bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Scale Modeling and Experimental Characterization of Charge Process of Li-O2 Batteries: Impacts of Particle Size and Cycling History
Authors: Yin Yinghui , Gaya Caroline , Torayev Amangeldi , Thangavel Vigneshwaran , Larcher Dominique , Franco Alejandro A.
Published: February 2020

Li−O2 batteries have attracted significant attention due to their high theoretical capacity up to ~3000 Wh/kg, but they are still facing many challenges which avoid their penetration in practical applications. Their high charging voltage, which usually reaches 3.8 V and even more than 4 V, leads to problems such as poor round-trip efficiency, unfavorable parasitic reactions and a large potential gap between charge and discharge, resulting in an intrinsic loss of energy efficiency from source to end. The major part of this potential gap is due to large charge overpotential. Therefore, it is important to develop better understanding of the charge process.

In this work, a comprehensive multiscale model is reported to describe charge processes of Li−O2 batteries. On the basis of a continuum approach, the present model combines mathematical descriptions of mass transport of soluble species (O2, Li+, LiO2) and detailed elementary reactions. The decomposition kinetics of the Li2O2 particles are assumed to be morphology dependent and the simulated charge curves are in good agreement with experimental studies reported in literature previously.1 The model along with the assumed reaction mechanisms provides physical explanations for the characteristic two-step charge profiles. Moreover, since the morphology of Li2O2depends strongly on the applied current density during discharge and operation history upon cycling, the model underlines the strong link between discharge and charge processes. The experimental validation and comparison will be also discussed in the talk.

 [1] Zhai, D.; Wang, H.-H.; Yang, J.; Lau, K. C.; Li, K.; Amine, K.; Curtiss, L. A. J. Am. Chem. Soc.
2013, 135, 15364–15372.

 [2] Y. Yin, C. Gaya, A.Torayev ,V. Thangavel, A. A. Franco. J. Phys. Chem. Lett., 2016, 7 (19), 3897–3902

Figure 1
Plastic Deformation of Lithium Metal and Impact on Dendrite Growth Process
Authors: Barai Pallab , Higa Kenneth , Srinivasan Venkat
Published: February 2020

Lithium metal has attracted interest as an alternative anode material for lithium ion batteries due to its extremely low reduction potential (-3.04V with respect to standard hydrogen electrode) and very high theoretical specific capacity (3860mAh/g of Li). However, lithium dendrite growth is a major challenge preventing the widespread commercial use of lithium thin films as lithium ion battery anodes.

It has been observed experimentally that stiff protective layers are capable of preventing the growth of dendritic protrusions. In a previous article[1], the present authors investigated a dendritic protrusion into a solid polymer electrolyte/separator region. Under the assumption of elastic deformation, stress fields and their impact on the current distribution were calculated. It was found that operation at low current density did not lead to any dendrite growth. Also the stress field under the assumption of linear elastic deformation significantly exceeded the yield strength of both lithium metal and polymer electrolyte region.

Contrary to the results of this previous analysis, there are several reports of lithium dendrite growth in systems where PEO-based polymers have been used as the electrolyte[2]. Elucidation of the dendrite growth mechanism within these Li/PEO systems is the main aim of the present work, which extends the earlier model by considering i) a more realistic elastic-plastic description of lithium metal and PEO electrolyte deformation, and ii) operation at current densities close to the limiting current, at which significant concentration and potential gradients evolve according to concentrated solution theory, promoting dendrite growth through higher total current density at dendrite protrusion peaks than valleys. An electrolyte phase with a higher elastic modulus can suppress this growth by i) reducing reaction current density at the peak through increased compressive stress, and ii) reducing variations in ionic conduction path lengths by decreasing dendritic protrusion height. Based on these two mechanisms, the minimum value of the elastic modulus needed for the electrolyte phase to prevent growth of dendritic protrusions is estimated.

References:

1. Barai, P., K. Higa, and V. Srinivasan, Effect of initial state of lithium on the propensity for dendrite formation: A theoretical study. Journal of the Electrochemical Society, 2016. Accepted, In press.

2. Brissot, C., et al., Dendritic growth mechanisms in lithium/polymer cells. Journal of Power Sources, 1999. 81: p. 925-929.

Figure 1
Long Cycle Life LiFePO4 / AC Hybrid Cathodes for Lithium Ion Capacitors
Authors: Shellikeri Annadanesh , Zheng Jun-Sheng , Yturriaga Steven , Cao Wanjun , Zheng Jim P.
Published: February 2020

Energy storage devices which can bridge the gap between the energy density of Lithium ion battery and the power density of electric double layer capacitor have been gaining interest. Lithium ion capacitor (LIC), with its unique charge storage mechanism with hybrid/composite electrodes is one such device which has attracted much research recently 1, 2. We report here a Hybrid LIC consisting of a Lithium Iron Phosphate (LFP) / Activated Carbon (AC) composite cathode in a synergetic ratio combination, while elaborating on the charge sharing and transition between the faradaic and non-faradaic reactions in the hybrid device. The results from this investigation of energy and power performance, cycle life and anode effects will be presented. The preliminary results, Figure 1, show that during the cycle life study carried out at a very high C- rate of 60C, the LIC device displays a very high capacity retention with no evident capacity decay (retention of 99.99%) over 15000 cycles (ongoing), while delivering an energy density of 70 Wh/Kg act. wt.+ Li-Loading at 1C rate.

Wang B, Wang QM, Xu BH, Liu TF, Wang DL, Zhao G. The synergy effect on Li storage of LiFePO4 with activated carbon modifications. RSC Adv. 3, 20024–20033 (2013).

Shellikeri, A., Hung, I., Gan, Z., Zheng J.P. In situ NMR Tracks Real-Time Li Ion Movement in Hybrid Supercapacitor - Battery Device, J. Phys. Chem. C, 120, 6314-6323 (2016).

Figure 1
LiPF6 as Effective Etching Agent of LiMnPO4 colloidal Nanocrystals for High Rate Li-Ion Battery Cathodes
Authors: Monaco Simone , Chen Lin , Dilena Enrico , Paolella Andrea , Bertoni Giovanni , Ansaldo Alberto , Colombo Massimo , Marras Sergio , Scrosati Bruno , Manna Liberato
Published: February 2020

LiMnPO4 is an attractive cathode material for the next-generation high power Li-ion batteries, due to its high theoretical specific capacity (170 mA h g−1) and working voltage (4.1 V vs Li+/Li). Two main drawbacks prevent the practical use of LiMnPO4: (i) its low electronic conductivity and (ii) the limited lithium diffusion rate, responsible for the poor rate capability of the cathode. The use of nano-particles can alleviate the issues associated with poor ionic conductivity while the electronic resistance is usually lowered by coating the particles with a carbon layer. It is therefore of primary importance to develop a synthetic route to LiMnPO4 nanocrystals (NCs) with controlled size and coated with a highly conductive carbon layer. Here we report an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs more hydrophilic and dispersible in the aqueous glucose solution used as carbon source for the carbon coating step. The carbon coated etched LiMnPO4-based electrode exhibited a specific capacity of 118 mA h g−1 at 1C, with a stable cycling performance and a capacity retention of 92% after more than 100 cycles at different C-rates. The delivered capacities were higher than those of not etched carbon coated NCs, which never exceeded 30 mA h g−1. The adopted etching process allowed: (i) The efficient removal of the hydrophobic passivated surfactants shell, present on NCs surface after the colloidal synthesis. This increases the nanoparticles’ solubility in the aqueous glucose solution used as carbon source for NCs coating, enabling the formation of a good conductive carbon layer. (ii) The possibility to prepare composite electrodes with a reduced amount of carbon additive and polymeric binder (less than 20% wt. in total), with a consequent benefit on the energy density of LMP-based cathodes. The protocol reported here enabled the preparation of LMP/NCs-based cathodes with high rate capability and which can be charged with a fast CC−CV procedure (of maximum 2 h at 1C-rate), which is of paramount importance for the future development of high rate and high power Li-ion batteries.
(Invited) Tire-Derived Carbon Anodes for Lithium-Ion and Sodium-Ion Batteries
Authors: Paranthaman Mariappan Parans
Published: February 2020

Carbon powders recovered from waste tires are considered as one of the most promising anodes for both lithium-ion and sodium-ion batteries. The tire-derived carbons obtained by pyrolyzing the acid-treated tire at 1100 °C. The carbon interlayer distances for crystalline carbon areas were determined to be 4.7 Å. These values are ideal for lithium and sodium intercalation. When the pyrolysis temperature is increased from 1100 to 1600°C, the capacity of the plateau below 0.2 V increases dramatically and this could help increase the full cell energy density. The 1600°C treated carbon shows a capacity of 203 mAh g-1after 100 cycles with sodium-ion batteries. We will report the current status of the tire-derived carbon powder scale up efforts and its use in energy storage applications.

Acknowledgements

This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.
Influence of Electrolyte Penetration Depth and How It Affects the Electrochemical Performance of Cathodes in Zn-Air Batteries
Authors: Kube Alexander , Wagner Norbert , Friedrich K. Andreas
Published: February 2020

One of the major drawbacks of renewable energy production is that efficient energy storage is required, due to the intermittent nature of wind and solar power. The EU funded Project “ZAS – Zinc Air Secondary batteries based on innovative nanotechnology for efficient energy storage” has the goal to overcome this drawback by developing a new generation of secondary zinc-air batteries.

Zinc based metal-air batteries have the advantage of high energy density, because oxygen from ambient air is used without in-cell storage. As a consequence, lighter batteries are produced with the reversible available Zinc as the only limiting factor.

However, before Zn-air batteries can be used as secondary elements some obstacles have to be overcome. The low cyclability of state of the art Zn-air batteries is caused by the passivation rate and dendrite growth of zinc, carbonate formation in the alkaline electrolytes, corrosion of cathode materials and flooding of the cathode.

Due to the volume expansion of Zinc in alkaline Zn-air batteries, it is important to optimize the penetration depth of electrolyte into the porous structure of the cathode by an appropriate pore size distribution.

Electrochemical impedance spectroscopy measurements were conducted for different applied electrolyte pressures and correlated to the electrolyte penetration depth and the electrochemical performance.

To get a better understanding how the electrolyte infiltrates the porous structure, an electrolyte intrusion cell was build. The volume increase and decrease of the zinc during charge and discharge could be mimicked with the developed cell by electrolyte intrusion and extrusion. The effect of the pore size distribution is strongly reflected in this measurements. This test was done for electrodes at different stages of degradation, to see how the penetration characteristics change over the cycle life of the cathode and how a long life battery could be obtained. Additionally electrodes at different state of charge (SOC) were compared and, in addition, changes in hydrophilic and hydrophobic pore properties were studied.
TiO2 Supported By Acid Treated Graphene Oxide As an Oxygen Reduction Catalysts
Authors: Grewal Simranjit , Macedo Andrade Angela , Karimaghaloo Alireza , Lee Min Hwan
Published: February 2020

Renewable energy devices such as fuel cells and metal air batteries involves oxygen reduction reactions (ORR), often the performance-determining process of the device. While Pt and its alloys have been the materials of choice due to their high catalytic activity, intense efforts have been made to find alternatives due to their prohibit cost, limited availability and instability. In this presentation, we report a study of TiO2–graphene hybrid as a cost effective option and more environmentally friendly alternative ORR catalyst. While TiO2 has been rarely considered to be an effective ORR electrocatalyst, a recent study by Pei and colleagues reported that oxygen-deficient titanium dioxide rendered surprisingly competitive ORR activity and excellent durability.[1] Motivated by this work and additional advantages of TiO2-x such as abundance, safety and cost effectiveness, we probed the feasibility of applying self-doped TiO2-x based on graphene oxide (GO) to ORR catalyst. This hybrid structure leverages the extremely high surface area and excellent electronic conductivity of reduced GO, which is highly advantageous for maximizing catalytically active sites per mass.[2] Since only the wrinkles and edges of GO are populated with active sites (binding functional groups), GO was treated with acid (HBr acid and/or oxalic acid) to functionalize the non-active sites (epoxide groups) on its basal plane. HBr acid is expected to create hydroxyl groups, and additional oxalic acid treatment is used to create carboxyl groups. These functional groups are then used to bind TiO2nanoparticles. [3]

TiO2/GO hybrid materials was synthesized by a hydrothermal reaction using three different kinds of GO: as-synthesized, HBr-treated, and HBr + oxalic acid-treated GOs. For simplicity, we named the resulting hybrid materials as GT (i.e. GO-TiO2), HGT (HBr-treated GO-TiO2), and HOGT (HBr and oxalic acid-treated GO-TiO2), respectively. From a series of characterization, we found that HOGT samples show the best catalytic activity among the samples with a four electron process, whereas the other samples show a two-electron processes. It was also observed that HOGT showed the best performance when reacted at the highest temperature (160°C) unlike the other samples. From these observations, it is concluded that high density of carboxyl group is essential in rendering high performance and durability toward ORR catlysis.

This project is funded by NASA Advanced STEM Training and Research (ASTAR) Fellowship (NNX15AW57H) and NASA MUREP Institutional Research Opportunity (MIRO) Program (Grant No. NNX15AQ01A).

 

 

References

[1] Pei, D.-N. et al.
Nat. Commun. 6, 8696 (2015).

[2] Sun, Y. et al. Graphene based new energy materials. Energy Environ. Sci. 4, 1113 (2011).

[3] Chen, M. et al. Sci. Rep. 5, 10389 (2015)

Figure 1
Integrating Reverse-Electrodialysis Stacks with Flow Batteries to Achieve Improved Energy Recovery from Salinity Gradients and Energy Storage
Authors: Zhu Xiuping , Logan Bruce E. , Kim Taeyoung , Rahimi Mohammad , Gorski Christopher A.
Published: February 2020

Salinity gradient energy can be directly converted to electrical power using reverse electrodialysis (RED) and other technologies, but the power densities have been too low for practical applications. Here, an integrated RED stack and flow battery (RED-FB) system was developed to efficiently capture and store salinity gradient energy using two different redox couples (ferrocyanide and 2,6-dihydroxyanthraquinone) in the electrolytes, at an energy density of up to 2.4 kWh/m3-anolyte. These solutions were then discharged in the flow battery at a power density of up to 3.0 kW/m2-anode, which was more than 1000 times that obtained in the RED stack using NaCl alone (2.8 W/m2-anode). Salinity gradient energy captured from the RED stack was recovered from the electrolytes as electricity with a 30% efficiency. The combined RED-FB system overcomes many limitations of previous approaches to capture and store salinity gradient energy from natural or engineered sources.
Electrostatic Spray Deposition (ESD) Based Li4Ti5O12 for Nonaqueous 3D Hybrid Microsupercapacitors
Authors: Agrawal Richa , Adelowo Ebenezer , Wang Chunlei
Published: February 2020

With the recent boom in development of miniaturized electronic systems, the demand for reliable miniaturized power sources is at an all-time high. Microsupercapacitors, quite similar to their larger counterparts, can provide high power but with limited specific energy. In the wake of addressing the low specific energy of supercapacitors, the concept of battery and capacitor hybridization has garnered significant attention in recent years. Such a system typically comprises a faradaic-type battery electrode and a double layer-type capacitive counter electrode. In this work, 3D micropillars were created on 2D current collectors via conventional photolithography in order to utilize a larger surface for the given footprint. Li4Ti5O12 (LTO) and a graphene-carbon nanotube composite (G-CNT) served as the faradaic and the double-layer component, respectively for the hybrid microsupercapacitors. Both the active materials were integrated onto the 3D micropillars via electrostatic spray deposition (ESD), which is a facile process for synthesizing thin films. LTO is a well-suited candidate for hybrid capacitors given its superior capacity as compared to the conventionally used activated carbons, and zero-strain lithium insertion-extraction around 1.55V vs. lithium, whereas graphene is a well-known double layer material; small amounts of CNT were added to prevent graphene sheet aggregation and improve electronic conductivity. Both half-cell and full-cell analyses were carried out in a lithium-containing nonaqueous medium (1.0 M LiPF6 in carbonate based solvent). Detailed electrochemical results (CV, galvanostatic charge-discharge, EIS) along with material characterization (XRD, SEM, TEM, FTIR) will be presented at the conference.
Exploring the Capacitive Performance of the Transition Metal Carbonitride Mxene Ti3CNTx
Authors: Mathis Tyler , Alhabeb Mohamed , Gogotsi Yury
Published: February 2020

Transition metal carbides, nitrides, and carbonitrides known as MXenes are a growing family (20+ members) of two dimensional (2D) materials that have garnered much attention for the unique physical, electrical, and optical properties of this new class of materials[1]. Titanium Carbide (Ti3C2Tx) MXene based electrodes have shown great potential for energy storage applications due to their attractive properties such as their high specific capacitances due to redox active transition metals at their surfaces[2, 3] and the high conductivities of MXenes (5000 S/cm) when they are fabricated into free-standing, flexible films[4]. To date, relatively few MXenes have been used as electrode materials for electrochemical capacitors, all of which have been carbides.

Here we examine for the first time the electrochemical performance of a carbonitride MXene, Ti3CNTx, as a supercapacitor electrode material. The structure of Ti3CNTx is similar to Ti3C2Tx, with nitrogen and carbon layers sandwiched between three layers of titanium instead of only two layers of carbon. The Ti3CNTx investigated shows high specific capacitances in acidic electrolytes and good rate performance, similar to previous reports on Ti3C2Tx-MXenes, but the charge-discharge response of Ti3CNTx-MXene during cyclic voltammetry is completely different from carbide based MXenes. These results show how manipulation of the composition of MXenes can influence their energy storage properties.

1. Naguib, M. and Y. Gogotsi, Synthesis of two-dimensional materials by selective extraction. Acc Chem Res, 2015. 48(1): p. 128-35.

2. Lukatskaya, M.R., et al., Cation intercalation and high volumetric capacitance of two-dimensional titanium carbide. Science, 2013. 341(6153): p. 1502-5.

3. Ghidiu, M., et al., Conductive two-dimensional titanium carbide 'clay' with high volumetric capacitance. Nature, 2014. 516(7529): p. 78-81.

4. Shahzad, F., et al., Electromagnetic interference shielding with 2D transition metal carbides (MXenes). Science, 2016. 353(6304): p. 1137-1140.
Vertically Aligned Carbon Nanotube Arrays As Efficient Supports for Faradaic Capacitive Electrodes
Authors: Oguntoye Moses , Pesika Noshir
Published: February 2020

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for pseudocapacitive and faradaic capacitive electrode materials. The objective is to develop electrodes that can function in an inexpensive aqueous environment with relatively small potential windows, and still store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NixCoyOz, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT templates is more than double that obtained by direct deposition onto current collectors or by using VACNT alone as electrodes. The ease of VACNT growth and the degree of coating control that can be achieved using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

Figure 1
Modeling the Effect of the Design of Air Cooling Channels on the Thermal Behavior of a Lithium-Ion Battery Module
Authors: Lee Myoung Kyou , Koo Boram , Shin Chee Burm
Published: February 2020

The lithium-ion battery (LIB) is one of the preferred candidates for electric vehicle (EV) and hybrid electric vehicle (HEV) applications due to its outstanding characteristics such as high energy density, modular scalability, long cycle life, and low self-discharge rate among others. In a battery module for EV applications, an uneven temperature distribution in the module can be created depending on the operating conditions and the types of thermal management. Uneven temperature distribution in a module could cause an electrical imbalance and thus lead to the lower performance and shorter life of battery. Therefore, it is important to calculate accurately the uneven temperature distribution in a battery module in order to achieve the optimum performance and long life of the battery module.

In this work, a three-dimensional modeling is performed to investigate the effects of the design of air cooling channels on the thermal behavior of an LIB module. Thermal conductivities of various compartments of the battery are estimated based on the equivalent network of parallel/series thermal resistances of battery components. Heat generation rate in an LIB cell is calculated by using the modeling results of the potential and current density distributions of a battery cell.

Fig. 1 shows the schematic diagram of the battery module composed of 24 cells with two types of air cooling channels. The average temperatures from the experimental measurement for the LIB module for US06 cycle profile are compared with those predicted by the modeling in Fig.2.

Figure 1
Modification and Activation of Graphite Felt-Based Electrodes for Vanadium Redox Flow Battery with Enhanced Performance
Authors: Chou Yi-Sin , Jeng King-Tsai , Yen Shi-Chern
Published: February 2020

Vanadium redox flow battery (VRFB) is a very promising electrical energy storage device (EES), particularly for use with intermittent-type renewable energies. In operation, the commonly used graphite felt (GF)-based electrode has to be modified and activated to generate a proper electrode reaction condition before use. This study proposes a novel modification and activation approach, mainly by impregnation treatment using a Nafion® ionomer solution, which effectively renders the electrode surface a needed hydrophilic environment. Various instrumental characterizations are carried out. The cyclic voltammogram (CV) of the ionomer-treated GF electrode, designated as N90, obtained in a 2M H2SO4 solution containing 0.8M V(III) and 0.8M V(IV) ions, respectively, demonstrates a wider electrochemical window and more pronounced redox signals than those of electrochemically oxidized counterpart. It shows that the ionomer is partially but uniformly coated on the graphite felt fibers after it is put into operation. In addition, the N90 electrode is found to be more resistant to corrosion and crystalline salt formation. Moreover, the prepared single-cell VRFB exhibits a good performance without the need of using any catalyst and the electrolyte unbalance phenomenon of the cell is substantially alleviated. The redox reaction mechanisms on both electrodes are proposed.
Redox-Active Organic Electrodes for Pseudocapacitor Applications
Authors: Liu Tianyuan , Lee Byeongyong , Lee Seung Woo
Published: February 2020

Current lithium-ion battery technology depends on inorganic cathode materials, such as LiCoO2 and LiFePO4. However, large-scale energy storage applications, including renewable energy storage and load-leveling, require more sustainable and cost-effective electrode materials. Organic electrode materials have been studied owing to their potential advantages, including the use of earth-abundant sources, environmental friendliness, and high energy density.1 We also have been investigating various redox-active organic electrodes by utilizing dopamine,1 pyrene derivatives,2 and glucose.3 Here, we further investigate the charge storage properties of the biomass-derived carbonaceous materials with Li- and Na-ions. We reveal that the synthesized carbonaceous materials can exhibit high capacities over 180 mAh/g in both Li- and Na-ions by based on double layer capacitance and redox reactions. These carbonaceous materials can be fabricated as the composite electrodes by mixing with conductive nanocarbons, including carbon nanotubes or reduced graphene oxides. These carbon-based composite electrodes show a high rate-capability and remarkable cycling stability. These high-performance organic electrodes could be promising candidates for developing large-scale energy storage devices.

References

1. T. Liu, K. C. Kim, B. Lee, Z. Chen, S. Noda, S. S. Jang and S. W. Lee, Energy & Environmental Science, DOI: 10.1039/C6EE02641A (2017).

2. J. C. Bachman, R. Kavian, D. J. Graham, D. Y. Kim, S. Noda, D. G. Nocera, Y. Shao-Horn and S. W. Lee, Nature Communications, 6:7040 (2015).

3. T. Y. Liu, R. Kavian, Z. M. Chen, S. S. Cruz, S. Noda and S. W. Lee, Nanoscale, 8, 3671 (2016).
(Invited) Modification of Lithium-Ion-Containing [60]Fullerene: Synthesis and Successful Preparation of Each [5,6]- and [6,6]-Isomer
Authors: Matsuo Yutaka , Okada Hiroshi , Ueno Hiroshi , Aoyagi Shinobu
Published: February 2020

Lithium-ion-containing [60]fullerene, Li+@C60, is a highly electron accepting material, which have been utilized in electron transfer chemistry, supramolecular chemistry, photovoltaics, singlet oxygen generation, and so on. Considering what chemical modification of fullerene has played in, that for Li+@C60 would be a significant step for further functionalization of this compound.[1-7] In addition, chemical modification of Li+@C60 can solve this compound's drawback of low solubility in organic solvents due to rock salt packing of [Li+@C60][PF6
–].

Li+@C60 was modified with diphenyl(diazo)methane as an easily available diazoalkane to obtain lithium-ion-encapsulated [5,6]- and [6,6]-diphenylmethano[60]fullerenes, Li+@C61Ph2. Successful separation of each [5,6]- and [6,6]-isomer was performed with a positive-ion exchange columns. Both [5,6]-open and [6,6]-closed structures of Li+@C61Ph2 were determined with X-ray crystallographic analysis.

Figure 1
(Invited) Efficient Fullerene-Based Electron Acceptors for Planar Perovskite Solar Cells
Authors: Xie Su-Yuan
Published: February 2020

Discovery of organic-inorganic hybrid perovskites ignites the dream of next-generation solar cells fabricated by low-cost solution processing. To date, fullerene derivative [6,6]-phenyl-C61- butyric acid methyl ester (PC61BM), is the most prevalently used electron transport material (ETM) for high efficiency inverted planar heterojunction (PHJ) perovskite solar cells. Compared with PC61BM, pristine fullerenes, such as C60 and C70, have shown superiority of higher electron mobility and much lower costs. Due to the poor solubility and strong tendency to crystallize for pristine fullerenes in solution process, it is still a challenge to deposit compact and continuous film of pristine fullerenes for inverted PHJ perovskite solar cells by solution processing. Herein, solution processed pristine fullerenes (C60 and C70) were used as ETMs to replace PC61BM in inverted PHJ perovskite solar cells with high performance and enhanced stability. Power conversion efficiency of 14.04% was obtained by using mixture of C60 and C70 as ETM, which is comparable to that of PC61BM-involving device (13.74%). We demonstrated that the strong tendency of pristine fullerenes to crystallize on solvent removal can be largely mitigated by mixing different kinds of pristine fullerenes, with implication about a promising future of pristine fullerenes as ETMs for high performance perovskite solar cells.
(Invited) Effect of Covalent Chemistry on the Electronic Structure and Properties of the Carbon Allotropes
Authors: Bekyarova Elena , Chen Mingguang , Tian Xiaojuan , Moser Matthew , Li Wangxiang , Li Guanghui , Itkis Mikhail E
Published: February 2020

Covalent chemistry exerts characteristic changes to the geometric and electronic structures of the carbon allotropes associated with modification of the conjugation. There are two limiting cases: (a) conventional addition chemistry leading to the formation of σ-bonds to the graphitic surface in which there is full rehybridization of the derivatized carbon atoms from sp2 to sp3; in this case the carbon atoms are removed from conjugation (destructive rehybridization) and (b) covalent chemisorption with formation of an organometallic hexahapto-metal bond that largely preserves the graphitic band structure (constructive rehybridization). 1, 2

We focus our discussion on the organometallic chemistry of the carbon allotropes and the possibility to electronically interconnect graphitic surfaces by means of covalent bonding. This mode of functionalization allows the formation of atomic scale interconnects that consist of bis-hexahapto-metal-bonds between benzenoid ring systems and it may be used to increase the dimensionality of the electronic structure of the materials leading to enhanced conductivity. We will discuss the effect of bis-hexahapto bond formation on the electronic properties of percolating networks of single walled carbon nanotubes, small scale graphite nanoplatelets and graphene.

1. Bekyarova, E.; Sarkar, S.; Wang, F.; Itkis, M. E.; Kalinina, I.; Tian, X.; Haddon, R. C., Effect of Covalent Chemistry on the Electronic Structure and Properties of Carbon Nanotubes and Graphene. Acc. Chem. Res.
2013, 46, 65-76.

2. Bekyarova, E.; Niyogi, S.; Sarkar, S.; Tian, X.; Chen, M.; Moser, M. L.; Ayub, K.; Mitchell, R. H.; Haddon, R. C., Stereochemical Effect of Covalent Chemistry on the Electronic Structure and Properties of the Carbon Allotropes and Graphene Surfaces. Synth. Met.
2015, 210, 80-84.
(Invited) Synthesis and Characterization of Unprecedented D2h
-Symmetrical Trans-1-(S,R,R,S-bis-pyrrolidine)-Tetra-malonate Hexakis Adducts of C60
Authors: Castro Edison , Hernandez Andrea , Azmani Khalid , Liu Shuming , Rodríguez-Fortea Antonio , Poblet Josep M. , Echegoyen Luis
Published: February 2020

The unique chemical and physical properties of fullerenes and their derivatives is mainly the result of their unique electron accepting abilities and their high charge transport capabilities in three dimensions. The octahedral arrangement of the addends in hexaadducts of C60 is unique in organic chemistry. However, stereo-chemically controlled functionalization of fullerenes has been scarcely addressed so far. Here we report the synthesis and characterization of unprecedented D2h
-symmetrical trans-1-(S,R,R,S-bis-pyrrolidine)-tetra-malonate hexakis adducts of C60, employing the topologically controlled method introduced by Krӓutler et al., followed by a 1,3-dipolar cycloaddition reaction.

Figure 1. Synthesis of D2h
-symmetrical trans-1-(S,R,R,S-bis-pyrrolidine)-tetra-malonate hexakis adducts of C60.

Figure 1
(Invited) Stereodivergent-at-Metal Synthesis of [60]Fullerene Hybrids
Authors: Vidal Sara , Filippone Salvatore , Martín Nazario
Published: February 2020

The preparation of chiral metal complexes and, specifically, chiral at metal complexes, is a highly sought after goal in current organometallic chemistry due to its relevance in enantioselective metal-mediated processes.1.

Despite the wealth of metal-fullererene hybrids reported to date, only a few are optically actives.2 To the best of our knowledge, only a single case presents a stereogenic metal center,3 while in all of them the chiral information stems from the stoichiometric use of other chiral ligands.4 In this regard, the use of asymmetric organo- and metal-catalysis in fullerene chemistry has provided an easy access to optically active derivatives through a precise stereocontrol in the newly formed asymmetric carbon atoms.5 Conversely, the control of the metal-centered chirality is not a trivial issue due to the configurational lability of the metals that often undergo rapid ligands exchange.1

In this communication, we report the first enantioselective synthesis of fullerene hybrids endowed with a stable stereogenic metal center whose configuration can be defined at will by the proper chiral catalyst choice. In these reactions, iridium, rhodium and ruthenium pyrrolidino[3,4:1,2][60]fullerene half-sandwich complexes with four new stereocenters are formed, namely the two C-2 and C-5 chiral car bons at the pyrrolidine ring, the asymmetric nitrogen atom and the transition metal center (Scheme). The suitable functionalization and stereochemistry of the chiral fullerene ligand determine the final configuration of the metal center. Interestingly, the chiral metal center does not undergo any epimerization process as evidenced by temperature dependent NMR analysis as well as by DFT theoretical calculations.6

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2012, 41, 3153-3167.

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Asian J.
2007, 2, 358-366.

V. I. Sokolov, V. V. Bashilov, F. M. Dolgushin, N. V. Abramova, K. K. Babievsky, A. G. Ginzburg, P. V. Petrovskii, Tetrahedron Lett.
2009, 50, 5347-5350.

a) S. Filippone, E. E. Maroto, A. Martín-Domenech, M. Suárez, N. Martín, Nat. Chem.
2009, 1, 578-582; b) E. E. Maroto, M. Izquierdo, S. Reboredo, J. Marco-Martínez, S. Filippone, N. Martín, Acc. Chem. Res. 2014, 47, 2660-2670.

J. Marco-Martínez, S. Vidal, I. Fernández, S. Filippone, N. Martín, Angew. Chem. Int. Ed.,
2017, accepted for publication.
(Invited) Polypeptides As Complexing Units
Authors: Solladie Nathalie
Published: February 2020

One of our research field concerns porphyrin-functionalized a-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.1

In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short α-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.1 Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy.

The right-handed 310 helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US), which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire.

The properties of our peptides with pendant porphyrins were studied extensively in collaboration with with Professor S. Fukuzumi (Univeristy of Osaka, Japan) and applications were found as organic photovoltaic cells,2 multiple photosynthetic reaction centers3 and for the successful purification of Single-Walled Carbon Nanotubes.4

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research.

References

W. Kühlbrandt, Nature
1995, 374, 497-498.

T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater.
Chem.
2007, 39, 4160-4170.

S. Fukuzumi, K. Saito, K. Ohkubo, V. Troiani, H. Qiu, S. Gadde, F. D’Souza and N. Solladié, Phys.
Chem. Chem. Phys.
2011, 13, 17019-17022.

 Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama, Shunichi Fukuzumi, J. Phys. Chem. C
2007, 111, 1194-1199.

Figure 1
(Invited) Subphthalocyanine-Fullerene Conjugates
Authors: Torres Tomas , Zango German , Mariñas Victor , Carrascosa Hector , Lavarda Giulia , Medina Diana Paola , Muñoz Nicolas , Trukhina Olga , Rodriguez-Morgade M. Salome , Martínez-Díaz M. Victoria
Published: February 2020

An approach for employing SubPcs and SubPc fused dimers [1] as active units in molecular recognition of fullerenes and artificial photosynthetic systems has been developed. Thus, the preparation of multi-SubPc systems constituted by SubPc and SubPc fused dimer units connected by their mutual axial positions has been explored. For this purpose, a series of SubPcs and SubPc dimers bearing different conjugated spacers linked by alkyne bonds to the SubPc or SubPc dimer boron atoms have been synthesized. Two multi-SubPc hybrids comprised of a perfluorinated SubPc fused dimer (syn or anti topoisomer) axially functionalized with unsymmetrical octylthio-substituted SubPcs linked through their periphery by ethynyl linkers to the boron atoms of the dimer have been prepared. Electrochemical and steady state photophysical studies of the syn- hybrid suggest the existence of an electron transfer process from SubPc units to photoexcited SubPc dimer to generate a (SubPc•+-SubPc Dimer•-) radical pair.

Furthermore, the position that the two axial SubPc units acquire in this assembly gives rise to unique supramolecular recognition sites suitable for the complexation of fullerenes. Thus, the binding ability of this hybrid towards different fullerene derivatives, namely C60
, C70
, C60-PCBM and C70-PCBM, has been analyzed through UV-vis absorption, fluorescence and NMR titrations. It has been demonstrated that syn-compounds display a unique fullerene complexation mode. Initially, the formation of a 1:1 supramolecular complex, where the axial octylthio-substituted SubPcs embraces a guest molecule with remarkable association constants of around 106 - 104 M-1, is observed. The spatially-defined cavity generated by the rigid and short alkynyl linkers shows a higher affinity for the bigger fullerene derivatives. Then, a secondary supramolecular interaction between the perfluorinated SubPc syn dimer unit and another fullerene molecule has been detected and quantified, with significant binding constants of 104-103 M-1 that depend on the size and the host-guest electrostatic interactions, leading to the formation of the final 1:2 supramolecular ensemble [2].

Pristine and endohedral fullerene-subphthalocyanine conjugates [3,4] both covalent and supramolecular have been also prepared and studied as artificial photosynthetic systems.

[1] C. G. Claessens, D. González-Rodríguez, M. S. Rodríguez-Morgade, A. Medina, T. Torres, Chem. Rev.
2014,
114, 2192–2277.

[2] G. Zango, M. V. Martínez-Díaz, T. Torres, in preparation

[3] L. Feng, M. Rudolf, O. Trukhina, Z. Slanina, F. Uhlik, X. Lu, T. Torres, D. M. Guldi, T. Akasaka, Chem. Commun.
2015,
51, 330-333.

[4] M. Rudolf, O. Trukhina, J. Perles, L. Feng, T. Akasaka, T. Torres, D. M. Guldi, Chem. Sci.
2015,
6, 4141-4147.
(Invited) 3D Fullerene - Based Metal Organic Frameworks
Authors: Suarez Catalina , Echegoyen Luis
Published: February 2020

Hydrogen constitutes an alternative energy source due to its abundance and environmental friendliness. Due to their porosity and high surface area, Metal Organic Frameworks (MOFs) exhibit promising hydrogen storage properties. On the other hand, it has been shown that fullerene-based frameworks can exhibit molecular H2 binding in the range established by the Department of Energy (DOE) – 8.0-9.2wt%. The incorporation of fullerenes as integral components of the organic linkers in a 3D MOF should result in a porous material with high hydrogen storage capacity. For this purpose, we designed three different fullerene derivatives with terminal carboxylic acids (Figure 1), which are excellent candidates to bind to metallic Zn to result in the formation of 3D MOF structures. We report the synthesis and characterization of compounds A, B and C (Figure 1). For the synthesis of the three different compounds, we used the previously reported orthogonal transposition method to control regioselectively the addition of the different COOH containing addends to the C60 cage. Compounds A, B and C were characterized by 1H-NMR, MALDI-TOF and UV-Vis absorption spectroscopy. By slow diffusion of triethylamine into a solution of compound A in N,N-Diethylformamide, we obtained an insoluble yellow powder. The resulting compound was characterized using IR spectroscopy, thermogravimetric analysis (TGA) and powder X-Ray diffraction (PXRD). Our results suggest that compound A was incorporated as an integral linker in a porous fullerene based extended network and the 3D structure was computed using molecular mechanics. Compounds B and C will be used as the struts to build a 3D-Structure. After the assembly and characterization of the different 3D MOFs, gas storage properties will be studied.

Figure 1
(Invited) Multichromophoric Perylenediimide-Silicon Phthalocyanine-C60 System As an Artificial Photosynthetic Analogue
Authors: Sastre-Santos Ángela , D'Souza Francis
Published: February 2020

Sequential photoinduced energy transfer followed by electron transfer and the formation of charge separated states, which are primary events of natural photosynthesis, have been demonstrated in a newly synthesized multichromophoric covalently linked triad, PDI-SiPc-C60. The triad was comprised of a perylenediimide (PDI) that primarily fulfils antenna functionality and electron acceptor; silicon phthalocyanine (SiPc) as an electron donor; and fulleropyrrolidine (C60) as a second electron acceptor. The multi-step convergent synthetic procedure developed here produced good yields of the triad and control dyads, PDI-SiPc and SiPc-C60. The structure and geometry of the newly synthesized donor-acceptor systems were established from spectral, computational and electrochemical studies with the help of appropriate control compounds. Ultrafast energy transfer from 1PDI* to SiPc in the case of PDI-SiPc and PDI-SiPc-C60 was witnessed. Energy level diagram established from spectral and electrochemical data suggested formation of two types of charge separated states, viz., of PDI-SiPc•+-C60
•- and PDI•--SiPc•+-C60 from the 1SiPc* in the triad; and that generation of the latter is energetically more favourable. However, photochemical studies involving femtosecond transient spectroscopy revealed formation of PDI-SiPc•+-C60
•- as a major charge separation product. This observation has been rationalized to the spatial closeness of C60 compared to PDI in the triad. The charge separated state lasted for a few nanoseconds prior to populating the 3SiPc* state during charge recombination.[1]

Acknowledgments

This work was supported by the Spanish Ministry of Economy and Competitiveness (Mineco) of Spain (CTQ2014-55798-R to ASS), Generalitat Valenciana (Prometeo 2012/010 to ASS) and National Science Foundation (Grant No. 1401188 to FD).

References

1. L. Martín-Gomis, F. Peralta-Ruiz, M. B. Thomas, F. Fernández-Lázaro, F. D’Souza, Á. Sastre-Santos. Chem. Eur. J.
2016, in press.

Figure 1
(Invited) Electron Donor-Nanocarbon Electron Acceptor Composites Linked with Oligophenylene Bridge
Authors: Imahori Hiroshi
Published: February 2020

During the last few decades, considerable efforts have been made toward the construction of donor–acceptor (D–A) linked systems that efficiently cause photoinduced charge separation, a fundamental step in natural photosynthesis and solar energy conversion. Among the building units for such D–A systems, nanocarbons deserve a special mention because it shows notable electronic conductivity, tenacious mechanical strength, and huge specific surface area. These singular properties place nanocarbon-based D–A systems in an attractive position as the next-generation material for energy-conversion devices such as solar fuels and organic photovoltaics. With this in mind, a variety of studies have been done to synthesize covalently linked systems of electron-accepting nanocarbons with electron-donating units such as pyrenes, porphyrins and phthalocyanines. However, the D–A interface frequently undergoes a rapid relaxation of the partially charge-separated (CS) exciplex or the completely CS state to the ground state, failing to generate a long-lived CS state that is crucial for solar energy conversion. In-depth understanding of the correlation between the structure and photodynamics of the electron donor-nanocarbon electron acceptor linked systems is important for extracting the full potential of such D–A materials for the potential applications.

In this talk I will show an overviw of our recent achievements related with photodynamics of pyrene- and porphyrin-attached chemically converted graphenes linked with oligophenylene bridge.

[1] T. Umeyama, J. Baek, Y. Sato, K. Suenaga, F. Abou-Chahine, N. V. Tkachenko, H. Lemmetyinen, and H. Imahori, Nat. Commun., 6, 7732 (2015).

[2] T. Umeyama, J. Baek, J. Mihara, N. V. Tkachenko, and H. Imahori, Chem. Commun., in press.

[3] T. Umeyama, T. Hanaoka, J. Baek, T. Higashino, F. Abou-Chahine, N. V. Tkachenko, and H. Imahori, J. Phys. Chem. C, in press.