bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Liquid Water Distribution under Temperature Gradient in PEFC Using in-situ X-ray Visualization
Authors: Komiyama Takahiro , Sasabe Takashi , Naito Hiroshi , Kawamura Katsuyuki , Suzuki Toshiyuki , Hirai Shuichiro
Published: December 2020

Polymer electrolyte fuel cells (PEFCs) are expected to be applied in wider range of applications including automobiles, and the operation at higher current density has been required. However, in the operation at high current densities, the performance of PEFCs is degraded due to liquid water accumulation in the gas diffusion layers (GDLs) which prevents the supply of oxygen to the catalyst. Furthermore, heat is generated in catalyst layer due to electrochemical reaction, leading temperature rise inside PEFCs. Since liquid water accumulation is closely related to temperature distribution, it is expected that temperature distribution alters the spots of liquid water accumulation. Therefore, it is necessary to understand the relationships between the liquid water distribution and the temperature distribution in the GDLs to improve the performance at high current density. This study intended to investigate the effects of temperature distribution on liquid water accumulation by in-situ X-ray visualization.

Liquid water distribution of 60, 70, and 80 ℃ cell temperature cases were measured by X-ray radiography, and current density was kept 1.5 A/cm2 in all cases. We used a serpentine type cell with ribs and flow channels of 300 µm width with 1.5 x 3.0 mm2 active area. As for GDLs, SIGRACET 29BC was used. The humidity of hydrogen in the anode was fixed at 100%. While, the humidity of air in the cathode was adjusted so that the gap between water vapor pressure and saturation pressure becomes 4.0 kPa.

Fig. 1 (a), (b) and (c) shows the liquid water distribution of the 60 ℃, 70 ℃, 80 ℃ cases. It is shown that the liquid water distribution in a region near the MPL/substrate boundary is clearly altered by the cell temperature. This effect is also observed in the averaged profiles of liquid water volume under rib areas (Fig. 1(d)). In Fig. 1(d), liquid water volume in the region near the MPL/substrate boundary (the region between 50 µm to 80 µm) of the 70 and 80 ℃ cases are clearly reduced compared to the 60 ℃ case. Since the overvoltage of each case is almost the same, the resultant temperature gradient inside GDLs due to the heat production is considered to be the same. Meanwhile, the saturated vapor pressure increases more abruptly at higher temperature, since the saturated vapor pressure is more affected by the initial cell temperature. The saturated vapor pressure of the 80 ℃ case is much larger than the other cases, therefore it is suggested that the lower amount of liquid water accumulation of the 80 ℃ case is caused by the larger saturated vapor pressure.

Figure 1
Measurement and Analysis of Gas Transport Properties in Catalyst Layers of Polymer Electrolyte Fuel Cells with Different Ionomer to Carbon Ratio
Authors: Tsutsui Fumiaki , Suzuki Takahiro , Tsushima Shohji
Published: December 2020

Catalyst layers of polymer electrolyte fuel cells are electrochemical reaction fields with complicated porous structures. Catalyst layers are composed of carbon particles supporting platinum catalyst (Pt/C), ionomers and micropores. Gas transport properties in catalyst layers are key factors for improving cell performance. It is necessary to clarify the relationship between the gas transport properties and the microstructure. The authors reported that ionomer in the catalyst layer affects the porous structure and resultant cell performance [1]. Therefore, the objective of this study is to investigate the effects of ionomer to carbon ratio (I/C) of the catalyst layer on the porous structure formation and gas transfer.

In this study, gas transport properties in catalyst layers with different I/C were evaluated by the measurement of gas transfer through thin porous media operated under a micro-channel apparatus (Gas-TOUCA) [2]. The porous structures of catalyst layers were evaluated by the nitrogen adsorption method and the observation using a Field-emission scanning electron microscope (FE-SEM).

Typical experimental results of the measurement of Gas-TOUCA are shown in Figure 1. The measurement was carried out for the catalyst layers under the four conditions of I/C 0.1, 0.3, 0.5 and 1.0. The effective diffusion coefficient in the catalyst layer with I/C 0.5 was the largest, and that in the catalyst layer with I/C 1.0 was the smallest of the four conditions. The tortuosity factor of the catalyst layers with I/C 0.1, 0.3 and 1.0 was approximately 3. However, the tortuosity factor of catalyst layers with I/C 0.5 was approximately 2. Segregation of ionomer was observed in the catalyst layers with I/C 0.5 and 1.0 by SEM. On the other hand, there was no ionomer segregation in the catalyst layers with I/C 0.1 and 0.3, and most of the ionomer could have adsorbed on the Pt/C particles. Ionomer works as a dispersant in electrode slurries [3]. Less amount of ionomer leads to large attractive interaction of particles in the slurry, whereas an excessive amount of ionomer leads to deposition to pores in the catalyst layer. Therefore, the experimental results indicated that there is an optimum I/C ratio for gas transport.

References

[1] T. Suzuki, S. Tsushima and S. Hirai, Int. J. Hydrogen Energy, 36, 12361 (2011).

[2] T. Suzuki, Y. Nakata and S. Tsushima, ECS Trans., 92, 175 (2019).

[3] T. Suzuki, S. Okada and S. Tsushima, ECS Trans., 86, 193 (2018).

Acknowledgments

This work was financially supported by JSPS KAKENHI Grant Number 18K13702 and 18H01383. A part of this study was supported by the Osaka University Nanofabrication Platform [F-19-OS-0016] and [S-19-OS-0011] in the Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Figure 1
Understanding Pyrolysis: Operandoand in Situcharacterization of Morphology and Composition Changes during Synthesis of M-N-C Electrocatalysts
Authors: Chen Yechuan , Huang Ying , Asset Tristan , Kulkarni Devashish Shashikant , Xu Mingjie , Tieu Peter , Pan Xiaoqing , Zenyuk Iryna V. , Atanassov Plamen
Published: December 2020

Transition metal-nitrogen-carbon (M-N-C) materials have been continuously reported to be one of most promising platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR)/cathode in low-temperature polymer electrolyte fuel cells (PEFC) and other emerging areas (such as carbon dioxide reduction reaction and nitrogen reduction reaction). They are usually obtained through pyrolysis of low molecular weight (organic) or polymetric precursors. The pyrolysis consists of heat treatment in inert (or reductive) atmosphere. Through the decades of practice, this pyrolysis process has been optimized intuitively and empirically with little-to-no knowledge of the explicit sequence of transformations. Morphological, structural, interfacial and chemical changes during pyrolysis enable the emergence of the new material with atomically dispersed transition metal ions. These ions are incorporated in the graphene-like carbonaceous matrix, doped with nitrogen and forming various Fe-Nxcatalytically active sites. Often, a secondary pyrolysis process is being carries out, after the completion of the initial one, resulting in better defined, and in many cases, more active and stable catalysts (a.k.a. “re-pyrolysis”).

Our team have investigated both stages of the pyrolytic synthesis via in situXPS, TEM, EDS, XRD and nano- and micro-XCT methods in two separate studies dedicated to (i) pyrolysis of charge-transfer organic salt (nicarbazin) when mixed with silica template (a.k.a. “sacrificial support method” of M-N-C catalyst synthesis) and (ii) re-pyrolysis (secondary, “purification” pyrolysis) of the M-N-C material as a path to obtain atomically dispersed PGM-free catalyst.

During the first pyrolysis we have observed for the first time the explicit melting of the precursor (at exact thermal signature), wetting of the hard template and followed major transformation in morphology: pore structure evolution, initial graphitization, metal and metal carbide phase formation, secondary graphitization templated on the transition metal nanoparticles and secondary micro-pores formation. All these observations have been interpreted through cross-referencing tomography, crystallography, microscopy and spectroscopy in situdata streams.

We established that the re-pyrolysis of M-N-C materials could result in the amorphization of carbon, the rearrangement of multitudinous N-containing moieties, and increased content and a more uniform distribution of Fe-Nxsites, yet without major morphology changes in carbonaceous framework. In summary, the re-pyrolysis has multiple advantages and is recommended for all M-N-C electrocatalysts, no matter what precursors and parameters are set for their synthesis.
Probing the Performance-Degradation Interactions in the PEFC Catalyst Layer
Authors: Goswami Navneet , Grunewald Jonathan B , Fuller Thomas F. , Mukherjee Partha P.
Published: December 2020

Polymer Electrolyte Fuel Cells (PEFC) exhibit considerable performance decay with cycling owing to the degradation of Platinum (Pt) catalysts which results in loss of electrochemically active surface area. Strategies to prevent the Pt inventory loss in the cathode catalyst layer is thus a focal point in ameliorating the life expectancy of the PEFC. In this work, we present a thermo-kinetic model incorporating the various deleterious mechanisms occurring in tandem including Ostwald Ripening on carbon support, oxide coverage over the Pt particles and Pt dissolution, diffusion through the ionomer phase and reprecipitation reaction which is coupled with a microstructure resolved electrochemical performance model. The influence of microstructural features has been investigated to provide detailed insights of the transients of the participating phenomena that contribute to catalyst degradation. In addition to elucidating the spatial heterogeneity of degradation, we also demonstrate a representative temporal scale which is commensurate with the long-term aging behavior.
Double Point Temperature Measurements Under Rib and Channel in an Operating PEFC Using MEMS Sensors
Authors: Shigemasa Kaito , Otsuki Yota , Kurosu Masato , Sato Hayate , Araki Takuto
Published: December 2020

Introduction

For more spread of polymer electrolyte fuel cells (PEFCs), investigating the temperature distribution inside an operating PEFC is important. Last year, correlation between local through-thickness temperature gradient and the PEFC performance was investigated [1]. In this case, temperature gradient was critical to the PEFC performance under certain operating conditions. Moreover, local in-plane temperature gradient should be suggested as an important factor to the PEFC performance. Therefore, in this study, two local temperature measurement on the interface of the cathode catalyst layer (CL) and the microporous layer (MPL) in a PEFC was performed while it was operated.

Experimental method

Thin-Film Thermocouple (TFTC)

For the local temperature measurement inside a PEFC, in-house thin-film thermocouple (TFTC) was fabricated using micro electromechanical system (MEMS). The thermocouple was made from Au and Ni. Its measurement point was about 30 µm width and about 6 µm thick, which was so fine and thin that it wouldn’t disturb a reaction inside a PEFC.

Cell Configuration

An active area of 1 cm2 PEFC cell was used, and is has five 1mm width gas channels and five 1mm width ribs with parallel flow configuration. 15 µm thick reinforces type PEM was used. TGP-H-060 (with MPL 2.0 mg/cm2) was used and in both anode and cathode side. TFTCs were inserted between interface of cathode CL/MPL, and two TFTCs were set on rib and channel, respectively.

Operation Conditions

Power generation was performed by sweeping the cell voltage from OCV to 0 V at a rate of 1 mV/s. K-type thermocouples were used to measure the bi-polar plates with gas channels and sensor terminal temperatures. An impedance analyzer was used to measure the cell resistance. O2 and air were used as a cathode supply gas, respectively. Pure H2 was used as an anode supply gas. The flow rates of anode gas / cathode gas were set in two conditions, 500/500 mL/min, and 30/75 mL/min.

Results and Discussion

Here, results in one operating condition is being shown, when the high flow rate has been chosen, and O2 has been chosen as a cathode supply gas. Fig.1 (a) shows the cell voltage and cell resistance transition with current density. In this case, the cell voltage decrease due to diffusion overvoltage didn’t occur. And Fig.1 (b) shows the temperature increase from the beginning operating the PEFC on the CL/MPL interface under rib and channel. The temperature on the channel was higher than that on the rib. Due to the condensed water which was generated with the PEFC operation, the effective thermal conductivity got decreased. The amount of the condensed water on the rib was larger than that on the channel. Therefore, total amount of the condensed water might affect on the effective thermal conductivity and caused the temperature difference on the rib and channel.

Reference

[1] K. Shigemasa, et al., ECS Trans., 92(8),161-4 (2019)

Figure 1
Effect of Reformed Gas Components on the Operation of HT-PEMFC Stacks
Authors: Cremers Carsten , Bürger Stefan , Groß Martin Florian
Published: December 2020

Due to still existing limitations in logistic and some risk in handling of compressed gases hydrogen is not a suitable fuel for all applications which can profit from the use of fuel cells. In such cases the use of a downstream reformer to generate hydrogen from another fuel is a viable option. Fuel cell which can tolerate the impurities contained in the reformed gas will avoid the need of sophisticated gas clean-up. Such tolerance is obtained by increasing the operation temperature. BASF has already shown that their Celtec® MEA can tolerated substantial CO and H2S concentration1 which was confirmed by us for MEA of other manufacturers2,3. Here, the effect of impurities on the operation of HT-PEMFC stacks is investigated.

In this contribution investigations of the effect of impurities typically found in fuel gas obtained by auto thermal reforming of jet fuels is reported. Tests were conducted on Serenergy S165L-35 stacks with 35 cells of 165 cm2 geometric electrode area. Investigated were in detail the effect of dilution of hydrogen with nitrogen or CO2, the effect of fuel gas humidity and the effect of percent level CO and ppm level H2S impurities.

It was found that the performance of the stack at an anode stoichiometry of 1.4 is strongly influenced by hydrogen dilution (cf. fig 1a and b). Thereby no difference is found between dilution with N2 or CO2 (cf. fig. 2) indicating that no relevant reversed water gas shift reaction does occur. High levels of humidification with anode feed dew point exceeding about 60 °C also reduce the stack performance (cf. fig 3). This effect can again be correlated to the dilution with hydrogen (cf. fig. 4). However, after longer test with high due points stack performance is irreversibly reduced (cf. fig 5). Adding CO or H2S to diluted hydrogen further reduces the performance as expected. Unexpectedly the impact of the addition of CO is higher than that of H2S (cf. fig 6). Finally adding CO and H2S has a combined effect (cf. fig 7) though not as strong a described by Schmidt and Baurmeister1.

In the contribution further analysis of the different effects e.g, on cell voltage distribution will be given as well as the determination and validation of a suitable operating point for a jet fuel surrogate reformate.

The work was financial supported by the European Defence Agency (EDA) through the Ad-Hoc project “IAPUNIT” Contract B 1490 GEM 3 GP, jointly financed by the Federal Republic of Austria, the Federal Republic of Germany, the Kingdom of the Netherlands, the Republic of Slovenia and the Kingdom of Sweden.

References

T. J. Schmidt and J. Baurmeister, ECS Trans., 3(1), 861 – 869 (2006)

C. Cremers, M. S. Rau, A. Niedergesäß, K. Pinkwart, and J. Tübke, ECS Trans., 75(14), 919 – 929 (2016).

M. Rau, A. Niedergesäß, C. Cremers, S. Alfaro, T. Steenberg, H.A, Hjuler, Fuel Cells, 16(5), 577 – 583 (2016).

Figure 1
Design and Characterization of Porous Graphite Bipolar Plates for Water Management in PEM Fuel Cells
Authors: Pitchiya Aswin Prathap , Krishnan Sitaraman
Published: December 2020

Proton exchange membrane fuel cells (PEMFCs) are promising power-generation sources for mobile, stationary, and emergency backup power applications. Proper water management within the cell is crucial for the optimum performance and durability of PEMFCs. Excessive water leads to the flooding of the cathode compartment, while dehydration of the membranes results in increasing resistive losses. Therefore, water management is critical to the successful implementation of PEMFCs. To optimize the water balance, various designs have been proposed and tested. These approaches include the use of more complex diffusion media and microporous layers, liquid water injection, wicking of liquid water, and the use of different flow-field pathways1. The latter two approaches seek to enable self-humidification of the PEMFCs system, thereby decreasing the cost and parasitic power losses of external components such as humidifiers.

In this study, a porous hydrophilic bipolar plate with different pore structures were designed and characterized. Methods and compositions to produce fuel cell bipolar plates, with a porosity tailored for the desired up-take of water produced during fuel cell operation through capillarity, while offering sufficient resistance to permeability and leakage of gaseous fuel, are reported. The plates were composites of graphite (of different shapes and sizes) and polymer and were produced by a combination of powder or paste mixing, followed by compression molding and curing. Pore formation was engineered by adding a pore-forming agent2. Additionally, the pore surface was chemically modified using several surface modification methods.

A competitive plate design and fabrication technique is adopted in order to develop a low-cost, and light weight bipolar plates with improved mechanical and electrical conductivity and with exceptional hydraulic permeability and gas breakthrough pressure. The microporous bipolar plates developed in this research are promising for making water-management in PEMFCs simpler. The results of these studies will be presented and discussed.

References:

Wang, Y.; Diaz, D. F. R.; Chen, K. S.; Wang, Z.; Adroher, X. C., Materials, technological status, and fundamentals of PEM fuel cells–a review. Materials Today 2020,
32, 178-203.

Krishnan, S.; Harrington, M.; Pitchiya, A. P.; Putnam, Z.; Orlowski, D., Material Compositions And Methods For Porous Graphite-Polymer Composite Bipolar Plates. U.S. Patent Application 16/558,857: 2020.
(Invited) Curing Fuel Cell’s Alzheimer’s with Carbon Coatings for Stainless-Steel Bipolar Plates and a Healthy Lifestyle
Authors: Proch Sebastian Karl , Novalin Timon , Eriksson Björn , Bexell Ulf , Moffatt Claire , Westlinder Jörgen , Lagergren Carina , Wreland Lindström Rakel , Lindbergh Göran
Published: December 2020

Membrane/ionomer degradation in proton exchange membrane (PEM) fuel cells caused by Fenton-reaction of Fe and Cu species with hydrogen peroxide is not unlike the development of Alzheimer’s in the human body. Stainless-steel dissolution under fuel cell-relevant conditions takes place via passive-transpassive-passive transitions (Figure 1) [1]. Moreover, rapid load cycling and concomitant global hydrogen starvation during the New European Driving Cycle (NEDC) [2] are very likely to create such transitions. In their presence, metal-stained carbon-coated bipolar plates lead to significant contamination of the MEA with Fe and Ni. In contrast, the mitigation of global fuel starvation in the NEDC makes it possible for the same plates to exhibit trace-metal contamination of the MEA as low as a pure graphite current collector. However, during both runs the carbon coating ensures a constant and low contact resistance between bipolar plates and gas diffusion layers (GLDs). To take the Alzheimer’s analogy a step further, these experiments show that the way the fuel cell is run can be more important than the quality of the components. In other words, lifestyle might beat genetics.

At SMT we strongly believe in the power of carbon for electrochemical energy conversion due to its sustainability, low cost, high stability, high conductivity, and the absence of oxide film formation, thus, maintaining low contact resistance. We, therefore, offer (non-metal stained) carbon-precoated stainless steel for bipolar plates produced in a roll-to-roll fashion.

Figure
1
. Transient dissolution behavior of a typical stainless steel, e.g., 304L, 316L, 904L, considered are only Fe and Cr species for simplification. In a potential step from OCP (+0.7 V vs. RHE), where Fe and Cr species are insoluble, to ±0 V vs. RHE, where the Fe species is soluble, Fe is preferentially leached (red trace in the transpassive part) until an all-Cr passive film has been reestablished, which takes about 100 s. The red and blue traces correspond to the Fe and Cr signal of an ICP-AES coupled to a flow cell with a stainless steel sample [1].

[1] Li X, Zhou P, Ogle K, Proch S, Paliwal M, Jansson A, et al. Transient stainless-steel dissolution and its consequences on ex-situ bipolar plate testing procedures. Int J Hydrogen Energy. 2020;45:984-95.

[2] Tsotridis G, Pilenga A, De Marco G, Malkow T. EU Harmonised Test Protocols for PEMFC MEA Testing in Single Cell Configuration for Automotive Applications. Petten (The Netherlands): EU; 2015.

Figure 1
Phosphoric Acid-Doped Biphenyl-Backbone Ion-Pair Coordinated Pems with Broad Relative Humidity Tolerance
Authors: Tian Ding , Bae Chulsung
Published: December 2020

Fuel cell has been recognized as a promising electrochemical device attributed to its high energy efficiency and zero CO2 emission. As an essential component of fuel cell, currently the most widely used proton exchange membrane (PEM), Nafion®, operates only at low temperature (<100 ˚C) and high relative humidity (>80% RH). Although phosphoric acid (PA)-doped polybenzimidazole membranes have been reported to offer good proton conductivity at temperatures 140–180 ˚C, they suffer from severe performance degradation due to acid leaching when moisture is present. For wider adoption of PEM fuel cell technology, the development of PEM that is capable of working over a broad operating condition window is highly desirable. In this presentation, three PA-doped biphenyl-backbone ion-pair coordinated PEMs with different quaternary ammonium structures (alkyltrimethylammonium, piperidinium, and 1,2-dimethylimidazolium) were reported. The resulting PA-doped PEMs were comprehensively characterized in terms of PA doping level, proton conductivity, RH tolerance, thermal stability, and mechanical properties. Acid titration result indicates the PA doping levels of three membrane samples were between six and eight, and the size and structure of cation groups of the ion-pair polymers were found to affect their PA doping levels. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity was observed up to 70% RH at 80 ˚C for 10 h. A combination of high proton conductivity at low RH conditions and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as PEM fuel cell and electrochemical hydrogen compressor.
Comparison of Novel 1,1-Diphenylethylene Alternating Copolymer and Polystyrene Based Anion Exchange Membranes
Authors: Briem Musashi , Trant Carrie , Park Sungmin , Bae Chulsung , Lee Sangwoo
Published: December 2020

This research investigates 1,1-diphenylethylene as a monomer in polymeric ion exchange membranes through the synthesis of a novel alternating copolymer functionalized for ion transport and analysis of mechanical and conductive properties. This will further the development of cost effective and high-performance ion exchange membranes, enabling energy systems that employ ion-transporting membranes, like fuel cells and electrolyzers, to become more economically viable, which in turn would lead to cleaner and more sustainable energy production.

The goal of the project is to develop an understanding of chemical structure-physical property relationships to make self-assembling ion-conducting channels in ionomers which have physical properties that prevent the excess swelling that leads to the mechanical failure of membranes. In this vein, anion exchange membranes (AEMs) based on 1,1-diphenylethylene were synthesized and their ion conducting properties and physical state were characterized. Poly(1,1-diphenylethylene-alt-butadiene) alternating copolymer was synthesized via anionic polymerization, then selectively hydrogenated to eliminate double bonds in the polymer backbone. The pendant aromatic rings of the selectively hydrogenated poly(1,1-diphenylethylene-alt-butadiene) were then subjected to quantitatively controlled functionalized by super acid catalyzed Friedel-Crafts bromoalkylation, then aminated with trimethylamine. AEMs spanning a wide range of ion exchange capacities (IECs), 0.39-1.99 milliequiv./gram (meq./g), were made. Conductivity increased with IEC and temperature. Polystyrene based AEMs of similar IECs, 0.38-2.14 meq/g, were synthesized as a standard to compare the 1,1-diphenylethylene based copolymers. The 1,1-diphenylethylene based copolymers had favorable conductivities compared to polystyrene membranes of similar IEC. The glass transition temperature, water uptake, and dimensional swelling were investigated to explain the difference in conductivities between the two species.

Figure 1
Pore-Filled PEMs from Poly(Phenylene Sulfonic Acid)s and Electrospun Poly(Phenylene Sulfone) Fiber Mats
Authors: Wycisk Ryszard , Hossain M. , Shang Z. , Pintauro Peter N.
Published: December 2020

Novel, composite, non-PFSA-based fuel cell membranes have been fabricated using a pore filling technique. The membranes consist of a mechanically stabilizing skeleton from an electrospun poly(phenylene sulfone) (PPSU) fiber mat and a thermally crosslinkable poly(phenylene sulfonic acid) (cPPSA) proton conducting ionomer that fills the interfiber voids. The work builds on two prior studies carried out in the labs of Prof. M. Litt and Prof. P.N. Pintauro demonstrating: (1) Exceptionally high proton conductivity, even at very low RH (down to 20% RH), of cPPSA solution cast films, and (2) Excellent durability of electrospun perfluorosulfonic acid (PFSA) ionomers/PPSU composite membranes, exceeding that of the pristine PFSA. Unfortunately, the high proton conductivity of cPPSA films, especially at low relative humidity, was offset by their significant brittleness, which made handling of those materials, including fabrication of membrane-electrode-assemblies, extremely difficult. The proposed pore-filling strategy should alleviate the brittleness problem leading to a robust, low RH-conductive PEM that is a true competitor to PFSA membranes and suitable for commercial applications.

Experiments focused on optimizing the cPPSA/PPSU ratio to achieve the desired balance of tensile strength and proton conductivity, and on minimizing membrane thickness to obtain area specific resistance (ASR) lower than 0.02 S/cm in the 40-90% RH range at 80oC. cPPSA copolymer was synthesized using Ullmann coupling copolymerization of 4,4′-dibromobiphenyl 3,3′-disulfonic acid with 1,4-dibromobenzene-2,5-disulfonic, followed by grafting certain fraction of backbone sulfonic acid groups with biphenyl linker [1]. The PPSU fiber mat was electrospun from NMP/acetone solution. Pore-filling was carried out by pouring a solution of cPPSA in methanol over the framed mat, followed by heating at 70oC to evaporate solvent. The cPPSA was crosslinked by an additional heating step, in a vacuum oven at 210oC for 1-2 hours. The resultant membranes had excellent proton conductivity, 5-10 times greater than that of Nafion® 211 in the 40-90% RH range at 80oC. Details of the membrane fabrication and characterization work will be presented in this talk.

[1] M. Litt and R. Wycisk, Poly(Arylenesulfonic Acids) with Frozen-In Free Volume as Hydrogen Fuel Cell Membrane Materials, Polymer Reviews, 55, 307 (2015).
(Invited) Engineering Polypeptides for Controlled Assembly of Ionomer Thin Films
Authors: Renner Julie N.
Published: December 2020

Increasing evidence suggests that control of ionomer thin film structures on metal surfaces is pivotal for efficient performance in electrochemical devices such as fuel cells and electrolyzers. Unfortunately, the assembly of these thin film structures is difficult to control using conventional methods and ideal arrangements remain unknown. Engineered polypeptides have emerged as powerful biomolecular tools in electrode assembly because binding sites and polypeptide structures can be easily modulated by changing the amino acid sequence. However, no studies have been conducted showing polypeptides can be engineered to interact with ionomers, attach them to metal surfaces, and control their arrangement. Our lab has recently developed this technology, using an elastin-like polypeptide to bind to metals, and bind to acidic and basic ionomer via ionic interactions. We use a quartz crystal microbalance with dissipation to provide detailed information about the loading, thickness, and binding behavior of the polypeptide and ionomer layers. We also use atomic force microscopy and grazing-incidence small-angle X-ray scattering to understand the impact of the biomolecules on ionomer phase separation. Finally, we have begun to analyze the performance (ionic conductivity) of the assembled films using interdigitated electrodes and electrochemical impedance spectroscopy. Through these techniques, we show that 1) our biomolecular system is highly flexible, easily adapting to different materials, 2) the polypeptide sequence can dictate ionomer phase separated structures, and 3) this system can be used to improve the performance of ionomer thin films and gain structure-function understanding. Generally, our results demonstrate that engineered polypeptides are promising tools for ionomer control in electrode engineering.
(Invited) Gel Polymer Electrolytes with Postinjection Gelation and High-Voltage Features for Double Layer Capacitors
Authors: Su Yi-Han , Teng Hsisheng
Published: December 2020

For ensuring safety and for the development of flexible devices, gel polymer electrolytes (GPEs) are ideal substitutes for the liquid electrolytes (LEs) currently used in batteries and capacitors. However, the use of GPEs is limited by the liquid injection assembly line currently used in battery and capacitor manufacturing. This study reports electric double layer capacitors (EDLCs) made from a postinjection gelated GPE, which is synthesized by mixing poly(acrylonitrile-co-methyl acrylate) and LE. This research indicates that the functionalities on the polymer chains of the GPE facilitate the dissociation of ion pairs and suppress the formation of ion-solvent complexes. Therefore, the ionic conductivity of the GPE is an order of magnitude higher than that of the LE. Under polarization for dielectric analysis, the GPE exhibits high storage permittivity and low loss permittivity because of its swift ion motion and polymeric dipole orientation. The cycling stability and energy and power densities of the resulting GPE-EDLC are higher than those of the LE-EDLC. As incorporated with graphene-based materials, this GPE exhibits low flammability and high voltage stability. The postinjection gelation feature and outstanding electrochemical properties of this GPE enable its industrial application.
Kinetics of Lithium Insertion and Plating on Basal and Edge Planes of Graphite
Authors: Schnabel Manuel , Kostecki Robert
Published: December 2020

Lithium-ion batteries (LIBs) with graphitic anodes dominate the energy storage market1, 2, and it is of interest to accelerate charging of LIBs for a number of applications, especially electric vehicles. A common issue upon fast charging is that parts of a graphitic anode are polarized to negative voltages vs Li/Li+, leading to lithium plating3. The reversibility of Li plating on graphitic anodes is poor, and Li plating leads to exothermic reactions with standard electrolytes, and can lead to dendrite growth and shorts in the cell3. It is therefore of interest to understand the onset of Li plating, and the maximum current that can be sustained without plating.

In commercially relevant cells such measurements are complicated by the three-dimensional porous composite nature of the anode and its interaction with an electrolyte whose lithium concentration at the interface with the graphite varies as a function of depth within the electrode during fast charging4, 5. The goal of our work is to determine the fundamental kinetics of Li intercalation and plating at edge and basal plane graphite surfaces by performing fast charging experiments using highly oriented pyrolytic graphite (HOPG) samples.

HOPG consists of a stack of graphite planes, with in-plane grain sizes on the order of 0.1 mm, enabling such measurements at a well-controlled current density. We confirm that Li intercalation occurs almost exclusively at edge planes, and show that current densities above 1 mA/cm2 can be sustained at pristine edge surfaces (see figure, which shows potential as a function of linearly increasing current density). We also show that Li plating can nucleate on both edge and basal planes with an overpotential below 0.1 V, and explore the differences in Li insertion rate and plating overpotential for different stages of graphite.

Funding was provided by the U.S. DOE Office of Vehicle Technology Applied Battery Research and Extreme Fast Charge Program (XCEL).

T. Placke, R. Kloepsch, S. Dühnen and M. Winter, Journal of Solid State Electrochemistry, 2017, 21, 1939-1964.

N. Nitta, F. Wu, J. T. Lee and G. Yushin, Materials Today, 2015, 18, 252-264.

Q. Liu, C. Du, B. Shen, P. Zuo, X. Cheng, Y. Ma, G. Yin and Y. Gao, RSC Advances, 2016, 6, 88683-88700.

A. M. Colclasure, A. R. Dunlop, S. E. Trask, B. J. Polzin, A. N. Jansen and K. Smith, Journal of The Electrochemical Society, 2019, 166, A1412-A1424.

A. M. Colclasure, T. R. Tanim, A. N. Jansen, S. E. Trask, A. R. Dunlop, B. J. Polzin, I. Bloom, D. Robertson, L. Flores, M. Evans, E. J. Dufek and K. Smith, Electrochimica Acta, 2020, 337, 135854.

Figure 1
Graphite Lithiation Under Fast Charging Conditions: Atomistic Modeling Insights
Authors: Garcia Juan , Bloom Ira , Johnson Christopher S. , Dees Dennis W. , Iddir Hakim
Published: December 2020

Charging lithium ion batteries in a fast and safe manner is critical for promoting mass adoption of electric vehicles. Li intercalation in graphite electrodes is known to be one of the bottlenecks during the fast charging process. The mechanism of Li diffusion in highly polarized graphite anode at high current rates remains, however not well understood. Herein, Density Functional Theory (DFT) calculations are used to gain insights into the Li diffusion process in graphite when far from equilibrium under fast charging conditions. The effect of uncompensated charges on Li mobility is determined in the highly polarized regions of the anode close to the interfaces. The extra charge was found to increase the interlayer spacing in the diffusion layer and adjacent channels, increasing the diffusivity, altering the staging mechanism, and promoting the formation of Li clusters. A concerted diffusion mechanism at the edge of high-concentration Li domains is proposed to enhance the diffusion of Li.
(Invited) Rechargeable Zn-Ion Batteries Via Multifunctional 3D Electrodes and Mixed-Salt Electrolytes
Authors: Sassin Megan B. , Helms Maya E , Parker Joseph F. , Chervin Christopher N. , Ko Jesse S. , Rolison Debra R. , Long Jeffrey W.
Published: December 2020

We recently demonstrated that advanced multifunctional 3D MnOx@carbon nanofoam (MnOx@CNF) electrodes cycled in mixed-salt aqueous electrolytes
[1]
extend the performance advantages of rechargeable “zinc-ion” batteries, an emerging energy-storage technology with inherent cost and safety benefits.
[2],[3]
The combination of the multifunctional birnessite-MnOx@CNF and mild-pH Zn2+-containing electrolyte results in a complex charge-storage mechanism in which a H+ inserts into the birnessite-MnOx during discharge, resulting in an increase in the local pH that triggers precipitation of Zn4(OH)6SO4·5H2O, while Na-ions support pseudocapacitance reactions.
[4]
This dual charge-storage mechanism yields high capacity at low rates (308 mA h g-1 at 1C, MnOx theoretical capacity) and pulse power at high rates (100 mA h g-1 at 20C) via pseudocapacitance; these mechanisms are reversible over hundreds of cycles, attributed in part to the through-connected pore structure of the CNF. In order to explore the efficacy of other MnOx polymorphs in such 3D multifunctional electrode designs, we developed an “in-place” conversion to generate nanocrystalline ZnMn2O4 spinel from the birnessite-MnOx coating on the CNF. Crystallization is achieved by heating at relatively mild temperatures (300°C), such that the nanoscale morphology of the original MnOx coating and through-connected pore structure of the underlying CNF are maintained. We used a suite of ex-situ characterization methods (SEM/EDS, XRD, XPS) to elucidate the charge-storage reaction of ZnMn2O4@CNF in 1 M ZnSO4 and found that it is even more complex than the charge-storage mechanism of birnessite-MnOx@CNF. Discharge of ZnMn2O4@CNF proceeds via two steps, the first occurring by Zn2+ insertion into the spinel and the second by H+ insertion accompanied by Zn4(OH)6SO4·5H2O precipitation; the reaction reverses upon recharge. We will discuss the implications of these mechanisms for such performance characteristics as rate capability and cycle life in their ultimate application as positive electrodes in next-generation zinc-ion batteries.

[1]. J.S. Ko, M.B. Sassin, J.F. Parker, D.R. Rolison, and J.W. Long: Combining battery-like and pseudocapacitive charge storage in 3D MnOx@carbon electrode architectures for zinc-ion cells. Sustainable Energy Fuels
2, 626–636 (2018).

[2]. B. Tang, L. Shan, S. Liang, and J. Zhou: Issues and opportunities facing aqueous zinc-ion batteries. Energy Environ. Sci. 12, 3288–3304 (2019).

[3]. L. E. Blanc, D. Kundu, and L. F. Nazar: Scientific Challenges for the Implementation of Zn-Ion Batteries. Joule
4
, 771–799 (2020).

[4]. J.S. Ko, M.D. Donakowski, M.B. Sassin, J.F. Parker, D.R. Rolison, and J.W. Long: Deciphering charge-storage mechanisms in 3D MnOx@carbon electrode nanoarchitectures for rechargeable zinc-ion cells. MRS Communications
9, 99–106 (2019).
Polycyclic Quinone and Its Dithiin Derivative As Cathode Materials for Sustainable Aqueous Zn-Organic Secondary Batteries
Authors: Mirle Chinmaya
Published: December 2020

Aqueous Zinc-ion (Zn-ion) batteries are considered as attractive energy storage devices for large scale applications owing to their intrinsic safety, low cost and robustness1. However, their implementation is held back by sluggish diffusion kinetics of Zn2+ into inorganic host materials. Therefore, the focus is on redox active organic materials particularly quinone derivatives. These materials show moderate coulombic repulsions to the Zn2+ diffusion by having big tunnels in the crystal lattice2. Yet, very few organic materials have been reported for aqueous Zn-ion batteries. In the contextual importance of exploring new organic materials that can reversibly host Zn2+. Herein, we have explored highly conjugated pentacene-5,7,12,14-tetraone (PT) as cathode material for aqueous ZIBs for the first time. The versatile features such as strong π-stacking, high theoretical capacity (i.e. 317 mAh g-1 for 4e- transfer), structural diversity, inherent insolubility and non-defamation upon electrochemical process unlike simple quinones make PT a promising candidate to study. Moreover, we used filter paper as a separator instead of nafion membrane and ZnSO4 as supporting electrolyte salt which makes this battery more environmentally friendly and cost effective. In order to improve the rate capability and cycling stability, PT was incorporated in the mesoporous nanonetwork of CMK-3 carbon. In addition, the discharge voltage of the cell was enhanced by introducing sulfur atoms in the PT skeleton.

Figure 1
Controlled Growth and Morphological Evolution of Nico Hydroxides for High Performance Hybrid Supercapacitor Applications
Authors: Baek Seong-Ho , Jeong Young-Min
Published: December 2020

The capacity of pseudocapacitors can exceed that of traditional electrostatic or electric double-layer capacitors, and they can also provide faster power delivery and longer cycling stability than lithium-ion batteries. In this work, we investigate the effect of solvent on the morphological change of NiCo hydroxides during hydrothermal synthesis according to mixture ratio of ethanol and water. We elucidate the phase of NiCo-layered double hydroxide (LDH) transformed to NiCo-carbonate hydroxide (CH) and morphological evolution of nanosheets to nanowire structures by adding ethanol in solution. The experimental results confirm that an increase of carbonate anions caused the phase and morphology of NiCo-LDH to transform into NiCo-CH. The hierarchically structured electrodes achieve excellent electrochemical performance, with a capacitance of 1,298 Fg-1 due to their structural benefits, which provide effective electrolyte transport, electron transfer, and active site accessibility.

Figure 1
Development of High Volumetric Mg-Ion Storage Capacitance with Electrochemical Activation of 2D MXene-Based Hybrid Material
Authors: Jung Mingyu , Nakhanivej Puritut , Park Ho Seok
Published: December 2020

Hybrid capacitors have played an important role in Energy storage field nowadays due to their high power capabilities and superb cycle life, while having higher specific energy density than traditional EDLC typed one. Usually this is realized by assembling an asymmetric cell with an electric double layer capacitor and searching for alternative energy storage system using multivalent cations. However, existing carbon based electrodes which are applying for volumetric capacitances have remarkable limitation at around 60 F/cc due to its low material density. Recently, a new family of 2D transition metal carbide known as MXene is standing in a spotllight because it represents a type of 2D material that has demonstrated many possibilities in electrochemical energy storage applications. Here, we suggest that MXene/graphene hybrid material which can be providing hierarchical structure, which is benifit to the ion diffusion and decrease the charge transfer resistance. Thus, our hybrid electrode and electrochemical activation approach opens new avenues to store Mg and other multivalent ions for high volumetric capacitance of electrochemical capacitors
High Performance Lithium Battery Anodes from Non-Water Based Graphene
Authors: Dada Oluwaseun John
Published: December 2020

High performance lithium battery anode plates were made from processed arc discharge graphene. Arc discharge graphene has been produced from glow electrolytic thermal arc discharging of graphite rods [1-3], different from graphene or reduced graphene prepared through other means [4-11], because it maintains high crystallinity and planar characteristics of graphite marked by low ID/IG and XRD peak (2θ = 26 ⁰C). Arc discharge Graphene was sonicated in NMP for hours until fully exfoliated and able to film coat without impediments on the rougher side of the electrode copper film. Sonicated Graphene was dried in the vacuum oven. Anode plates were prepared by homogenizing the sonicated graphene in PVDF saturated NMP (0.53% NMP; 4% superP carbon black; and 2.25wt% PVDF) for 1 hr. The anode slurry was coated on the copper plates using automatic doctor blade film coater at a speed of 100mm/min. Anode plates were dried at 80 ⁰C for and cured for 120 ⁰C for 2 hrs in vacuum oven. Coin cells of NMC//HGR were made and tested in CT2001A. The capacity of the anode cycled at 1C was ~1083mAhg-1. This very high capacity of the graphene anode represents 188.3% increase over nominal graphite anodes, and one of the highest reported in published literature.
Preventing Lithium Plating during Fast Charging of Lithium-Ion Cells
Authors: Bohinsky Amy , Perumaram Rangarajan Sobana , Barsukov Yevgen , Mukherjee Partha P.
Published: December 2020

Fast charging of lithium ion batteries is currently limited by lithium plating occurring on the anode. During fast charging, the electronic and ionic kinetic limitations cause the potential on the anode surface to decrease below that of metallic lithium, making lithium plating preferred to intercalation inside graphite particles. The plated lithium reacts with the electrolyte forming a passivation layer and may also form dendrites and/or become electrically detached, all resulting in accelerated capacity fade and safety issues. In this work, a battery management system (BMS) module was used to fast charge a commercial pouch cell without lithium plating. The BMS measures full cell voltage to control the charging current to account for reduced intercalation kinetics at high states of charge preventing lithium ion accumulation and inhibiting plating. A three-electrode pouch cell was cycled using the BMS module so that the anode potential could be independently monitored to verify that plating was prevented.
(Invited) Anthraquinone on Carbon: Is There Any Way to Get It Working?
Authors: Zhu Yachao , Deschanels Mathieu , Le Vot Steven , Fontaine Olivier , Favier Frederic
Published: December 2020

Grafting redox active moieties, including anthraquinone, on large surface area carbons has been for long considered has a good opportunity to increase the energy density of electrochemical capacitors. From the CVs, usually looking like the merging of redox and capacitive signals, the storage capability obviously takes benefit from both contributions. Unfortunately, performances are not fully met: when increasing the anthraquinone loading above 10-15 w%, the double layer contribution decreases because of pore clogging. Cyclability is also poor: during the first few hundreds of cycles (often less), the capacity is progressively fading down because of either physisorb anthraquinone molecules being washed away from the carbon surface and molecule degradation.

Various approaches have been considered to address these limits. This paper is an introduction to two of those we have explored. The first one consists in the covalent grafting of an anthraquinone propargyl molecule by a Diels Alders reaction using carbon surfaces as dienophyl. For the second, anthraquinone molecules are first simply adsorbed at the carbon surface. In a second step, flakes from exfoliated MXene are deposited on top of the anthraquinone film by dip-coating. This carbide shell provides the resulting composite some extra electronic conductivity while allowing the electrolytic species to reach both anthraquinone and carbon thanks to its open structure. Attractive electrochemical characteristics have been obtained from electrodes based on these two different materials. These are discussed based on the compositions and morphologies of the prepared composite materials.

References

Brousse, T.; Cougnon, C.; Bélanger, D., Grafting of Quinones on Carbons as Active Electrode Materials in Electrochemical Capacitors. Journal of the Brazilian Chemical Society
2018,
29, 989-997.

Pognon, G.; Brousse, T.; Demarconnay, L.; Bélanger, D., Performance and stability of electrochemical capacitor based on anthraquinone modified activated carbon. Journal of Power Sources
2011,
196 (8), 4117-4122.