bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Concentrated Hydrogen Bonded Electrolytes: Definition and Bulk & Interfacial Properties
Authors: Gurkan Burcu , Dean William , Penley Drace
Published: November 2022

We broadly refer to deep eutectic solvents (DESs) as concentrated H-bonded electrolytes (CoHBEs) where a composition specific to the “deep eutectic temperature” does not have to be met as long as the electrolyte possesses high salt concentration of the salt or the redox active specie and suppressed volatility are desired in energy storage, electrocatalysis, and electrodeposition processes. Liquid heterogeneity owing to H-bonding, similar to ionic liquids and DESs, CoHBEs present distinct electrode-electrolyte interfacial behavior.

As a way to probe the electrode-electrolyte behavior of CoHBEs as a function of composition, we have performed electrochemical impedance spectroscopy and surface enhanced Raman spectroscopy (SERS). The potential dependent differential capacitance of choline chloride and ethylene glycol (1:2, 1:4, 1:6 molar ratio) mixtures do not present camel shaped curves as in the case of more extreme examples of concentrated electrolytes such as ionic liquids. The interfacial behavior is more similar to dilute systems, however, the H-bonding network presents a less mobile diffuse layer. While on glassy carbon, there is no specific ion adsorption, on metal electrodes chloride adsorption is observed. In chloride-free systems that are based choline oxalate mixed with ethylene glycol, capacitance is measured to be almost independent of the applied voltage on glassy carbon and gold. This is attributed to the strong binding energy of the solvation structure, as determined from theory, that hinders voltage-induced reorientations. Consistent to this behavior, the oxalate system also presents a very high viscosity. In addition, the voltage sweep range is limited in the case of oxalate system as it has narrower electrochemical window. On the other hand, choline acetate, which has a very similar chemical structure to the oxalate, undergoes specific ion adsorption particularly on gold electrode at a positive applied potential as confirmed by SERS. This is believed to be due to the reduced binding energy as calculated by density functional theory with -1 charge of the acetate in comparison to -2 charge in oxalate that leads to the desolvation and then the surface adsorption of the acetate. In the case of the choline bis(trifluorosulfonyl)imide and ethylene glycol mixture, a wider electrochemical window accompanied by a dampened u-shaped capacitance was observed with no specific ion adsorption.

This study presents tuning of DESs and more broadly CoHBEs in terms of the bulk physical properties, the interfacial behavior near an electrode, and the coupled structuring effects through the variation in anion charge density and the extent of H-bonding.
(Invited) Functionalized Water-Mimicking Ionic Liquids for Biocatalysis
Authors: Zhao Hua , Martin Caden , Baker Gary , Mitchell-Koch Katie
Published: November 2022

Enzyme activity in organic solvents is usually much lower than its performance in aqueous media. To develop water-mimicking environment for the enzyme, we designed ionic liquids functionalized with tert-alcohol (as hydrogen-bond donor) and ether groups (as hydrogen-bond acceptors). These “water-like” ionic media have high thermal stability and low viscosities, and produced higher lipase and protease activities and stabilities than some enzyme-compatible organic solvents (such as tert-butanol and diisopropyl ether) and conventional ionic liquids (e.g., [BMIM][Tf2N]) during transesterification reactions under low water contents. In addition, these unique ionic solvents are found suitable media for asymmetric synthesis. Our experimental and MD simulations data illustrate the interactions between these water-mimicking solvent molecules and the enzyme.
Fundamental Understanding of Water's Role in the Oxygen Redox Process in Ionic Liquids
Authors: Witherspoon Erin , Wang Zhe
Published: November 2022

The O2/O2
•- redox couple is of particular interest for use in energy storage technology due to its abundance, sustainability, and potentially high energy density. Conversely, in the presence of a proton source, such as water, the O2/O2
•- redox couple may become unstable and irreversible. However, the fundamental understanding of this process is still not clear. In this work, O2/O2
•- redox process has been investigated in the presence of water using electrochemistry combined with in-situ spectroscopic methods in ionic liquid media. The findings for the redox reaction of oxygen in ionic liquids reported here indicate a complex mechanism on different electrode surfaces. This study is to elucidate the mechanism and reaction intermediates; it will also provide a fundamental understanding of oxygen chemistry and ionic liquid green chemistry for future emphasis on batteries, fuel cells, and gas sensor applications.
Redox Couple Stability Studies for Thermodynamic Reference Electrodes and Fluoroacidity Investigation
Authors: Williams Haley , Scarlat Raluca O.
Published: November 2022

A stable reference electrode is essential for electrochemical studies in molten fluoride salts, yet reference electrode design is hindered by challenges such as materials compatibility and high temperature operation. Electroanalytical studies are relevant to sensor development for molten fluoride salt systems as well as fundamental chemistry studies of salt structure and speciation. Dynamic reference electrode techniques have been used to find benchmark reference potentials, but the application of a constant current for the technique may not be feasible for sensing or high throughput studies. A thermodynamic reference electrode which is durable, stable, and reproduceable is urgently needed for both scientific studies and engineering applications of molten fluoride salts.

Fluoroacidity studies are of particular interest for a fundamental understanding of molten salt speciation. The more dissociated fluoride anions present in a melt, the more of a fluorodonor it is. Thus, it is considered to have a higher fluorobasicity due to its Lewis base behavior. Fluoroacidity is related to the coordination of solvent and solute ions and, therefore, solute diffusion coefficients and viscosity. Ion solvation differs in fluoride salts of various fluoroacidities, so solvated ions have different activity coefficients in different fluoride solvents. The relationship between activity coefficients of solvated ions and a melt’s fluoroacidity is not fully understood. The electrochemical determination of these activity coefficients benefits from a stable reference electrode. In addition, quantification of fluoroacidity requires the measurement of the activity of dissociated fluoride, which can be done electrochemically. The measurement of redox potential of a given couple in various fluoride melts can lead to a classification of the solvent melts based on the Nernst equation. Therefore, the study of redox couple behavior in various fluoride melts is relevant to both the development of a robust thermodynamic reference electrode & the quantification and theory of fluoroacidity.

The Ni/NiF2 and Ag/AgF redox couples have been previously investigated for use in thermodynamic reference electrodes for molten fluoride salt. Ni/NiF2 has been characterized for its stability in molten fluorides. The Ag/AgCl redox couple has commonly been used for chloride mixtures but literature on the fluoride couple is marginal. Our preliminary studies have shown the stability of the Ag/AgF redox couple in a FLiNaK melt by OCP measurement. Polarization studies will be carried out to test for reversibility, and other redox couples may be investigated. In this presentation, we present results from the Ag/AgF redox couple studies in FLiNaK, as well as their impact on current understandings of fluoroacidity.
Up-Scaling and Stabilization of Processes for the Electrodeposition of Aluminum Alloys for Corrosion Protection
Authors: Böttcher Rene , Ispas Adriana , Bund Andreas
Published: November 2022

Aluminum and its alloys have excellent properties (e.g. specific weight, corrosion resistance) that are beneficial for a wide range of industrial applications. By forming a natural oxide layer of a few nm thickness, these materials are able to protect themselves from the progression of corrosive attack. Unfortunately, this oxide layer limits the use of pure aluminum for cathodic corrosion protection. Adding the right alloying elements can help to prevent the formation of the oxide layer and thus self-passivation.

Electrodeposition is an elegant and cost-efficient method to deposit thin films on substrates with complex shapes. The choice of the electrolyte, its composition and the deposition parameters allow the tuning of the layer properties. Electroplated aluminum materials open up the possibility of replacing environmentally hazardous materials such as cadmium. Aluminum cannot be electrodeposited from aqueous electrolytes due to its negative Nernst potential (-1.66 V vs. NHE). Non-aqueous media make this possible due to large electrochemical windows. However, they are often limited by expensive and highly flammable chemicals (e.g. SIGAL and REAL process). High investment costs for process and plant technology are the consequence. Ionic liquids (ILs) allow the deposition of reactive metals such as aluminum at room temperature. They have a very low vapor pressure and are non-flammable. In addition, they exhibit good solubility for numerous metal salts and lower differences in the deposition potentials of the metals.

This paper discusses the use of imidazolium-based chloroaluminate ILs for the electrochemical deposition of aluminum alloys for cathodic corrosion protection of high-strength steel. As an essential part of upscaling IL-based processes, the use of multianodes, their limitations, and the use of additives to optimize the deposition process and the coating properties will be discussed.
(Invited) Promises and Challenges of Multivalent Ion Battery Chemistries
Authors: Ma Lin , Schroeder Marshall , Pastel Glenn , Borodin Oleg , Pollard Travis , Ding Michael , Ho Janet , Cresce Arthur v. , Xu Kang
Published: November 2022

Extensive efforts have been made to seek new battery chemistries based on multivalent working ions, with the aim to replace the mature lithium-ion batteries. These efforts were initially driven by the pursuit of higher capacity/energy, better safety and lower cost, and more recently have significantly intensified with the increasing concerns over the climate change, the limited resources of Co and Ni, and the anxieties over geopolitical as well as ethical risks of the corresponding supply chain. But how far are we from a practical multivalent battery?

This talk rigorously examines the achievements made in MV batteries as reported in the current literature, while attempting to explore a pathway through the fog-of-war ahead of us.
Electrolyte-Centric Thermal Model of Li-Ion Battery Under Abuse Conditions
Authors: Guillamon Joaquin I. , Verma Amit
Published: November 2022

Safety is an important concern in Li-ion battery operation and storage. As both energy stored per unit volume and current densities have increased in these batteries, energy dissipation in the form of heat has become one of the main issues for proper battery operation. As temperature increases, secondary chemical reactions may be initiated. These reactions release more heat and undesired products, triggering an auto-catalytic feedback process, commonly classified as thermal-runaway mechanisms. This can potentially lead to a complete degradation of the battery and possible explosion or combustion of the battery components.

Several researchers have worked on developing models to predict thermal behavior under conditions with potential thermal runaway outcomes on Li-ion batteries. The first studies proposed a model that emulates the solid electrolyte interface (SEI) decomposition and regeneration reactions on a standard 18650 cylindrical cell. Later works extended these models and included the reactions of cathode decomposition and electrolyte decomposition with potential combustion. Although macroscopic level energy balance helps predict potential thermal behavior in a battery of multiple layers, the study of all the different transport mechanisms that happen inside a single layer battery is essential for a better understanding of the process taking place when temperature begins to rise. With the aim of improving heat dissipation inside a battery, the electrolyte is a key component to consider as it can potentially handle heat flux easier through convection within the solution.

Our work investigates spatially dependent electrolyte conditions in the presence of a thermal gradient to produce an electrolyte-centric thermal runaway model. Non-current conditions are considered for emulating oven-test experiments or storage conditions. Furthermore, this specific case study aims to extend our previous model by accounting for the influence of the Joule effect on simulating a battery's operational conditions. The purpose of the study is to model transport mechanisms that can potentially lead to thermal degradation of the battery. Li-ions, momentum, and thermal flux are the main components of the analysis. This objective is achieved by using numerical simulation techniques. A detailed understanding of the transport processes taking place inside the battery will contribute towards mitigating damage induced due to thermal abuse conditions.

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Electrolyte Channel Design By Physical Model and Machine Learning
Authors: Gao Tianhan , Lu Wei
Published: November 2022

Thick electrode is highly effective to increase the specific energy of a battery cell, but the associated increase in transport distance causes a major barrier for fast charging. We introduce a bio-inspired electrolyte channel design into thick electrodes to improve the cell performance, especially under fast charging conditions. The effects of channel length, width, tapering degree and active material width on the electrochemical performance and mechanical integrity are investigated. Machine learning by deep neural network (DNN) is developed to relate the geometrical parameters of channels to the overall cell performance. Integrating machine learning with the Markov chain Monte Carlo gradient descent optimization, we demonstrate that the complicated multivariable channel geometry optimization problem can be efficiently solved. The results show that within a certain range of geometrical parameters, the specific energy, specific capacity and specific power can be greatly improved. At the same time, the maximum first principal stress which is in the cathode region next to the separator can be significantly reduced, giving better mechanical integrity. Comparing to conventional designed cells without electrolyte channels, we show a 79% increase in specific energy using channel design optimization. This study provides a design strategy and optimization method to achieve significantly improved battery performance
(Invited) 4C 15-Minute Fast-Charging Li-Ion Battery Enabled By Novel Electrolytes
Authors: Gao Tao
Published: November 2022

Electrifying our transportation is one key step to decrease human society’s fossil fuel consumption, therefore, reducing CO2 emissions. In the past decade, electric vehicles (EVs), especially electric passenger cars, are successfully commercialized and are gaining increasing market shares. Most of these EVs are powered by Li-ion batteries (LiBs) due to their high performance over other alternative vehicle power sources. After three decades of development, the energy density of LiBs has steadily increased to >250 Wh/kg at the cell level, which enables EVs with a comparable drive range to their gasoline counterparts. However, the charging time of LiBs is much longer than the refueling of a gasoline tank. The current battery technology can only achieve 80% charge for >30-40 minutes at a high temperature (40-50°C), which falls short of the U.S. Department of Energy (DOE)’s target of 80% charge within 10 minutes. Achieving such a super-fast charging performance without degrading battery life is a challenge that still has not been solved.

In this talk, I will discuss our latest findings that by engineering the composition of the electrolyte, the charging performance of LiB can be significantly enhanced. When compared with the commercial carbonate electrolytes (1M LiPF6 in EC-DMC, LP30; or 1M LiPF6 in EC-EMC, LP50), our electrolytes show remarkably better charging performance at all charging rate > 1C. Some formulation of our electrolyte is able to deliver >80% charge at 4C rate within 15 minutes at room temperature. I will discuss our fundamental study to understand the mechanisms underlying the remarkable charging performance of our electrolytes compared to the commercial carbonate electrolytes.
Carbon-Binder Optimization for Lithium-Ion Battery Extreme Fast Charge
Authors: Usseglio-Viretta Francois L. E. , Colclasure Andrew M. , Dunlop Alison , Trask Stephen E. , Jansen Andrew N. , Abraham Daniel P. , Rodrigues Marco-Tulio F , Dufek Eric J. , Tanim Tanvir R. , Chinnam Parameswara R. , Ha Yeyoung , Smith Kandler
Published: November 2022

Battery performance is strongly correlated with electrode microstructure and weight loading of the electrode components. Among them are the carbon-black and binder additives that enhance effective conductivity and provide mechanical integrity. However, these both reduce effective ionic transport in the electrolyte phase and reduce energy density. Therefore, an optimal additive loading is required to maximize performance, especially for fast charging where ionic transport is essential. Such optimization analysis is however challenging due to the nanoscale imaging limitations that prevent characterizing this additive phase and thus quantifying its impact on performance.

In this work [1], an additive-phase generation algorithm [2] has been developed to remedy this limitation and identify percolation threshold used to define a minimal additive loading (cf. figure, left). Impact of carbon-black binder (CBD) loading on electrochemical performance has been investigated through a wide array of numerical methods and experiments on NMC/graphite cells. These range from the representation, characterization, and homogenization of electrode microstructures, battery macroscale modeling, and impedance and rate capabilities measurements on various cell formats. The combined work provides information on connectivity/percolation of the solid network, effective solid conductivity and ionic diffusivity, interfacial area, cell capacity, lithium plating, impedance, and transport polarization at the beginning of life (BOL) [1]. Rate capability test demonstrates capacity improvement at fast charge at BOL (cf. figure, right), from 37% to 55%, respectively for high (10%wt) and low (4%wt) additive loading during 6C CC charging (and from 80% to 86% at the end of 10 min 6 CC-CV), in agreement with macroscale model. Improvements are attributed to a combination of lower cathode impedance, reduced electrode tortuosity and cathode thickness [1].

[1] F. Usseglio-Viretta et. al., Carbon-binder Weight Loading Optimization for Improved Lithium-ion Battery Rate Capability, submitted to Journal of the Electrochemical Society

[2] F. Usseglio-Viretta et. al., SoftwareX, 17, 100915 (2022), https://doi.org/10.1016/j.softx.2021.100915

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(Invited) Fire-Extinguishing, Recyclable Liquefied Gas Electrolytes for Temperature-Resilience Lithium Metal Batteries
Authors: Yin Yijie , Yang Yangyuchen , Holoubek John , Cheng Diyi , Chen Zheng , Borodin Oleg , Meng Ying Shirley
Published: November 2022

High energy density, improved safety, temperature resilience and sustainability are desirable properties for lithium battery electrolytes, yet these metrics are rarely achieved simultaneously. Inspired by the compositions of clean fire extinguishing agents, we demonstrate inherently safe liquefied gas electrolytes (LGE) based on 1,1,1,2-tetrafluoroethane (TFE) and pentafluoroethane (PFE) that maintain > 3 mS cm-1 ionic conductivity from –78 to +80 °C. As a result of beneficial solvation chemistry and a fluorine-rich environment, Li cycling at > 99% Coulombic efficiency for over 200 cycles at 3 mA cm-2 and 3 mAh cm-2 was demonstrated in addition to stable cycling of Li/NMC622 full batteries from –60 to +55 °C. Additionally, we demonstrate that the vapor pressure-temperature relationship unique to LGE systems allows for a one-step solvent recycling process, which promises sustainable operation at scale. This work provides a route to sustainable, temperature resilient lithium metal batteries with fire-extinguishing properties that maintain state-of-the-art electrochemical performance.
Understanding the Unreliability Issues of Performance and Safety Diagnostics of Lithium-Ion Batteries Under Extreme Conditions
Authors: Tanim Tanvir R. , Walker Lee K , Todd Jordan
Published: November 2022

The research and development (R&D) community is continually pushing for high energy density Lithium-ion batteries (LiBs) by innovating materials, designs, and operating conditions.1 We expect these batteries to operate under a range of conditions (e.g., fast charging, fast discharging, low temperatures, etc.).1,2 Advanced diagnostics could play a key role in ensuring an extended life of these energy-dense LiBs while ensuring their safety. Therefore, a parallel effort is enabling advanced diagnostics and prognostics to ensure the safe operation of these batteries under the stated conditions throughout their service lives.

Many researchers have proposed different performance and safety diagnostics of LiB in their early stages, often using small or specially designed cells through controlled tests.1 Extending these diagnostics to automotive grade cells in real life environments has not been performed extensively to understand their uncertainties. This gap in development between the early R&D stage to near the deployment stage is impeding their maturity; hence, delaying their adoption in their expected applications.

In this presentation, we will discuss the unreliability issues of different electrochemical and electromechanical diagnostics related to LiBs under different safety critical conditions when cell size, age, and operating conditions changes. We will discuss the underlying issues of unreliability in different diagnostics with experimental data, followed by a discussion of several emerging safety diagnostics. Finally, the need for independent evaluation of LiB safety diagnostics along with some logistical pathways to do so will be discussed.

References

T.R. Tanim, E. J. Dufek, and S. V. Sazhin, MRS Bulletin, 46, 420-428 (2021)

S. Ahmed et al., J. Power Sources, 367, 250–262 (2017).
(Digital Presentation) Elucidating the Rate-Limiting Processes in High-Temperature Sodium-Metal Chloride Batteries
Authors: Landmann Daniel , Svaluto-Ferro Enea , Heinz Meike , Schmutz Patrik , Battaglia Corsin
Published: November 2022

Sodium-metal chloride batteries are considered a sustainable and safe alternative to lithium-ion batteries for large-scale stationary electricity storage, but exhibit disadvantages in rate capability. Several studies identified metal-ion migration through the metal chloride conversion layer on the positive electrode as the rate-limiting step, limiting charge and discharge rates in sodium-metal chloride batteries. Here we present electrochemical nickel and iron chlorination with planar model electrodes in molten sodium tetrachloroaluminate electrolyte at 300 °C. We discovered that, instead of metal-ion migration through the metal chloride conversion layer, it is metal-ion diffusion in sodium tetrachloraluminate. which limits chlorination of both the nickel and iron electrodes. Upon charge, chlorination of the nickel electrode proceeds via uniform oxidation of nickel and the formation of NiCl2 platelets on the surface of the electrode. In contrast, the oxidation of the iron electrodes proceeds via localized intergranular dissolution, resulting in non-uniform iron oxidation and pulverization of the iron electrode. We further discuss the transition from planar model electrodes to porous high-capacity electrodes, where sodium-ion migration along the tortuous path in the porous electrode can become rate limiting. These mechanistic insights are important for the design of competitive next-generation sodium-metal chloride batteries with improved rate performance.
(Invited) Extending the Low Temperature Operating Range of Sodium Metal Batteries
Authors: Li Weiyang
Published: November 2022

Despite the promise of sodium electrochemistry at ambient temperature, the performance of sodium metal batteries in frigid environments is hindered by high internal resistance and unstable solid electrolyte interphase (SEI), which highly depends on the electrolyte composition. Here we present our recent efforts in tuning the electrolyte composition, which enables the formation of a protective SEI on sodium metal electrode in cold environments. Long-term sodium metal cycling is demonstrated at low temperatures down to −80°C. Coupled experimental characterization (such as, X-ray photoelectron spectroscopy, cryogenic transmission electron microscopy, and atomic force microscopy) and density functional theory calculations reveal the underlying mechanism behind the superior performance.
Correlating Local Structure and Electrochemical Performance in Metal-Substituted Vanadium Ferrite Aerogel Electrodes for Lithium-Ion Batteries
Authors: DeBlock Ryan H. , Chervin Christopher N. , Rolison Debra R. , Johannes Michelle D. , Long Jeffrey W.
Published: November 2022

Disordered vanadium ferrite (VFe2Ox) materials exhibit promising performance for electrochemical energy-storage applications such as rechargeable lithium-ion batteries.1,2 We employ an epoxide-promoted sol–gel reaction of iron chloride and vanadium isopropoxide to form nanostructured vanadium ferrite gels. Subsequent supercritical-CO2 extraction of the pore fluid yields high surface–area aerogels. Heat treatment under either O2-containing or inert atmosphere yields disordered or nanocrystalline variants, respectively. Electroinactive metal cations such as aluminum, zinc, and zirconium are substituted during the initial sol–gel synthesis to alter the local electronic environment of VFe2Ox. The resulting series of native and substituted VFe2Ox materials are evaluated as powder-composite cathodes versus lithium metal in coin cells with conventional nonaqueous lithium-ion electrolyte. We correlate such critical battery-performance parameters as total specific capacity, high-rate capability, and cycle life as a function of MVFe2Ox composition and its degree of structural order/disorder. In-lab X-ray absorption spectroscopy also provides important information on metal oxidation state and element-specific coordination for these VFe2Ox aerogels, including during operando electrochemical lithiation/delithiation. In parallel with experimental advancements, calculations on VFe2Ox reveal that V incorporation into the defect-induced spinel structure occurs at tetrahedral sites. Further, both disorder of vacancies and Fe/V tetrahedral occupation lower the overall energy, opening an electronic energy gap that establishes the redox sequence during lithiation.

N. Chervin, J. S. Ko, B. W. Miller, L. Dudek, A. N. Mansour, M. D. Donakowski, T. Brintlinger, P. Gogotsi, S. Chattopadhyay, T. Shibata, J. F. Parker, B. P. Hahn, D. R. Rolison, and J. W. Long, J. Mater. Chem. A
3, 12059 (2015).

C. N. Chervin, R.H. DeBlock, J. F. Parker, B. M. Hudak, N. L. Skeele, J. S. Ko, D. R. Rolison, and J. W. Long, RSC Adv.
11, 14495 (2021).
(Invited) Discovery of New Capacity Fade Mechanism in Lixsn Batteries with Derivativeoperando (dOp) NMR Spectroscopy
Authors: Grandinetti Philip John , Lorie Lopez Jose , Co Anne C.
Published: November 2022

Tin, silicon and other intermetallic forming electrodes have large volumetric lithium capacities—nearly 10 times that of graphite. Such a high capacity combined with their low cost make intermetallics promising materials for the next generation of rechargeable batteries. Unfortunately, severe capacity fade remains the greatest obstacle in their commercial use. For example, in 2005 Sony introduced their NEXELION battery technology using nanostructured SnCo electrodes but eventually had to pull these batteries from the market due to substantial capacity loss with cycling. While a major reason for capacity fade in these electrodes is thought to be cracking from large volume changes during transitions between intermetallic phases, little evidence for cracking in nanostructured electrodes has been found; and the mechanism for capacity fade in nanostructured intermetallic electrodes has remained a mystery.

Using derivative operando (dOp) 7Li NMR we have discovered a mechanism for capacity fade in LixSn nanoparticle electrodes that may solve this mystery. In short, the capacity fade in nanoparticle electrodes is the result of nanoparticles losing contact with the carbon/PVDF binder. Yet, it occurs in a peculiar way which causes the cell to reach full capacity at the end of every cycle on lithiation. In other words, capacity fade only occurs during delithiation. We present clear NMR evidence showing that particle disconnection occurs during the delithiation (volume contraction of the electrode particles) process. During lithiation (volume expansion of the electrode particles) our NMR data further reveals that connected particles are surprisingly pushed back into contact with the disconnected particles which then rejoin the circuit and allow the cell to reach full capacity on lithiation. Our dOp 7Li NMR spectra also reveal the structural transformation pathways between Li-Sn intermetallics during lithiation and delithiation of Sn nanoparticles. The disconnecting particles are associated with LixSn phases undergoing large decreases in diameters on delithiation, i.e., Sn, Li2Sn5, LiSn, and Li7Sn3. The Li–Sn phases observed are somewhat consistent with the structural evolution expected from the equilibrium binary phase diagram, but there are some notable exceptions with the observation of a metastable phase Li2Sn3, and two vacancy rich metastable phases, Li7−ζSn3, and Li13−δSn5 during delithiation.

Although this new capacity fade mechanism is simple, we know no in-situ microscopy method capable of detecting and following such a disconnection-connection mechanism. Our approach clearly show the power of operando NMR spectroscopy for revealing such fundamental processes. These results point the way for future efforts in both industrial and academic research labs to reduce capacity fade in a wider range of nano-structured intermetallic electrodes, involving Si, Ge and Sb.

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(Invited) Insights of Electrochemical Degradation Enabled By Correlated in-Situ Electrochemical Diagnostics and Spatially Resolved Diffraction Mapping
Authors: Cheng Lei , Rezaei Talarposhti Morteza , Khedekar Kaustubh , Braaton Jonathan , Zenyuk Iryna V. , Craig Nathan , Johnston Christina
Published: November 2022

One of the top priorities of human society is addressing climate change. Clean electrochemical technology is a vital part of the transformation necessary to meet climate goals and net-zero CO2 emissions by 2050. Electrochemical technology of high interest includes water electrolysis for green hydrogen generation, fuel cells for emission free transportation, and electrochemical CO2 reduction for achieving net-zero CO2 emissions. One critical challenge for wide-scale adoption of these electrochemical technologies is the long-term device durability. Comprehensive understanding the degradation phenomenon and underlying mechanism is of critical importance for technology and product development. In this regard, in-operando and in-situ techniques, providing unique and direct insight into the degradation process in these electrochemical devices, play important roles for advancing such understanding and ultimately increasing long-term durability.

Such techniques often rely on combined electrochemical diagnostics with advanced spectroscopy or other imaging capable of temporal and spatial resolution. In-operando techniques are often challenging due to the need for unique electrochemical cell configurations that fulfill the requirements of the technique while at the same time delivering electrochemical behavior similar to a commercial device.

The talk will first discuss a mapping methodology based on synchrotron X-ray micro-diffraction to study the heterogeneous degradation. Information obtained from the method and examples of application to study platinum catalyst degradation in accelerated stress tests will be discussed. The utility of correlating large datasets of in-situ electrochemical diagnostics from a variety of accelerated aging tests with the spatially resolved diffraction mapping will also be presented.
In-Situ/Operando Bragg Coherent X-Ray Diffraction Imaging for Nanoscale Imaging of Strain and Defect
Authors: Cha Wonsuk
Published: November 2022

In the last two decades, Bragg Coherent X-ray Diffraction Imaging (BCDI) has become a powerful nanoscale characterization technique [1]. Its extreme sensitivity to lattice displacements enables to image three-dimensional morphology as well as internal deformation field distribution of nano- or micro-scaled various materials. In-situ and operando capabilities have been combined to BCDI to address scientific questions on materials under realistic conditions. Nowadays, in-situ/operando BCDI on electrochemistry successfully shows strain evolution and dislocation dynamics inside materials.

In this talk, I will introduce current state-of-the-art of BCDI and the 34-ID-C beamline in the Advanced Photon Source which is dedicated to BCDI. This talk will also cover recent experimental results on in-situ/operando BCDI, for example, electrochemical dissolution/deposition [2] and battery materials during charging/discharging cycles [3,4].

[1] M. A. Pfeifer, et al., Nature 442, 63 (2006).

[2] Y. Liu, et al., Nano Lett. 17, 1595 (2017).

[3] A. Ulvestad, et al., Science 348, 1344 (2015).

[4] A. Singer, et al., Nat. Energy 3, 641 (2018).
Novel Metal-Free Composite Electrodes with Carbon Quantum Dots and Anion-Conducting Ionomers for the Oxygen Reduction Reaction
Authors: Reddy Nallayagari Ashwini
Published: November 2022

The oxygen reduction reaction (ORR) is one of the bottlenecks in many electrochemical applications and plays an important role in commercial fuel cell systems. Platinum is highly used as a catalyzer especially in proton exchange membrane fuel cells. Given its rarity and cost, platinum, is not a viable choice as a catalyst, so there is a need to shift to alternative materials such as a metal-free catalyst possible in anion exchange membrane fuel cells. There were several theoretical and experimental studies to address this issue and a direction toward metal-free catalysts is of great interest. In this study, we focus on the oxygen reduction reaction in alkaline medium using a novel metal-free catalyst composite with carbon quantum dots and anion exchange ionomer (AEI). Doped carbon quantum dots were synthesized by a hydrothermal method and an AEI was integrated to improve the hydroxide ion transport and have a composite of desired functionality. These composites showed significant electrochemical activity with a good current response and four-electron ORR. The characterization comprised various microscopic, spectroscopic and electrochemical techniques.

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Field-Effect Tuning of Electrochemistry at 2D Semiconductor Electrodes: Charge Transfer Kinetics Can be Modulated with a Back Gate Voltage
Authors: Wang Yuxin , Frisbie C.Daniel
Published: November 2022

Semiconductor electrodes are widely used in electrocatalytic reactions. The ability to improve and modulate the heterogeneous charge transfer kinetics on semiconducting electrodes is a major challenge for the electrochemical application of these materials. Instead of changing the electronic occupation of the semiconductor by chemical doping, we adopt an electronic method to modulate band edge alignment and solution electrochemistry at 2D ZnO working electrodes.

In our approach, a field-effect transistor with ultrathin ZnO semiconductor (3-5 nm) is fabricated, the heart of which is a metal-insulator-semiconductor (MIS) stack. A high-dielectric-constant material (HfO2) is used as the insulator to realize low-voltage tunability of the device. The ZnO layer of the device functions as the working electrode (WE) for electrochemical reactions. By applying a back gate voltage to this MIS field-effect transistor, charge carriers are electrostatically induced and the ZnO band edges shift at the front face of the ZnO in contact with electrolyte. These effects can be exploited to manipulate the charge transfer kinetics on the ZnO electrode at a given electrode potential. We demonstrate this by focusing on outer-sphere redox chemistry. In order to eliminate mass transfer effects, microfluidic flow cells are coupled to the ZnO devices. Steady state kinetic analysis is carried out to extract the electron transfer rate constant of the redox process as a function of both electrochemical and back gate potentials. The heterogeneous electron transfer rate can be tuned by over an order of magnitude using the back gate voltage. The work demonstrates that a back gate provides another degree of freedom in determining electrochemical reaction kinetics at ultrathin semiconductor working electrodes. The method also opens possibilities for control over a wider range of semiconductor electrochemistry, such as electrocatalytic reactions.

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(Invited) NMR Investigation of Proton Transport in Concentrated Aqueous and Polymer Electrolytes Based on Polyphosphoric Acid
Authors: Garaga Mounesha N , Greenbaum Steven
Published: November 2022

Concentrated aqueous electrolytes have received much attention in recent years due to their high ionic conductivity and electrochemical window that usually exceeds that of the water electrolysis limitation. In collaboration with Ziyue Li and Fei Wang (Fudan University) we have investigated water/polyphosphoric acid solutions ranging in concentration from 1.25 to 16.6 molar being considered for proton-based batteries. Self-diffusion coefficients measured by pulsed field gradient NMR as well as spin-lattice time relaxation measurements were determined for 31P and 1H. The results shed light on the observed maximum in conductivity at the 5.9 molar concentration.

For polymer electrolyte membrane fuel cells (PEMFC), polybenzimidazole (PBI) membranes with high phosphoric acid content have been developed previously by collaborator Brian Benicewicz (University of South Carolina) using the so-called PPA process. Recently, a carefully controlled drying method has been discovered by Benicewicz and co-worker Laura Murdock in which a PBI membrane prepared by the PPA process is transformed into a dense PBI film. Though originally developed for flow battery applications, it was found that this dense film could be re-acidified to yield a mechanically robust PEM. Furthermore this method provides a synthetic route to PBI films without the use of any organic solvents. The re-doped PBI films display high ionic conductivity at elevated temperatures, similar to the starting PBI gel membranes prepared by the PPA process, while containing nearly a factor of two less acid than the latter and also exhibiting enhanced mechanical properties. NMR spectroscopy was used to characterize the structure and dynamics of the modified and the original PBI/PPA membranes. In addition to pulsed field gradient diffusion studies, we have performed solid state one-dimensional 31P, 13C and two-dimensional 31P{1H} and 13C{1H} HETCOR NMR measurements, which yield additional information on structural differences between the membranes and how these differences may affect transport properties.
(Invited, Digital Presentation) Charge Transfer at Heterogeneous Functional Interfaces in Energy Conversion and Storage Devices: A Quantum Chemical Perspective
Authors: Munoz Garcia Ana Belen
Published: November 2022

Energy conversion and storage devices are triggering the ecological transition toward a sustainable economic and social development. In these technological devices, several constituent materials and their interfaces undergo charge/mass transport processes over different time/space scales, from local fast electron transfer to long-range slow ionic diffusion.

Often, experimental techniques cannot dissect such processes at the nanoscale, which hinders a rational design of new devices with better performances. Thus, the application of computational modeling tools with atomistic resolution represents an ongoing revolution in materials design and device development.

In this context, this contribution will display how cutting edge DFT-based approaches allow to unveil the charge transfer mechanisms in several different electrochemical environments: (i) at hybrid interfaces considering promising Cu-based molecular redox couples in dye sensitized solar cell photoanodes [1,2], (ii) at heterogeneous interface in last generation perovskite solar cells [3] and (iii) ion-electrode interfaces in the context of nanostructured electrodes in sodium-ion batteries [4,5,6].

The results will provide new insights on the structure-property-functional relationships of different functional materials/interfaces and will pave the basis of new design principles for further improvements of the corresponding devices.

[1] AB Muñoz-García, I Benesperi , G. Boschloo, JJ Concepcion, JH Delcamp, EA Gibson, GJ Meyer, M Pavone, H Pettersson, A Hagfeldt, M Freitag

Dy
e-sensitized Solar Cells strike back

2021 Chemical Society Reviews 50, 12450-12550

[2] I Benesperi, H Michaels, T Edvinsson, M Pavone, MR Probert, P Waddel, AB Muñoz-García*, M Freitag

Dynamic dimer copper coordination redox shuttles

2022 Chem 8, 439-449 (Cover Article)

[3] A Pecoraro, A De Maria, P Delli Veneri, M Pavone, AB Muñoz-García*

Interfacial electronic features in methyl-ammonium lead iodide and p-type oxide heterostructures: new insights for inverted perovskite solar cells

2020 Physical Chemistry Chemical Physics 22, 28401-28413

[4] A Massaro, AB Muñoz-García, PP Prosini, C Gerbaldi, M Pavone

Unveiling Oxygen Redox Activity in P2-Type NaxNi0.25Mn0.68O2 High-Energy Cathode for Na-Ion Batteries

2021 ACS Energy Letters 6, 2470-2480

[5] A Massaro, A. Langella, AB Muñoz-García, M Pavone

First-principles insights on anion redox activity in NaxFe1/8Ni1/8Mn3/4O2: Towards efficient high-energy cathodes for Na-ion batteries

2022 Journal of American Ceramic Society https://doi.org/10.1111/jace.18494

[6] A Massaro, AB Muñoz-García, P Maddalena, F Bella, G Meligrana, C Gerbaldi, M Pavone

First-principles study of Na insertion at TiO2 anatase surfaces: new hints for Na-ion battery design

2020 Nanoscale Advances 2, 2745-2751
Making and Breaking Bipolar Membrane Protonic Diodes
Authors: Schulte Leanna , Phun Gabriel S. , Heffernan Ethan J. , White William , Renna Lawrence A. , Ardo Shane
Published: November 2022

Historically, bipolar membranes have been used for application in electrodialysis at moderate current densities (<100 mA/cm2). In the past decade bipolar membranes have experienced a renaissance due to interest in driving higher current density processes with intentional pH gradients between the anode and cathode, such as CO2/H2O electrolysis and electrochemical generation of acid and base for direct oceanic carbon capture, two applications that my group actively studies. My group’s main contribution to this field is that we recently showed that bipolar membranes are in fact high-quality protonic diodes, where water serves as a (protonic) semiconductor. Given this fact, we leveraged techniques from the semiconductor physics and electrocatalysis communities, i.e. Mott–Schottky analysis and Butler–Volmer analysis, to further characterize bipolar membrane performance. Using this platform, we have also demonstrated photovoltaic action from photoacid-dye-sensitized bipolar membranes. More recently, we have studied how intentional placement of proton-donating and proton-accepting groups in the bipolar membrane space–charge region forms a recombination/generation junction, which are the non-tunneling variants of tunnel junctions that are important in tandem solar cells. This allows for rapid protonic conduction across originally rather insulating junctions, as desired for ionic conductors in most electrochemical devices. Collectively, our efforts form the foundational framework for new functions and resulting applications that benefit from protonic transfer and transport.
(Invited) Electro-Conversion of CO2 – a Technical and Economical Comparison between High Temperature and Low Temperature Processes
Authors: Wang Yudong , Zhou Xiao-Dong
Published: November 2022

The booming technologies for the electrochemical conversion of CO2 aim to offer a carbon-neutral approach for industrial activities. The major greenhouse gas, CO2, can be reduced electrochemically with a low-carbon energy source in a highly effective manner. In this talk, we will provide a thorough technical and economical comparison between high temperature and low temperature processes. The thermodynamics of CO2 splitting, which is highly temperature-dependent, determines the energy requirement for the technologies. The development of polymer electrolyte membranes enables the low temperature electrochemical CO2 reduction in an aqueous system into various high-value products. High-temperature CO2 electrolysis based on solid oxide cells or molten carbonate cells reduces electricity cost and can be highly effective for CO production. Techno-economic assessment of these electrolysis techniques offers a comprehensive understanding on balancing efficiencies, economic cost and environmental benefits. The milestones on the materials/system development are proposed for high efficiency, low cost, high-value products and less negative environmental effects to move CO2 electrolysis technologies toward commercialization.
Thermally-Activated Cobalt Hexacyanocobaltate Dispersed on Reduced-Graphene-Oxide As Electrocatalyst Towards Oxygen Reduction in an Alkaline Medium
Authors: Miecznikowski Krzysztof , Zakrzewska Barbara , Adamczyk Lidia , Kulesza Pawel J. , Marcinek Marek , Cox James A.
Published: November 2022

In the recent research years is observed huge interest in design of new functional nanomaterials for developing new electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline media. The research has been focused on developing carbon nanostructures materials with the different transition metals (e.g. Co, Ni, Ag, Au, Cu, Mn) analogue of polynuclear Prussian Blue for fuel cell applications. The development of electrocatalytic material prepared by heat-treating a composite of a Prussian Blue analogue - cobalt hexacyanocobaltate immobilized on a reduced graphene oxide. The pyrolysis process, forms a new type of catalyst with efficient active cobalt centers (Co-N-C and Co-C-N) of electrochemical oxygen reduction reaction in alkaline media. Physicochemical properties of this catalytic material containing cobalt in differing oxidation states were elucidated using microscopic, spectroscopic methods and various electrochemical diagnostic techniques. Experimental results showed that the cobalt analogue of Prussian Blue displayed comparable electrocatalytic activity (e.g., a half-wave potential and overpotential) towards oxygen reduction reaction in alkaline media to Vulcan-supported platinum nanoparticles. Furthermore, the presence of cyanide-bridged cobalt ionic sites tended to decrease formation of undesirable peroxide intermediate species, as demonstrated by monitoring ring currents during RRDE measurements. Furthermore, the proposed electrocatalytic material exhibits great stability and tolerance to alcohols (e.g. methanol).

Acknowledgement

The study was supported by the National Science Center (NCN), Poland, Project Number 2015/19/B/ST4/03758