bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Ternary Blended Materials of Li1.2Mn0.4Ni0.16Co0.24O2, the Li2MnO3-Stabilized Compound, and Olivine Fluorides (Li2MPO4F) As a High Capacity Cathode Materials for Lithium Ion Batteries
Authors: Agubra Victor Anafo , Moore Todd , Kemp Ricardo , Intekhab Abdullah Farooq
Published: February 2020

The area of blended cathode materials is still evolving and there are very few research on the subject. The blending parent cathode materials typically involves high capacity electrode materials; layered oxides compounds with spinel cathode compounds that are lower in cost, more environmentally benign and higher operating voltage. These blended cathode materials are expected to be resilient in terms of storage capacity, cycle life, cheaper and environmentally safer. However, chemically, there are exist challenges in pairing a high- operating voltage material and high capacity material and still achieving less resistance, greater storage and cycle life may be difficult to achieve, since high voltages are likely to enable more degradation pathways.

This paper seeks to explore a composite systems made of three different cathode materials involving lithium rich compounds Li1.2Mn0.4Ni0.16Co0.24O2, the Li2MnO3-stabilized compounds, spinel, or Olivine fluorides (Li2MPO4F). This study aims to design a better ternary system that meets the high energy density demand for hybrid electric vehicles and at the same time, minimizes the salient but important material properties like the thermal stability, longer life, high capacity and yet meet bottom line. The paper therefore explores a thorough understanding of the various interaction of each of the compounds so as to tailor their properties to have that synergy, conducting basic scientific analysis of the particle-to particle interaction at the atomic level, as well as the chemical interaction of the constituents in the ternary system to achieve the synergistic effect.
Study of Cell Configuration on the Zinc-Air Battery Performance
Authors: Lu Cian-Tong , Chen Sheng-Wen , Chang Yu-Ling , Hsueh Kan-Lin , Wu Ching-Chen , Yang Chang-Chung , Chang Wen-Sheng
Published: February 2020

Zinc air battery has high energy density and low material cost. It has great potential for large-scale energy storage or electrical vehicle applications. Power density is one of the critical factor for these applications. It is heavily depending on the cell configuration. Four different zinc air batteries were design, fabricated, and tested. Cells under investigation are: 1. ORR (oxygen reduction reaction) half-cell, 2. planar cell (parallel electrode separated by a porous separator filled with electrolyte), 3. stationary electrolyte cell (parallel electrode separated by a stationary electrolyte), 4. circulated electrolyte cell (parallel electrode separated by a circulated electrolyte), and 5. stack with 10 cells in series (Parallel electrode separated by stationary electrolyte and ten cells are laminated stacking together). Their maximum power densities were varied from mW cm-2 to hundred mW cm-2. We found that the thickness of cathode, discharge of gas bubble in the electrolyte, internal resistance, and contact resistance, etc. are playing an important factor on the cell power density.

Figure 1
Surface Energy Modulation of PdCu Nanocatalysts Via the Crystal Structure Change for Lithium-Oxygen Battereis
Authors: Park Mihui , Liang Chaoping , Agyeman Daniel Adjei , Cho Kyeongjae , Kang Yong-Mook
Published: February 2020

Palladium-copper (PdCu) alloys have two representative crystal structures; one is body-centered cubic (bcc), the other is face-centered cubic (fcc) even though both Pd and Cu originally have fcc crystal. The fcc PdCu alloys have disordered structure within which Pd and Cu have solid-solution in fcc lattice, whereas the bcc PdCu alloys have ordered structure which consists of alternative layers with either Pd or Cu atoms.

In particular, bcc PdCu alloys have occasionally shown superior performance to fcc PdCu alloys since the unique ordered structure of bcc has isolated Pd on the surface. Most of bcc PdCu alloys have been synthesized for structural transformation by annealing or seed-growth method of fcc PdCu alloys with inevitable grain growth, uneven surface structure and particle size distribution. Despite these limitations, the Pd on the bcc surface which is provided charge flow from Cu serves as an active site for catalytic reaction, which is highly favorable for lithium-oxygen battery. However, the same size of fcc and bcc PdCu alloys is quite difficult to be obtained since the crystallites larger than 20 nm favor the ordered bcc structure with lower symmetry. Thus, bcc PdCu alloys in nanoscale have been rarely reported, consequently fcc and bcc PdCu nanoparticles (NPs) have never been properly compared until now.

In this study, we successfully synthesize fcc and bcc PdCu alloys in nanoscale through precisely adjusting the driving force for reducing organometallic complex. The bcc PdCu NPs with higher surface energy govern the growth thermodynamics of discharge product and greatly improved battery performance based on density functional theory calculation and experimental proof. This study provides critical descriptor on material design in the perspective of modulating surface structure via crystal structure to tune its intrinsic properties.
The Relationship between the Oxygen Vacancies Density with the Electronic and Optical Properties of Hafnium Oxide
Authors: Islamov Damir R. , Gritsenko Vladimir A. , Kruchinin Vladimir N. , Lebedev Mikhail S.
Published: February 2020

Hafnia-based high-κ dielectrics are widely used in modern MOS devices, perspective RRAM and FRAM cells, dopand of ceramics in teeth prosthetic. The electronic properties of HfO2, such as leakage currents and luminescence, are defined by traps and defects. The presence of traps increases the conductance of dielectric. Electron or hole localization on traps shifts the voltage threshold and leads to device degradation. In active layers of RRAM, traps act as precursors of a filament during the HRS/LRS switch. The trap density ≲1022 cm-3 is a huge for degeneration of devices, but is very low for detecting within chemical analytical techniques. Previously, it was reported that comparison measured J-V dependencies with multiphonon transport models allows extracting the density of oxygen vacancies (VO), which acts as traps, in the HfO2. In the study, we try to get correlations between the trap density and optical properties of hafnia films.

Variation of the trap density in HfO2 was supported by different conditions of film synthesis using ALD technique and different precursors: TEMAH+H2O and Hf(thd)4+O2. The series of samples was annealed in N2-flow for 1 hour at different temperatures. Annealing was performed directly in the reaction chamber at T
ann = 440, 550 and 700 °C for TEMAH+H2O samples and T
ann = 550 and 700 °C for samples deposited from Hf(thd)4+O2 precursor system. Dispersion dependencies of refractive index were measured by spectral and laser ellipsometry. It was found that the refractive index grows as films are depleted by oxygen. The results offer a new in situ technique for quality evaluation of synthesized HfO2 films, namely evaluation of oxygen vacancy density.

The work was supported by the Russian Science Foundation, grant #16-19-00002.
Chain Length Dependence of the Dielectric Constant and Polarizability in Conjugated Organic Thin Films
Authors: Van Dyck Colin Jean-Louis , Marks Tobin , Ratner Mark A
Published: February 2020

Dielectric materials are ubiquitous in optics, electronics and materials science. Recently, there has been new effort to characterize the dielectric performance of thin-films made of polarizable molecule assemblies, at both theoretical and experimental levels. [1-3] In this context, we will present the relation between the polarizability of the constituting molecule and the film dielectric constant, using periodic Density Functional Theory (DFT) calculations, for conjugated and saturated chains.

We particularly explore the implication of the peculiar chain length dependence of the polarizability for conjugated molecules. We show and explain from DFT calculations and a simple Clausius-Mossotti-like depolarization model how this chain-length dependence is affected by the collective polarization. We show that a high sensitivity of the dielectric constant to the thin-film thickness is expected for conjugated molecules. This latter can increase by a factor of 3-4 at a reasonable coverage, just by extending the molecular length. This significantly limits the decline of the thin-film capacitance with the film thickness.[4]

[1] Heitzer et al, Acc. Chem. Res., 2016, 10.1021/acs.accounts.6b00173

[2] Suchand Sangeeth et al, JACS, 2016, 10.1021/jacs.6b02039

[3] Bergren et al, J. Phys. Chem. C, 2010, 10.1021/jp106362q

[4] Van Dyck et al, ACS Nano, 2017, 10.1021/acsnano.7b01807

Figure 1
(Invited) Epitaxial Growth of 2D Transition Metal Dichalcogenide Monolayers, Alloys and Heterostructures
Authors: Zhang Xiaotian , Chubarov Mikhail , Choudhury Tanushree , Redwing Joan M.
Published: February 2020

Two-dimensional (2D) transition metal dichalcogenides (TMDs) comprise a compelling class of new materials with intriguing properties that arise from their ultra-thin form, thickness-dependent bandstructure, large exciton binding energies and unusual spin and valley polarization physics. The majority of the research that has been carried out thus far employs ultra-thin TMD flakes exfoliated from bulk crystals but future device development requires the ability to synthesize large area single crystal films and heterostructures. Our research is aimed at the development of an epitaxial growth technology for TMDs and related layered chalcogenides based on gas source/metalorganic chemical vapor deposition (CVD/MOCVD) to enable monolayer growth over large substrate areas and layer-by-layer growth of heterostructures.

Our recent studies have focused on the epitaxial growth of WSe2 and (Mo,W)S2 monolayer films, alloys and heterostructures using metal hexacarbonyl and hydride chalcogen precursors on substrates including sapphire and hexagonal boron nitride (hBN). A multi-step precursor modulation growth method was developed to independently control nucleation density and the lateral growth rate of TMD domains on the substrate. This approach also enables an estimation of metal-species surface diffusivity and domain growth rate as a function of growth conditions providing insight into the fundamental mechanisms of monolayer growth. Using the multi-step growth process, coalesced monolayer and few-layer TMD films were obtained on sapphire substrates up to 2” in diameter at growth rates on the order of ~ 1 monolayer/hour. In-plane X-ray diffraction demonstrates that the films are epitaxially oriented with respect to the sapphire resulting from a merging of 0o and 60o oriented domains. Room temperature photoluminescence (PL) measurements demonstrate strong emission peaks in the range of ~1.6 eV for WSe2 and ~2.0 eV for WS2 monolayers with lateral variations that may arise from residual strain in the films. (Mo,W)S2 alloy growth using simultaneous flows of Mo and W hexacarbonyl precursors reveals evidence of atomic scale ordering of Mo and W atoms within the monolayer. Growth and characterization of MoS2/WS2 and WSe2/WS2 vertical heterostructures will also be discussed.
Investigation on Tunable Optical Properties and Structures of Graphene Quantum Dots Doped with Sulfur Heteroatoms
Authors: Feng Jianguang , Dong Hongzhou , Pang Beili , Yu Liyan , Dong Lifeng
Published: February 2020

Due to pronounced quantum confinement and edge effects, graphene quantum dots (GQDs) demonstrate numerous novel chemical and physical properties and thereby, have potential applications in optoelectronic devices, sensors and biomedical imaging. Doping GQDs with heteroatoms is an effective way to tailor their electronic and optical properties. However, due to different synthesis methods, the widespread use of GQDs doped with heteroatoms has been hindered by the poor understanding of their optical mechanisms. Recently, we studied optical properties of GQDs by employing theoretical calculations and experimental work, which demonstrated that theoretical studies can reveal optical mechanism of GQDs. In this work, the mechanisms underlying the tunable optical properties of GQDs doped with B and S are investigated using density functional theory and time-dependent density functional theory calculations. The electronic structures, optical spectra, molecular orbitals, and electronic density of GQDs are predicted to reveal electron transition processes. Especially, GQDs doped with different B and S patterns are designed to reveal the influence of the existence of O atoms on optical and electronic properties of GQDs. In general, electron-rich S atom increases the HOMO energy, while electron-deficient B atom lowers the LUMO energy, resulting in a decreased HOMO–LUMO gap. Edge doped effect analysis shows that B on GQDs induce a small red shift in absorption spectra whereas a large red shift occurs with surface doped GQDs. However, the absorption spectra of B and O co-doped GQDs exhibit an obvious blue shift and the absorption intensities enhance markedly. For S doped GQDs, the influences of surface and edge doping on absorption spectra of GQDs are almost opposite. Surface doped GQDs induces a small redshift in absorption spectra whereas a large redshift occurs with edge doped GQDs. The recombination of excited, well-separated electron hole pairs can result in enhanced absorption intensity. The heteroatoms doping on the basal plane can transform the sp2 hybridized carbon into the sp3 state. It is expected that this work will provide valuable knowledge for understanding and interpreting the electronic and optical properties of GQDs at atomic scale, and give important insights and guidance for the development of methods to controllably synthesize GQDs with well-defined and desirable properties towards specific purposes.
(Invited) Bottom-up Grown Nanowire Quantum Devices
Authors: Bakkers Erik P.A.M.
Published: February 2020

The main challenge for the development of a quantum computer is to solve decoherence. The promise of topological quantum computation is that local noise does not affect and destroy the quantum state, and therefore long coherence times are expected. In a topological system the quantum information is encoded in quasi particles, called Majorana Zero Modes (MZM).

First signatures of MZM have been obtained in InSb nanowires [1]. Recently, different schemes for performing logical operations and uncovering the properties of Majorana states are proposed. For such a universal computational architecture the realization of a near-perfect nanowire network assembly is needed in which Majorana states are coherently coupled.

Here, we demonstrate a generic process by which we can design any proposed braiding device by manipulating an InP substrate and thereby the nanowire growth position and orientation [2]. Our method leads to highly controlled growth of InSb nanowire networks with single crystalline wire-wire junctions. Additionally, nanowire “hashtag” structures are grown with a high yield and contacted. In these devices, the Aharonov–Bohm (AB) effect is observed, demonstrating phase coherent transport. These measurements reveal the high quality of these structures. Furthermore, this platform is used for in-situ epitaxial shadow growth of a superconductor on the nanowire facets, resulting in transport contacts. With this new generation devices we have observed quantized MZM [3].

Mourik et al., Science
2012, 336, 1003

Gazibegovic et al.
Nature 548 2017, 434

Zhang et al. Nature
2018
, accepted
Structural and Charging Stability of Metal Nanodot Memory in SiO2; First-Principles Study
Authors: Nakayama Takashi , Yamazaki Shota , Shiraishi Yuto
Published: February 2020

Due to the high charge-retention power, nanometer-scale metal dots are promising systems for near-future memory devices when they are embedded in insulating oxides such as SiO2. However, there exist serious issues of charge-retention degradation [1]; during the repeated charge injection, a metal nanodot is broken by the dissociation of metal atoms from the nanodot surface into insulator under the charge-induced electric field. In addition, the charge leakage from the metal nanodot to dissociated metal atoms decreases the charge-retention power of the metal nanodot. However, there have been no microscopic studies on how the metal nanodot is broken (structural stability) and how the charge-retention power decreases (charging stability). In this work, by the first-principles calculations, we answer these questions and clarify what kind of metal is suitable for a metal nanodot memory in SiO2.

Twenty kinds of metals are considered as candidate elements of metal nanodots. We calculate the dissociation energy of a metal atom from nanodot surface into amorphous SiO2 (a-SiO2) and clarify the structural stability [2]. On the other hand, the charge-retention power is estimated using the ionization energy of a dissociated metal atom in a-SiO2 [3]. Atomic and electronic structures of various metal atoms in a-SiO2 are calculated by the standard first-principles method using VASP code in the density-functional theory.

Main results are summarized as follows: (1) we found that the structural stability is determined by the competition between the metal-metal and metal-SiO2 interactions (bondings). For example, the Au and Ti nanodots are unstable because the Au-Au bonding is basically weak and the Ti-Ti bonding is weaker than Ti-SiO2 interaction, while the W nanodot is stable because the W-W bonding is much stronger than W-SiO2 bonding. It is shown that such strength of bonding reflects both the electron occupancy of d-orbital states and the electron negativity of metal atoms. (2) The degradation of charge-retention power occurs by the charge leakage from a metal nanodot to dissociated metal atoms. It is interesting to note that Ti and W dissociated atoms are difficult to be ionized positively although they have small electron negativity compared to Au. This is because these atoms are electronically bounded strongly to surrounding O and Si atoms in a-SiO2. As a result, the W and Ti nanodots show little charge-retention degradation. (3) From these considerations, we found that the W nanodot has the highest structural and charging stability, thus being suitable for a metal-nanodot memory usage.

These results are discussed in details, together with reviewing recent experiments and considering other degradation processes.

[1] M. S. Lee et al., Jpn. J. Appl. Phys. 46 (2007) 6202.

[2] R. Nagasawa, T.Nakayama et al., Jpn. J. Appl. Phys. 57 (2018) 04FB05.

[3] M. Y. Yang, T. Nakayama et al, J. Appl. Phys. 114 (2013) 063701.

Figure 1
(Invited) Unconventional Computing with Memristive Devices and Arrays
Authors: Li Can , Wang Zhongrui , Joshi Saumil , Upadhyay Navnidhi K. , Midya Rivu , Rao Mingyi , Xia Qiangfei , Yang J. Joshua
Published: February 2020

Memristive devices1 have become a promising candidate for unconventional computing2. In this talk, I will present some of our recent work on unconventional computing experimentally implemented by using memristive devices or crossbar arrays.

Using traditional non-volatile memristors with 64 stable analog resistance levels, we have built a dot-product engine based on a 128 x 64 1T1R crossbar array3. Accurate image compression and filtering have been demonstrated with such analog computing accelerator3. In addition, we have demonstrated efficient and self-adaptive in-situ learning in a two-layer neural networks using such memristive arrays4, which is expected to significantly improve the speed and energy efficiency of deep neural networks.

Using our newly developed diffusive memristors5 with diffusion dynamics that is critical for neuromorphic functions, we have developed artificial synapses6 and neurons7 to more faithfully emulate their bio-counterparts and more efficiently perform spiking neural network functions. We have further integrated these artificial synapses and neurons into a small neural network, with which pattern classification and unsupervised learning have been demonstrated7. Moreover, the diffusive memristors can be used as true random number generators8 for cybersecurity applications and artificial nociceptors for robotics applications9.

1. Yang, J. J. et al. Memristive switching mechanism for metal/oxide/metal nanodevices. Nature Nanotechnology
3, 429 (2008).

2. Yang, J. J., Strukov, D. B. & Stewart, D. R. Memristive devices for computing. Nature Nanotechnology
8, 13 (2013).

3. Li, C. et al. Analogue signal and image processing with large memristor crossbars. Nature Electronics
1, 52 (2018).

4. Li, C. et al. Efficient and self-adaptive in-situ learning in multilayer memristive neural networks. Nature communications, under revision (2018).

5. Midya, R. et al. Anatomy of Ag/Hafnia-Based Selectors with 1E10 Nonlinearity. Advanced Materials
29, 1604457 (2017).

6. Wang, Z. et al. Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing. Nature Materials
16, 101-108 (2017).

7. Wang, Z. et al. Fully memristive neural networks for pattern classification with unsupervised learning. Nature Electronics
1, 137 (2018).

8. Jiang, H. et al. A Novel True Random Number Generator Based on a Stochastic Diffusive Memristor. Nature communications
8, 882 (2017).

9. Yoon, J. H. et al. An artificial nociceptor based on a diffusive memristor. Nature Communications
9, 417 (2018).
Investigation on Amorphous Ga2O3 Based Conductive-Bridge Resistive Switching Memory with Low-Power, High-Speed, High Reliability
Authors: Gan Kai-Jhih , Liu Po-Tsun , Chien Ta-Chun , Li Zhen-Hao , Chiu Yu-Chuan , Ruan Dun-Bao , Sze Simon M.
Published: February 2020

In this work, Ga2O3 single layer serving as the resistive switching layer of a conductive bridge RAM device using a Cu-based supply layer was reported. Gallium oxide is a wide bandgap semiconductor with high dielectric constant and high breakdown voltages. By applying a Ga2O3 layer as the resistive switching layer, the excellent memory performances, such as low operation current (down to 100μA), notably high on/off resistance ratio (more than 105), and high switching endurance (>103 cycles) have been demonstrated in this study. Meanwhile, good stable retention property is also achieved (five decades of window margin are constantly maintained beyond 104 s at 85 ◦C). The novel Ga2O3-based CBRAM is a promising technology for potential future high density nonvolatile memory applications.
(Invited) Sputter Growth of Chalcogenide Superlattice Films for Future Phase Change Memory Application
Authors: Saito Yuta , Mitrofanov Kirill V , Makino Kotaro , Miyata Noriyuki , Fons Paul , Kolobov Alexander V. , Tominaga Junji
Published: February 2020

Ge-Sb-Te ternary alloys are key materials for phase-change random access memory (PCRAM). In PCRAM, data recording relies on reversible switching between amorphous and crystalline phases by electrical pulse induced Joule heating. We have proposed and developed GeTe/Sb2Te3 superlattice phase change memory, which is known as interfacial phase change memory (iPCM), and have demonstrated a significant reduction in switching energy and much longer endurance compared to conventional alloy-type phase change memory.

Since this superlattice is composed of atomically aligned GeTe and Sb2Te3 multilayers, fabricating a highly-oriented film is crucial. Furthermore, in order to utilize such material for novel devices in an industrial setting, reliable processes that allow large area deposition of uniform films is critical. Sputtering is one of the most useful, technologically friendly, and reliable methods for thin film fabrication. In this work, the growth mechanism of layered chalcogenide films is discussed.

The superlattice films were grown on various substrate materials by radio-frequency magnetron sputtering. Ge-Te and Sb-Te alloy targets were used. Before the growth of the film, Ar sputter cleaning was carried out to remove a native oxide from the substrate surface. An Sb2Te3 seed layer was grown initially at room temperature followed by alternate deposition of GeTe and Sb2Te3 layers at high temperature.

The crystal structure of the films as well as the degree of orientation were evaluated by x-ray diffraction (XRD) while the microstructure was observed by transmission electron microscopy (TEM). We found there is a strong dependency on substrate materials in terms of out-of-plane orientation of the superlattice film. On the basis of the obtained results, we will discuss the growth mechanisms of layered chalcogenide films and propose optimal growth conditions for future phase change memory applications.

This work was supported by JST-CREST (JPMJCR14F1).
(Keynote) MnPO4-Coating for Improved Long-Term Performance of Li(Ni0.4Co0.2Mn0.4)O2 in Ionic Liquid-Based Electrolytes
Authors: Chen Zhen , Kim Guk-Tae , Bresser Dominic , Jeong Sangsik , Copley Mark , Lin Janyi , Shen Zexiang , Passerini Stefano
Published: February 2020

MnPO4-coated LiNi0.4Co0.2Mn0.4O2 (MP-NCM) [1] is demonstrated to be a high performance lithium battery cathode material in combination with the room-temperature ionic liquid-based electrolyte consisting of LiTFSI-PYR14FSI (2:8 molar ratio). The MnPO4 coating acts as an ideal protective layer to physically prevent the contact between the NCM active material and the electrolyte, thus, successfully stabilizing the electrode/electrolyte interface and preventing detrimental side reactions even in conventional, carbonate-based electrolytes [2]. As a result, MP-NCM-based electrodes reveal greatly enhanced C rate capability and cycling stability – even under extreme conditions like extended operational potential windows, elevated temperature, and higher active material mass loadings. Employing an ionic liquid-based electrolyte allows for outstanding cycling stability of lab-scale pouch cells, offering a capacity retention of well above 85% after 2000 cycles. The superior electrochemical behavior of MP-NCM compared to as-synthesized NCM is assigned to the superior stability of the electrode/electrolyte interface and structural integrity when applying a MnPO4 coating, rendering this approach highly promising also for other state-of-the-art and next generation lithium battery cathodes.

References

[1] Z. Chen, D. Chao, J. Liu, M. Copley, J. Lin, Z. Shen, G.-T. Kim, S. Passerini, J. Mater. Chem. A, 5, 2017, 15669

[2] Z. Chen, G.-T. Kim, D. Bresser, T. Diemant, S. Jeong, M Copley, R. J. Behm, J. Lin, Z. Shen, Stefano Passerini, Energy & Environmental Science (2018) submitted
Development of Utility Friendly Olivine Based ESS in Esstalion Technologies – Part-2
Authors: Asakawa Yuichiro , Daigle Jean-Christophe , Zaghib Karim , Ueno Hiroshi
Published: February 2020

One of the promising approaches for striking a balance of realizing sustainable society and maximizing utility’s profit is to apply energy storage system (ESS). There’re many use cases proposed (1), such as reserve, regulation, peak shaving, time shift, load following, and renewable integration. To answer these demands, the development of a battery with high rate of charging and discharging, a longer cycle life and safe is imperative.

Esstalion Technologies Inc. has developed LFP LTO technologies with outstanding long life and excellent low temperature performance. (2) It is well know that material stability of LFP and LTO is key to those properties (3), however highly reactive surface of LTO causes undesirable reactions such as gas evolution (4). Those degradation modes hold back the possibilities of full utilization of material stability of LFP and LTO. We investigated mechanisms of failure modes at cathode and anode interfaces. Based the mechanisms, we overcome the issues, and found unique interface structure realizes the properties of our LFP LTO technology.

We propose a brief review of our technologies and we will show an example of our efforts to enhance the key properties of the Li-ion battery.

References

(1) Pacific Northwest National Laboratory, Protocol for Uniformly Measuring and Expressing the Performance of Energy Storage Systems

(2) Y. Asakawa et al., ECS Abstract MA2017-02 112

(3) K. Zaghib, M. Dontigny, A. Guerfi, P. Charest, I. Rodrigues, A. Mauger,

C.M. Julien, J. Power Sources 196 (8) (2011) 3949e3954.

(4) I. Belharouak et al., J. Electrochem. Soc. 2012 volume 159, issue 8, A1165-A1170
(Keynote) Ionic Liquid Electrolytes and Ionogel Composites that Enable High Capacity Anodes for Lithium and Sodium Batteries
Authors: Forsyth Maria , Howlett Patrick C , MacFarlane Douglas R. , Mecerreyes David , Girard Gaetan , Yunis Ruhamah , Armand Michel , Wang Xiaoen
Published: February 2020

With accelerating growth in demand for longer lasting, more durable and safer rechargeable energy storage technologies, it has become clear that we must find solutions to deliver these features while also using higher energy-density electrodes. As an anode material, graphite is limited in achieving high capacities due to its relatively low specific capacity of 372mAh/g. Li metal presents as an attractive alternative due to a ten-fold increase in specific capacity (3862mAh/g), while Na metal is nearly four times greater at 1166mAh/g. Electrolytes currently used for Li-ion and Na-ion devices are not compatible with these higher energy-density anodes. Instead we show that by using an ultra-high concentration of lithium or sodium salt in an ionic liquid we can facilitate stable cycling of Li metal and Na metal anodes, often at high rates and current densities, and even in the presence of water. These electrolytes indicate a decoupling of the alkali metal ion dynamics from the bulk with tLi+ or tNa+ transport numbers approaching 0.5. We will discuss the structure and transport in these superconcentrated IL systems and the importance of clustering and structural rearrangement in the transport mechanism of the alkali metal cation.

Polymerized ionic liquids, such as poly(diallyldimethylammonium) (PDADMA), with either TFSI or FSI counterions, are capable of dissolving even higher concentrations of lithium salt leading to highly conductive solid electrolytes. These materials have high tLi+ and improved mechanical properties and also enable stable Li metal cycling, thus offering exciting opportunities for all solid state lithium batteries. Interestingly, the nature of the counterion associated with the PIL has a significant impact on the compatibility with the IL electrolytes and on the resultant conductivity and mechanical properties. These materials will be discussed in terms of their phase behavior, conductivity and electrochemical behavior.
(Keynote) Redox-Active Polymeric Electrodes and Polymer Electrolytes
Authors: Sánchez Fontecoba Paula , Zhang Heng , Armand Michel , Rojo Teófilo
Published: February 2020

Electrochemical energy storage is one of the main societal challenges to human kind in this century. Among the myriad of energy-storage technologies, rechargeable batteries play a pivotal role because of their high specific energy and energy density. [1]

The evolution and development of rechargeable batteries have been tightly bonded to the research of polymeric materials, such as polymeric electrodes, polymer electrolytes, separators, binders, and so on. In particular, polymeric redox-active electrodes and polymer electrolytes have been emerging as promising candidates to substitute inorganic electrode materials and liquid electrolytes, respectively. This is because of the low cost of the precursors and the sustainability of their synthetic methods. Moreover, for polymeric materials, the existence of such a vast range of possible structures enables the proper tuning of structure-related properties according to the different requirements.

In the last few years, we have devoted continuous efforts on the research of polymeric redox-active electrodes and polymer electrolytes. We have conceived several novel concepts in these fields. In this talk, we will present an overview the development and our latest results on the polymeric redox-active electrodes, especially the family of poly-Schiff base/oligoether terpolymers. [2-4] In addition, highly conductive polymer electrolyte comprised of Jeffamine-based polymer matrices, [5] single ion conducting polysalts, [6] composite/hybrid solid polymer electrolytes, [7,8] novel additives for solid polymer electrolytes [9] will be also presented.

References

[1] M. Armand, and J.-M. Tarascon. Nature, 2008, 451, 652.

[2] M. López-Herraiz, E. Castillo-Martínez, J. Carretero-González, J. Carrasco, T. Rojo and M. Armand, Energy Environ. Sci., 2015, 8, 3233.

[3] E. Castillo-Martínez, J. Carretero-González, and M. Armand, Angew. Chem Int. Ed.,
2014, 53, 5341.

[4] N. Fernández, P. Sánchez-Fontecoba, E. Castillo-Martínez, J. Carretero-González, T. Rojo and M. Armand, ChemSusChem,
2018, 11, 311-319.

[5] I. Aldalur, H. Zhang, M. Piszcz, U. Oteo, L.M. Rodriguez-Martinez, D. Shanmukaraj, T. Rojo, and M. Armand, J. Power Sources, 2017, 347, 37.

[6] H. Zhang, C. Li, M. Piszcz, E. Coya, T. Rojo, L.M. Rodriguez-Martinez, M. Armand, and Z. Zhou, Chem. Soc. Rev., 46, 2017, 797.

[7] X. Judez, H. Zhang, C. Li, G.G. Eshetu, Y. Zhang, J.A. González-Marcos, M. Armand, and L.M. Rodriguez-Martinez, J. Phys.
Chem. Lett.,
2017, 8, 3473.

[8] N. Lago, O. Garcia-Calvo, J.M. Lopez del Amo, T. Rojo, M. Armand, ChemSusChem, 2015, 8, 3039.

[9] G.G. Eshetu, X. Judez, C. Li, O. Bondarchuk, L.M. Rodriguez-Martinez, H. Zhang, and M. Armand, Angew. Chem Int. Ed.,
2017, 56, 15368.
(Keynote) Redox-Active Organic Species for Rechargeable Batteries, and Beyond!
Authors: Poizot Philippe , Jouhara Alia , Deunf Elise , Dupré Nicolas , Guyomard Dominique , Dolhem Franck
Published: February 2020

Our entry into the Fourth industrial revolution since the turn of the century is set to revolutionize our daily life notably with the blooming of digital technologies such as communications, artificial intelligence, technologies related to the Internet of Things (IoT), 3-D printing or nano/bio-technologies. It is however hoped this new paradigm shift will integrate sustainable development goals and actions to address the critical damage caused by the previous industrial revolutions especially the threat of global warming. We have to be particularly aware there remains the urgent need for cleaner energy technologies which calls for a radical change in the energy mix to favour renewable energy and environmentally responsible energy storage solutions. To date, commercial batteries exclusively include inorganic electrode materials notably 3d transition-metals which are scarce, expensive and energy-greedy. In contrast, organic materials enable access to low cost and possibly greener compounds because composed of naturally abundant elements (i.e., C, H, O, N or S) moreover they are easier to recycle. In addition, they offer high structural designability through the well-established principles of organic chemistry and notably access to both n- and p-type electrochemical storage mechanisms making various cell or electrode configurations possible (Figure 1).

In 10 years, tremendous progress has been made to promote organic compounds in various rechargeable storage devices giving rise to nearly 15 published review articles especially for applications in non-aqueous (metallic) Li or Na-based batteries. However, several improvements are needed to further promote insertion organic electrode materials. For instance, only few studies have been reported in the literature regarding the assembly of full Li-ion organic cells while the literature is quite abundant in terms of Li metal-organic batteries; the main difficulty being to successfully synthesize robust lithiated cathode materials.

This contribution aims at reporting recent electrochemical data obtained with crystallized organic materials and explaining how it is possible to tune the electrochemical activity towards higher voltages depending on the molecular assembly and its electrostatic environment in Li enolate-based organic cathodes. In addition, a specific electrochemical study using soluble redox-active organic species will be reported providing to the Li battery community a supplementary proof concerning the high reactivity of the most popular supporting salt (i.e., LiPF6) versus any labile proton potentially present in a battery electrolyte.

Figure 1
A High-Voltage Aqueous Electrolyte for Sodium-Ion Batteries
Authors: Kühnel Ruben-Simon , Reber David , Battaglia Corsin
Published: February 2020

Aqueous sodium-ion batteries promise increased operational safety and lower cost compared to current state-of-the-art lithium-ion batteries based on organic electrolytes. For large-scale stationary systems, which find increasing application in the grid integration of electricity generated from intermittent renewable sources, these advantages of aqueous electrolyte batteries could translate into lower total-cost-of-ownership compared to organic electrolyte batteries. The major disadvantage of water as electrolyte solvent for batteries is its intrinsically narrow electrochemical stability window (thermodynamically only 1.23 V) limiting maximum cell voltage and consequently the battery’s energy density. We recently discovered an aqueous sodium-ion electrolyte system with a much enhanced electrochemical stability window. The wide stability window of 2.6 V for 35m aqueous NaFSI solutions broadens the choice of suitable active materials for aqueous sodium-ion batteries. We demonstrate stable cycling of a NaTi2(PO4)3 anode and a Na3(VOPO4)2F cathode in this aqueous electrolyte enabling the fabrication of high-voltage rechargeable aqueous sodium-ion batteries and discuss route to further increase the cell voltage.

R.-S. Kühnel, D. Reber, C. Battaglia, ACS Energy Letters 2017, 2, 2005
(Invited) Design, Analysis and Understanding of Electrochemical Interfaces for Energy Storage and Conversion
Authors: Strasser Peter
Published: February 2020

Electrochemistry and electrocatalysis play prominent roles in the science and technology of renewable electrical energy storage and conversion. Storage and conversion is put into effect via molecular bond making and breaking, catalyzed at electrified interfaces of an ion conductor and an electrocatalyst inside electrochemical reactors, such as Fuel Cells or Electrolyzers. For these reactions to occur with the smallest possible energy losses and the utmost atom efficiency, nanostructured multi-component electrode materials have proven indispensable, because they offer substantial advantages in atomic dispersion, often resulting in energy efficiency and performance benefits. What is more, electrocatalyst always undergo initial transient structural reorganization before their reactivity can fully unfold.

The successful development of novel nanostructured electrocatalyst materials requires molecular insights into their initial structural evolution (activation behaviour, active site/phase formation) as well as the relation between their atomic-scale structure and their catalytic performance. Unravelling these insights and relations is thus a scientific priority.

In this talk, I will highlight some of our recent work on the design and analysis of nanostructured electrocatalytic materials and their catalytically active liquid-solid interfaces. Examples will include new designs of and insights in noble and non-noble water splitting catalysts, oxygen reduction catalysts as well as CO2 reduction catalysts.
Electrochemical Synthesis of Cu-Cu2o-CNT/CNF Composite Coatings
Authors: Mech Krzysztof , Szacilowski Konrad
Published: February 2020

The main scientific objective of performed studies was development of methodology for electrochemical synthesis of ternary composite materials in the Cu-Cu2O-CNT/CNF systems (CNT – carbon nanotubes, CNF – carbon nanofibers). Copper is the only metal that exhibits very high selectivity for electrochemical conversion of CO2 to ethylene (1). Ren et al. observed similar effect in case of p-type Cu2O (2). Reported effects allows on assumption that combination of both materials can be great solution in the frame of light supported electrochemical conversion of carbon dioxide to ethylene. Additionally application of carbon structures: CNT or CNF as charge transfer mediators can limit photodegradation of Cu2O, improving simultaneously its chemical stability (3) and catalytic activity as well as selectivity for electrochemical conversion of CO2 to ethylene (2). Presence of highly hydrophobic CNT/CNF phase in Cu matrix may significantly improve selectivity through limiting adsorption of polar water molecules favoring simultaneously adsorption of nonpolar CO2 molecules.

Present studies describing optimization of electrochemical synthesis process towards synthesis of composite coatings of wide composition range. Synthesis conditions were investigated starting from thermodynamic analysis of the electrolyte. In next step, based on zeta potentials values stability of colloidal electrolyte containing carbon nanotubes was analyzed. Current-voltage conditions allowing on deposition of Cu with Cu2O with simultaneous incorporation of CNT/CNF structures were determined based on voltammetric and elctrogravimetric tests. Synthesized coatings were characterized towards their composition, structure and morphology.

References

Y. Kwon, Y. Lum, E. L. Clark, J. W. Ager and A. T. Bell, ChemElectroChem, 3, 1012 (2016).

D. Ren, Y. Deng, A. D. Handoko, C. S. Chen, S. Malkhandi and B. S. Yeo, ACS Catalysis, 5, 2814 (2015).

P. D. Tran, S. K. Batabyal, S. S. Pramana, J. Barber, L. H. Wong and S. C. J. Loo, Nanoscale, 4, 3875 (2012).
Preparation of n-MoS2 for HER Using a High Voltage Electrochemical Deposition Method
Authors: Kim Seong-Hoon , Iqbal Muhammad Ibrahim , Abbas Syed Asad , Jung Kwang-Deog
Published: February 2020

Recently, MoS2 has attracted attention as a HER (hydrogen evolution reaction) catalyst for replacing Pt, because it has similar hydrogen bonidng energy to Pt. Here, a HVER (high-voltage electrochemical reduction) method in a H-cell was attempted to prepare nanosized MoS2 on graphene. A Pt wire was used as a cathode to reduce (NH4)2MoS4 to MoS2 on the graphene particles dispersed in water and a potential of 60 V was applied to the cell and a varible resistor was adjusted to allow a current of 50 mA to flow. During the electrochemical reduction, no Mo deposition on the Pt cathode was observed and MoS2/graphene particles were simply obtained with a short preparation time of less than 15 min. Fig.1 shows LSV of MoS2/rGO synthesized at the diffierent reduction time with a RDE and EIS Nyquist plots corresponding to the LSV. The MoS2/rGO sample prepared at the reduction time of 10 min exhibited the highest current density of 37.6 mA/cm2 at the overpotential of 200 mV. EIS analysis showed that the MoS2/rGO sample (10 min) has the lowest charge transfer resistance of 25 Ω. Particle sizes of the prepared MoS2 were observed with TEM analysis. The particle size of MoS2 (10 min) was in the range of 4-10 nm. The particle size of MoS2 increased with increasing the electroreduction time. It was reported that the smaller the particle size of MoS2, the higher the HER activity.1) So, one reason for the decrease in the activity of the sample prepared at a reduction time of more than 10 minutes is because the particle size of MoS2 increases as the electrochemical reduction time increases. XRD diffraction patterns of the prepared samples showed that the prepared MoS2 samples had three phase of 1T (tegragonal), 2H (hexagonal) and 3R (rhombohedral) and the 3R phase was mainly observed. The MoS2 has been prepared in a hydrothermal method for HER, which shows mainly 2H phase. Recently, it was suggested that 3R phase of MoS2 outperformed the corresponding 2H phase for hydrogen evolution.2) In that aspect, it is proposed that the HVER method is a promising technique for producing high activity MoS2 catalysts.

References

[1] L. Lei, Z. Jie, B. Xiaojun, Z. Lina, D. Micheal, G.H. Scanlon, L. Baohong, Adv. Funct. Mater., 23, 5326 (2013). [2] T.J. Rou, S. Zdenek, L. Jan, S. David, P. Martin, ChemComm, 53, 3054 (2017)

Figure 1
Pulse Electrodeposition of Copper Octahedrons: Investigations into the CO2RR on These Surfaces
Authors: Rashid Nusrat , Ingole Pravin popinand
Published: February 2020

A well-tamed energy conversion strategy for the valorization of CO2 is a necessity for maintaining a check on CO2 levels (~ 500ppm) and borrow enough time for the scientific community to perfect zero-emission fuel prospects. Mimicking photosynthetically fixed CO2 by plants in an electrochemical cell is both scientifically intriguing and sociologically promising- given more than half of world still runs on fossil fuel derived energy and standard of life are determined by the intake of energy. Catalysing CO2RR with economical, selective heterogeneous metal nano-structures proved a promising way to improve upon the status quo.

We synthesised copper octahedrons by two electrode electrodeposition, to selectively reduce CO2RR into CO2+H2 (synthesis gas) to use it as starting material in well known Fischer-tropsch reaction. In a representative experiment, copper was dissolved from a sacrificial copper anode and collected as micro-octahedrons on the surface of a platinum foil. The structures were simply tapped off the surface, cleaned, dried and used as catalyst ink to reduce CO2 into value-added fuels. A set of experimental parameters were varied to study the effect of them on morphology, size and activity of the obtained copper powders. A pulse method involving anodic and cathodic waves passed through the copper anode was found to have a determining capability - be it shape, topology or size of the crystallites.

In a catholyte composed of 0.2 M KHCO3, cyclo-voltammograms (CVs) were recorded in N2 saturated and CO2 catholyte in a 3-electrode, 2-chambered cell. From preliminary results, it was shown that CuOcta showed activity towards CO2RR as was evident in enhanced faradaic response in CO2 saturated catholyte. To confirm the path of fixing and valorization, a thorough gas chromatography (GC) analysis was done on the gases that were collected in a Tedlar bag. CO was found to be major reduction product in gaseous phase overcoming the inherit HER (hydrogen evolution reaction) competition on metal surfaces. A significant amount of CH4 was also measured. The array of obtained products signal role of morphology, the surface topography of catalytic structures on the mechanism and kinetics of CO2RR.

Figure 1
Structural Evolution of Lithium Metal Electrodeposited on Copper
Authors: Steingart Daniel A
Published: February 2020

The secondary lithium metal negative electrode is regarded as the “end point” in closed form electrochemical energy systems. The inherent instability of the lithium metal interface against any known electrolyte and current collector makes any resultant passivation layer and alloys a critical aspect of the electrodeposition, and stripping, of the metal in addition to standard electrochemical determinants of plate metal morphology. In this presentation we present the conditions that result in a columnar morphology of lithium grown atop copper films, as well as the electrochemical behavior of this morphology as compared to standard foil lithiums.