bluuebunny/crossref_metadata_2025_split huggingface dataset:
Positive – Positive Symmetric Cell Study on the Compatibility of Different Electrolyte Additives with Li[Ni0.6Mn0.2Co0.2]O2
Authors: Liu Yulong , Dahn Jeff R 
Published: February 2020

Electrode/electrolyte compatibility plays a critical role to increase the energy density and longevity of lithium-ion cells. A sound understanding of the interactions between electrode and electrolyte allows us to design better electrolyte formulation with more suitable additives. Nevertheless, the study of electrode/electrolyte interaction is difficult to carry out in a full lithium-ion cell due to the interactions between positive and negative electrodes, such as the migration of oxidation products and dissolved transition metal to the negative electrode1, and the effect of different negative electrodes on the surface layer composition of positive electrode2. In recent years, there has been quite a few experimental techniques developed aiming to solve this problem3,4. Among them, symmetric cells are excellent test vehicles where performance is exclusively determined by the compatibility of the electrode of interest with the electrolyte of choice.
In this study, the compatibility of two electrolyte additives, vinylene carbonate (VC) and prop-1-ene-1,3-sultone (PES), with uncoated polycrystalline Li[Ni0.6Mn0.2Co0.2]O2 were studied using positive-positive symmetric cells with electrodes hand-made from powder. Each symmetric cell was constructed with one fresh electrode and one delithiated electrode prepared using a coin-cell half cell. These symmetric cells were then cycled at 40oC with 10 cycles of C/10 followed by 1 cycle of C/30 repeatedly between ±0.9 V, ±0.8 V, ±0.7 V, ±0.6 V, ±0.5 V, which correspond to half cell voltages of 4.39 V, 4.35 V, 4.29 V, 4.22 V and 4.15 V vs. Li/Li+, respectively. It was found that for all symmetric cells cycled with the chosen voltage cut-offs, the cells containing VC showed better capacity retention compared to those with PES. This is surprising because in full Li-ion cells operated above 4.3 V, the opposite was found to be true by Lin Ma et al. 5

The symmetric cell building method in this work can also be used to study electrode/electrolyte compatibility when machine-made electrodes are not readily available to researchers.

References

A. J. Smith, J. C. Burns, D. Xiong, and J. R. Dahn, J. Electrochem. Soc., 158, A1136 (2011)

E. Björklund, D. Brandell, M. Hahlin, K. Edström, and R. Younesi, J. Electrochem. Soc., 164, A3054–A3059 (2017)

D. J. Xiong et al., J. Electrochem. Soc., 164, A340–A347 (2017)

C. Shen et al., J. Electrochem. Soc., 164, A3349–A3356 (2017)

Lin Ma et al, J. Electrochem. Soc. 161, A2250-A2254, (2014).

Figure 1
Evidence of Direct Link between Side Reaction and Capacity Fading in Lnmo
Authors: Dumaz Philippe , Rossignol Cécile , Bouchet Renaud 
Published: February 2020

Since their market introduction in 1991, lithium (Li)-ion battery is the main solution to power electronic portable devices, and after almost three more decades of development this technology is embedded in modern electric and hybrid cars. However, its maturity leaves little gap to increase its energy density in the order of 250 Wh.kg-1. In order to increase their energy density, a promising solution is to use positive materials with high potential (up to 5V vs Li + / Li) [1] . The spinel LiNi1/2Mn3/2O4 which owns a capacity of 147 mAh/g and a potential of 4.8 V vs Li + / Li, enables to reach a high energy density (at least 20% higher than the state of the art Li-ion technology), However, this operating potential is largely above the electrochemical stability range of conventional electrolytes based on carbonate solvents [2] . Cycling tests reveals a low coulombic efficiency induced by electrolyte oxidation and capacity loss induced by material degradation [3] . A simple model based on coulombic
efficiency has been developed to quantify the solvent decomposition current. By comparing values obtained on thin film and composite electrode, we proved that the electrolyte oxidation mainly happen on the surface of the LNMO, with a main reaction that can simply be written as: Li + + EC + NMO → EC + + LiNMO where EC stand for a solvent electrolyte molecule and EC+ the product of the solvent oxidation.
The rate of solvent decomposition is kinetically controlled by the charge-transfer, therefore a simple anodic Tafel expression has been used to model the current density due to this mechanism and has been compared to our model based on coulombic efficiency. Tests at different C rates indicate that the longer the electrode stays at high potential, the higher is the capacity fading, showing that the product of electrolyte oxidation seems to be involved into material degradation. In order to get a more deep insight into these parasitic reactions (oxidation of the electrolyte, active material degradation), cells were tested at different temperatures (10, 25 and 50°C). Especially, we have obtained that coulombic efficiency is strongly improved when the operation temperature is decreased, in full agreement with thermal activation of the electrolyte decomposition Inter estingly, we obtained a lower capacity fading which demonstrates the strong link between faradic efficiency (electrolyte oxidation) and material degradation.
[1] Tarascon et al. Nature Mater. 2011
[2] Yi et al. J. Power Sources, 2016
[3] Pieczonka al. J. of Phys. Chemistry, 2013
In Situ NMR Measurements of Lib Electrolytes -Revealing the Network of Reactions in a Battery
Authors: Wiemers-Meyer Simon , Winter Martin , Nowak Sascha 
Published: February 2020

The class of lithium ion battery (LIB) electrolytes most commonly used nowadays is under investigation for at least two decades. These electrolytes, consisting of organic carbonates and LiPF6, are known to undergo not only electrochemical reactions due to their limited electrochemical stability but also chemical reactions due to their sensitivity to hydrolysis. The interplay of chemical and electrochemical reactions as well as their interactions with cathodes, anodes and their surfaces are not yet fully clarified. To study these reactions different analytical techniques can be applied. This usually requires an extraction of the electrolyte from the battery involving a high risk of sample alterations due to volatile and highly reactive substances.
To overcome this issue a battery cell set-up for in situ NMR measurements of liquid electrolytes has been developed.1 It enables non-invasive investigations providing molecular information from the inside of an intact battery. The cylindrical battery cell consists of two electrodes in a heat-sealed polymer tube that is small enough to be placed in a standard 5 mm NMR glass tube (see Figure). To ensure gas tightness the NMR glass tubes are sealed with epoxy resin. All the common electrode materials including transition metal oxides, graphite as well as lithium metal can be applied as active electrode materials.
Electrochemical tests demonstrate a sufficient rate performance and a good cycling stability of the in situ cells. NMR measurements of the cells provide well-resolved spectra not distorted by the solid battery components. Furthermore, it can be shown that a loss equal or less than 0.1 % of the working electrode capacity by a one-electron reaction forming hydrogen or fluorine containing compounds is sufficient to reach the limit of detection (capacity: 1 to 6 mA h, 400 MHz NMR spectrometer). Hence, the sensitivity of this method is considered high enough to detect any significant electrochemical formation of soluble compounds exhibiting clear 1H or 19F NMR signals.
The results so far show that the in situ cells enable investigations on the passivating properties of the solid electrolyte interphase on the anode (SEI) by monitoring the formation of compounds electrochemically formed on the anode. Furthermore, they revealed temperature and potential dependent fluorination reactions of electrolyte solvents on the cathode surface. In addition, the measurements provide insight into reactions of the electrolyte that probably influence the SEI and are preventable by the cathode depending on the cathode material and processing. NMR spectroscopy also offers a method to investigate transition metal dissolution from the cathode active material since paramagnetic species, e.g., Mn2+, Ni2+ and Co2+ have a strong impact on the relaxation of nuclear spin magnetization.
1) S. Wiemers-Meyer, M. Winter and S. Nowak, Phys. Chem.
Chem. Phys, 2017, 19, 4962-4966.

Figure 1
The Forgotten Concept of the Three-Phase Boundary
Authors: Petrovic Slobodan , Garche Juergen 
Published: February 2020

The safety and overall operation of lithium metal batteries depends largely on the prevention of lithium dendrite build. Numerous methods have been proposed for dendrite suppression such as use of external pressure, modification of the nucleation sites for dendrite initiation and the use of solid electrolytes. Each of these approaches shows promise, but neither has led so far to a practical solution. A conceptually different design approach involves the use of high-surface area, 3D structures. Electrodes built on the principle of porous or three-dimensional substrate enable low current densities, while still offering high overall current. The low current density in turn enables long Sands time and prolonged lithium deposition without dendrite build. The entire concept relies on the creation of a high-surface area current collector in direct contact with both the electrolyte and the active material. This is the, often forgotten, principle of the three-phase boundary. The principles of creating large three-phase boundary are used to design the pore structure and to balance the distribution of the electrode components. While the effective design of the three-phase boundary is critical for both charge and discharge reactions in the lithium metal battery, it’s principles are more obvious during the discharge reaction. It is demonstrated how the effective three-phase boundary affects the cell performance.
A high-surface area porous silicon current collector is used for the metal silicon anode as well as for the air cathode. The study depicts the fundamental behavior and dependence of lithium dendrite build on the current density at the anode. Cycling of a symmetrical cell demonstrates stable voltage and current, with no capacity fade, i.e., no dendrite build, for C rates below a critical value. Figure 1 depicts stable capacity during cycling, while figure 2 shows reduction in impedance as the cycling progresses.
Further suppression in dendrite creation is demonstrated through the geometrical effects of the structure as well as by modifying the nature of the current collector. The application of this 3D structure for the air cathode is also evaluated and modeled.
Molecular Dynamics Simulations of Ionic Diffusion in PEO-LiTFSI Polymer Electrolyte: Effect of Temperature, Molecular Weight, and Ionic Concentration
Authors: Merinov Boris V , Brooks Daniel J , Goddard William A 
Published: February 2020

Polymer electrolytes are promising materials for development of the next generation of energy storage devices, including lithium-ion polymer batteries, due to their exceptional chemical and mechanical stability, high energy density and long lifetimes. Understanding the ionic diffusion mechanism in polymer electrolytes is critical to the development of advanced lithium-ion batteries. A molecular dynamics-based characterization of structures and diffusion in poly(ethylene oxide) (PEO) with lithium and bis(trifluoromethy-sulfonyl-imide) (TFSI) ions imbedded into the PEO structure have been performed across a range of temperatures, molecular weights and ion concentrations, with relative ionic diffusion coefficients shown to be in good agreement with experimental measurements. To determine details of the atomistic diffusion mechanism, the chain coordination of Li atoms, polymer motion, and temperature dependences of the intrachain and interchain diffusion contributions into the total ionic diffusion coefficients on ionic concentration and molecular weight were analyzed. We find that the most diffusive Li atoms exhibit frequent interchain hopping, whereas the least diffusive Li atoms rather oscillate or “shift” coordination between two or more polymer chains. These shifts may actually reduce the segmental motion of the PEO-LiTFSI polymer, which is important for the fast lithium-ion diffusion. Good agreement between experiment and theory validates the approach and methodology used in this study and its further applications for predicting the structure and ionic conductivity of new advanced polymer materials for a new generation of electrochemical devices.
Acknowledgement
This work was supported by Bosch Energy Research Network Grant No. 13.01.CC11.
The Influence of State-of-Charge on Ageing in Commercial Li-Ion Pouch Cells
Authors: Wikner Evelina , Thiringer Torbjörn , Scheers Johan 
Published: February 2020

Vehicle manufacturers are increasingly electrifying their vehicles using Lithium-ion batteries (LiBs) as the energy storage unit. With a very high battery cost, the requirements on LiB life and performance are necessarily stringent and much effort goes into understanding how these properties are influenced by the conditions of use. For electric vehicles a large State-of-Charge (SOC) operation window has to be balanced with the lifetime expectancy. Being able to correlate load cycles to a specific type of ageing is crucial to understand how to better utilize the LiBs - improving the accuracy of lifetime predictions and optimizing the performance/lifetime balance in the vehicle.
A physics-based ageing model of a commercial Li-ion pouch cell with a graphite anode and a blended LMO/NMC cathode has been developed. The model is based on the Newman theory [1], as implemented in COMSOL [2-6], and is a direct continuation of the work in [6]. The growth of a solid electrolyte interphase (SEI), resulting in increased resistance and capacity loss, constitutes the main ageing mechanisms of the model, which has been tuned with experimental test data as input. The SEI growth has also been linked to a change in active material porosity and thereby a reduced electrolyte volume in the electrode. The resulting effect on the cell resistance and capacity during various test conditions is determined, and the impact from the different ageing parameters evaluated.
The experimental tests used synthetic load cycles for various C-rates, at different Depth of Discharge (DOD) and at different SOC. The results show an expected increased ageing with C-rate, but more surprising is the ageing patterns seen for small DOD, at various SOC intervals, which do not follow the trend observed for LiBs with LFP cathodes [7]. The LiB here degrade most strongly at high SOC (> 60%), in accordance with previous research, while at SOC < 30% ageing is impressively slow. The slow capacity degradation of the cells in SOC intervals < 30% make their cycle lifetime more than 3x longer compared to the cells run at high SOC. The developed ageing model can successfully capture the difference in capacity loss due to larger SEI growth at high SOC.

References:

[1] M. Doyle, T.F. Fuller, J. Newman, J. Electrochem. Soc. 140 (1993) 1526-1533.
[2] H. Ekström, G. Lindbergh, J. Electrochem. Soc. 162 (2015) A1003-A1007.
[3] P. Ramadass, B. Haran, P.M. Gomadam, R. White, B.N. Popov, J. Electrochem. Soc. 151 (2004) A196-A203.
[4] R. Darling, J. Newman, J. Electrochem. Soc. 145 (1998) 990-998.
[5] S. Santhanagopalan, Q. Guo, P. Ramadass, R. E. White, J. Power Sources 156 (2006) 620-628.
[6] E. Wikner, Lithium ion Battery Aging: Battery Lifetime Testing and Physics-based Modeling for Electric Vehicle Applications, Chalmers University of Technology, Göteborg, 2017.
[7] J. Groot, State-of-Health Estimation of Li-ion Batteries: Ageing Models, Chalmers University of Technology, Göteborg, 2014.
Charge Transport and Practical Applications of All-Carbon Molecular Electronic Devices
Authors: Supur Mustafa , Najarian Amin , Bergren Adam Johan , McCreery Richard 
Published: February 2020

Molecular electronic junctions can be made by covalently bonding aromatic molecules and graphene ribbons to a flat, sp2 hybridized carbon electrode followed by a “top contact” of electron-beam deposited carbon. The entire active region of the structure consists of carbon and hydrogen, and electronic properties range from insulators to efficient conductors, with excellent lifetime and tolerance to temperature excursions. 1-3 Of particular interest is a carbon/graphene/carbon device containing 5-carbon wide graphene ribbons, which avoids torsional disorder common to aromatic molecular components (shown schematically below, left). The graphene devices have the highest molecular conductance reported to date for large-area molecular junctions, and is stable for at least five million current/voltage cycles to ±4 A/cm2. 4 An application of all-carbon molecular tunnel junctions in electronic music will be described, which resulted in the first known commercial product involving molecular electronics (below, right). 5

(1) Morteza Najarian, A.; Bayat, A.; McCreery, R. L.; Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions; Journal of the American Chemical Society
2018, 140, 1900.
(2) Supur, M.; Smith, S. R.; McCreery, R. L.; Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy; Analytical Chemistry
2017, 89, 6463.
(3) Morteza Najarian, A.; McCreery, R. L.; Structure Controlled Long-Range Sequential Tunneling in Carbon-Based Molecular Junctions; ACS Nano
2017, 11, 3542.
(4) Supur, M.; Van Dyck, C.; Bergren, A. J.; McCreery, R. L.; Bottom-up, Robust Graphene Ribbon Electronics in All-Carbon Molecular Junctions; ACS Applied Materials & Interfaces
2018, 10, 6090.
(5) Bergren, A. J.; Zeer-Wanklyn, L.; Semple, M.; Pekas, N.; Szeto, B.; McCreery, R. L.; Musical molecules: the molecular junction as an active component in audio distortion circuits; Journal of Physics: Condensed Matter
2016, 28, 094011.

Figure 1
Toward the Chemical Isolation of Larger-Size Empty-Cage Fullerenes
Authors: Stevenson Steven , Koenig Ryan 
Published: February 2020

A plethora of literature exists for C60 and C70. Isolated in gram quantities since the early 1990s, these empty-cage fullerenes are well-studied due to their (1) high abundance in carbon soot extracts and (2) ease of separation. Depending on the method of synthesis (e.g., electric-arc), C60 and C70 typically comprise 95-98% of the soluble fullerene extract. The remaining 2-5% represents the higher fullerenes, e.g., C76 - C140 and beyond. How does one isolate these higher cage fullerenes given their extremely low abundance? Great question - which will be addressed.
Our goal is developing a new separation method to chemically isolate these higher fullerenes. An inherent advantage to chemical methods is the removal of structural isomers, which present co-elution challenges with HPLC alone. In this presentation, we discuss the attractiveness of being able to remove more reactive fullerenes to greatly simplify samples. A successful purification strategy for isolating higher fullerenes would make macroscopic quantities available for the first time.
Electrochemical Intercalation of AP-CVD Grown Few-Layer and Multi-Layer Graphene
Authors: Accogli Alessandra , Gibertini Eugenio , Pedrazzetti Lorenzo , Panzeri Gabriele , Lucotti Andrea , Magagnin Luca 
Published: February 2020

First studies on intercalation of graphite date back to the first half of the XX century. At first, the ability of graphite to spontaneously form intercalation compound (GIC) by the soaking in strong acids was studied. Only later, GIC were obtained by electrochemical route, highlighting the mechanism of formation of GIC in extremely ordered layered structure as HOPG [1,2]. Anodic electrochemical intercalation is typically performed in acidic aqueous solution, forming GIC by the insertion of anions as ClO4-, HSO4- and NO3- [3]. Anodic electrochemical intercalation is nowadays useful to obtain high quality Graphene Oxide (GO) thorough an easy and green route [4]. Studies on the formation of GIC by cathodic polarization opened to the understanding and exploitation of the reversible intercalation of alkali ions (Li+, Na+) that found the suitable application in Li battery technology [5]. However, up to now, studies have concentrated mainly on the electrochemical formation of GIC HOPG, but very few have investigated the GIC formation in nanoscaled graphitic material as graphene [6]. In this work, we provide a comprehensive understanding of the GIC formation by electrochemical route in few-layer graphene grown through atmospheric pressure chemical vapor deposition (ACVD) on metallic substrates. Anodic electrochemical intercalation of few layer graphene in acidic, organic-based and aqueous-based media has been investigated. A deeper understanding of intercalation and doping phenomena of few layer graphene has been performed in situ through Raman spectroscopy measurements. Preliminary results on cathodic intercalation of few layer graphene in aqueous and organic media will be also discussed.

References

[1] H. Thiele, Trans. Faraday Soc., 1938,34, 1033-1039
[2] F.Beck, H.Junge, H.Krohn, Electrochemical Acta, 26 (7), 1981, 799-809
[3] D.C. Alsmeyer, R. L. McCreery, Anal. Chem., 1992, 64 (14), 1528–153
[4] K. Parvez, Z. Wo, R. Li, X. Liu, R. Graf, X. Feng, K. Müllen J. Am. Chem. Soc., 2014, 136 (16), 6083–6091
[5] S.Basu, C.Zeller, P.J.Flanders, C.D.Fuerst, W.D.Johnson, J.E.Fischer, Materials Science and Engineering, 1979, 38 (3), 275-283
[6] E. Pollak, B. Geng, K. Jeon, I.T. Lucas, T. J, Richardson, F. Wang, R. Kostecki, Nano Lett., 2010, 10 (9), pp 3386–3388.
Preparation and Evaluation of Pt-Ru/CNTs Catalysts for Direct Methanol Fuel Cell
Authors: Tavakoli Mehrabadi Bahareh Alsadat , Regalbuto John R. , Weidner John W. , Monnier John R. 
Published: February 2020

The most widely used electro-catalyst material in direct methanol fuel cell (DMFCs) are Pt-Ru bimetallic electro-catalysts, which show the best performance among other bimetallic catalysts. Many methods exist to prepare catalysts with bimetallic surfaces, and the properties and performance of these catalysts vary widely. Previous studies have shown that combining strong electrostatic adsorption (SEA) and electroless deposition (ED) methods can increase the surface area of the Pt particles by lowering the particle sizes of the bimetallic particles [1]; however, decreasing particle sizes can result in other problems such as thermal stability. Therefore, new routes for development of highly active and stable catalyst supports have become important to study. Among the different forms of carbon support, carbon nanotubes (CNTs) are especially known for their crystallinity which not only imparts structural uniformity and high electrical conductivity, but also assures stability of the nanomaterials deposited on the support. In addition, they fulfill the properties of high surface area, high thermal conductivities, extraordinary strength, and resilience to an acidic environment, all of which can prove highly important for improving the performance of a fuel cell catalyst.
In this work we have investigated the effect of CNTs support for the methanol electro-oxidation reaction. The combination of SEA and ED methods have been used for deposition of Pt-Ru bimetallic catalysts on CNTs and to predict the effect of support on DMFC performance. The materials synthesized will be characterized by X-ray diffraction (XRD) spectroscopy for crystal structure and energy dispersive spectroscopy (EDS) will be employed to examine elemental analysis and distribution. To observe surface morphology HRTEM images will be used, and BET surface areas and pore volume measurements will be carried out to evaluate porosity and pore size distributions.
References

Tengco, J.M.M., et al., Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation. Catalysts, 2016. 6(6).