity.
Substrate Ligand Effects on Atomically Thin 2D Platinum on Graphenated 3D Structures
Authors: Arnold Christopher , Buntin Parker , Warner Jamie H , Kacher Josh , Abdelhafiz Ali , Alamgir Faisal M
Published: February 2020

This work explores the novel concept of electrochemically deposited wetted monolayer to few multilayers of Pt on a graphenated 3D Ni foam (Pt-ML/GR/Ni). Commercially available, highly porous, Ni foam capped with graphene was utilized as a substrate for layer-by-layer Pt growth by surface-limited electrochemical deposition. A survey of literature reveals that our resulting Pt-ML/GR/Ni architecture is the first instance of 3D rendered graphene being used as a template for 2D Pt growth via room-temperature synthesis. XPS, CV, SEM/EDS and high-resolution TEM characterization reveals that graphene covers much of the Ni foam and that the Pt grows epitaxially on the graphene. This scheme allows us to approach theoretical limits of Pt utilization for electrocatalytic applications, such as the canonical oxygen reduction reaction (ORR). Analysis of the ORR overpotential in Pt-ML/GR/Ni in comparison to that of the Ni-free Pt-ML/GR shows that the Dirac cone of the Pt/GR is intact, making the graphene essentially ‘electron transparent’ to the Ni-to-Pt charge transfer. Such Pt-ML/GR architectures can thus allow the surface Pt atoms to be electronically tuned by an underlying ligand of choice. This synthesis approach may prove extremely valuable for high-utilization, low-loading, electronically tunable catalysts. We present here a thorough investigation of the atomic/electronic structure and of the related evolution of electrocatalytic properties as a function of the number of graphene-templated 2D Pt layers.
TMDC 2D Materials Synthesis via Two Steps Solution Process at Low Temperature
Authors: Choi Woon-Seop
Published: February 2020

In nanoelectronics and optoelectronics, two-dimensional transition metal dichalcogenides (2D TMDC) analogous to graphene have drawn considerable attention due to their electrical and innate band gap characteristics. Among them, MoS2 and WS2 show unique properties; direct and indirect band gap of 1.8 eV and 1.2 eV, respectively, depending on the monolayer stacking states. Thin layered WS2 composed of a S-W-S sandwich crystalline with a van der Waals, possessed the coupled spin and valley physics, high photoluminescence efficiency, and composited layered materials with other 2D for many applications. Most studies on 2D TMDC have been focused on the chemical synthesis using chemical vapor deposition (CVD) and mechanical methods like exfoliated flakes by taping or in liquid. In contrast, large scale synthesis of WS2 via solution-process is rare to find.

Here, we have prepared new synthetic route combining solution coating and CVD process together. The solution of sodium tungstate soulution and hydrizene hydrate with sodium thiosulphate was coated on the silicon wafer. The coated films from dip coating and spin coating were treated in the CVD with different paramerters to obtain WS2 crystal structures. The temperature and coating conditions were modified to obtain uniform wafer-scale films. The average of 50 um size WS2 crystals with triangle shapes could be obtained at the low temperatures of 700oC and above with sample positions in the CVD.
Anionengineered Molybdenum Disulfide Thin Film/p-Type Si Heterojunction Photocathode for Efficient Hydrogen Evolution Reaction
Authors: Choi Kyougn Soon , Jeon Cheolho , Kwon Ki Chang , Choi Seokhoon , Lee Joohee , Hong Kootak , Son Woonbae , Kim Younghye , Han Seungwu , Kim Soo Young , Jang Ho Won
Published: February 2020

We synthesized transferrable and transparent anion-engineered molybdenum disulfide thin-film catalysts through a simple thermolysis method by using [(NH4)2MoS4] solution and powder precursors with different sulphur/phosphorus weight ratios. The synthesized sulphur-doped molybdenum phosphide (S:MoP) thin film changed from a two-dimensional van der Waals structure to a three-dimensional hexagonal structure by introduction of phosphorus atoms in the MoS2 thin film. The S:MoP/p-Si heterojunction photocathodes showed a high photocurrent density (33.13 mA/cm2 at 0 V vs. the RHE), large overpotential shift (0.9 V at 10 mA/cm2), and long-term stability (over 10000 s). The characterization of the S:MoP/p-Si photocathodes revealed that they could act not only as surface active catalysts owing to their low hydrogen adsorption Gibbs free energy but also as passivation layers owing to their 3D tight bonding between molybdenum and sulphur or phosphorus atoms. Anion-engineering of the MoS2 thin film catalyst would be an efficient way to enhance the catalytic activity for photoelectrochemical water splitting.

Figure 1
(Invited) 3D Circuitry and Folding with 2D Crystals
Authors: Park Jiwoong
Published: February 2020

Two thousand years ago, the mass-manufacturing of paper simplified all aspects of information technology: generation, processing, communication, delivery and storage. Similarly powerful changes have been seen in the last century through the development of integrated circuits based on silicon. Monolayers of 2D crystals provide an ideal material platform for realizing these integrated circuits thin and free-standing, which were the key advantages of paper over other medium two thousand years ago. Once realized, these atomically thin circuits will be foldable and actuatable, which will further increase the device density and functionality, allowing them to be used tether-free (or wirelessly) in environments not previously accessible to conventional circuits, such as water, air or in space. In this talk, we will discuss our recent progresses toward building atomically-thin integrated circuits using wafer-scale 2D crystals. In order for this, we developed a series of approaches that are scalable, precise, and modular. We developed wafer-scale synthesis of three atom thick semiconductors, reported a wafer-scale patterning method for one-atom-thick lateral heterojunctions, and showed how atomically thin films and devices can be vertically stacked to form more complicated 3D circuitry. Then we will discuss our most recent efforts to turn these 2D circuits into 3D structures.
(Invited) Amphiphilic Block Copolymers and Their Hybrids for Efficient Aqueous-Processed Solar Cells
Authors: Luscombe Christine , Li Junhuan
Published: February 2020

Due to their low cost and high efficiency, polymer/nanocrystal hybrid solar cells have attracted much attention in recent years. Additionally, aqueous-processed solar cells are attractive because they exhibit the potential to produce clean energy via the use of nontoxic solvents. The use of water instead of toxic organic solvents during the fabrication process of these devices is capable of significantly reducing the environmental impact as well as the production cost. In

aqueous-processed solar cells, hybrid solar cells employing water-soluble conjugated polymers and inorganic nanocrystals as photovoltaic materials have gained much attention. These hybrid materials take advantage of both water-soluble conjugated polymers and nanocrystals, which exhibit adjustable absorption properties through structural modification, efficient charge carrier generation, and high charge carrier mobility.

Water-soluble conjugated polymers are typically homopolymers with ionic (i.e., sulfonate and phosphonate moieties) or nonionic, hydrophilic (i.e., hydroxyl and glycol moieties) side chains. Unfortunately, the use of hydrophilic side chains in these conventional water-soluble conjugated polymers adversely affected the stacking of the polymer backbone, which can lead to the deterioration of their optoelectronic properties and thus a lower power conversion efficiency in solar cells. Furthermore, these side chains may cause charge trapping when applied in the active layer, which results in the further reduction in performance

In this presentation, the use of a water-soluble hybrid material consisting of amphiphilic block copolymers and cadmium telluride nanocrystals as the active layer in hybrid solar cells will be discussed. The amphiphilic block copolymers composed of poly(3-hexylthiophene) (P3HT) and poly(acrylic acid) (PAA) self-assembled into ordered nanostructured micelles which then transformed to nanowires by co-micellization with P3HT additives. Furthermore, after annealing, the hybrid materials formed an interpenetrating network. The properties of the hybrid materials and the film morphology, and how they correlate to the device performance will be discussed.
(Invited) Improved Interfaces in Multilayered Organic-Inorganic Hybrid Solar Cells with π-Conjugated Polymers-Antimony Sulfide-Strontium Titanate-Titanium Oxide
Authors: Yukawa Mayumi , Hayakawa Akinobu , Sagawa Takashi
Published: February 2020

We have developed various organic-inorganic hybrid solar cells using Sb2S3-based composites with π-electronic molecules [1,2]. For examples, utilization of zinc phthalocyanine (ZnPC) for the hybrid solar cell composed of glass/indium-tin-oxide (ITO)/TiO2/Sb2S3/ZnPC/Au achieved long durability with keeping the relative power conversion efficiency (PCE) of 90% after the stability test under 1 sun at 63 °C at a relative humidity of 50% for 1,500 h [1]. Using La-decorated Sb2S3 for hybrid solar cell composed of glass/F-doped SnO2 (FTO)/TiO2/La-decorated Sb2S3/poly[(3-hexylthiophene)-2,5-diyl] (P3HT)/poly[3-(3-carboxypropyl)thiophene-2,5-diyl] (P3CT)/Au resulted in 33% improvement of PCE as compared to that of the non-decorated Sb2S3 because of lowering the resistance at the interface, which was confirmed by the impedance analyses [2]. While doping of Zn into Sb2S3 attained 57% enhancement of PCE. This result is ascribed to the effective lowering the bulk-resistance [2]. In this context, we newly inserted SrTiO3 layer between TiO2 and Sb2S3 interface and found the enhancement of the open circuit voltage (VOC
) from 0.61 V to 0.74 V. Temperature dependence of VOC
for SrTiO3-inserted device indicated the maximum voltage was 1.7 V, which had been estimated by extrapolation of the line to 0 K. For further improvement of the photovoltaic performance, we modified the thin-film making process for Sb2S3 layer from the previously reported procedures [1,2]. After the spin-coating of the precursor solution of SbCl3-thiourea complex in DMF onto the SrTiO3 layer, heat treatment at 220 °C under vacuum was newly performed. The thickness, surface roughness, and sea-island structure were optimized by their uv-vis measurement, AFM, TEM observations, and current density-voltage (J-V) characteristics in terms of transmittance, reflectivity, and short circuit current density (JSC
) by changing the spin-coating speed, duration of heating, and so on. Through the optimization, remarkable enhancement of JSC
from 10.7 mA cm-2 to 13.6 mA cm-2 and improvement of PCE from 4.7% to 6.1% were achieved.

[1] A. Hayakawa, M. Yukawa, and T. Sagawa, ECS J. Solid-State Technology, 6(4), Q35-Q38 (2017).

[2] M. Yukawa, A. Hayakawa, and T. Sagawa, ECS Trans., 77(11), 653-659 (2017).
(Invited) Carbon Nanotube and Porphyrins: Materials for Optics and Energy Applications
Authors: Hanana Manel , Delport Géraud , Le Gac Stéphane , Voisin Christophe , Jousselme Bruno , Boitrel Bernard , Lauret Jean-Sébastien , Campidelli Stephane
Published: February 2020

The fabrication of functional hybrid materials that preserves and combines the properties of their building blocks is a central issue of nanosciences. Among the different classes of nanomaterials, carbon nanotubes are promising for electronics, opto-electronics, catalysis and composite applications. In this context the combination of nanotubes with porphyrins has been widely explored for catalytic1,2 or electron transfer purposes.3,4

Here I present two results obtained recently on the nanotube/porphyrin composites, the first deals with the supramolecular organization in micelles of porphyrins around the nanotubes.5 In this work we were able to explain the Davidoff splitting observed on the absorption bands of the porphyrins by their organization around the nanotubes. The second deals with the synergic effect on catalytic activity of carbon nanotubes and strapped iron porphyrin hybrids for Oxygen Reduction Reaction (ORR).6 In particular, we demonstrated that the combination of both components - MWNTs and porphyrin - leads to a better catalytic activity than those of the nanotubes or the porphyrins taken separately. This study highlights the importance of the carbon support for the catalysis. The nanotubes ensure the availability of electrons to the porphyrin catalysts and allow the ORR to occur via the 4-electron pathway, avoiding the production of hydrogen peroxide.

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