bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Pseudocapacitive Energy Storage Using 2D Nanomaterialsunder Extreme Conditions
Authors: Park Ho Seok
Published: December 2020

With increasing demand for high performance energy storage devices, the feasibility of reliable and functional energy storage devices that well operates under extreme conditions is of prime importance for expanding applicative fields as well as for understanding materials’ intrinsic and extrinsic properties and device physics.1-4 In this talk, I will introduce the control in the physical structure and chemical composition of 2D nanomaterials for ultracapacitive energy storage devices under limited circumstances, where conditions are classified into thermodynamic (e.g. pressure, volume and temperature) and kinetic (e.g. high rate and frequency) variables.1-10 In addition, a fundamental foundation via in-situ spectroscopic techniques will be presented to understand charge storage phenomenon of new materials and devices occurring on a nanoscale under various circumstances.8-10

Reference

[1] Ho Seok Park*, et al. Adv. Energy Mater., 2015, 1500959.

[2] Ho Seok Park*, et al. ACS Nano., 2015, 9, 8569-8577.

[3] Ho Seok Park*, et al. Adv. Funct. Mater., 2015, 25, 1053-1062.

[4] Ho Seok Park*, et al. ACS Nano, 2011, 5, 5167-5174.

[5] Ho Seok Park*, et al. Nano Lett., 2015, 15 (4), 2269-2277.

[6] Ho Seok Park*, et al. Adv. Energy Mater., 2016, 6, 1501115.

[7] Ho Seok Park*, et al. Adv. Energy Mater.,
2018, 8, 1702930.

[8] Ho Seok Park*, et al. ACS Energy Lett., 2018, 3, 724.

[9] Ho Seok Park*, et al. Joule, 2019, 3, 1-13.

[10] Ho Seok Park*, et al. Nature Materials,
2019, 18, 156-162.
Understanding Cell Degradation As a Function of Fast Charging
Authors: Raj Abhishek , Rodrigues Marco-Tulio , Abraham Daniel P.
Published: December 2020

The results of this work aim to inform development of charging protocols that are less damaging to cell health. To that end, degradation during fast charging is observed through capacity limited charging with rates ranging from 1C to 8C and SOCs ranging from 10-100%. This test matrix probes various failure modes including metallic deposition of lithium at the anode, continued formation of SEI, and full cell impedance rise. Reference electrode testing and harvested electrodes transferred to half cells are used in order to deconvolute these degradation modes.

Through these experiments, we find that impedance rise is a function of charging rate alone and not on the amount of capacity passed at each cycle. Accordingly, limiting charging to a narrow SOC can delay cell aging, but not prevent eventual degradation. Particle cracking in the cathode is identified as the likely mechanism for impedance rise, supporting the notion that electrode design is essential to enabling fast charging.
Reversible Capacity Losses in LiFePO4 / Graphite Cells
Authors: Spingler Franz B. , Naumann Maik , Jossen Andreas
Published: December 2020

This investigation focuses on significant capacity losses that have been found to occur in commercial lithium-iron phosphate (LFP) / graphite cells after repeated shallow cycling around medium states of charge (SOCs). Many combinations of cycle depth, medium SOC and temperature are examined over up to 10,000 full cycle equivalents. Up to 1000 full cycle equivalents, the capacity loss rate is four times higher when the cells are cycled between 40% and 60% state of charge than it is with full cycles. It is shown that these extraordinary losses occur in three different lithium-iron phosphate / graphite cell models, two 26650-type and one 18650-type, but do not occur in a nickel-manganese-oxide / graphite 18650-type cell. Most of the apparently lost capacity is shown to be recoverable by holding the cells at either 0 % or 100 % state of charge over a period of several days. Differential voltage analysis and visual post-mortem inspection as well as coin cell experiments with harvested electrode material suggest that these capacity losses are caused by strongly non-uniform lithium distributions in the electrodes. Hypothetical mechanisms are presented and discussed that could lead to such non-uniform distributions of lithium forming preferentially in lithium-iron phosphate based cells. The findings presented in this study are believed to be particularly relevant for grid applications like primary control reserve or in other scenarios where the battery mainly serves as a peak power buffer, e. g. in hybrid drivetrains.

The graph shows the capacity evolution of LFP / graphite cells cycled with full cycles and with 20 % cycle depth around three different medium SOCs. Capacity loss is largest when cycling between 40 % and 60 % SOC. The photographs show post-mortem views of the graphite anodes of three different LFP / graphite cell models that were cycled using this procedure until reaching ca. 80 % remaining capacity. Gold colored stripes at the top and the bottom of the electrodes indicate a non-uniform distribution of intercalated lithium.

Figure 1
Hierarchical Nanoneedles Grown on Nickel Foam As Binder-Free Electrode for High Energy Density Asymmetric Supercapacitors
Authors: Jadhav Vijaykumar
Published: December 2020

Hierarchical chestnut-like manganese cobalt oxide (MnCo2O4) nanoneedles (NNs) are successfully grown on nickel foam using a facile and cost-effective hydrothermal method. High resolution TEM image further verifies that the chestnut-like MnCo2O4 structure is assembled by numerous 1D MnCo2O4 nanoneedles, which are formed by numerous interconnected MnCo2O4 nanoparticles with grain diameter of ∼10 nm. The MnCo2O4 electrode exhibits high specific capacitance of 1535 F g−1 at 1 A g−1 and good rate capability (950 F g−1 at 10 A g−1) in a 6 M KOH electrolyte. An asymmetric supercapacitor is fabricated using MnCo2O4 NNs on Ni foam (MnCo2O4 NNs/NF) as the positive electrode and graphene/NF as the negative electrode. The device shows an operation voltage of 1.5 V and delivers a high energy density of ∼60.4 Wh kg−1 at a power density of ∼375 W kg−1. Moreover, the device exhibits an excellent cycling stability of 94.3% capacitance retention after 12000 cycles at 30 A g−1. This work demonstrates that hierarchical chestnut-like MnCo2O4 NNs could be a promising electrode for the high performance energy storage devices.
Surface-Redox Features of Molecular-Level Controlled 2D Oxidized Black Phosphorus
Authors: Nakhanivej Puritut , Jung Mingyu , Park Ho Seok
Published: December 2020

Two-dimensional (2D) nanomaterials have gained much attention for energy applications over other dimensional materials due to their unique atomic orientation and physiochemistry, which allows fully utilization of exposed surface. Here, we highlight the importance of surface-redox features on 2D oxidized black phosphorus (oBP) surface chemically coupled with percolated graphene. The redox-active oxidized P sites and strong covalent bonds between oBP and graphene play the pivotal role for highly efficient energy storage. The interplay of oxidized P sites on the surface and strong interlayer coupling at heterointerface on the unique charge storage mechanism were investigated by several in-situ spectroscopic techniques and computational method along with electrochemical performance of hybrid cell.
Electrochemical Fluorination of Organic Compounds Using Alkali Metal Fluoride Salt with Fluorinated Alcohol-Based Solvent System
Authors: Shida Naoki , Takenaka Hiroaki , Gotou Akihiro , Isogai Tomohiro , Yamauchi Akiyoshi , Fuchigami Toshio , Inagi Shinsuke
Published: December 2020

Fluorinated alcohols, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE), are quite useful in organic chemistry including electrosynthesis, due to their unique features such as high oxidation tolerance, high polarity, low nucleophilicity and strong donor ability in hydrogen bonding. Fluorinated alcohols are also capable of dissolving alkali metal salt such as KF and CsF, which is one of the least expensive fluoride ion sources, in high concentration. In this research, we report the electrochemical fluorination of various organic compounds using alkali metal fluoride salt dissolved in a mixed solvent containing HFIP for the first time. Alkali metal fluorides acted both as a fluoride ion source and a supporting electrolyte to enable the electrochemical fluorination of C-H and C-S bonds efficiently.
Electrochemical Synthesis of Fused Indole Alkaloids By Controlling Radical Cation Reactivities
Authors: Okamoto Kazuhiro , Chiba Kazuhiro
Published: December 2020

Pyrrolophenanthridone alkaloids are isolated from Amaryllidaceae and it has fused N-benzoyl indole as core structure. Many researchers targeted this simple alkaloids to demonstrate various synthetic method1), such as palladium- or hypervalent iodine-mediated intramolecular cross-coupling, tetrazine-promoted inverse electron-demand Diels-Alder reaction. All examples required DDQ oxidation to convert indoline to indole.

We established metal- and oxidant-free electrochemical intramolecular C(sp2)-H cross-coupling and indole synthesis reaction. These reactions were initiated by same anodic oxidation for electron-rich indoline ring, but different electron-transfer pathway was occurred in both cyclization and indole forming reaction. Moreover, non-coordinative medium has crucial role to control reactivity of radical cation. Increasing electrophilicity of radical cation is key strategy to accomplish intramolecular cross-coupling. MeNO2-LiClO4 and HFIP (1,1,1,3,3,3,-hexafluoro-2-propanol), which known as suitable medium for radical cation-mediated reaction2), had not worked well for this reaction. However, MeNO2-HFIP (9:1) mixed solvent strongly enhanced the reactivity of radical cations. This phenomenon was occurred by synergetic stabilization effect of MeNO2 and HFIP3). The low donor number of MeNO2 and anion trapping ability of HFIP made non-coordinative environment and resulting electrophilic radical cation was maintained in this medium. Dehydrogenative indole forming reaction was accomplished in Lewis-basic condition (MeCN-Bu4NClO4), and collidine additive enhanced benzylic deprotonation from radical cation.

Finally, we applied both reactions for the synthesis of seven naturally occurred pyrrolophenanthridone alkaloids4).

References

(1) (a) Black, DC.; Keller, PA.; Kumar, N. Tetrahedron Lett.
1989, 30, 5807-5808; (b) Ganton, MD.; Kerr, MA. Org. Lett.
2005, 21, 4777-4779; (c) Boger, DL.; Wolkenberg, SE. J. Org. Chem.
2000, 65, 9120-9124.

(2) (a) Okada, Y.; Chiba, K. Chem. Rev.
2018, 118, 4592-4630; (b) Kirste, A.; Nieger, M.; Malkowsky, IM.; Stecker, F.; Fisher, A.; Waldvogel, SR. Chem. Eur. J.
2009, 15, 2273-2277.

(3) (a) Shida, N.; Imada, Y.; Nagahara, S.; Okada, Y.; Chiba, K. Commun. Chem.
2019, 2, 24; (b) Shida, N.; Imada, Y.; Okada, Y.; Chiba, K. Eur. J. Org. Chem.
2020, 2020, 570-574.

(4) Okamoto, K.; Chiba, K. Org. Lett.
2020, accepted (DOI: 10.1021/acs.orglett.0c01082).

Figure 1
Biphasic Bioelectrocatalytic Synthesis of Chiral β-Hydroxy Nitriles
Authors: Dong Fangyuan , Chen Hui , Minteer Shelley D.
Published: December 2020

Two obstacles limit the application of oxidoreductase-based asymmetric synthesis. One is the consumption of high stoichiometric amounts of reduced equivalent. The other is the low solubility of organic substrates, intermediates, and products in the aqueous phase. In order to address the two obstacles of oxidoreductase-based asymmetric synthesis, a biphasic bioelectrocatalytic system was constructed and applied.. In this study, the preparation of chiral β-hydroxy nitriles catalyzed by alcohol dehydrogenase (AdhS) and halohydrin dehalogenase (HHDH) was investigated as a high-value organic product. Diaphorase (DH) was immobilized by cobaltocene-modified poly(allylamine) redox polymer on the electrode surface (DH/Cc-PAA bioelectrode) to realize the effective bioelectrocatalytic NADH regeneration. AdhS is a NAD-dependent dehydrogenase, so the diaphorase modified biocathode was used to regenerate NADH to support the conversion from ethyl 4-chloroacetoacetate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by AdhS. The addition of methyl tert-butyl ether (MTBE) as organic phase not only increased the uploading of COBE, but also prevented the spontaneous hydrolysis of COBE and extended the lifetime of DH/Cc-PAA bioelectrode, and finally increased the Faradaic efficiency and the concentration of generated (R)-ethyl-4-cyano-3-hydroxybutyrate ((R)-CHCN). After 10 hours of reaction, the highest concentration of (R)-CHCN in biphasic bioelectrocatalytic system achieve 25.5 mM with 81.2% enantiomeric excess (ee
p). The conversion ratio of COBE achieved 85%, which was 8.8 times higher than that of single phase system. Besides COBE, the other two substrates with aromatic ring structures were also used in this biphasic bioelectrocatalytic system to prepare corresponding chiral β-hydroxy nitriles. The results indicate that the biphasic bioelectrocatalytic system has the potential to produce a variety of β-hydroxy nitriles with different structures.
(Invited) Split G-quadruplex-based Strategy for Sensitive Detection of Pathogenic Bacteria
Authors: Park Ki Soo
Published: December 2020

In this talk, I will introduce a simple, sequence-specific DNA detection method, utilizing a fluorescent 2-aminopurine (2-AP) nucleobase analogue-containing split G-quadruplex as the key detection component. In the sensor, the 2-AP-containing G-quadruplex is split into two segments and linked to a target-specific overhang sequence. The separate G-quadruplex sequences form an active G-quadruplex structure only in the presence of a complementary target DNA, which leads to a significant increase in the intensity of fluorescence from the 2-AP fluorophore. This simple, one-step, homogenous assay was successfully employed to detect target DNA with a high selectivity. In addition, the practical applicability of the detection method was demonstrated by its use in analyzing target DNAs in human serum. To the best of our knowledge, this is the first time that an investigation was carried out in which a fluorescent nucleobase analogue was incorporated into a split G-quadruplex structure and this structure was utilized as the foundation for a specific DNA sensor.
Elucidating the Mechanism behind the Bionanomanufacturing of Gold Nanoparticles Using Bacillus Subtilis
Authors: Lim Koun , Macazo Florika , Scholes Connor , Chen Hui , Sumampong Kirsten , Minteer Shelley D.
Published: December 2020

Precious metal nanoparticles, such as gold, silver, and platinum, have opened up numerous research opportunities in pharmaceuticals, medical, optical and electronic fields thanks to their unusual size-dependent properties. Thus, bionanomanufacturing of nanoparticles, using biological entities at ambient pressure and temperature, has shown promising synthesis routes to control size and morphology for industrial applications. However, the exact mechanism of how ions get reduced to stable nanoparticles has not been fully investigated, hindering researchers from optimizing the process and possibly applications in bioelectrochemical synthesis of nanoparticles. Thus, we focused on elucidating the mechanism of the extracellular bionanomanufacturing of gold nanoparticles using the cell extract of Bacillus subtilis. The suspect gold reducing protein, catalase A (cat A), was engineered into E.Coli for overexpression. The recombinant cat A was exposed to multiple experimental parameters such as solvents, additives, temperature and pH. Commercially available catalase from the bovine liver was also used to compare the bionanomanufacturing process, assessing the possible gold reduction via the catalytic active site. The bionanomanufactured gold nanoparticles were characterized via UV-VIS, TEM, and XPS. The deduced mechanism is a combination of non-catalytic activity of sulfur-containing amino acids to initiate the gold ion reduction and the denatured enzyme working as a capping agent to stabilize nanoparticles.

Figure 1
Evaluation of Matching Ratio Impact on Reduced Charging Time
Authors: Yourey William , Fu Yanbao , Li Ning , Battaglia Vincent , Tong Wei
Published: December 2020

As electric vehicles (EV) show an increased penetration into the transportation market, a challenging hurdle to overcome is a vehicle “refuel” time similar to that of refilling a gasoline vehicle tank. One pathway to accomplish this is fast charging lithium-ion cells. The majority of commercial Li-Ion cells manufactured today contain various positive electrode active materials, coupled with a graphite negative electrode. An advantage of graphite electrodes is that the lithiated graphite voltage lies close to that of Li/Li+, resulting in in increased cell voltage. This benefit also has a detrimental effect on fast charging cells with graphite electrodes, where a small polarization of the negative electrode can result in a condition favorable to lithium metal plating on the negative graphite electrodes1.

While modified high rate charging procedures for commercial lithium-ion cells with conventional graphite negative electrodes, such as multistage constant current charging and boost charging, have been implemented. These procedures rely on reducing charging currents when cell voltage limits are reached 2,3. Following the development of an accelerated charging procedure based solely on negative electrode lithiation rate and polarization 4, the presented work evaluates the effect of negative to positive (N:P) matching ratio on cell fast charge performance. Two varying N:P matching ratios of 1.2:1 and 1.7:1 are evaluated and the resulted impact on fast charge performance will be presented. Utilizing an accelerated charging procedure based solely on the limiting negative electrode results in an identical charging procedure being used for multiple cell designs when charging to the same degree of negative electrode lithiation. Theoretically the applied procedure should result in a reduction in recharge time to 80% state of charge from 58 minutes to 34 minutes by altering the cell N:P ratio. Actual cell performance is altered as increased irreversible capacity loss occurs in cells with increased N:P rations, but improvements in cell charge times can be accomplished from design changes, namely cell N:P ratios.

References

C. Uhlmann, J. Illig, M. Ender, R. Schuster, and E. Ivers-Tiffée, Journal of Power Sources, 279, 428–438 (2015).

D. Anseán et al., Journal of Power Sources, 321, 201–209 (2016).

P. H. L. Notten, J. H. G. O. het Veld, and J. R. G. van Beek, Journal of Power Sources, 145, 89–94 (2005).

W. Yourey, Y. Fu, N. Li, V. Battaglia, and W. Tong, J. Electrochem. Soc., 166, A1432–A1438 (2019).
Morphology Evolution in Sodium Metal Electrodes
Authors: Sarkar Susmita , Mukherjee Partha P.
Published: December 2020

Uncontrolled dendrite growth leading to electrical short-circuits, poor recharging capability, and other safety concerns, currently delegate the feasibility of commercial utilization of sodium metal batteries. Dendrites are needle-like growths that appear on the surface of the negative electrode during the electrochemical cycling of a battery. As the fundamental knowledge in intrinsic plating/striping process of sodium metal can guide us for designing a better and safe system, here, we have thoroughly investigated the deposition and dissolution process with the aid of electrochemical analytical methods and imaging techniques using Na|Na or Na|Cu cells as exemplar systems. Engineering a separator with respectable mechanical strength to accommodate electrode volume changes and good electrolyte wettability to retain sufficient absorbed electrolyte in the interface is necessary for stabilizing the metal deposition and improving the overall battery response. Herein, different types of separators were used to understand how the separators guide the homogeneous/inhomogeneous deposition of sodium during the cycling process. The detailed knowledge in the nucleation and growth of sodium metal can provide insights into engineering a sodium cell with controlled Na growth and higher cycling stability.
Resistivity of Mesopore Confined Solvent Free Ionic Liquid Determined By Electrochemical Impedance Spectroscopy
Authors: Scisco Gibson Paul , Orazem Mark E. , Jones Kevin S. , Ziegler Kirk J.
Published: December 2020

Supercapacitors offer higher power delivery and near infinite cycle stability compared to Li-ion batteries, but they lag behind in terms of energy density. Research into improving the energy density of supercapacitors has recently been focused on the rational design of nanopore structure to balance highly energy dense micropores (<2 nm) with higher conductivity mesopores (2 – 50 nm). Replacing aqueous electrolytes with organic electrolytes such as ionic liquids (ILs) can also dramatically increase energy density by enabling voltages higher than 1.23 V. ILs can have electrochemical stability windows as high as 3 – 6 V. Experiments with single conical nanopores have shown drastic increases in resistivity for imidazolium based ILs in very small pores, but a return to bulk resistivity for pores above 20 nm in diameter. Here, we report a 5-fold increase in resistivity of 1-ethyl,3-methylimidazolium tetrafluoroborate (EMIM-BF4) IL confined in carbon nanopores of diameter 24.4 ± 4.6 nm, well into the mesopore regime. Resistivity was determined through the use of detailed analysis of electrochemical impedance spectroscopy measurements of working supercapacitors of varying pore length. By utilizing highly ordered carbon electrodes based on the anodized aluminum oxide template growth method, this analysis offers insight into the effects of mesopore confinement on ionic liquid resistivity. These results will allow for improved rational design of supercapacitors to account for the effect of pore diameter on electrolyte resistivity and overall device performance. DISTRIBUTION STATEMENT A. Approved for public release; Distribution is unlimited 412TW-PA-20358
Modeling of Calendar Capacity Loss of Graphite-NMC Li-Ion Battery
Authors: Su Boman , Ke Xinyou , Yuan Chris
Published: December 2020

Nowadays lithium ion batteries (LIBs) have been widely used in various portable electronic devices and electric vehicles, owing to their high power and energy densities1. The most popular LIB is using graphite anode and NMC(Lix[MnNiCo]O2) cathode2. However, battery aging is a critical issue for graphite-NMC LIBs, and currently studies on examining their capacity losses through modeling are few3-5.In this presentation, we will first introduce an electrochemical model that was developed for simulating the calendar capacity loss of a graphite-NMC Li-ion battery during the storage period. We will then present our modeling results on investigating the effects of state of charge (SOC), cell working temperature and electrode particle size on calendar capacity loss of a graphite-NMC Li-ion battery. In the end, we will discuss some strategies on reducing the calendar capacity loss and extending the graphite-NMC battery life.

Acknowledgement

This work was partially supported by U.S. DOE Industrial Assessment Center at Case Western Reserve University.

References

[1] Blomgren, G. E. (2016). The development and future of lithium ion batteries. Journal of the Electrochemical Society, 164(1), A5019.

[2] Wu, S. L., Zhang, W., Song, X., Shukla, A. K., Liu, G., Battaglia, V., & Srinivasan, V. (2012). High rate capability of Li (Ni1/3Mn1/3Co1/3) O2 electrode for Li-ion batteries. Journal of the Electrochemical Society, 159(4), A438.

[3] Lee, Y. J., Choi, H. Y., Ha, C. W., Yu, J. H., Hwang, M. J., Doh, C. H., & Choi, J. H. (2015). Cycle life modeling and the capacity fading mechanisms in a graphite/LiNi0.6Co0.2Mn0.2O2 cell. Journal of Applied Electrochemistry, 45(5), 419-426.

[4] Schmitt, J., Maheshwari, A., Heck, M., Lux, S., & Vetter, M. (2017). Impedance change and capacity fade of lithium nickel manganese cobalt oxide-based batteries during calendar aging. Journal of Power Sources, 353, 183-194.

[5] Jana, A., Shaver, G. M., & García, R. E. (2019). Physical, on the fly, capacity degradation prediction of LiNiMnCoO2-graphite cells. Journal of Power Sources, 422, 185-195.
Simulation-Based Analysis of Structural and Thermodynamic Aspects of the Electrochemical Lithiation of Silicon Nanoparticles
Authors: Lee Sangheon
Published: December 2020

Lithium-ion batteries are among the most predominant energy storage systems for portable to stationary electronic devices. Lithium-ion batteries are indispensable to laptops, mobile phones, and electric vehicles due to their high energy/power density and long cycle life. Silicon has been intensively pursued as one of the most promising anode materials because of its high specific capacity (4200 mAh/g for Li22Si5), in comparison with the conventional graphite (372 mAh/g for LiC6), and its abundance. Despite its high capacity, silicon-based anode materials suffer from fast capacity loss caused by its large volume change (>300%), unstable solid electrolyte interphase and the physical disintegration, such as racking and crumbling, of the electrode structure during lithiation and delithiation processes. Therefore, there are various research activities to control the electrochemical performance of silicon anode materials. The engineering of silicon nanostructures proved to be an effective method for improving capacity and cycling stability, since nano-sized silicon can alleviate mechanical fractures during volume changes. In particular, silicon nanoparticles can be added into the void region in the polycrystalline graphite matrix, resulting in an effective increase in the overall energy density of the anode. In this work, we designed reasonable structural models of silicon nanoparticles in terms of particle size and lithiation ratio through Monte Carlo simulations, and we conducted a series of first-principle simulations to understand their intrinsic electrochemical properties. We reported the theoretical understandings of the detailed structural and thermodynamic mechanism of the actual lithiation process of silicon nanoparticle systems based on atomistic simulation approaches. We found that the rearrangement of the silicon bonding network is the key mechanism of the lithiation process, and that it is less frequently broken by lithiation in the smaller sizes of silicon nanoparticles. The decreased lithiation ability of the silicon nanoparticles results in the lithiation potential being significantly lower than that of crystalline silicon phases, which impedes the full usage of the theoretical maximum capacity. Thus, nanosized slicon could have a negative effect on performance if they become too fine-sized. These findings provide a detailed view of the electrochemical lithiation process of silicon nanoparticles and engineering guidelines for designing new silicon-based nanostructured materials for the anode of high capacity lithium ion batteries.
Ionic and Thermal Transport in the Nasicon System Na1+XAlxTi2-X(PO4)3 (NATP)
Authors: Rohde Magnus , Seifert Hans , Ziebert Carlos
Published: December 2020

Phosphate based ceramic electrolytes are promising candidates of all-solid-state Na-ion cells. Specifically, the NASICON (Na SuperIonic Conductor) structured electrolytes can be tailored by doping and structural tuning. Therefore, our studies were focused on the evaluation of possible interrelations between mechanisms of ionic and thermal transport, thermodynamic properties as well as morphology and microstructure of ceramic Na+ ion conductors.

Within this work, we have studied the ionic and thermal transport properties along with the thermodynamic key properties of Na-ion conducting phosphate ceramics. The system Na1+xAlxTi2-x(PO4)3 with x=0.3 was taken as a Na-ion conducting model system.

In addition to the ionic transport also the thermal transport properties were measured by a Laser Flash Apparatus (LFA 427, Netzsch GmbH), which enables the direct determination of the thermal diffusivity. The specific heat capacity of the NASICON systems were measured in a differential scanning calorimeter (DSC 404, Netzsch GmbH for the high temperature range 220 to 900 °C and DSC 204, Netzsch GmbH for the low temperature range from 0 to 320 °C). The thermal conductivity was calculated from data of the thermal diffusivity, the heat capacity and the density.

In contrast to the ionic conductivity, which increases in both NASICON systems about two orders of magnitude from RT to 200 °C the thermal diffusivity and conductivity, respectively, varies only slowly in this temperature due to strong phonon scattering at point defects. Changes of the thermal transport properties within a given material system can be directly related to a variation in the phonon mean free path, which is affected by scattering processes at grain and phase boundaries, respectively, but also by defects. This is important for solid electrolytes since the number and distribution of point defects i.e. vacancies are crucial for the transport of ions within a lattice structure.
(Invited) Doping and Composition Optimization of Electrocatalysts for Water Splitting and Metal-Ion Batteries
Authors: Fan Hong Jin
Published: December 2020

Water electrolysis, fuel cells, and metal-air batteries all require efficient and cheap electrocatalysts that can significantly lower the reaction overpotentials. Bimetallic alloys and their oxides or nitrides compounds are particularly interesting as non-precious metal electrocatalyst materials for HER, OER, and ORR because of their tailorable electronic structure, conductivity, and surface chemistry. Our group has been actively working on nanoarray materials directly grown on conductive substrates as electrodes for supercapacitor, batteries and electrocatalyst.

In this talk, I will present two main results about surface and interface engineering/functionalization of array-type electrocatalysts for water splitting and for meal-ion batteries. First, we demonstrate that dual anion doping, or metal-anion co-doping in alloy compounds (Ni2P, CoP) can simultaneously modulate key parameters in water dissociation and hydrogen adsorption energies, and thus leads to a significant enhancement in catalytic activities for both HER and OER in wide-pH solutions. Second, effective bi-functional catalysts (ORR and OER) supported on doped 3D carbon supports for cathode materials in Zn-air batteries will also be presented.

This work is supported by Singapore MOE (MOE2017-T2-1-073) and A*STAR (AMEIRG18-0006).
(Invited) Approaches to Understanding and Predicting the Stability of Liquid Electrolytes and the Early Formation of the Solid-Liquid Electrolyte Interphase
Authors: Persson Kristin A.
Published: December 2020

Electrolytes with improved stability have the potential to transform the current state-of-the-art Li-ion architectures and enable future technologies such as multivalent systems (e.g., Mg2+, Ca2+ and Zn2+), as well as Li-S and Li-O2 conversion systems. A remaining challenge in the pursuit of rational design of novel and optimized electrolytes is understanding and ultimately predicting the reaction cascade responsible for the creation of a functional liquid-anode solid-electrolyte interface (SEI). We here present an overview of the challenge, coupled with several examples of systems where minority as well as majority speciation of the electrolyte is imperative to understand the origin of the electrochemical window. Furthermore, to address the complexity of the resulting reaction cascade once these species start to decompose, we advocate the need for data-driven approach coupled with a high-throughput quantum chemistry computational infrastructure. To this end, we have constructed a chemical reaction network with tens of thousands of elementary reactions which allow for bond breaking/formation as well as oxidation/reduction reactions. The reaction energetics are obtained from our computational framework which automate geometry optimization and vibrational frequency calculations for molecules, including radical, charged, metal-coordinated, and solvated species. To analyze possible reaction pathways, we apply a graph representation to our network, leveraging an iterative reweighting strategy that solves for all prerequisite branching such that traditional pathfinding algorithms correctly capture coordinated pathways. Machine-learning algorithms operating on bond-formation and breaking energetics aid in rapid evaluation of highly reactive processes. We show that without any apriori chemical intuition, our automated framework can recover favorable reaction paths to form key SEI components, which have been carefully identified over the past two decades. This data-driven approach and infrastructure show promise to accelerate the understanding of chemical reactivity in complex environments, in the aid of novel electrolyte design.
Morphological Heterogeneities of Stripped and Plated Lithium Metal Analyzed By X-Ray Tomography
Authors: Magnier Lucile , Devaux Didier , Lachambre Joël , Lecuyer Margaud , Deschamps Marc , Maire Eric , Bouchet Renaud
Published: December 2020

Lithium (Li) metal is the most promising anode battery material to be implemented in stationary and electric vehicle applications [1]. For years, its use and subsequent industrialization was hampered because of the inhomogeneous Li electrodeposits onto Li metal leading to dendrite growth [2]. The use of solid polymer electrolyte is a solution to mitigate dendrite growth but the Li redox processes, stripping and plating, remain heterogeneous. Blue Solutions compagny is already commercializing lithium metal batteries using a solid polymer electrolyte to prevent dendrite growth. A precise characterization of the behaviour of these heterogeneities during cycling is essential to move towards an optimized anode. During our research, we have developed a characterization method based on X-ray tomography applied to model Li symmetric cells to

quantify and spatially probe the Li stripping/plating process. Ante- and post-mortem cells are recut in order to allow a 1µm voxel size

in a conventional laboratory scanner. The reconstructed cell volume is post-processed to numerically re-flatten the Li electrodes, allowing

us a subsequent precise measurement of the electrode and electrolyte thicknesses and revealing local interface modifications. This in-depth

analysis brings information on the location of heterogeneities and the impact on the electrode microstructure both at the electrode grains and

grain boundaries. This simple methodology permits to finely retrieve and then surface-map the local current density at both electrodes based

on the local thickness change during the redox process (see Figure 1a : 2D map of the cathode local current density variations overlaped with

grain boundaries pattern (image analysis of a cell after moving 22µm of lithium)). Thanks to quantitative data that can be extracted from the

2D maps (see Figure 1b: anode and cathode quantitative distribution of local current density variations), we show that the plating process

(reduction) induces more pronounced heterogeneous deposits compared to the stripping (oxidation) one. The existence of cross-talking

between the electrodes is also highlighted.

[1] Wu Xu et al., Energy Environ. Sci. 7, no 2 (2014): 513-37

[2] Xin-Bing Cheng et al., Chemical Reviews 117, n°15 (2017): 10403-73

Figure 1
Predicting Electrolyte Performance in Lithium Metal Batteries at Low and High Current Densities
Authors: Galluzzo Michael D. , Balsara Nitash P.
Published: December 2020

For lithium metal batteries to surpass graphite-based lithium ion batteries as the standard for advanced applications, electrolytes must be designed to 1) stabilize the lithium metal anode and high-voltage cathode and 2) facilitating ion transport at fast rates. Composite electrolyte systems (e.g. a glassy polymer or nanoparticle dispersed in an ion-conducting medium) have frequently been proposed in an effort to fulfill the first design principle; however, it is often not clear if the second design principle can be met. Ultimately, the performance of new electrolytes should be based on comprehensive cycling experiments in full-cell configurations. Practically, we would like to leverage simple characterization techniques in order to predict full-cell performance and allow design iteration more quickly. In this talk, we will discuss experiments utilizing symmetric cell configurations (i.e. lithium/electrolyte/lithium) which can be used to predict electrolyte performance in a battery. For applications requiring small applied currents, the product of the ionic conductivity, κ, and the current fraction, ρ+, can be used to evaluate electrolyte efficacy and can be measured in a simple polarization experiment in a symmetric cell. This method is well established, and we have compiled data from the literature which reveals a tradeoff between the two parameters. For applications requiring large current densities, the problem is more complicated, especially for composite electrolytes where many parameters (six or more) are required to fully define ion transport. We have applied an approximation to Newman’s concentrated solution theory to define ion transport in a block copolymer electrolyte system (polystyrene-block-polyethylene oxide with LiTFSI) with only three transport parameters. We will discuss the results and predictions made by the theory and compare the predictions to experimental data. Our approach to characterize electrolyte performance at low and high current densities can be broadly applied to any electrolyte which can be studied in a symmetric cell configuration.
High Energy Density Hydrogen/Vanadium Hybrid Redox Flow Battery Utilizing HCl As a Supporting Electrolyte
Authors: Parra-Puerto Andres , Rubio-Garcia Javier , Cui Junyi , Kucernak Anthony
Published: December 2020

Hybrid gas-liquid hydrogen/liquid electrolyte energy storage systems known as RFCs (reversible fuel cells) replace the negative liquid electrolyte by the kinetically fast hydrogen reaction which among other advantages reduces the electrolyte cost. A significant amount of work has been devoted to the development of RFCs using halogen redox couples at the positive side, particularly bromine.[1] However, the highly corrosive environment associated with the liquid electrolyte containing halogen species leads to poor compatibility and stability of materials as well as safety issues associated with the leakage of toxic fumes. This issue can be minimized or even eradicated with the implementation of other redox couples such as organic[2] or inorganic species.[3]

We demonstrate a high energy density Hydrogen/Vanadium (6M HCl) system with increased vanadium concentration (2.5 m vs. 1 m), and standard cell potential (1.167 vs. 1.000 V) compared to previous vanadium-hydrogen systems.[4] The implementation of an Ir/C catalyst at the negative side enables a system with high energy density of ca. 45 W h L-1 at 75 mA cm-2 (assuming gas compression at 30 bar) and >67% electrolyte utilization.

References

1] K. T. Cho, M. C. Tucker, and A. Z. Weber, “A Review of Hydrogen/Halogen Flow Cells,” Energy Technol., vol. 4, no. 6, pp. 655–678, Jun. 2016, doi: 10.1002/ente.201500449.

[2] J. Rubio-Garcia, A. Kucernak, R. Liu, and B. Chakrabarti, “Hydrogen/functionalized benzoquinone for a high-performance regenerative fuel cell as a potential large-scale energy storage platform,” J. Mater. Chem. A, vol. 8, no. 7, pp. 3933–3941, Feb. 2020, doi: 10.1039/c9ta12396b.

[3] J. Rubio-Garcia et al., “Hydrogen/manganese hybrid redox flow battery,” J. Phys. Energy, vol. 1, no. 1, p. 015006, Dec. 2018, doi: 10.1088/2515-7655/aaee17.

[4] J. Rubio-Garcia, J. Cui, A. Parra-Puerto, and A. Kucernak, “High Energy Density Hydrogen/Vanadium Hybrid Redox Flow Battery Utilizing HCl as a Supporting Electrolyte for Large Scale Energy Storage Applications.” Under Review.

Figure 1
Compatibility of Porous Silicon with Lithium Polysulfides for Full Cell Lithium Ion Battery Applications with Sulfur Cathodes
Authors: Cavers Heather , Krüger Helge , Polonskyi Oleksandr , Adelung Rainer , Nöhren Sandra
Published: December 2020

Crystalline silicon is an ideal anode candidate for lithium ion batteries as it offers a high Li+ ion storage capacity, direct current pathway and is a stable and earth abundant element. In order to match the high theoretical energy density of silicon in lithium ion batteries a suitable cathode material is required. Sulfur based cathodes have a high theoretical storage capacity for application in lithium ion batteries, based on the conversion reaction of the cyclic S8 molecule with lithium to form smaller lithium polysulfides up to Li2S, and are also cheap and earth abundant. One of the major drawbacks of lithium sulfur cathode materials is the tendency of lithium polysulfides to be dissolved by the electrolyte, which causes the polysulfides to migrate away from the cathode, leading to an overall capacity loss. For application of porous silicon in a full cell lithium ion battery with sulfur it is important to understand the impact the presence of lithium polysulfides can have on the functionality of porous silicon as an anode. In this study porous silicon anodes with thicknesses of 6 µm and 12 µm were cycled in a half cell in the presence of varying concentrations of Li2S6 (0 M, 0.017 M and 0.083 M). For the electrolyte with 0.017 M Li2S6 the cycling behavior was comparable, or better, than the electrolyte with no polysulfides. The SEI layer formed on the surface of the porous silicon anodes was investigated ex situ with X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy after one, five and ten cycles. It was seen that in the first cycle lithium polysulfides are contained in the SEI and undergo an oxidation reaction to form sulfates over the following cycles. This leads to a more inorganic SEI layer in the presence of polysulfides, especially in the case of the 12 µm porous silicon, and long term cycling stability. The 12 µm porous silicon anode cycled in the presence of 0.083 M Li2S6 showed stable cycling behavior over one hundred cycles, with limited capacity loss and coulombic efficiencies of 96.2 % after one hundred cycles.
Interface Structure and Transport Properties of Thin-Film Solid-State Batteries with an Epitaxial Cathode
Authors: Shirasawa Tetsuroh , Shiraki Susumu , Nishio Kazuo , Shimizu Ryota , Hitosugi Taro
Published: December 2020

A problem of solid-state Li ion batteries is a relatively low ionic conductivity at the interface between electrodes and electrolytes that limits the charging/discharging rate. For designing the solid-state batteries, understanding the mechanism behind the low interface conductivity is crucial. Investigation of the atomic structure of the interfaces and its relation to the ionic conductivity would be helpful for this purpose. However, atomic-scale observation of the buried interfaces is often difficult in practical batteries which consist of grain aggregates. Recent progress in thin-film deposition techniques of electrodes and electrolyteshas opened a path to study the interface quantitatively. By using an all-in-vacuum battery fabrication system [1], we succeeded in fabricating a very low solid-electrolyte/electrode interface resistance in thin film batteries with an epitaxial cathode. The well-defined crystalline interfaces allow the analysis of atomic-scale structure and its transport properties. For the structure analysis, we used X-ray crystal truncation rod (CTR) scattering which enables the atomic-scale analysis in a non-destructive manner.

The analysis of two interfaces will be presented: a solid-electrolyte/electrode interface and an electrode/current collector interface. In the former case, we studied Li(negative electrode)/Li3PO4(solid electrode)/LiCoO2(positive electrode) thin-film Li batteries with low and high (more than 10 times) interface resistances. It turned out that the low-resistance interface has an atomically well-ordered LiCoO2 surface and a disordered surface CoO2 layer can results in the high-resistance interface, demonstrating the crucial importance of the structural ordering in the interfacial layer for realizing a low-resistance interface [2]. In the second topic, we focused on electrode/current collector interface that can also affect the battery performance. We found a drastic improvement of the charging/discharging property by inserting 1.2 nm-thick band insulator LaAlO3 into the LiCoO2 (electrode)/Nb-doped SrTiO3 (current collector) interface. The CTR analysis revealed that a formation of electric dipole at the LaAlO3/Nb-doped SrTiO3 interface, which causes a energy band alignment preferable for the electronic conductance between the electrode and the current collector.

References

[1] M. Haruta, T. Hitosugi et al., Nano Lett. 15, 1498 (2015)

[2] S. Shiraki, T. Shirasawa et al., ACS Appl. Meter. Interfaces 10, 41732 (2018)

Figure 1
(Invited) Lithium Metal Polymer Batteries: State-of-the-Art of the Technology and Commercial Prospects
Authors: Lecuyer Margaud
Published: December 2020

BlueSolutions has been commercializing all-solid state batteries since 2011. EVs, buses and stationary applications are the main targets of its research and development program. After more than 15 years, this Bolloré group subsidiary masters all the industrial processes for the production of a unique solid state battery technology. The know-how goes from the transformation of the lithium ingots to the integration of the battery packs within the applications. Importantly, a low-ecological footprint process has been stated for both the positive electrode and the polymer electrolyte manufacturing.

In order to get incomparable energy densities, today, all the industrial actors of lithium batteries are hardly working on the lithium metal technology. In this context, BlueSolutions has a unique 10 years feedback regarding both the behavior of this special anode and of the solid-state electrolyte.

After having spread the first pack generation for 8 years all-over the world, an optimized 650V battery pack is about to be delivered. It is especially designed for heavy vehicles, such as buses. To match with customers expectations this new generation offers optimized performance and a very long cyclability. In the meanwhile, BlueSolutions has already started working on its future generation products. While the current battery is LFP-based and cycles at a nominal temperature of 80°C, a lot of efforts are dedicated to improve the actual chemistry. Research programs are conducted on the development of a new positive electrode with higher energy density, new polymers that will be compatible with high-voltage materials and which have high conductivity at ambient temperature and optimized lithium electrode. In fine, the goal is to keep the intrinsic safety of the polymer solid electrolyte, while benefiting from the promising performances of new electrode materials.