bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible Free-Standing Tin-Based Carbon Nano Tube Composite Anodes for Li-Ion Batteries
Authors: Alaf Mirac , Akbulut Hatem
Published: February 2020

In this study, tin/tinoxide/multi walled carbon nano tube (Sn/SnO2/MWCNT) composite anodes produced as flexible and free-standing. MWCNT papers (buckypapers) were prepared by vacuum filtration from oxidized MWCNTs with controlling porosity. Double phase Sn/SnO2 structure was deposited onto buckypapers by thermal evaporation and subsequent plasma oxidation. The ratio between metallic tin (Sn) and tinoxide (SnO2) was controlled with plasma oxidation time. It was determined that the evaporated pure tin nano crystals were mechanically penetrated into pores of buckypapers to form functionally gradient nanocomposites. Structure and morphology of the composite anodes were investigated by field emissions scanning electron microscopy (FE-SEM), transmission electron microscopy and X-ray diffractometer. In addition the discharge/charge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out to characterize the electrochemical properties of these composites as anode materials for ultra-thin and flexible batteries.
Self-Healing in Li-Ion Battery Electrodes
Authors: Okman Oya , Kang Sen , Jones Elizabeth M. C. , White Scott R. , Sottos Nancy R.
Published: February 2020

Battery lifetime relies on the electrical and mechanical integrity of its electrodes. A common cause of degradation of performance in Li-ion batteries is the capacity loss in negative electrode due to extensive mechanical cracking. During the regular operation of a battery, subsequent charging and discharging cycles induce high, cycling mechanical stress in graphite and silicon based electrodes resulting in crack initiation and growth. In this study, we introduce a microcapsule based autonomous healing approach to restore functionality across the through-cracks in battery electrodes. We use a custom designed battery cell, by which we observe a double clamped negative electrode in-situ during subsequent cycles, capture cracking by a CCD camera and assess mechanical failure/healing through capacity data. We incorporate microcapsules with a conductive core within or on the electrode to deliver their contents at the damage zone. The electrode design involves a mechanically vulnerable region to shorten the experiment time and to enable us to predict the crack location. We induce a capacity loss based on mechanical failure and then assess the effectiveness of autonomous restoration of battery capacity during its regular operation.
Advanced Multiphase Silicon-Based Anodes for High-Energy-Density Li-Ion and Li-Air Batteries
Authors: Golodnitsky Diana , Goldstein Keren , Freedman Kathrin , Menkin Svetlana , Peled Emanuel
Published: February 2020

Given that lithium-ion and lithium-air batteries are the preferred choice for EVs and plug-in applications for the next 10–15 years, the focus is on improving their safety and performance. New, higher-capacity materials are required in order to address the need for greater energy density, longer cycle life and safer high-power operation. Silicon offers the highest gravimetric and volumetric capacity as an anode material (e.g. Li22Si5: nearly 4,200mAh/g, 9,800mAh/mL). The lithium-rich silicon compounds have high melting points. Their higher working potentials (vs. Li) eliminate the possibility of metallic-lithium deposition due to overcharge. Silicon is the second-most abundant element in the earth’s crust, and it is environmentally benign. Unfortunately, Si-based electrodes typically suffer from large volume changes (up to 420%) during insertion and extraction of lithium. This is followed by cracking and pulverization of silicon, which in turn, leads to the loss of electrical contact, unstable SEI and eventual capacity fading.

We have developed two synthetic routes for the preparation of core-shell silicon multiphase composite particles. We studied the process of formation of the protective SEI layer on the anode nanoparticles and tested small laboratory-prototype cells with advanced anodes. The methods of attachment of silicon nanoparticles to carbon nanotubes (multi-wall carbon nanotubes (MWCNT)) were developed with the purpose of creating silicon anodes supported by a strong, rigid and high-electrically-conducting matrix. The methods are based on the silanization process or pyrolysis. STEM analysis showed that silicon particles are dispersed uniformly on the surface of the MWCNT. ESEM images indicated the formation of silicon nanoparticles wrapped by carbon nanotubes and coated by nanometer thick amorphous carbon. TEM, EELS and XPS tests confirm the formation of a layer of carbon on top of the silicon nanoparticles and Si-C bonding (Fig.1). The feasibility of using electrophoretic deposition for the preparation of composite silicon anodes coated by a ceramic-in-polymer protective layer has been proven.

Li/LiPF6 EC:DEC/Si-C-MWCNT cells with anodes composed of about 50% core-shell Si-C composite exhibited de-intercalation capacity of 1373mAh/gSi at the 50th cycle and 1021mAh/cm2 at the 410thcycle. Li/LiTFSI-Pyr14/Si-C-MWCNT cells ran for more than 30 cycles with capacity of 1500mAh/gSi. Doped Si-alloy nanoparticles were formed by electrochemical means. The anodes are being tested.

Acknowledgments

Research is funded by EU FP7, contract no. 265971 and by Israel Academy of Science
Monitoring the Location of Cathode Reactions in Li-O2systems
Authors: Landa-Medrano Imanol , Pinedo Ricardo , Ruiz de Larramendi Idoia , Ortiz-Vitoriano Nagore , Jimenez de Aberasturi Dorleta , Ruiz de Larramendi José Ignacio , Rojo Teófilo
Published: February 2020

Lithium-oxygen (Li-O2) batteries have been considered as a promising alternative for high energy storage systems due to their exceptional theoretical energy density. However, many obstacles need to be overcome before developing a safe, green and efficient commercial dispositive [1,2].

One of the key issues of these batteries is the employed electrolyte. Carbonates have been inherited from Li-ion technology, becoming their use popular in the early steps of development of Li-O2 systems. However, due to their decomposition at high potentials [3,4], they are slowly being replaced by other type of electrolytes such as glymes or ionic liquids. In order to study these processes, in addition to common electrochemical characterisation techniques, X-ray photoelectron spectroscopy (XPS), impedance spectroscopy and transmission electron microscopy (TEM) have proved to be fundamental techniques for in situ monitoring of reaction products that take place during charge and discharge [5-7]

In this work, it is proved that the use of organic solvents with low oxygen solubility reduces the active area for the oxygen reduction reaction (ORR) to the oxygen cathode electrolyte triple interface (OCETI). For this aim electrodes loaded with different carbon masses have been cycled in different conditions and post-mortem analyzed by means of X-ray diffraction (XRD), scanning electrode microscope (SEM) and x-ray photoelectron spectroscopy (XPS). The obtained data evidence that the most of the cathode is not active in each stage of the cycling process (Figure 1.a and 1.b). Consequently, expressing the obtained specific capacity values in mA h g-1 units or the current densities in mA g-1 becomes undesirable as it leads to non reasonable comparisons. Moreover, the analysis of the cyclability has evidenced the competition between the OCETI (Figure 1.c) and the applied intensity (Figure 1.d) as the main limiting factors for the performance of these Li-O2 systems.

References:

[1] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, W. Wilcke, J. Phys. Chem. Lett. 1 (2010) 2193−2203.

[2] K.M. Abraham, Z. Jiang, J. Electrochem. Soc. 143 (1996) 1−5.

[3] S.A. Freunberger, Y. Chen, N.E. Drewett, L.J. Hardwick, F. Bard, and P.G. Bruce, Angew. Chem. Int. Ed. 50 (2011) 8609−8613.

[4] Y. Chen, S.A. Freunberger, Z. Peng, F. Bardé, P.G. Bruce, J. Am. Chem. Soc. 134 (2012) 7952−7957.

[5] Y.-C. Lu, B. M. Gallant, D. G. Kwabi, J. R. Harding, R. R. Mitchell, M. S. Whittingham and Y. Shao-Horn, Energy Environ. Sci 6 (2013) 750-768.

[6] I. Landa-Medrano, I. Ruiz de Larramendi, N. Ortiz-Vitoriano, R. Pinedo, J.I. Ruiz de Larramendi and T. Tojo, J. Power Sources 249 (2014) 110-117

[7] L. Zhong, R. R. Mitchell, Y. Liu, B. M. Gallant, C. V. Thompson, J. Yu Huang, S. X. Mao and Y. Shao-Horn, Nano Lett. 13 (2013) 2209-2214.
Suppression of Unwanted Reactions on the Carbon-Based Air Electrode
Authors: Yoon Dae Ho , Park Yong Joon
Published: February 2020

In the past decade, lithium ion batteries have played a dominant power source for items ranging from portable electronics to hybrid electric vehicles. However, they still do not offer enough energy density to meet the ever-increasing demands of many applications despite extensive research to explore ways to increase their charge-storage capability. As a new energy storage system, Li-air batteries have attracted numerous attentions because they have the potential to provide several times higher capacity than commercial Li-ion cells [1-2]. Li-air batteries have been developed in different types according to the electrolytes employed, such as aqueous, non-aqueous, and hybrid systems. Because of relatively simple configuration and large real capacity, non-aqueous system is most active all Li-air batteries. Much research effort has been devoted in order to enhance the performance of Non-aqueous Li-air cells [3-4]. However, they still are facing fundamental and practical challenges such as low rate capability, limited cycle life resulting from the instability of the electrode and electrolyte, and significant overpotential on charge due to slow kinetics of dissociation from reaction products (such as Li2O2). These critical issues are highly attributed to the air electrode, the reaction place between lithium ion and oxygen, and electrolyte directly contact with electrode. In this study, the suppression of unwanted reactions on the air electrode during cycling is main issue. With aim to suppress the unwanted reactions, the surface of carbon was passivated by stable materials. The surface defects of carbon facilitate unwanted electrolyte decomposition reactions during cycling, which deteriorate the cyclic performance of air cell [5-6]. So the passivation of carbon is expected as an effective approach for enhancing the cycling performance of the Li-air batteries.

References

[1] A. Kraytsberg, Y. Ein-Eli, J. Power Source. 196 (2011) 886

[2] A. Débart, J. Bao, G. Armstrong, P.G. Bruce, J. Power Sources 174 (2007) 1177

[3] D. Capsoni, M. Bini, S. Ferrari, E. Quartarone, P. Mustarelli 220 (2012) 253

[4] Z. Peng, S. A. Freunberger, L. J. Hardwick, Y. Chen, V. Giordani, F. Bardé, P. Novák, D. Graham, J. M. Tarascon, and P. G. Bruce, Angew. Chem. Int. Ed. (2011) 50, 1

[5] J. Lu, Y. Lei, K. C. Lau, X. Luo, P. Du, J. Wen, R. S. Assary, U. Das, D. J. Miller, J. W. Elam, H. M. Albishri, D. A. El-hady, Y. K. Sun, L. A. Curtiss, K. Amine, Nat. Commun. 4 (2013) DOI: 10.1038/ncomms3383.

[6] B. D. McCloskey, A. Speidel, R. Scheffler, D. C. Miller,V. Viswanathan, J. S. Hummelshøj, J. K. Nørskov and A. C. Luntz, J. Phys. Chem. Lett. 3 (2012) 997.
Li-S Cathodes with Extended Cycle Life By Sulfur Encapsulation in Disordered Micro-Porous Carbon Powders
Authors: Aurbach Doron , Rosenman Ariel , Salitra Gregory , Elazari Ran , Garsuch Arnd
Published: February 2020

Sulfur cathodes have excellent theoretical properties for use as positive electrodes in rechargeable lithium batteries, but lack long-term stability required of practical secondary battery systems. To deal with this issue, high capacity Lithium-Sulfur cathodes with extended cycle life were prepared through thermal encapsulation of sulfurat 155°C in disordered micro-porous carbon powders that have high specific surface-area of ~ 2000 m2/g. The electrodes have been characterized using X-ray diffraction (XRD), Scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), Raman spectroscopy, Thermal Gravimetric Analysis (TGA) and Gas adsorption technique. By using microporous carbon as matrices for sulfur cathodes and lithium nitrate as an additive to the electrolyte solution, that suppresses the shuttle phenomena in Li-sulfur batteries, we managed to achieve a reversible capacity of over 500mAh/g after 1000 cycles (Figure 1) with a Columbic efficiency approaching 100% throughout cycling. The sulfur composite cathodes of 14mm in diameter (area of ~1.54 cm2) and active material load of more than 1mg/cm2were tested in a two electrodes configuration with coin-type cells (2523,NRC, Canada). Electrolyte solution was DOL and DME (1:1 ratio) with 10% LiTFSI and 2% of LiNO3(by weight).

The influence of the volume of the electrolyte solutions in Li-S cells was further evaluated by analyzing their voltage profiles during cycling.
Li-Oxygen Versus Li-Ion Battery Systems: Chances and Challenges for Utilization in the Automotive Industry
Authors: Traußnig Thomas , Fink Clemens , Lukacs Andras , Stuetz Harald , Hennige Volker
Published: February 2020

Due to its ultra-high energy density Li-oxygen battery technology is one of the first-choice candidates for the realization of full electric vehicles capable of covering a driving range beyond 500 km [1].

The present contribution deals with the development of a full system for operating Li-oxygen technology in an automotive environment.

Electrochemical models based on the work of Doyle and Newman [2] as well as battery system requirements form the fundament for developing a suitable Li-oxygen cell design (i.e. simulation of reactant flow). The integration of the cells into a full battery system is elaborated in detail with special focus on the requirements of Li-oxygen technology [3]. For the Li-oxygen battery system an operation strategy is described. A discussion of range- and power capabilities as well as predictions for weight and volume of the full battery system for achieving a vehicle range beyond 500 km is presented. With the help of statistical methods safety aspects of Li-oxygen battery pack design are studied. In addition a comparison between conventional Li-ion technology and Li-oxygen technology on battery system level is drawn.

Our findings point out that both Li-oxygen and Li-ion technology feature mutually beneficial properties with respect to energy and power density and that a combined use of these technologies is highly recommendable for automotive applications.

[1] Girishkumar et al, J. Phys. Chem. Lett. 1, (2010), p.2193-2203

[2] J. Adams, M. Karulkar, J. Power Sources 199 (2012) 247-255

[3] Traußnig et al, Poster Session, Kraftwerk Batterie (2013)

Acknowledgement

The research leading to these results has received funding from the European Union’s Seventh Framework Program under EC-GA No. 265971 ‘LABOHR’.

The attached image shows a Li-oxygen pack design which is separated into three different areas (oxygen uptake area in yellow, cell assembly in blue and E/E unit in red -> see also integrated caption). The simulation on the upper right side of the image studies the impact of the reactant flow on cell chemistry, whereas the simulation on the lower right side of the image investigates the impact on system level.
In Situ Synchrotron XRD on a Capillary Li-O2 Battery Cell
Authors: Storm Mie Møller , Johnsen Rune E. , Norby Poul
Published: February 2020

In situ studies give an opportunity to explore systems with a minimum of external interference. As Li-air batteries hold the promise for a future battery technology the investigation of the discharge and charge components of the cathode and anode is of importance, as these components may hold the key to making a large capacity rechargeable battery[1]. Different design for in situ XRD studies of Li-O2 batteries has been published, based on coin cell like configuration[2] [3] or Swagelok designs [4]. Capillary batteries have been investigated for the Li-ion system since its development[5], but no capillary batteries of Li-air has yet been designed. Some of the advantage of the capillary battery design lies in its ability to separate the cathode and anode and avoid the use of glass fiber or separators, which may enable ex situ analysis of battery components. The battery design consist of a electrolyte filled capillary with anode and cathode in each end suspended on stainless steel wires, the oxygen in-let is placed on the cathode side of the capillary with a flushing system for oxygen in-let. In this study we present a flexible design of a capillary based Li-O2 battery with discharge and charge investigated in dimethxyethane (DME) with synchrotron XRD. The in situ study in these batteries show clearly how Li2O2 precipitates on the cathode side of the battery during discharge (see Figure), as the Li2O2 reflections at 21.2°, 22.5° and 37.1° grows. The reflection at 27.8, 28.4 and 32.16 is from a stainless steel wire where the cathode is attached. The in situ XRD measurements show how the Li2O2 growth depend on current discharge rate and how the FWHM changes dependent on reflection and charge/discharge.Several cells were tested both ex situ and in situ, and in situ XRD for 1st discharge/charge and 2nd discharge/charge of the battery cell were measured, to give a better understanding of the electrochemistry in the Li-O2battery.

1. Girishkumar, G., et al.. The Journal of Physical Chemistry Letters, 2010. 1(14): p. 2193-2203.

2. Lim, H., E. Yilmaz, and H.R. Byon, The Journal of Physical Chemistry Letters, 2012. 3(21): p. 3210-3215.

3. Ryan, K.R., et al.,. Journal of Materials Chemistry A, 2013. 1(23): p. 6915-6919.

4. Shui, J.-L., et al., Nat Commun, 2013. 4.

5. Johnsen, R.E. and P. Norby,. Journal of Applied Crystallography, 2013. 46(6): p. 1537-1543.
Effect of Resting Periods over Cycling Performance of a Li-Ion Battery
Authors: Rashid Muhammad , Gupta Amit
Published: February 2020

Vehicles powered by Li-ion batteries (hybrid- and electric-vehicles) offer an attractive alternative to the typical gasoline fuelled vehicles due to their potential in reducing dependence on fossil fuels, reduction in air pollution and noise-free operation. However, the life of these batteries is limited due to the irreversible or degradation reactions that occur in these energy storage systems. It is widely believed that operational parameters such as charge/discharge rates, resting duration, depth of charge and discharge play an important role in enhancing the cycling life of these battery systems. Providing batteries with a rest period after discharging and charging might be essential for relaxation of gradients generated due to the passage of current. In the present work, the effect of open-circuit time durations, after the completion of each charge and discharge segment, over the performance of Li-ion cells will be analyzed and quantified. The applied current profile used to conduct numerical simulations is shown in Fig. 1. In this figure, tdch, trest,1, tch, and trest,2 are the discharge, rest after discharge, charge, and rest after charge durations respectively. The impact of different rest durations on the discharge capacity over 1000 cycles is shown in Fig.2. It was observed that resting the cell after discharge has significant influence over cell performance, whereas resting after charge has a marginal effect. In the former case, a relatively thicker film forms at the solid-electrolyte interface in the negative electrode. Moreover, a longer resting period at the end of discharge results in a higher concentration of lithium in the solid matrix of the negative electrode, leading to a higher cell potential during the discharge phase of the subsequent cycle. Similarly, charging the cell following a relatively longer resting period at the end of discharge results in a lower concentration of lithium in the positive electrode indicating a better utilization of cyclable lithium and hence a higher battery capacity. In the future, the effect of resting duration on the solid and electrolyte concentration, and local electrolyte potential will be studied to identify reasons which lead to an improvement in achievable cell capacity and potential which can be foreseen to be helpful in achieving improved cell life and rate capability in these energy storage systems.
Estimating Thermal Parameters of Large-Format Laminated Lithium-Ion Batteries Using Thermal Impedance Spectroscopy
Authors: Wu Bin , Zhang Jianbo , Zhou Jun , Li Zhe
Published: February 2020

The accuracy of battery thermal parameters is crucial to the accuracy of thermal simulations for batteries. Given the structural characteristics of the large-format laminated lithium-ion battery [1], effective methods to determine multiple thermal parameters, such as the thermal conductivity and the specific heat capacity, should be developed to achieve better prediction of battery thermal behaviors.

Generally, the methods for measuring the thermal parameters of batteries can be divided into two categories, the time-domain method and the frequency-domain method. The authors developed a joint computational and experimental time-domain method to estimate the multiple thermal parameters for a 25 Ah laminated lithium-ion battery both in-situ and simultaneously [1]. However, the battery temperature changed from 25 to 35°C in the experiment, hence the estimated thermal parameters were the average properties over 25~35°C. In contrast, the change in the temperature of the sample can be greatly reduced in the frequency-domain method, making it possible to obtain the thermal parameters at different temperatures.

In this work, a frequency-domain method, the thermal impedance spectroscopy (TIS) method is used to simultaneously and in-situ determine two thermal parameters, i.e. thermal conductivity and specific heat capacity, for the large-format laminated lithium-ion battery.

In the experiment, a planar electric heater is sandwiched between two identical batteries (25 Ah, 250 mm × 220 mm × 7.2 mm，NMC-LMO/Graphite), as shown in Fig. 1(a). The electric power for the heater is adujusted at different frequencies (0.1, 0.2, 0.4, 0.6, 0.8 and 1 mHz) and the temperature response on one outer surface is recorded with the attached thermocouple. The entire set-up is placed in an environment chamber.

The heat transfer behavior between the heating power and the temperature response is examined in the frequency domain. An equivalent thermal circuit including thermal capacity and resistance is introduced to derive the analytical expression of thermal impedance, as shown in Fig. 1(b). The thermal circuit is simplified from the 1D heat conduction model, which also takes the covering aluminum-plastic film into account. The thermal conductivity and capacity of the battery core are estimated using the least-square fitting algorithm. The experimental and fitted thermal impedance are shown in Fig. 1(c).

The estimated parameters are validated against the results from the accelerating rate calorimeter (ARC), the heat flow calorimeter (HFC) and the joint computational and experimental time-domain method [1].

Reference

[1] Zhang J, Wu B, Li Z, et al. Simultaneous Estimation of Multiple Thermal Parameters of Large-Format Laminated Lithium-Ion Batteries[C]//Vehicle Power and Propulsion Conference (VPPC), 2013 IEEE. IEEE, 2013.
Numerical Simulation and in-operando Measurement of the Local Temperature Evolution in a Lithium Ion Battery Cell
Authors: Heubner Christian , Schneider Michael , Junker Nils , Lämmel Christoph , Michaelis Alexander , Hess A. , Mortazavi B. , Roode-Gutzmer Q. , Yang H. , Bobeth Manfred , Cuniberti G.
Published: February 2020

Aiming at a better quantitative understanding of the fundamental mechanisms that cause heat evolution in lithium ion batteries, theoretical modeling of the temperature evolution was performed associated with in-operando temperature measurements across the interfaces of a single lithium ion battery cell. For that purpose, an experimental setup has been developed at the Fraunhofer IKTS. The cylindrical electrode arrangement and the positioning of the thermocouples at specific interfaces within the lithium ion cell is illustrated in the figure. The success of this experimental approach has recently been demonstrated [1]. The present modeling is based on Newman's pseudo-2D model [2], extended however by including a radial spatial dependence of the electrochemical processes and SoC-dependent material properties. To evaluate the reliability of the electrochemical modeling, simulations of GITT experiments were compared with corresponding measurements using a 3-electrode arrangement. Calculations of the electric potential and current densities within the cell during charging and discharging yield the spatially resolved heat-source densities. The simulations enable the comparison of different contributions to the local heat generation. Reversible heat due to entropy changes, irreversible reaction heat, and ohmic heating within the electrode materials and the electrolyte are included in the temperature model as a function of the SoC for a wide range of charge/discharge rates. The effect of parameter variations on the temperature evolution has been extensively explored, particularly in view of different reported material properties [3]. Differences in the heat generation within the cathode, separator, and anode as a function of time, charge/discharge rate and SoC were successfully identified both theoretically and experimentally. Generally, the numerical results and the measurements reveal the significance of reversible heat effects due to electrochemical reactions under near equilibrium conditions, whereas Joule heating becomes important at high current densities. In-operando measurements allow time-resolved as well as SoC-dependend study of key parameters for the numerical simulation. The present work magnificently show the strong relation between the fundamental electrochemical processes and the resulting heat impact.

[1] C. Heubner, M. Schneider, C. Lämmel, U. Langklotz, A. Michaelis; In-operando temperature measurement across the interfaces of a lithium-ion battery cell; Electrochim. Acta, 113 (2013) 730-734.

[2] M. Doyle, T.F. Fuller, J. Newman; Modeling of galvanostatic charge and discharge of the lithium/polymer/insertion cell; J. Electrochem. Soc. 140 (1993) 1526-1533.

[3] M. Park, X. Zhang, M. Chung, G.B: Less, A.M. Sastry; A review of conduction phenomena in Li-ion batteries; J. Power Sources 195 (2010) 7904-7929
In-Situ Observation of Solid Electrolyte Interphase on LiCoO2 during Cycling to 4.5 V By AFM
Authors: Lu Wei , Zhang Jiansheng , Chen Liwei , Wu Xiaodong
Published: February 2020

LiCoO2 is the most common cathode material for commercial lithium-ion batteries due to its high tap density, excellent cycling performance and high rate capability. Though LiCoO2 has a theoretical capacity of 274 mAh/g, its reversible capacity is limited to around 140 mAh/g when cycled between 3.0 V and 4.2 V vs Li metal. Increasing the upper cutoff voltage can extract more lithium ions beyond Li0.5CoO2, which can increase the reversible capacity of LiCoO2. However, the electrolyte will be oxidized at such high voltage, which will consume the electrolyte, and form solid electrolyte interphase (SEI) on the surface. The thickness, stability will influence the electrochemical performance of LiCoO2cathode at high voltage.

In this work, we used atomic force microscope (AFM) to study the properties and evolution of SEI films on LiCoO2 cathode during electrochemical cycling. Different structure and evolution processes of SEI on different crystal faces //(001) and „¨(001) were observed in-situ during the electrochemical reaction. We also study the protecting effect of a thin layer of Al2O3 film on the surface of LiCoO2micro-crystal prepared by atomic layer deposition (ALD) technique.

Figure. (a) LiCoO2 micro-crystal prepared by melting-salt method. (b) LiCoO2 micro-crystal embedded in Al substrate. Topography images of LiCoO2 micro-crystal //(001) face obtained in-situ by AFM at original (c) and charged to 4.5 V (d). Topography images of LiCoO2 micro-crystal „¨(001) face obtained in-situ by AFM at original (e) and charged to 4.5 V (f).
In Situ Investigation on Spatiotemporal Changes of SEI Properties By SECM
Authors: Bülter Heinz , Peters Fabian , Schwenzel Julian , Wittstock Gunther
Published: February 2020

In our society Li-ion batteries are widely used, especially for small-scale devices. During the first charging process the solid-electrolyte-interface (SEI) between the electrode and electrolyte is established. This layer passivates the surface against electron transfer reaction but allows transfer of Li-ions. In order to realize high-energy Li-ion batteries in conventional carbonate-based electrolytes, the formation of the SEI is required.[1]

Content and structure of the SEI are highly discussed.[2, 3] The SEI represents a complex chemical system, where several solid, liquid and gaseous compounds establish interdependent equilibria. Characterization of the SEI is a difficult challenge, because of the similar chemical identity of SEI components and electrolyte molecules. Furthermore, ex situ analysis of the SEI requires separation and isolation of the SEI, which may change the content and the structure of the SEI.[3]
In situ analysis is highly sought after to circumvent this problem.

In our approach we use the scanning electrochemical microscopy (SECM) to investigate in situ the electron transport across the SEI. For this purpose, a redox mediator is added to the electrolyte, which communicates between the battery electrode and the positionable ultra-microelectrode (UME). Our results by SECM demonstrate the dynamic of SEI formation and dissolution. Furthermore, the swelling behavior of practical graphite anodes in standard battery electrolytes is characterized.

References

[1] J. B. Goodenough, K.-S. Park, J. Am. Chem. Soc.
2013, 135, 1167.

[2] V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci.
2011, 4, 3243.

[3] P. Verma, P. Maire, P. Novak, Electrochim. Acta
2010, 55, 6332.
New Synthetic Methodology of Hybrid Materials for Energy-Related Applications
Authors: Herreros Lucas Carlos , Khlobystov Andrei N , Gimenez Lopez Maria del Carmen
Published: February 2020

New hybrid nanomaterials are strictly required to meet the future energetic demand. In this context, supercapacitors are proposed as the ideal candidate to fill the energetic gap between batteries and conventional capacitors, showing higher power and energy density respectively [1]. Supercapacitos are based on two storage mechanism: i) electrochemical double layer, which relay on electric charge storage and ii) pseudocapacitance, which is associated with the surface redox processes at electrode materials. As the former has high cycling stability while the latter present higher capacitance, research is focused on combining materials which present both mechanisms.

Nowadays, the widely used conventional approach is based on a physically mixture of both materials. Carbon nanostructures are currently the most used support material for electrochemical applications mainly due to their low cost and high surface area, directly related to electrochemical double layer. Thus, pseudocapacitance materials such as metal oxides nanoparticles are the active material combined with the carbon support, leading to a much better distribution and also increment of the electrochemical properties. However, simple mixing these two nanocomponents affords limited interactions between them, leaving a significant portion of the material electrochemically inactive. Therefore, new synthetic procedures must be developed if new hybrid materials want to be achieved [2,3]

Here, we report a novel one-step methodology for preparing hybrid metal-carbon nanostructures by using pre-treated carbon nanofibers as templates for directing the in-situ syntehsis of surfactante-stabilised manganese oxide nanoparticles selected as model system for studying the structure-energy storage capacity relationship of the obtained hybrid nanostructure by electrochemical means.

[1] Simon, P. et al., Nature Materials, 2008. 845(7): p. 275709. [2] Gimenez-Lopez M. C. et al., Angew Chem. Int. Ed. Engl., 2013. 52(7): p. 2051-4. [3] La Torre, A., et al., ACS Nano, 2012. 6(3): p. 2000-2007.
Porous SiC/Graphene-on-Wafer Electrodes for Supercapacitors
Authors: Ahmed Mohsin , Khawaja Mohamad , Notarianni Marco , Wang Bei , Goding Dayle , Gupta Bharati , Boeckl John J. , Takshi Arash , Motta Nunzio , Saddow Stephen E. , Iacopi Francesca
Published: February 2020

The intensive research on epitaxial 3C SiC/Si wafers has opened up a new era for the micro-fabrication industry and led to the direct growth of high quality and large area graphene layers on the device location for on-chip applications.[1] This new technology to grow graphene on silicon possesses various advantages over the conventional methodology, such as eliminating the complex and unreliable process of transferring graphene flakes and replacing expensive SiC wafers, and also prompts the use of graphene for energy storage, e.g. as supercapacitors, at wafer level. However, morphology control of the graphene layers on silicon remains a challenge to further enhance the performance of supercapacitors, which mainly relies on the surface area of the active graphene layers through an electrochemical double layer mechanism. To address this issue, we demonstrate, for the first time, creating porosity on the graphene surface. The growth of porous graphene on wafers in our work presents a facile, highly reproducible and low-cost approach to obtain highly continuous graphene layers with extremely low sheet resistance. Our preliminary electrochemical investigation indicates that the porous SiC/graphene-on-wafer electrode can deliver typical supercapacitive behaviours and the porosity we create on the graphene surface can facilitate the electrochemical performance by providing more accessible surface area. Graphene prepared via this routine can also be employed to fabricate micro-supercapacitors in an interdiginated pattern for future on-chip integration and energy storage.

[1] B.V. Cunning, M. Ahmed, N. Mishra, A.R. Kermany, B. Wood, F. Iacopi, Nanotechnology, 25 (2014) 325301.
Molecular Engineering of Zinc Phthalocyanine Sensitizers for Efficient Dye-Sensitized Solar Cell
Authors: Kimura Mutsumi
Published: February 2020

Dye-sensitized solar cells (DSSCs) have been expected as low-cost, lightweight, and flexible energy conversion devices. To date, the highest conversion efficiency above 12 % has been achieved with p-conjugated macrocyclic zinc porphyrin sensitizer YD2-o-C8 using cobalt polypyridine redox shuttles. Designed p-conjugated macrocycles such as porphyrins and phthalocyanines have attracted special attention as versatile molecular platforms of highly efficient dyes for DSSCs. While a lot of porphyrin-based sensitizers have been designed and synthesized to enhance the conversion efficiency in DSSCs, the efficiencies of DSSCs employing red/near-IR absorbing phthalocyanine-based sensitizers had not been impressive due to their strong tendency to aggregate and the lack of directionality of electron transfer in the excited states. To overcome these drawbacks of phthalocyanine-based sensitizers, several approaches such as steric suppression of aggregation, electronic push-pull structures through asymmetrical substitutions, and optimization of adsorption sites have been reported. Recently, we showed that the structural modification of peripheral bulky substituents and adsorption site around the phthalocyanine core induced the improvement of incident photon-to-current efficiency (IPCE), and thereby achieved a solar-to-electric power-conversion efficiency (PCE) of 5.9% from solar cells employing PcS18 under one sun condition. However, while the maximum value of IPCE was more than 80 %, the values around 520 nm was about 30 %. Since the absorption coefficient of the sensitizers at the wavelength is very low, in order to increase the efficiency, higher dye adsorption density is desired. This can be done by decreasing the molecular size. In addition to IPCE spectrum, open circuit voltage of the PcS18 cell was not high. This could be improved by modifying the size of peripheral substituents attached to the phthalocyanine core to cover the TiO2 surface by the dye molecules. In this presentation, we examine the effect of the length and number of alkoxy groups around the phthalocyanine moiety on the photovoltaic properties. We now expect the alkoxy groups to have three functions, preventing aggregation, filling the space among dyes on TiO2 surface and increasing dye adsorption density. We found that an asymmetrical zinc phthalocyanine (ZnPc) PcS20 bearing propoxy groups in the 2 and 6 positions of peripheral phenoxy units showed a record PCE value of 6.4 % under simulated air mass 1.5 global sunlight.
Facile Synthesis of Meso-Aminoporphyrins and Their Oxidative Oligomerization
Authors: Yamashita Ken-ichi , Shouichi Takeuchi , Motoko Asano , Sugiura Ken-ichi , Kataoka Kazuyuki
Published: February 2020

Porphyrins and their metal complexes have been attracting significant attentions due to their characteristic chemical, or physicochemical properties derived from their 18π aromaticity.  Recently, nitrogen-based substituents (e.g., amino, amido, imido, imino, and azo groups) have been energetically introduced on the porphyrin periphery because of their strong influence of the p-electron system of the porphyrin.  Among them, meso-aminoporphyrins are the simplest nitrogen-substituted porphyrins.  Because of a wide variety of reactivities of the amino groups, meso-aminoporphyrins have been utilized as useful precursors for other nitrogen-substituted porphyrins.  Despite their synthetic usefulness, there have been only a few practical methods for the preparation of meso-aminoporphyrins. 

In this presentation, we present a facile and efficient synthetic method for meso-aminoporphyrins from meso-bromoporphyrins.1  This method involves the aromatic nucleophilic substitution (SNAr) of a bromo group with azide2 and the following in-situ reduction of the introduced azide group by sodium ascorbate.  A simple treatment of 10 equiv. of sodium azide and sodium ascorbate with meso-bromodiarylporphyrins affords the corresponding meso-aminoporphyrins almost quantitatively.  This reaction is easily scalable up to a gram scale without the decrease of the product yield. 

We also performed the oxidative oligomerization of meso-aminoporphyrins to afford the polyaniline-like π-conjugated oligomers.3  We will also report the synthesis, structural characterization, and redox behavior of the obtained oligomers.

 

References

(1) K. Yamashita, K. Kataoka, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation.

(2) K. Yamashita, K. Kataoka, M. S. Asano, K. Sugiura, Org. Lett.
2012, 14, 190–193.

(3) K. Yamashita, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation.

 

Figure 1
Supramolecular Assembly of Helical Porphyrin Nanostructures on Single Stranded DNA Via Directional Hydrogen Bonds
Authors: Balaz Milan
Published: February 2020

Chiral nanomaterials and metamaterials have great potential for applications in plasmonics, biological sensing, labelling, chiral memory, data storage, and optical communication. Porphyrins’ modular photophysical and structural properties, high stability, and accessible synthetic routes make them one of the most commonly utilized functional building blocks in molecular engineering. Single stranded DNA (ssDNA) represents a versatile supramolecular template, since its nucleotide sequence and structure can be easily copied into newly formed periodically arranged helical nanostructures. This lecture will present the synthesis of porphyrin-purine conjugates and their assembly into helical supramolecular porphyrin and metalloporphyrin nanostructures formed on a single stranded oligothymidine template via directional hydrogen bonding (see Figure).[1,2] We will describe how the helicity of ssDNA-templated porphyrin and metalloporphyrin nanoarrays can be controlled and switched using external stimuli to preferentially prepare left-handed and right-handed nanoassemblies. We will also present external stimuli induced, reversible switching of helical twist of ssDNA-templated porphyrin nanoassemblies. Time-dependent density functional theory (TD DFT) simulations of UV-vis and circular dichroism (CD) spectra for model porphyrin nanostacks have been used to confirm the origin of observed chiroptical properties and to assign the handedness of porphyrin nanoassemblies. We will also discuss successful use of dialysis to separate porphyrin nanoassemblies from porphyrin monomers. The chiral DNA-templated multiporphyrin nanostructures exhibited high thermal and acid/base stability: the helicity was fully preserved up to +85 °C and pH between 3 and 12. High resolution transition electron microscopy (HRTEM) has showed formation of metalloporphyrin nanoassemblies and their assembly into helical fibrils with micrometer lengths.[2]

1. G. Sargsyan, B. M. Leonard, J. Kubelka, M. Balaz, ‘Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.’
Chem. Eur. J., 2014, 20, 1878-1892 (VIP)

2. G. Sargsyan, A. A. Schatz, J. Kubelka, M. Balaz, ‘Formation and helicity control of ssDNA templated porphyrin nanoassemblies.’
Chem. Commun.
, 2013, 49, 1020-1022

Figure 1
Can Heme Modes be Influenced By Protons?
Authors: Schünemann Volker
Published: February 2020

Nuclear Resonance Vibrational Spectroscopy (NRVS) –also called Nuclear Inelastic Scattering (NIS) - is a synchrotron based technique which uses a Mössbauer active nucleus -in most cases 57Fe- to characterize iron-ligand vibrations. This method does not depend on optical selection rules; any vibrational mode involving movement of the 57Fe is NIS-active and therefore this technique is complementary to other methods including IR or Raman spectroscopy. In order to explore iron ligand vibrations in heme systems we have investigated the vibrational properties of Fe(III) containing model hemes as well as the NO-adducts of the NO-transporter proteins nitrophorin 2 (NP2) [1,2] and nitrophorin 7 (NP7) [3]. Theoretical QM/MM-calculations have been performed to understand and assign all iron-related vibrational modes in the range starting from 20 cm-1 up to 600 cm-1. Interestingly the QM/MM-calculations do also show that protonation of the heme carboxylates significantly influences the Fe-NO stretching and bending modes of the heme-NO unit [3], an effect which can be related to a change of its electronic properties.

This work was supported by the research initiative NANOKAT and the German Federal Ministry of Education and Research under 05 K13UK2.

1. B. Moeser, A. Janoschka, J.A. Wolny, H. Paulsen, I. Fillipov, R.E. Berry, H. Zhang , A.I. Chumakov, F.A. Walker, V. Schünemann, J. Am. Chem. Soc. 134(9) (2012) 4216.

2.  B. Moeser, A. Janoschka, J. A. Wolny, I. Filipov, A.I. Chumakov, F. A. Walker, V. Schünemann, Hyperfine Interact. 206(1) (2012) 19.

3. H. Auerbach, I. Faus, S. Rackwitz, J. A. Wolny, F. A. Walker, A. I. Chumakov, H. Ogata, M. Knipp, V. Schünemann, Hyperfine Interact. 226 (2014) 439.
Porpholactone and Metal Complexes: Effect of Lactonization of ß-Pyrrole
Authors: Zhang Jun-Long , Ke Xian-Sheng
Published: February 2020

The development of “porphyrin-like” molecules (porphyrinoids) and related tetrapyrroles has attracted considerable attention for the potential as optical materials and photosensitizers for photodynamic therapy (PDT). Porpholactones (TPPLs) are an important but relatively unstudied class of tetrapyrroles, which combine some of the features of porphyrins and chlorins. To explore the effect ß-Lactonization on the electronic structures and spectral properties is of importance to expand the porpholactone chemistry. In recent years, we focused on the synthesis, characterization and the application of porpholactone and their metal complexes.  Based on the skeleton of porpholactones, the β-lactone moiety provides an access to tune their NIR optical characteristics, amphilicity and cellular  behaviour. More importantly,  the relative orientation of the β-dilactone moieties significantly influences their electronic structures and photophysical properties, for example, the Qy band of trans-porphodilactone is red shifted 19 nm compared to that of the cis-isomer with a 2-fold increase in the absorption intensity. Trans-isomer exhibit much higher singlet oxygen quantum yield and the related PDT efficiency than cis-isomer upon irradiation at their Qv bands, respectively. Thus, these results reveal the importance of relative orientation of b-substituents on optical properties at NIR regions.
Mechanistic Understanding of Li Transport in Rechargeable Batteries
Authors: Shahbzian-Yassar Reza
Published: February 2020

Electrodes in rechargeable batteries undergo complex electrochemically-driven phase transformations upon driving Li ions into their structure. Such phase transitions in turn affect the reversibility and stability of the battery. It is of prime importance to better understand how Li ions transport within the host electrodes and what phase transitions are triggered during such interaction. This presentation gives an overview of the PI’s research program on in situ transmission electron microscopy (TEM) of battery materials.  Various anode materials including SnO2, Zn-Sb were subjected to lithiation process and the transport of Li ions was visualized within their atomic structure. For SnO2 nanowires, it was observed that the Li ion transport results in local strain development preferably along (200) or (020) plans and [001] crystallographic directions. Anisotropic plastic deformation was also observed along [010] directions of MnO2 nanowires. Zn-Sb alloys also exhibit a new cubic alloying phase Li2ZnSb that form by intermixing of the ABAB atomic ordering in hexagonal LiZnSb due to Li inclusion in their lattices.
Low Voltage Anodes for Lithium-Ion Batteries
Authors: Clark Steve , Armstrong Anthony Robert , Bruce Peter G
Published: February 2020

Graphite has proved a highly successful anode for lithium ion batteries; however it is not without its limitations. There is intensive research to perfect silicon based anodes but important challenges still remain in the quest for high cycling efficiency and high cycle numbers. As a result, there remains much need for investigation of alternative anodes for lithium-ion batteries. Recently we investigated anodes based on LiVO2
1,2.  Intercalation into this compound, which is isostructural with LiCoO2, occurs in a two phase process with the formation of hexagonal close packed Li2VO2.1 We have now extended these studies to related compounds, and solid solutions, and have identified anodes with a capacity of over 215 mAh/g at C rate, Fig. 1. The density of these materials is 3.34 g/cm3 resulting in a volumetric capacity of 718 mAh/cm3 at 1C. Volumetric capacity is important for applications such as electric vehicles.  Detailed results of these investigations will be presented at the meeting.

References:

1) A.R. Armstrong, C. Lyness, P.M. Panchmatia, M.S. Islam, P.G. Bruce, Nat. Mater. 10 (2011) 223-228.

2) F.d.r. Pourpoint, X. Hua, D.S. Middlemiss, P Adamson, D Wang, P.G  Bruce, C.P. Grey, Chem. Mater. 2012, 24, 2880−2893.

Figure 1