bluuebunny/crossref_metadata_2025 huggingface dataset:
Bimetallic−Organic Framework-Derived Hierarchically Porous Co-Zn-N-C As Efficient Catalyst for Acidic Oxygen Reduction Reaction
Authors: Meng Zihan
Published: February 2020

The development of highly active and cost-efficient electrocatalysts toward oxygen reduction reaction (ORR) is essential for widespread application of polymer electrolyte fuel cell (PEFC). In the present work, hierarchically structured porous Co-Zn-N-C electrocatalyst is prepared by using soft templated bimetallic-organic framework precursors.

The as-synthesized hierarchically porous catalyst presents outstanding ORR onset-potential (0.88 V vs. RHE), half-wave potential (0.78 V vs. RHE), and diffusion limiting current density (5.73 mA cm-2), that is similar to that at commercial Pt/C catalyst in acidic electrolyte. It is found that the hierarchical porous architecture is important for its excellent catalytic activity and further testifies that the hierarchically porous electrocatalyst also exhibits superior single PEFC performance with a power density of 412 mV cm-2.

The present work provides not only a facile and low cost strategy toward the preparation of hierarchically porous materials, but also inspires an approach for enhancing the ORR electrocatalytic activity of MOF-derived materials.
Pulsed Electrodeposition of Si Under Light Illumination in Ionic Liquid
Authors: Watanuki Shuei , Fukunaka Yasuhiro , Homma Takayuki
Published: February 2020

Electrodeposition of Si has attracted much attention for its possibility to apply various areas such as photovoltaic cells and MEMS. Si thin film can be electrochemically fabricated with precise microstructural control and in a relatively simple process. However, it requires nonaqueous solvents due to very negative reduction potential of Si(IV). Ionic liquids are promising solvents for Si electrodeposition because of its unique characteristics such as nonflammable, non-volatile, and relatively wide electrochemical window. We have reported the electrochemical processing on Si thin films, nanodots, and nanopillars in trimethylhexyl ammonium bis-(trifluorosulfonyl) imide (TMHATFSI) ionic liquid containing SiCl4 as Si precursor [1-3]. Moreover, our recent paper [4] reports relatively smooth and compact Si thin films obtained by applying pulsed deposition, and smoother ones by applying light illumination additionally. Here we present the results of our work in the electrochemical processing of Si thin film with the pulsed potential modulation and light illumination. These experiments were conducted in order to promote the diffusion of precursor and light-assisted electrodeposition respectively. In the preliminary experiments, it turned out that the composition of Si film in pulse potential modulation [4] contained relatively large amount of impurities than the films potentiostatically deposited [3]. This result suggests that the oxidation currents during the rest period of pulse deposition may be partly responsible for such a larger impurity. Then, pulse potential modulation scheduling was further examined. Controlling the potential and current density considerably suppressed oxidation current. The composition of Si thin films was improved to recover to the level of potentiostatic electrodeposition. However, some cracks were still observed the surface. Thus, light illumination only in deposition time was superimposed. As a result, large cracks disappeared, and continuous and relatively smooth Si thin films with relatively low impurity were obtained.

[1] T. Homma, J. Komadina, Y. Nakano, T. Ouchi, T. Akiyoshi, Y. Ishibashi, Y. Nishimura, T. Nishida, and Y. Fukunaka, ECS Trans., 41 (2012) 9.

[2] Y. Ishibashi, T. Akiyoshi, J. Komadina, Y. Fukunaka, T. Homma, ECS Trans., 50 (2012) 117.

[3] Y. Tsuyuki, A. Pham, J. Komadina, Y. Fukunaka, T. Homma, Electrochim. Acta, 183 (2015) 49.

[4] Y. Tsuyuki, H. Takai, Y. Fukunaka, T. Homma, Jpn. J. Appl. Phys. 57 (2018) 08RB11.
Rheological Study of Electrode Ink for a PEMFC: I/C and Solid Content
Authors: Yang Donglei , Chuang Po-Ya Abel
Published: February 2020

Facilitating cost reduction and durability improvement of the next-gen PEMFCs requires focused efforts on not only advanced catalyst materials but also optimized electrode design concepts1,2. Currently, the most widely used electrode in a PEMFC is made from ink dispersion consists of catalyst, catalyst support, ionomer, and solvent. Before advancing optimized electrode design, the desired properties of the electrode ink dispersion and its corresponding relationship to catalyst layer need to be studied3. In our previous work, we have used rheological measurements as a tool to study a baseline electrode ink with Pt/C and Nafion ionomer. The strength, tortuosity and structural character of electrode ink were quantitatively and qualitatively characterized by oscillation amplitude sweep and frequency sweep. The flow property of the catalyst inks was measured by viscometry. A coating process was also simulated and its impact on the ink microstructure was investigated as well. With our preliminary results from the oscillatory and viscometry tests, we proposed physical models to describe Pt/C-ionomer agglomerate as the microstructural unit in various water/IPA binary solvents. These collective data also verify a strong correlation between the electrode ink rheology and its resulting microstructure, which allowed us to speculate the Pt/C-ionomer agglomerate structure in the opaque electrode inks. The rheological characterization of electrode ink not only enhances our fundamental understanding of the electrode formation, but also provides valuable information for electrode optimization. Built upon the foundation of our previous work, we employed an improved approach to study ionomer to carbon ratio and solid content in the electrode ink in this work. The main objective is to improve fuel cell performance through optimization of electrode ink. This comprehensive study allows us to understand the adsorption behavior of ionomer onto Pt/C and their impact on the microstructure of Pt/C-ionomer agglomerates. With the assist of rheological data, we were able to identify the optimal ionomer to carbon ratio for this system at different solid content. Our preliminary results showed strong interactive nature between Pt/C, ionomer content, and volume fraction. Key rheological features of the studied inks and their corresponding relationship to the electrode microstructure for performance optimization will be present at the conference.

References

Kongkanand A and Mathias MF. The priority and chanllenge of high-power performance of low-platinum proton-exchange membrane fuel cells. The journal of physical chemistry letters, 2016, 7, 1127-1137.

Banham D and Ye S. Current status and future development of catalsyt materials and catalyst layers for proton exchange membrane fuel cells: an industrial persperctive. 2017, 2, 629-638.

Hatzell KB et. al.. Understanding inks for porous-electrode formation. 2017, 5, 20527-20533.
Development of a Conductive Biomimetic Nanocomposite Anode for Improved Microbial Fuel Cell Efficiency
Authors: Dunne Alana Danielle , Puckett Madalyn D. , Yuede Nicole Elizabeth , Keleher Jason J.
Published: February 2020

Microbial fuel cells (MFCs) have gained attention as a renewable energy option due to the utilization of microbes as catalysts for the oxidation of natural substrates. In order to increase the practical application of MFC technology, the overall system must enhance power output and lower operational costs. More specifically, the bacteria must dock on the electrode surface to allow for efficient electron transfer mechanisms. In efforts to increase productive bacteria-surface interactions, this work focuses on the synthesis of a conductive, cellulose-based nanocomposite for use as anodic electrodes. The nanocomposite material was non-covalently modified through the incorporation of sugar-functionalized TiO2 nanoparticles. The relationship between conductivity and biocompatibility was explored in order to optimize the interactions between the synthesized electrodes and Escherichia coli (E. Coli). Power production using the composite electrodes was correlated to biofilm formation and cell proliferation via atomic force microscopy (AFM) and live/dead stain, respectively. The composite electrode materials have shown increased electrical response over traditional carbon cloth when used as anodes under dye-mediated conditions. Additionally, the sugar-functionalized composites showed increased bacterial adsorption and enhanced cell viability indicating more intimate contact between the microbes and the electrode surface. Initial results also suggest photochemical activity using sugar, polyaniline modified TiO2 nanoparticles embedded within the cellulose matrix resulting in responsive fuel cell behavior. Future work aims to incorporate supramolecular structures, such as β-cyclodextrin, to constrain dye absorption to the material surface and potentially increase the electrical response and longevity of the fuel cell system.
Flue Gas Derived Carbon Electrocatalysts for Enhancing Oxygen Reduction Reaction
Authors: Park Jae Hyun , Baik Seoyeon , Lee Jae W.
Published: February 2020

Flue gas was directly converted into carbon materials with the doping of iron, boron and nitrogen atom. The B-N doping was achieved in a single step with the carbonization of flue gas and subsequently, the Fe atom was incorporated into the material using the iron precursor (FeCl3). The synthesized Fe-N-B co-doped carbon materials showed enhanced electrochemical activity for oxygen reduction reaction (ORR), which is comparable to that of commercial platinum catalysts. The effect of various FeN/C ratios by varying the amount of iron species in the synthesis step was investigated, and the clear correlation between the doping of Fe/N and electrochecmical activity was confirmed. The optimized iron weight ratio was 33 % due to the existence of Fe-N pyridinic bonding in the carbon lattices without agglomeration of Fe species. The high electrocatalytic activity toward ORR and long-term durability for 10,000 cycles of synthesized Fe-N-C composites indicate that flue gas itself can be an effective precursor for efficient carbon-based electrocatalysts.
Nanostructured Carbon-Free Tantalum Oxide-Supported Platinum for Highly Active and Stable Acidic Oxygen Reduction Electrocatalysts
Authors: Rhodes Christopher P. , Aguirre Lupita S.
Published: February 2020

Oxygen reduction reaction (ORR) electrocatalysts that provide high activity, long-term stability, and reduced precious metal content are needed for proton-exchange membrane fuel cells (PEMFCs). Typically, carbon is used as a catalyst support; however at elevated voltages encountered during start-up/shut-down, carbon corrosion occurs which can significantly reduce the long-term stability of the catalyst. Tantalum pentoxide (Ta2O5) is stable under the oxidative potentials and acidic conditions of the oxygen reduction reaction, but prior efforts have largely focused on carbon-Ta2O5-platinum catalysts which can still result in degradation of the support. We have investigated carbon-free nanostructured tantalum oxide as a support material to obtain a high surface area, conductive, stable support for acidic ORR electrocatalysts. Tantalum oxide (TaOx) was synthesized using sol-gel chemistry, and the effects of synthesis parameters, processing conditions, thermal treatments were evaluated. The effect of introducing substituents was evaluated to increase the electronic conductivity. The structure and morphology of the nanostructured TaOx support was determined using X-ray diffraction, nitrogen physisorption, and scanning electron microscopy. Electronic conductivity measurements were determined using a two-point probe configuration. The ability to create carbon-free, high surface area, nanostructured conductive oxides opens up new opportunities for the design of high activity and stability carbon-free catalyst nanoarchitectures for ORR and other electrocatalytic reactions.
Modeling Fermi Levels in Metal Functionalized TiO2 Sensors for Applications in Volatile Organic Biomarker Detection
Authors: McKinnon Lani , Saffary Yalda , Mohanty Swomitra , Prisbrey Keith
Published: February 2020

There is a large knowledge base of characteristic volatile organic biomarkers (VOBs) that are detectable as a direct result of a particular disease. VOBs can be detected from many sources including patient breath and urine. The fabrication and testing of VOB sensors for the detection of various diseases is the topic of several ongoing projects in our research group. These VOB sensors utilize a highly specific interaction between a known VOB, a metal-functionalized titanium dioxide sensor, and an applied voltage. When designing a novel sensor for a different disease it can be extremely difficult to determine the appropriate components because the correct choice for VOB, metal, and voltage are all of great importance and each component comes with many possible options.

A simplified version of the sensor system has been examined with various combinations of VOBs and metals using modeling software that employs density function theory (DFT). Density functional calculations were performed to calculate the fermi level of TiO2 functionalized with a group of metals of different valency including Co(III), Ni(II), Fe(II), and Cu(I). The fermi level was then determined for the selected system in the presence of a known VOB. For a potential pneumonia breath sensor these VOBs included heptane, acrolein, and ethylbenzene. The more negative the fermi level became when the metal-functionalized titanium dioxide was in the presence of a particular VOB, the better the sensor was predicted to respond. Promising systems were then tested for selectivity by determining the fermi level of the sensor in the presence of compounds commonly found in breath that are not indicative of the disease. The results from this study directly apply to the fabrication of a potential pneumonia breath sensor, but are also appropriate for a broad range of applications where volatile organic compound detection is needed.
Synthesis and Characterization of Self-Organized Oxide Layer Grown on Ti-Cu Alloys System for CO2 Reduction
Authors: de Almeida Juliana , Câmara Stella Hoffman , Bertazzoli Rodnei , da Silva Ricardo Galdino , Rodrigues Christiane Arruda
Published: February 2020

Carbon dioxide (CO2) is the main responsible for greenhouse effect. The global concentration of CO2 in the atmosphere is increasing mainly due to the emissions from fossil fuel combustion. The reduction of CO2 by photocatalysis is one of the most promising methods since CO2 can be reduced to useful compounds by irradiating it with UV light at room temperature and ambient pressure. Several semiconductors, titled p-type, exhibit suitable band energies for photocatalytic reduction of carbon dioxide. Copper oxides have properties that leads methanol and ethanol formation when applied in CO2 reduction process and it can be used as an efficient sensitizer to couple with other wide band gap semiconductors, such as TiO2, to expand the photocatalytic application in the reduction experiments and to improve its absorbance in visible light. However, copper in its different kind of oxidation (copper metal, Cu2O and CuO) are easily dissolved and its stability is a challenge. In the present work, nanostructures heterojunction films of Cu–Ti–O was fabricated to act as a polarized photoelectrochemical for future applying in CO2 reduction process. The films were growth by anodizing process on Ti-x%atCu alloy substrate, containing different concentration of copper (x= 0.5, 5.5, 10, 50), after annealing or quenching heat treatment. The alloys with less 10 % of copper concentration were attacked by 0.1 M HF in ethylene glycol, with a small H2O quantity in the electrolyte, varying from 0 to 5.0 %. These films showed nanotubes structures with thickness around 1.0 μm and 70 nm of the inner diameter. While in equiatomic alloy a porous layer was obtained after anodization process employing 0.1 M HF + 0.2 KCl in ethylene glycol and alkaline pH. The growth, structure, and photocatalytic properties of these electrodes were investigated by SEM-FEG, XRD, XPS, UV-Vis spectroscopy and photocurrents by linear voltammetry experiments in a solution containing 0,1 mol L-1 Na2SO4, with a potential range from -0.025 to -1.0 V vs. Ag/AgCl/Cl- (3M). All films presented TiO2 and copper dioxides in its compositions. These electrodes showed higher absorbance in visible light, anodic current for low copper concentration in the alloy, cathodic current in equiatomic alloy composition and copper stability for all cases due to insertion of Cu atomic inside TiO2 crystal lattice and sharing oxygen atomic and the catodic currente varied in function of Cu concentration in the alloy.

Keywords: Ti-Cu alloy, thin films, self-organized oxide layer, p-n heterojunction
Thermal Stability Study of Commercial Lithium-Ion Batteries As a Function of Cathode Chemistry and State-of-Charge
Authors: Barkholtz Heather , Preger Yuliya , Langendorf Jill , Lamb Joshua , Chalamala Babu R. , Ferreira Summer , Ivanov Sergei
Published: February 2020

The safety of lithium-ion batteries is mainly quantified by thermal runaway characteristics such as onset temperature, peak heating rate (HR), and maximum pressure release. This talk evaluates the materials aspects of thermal runaway of commercial lithium-ion batteries by correlating the contributions from individual cell components to thermal runaway trends. An accelerating rate calorimeter was used to define the thermal runaway behavior of three commercial 18650 lithium-ion batteries (LiCoO2, LiFePO4, and LiNixCoyAl1-x-y­O2) at various states of charge (SOC). Cells were also disassembled and the thermal properties of their component materials was evaluated by thermogravimetric analysis, differential scanning calorimetry, and temperature-resolved X-ray diffraction. Broadly, lithium-ion battery thermal runaway process begins with solid-electrolyte interface and negative active material decomposition followed by the positive active material breakdown. The experimental results show that the onset temperature is generally independent of SOC and peak HR increases with SOC as a result of cathode destabilization. Overall, LiNixCoyAl1-x-yO2 decomposes readily, and charged LiCoO2 is also metastable, although it decomposes more gradually than LiNixCoyAl1-x-y. Contrary to the layered transition metal oxides, LiFePO4 is stable to > 500oC, even when charged. The results are aimed at informing future engineering and fire protection of commercial lithium-ion batteries.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2018-3360 A
Unlocking the Safety Issues Caused By Internal Short Circuits in Lithium-Ion Batteries
Authors: Liu Binghe , Xu Jun
Published: February 2020

Lithium-ion batteries (LIBs) have been attracting tremendous focuses and fundamental impetus for the fast development of electric vehicles, computers, cellphones and among others . Mechanical loading may catastrophically cause battery internal short-circuit (ISC) and then usually lead to irreversible and chain reaction until the dead of the cell. Possible hazards such as excessive heat, gas/smoke, fire and explosion of LIBs triggered by ISC greatly refrains further wide application of LIBs as well as developing higher energy density LIBs. However, a clear picture of the LIB’s electrochemical safety behavior triggered by mechanical loading is still uncovered. Here we systematically show that there are three modes of electrochemical behavior for LIBs after ISC, i.e. fast voltage drainage with no thermal runaway (TR), several cycles of voltage drop-recovery followed by TR, and a significant voltage-drop followed by TR, triggered by mechanical abusive loading. By highly repeatable tests, detailed characterization and computation modeling, we found that electrochemical safety behavior of LIBs is dominated by SOC, ISC area and resistance. Our results demonstrate the safe boundary and electrochemical behavior map for LIBs after ISC. We anticipate that this discovery will lead to new opportunities for LIB safety design, manufacturing, assembling, evaluation and protection.
Infrared Spectroscopic Study of the Thermal Stability of Alkyl Carbonate Electrolytes
Authors: Porter Jason Morgan , Saqib Najmus
Published: February 2020

Decomposition of ethylene carbonate (EC) in lithium ion batteries leads to battery swelling, off-gassing, and thermal runaway. Ethylene carbonate decomposes electrochemically by reduction at the anode or chemically in the bulk electrolyte at elevated temperature. The formation of a solid electrolyte interface (SEI) on the anode limits electrochemical decomposition so long as the SEI remains intact. While neat ethylene carbonate is thermally stable at temperatures exceeding 150°C, EC-based electrolytes containing lithium hexafluorophosphate (LiPF6) salt are known to chemically react at temperatures as low as 50°C. Decomposition rate has been shown to increase with higher salt content, indicating a salt-catalyzed thermal decomposition mechanism. Trace contaminants, especially moisture, have also been shown to strongly effect electrolyte thermal stability. Thus, small impurities in the manufacture of battery components can have dramatic effect on electrolyte stability and battery aging.

Electrolyte decomposition mechanisms have been studied extensively. Differential scanning calorimetry (DSC) and accelerated rate calorimetry (ARC) can identify temperatures of reactions, kinetic parameters, and heat release rates. Decomposition mechanisms and reaction products are also identified indirectly by ex situ electrolyte and off-gas analysis. Despite numerous studies, much remains unknown about decomposition chemistry in lithium ion batteries, especially the role of trace impurities on stability. Further, little is known about electrolyte decomposition mechanisms in batteries, as few operando electrolyte diagnostics exist.

In this work, the chemical stability of EC at elevated temperature is studied using infrared spectroscopy. Electrolyte samples are heated on an attenuated total reflection (ATR) spectrometer stage using both liquid samples and in operating half and full cell batteries. Liquid samples were prepared in an argon glove box with varying concentrations of LiPF6 salt, H2O, and in CO2 gas environments (to simulate cathode off-gassing). Accurate temperature readings up to 150°C were made using infrared thermometry. Operando spectroscopic measurements of electrolyte stability in graphite half cells, lithium cobalt oxide (LiCoO2) half cells, and lithium ion full cells were also collected. Reaction rates and activation energies are also reported using time-resolved infrared spectroscopy.
Comparison of the Thermal Reaction Kinetic Parameters of Layered Li[NixCoyMnz]O2 Cathode Material with Different Nickel Content and Different Crystal Structure
Authors: Wang Yu , Ren Dongsheng , Hsu Hungjen , Feng Xuning , Lu Languang , Ouyang Minggao
Published: February 2020

Layered Li[NixCoyMnz]O2 (NCM) material with high nickel content is a promising cathode material for next generation lithium-ion batteries because of its high energy density. However, the NCM materials become unstable with nickel content increasing and face safety problems at elevated temperatures. In this study, we report and compare the thermal stability and thermal reaction kinetic parameters of NCM materials with different Ni content (x=0.3, 0.5, 0.7 and 0.8) and different crystal structure (single crystal / poly-crystal). The active materials were heated with diﬀerential scanning calorimetry (DSC) from room temperature to 550℃ at various heating rates. The kinetics parameters (pre-exponential factor, activation energy, mechanism function and reaction enthalpy) of each exothermic reaction were identiﬁed with Kissinger’s method and nonlinear ﬁtting method. Results showed that the NCM crystal structure had little influence on the NCM exothermic peak temperature and the kinetic parameters. With Ni content increasing, the exothermic peaks shifted to lower temperatures and the activation energy of the first exothermic peak decreased. Thus, the NCM cathode with higher Ni content was easier to experience phase transition process accompanied with oxygen release at elevated temperatures. This study compared the thermal stability of NCM materials with different Ni content and different crystal structure, and provided kinetic parameters of the NCM exothermic reactions for the future thermal safety simulations of lithium-ion batteries.

Figure 1
(Invited) Thermal Runaway Propagation Resistance in Lithium-Ion Batteries
Authors: Srinivasan Rengaswamy , Thomas Michael E , Airola Marc B. , Carkhuff Bliss G , Frizzell-Makowski Linda J. , Alkandry Hicham , Reuster James G. , Oguz Hasan N. , Green Peter W , Demirev Plamen A , Currano Luke J.
Published: February 2020

Thermal runaway (TR) is a commonly-known mode of failure in lithium-ion (Li-ion) cells. TR generates large amounts of heat and fire as well as toxic gases that are potentially destructive. A Li-ion battery consists of multiple cells in which TR from a single cell could propagate creating cascading failures across multiple cells, generating high-energy shrapnel and a large quantity of toxic and corrosive materials. TR propagating between cells in multi-cell batteries causes more destruction than TR in a single-cell battery, the most striking examples being electric vehicle batteries in which fires are typically much larger than fires in single-cell mobile phones.

Conventional understanding of TR propagation has been limited to the perception that heat generated from a cell under TR is carried to the adjacent cells: a.) predominantly by ejected high-temperature gases and solids; and b.) to a lesser degree by conduction through metallic parts within the battery such as cell interconnects. If the conventional understanding is correct, then removing/venting the high-temperature gases and solids ejected at the time of TR from the battery compartment will primarily prevent cell-to-cell TR propagation. In fact, although batteries have been designed with vents that provide opportunity for hot matter to exhaust away from the rest of the cells, they have not successfully prevented TR propagation. In other words, the conventional model used in describing TR propagation needs to be revised.

We recently observed by infrared spectroscopy that when a cell temperature rises, but before the start of TR, flammable organic compounds such as carbonate esters are ejected from the cell. This observation sheds new light on the thermal propagation processes in multi-cell Li-ion batteries. The ester is ejected as a gas through vent valves in the cell, and it condenses outside the cell which is evident in its absorption spectra. Although the ester can be highly flammable (similar to gasoline), it requires a spark to ignite and an oxidizer to burn. If either is missing, the ester is deposited on adjacent cells, either as a liquid or a mixture of liquid and trapped gas, and is not vented out of the battery housing. The condensation of esters on adjacent cells is supported both by experimental data and computational fluid dynamics models. When the cell goes into TR, both ignition spark and oxidizers are present, which ignites the ester. The ester starts burning on the surface of the adjacent cells, sending them also into TR. This finding ultimately has implications for innovative technical solutions aimed at preventing large multi-cell battery fires.
Inhibiting Thermal Runaway in Large Format Li-Ion Batteries
Authors: Torres Gabriel , Moganty Surya Sekhar
Published: February 2020

NOHMs Technologies is developing novel safe solvent hybrid electrolytes for safe, high energy density, high voltage, and high-power lithium-ion batteries for mobility and consumer applications. Over the past 25 years there has been a proliferation in the use of lithium ion technology and with that ever-increasing market demand for higher energy density cells – demand primarily met by advancements in the cathode and anode. This proliferation has come with the increased rise of safety concerns. There have been high profile incidents of what is known as thermal runaway across a wide variety of applications ranging from consumer electronics to electric vehicles.

It is well understood that thermal runaway occurs when the self-heating rate in the cell exceeds the heat dissipation out of the cell. This self-heating is the product of undesired side-reactions in the cell which are onset by abuse conditions such as excess heat, internal short circuits, etc. The key to inhibiting thermal runaway is to modify the cell such that the self-heating rate under abuse conditions is significantly reduced. Reducing the self-heating rate is important when considering battery packs that consist of many cells as is the case in electric vehicles, so that if one cell fails in a pack the thermal runaway does not propagate to adjacent cells. Given that market trends are moving away from low energy electrodes, our approach therefore is to modify the electrolyte system to reduce the overall cell self-heating rate. This is a tunable, drop-in solution to addressing the need for improving battery safety.

The incorporation of NOHMs novel safe solvents into the electrolyte formulation is shown to impact the abuse tolerance of cells on both the material level, i.e. the electrolyte-electrode interaction and on the cell level. The presented electrolyte systems demonstrate reduced overall energy and peak heat flow in the exotherm profiles of high-nickel cathode materials as well as lithiated graphite via differential scanning calorimetry (DSC). With this approach, we demonstrate significantly lower self-heating rates in an accelerating rate calorimeter (ARC) heat-wait-seek test on 30 Ah and above high-nickel cathode lithium ion cells. Combined with good rate capability and cycle life NOHMs’ novel safe solvents present an improvement in battery safety without compromising battery performance. This approach carries significance in not just safer individual cells but also in safer overall battery packs.
Early Warning of Thermal Runaway for Lithium-Ion Battery Based on Multi-Sensor Detection
Authors: Pan Yue , Feng Xuning , Lu Languang , Ouyang Minggao
Published: February 2020

The expansion of the electric vehicle market, giving credit to the technical breakthroughs in the energy density and cycle life of lithium-ion batteries, is beyond our expectations. However, the lithium-ion batteries with high energy density still suffers from safety problems, such as thermal runaway. Thermal runaway always occurs with fire and explosion, which threatens human lives and properties. It is essential to make early warning before the triggering of battery thermal runaway happens.

In this study, an online fault-diagnosis algorithm that can be used for the early warning of thermal runaway is proposed based on joint information measured by multiple sensors. A set of sensors, including voltage, temperature, flammable gas and pressure, are used to monitor the direct and indirect features of thermal runaway. Figure 1 shows the scheme of the proposed fault-diagnosis algorithm, including five steps that explain how this algorithm makes decision of warning. Step I is for data collection, while the data are acquired from the thermal runaway tests. Step II is for data screening. The average temperature, average voltage, maximum temperature and minimum voltage are obtained for further data processing. Step III is for the difference calculation. The voltage difference and temperature difference are calculated. Step IV is called the fault level transformation. The continuous deviations and the continuous signals of gas sensor and pressure sensor are transformed into discretized fault levels. Step V is for the fault judgement. The overall fault level is calculated by merging all the fault levels. The thermal runaway can be captured by setting proper threshold to judge the overall fault level.

To confirm that the algorithm is capable of detecting thermal runaway before it develops into a severe hazard, thermal runaway tests on commercial 18650 cells were conducted. A customized transparent PMMA box, which has comparable volume of the module of Tesla Model S, is designed as the experimental vessel. Battery cells, which have the identical cell number of one Tesla module, are placed in the vessel. Thermal runaway is triggered by heating one of the cells. Sensors are placed in different locations of the vessel to find the optimal location. The test results validate the warning algorithm, and will be presented at the conference.

Acknowledgement: This research is supported by the National Natural Science Foundation of China under the Grant No. U1564205 and No.51706117, and funded by the Ministry of Science and Technology of China under the Grant No. 2016YFE0102200.

Figure 1. The scheme of the proposed fault diagnosis algorithm for TR warning.

Figure 1
Detection and Quantification of Lithium Plating on Graphite in Low Temperature and Fast Charging Operation
Authors: Fear Conner , Mistry Aashutosh N , Carter Rachel E. , Love Corey T , Mukherjee Partha P.
Published: February 2020

As a broad range of industries turn to lithium-ion batteries as an energy storage solution, the safety and performance of these systems becomes increasingly critical. Of the many degradation processes that reduce battery performance with age, the most dangerous and most detrimental process is the plating of metallic lithium on graphite anodes, which is known to occur most severely during charging at high rates and low temperatures. The potential consequences of lithium plating are rapid capacity fading, increased impedance, internal short circuiting due to lithium dendrite growth, and a reduction in the onset temperature of thermal runaway, making detection of lithium plating vital to the safe operation of these cells. However, reliable in-situ methods for detection and quantification of plated lithium are lacking. In this work, lithium plating was induced in graphite half cells by lithiating graphite electrodes at various C-rates and temperatures, using a constant current with a fixed charge throughput equivalent to their C/20 capacities. An impedance-based technique is proposed for detecting lithium plating in graphite half cells. Furthermore, a nondimensional parameter is developed and validated to allow for quantitative comparison of the extent of lithium plating when the anode potential curve is known.
Characterization of Double-Stranded DNA on Single-Walled Carbon Nanotubes (SWCNTs)
Authors: Wu Shang-Jung , Schuergers Nils , Lin Kun-Han , Gillen Alice Judith , Corminboeuf Clemence , Boghossian Ardemis Anoush
Published: February 2020

DNA has been extensively studied due to its versatility as a dispersant of SWCNTs. The specificity and binding affinity of DNA to various analytes has been shown to be strongly sequence dependent. As a result, through modifications of the nucleotide sequence, the DNA conformation on the SWCNT surface can be tailored to suit specific needs for techniques such as single-molecule detection, in vivo imaging, and chirality separation. To date, the majority of research has focused on the interaction between single-stranded DNA and SWCNT surface, with less focus on the nature of the interaction between double-stranded DNA (dsDNA) and SWCNTs. As a result, the exact interaction mechanism governing this type of complex remains strongly debated and largely unknown.

In this study, we employ various biochemical methods to infer the conformation of dsDNA on the surface of SWCNTs. Our methods are based on imaging techniques for identifying DNA-modifying enzyme activity in the presence of dsDNA-SWCNT complexes. Our findings suggest that dsDNA can partially retain its native conformation on the SWCNT surface, and the degree of dsDNA accessibility is strongly sequence dependent. These findings offer new possibilities for SWCNT sensing applications that employ dsDNA, such as the optical detection of DNA-protein interactions.
(Invited) Single Luminescent Carbon Nanotubes Interrogate the Live Brain Extracellular Space at the Nanoscale
Authors: Cognet Laurent
Published: February 2020

The extracellular space (ECS) of the brain represents up to a fifth of brain volume with an undisclosed complex miniaturized topology. While it has long been seen as a passive brain area, it however constitutes an important signaling region for the development, function and communication of neuronal and glial cells. Interestingly, we have identified luminescent single wall carbon nanotubes, as unique nanoreporters to probe the brain extracellular space. This comes from their unique morphological and near-infrared optical properties, which are now well established but also provide a rich platform for improvements. We used super-localization imaging and single particle tracking of luminescent carbon nanotubes to interrogate the local ECS architecture in live brain tissue at the nanoscale[1-3]. In particular, the interplay between the nanotube geometry and the extracellular space local environment allows extracting information about the ECS local viscosity [1, 4]. In this presentation our recent results about the specific ECS properties near identified brain structures [5] (e.g synapses) and in neurodegenerative disease animal models [6] will also be presented.

References

[1] Godin et al Nat. Nanotechnol. 12 (2017) 238-243.

[2] Gao, et al, Nanomaterials 7, 11, (2017) 393.

[3] Danné et al ACS Photonics, 5, 2, (2018) 359-364

[4] Danné et al in preparation

[5] Paviolo et al in preparation

[6] Soria et al in preparation
(Invited) Biological Multiphoton Imaging Techniques for Tracking Non-Fluorescent Carbon Nanomaterials
Authors: Corr Stuart James , Kakadiaris Eugenia , McDOWELL Meredith , Lewis Eric , Sonka Theresa , Anderson Andrew , Marti Angel , Wilson Lon J.
Published: February 2020

Multiphoton Microscopy (MPM) has enabled an unprecedented level of dynamic exploration within living cells and organisms. The physical principle behind this imaging technique involves the use of near-infrared femtosecond lasers to excite optical processes in fluorescent molecules using two or more photons1. The use of long wavelengths (700 nm – 1000 nm) enables deep tissue penetration (up to 1000 μm) without inducing harmful biological effects. Previous studies include the examination of membrane potentials on the single-molecule scale2, the non-invasive observation of embryo development3, and the simultaneous multiplane imaging of calcium transportation in transgenic mice4. An excellent review of this field can be found in the literature5.

Herein we demonstrate a novel multiphoton-based technique for imaging negligible-to-non-fluorescent
carbon-based nanomaterials such as C60 fullerenes, single-walled carbon nanotubes, and graphene, which usually can only be imaged by conjugation of specific fluorescent tracers thereby altering their inherent dynamics within biological systems. More specifically, we demonstrate optical and photoluminescent activity in water-soluble C60-serinol, highly enriched (95 %) metallic and semiconducting single-walled carbon nanotubes, and graphene. This multiphoton imaging technique was also applied to in vitro and in vivo animal model studies. Various concentrations of the above-mentioned nanomaterials were given to human pancreatic ductal adenocarcinoma (Panc-1) and hepatocellular carcinoma (Heb3B) cancer cell lines, as well as normal, healthy pancreatic ductal epithelial cells (HPDE). In all cases, imaging of these nanomaterials was possible using the MP imaging technique even though the nanomaterials exhibit weak, almost zero inherent fluorescent properties. We also examined the ability to image these nanomaterials, real-time, in vivo, using mice with orthotopic 4T1 breast tumors. Finally, we also include a range of spectroscopy data to examine the specific optical characteristics of the carbon nanomaterials.

References

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Tailoring the Properties of Single-Wall Carbon Nanotube Samples through Structure-Selective Photochemistry
Authors: Zheng Yu , Bachilo Sergei M. , Weisman R. Bruce
Published: February 2020

It is known that as-grown samples of single-wall carbon nanotubes (SWCNTs) contain many different structural forms, displaying distinct optical and electronic properties. We report here that resonant near-infrared irradiation of the E11 optical transitions can induce selective covalent SWCNT functionalization in the presence of dissolved oxygen. By varying the irradiation wavelength, (n,m)-specific photochemistry is achieved. Using three different irradiation wavelengths at 955, 985, and 1130 nm, we have preferentially functionalized the (8,3), (6,5) and (7,6) species in aqueous dispersions. After irradiation, the sample’s fluorescence spectrum showed strong “hole-burning”, and the absorption spectrum was heavily and selectively distorted. Meanwhile, the Raman D/G intensity ratio increases, indicating the introduction of defects in the SWCNT sidewalls. This new approach should prove useful for applications such as spectral bar-coding, biomedical imaging, and spectral strain sensing. This new method of selective functionalization may also permit physical sorting of SWCNT mixtures.
Brightening of Long, Polymer-Wrapped Carbon Nanotubes By Large Scale sp3
Functionalization
Authors: Berger Felix Julian , Lüttgens Jan Matthias , Zaumseil Jana
Published: February 2020

Networks of long, polymer-sorted semiconducting single-walled carbon nanotubes (SWNTs) show excellent transport of both electrons and holes and are thus perfectly suited for electrically-driven light emission in the near-infrared (NIR) [1,2]. So far, their application in near-infrared light-emitting devices has been hampered by their low photoluminescence quantum yield (PLQY) and strong self-absorption owing to their small Stokes shift. In recent years, the controlled introduction of a low density of sp3
defects as exciton trapping sites was shown to lead to red-shifted emission with longer exciton lifetimes and improved PLQYs. However, due to the polarity of the employed diazonium salt reagent, this approach was limited to aqueous dispersions of SWNTs with often short tube lengths and the undesired presence of stabilizers. Here, we present a novel route to sp3
functionalization with diazonium salts in organic, non-halogenated solvents, thereby making it compatible with polymer-wrapped long SWNTs produced by shear force mixing. As a result of the low density of exciton quenching sites on shear mixed SWNTs [3], the excitons are efficiently channeled to the emissive defect sites, leading to absolute PLQYs of 4 % for functionalized (6,5) SWNT dispersions in toluene. This new method paves the way toward the large scale production of high-quality sp3
functionalized SWNTs and hence also thin films for optoelectronic devices with narrowband near-infrared emission.

[1] Rother et al., ACS Appl.
Mater. Interfaces
2016, 8, 5571-5579.

[2] Brohmann et al., J. Phys. Chem. C
2018, 122, 19886-19896.

[3] Graf et al., Carbon
2016, 105, 593-599.

Figure 1
Synthesis and Metrology for Large-Area Applications of Single-Wall Carbon Nanotube Forests
Authors: Meshot Eric , Park Sei Jin , Buchsbaum Steven , Wu Kuang Jen , Fornasiero Francesco
Published: February 2020

Commercial applications of vertically aligned single-wall carbon nanotube (SWCNT) “forests” are on the horizon, with the emergence of their use in nanocomposite membranes,1 electronic interconnects, thermal interface materials, among other promising demonstrations. To realize these potential applications, we sought to not only design reproducible wafer-scale synthesis of high-density SWCNT forests but also to establish advanced metrology to enable quantitative, large-area mapping of several key forest characteristics. This detailed information will unlock better understanding of interdependent correlations among the characteristics and how these correlations inform SWCNT forest growth mechanisms toward enhanced synthetic control.

We performed low-pressure chemical vapor deposition (CVD) on 4-in. Si wafers in an AIXTRON® Black Magic cold-wall furnace. The combination of a low flux of carbon precursors with sub-nm Fe/Mo catalyst films on alumina-coated Si wafers maintained small-diameter SWCNTs (mean as small at 1.87 nm) with number densities up to 2.2 x1012 cm-2. Although removing Mo resulted in categorically larger CNT diameters and lower densities (< 0.9 x1012 cm-2), the mass conversion rate from C2H2 to SWCNT product was essentially constant (~1.2 x106 % g catalyst-1) for all catalyst compositions and CNT densities. These results corroborate the notion that hydrocarbon dissociation may be thermally driven without assistance from the catalyst under these conditions, and that the role of Mo was primarily a physical one in creating smaller, denser SWCNTs. Furthermore, we leveraged a suite of advanced characterization techniques to generate area maps across a 4-in wafer to visualize and evaluate the uniformity of various forest properties, including Raman microscopy (forest height, graphitization level, diameters), synchrotron X-ray scattering (mean diameter),2 and Rutherford backscattering spectroscopy (forest density). The uniformity and coupled correlations among different structural characteristics (e.g., diameter-density, rate-density) within a single wafer were consistent with those observed for multiple wafers grown by sequential runs (up to 5 in a day). This validates the reproducibility of our process and suggests that these correlations may be more universal phenomena.

Lastly, our developments in synthesis represent to our knowledge best-in-class co-optimization of small-diameter, high-density, and large-area SWCNT forest growth. We will briefly discuss growth benchmarks in context of membranes, electrochemical devices, and antireflective surfaces as examples.

Bui, N.; Meshot, E. R.; Kim, S.; Peña, J.; Gibson, P. W.; Wu, K. J.; Fornasiero, F. Advanced Materials
2016,
28 (28), 5871-5877.

Meshot, E.; Zwissler, D. W.; Bui, N.; Kuykendall, T. R.; Wang, C.; Hexemer, A.; Wu, K. J. J.; Fornasiero, F. ACS Nano
2017, 11 (6), 5405-5416.
Photochemical Patterning of Fluorescent sp3 Quantum Defects on Carbon Nanotube Thin Films
Authors: Fortner Jacob , Wu Xiaojian , Huang Zhongjie , Wang YuHuang
Published: February 2020

Fluorescent sp3 quantum defects are an emerging subject of interest due to their remarkable optical properties, including chemically tunable emission in the shortwave infrared, environmentally selective sensitivity, and room-temperature single-photon emission. Many potential applications, such as bioimaging, chemical sensing, and quantum information processing, will benefit from the ability to place different types of defects at locations where, and only where, they are needed. In this presentation, we will discuss our progress in patterning fluorescent sp3 defects on thin films of single-walled carbon nanotubes. We show it is possible to trigger the defect-generating reactions by exciting the nanotubes with light to create arrays and artificial patterns of fluorescent defects.