bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Domino Killing Isomerization of Azobenzene Embedded in Rigid Polymer Gel
Authors: Watanabe Toshiyuki , Matsumoto Masaya , Karube Tamami , Isozaki Masatsugu , Misawa Kazuhiko
Published: February 2020

Photoisomerization reactions of azobenzene derivatives have become the most common power source for molecular machines and photoresponsive polymers. Among photomechanical polymeric materials, a large response has been achieved exclusively using azobenzene-containing liquidcrystalline elastomers (azo-LCEs) and networks (azo-LCNs). Thus, although a number of efforts have been done to develop polymeric materials capable of transducing light to mechanical work, successful examples of bottom-up direct photomechanical transduction are still limited. Here we demonstrate that azobenzene containing rigid polymer networks, which consist of aromatic poly(amide acid) or polyimide backbones, show remarkable macroscopic deformation in response to blue (405 nm) and visible light (>532 nm) irradiation.

The bending motion of the cantilever was recorded by a video camera and analyzed on a computer. Although, the centimeter-long cantilever of PAA gel rapidly bends and forms a 90° angle within 4 s upon 405nm laser irradiation at one point, that of PI gels deflect 90 degree within 1.5 s. The bent cantilever cannot smoothly return to a straight shape upon visible light (> 532 nm) irradiation at one point. Surprisingly, in order to return the polymer rod of PI gels to the upright state, it is necessary to irradiate the entire rod with visible light. We believe that this is because trans-cis isomerization of azobenzene at the light irradiation site induces domino killing isomerization of the polymer gel at the non-irradiated site. In this research, we discuss the possibility that domino killing isomerization of azobenzene is induced by laser irradiation from various evidence.
(Invited) Toward “Infinite Origami” Polymer
Authors: Ochiai Bungo
Published: February 2020

This paper describes development of a foldable and shape-memory polymer toward “infinite origami” based on synergy of morphological, sacrificial, and chemical cross-linkages. The basis of the topological cross-linkage is a cyclopolymerization of a bisacrylate monomer forming 19-membered rings. Radical copolymerization of the bisacrylate, acrylonitrile, and 2-ethylexylacrylate in the presence of axis polymers bearing PEG repeating units gave transparent films. The Young’s modulus of a film is as high as 200 MPa, while the film is foldable below Tg. The cyclopolymerization is accompanied by inclusion of the axis polymers forming topological cross-linkages for ductility. The nature of the initial hardness is the dipolar-dipolar interaction of the nitrile groups cross-linking the polymer chains physically and reversibly. The physical cross-linkage may be sacrificially broken to lose energy for fracture, while can be regenerated after heating.

Figure 1
(Invited) Bioinspired Multi-Scale Pores and Channels
Authors: Hou Xu
Published: February 2020

"Pores" and "Channels" are everywhere, e.g, from small biological ion channels to large oil pipelines. Pores and channels can be distinguished by the relationship between their diameter and their depth. If the diameter is greater than the depth, the system is treated as pore, otherwise, channel. However, for established porous materials, including membranes, no such strict definition is used. Both, “Pores” and “Channels” have a wide range of significant applications in different scales. Good examples of microscale channels can be found in microfluidics, which has rapidly increasing impact in the areas of chemical synthesis, biomolecule and cell analysis, micro- and nanofabrication, and information technology, etc. With regard to the nanoscale, the nanochannels which led to the birth of a whole new area of research, can be used for nanofluidics, gas separation and storage, batteries, water purification, energy harvest or DNA sorting. In the past, such multiscale pores and channels systems have been intensively explored and contributed to new developments in materials science, in membrane science and technology, or in micro/nanotechnology for analytical, biomedical or information processing applications. Stimulated by the achievements and the even larger potential of multiscale pores and channels systems, increasing research activities are devoted to important aspects such as energy saving, anti-fouling, anti-corrosion, and anti-blocking functionalities, switchability and controllability integration of various different functionalities, and good stability in such confined space. Our research mainly focuses on bioinspired and smart multiscale pore/channel systems, membrane science and technology, microfluidics, interfacial science, physical chemistry, electrochemistry, nano/micro fabrication for energy-saving and biomedical applications.

Recent Publications:

ACS Nano 2018, 12 (2): 908-911;

Nature Communications 2018, 9 (1): 733;

Science Advances 2018, 4 (2): eaao6724;

Small 2018, 1703283;

Small 2018, 1702170;

Nature Reviews Materials 2017, 2: 17016;

Advanced Materials 2016, 28: 7049-7064;

Nature 2015, 519 (7541): 70-73;

CRC Press USA (Book, 2016, ISBN: 978-1-4987-2248-3);

Nano Today 2018 DOI:10.1016/j.nantod.2018.04.006.
(Invited) Self-Assembly Synthesis and Interfacial Control of Electrode Architectures
Authors: Dai Sheng
Published: February 2020

Enhancement in electrochemical energy storage resides in tailored nanotextures resulting from making electrode materials hierarchically nanoporous. The complex interplay of solvent and solute structure and dynamics at the charged interface, the transport of electrolyte ions into and out of the pores, the solvation/desolvation processes occurring in pores approaching bare-ion dimensions, and formation of interfaces via chemical reactions are all important parameters. Herein, several self-assembly synthesis methods for carbon and oxide composites as electrode materials for energy storage will be discussed. The objective of this talk is to demonstrate that mesoporous carbons and oxides derived from soft-template synthesis not only entail a high storage capacity but also, most importantly, can be made through self-assembly synthesis to have a significantly enhanced electronic conductivity and storage capacity. This enhanced electronic conductivity in 3D architectures is the key to providing high rate capability for the corresponding energy storage systems.
Random Heterogeneous Microstructure Construction of Composites By Fractal Geometry
Authors: Guo Zhansheng , Wang Siwen
Published: February 2020

The microstructures of composite determine its macroscopic properties. In this work, microstructures included arbitrary shapes and sizes of particles are constructed by several developed fractal geometry algorithms based on MATLAB. A two dimensional (2D) quadrilateral fractal geometry algorithm is developed based on modified Sierpinski carpet algorithm. Square, rectangle, circle, and ellipse based microstructure constructions are a special case of 2D quadrilateral fractal geometry algorithm. Moreover, a three dimensional (3D) random hexahedron geometry algorithm is developed according to Menger sponge algorithm. Cubes and spheres based microstructure constructions are a special case of 3D hexahedron fractal geometry algorithm. The polydispersities of fractal shapes and the random fractal sub-units are two significant advantages compared with their original algorithms. In addition, we can combine the different algorithm randomly according to the real microstructure. These algorithms open up new opportunities for microstructure construction which can be imbedded commercial finite element method software.
Electrocatalytic Hydrogenation of Biogenic Molecules: Understanding Reactivity Trends
Authors: Gutiérrez Tinoco Oliver Y , Sanyal Udishnu , Meyer Laura C , Camaioni Donald M , Lopez Ruiz Juan A , Holladay Jamelyn , Lercher Johannes A
Published: February 2020

The interest in storing electrical energy into chemical bonds has increased due to the increasing availability of sustainable electricity and its intermittent character. A promising approach is to couple electrolytic H2 production with transformations of organic compounds to chemicals and fuels. Thus, electrocatalytic hydrogenation (ECH) of phenolic compounds, di-aryl ethers and aromatic aldehydes, has been performed on Pt, Pd, Rh, and Ni supported on the working carbon electrodes of H electrolysis cells. At these conditions, H2 evolution (HER) is the prevalent side reaction, thus we define efficiency as the fraction of current used to reduce the organic compounds.

The electrocatalytic hydrogenation of phenolic compounds and aromatic aldehydes readily occur on Pt and Rh, whereas Pd is highly efficient for reduction of aldehydes (Figure 1). The rates of ECH and HER increase with increasingly negative potentials but the efficiency is a strong function of the metal (e.g., Pt and Ni strongly favor HER).

In the conversion of phenolic compounds and ethers, the dominant reaction pathway is hydrogenation to the corresponding alcohols and cycloalkyl ethers. Ether bonds undergo C-O bond cleavage (mainly via hydrogenolysis), which opens pathways to the formation of hydrocarbons. In contrast, aromatic and aldehydes and ketones undergo only reduction of the carbonyl groups without exhibiting any hydrogenation of the aromatic ring. Acidic media accelerates the rates of reduction and enables C-O bond cleavage of alcohols through a bifunctional (acid-metal) mechanism.

We have further studied the effect of solvents in continuous flow systems. Similar to batch H-cells, the aromatic aldehydes are quantitatively converted to aromatic alcohols (Figure 1). The reactivity of these carbonyl compounds is strongly affected by decreasing polarity of the reaction media due to solvation effects. HER is less affected than ECH by increasing the C number of the co-solvent alcohol from methanol to i-propanol. This effect can be compensated by increasing cell potentials (see Figure 1 for the ECH of acetophenone) and the concentration of the reactant.

This study shows that electrocatalysis drives the desired transformations at mild conditions and allows a better control over the reaction pathways than thermal catalysis. Cathodic potentials leads to high rates through increasing the availability of surface H and by providing alternative pathways with low-energy barriers.

Figure 1
Bifunctional Electrocatalytic Properties of Na2MPO4f (M: Fe, Mn, Co) for Na-Air Batteries
Authors: Sharma Lalit , Barpanda Prabeer
Published: February 2020

Metal-air batteries with high-energy density (~5200 Wh kg-1) based on O2-H2O based chemistry are of great interest for the battery community. The performance of air-battery in non-aqueous electrolyte is affected due to the formation of insoluble discharge product. Hence, hybrid aqueous air batteries are garnering more interest as the discharge product is soluble. However, air batteries function on two processes namely oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Kinetics of both ORR/OER processes are too slow hence, a catalyst is required to increase the rate of reaction. Existing catalysts are costly and lacks bifunctional nature. Motivated by recent reports of various phosphate based materials having electrocatalytic activity, we hereby report the electrocatalytic activity of Na2MPO4F (M: Fe, Mn, Co) family. All materials were synthesized via solution combustion route resulting in carbon-coated grains. This carbon coating not only increased the conductivity of the sample but also improve the catalytic properties. All three materials were found to be acting as a bifunctional catalyst with Na2CoPO4F standing out among all three. [Figure 1] The onset potential of Na2CoPO4F was found to be 0.854 V vs. RHE for ORR process, which is comparable to 20% Pt/C. An onset potential of 1.591 V vs. RHE was recorded for OER process. It was used as a cathode to fabricate hybrid Na-air battery and a roundtrip efficiency of 88% was recorded for over 30 cycles. The catalytic properties of all three materials were also studied theoretically by density functional theory (DFT) analysis. The structural and catalytic analysis of the family will be presented.

Figure 1: Linear sweep voltammetry plots of Fe, Mn and Co-based fluorophosphtes recorded at 1600 rpm in 0.1 M NaOH electrolyte showing their bifunctional nature.

Figure 1
Cu2s As a Superior Anode for Sodium-Ion Batteries
Authors: Cai Jiyu , Meng Xiangbo
Published: February 2020

There has been an ever-increasing demand on renewable clean energies (e.g., solar energy and wind energy), given the facts that fossil fuels (i.e., petroleum, coal, and natural gas) are depleting and causing environmental issues. Because of their intermittent operations, however, these renewable clean energies rely on large-scale electrical energy storage (EES) systems to realize their wide implementation in the grids. To this end, sodium-ion batteries (SIBs) have been highly regarded as the promising EES candidates, due to their low cost and natural abundance. One of the biggest challenges for SIBs lies in developing high-performance anodes [1-3] that enable high capacity and long-term stable cyclability. In this regard, conversion-based materials (e.g., metal oxides and metal sulfides) hold great promise, but have not been well explored. In this context, we recently investigated copper sulfide (Cu2S) as a high-performance anode for SIBs. Our study revealed that Cu2S could achieve a sustainable capacity of ~300 mAh/g. In addition, our study also demonstrated that Cu2S could realize high rate capability up to 10 C and long-term cyclability. In the study, we characterized Cu2S as a new anode using galvanostatic cycling, cyclic voltammetry, electrochemical impedance spectroscopy, high-magnification scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. This study provides an in-depth understanding on Cu­2S electrochemistry in SIBs.

Meng, X., Atomic-scale surface modifications and novel electrode designs for high-performance sodium-ion batteries via atomic layer deposition. Journal of Materials Chemistry A, 2017. 5: p. 10127-10149.

Li, L., et al., Recent progress on sodium ion batteries: potential high-performance anodes. Energy & Environmental Science, 2018. 11(9): p. 2310-2340.

Luo, W., et al., Na-Ion Battery Anodes: Materials and Electrochemistry. Accounts of Chemical Research, 2016. 49(2): p. 231-240.

Figure 1
The Fundamental Mechanism behind the Stability of Li Metal Anodes in Non-Aqueous Electrolytes
Authors: Zhang Ji-Guang , Cao Xia , Ren Xiaodi , Xu Wu
Published: February 2020

A stable and high efficiency Li metal anode (LMA) is critical rechargeable Li metal batteries (LMBs), including the batteries with various cathodes such as ion intercalation compounds and conversion materials (such as sulfur and oxygen). An ideal metal anode not only needs to have a very high Coulombic efficiency (CE), but also need to have a low concentration, high conductivity and low cost. [1-2]

During the last a few years, various methods have been used to prevent dendrite growth and improve CE of LMA, including used of high concentration electrolytes (HCEs) Localized High-Concentration Electrolytes (LHCE) by diluting HCEs with electrochemically “inert” solvents or poorly solvating diluents. [3] However, the fundamental mechanism behind the stability of LMA in non-aqueous electrolyte is still not well understood. This work will report our recent investigations on the interaction between LMA and various non-aqueous electrolytes. Although LMA is kinetically unstable with non-aqueous electroltye, appropriate selection of non-aqueous electrolyte, including both salt and solvent will enable formation of a more stable SEI layer on LMA surface and largely minimize the side reaction between LMA and electrolyte, therefore enable a dynamically stable LMA for long term cycling of li metal batteries. Several high performance electrolytes that are stable at ~4.5V with a CE of more than 99.2% have enabled long term cycling of LMBs and will also be reported in this work.

S. Whittingham, "History, Evolution, and Future Status of Energy Storage", proceedings of the IEEE(Volume: 100, Issue: Special Centennial Issue , May 13 2012).

-G. Zhang, W. Xu and W. A., Henderson, Lithium Metal Anode and Rechargeable Li Metal Batteries. (Springer International Publishing), 249, (2017).

Shuru Chen, Jianming Zheng, Donghai Mei, Kee Sung Han, Mark H. Engelhard, Wengao Zhao, Wu Xu, Jun Liu and Ji-Guang Zhang,” Mater.
2018, 30, 1706102.
Revealing the Atomic Origin of Heterogeneous Li-Ion Diffusion By Probing Na
Authors: Xiao Biwei , Wang Kuan , Xu Gui-Liang , Song Junhua , Chen Zonghai , Amine Khalil , Reed David , Sui Manling , Sprenkle Vincent , Ren Yang , Yan Pengfei , Li Xiaolin
Published: February 2020

The ion diffusion process, shuttling of Li and Na-ions in and out of the host electrode materials is the basis on which Li-ion batteries (LIBs) and Na-ion batteries (SIBs) operate.[1] Its reversibility and the governing kinetics dictate many of the battery performance parameters such as cycling stability and rate capability.[2] However, it is challenging to understand the ion diffusion process at the atomic level for manipulation in practical rechargeable batteries.[3]

Tracing the dynamic process of Li-ion transport at the atomic scale is a long-cherished wish in solid state ionics and essential for battery material engineering. Approaches via phase change, strain, and valence states of redox species are developed to circumvent the technical challenge of direct imaging Li, however, all are limited by poor spatial resolution and weak correlation with state-of-charge (SOC). Here, we adopt an ion-exchange approach by sodiating the de-lithiated cathode and probing Na distribution to trace the Li de-intercalation, which enables us to visualize the heterogeneous Li-ion diffusion down to atomic level through the utilization of techniques such as scanning transmission electron microscopy - high angle annular dark field (STEM-HAADF) imaging. In the model LiNi1/3Mn1/3Co1/3O2 cathode, dislocation-mediated ion diffusion is kinetically favorable at low SOC and planar diffusion along (003) layers dominates at high SOC, which work synergistically to determine the ion diffusion dynamics. Our work unveils the heterogeneous nature of ion diffusion in battery material and stresses the role of defect engineering in tailoring ion transport kinetics.[4]

References

[1] J. B. Goodenough, Y. Kim, Chem. Mater., 2010, 22, 587

[2] M. S. Whittingham, Chem. Rev., 2004, 104, 4271.

[3] T. Shang and H. Li et al., Adv. Energy Mater. 2017, 7, 1700709.

[4] B. Xiao and X. Li et al., submitted.

Figure 1
Electrochemical Properties of Zr4+ Doped LiFePO4 cathode Material for Li-Ion Battery
Authors: Ellinwood Clayton , Zavala Caleb , Carson Oliver , Fang Hui
Published: February 2020

Due to its thermal stability, low cost and high theoretical charge capacity, LiFePO4has emerged as one of the most promising cathode materials for large-scale lithium ion batteries. In this study, we systematically investigated the effect on structure and electrochemical properties brought by Zr doping on Fe site of LiFePO4. LiFe1−yZryPO4 (y = 0, 0.01, 0.02, 0.03, 0.05, 0.07, and 0.1) samples were prepared by using solid-state reaction. The phase and structure of as prepared powders were characterized by X-ray diffraction. Cycling charge and discharge measurement at various C-rates was employed to reveal the electrochemical properties. Results showed that the sample with 1% Zr doping was observed to have the highest charge capacity at various rates.
Characterization of Limiting Factors in All-Solid-State Lithium Batteries Using an Embedded Reference Electrode
Authors: Lim Hyung-Tae , Chang Gi Hwan , Choi Han Ul , Kang Sung
Published: February 2020

Three-electrode system has been universally utilized in lithium ion batteries to understand the reaction mechanism of working electrodes during charge-discharge process. However, it cannot be readily applied in all-solid-sate batteries (ASSBs) due to the practical constraints to the selection and placement of reference electrode in solid electrolyte. Herein, we investigated factors influencing capacity fade in ASSBs consisting of Li2S-P2S5 solid electrolyte, Li4.4Si anode and TiS2 cathode, with embedded reference (In) electrode. Ohmic resistance (R0), charge transfer resistance (Rct) and polarization resistance (Rp) were determined for each electrode, using three electrode setup. The first discharge process was dominated by the low lithium diffusion coefficient in TiS2. The first charge capacity was significantly reduced due to sluggish kinetics of alloying process, which sequentially affected the next cycle performance. The results indicate that alloying process is a critical step to determine the performance of ASSBs consisting of alloy electrode.
Comparative Analysis on Deactivation of Redox Mediators in Li-O2 Battery
Authors: Kim Hun , Nguyen Trung Thien , Sun Yang-Kook
Published: February 2020

To address the high overvoltage issues on charging in Li-O2 batteries, many kinds of redox mediators (RMs) have been studied. However, researches on the problems of RMs in these systems are insufficient. We compare herein effects and problems of RMs in Li-O2 batteries by applying unique methodology, based on two types of cells, comparison between argon and oxygen atmospheres and combining electrochemistry in conjunction with spectroscopy. Using systematic electrochemical measurements, representative RMs in Li-O2 battery prototypes were thoroughly explored with respect to oxygen presence, voltage ranges and scan rates. By this comparative, multi-parameters study we reached valuable insights. We identified possible routes for RMs degradation in Li-O2 batteries related to the cathode side, using bi-compartments cells with solid electrolyte that blocks the crossover between the cathode and the Li metal sides. Based on comparative research, we confirmed that degradation of the RMs activity was caused by intrinsic decomposition of the RMs in the electrolyte solution at the cathode part, even before further reactions with reduced oxygen species. This work provides a realistic view of the role of important RMs in Li-O2 batteries and suggests guidelines for selecting suitable RMs, mandatory additive in Li-O2 batteries electrolyte.
Study on Degradation of Microstructure in Ni-Rich Li[NixCoyMn1−x−Y]O2 (x = 0.8, 0.9) Cathodes from Accelerated Calendar Aging
Authors: Ryu Hoon-Hee , Park Kang-Joon , Kim Un-Hyuck , Kim Jae-Hyung , Sun Yang-Kook
Published: February 2020

Lithium-Ion batteries (LIBs) based on layered transition-metal oxides, Li[Ni
x
Co
y
Mn1
−

x

−

y
]O2 (NCM), have long been considered as an alternative cathode for EVs and the main strategy for increasing the discharge capacity of NCM cathodes has been a progressive increase of the Ni fraction.1,2 However, the large-sized LIBs for EV require not only high energy density, but also longer operation lifetimes and improved safety for more than 10 years. Because an EV is intermittently used, it typically remains stationary for long periods in the fully charged state. Therefore, calendar aging is expected to significantly affect the lifetimes of EVs, similar to cyclic aging. The most common degradations observed from calendar aging in low-Ni NCMs are mainly from the gradual loss of active Li as identified by most researchers.3 However, for Ni-rich NCM materials with high energy densities but poor structural stability originating from phase transitions, the degradation mechanism during calendar aging is still poorly understood.

In this study, we investigated the deterioration of Ni-rich NCM (Ni = 80 %, and 90 %) cathode materials under severe storage conditions.4 To mimic parking conditions for EVs, we performed accelerated calendar aging tests and focused on the consequential structural degradation of the cathode materials upon electrolyte contact.

References

S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett.
2017, 2, 196.

D.-W. Jun, C. S. Yoon, U.-H. Kim, Y.-K. Sun, Chem. Mater.
2017, 29, 5048-5052.

S. Käbitz, J. B. Gerschler, M. Ecker, Y. Yurdagel, B. Emmermacher, D. Andre, T. Mitsch, D. U. Sauer, J. Power Sources
2013, 239, 572.

H.-H. Ryu, G.-T. Park, C. S. Yoon, Y.-K. Sun, Small
2018, 14, 1803179.
(Invited) Electrolytes for Wide-Temperature Application Range of Lithium Ion Batteries
Authors: Liu Bin , Li Qiuyan , Engelhard Mark H , He Yang , Wang Chongmin , Xu Wu
Published: February 2020

The electrolyte often dominates the temperature range within which lithium (Li) ion batteries (LIBs) operate, thus developing new class of electrolytes in LIBs for wide temperature applications especially at low temperature environment will be quite essential for further development of LIBs. In this study, after a lot of electrolyte screening work, we developed new optimized electrolytes containing multiple functional additives to enable the LIBs to perform well in a wide temperature range. Importantly, those cells based on the above optimized electrolytes have been proven to behave significantly enhancement in discharging performance at −40°C, the long-term cycling stability at 25°C (more than 85% of capacity retention after 1000 cycles at 1C/1C rates), as well as the obviously improved cycling stability at 60°C. These remarkable results indicate that the optimized electrolytes with multiple additives are worth considering for further development of LIBs in wide-temperature application range. Some underlying mechanisms behind the high-performance battery electrolytes have been investigated and will be presented at the meeting. Our finding on the new functional electrolytes would favorably widen the working temperature range of future LIBs, especially for electric vehicles at low temperatures.

Acknowledgement

This work was supported by the Technology Commercialization Fund program, Office of Technology Transitions, of the U. S. Department of Energy (DOE).
CuCl2-Based Cathode Material with Incombustible Inorganic Liquid Electrolyte Towards Room-Temperature Na Rechargeable Battery
Authors: Jung Hojae , Kim Ayoung , Lee Jiwhan , Jeong Goojin , Kim Young-Jun , Kim Hansu
Published: February 2020

Na rechargeable batteries have gained much attention as an alternative power sources of Li rechargeable batteries. Nevertheless, further advance on Na rechargeable batteries is necessary, to compete in rechargeable battery market because of their low energy density and reliability. Here, we demonstrate a new type of room temperature Na rechargeable battery which employs CuCl2/C nanocomposite cathode material and SO2-based inorganic liquid electrolyte. A high discharge capacity of 200 mAh g−1 corresponding to theoretical energy density of 580 Wh kg−1 is achieved, and also a high round-trip energy efficiency (>96%) and excellent cycle-life over 1000 cycles, which has never been obtained in conventional organic electrolyte system. The remarkable electrochemical performance is mainly attributed to the use of the non-flammable SO2-based electrolyte, which guarantees a reversible conversion reaction between CuCl2 and CuCl with NaCl. Further, detailed reaction mechanism of the new battery system will be discussed in the presentation.
Enhancing the Performance of Li-S Batteries with LaLiO2-Based Multifunctional Interlayer
Authors: Bizuneh Girum G. , Fan Jingmin , Sun Cui , Xiangfei Yuan , Xue Fei , Deng Dingrong , Lei Jie , Lin Xiaodong , Jia Yueju , Yang Jingfang , Yan Han , Wang Xueyin , Zheng Mingsen , Dong Quanfeng
Published: February 2020

The Li-S batteries are the future promising energy devices. However, the polysulfide diffusion and the lethargic kinetics of sulfur are the prominent bottle necks. Consequently, commercialization of the Li-S batteries for practical application is dragged back. In this work, multifunctional interlayer composed of Lanthanum lithium oxide is designed and tested. With this design we could obtain multifunctional interlayer combined sulfur cathode by coating of Lanthanum lithium oxide on as-fabricated cathode. The multifunctional interlayer with the striking features of good electronic and ionic conductivity as well as effective polysulfide trap resulted in boosted performance of Li-S batteries. The modified cathode with expanded sulfur could deliver 1458.00 mA h g-1 capacity at initial cycle and 1004.40 mA h g-1 during the first cycle at 1C rate with superb cycling stability up to 250th cycle offering the corresponding residual discharge capacity of 872.79 mA h g-1 in Li-S batteries. And, the rate performance has been improved by the facile strategy.
Unraveling the Origin of Performance Degradation in High-Capacity Cation-Disordered Oxide Cathodes
Authors: Chen Dongchang , Chen Guoying
Published: February 2020

Due to the substantial energy gap between state-of-the-art cathodes and anodes, development of new-generation Li ion batteries (LIBs) critically depends on cathode material discovery and improvement. In recent years, a combination of reversible redox activities of both transition-metal cations and oxygen anions were found to be feasible in a number of transition-metal (TM) oxides, such as the layered Li- and Mn-rich, lithium nickel manganese cobalt oxides (LMR-NMCs) and Li-rich rock-salt compounds. Such combination allows a significant enhancement in the charge storage capacity of LIB cathodes. However, challenges exist in these LIB cathodes with both cationic and anionic redox activities. After extensive cycling, performance issues such as capacity fade, voltage decay, hysteresis, and impedance rise often occur. Understanding the chemical origin of these issues in LMR-NMC has been on-going for well over a decade. Various degradation mechanisms, such as TM migrations, have been proposed. However, the effect of oxygen redox in cation-disordered cathode is largely unknown.

In this work, we performed detailed studies on one of the most promising cation-disordered rock-salt cathodes, Li1.3Nb0.3Mn0.4O2 (LNMO). Systematic evaluation on the electrochemical behavior as a function of oxygen redox revealed that the performance deterioration is directly correlated to the extent of oxygen redox involvement. On the fundamental side, we performed a series of hard and soft X-ray absorption spectroscopic (XAS) studies to analyze the changes in Mn and oxygen activities due to cycling, and illustrated the chemical and structural origin for the observed voltage decay and capacity fade. It was found that electrochemical cycling with large contribution of oxygen redox significantly decrease the redox activity of oxygen itself as well as Mn redox activity. In contrast to what was reported on layered LMR oxides, extensive TM reduction was observed but phase transition resulting from cation site migration was not detected in the cycled oxide. A densification/degradation mechanism was proposed accordingly which elucidates how a unique combination of extensive chemical reduction of TM and reduced quality of the Li percolation network in cation-disordered rock-salts can lead to performance degradation in these newer cathodes with 3-dimentional Li migration pathways. On the basis of these studies, cation site chemistry of Li-Nb-Mn rock salt system was systematically tailored to tune the contribution of oxygen redox. Opportunities in balancing capacity and cycling stability will be discussed.
Improved Electrochemical Performance of Al2O3-Coated LiNi0.6Mn0.2Co0.2O2 Cathodes By Atomic Layer Deposition
Authors: Wang Xin , Cai Jiyu , Li Jianlin , Meng Xiangbo
Published: February 2020

There has been an ever-increasing need on high-energy and cost-effective lithium-ion batteries (LIBs) in order to power future transportation. In this context, LiNi1-x-yMnxCoyO2 (NMC) cathodes are particularly attractive, due to their reduced cost and higher capacity compared to the traditional LiCoO2 cathodes [1]. Among the NMC cathodes, nickel-rich LiNi0.6Co0.2Mn0.2O2 (NMC622) is one of the most promising cathode materials undergoing intensive investigation, but suffers from a series of technical issues, such as dissolution of metal elements, oxygen evolution, and structural instability [2]. Aimed at addressing these issues, we recently applied Al2O3 coatings on NCM622 using atomic layer deposition (ALD). Unlike others did, we coated the cathode directly and it revealed that the ALD Al2O3 coatings enable improving the cyclability and sustainable capacity of the NMC622 cathodes at different cutoff voltages of 4.3 – 4.7 V. In the study, we investigated the effects of ALD Al2O3 coatings using X-ray diffraction, X-ray photoelectron spectroscopy, impedance spectroscopy, scanning electron microscopy, and transmission electron microscopy. Our study demonstrated that ALD remains an important measure to tackle technical issues in LIBs [3].

Manthiram, A., B. Song, and W. Li, A perspective on nickel-rich layered oxide cathodes for lithium-ion batteries. Energy Storage Materials, 2017. 6: p. 125-139.

Hou, P., et al., Surface/Interfacial Structure and Chemistry of High-Energy Nickel-Rich Layered Oxide Cathodes: Advances and Perspectives. Small, 2017. 13(45): p. 1701802.

Meng, X., X.-Q. Yang, and X. Sun, Emerging applications of atomic layer deposition for lithium-ion battery studies. Advanced Materials, 2012. 24(27): p. 3589-3615.

Figure 1
Mechanism Explaining the Onset of Dendritic Li Electrodeposition Via Considerations of Li-Ion Transport within the SEI Layer
Authors: Maraschky Adam , Akolkar Rohan
Published: February 2020

High-energy density batteries are critically needed to power future electric vehicles. One major hurdle for rechargeable energy-dense Li-metal batteries is the dendritic electrodeposition of Li during the battery charging process. In this contribution, we report on our investigations of the onset time for dendritic growth during galvanostatic Li electrodeposition. Using electrochemical techniques combined with optical microscopy, we show that Li dendrites initiate at a time when the surface overpotential during galvanostatic electrodeposition reaches a maximum value. This observation is explained using an analytical transport model wherein the Li+ concentration within the solid electrolyte interphase (SEI) at the Li–SEI interface decreases gradually as the SEI thickens and its transport resistance increases with time. At the dendrite onset time (τonset), the Li+ concentration at the Li–SEI interface approaches zero – a condition under which surface roughness on the Li electrode amplifies, producing dendrites. Once dendrites form, they rupture the SEI, lowering the surface resistance for plating. Model predictions of how τonset varies with current density and soak time are shown to be in qualitative agreement with experimental observations. Pulsed currents are applied to mitigate Li+ concentration depletion within the SEI, thereby delaying or preventing altogether the formation of dendrites. The effect of temperature on τonset is also investigated and this temperature-dependence is discussed in the framework of the aforementioned transport model.
Transition Metal Cations Stabilized Layered Vanadate Cathodes for Zinc-Ion Batteries
Authors: Liu Chaofeng , Cao Guozhong
Published: February 2020

A general strategy is explored to design and synthesize a series of layered vanadate hydrates. Structural analysis found a small amount of cations entered into the VO layers to form a chemical bonding and lock the layer slabs with a stable structure. The stabilized vanadate hydrates have the expanded layer spacing and the robust layered structures that provide a fast ion migration channel and stand the volume change in the intercalation/de-intercalation of Zinc-ion during the electrochemical reaction, rendering an excellent rate capability and stable cycling performance. Specifically, Mn-stabilized vanadium pentoxide hydrate delivers a specific capacity of 400 mAh/g at a current density of 50 mA/g and 260 mAh/g at 4 A/g with capacity retention of 92% over 2,000 cycles. Several transition metal cations can also play the same role in enhancing Zn-ion storage in layered vanadate hydrates, suggesting a general strategy for exploiting the high-performances cathodes for multi-valent ion batteries.
High Energy Density Flexible Battery with Self-Standing Binder- and Collector-Free Electrodes
Authors: Kuznetsov Oleg A. , Pigos Elena , Chen Gugang , Harutyunyan Avetik R
Published: February 2020

Rapid development and miniaturization of portable and wearable electronic require compact powering devices with highest possible energy density combined with mechanical flexibility. Li-ion batteries remain most practical energy storage devices. Their energy density can be increased by removing electrochemically dead components such as metal collector foils, binder and additives. We developed novel self-standing collector-, and binder-free electrodes produced by a mixing of battery active materials with as-grown carbon nanotubes in a gas-phase. Resulted composite sheets consisting of the particles of the active material imbedded in the 3-dimentional network of pristine carbon nanotubes. The method allow exploiting particles/flakes of any active materials. Electrodes grown by this method can be up to 2 mm thick and have up to 25 mAh/cm2 areal capacity density (in case of NMC 5:2:3 active cathode material). Electrodes are flexible and stretchable in a wide range of compositions, allowing fabrication of flexible battery cells. Since metal collector foils are not present, the electrodes are naturally two-sided, simplifying manufacturing of stacked cells. Batteries that exploit the electrodes fabricated by this method can power flexible electronics.
High Ionic Conductivity in 2D Molybdenum Disulfide (MoS2) Membrane
Authors: Park Juhong , Choi Wonbong
Published: February 2020

Two-dimensional transition metal dichalcogenides (2D TMDs) have a variety of advantages for nanoelectronics, photonics, and opto-electronics due to their unique electrical and optical properties including the band gap modulation with film thickness. 2D TMDs film reveals layered structures with weak van der Waals forces between each neighboring layer and large specific surface area owing to sheet-like structure, which are distinct properties making 2D TMDs highly attractive for capacitive energy storage. Other layered materials, such as graphene oxide and boron nitride, have been well studied as membrane separation for nanofluidic device applications, but the property of ionic transport through 2D molybdenum disulfide (MoS2) has not revealed yet. Here we fabricated few-layer MoS2 nanosheets and measured ionic currents with a variety of hydroxide solutions (LiOH, NaOH, and KOH). The activation energies and ionic conductivities of the solutions are practically calculated, and several orders of magnitude higher ionic conductivity compared to the bulk are measured at low concentration of the solutions. The detail of mechanistic understanding of the ionic conductivity in 2D MoS2 will be discussed.
(Invited) Atomically-Informed Phase-field Modeling of Li and Mg Electrodeposition Morphologies
Authors: Liu Zhe , Li Yunsong , Yao Yan , Chen Long-Qing , Qi Yue
Published: February 2020

Exploring the origin of non-dendritic Mg electrodeposition might provide a new prospect of realizing the Li metal anode application in next-generation batteries. To fundamentally understand the morphological difference between Li and Mg plating, we hereby developed a multiscale model for a general metal electrodeposition process based on the phase-field method and transition state theory, connecting the atomic level charge-transfer physics to the mesoscale morphological evolution. At the atomic level, density functional theory (DFT) based half-cell calculations were used to predict the interfacial structures, de-solvation processes and Li+/Mg2+ ion energy landscapes at Li/SEI/ethylene carbonate (EC)-electrolyte and Mg/ tetrahydrofuran(THF)-electrolyte, and the effects of electric field on them. With thermodynamic and kinetic parametric inputs from DFT calculation (i.e. interfacial energy and anisotropy of Li/SEI (Li2CO3), surface energy and anisotropy of Mg, diffusion coefficient of Li+ in SEI (Li2CO3), and relative difference in charge-transfer energy barrier of Li/Mg plating), our non-linear phase-field model captures the morphological evolution difference between dendritic Li plating and faceted Mg plating. Furthermore, through systematical parametric analyses, we conclude that the cation desolvation-induced exchange current difference between Li and Mg is mainly responsible for their deposition morphological differences. This study provides a strategy of connecting the phase-field method and atomistic calculations and sheds lights on the dendrite-free battery anode design.
(Invited) Exploring Fuel Cell Catalyst Layers at Multiple Scales
Authors: Zawodzinski Thomas A. , Subbaraman Ram , Sun Che-Nan , Cantillo Nelly M.
Published: February 2020

The catalyst layer used in a fuel cell is an archetype of multi-component composite materials used as electrodes in many electrochemical devices. In this talk, we will describe and link together a number of studies of the fuel cell catalyst layer that we have been carried out over the past 10 to 15 years. The first of these was a modeling effort that was initially carried out to describe the geometrically constrained limits on utilization of dispersed catalyst in the layer. To answer our original question, the catalyst components were broken down to constituents (Pt nanoparticles, carbon particles, ionomer) and interactions between components were used to build a hierarchical model of the catalyst layer. The interactions were defined in the context of colloidal interaction theory using descriptions of electronic properties of the constituents derived from experimental measurements of refractive index/dielectric properties across a wide range of frequencies. The model satisfactorily captured some aspects of the structure of the catalyst layer, e.g. the tendency toward segregation of components, and provides a good bound to the utilization of catalysts but failed to provide a quantitatively accurate description of certain transport-related physical properties. In the next phase of the work, the connectivity of ionomer in the catalyst layer was probed using NMR relaxation and diffusion measurements on water in the catalyst layer as a function of water content. Finally, a detailed study of the distribution of components within the catalyst layer, the catalyst layer porosity and the adsorption of ionomer in catalyst layers, all as functions of composition, was undertaken. These three chapters of work correspond to three different probes usng models and experiments of many types to yield a more nuanced picture of the catalyst layer. Future prospects and needs will be presented in the context of still-missing information and where we might look for it.

Acknowledgement

We gratefully acknowledge the support of this work by the US Army Research Office and the Naval Research Research Office. The significant contributions of Professor J. Adin Mann of Case Western Reserve university and Dr. Karren More of Oak Ridge National Lab are also appreciated.
Comsol Simulation of Hierarchical Ordered Porous Microstructure Electrode
Authors: Azami-Ghadkolai Milad , Creager Stephen E , Bordia Rajendra
Published: February 2020

High specific energy is always desirable in battery systems, especially for electric vehicles. A key towards improving specific energy for a particular combination of anode and cathode active material is to maximize the mass fraction of active material, which means minimizing the fraction of inactive material such as the separator, the binder, electrode additives for improving electronic conductivity, and the current collector. A seemingly simple strategy for maximizing the mass fraction of active materials is to make the electrodes as thick as possible. However, ion transport in thick electrodes can be particularly problematic since salt diffusion into and through the electrode pore space is slow and can easily limit the battery charge / discharge rate.

An ideal microstructure is one that allows for direct line of sight or path for the electrode active material access to the electrolyte, for rapid ion-transport throughout the entire electrode thickness. Therefore, a need exists for electrode fabrication methods that create microstructures that maximize electrolyte transport, as is needed to achieve high-rate charging/discharging in electrodes having high mass loading. Optimal microstructures in electrodes help to achieve the ideal balance of active material and electrolyte mass to give high gravimetric and volumetric energy density.

As to design a microstructure with the goal of Li ion salt transport facilitation, we synthesized ordered porous microstructure electrodes using combination of freeze cast and tape cast techniques. This method enjoys the combination of conventional tape casting, a main technique in manufacturing Li ion electrodes in industrial scale, and freeze casting.

This study simulate two dimensional ordered porous electrode cross-sections and presents the electrochemical performance results of Mo-doped LTO in a electrochemical cell consist of a lithium metal anode, polymer separator, and liquid ethylene carbonate and ethyl methyl carbonate electrolyte. The electrochemical performance of ordered porous microstructure is investigated by varying electronic conductivity, tortuosity, particle size, electrode thickness, and C rate.

We show that these engineered porous electrodes considerably reduces the electrolytes mass transport limitation and electrochemical response of electrode is independent of tortuosity, making it possible to synthesize ultra thick electrode for high energy and power density applications.

Simulation results show that 10 micron thickness of wall and pore freeze tape cast Mo-doped LTO with electronic conductivity of 1 S/m, tortuosity as high as 10, electrode thickness of 458 micron and mass loading of 30 mg/cm^2 can deliver full capacity even at 2 C-rate.