bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Electrocatalytic Reduction of Carbon Dioxide over Aluminum-Added Coppor Oxide Gas Diffusion Electrode
Authors: Minegishi Tsutomu , Komori Daiki , Ebe Hiroji , Kumagai Hiromu , Sugiyama Masakazu
Published: February 2024

Electrochemical cells are the key technologies for construction of carbon neutral society to produce hydrogen from water and produce useful chemicals from carbon dioxide utilizing renewable energy. Copper species are the unique catalysts for electrochemical carbon dioxide reduction reaction (CO2RR) with capable of producing C2+ products such as ethanol and ethylene. Selective production of target chemical is one of the most important requirements for the catalysts, and addition of different elements and surface modifications have been reported to be beneficial for the selective production.

In the present study, copper oxides-based catalysts prepared with electroless plating techniques were examined for electrochemical CO2RR. To conduct CO2RR at relatively high current densities, the catalysts were examined in the form of gas diffusion electrode (GDE). The Cu2O based GDE was prepared by the combination of physical vapor deposition and electroless plating on hydrophobized carbon paper coated with mesoporous carbon layer. After the electroless plating treatment, the metal precursors were successfully converted to core-shell structured electrocatalyst with Cu2O shell and Cu core. By introducing different elements such as aluminum to the precursor, metallic Cu, the different element added catalysts were successfully prepared in the shape of GDE. Addition of different element significantly improved durability of the core-shell structured catalysts and, as a result, faradaic efficiency of ethylene of 24 hours after starting electrolysis was increase from 32% to 47% under applying cathodic current of 260 mAcm-2. Further surface modifications with Nafion enhanced the durability and the faradaic efficiency of ethylene maintained >50% for over 48 hours and reached about 60% in maximum.

In the presentation, we will discuss about the detailed structure of the electrocatalysts, results of full-cell test, and longer durability test over 100 hours.
(Invited) Limitation of Molecular Twisting: Upgrading a Donor-Acceptor Dye to Drive H2 Evolution
Authors: Mul Guido , Zhu Kaijian , Huijser Annemarie
Published: February 2024

Dye-sensitized photoelectrochemical cells (DSPECs) have attracted wide attention to convert solar energy into high-energy chemicals. A DSPEC consists of a photoanode performing the oxidation half reaction and a

photocathode performing the reduction half reaction. In this presentation I will demonstrate how the performance of a dye-sensitized photocathode can be manipulated to enhance performance and even produce hydrogen! We have used a state- of-the-art dye (D-A P1 dye) on the surface of optimized NiO, and co-adsorbed myristic acid (Tetradecanoic Acid), which has a carboxyl anchoring group and a long apolar alkyl chain. Time-resolved photoluminescence and Density Functional Theory studies show that twisting lowers the energy levels of the photoexcited D-A dye, while twisting is inhibited in case myristic acid is co-adsorbed on the NiO surface. The presence of myristic acid also favors light-induced charge separation, as apparent from femtosecond transient absorption, and increases the apparent photocurrent. Very interestingly, only in the presence of myristic acid, light-induced H2 evolution is observed in aqueous media, despite the absence of a H2 evolution catalyst. We assign the H2 generation to a synergetic effect of inhibited twisting of the D-A dye radical anion increasing its electrochemical potential, combined with charge transfer and conversion of H+ on the hydroxylated NiO surface. Our work illustrates the importance of understanding effects of photoinduced intramolecular twisting and demonstrates that control thereof offers a simple design approach for efficient solar fuel devices.
Extending the Success of Halide Perovskites from Solar Cells to Photoelectrodes and Photocatalysts
Authors: Eslava Salvador , Daboczi Matyas , Baghdadi Yasmine , Temerov Filipp , Sena Michael , Cui Junyi
Published: February 2024

Photoelectrochemical and photocatalytic conversion of water and carbon dioxide using solar energy offers a clean and sustainable solution to meet the world’s energy requirements. Achieving their full potential depends on developing inexpensive photoelectrodes and photocatalysts that can efficiently absorb solar light and drive photoinduced charges to react with water and carbon dioxide. In this talk, I will present the recent developments of our group in the preparation of inexpensive photoanodes and photocatalysts made of halide perovskites such as CsPbBr3. These materials are revolutionizing the photovoltaics field due to their high absorption coefficient and excellent optoelectronic properties, and now offer an opportunity to revolutionize photoelectrochemistry and photocatalysis if their instability in aqueous environments is addressed. We have found novel strategies to protect halide perovskites with printed carbon layers and graphite sheets functionalized with NiFeOOH water-oxidation electrocatalyst, achieving photoanodes with low onset potential (+0.4 VRHE) for solar water oxidation. We have also managed to boost charge separation in these photoanodes by engineering the CsPbBr3 phase to a 3D one that achieves enhanced energetics and better band alignment to the TiO2 electron transport layer and printed carbon electrode layer, achieving photocurrents around 8 mA cm-2 at 1.23 VRHE for water oxidation. Moreover, our carbon/graphite protection and NiFeOOH functionalization methods impart days of stability to the photoanodes, easily extended to weeks, compared with seconds in the absence of protection. Regarding photocatalysts made of halide perovskite, we have found novel approaches based on mechanochemical syntheses and antisolvent crystallization to prepare different composites of CsPbBr3 and other perovskites, including Cs2AgBiBr3/bismuthene and Cs3Bi2Br9/g-C3N4, all photocatalytically active in the reduction of CO2. An extended characterization allows us to relate their physical and charge-transfer properties to their performance, providing guidance in their rational design for their optimization and future application.
(Invited) C–C Bond Cleavage of Lignin with an Organic Dye-Sensitized Photoanode
Authors: Kim Saerona , Kang Hyeong Cheol , Leem Gyu , Lee Jae-Joon
Published: February 2024

Chemoselective C–C bond cleavage remains a challenge for the degradation of polymers because of the relatively high bond dissociation energy of C–C σ-bonds at room temperature. Organic molecular-based dye-sensitized photoelectrochemical cells (DSPECs) could offer a means of using renewable solar energy to drive energetically demanding chemoselective C–C bond cleavage reaction. This study reports the solar light-driven activation of a bicyclic aminoxyl mediator to achieve C–C bond cleavage in the aryl-ether linkage of a lignin model compound (LMC) at room temperature using a donor–π-conjugated bridge–acceptor (D–π–A) organic dye-based DSPEC system. The 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DPTC) D–π–A organic dye was investigated along with a bicyclic aminoxyl radical mediator (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, KABNO) in solution and at the interface of a mesoporous structured TiO2 substrate in the presence of LMC. Photophysical studies of DPTC with KABNO were carried out to show intermolecular energy/electron transfer under 1 sun illumination (100 mW·cm−
2). The D–π–A type DPTC sensitized mesoporous TiO2 photoanode in the presence of KABNO can facilitate the generation of the reactive oxoammonium species KABNO+
as a strong oxidizing agent, which plays an important role in the photocatalytic oxidative C–C bond cleavage of LMC. The photoelectrochemical oxidative reaction in a complete DSPEC with KABNO afforded the chemoselective C–C bond cleavage products 2-(2-methoxyphenoxy)acrylaldehyde (94%) and 2,6-dimethoxy-1,4-benzoquinone (66%). This process provides a first report utilizing a D–π–A type organic dye in combination with a bicyclic nitroxyl radical mediator for heterogeneous photoelectrolytic oxidative cleavage of C–C σ-bonds, modeled on those found in lignin, at room temperature.
Viable Route to Green Hydrogen: Sea Water Photocatalysis
Authors: Khushalani Deepa
Published: February 2024

The photocatalytic (PC) hydrogen production from water splitting is a promising route to fulfill the current energy demand in an eco-friendly and sustainable manner. For photocatalysis to become industrially viable, seawater should be used. This solvent owes its salinity due to various ions (Na+, K+, Mg2+, Ca2+, Cl−, Br−, SO2
4−, and CO3
2−). To date, there are contradicting reports in the literature on the influence of these ions on the PC splitting of water. A variety of different neutral transition metal-oxide-based photocatalysts have been exploited. Although they might be effective in splitting deionized water, however, thus far, there has been a lack of a well-established route to effectively using any semi-conductor for seawater splitting. Presented here are the details of our work where an intriguing, ionized, low-cost semiconductor has been successfully evaluated for sea-water splitting. The structure consists of a modified carbon nitride such that it forms an ionized organic polymer-based system. A detailed study has been done using this salt-type semiconductor in the presence of various ions, and their role has been probed in modulating the photocatalytic activity. Photoelectrochemical measurements have provided insight as to how the presence of cations aids advantageously in forming an effective in-situ interface between catalyst/co-catalyst for improved charge transfer. This improved interfacial charge transfer rationalizes the 8-fold enhancement in the photocatalytic rate in the presence of simulated seawater compared to deionized water. It provides an impetus for using these carbon nitride structures for sustainable PC splitting of seawater.
(Invited) Solar-Driven H2O2 Production via Cooperative Auto- and Photocatalytic Oxidation in Fine-Tuned Reaction Media
Authors: Lee Dong Ki , Byun Jeehye , Moon Byeong Cheul
Published: February 2024

The industrial synthesis of H2O2 is based on the anthraquinone auto-oxidation process, which requires high-energy consumption and an expensive metal catalyst. Solar photocatalysis has been suggested as a green and sustainable process to produce H2O2. Although there have been significant advances in material design to improve the H2O2 production efficiency, the photocatalytic H2O2 production performance remains insufficient to meet industrial demands. In this study, we designed a new reaction environment using aryl alcohol as an organic photo-oxidation substrate. With a metal-free covalent triazine framework (CTF) as a model photocatalyst, we combined photo-oxidation with O2 reduction in fully organic conditions for the co-production of H2O2 and aryl aldehyde. Furthermore, such an organic system allows for the light-activated autocatalytic oxidation of aryl alcohol, facilitating O2 reduction kinetics by photo-initiated radicals. Inspired by an organic working solution of the anthraquinone process, we fine-tuned the reaction composition by varying the water-aryl alcohol-solvent ratios to improve the photocatalytic pathway, achieving one of the highest solar-to-chemical conversion efficiencies ever reported. The electrochemical assessment of the photocatalyst elucidates that the effect of water addition in the organic solution promotes the proton transfer from aryl alcohol to dissolved O2 molecules, boosting the H2O2 generation. This study demonstrates that tailoring the reaction media is a simple but effective route for promoting overall solar H2O2 productivity, providing a new opportunity in photocatalytic reactions.
Surface Hydroxyl Groups Enhance Ethylene Selectivity in Acidic CO2 Reduction Reaction
Authors: Chen Zhu , Cao Yufei , Sinton David , Ge Jun , Sargent Edward H.
Published: February 2024

Acidic conditions can enable high single-pass conversion in electrochemical CO2 reduction (CO2R) reaction. However, the kinetically facile hydrogen evolution reaction (HER) prevails in acidic conditions and limits the energy efficiency for CO2R towards multi-carbon (C2+) products. By performing electrodeposition under CO2R conditions, we synthesized a copper catalyst (EC-Cu) that promotes selective CO2R to C2+ products in acidic conditions. We combine in situ spectroscopy, DFT calculations, and catalyst performance to show that co-adsorbed CO and OH on the catalyst surface promote C-C coupling, which we correlate with evidence of increased CO residence time. With optimization, the EC-Cu catalyst achieved a 60% faradaic efficiency for ethylene and 90% for C2+. Furthermore, when implemented in a slim flow cell, the EC-Cu catalyst can attain a 20% energy efficiency toward ethylene production.
Hydrodynamics Change Tafel Slopes in Electrochemical CO2 Reduction on Copper
Authors: Watkins Nicholas B. , Schiffer Zachary J. , Lai Yungchieh , Musgrave Charles B. , Atwater Harry A. , Goddard William A , Agapie Theodor , Peters Jonas C. , Gregoire John M.
Published: February 2024

The hydrodynamics of electrochemical CO2 reduction (CO2R) systems is an insufficiently investigated area of research that has broad implications on catalyst activity and selectivity. While most previous reports are limited to laminar and CO2-sparged systems, herein we address a wide range of hydrodynamics via electrolyte recirculation systems. We find that increased hydrodynamics at the electrode surface results directly in changes to the ethylene and methane Tafel slopes, demonstrating that mass transport is on equal footing with catalyst active sites in determining reaction mechanisms and the ensuing product distribution. Mass transport is traditionally considered to be in the purview of systems-level engineering, yet the present work shows that CO2R mechanistic work must be considered in the context of the mass transport conditions. We extend our analysis to organic coatings, demonstrating that the films shield the active sites from variability in hydrodynamics and increase the residence time of CO so that it may be further reduced to desirable products.
Mass Transport in a Gas-Fed CO2 Electrolyzer with a Forward-Bias Bipolar Membrane
Authors: Dessiex Matthieu , Fischer Robert , Haussener Sophia , Buechi Felix N.
Published: February 2024

In the context of synthetic fuel and chemical production, CO2 electrolyzers using bipolar membranes (BPM) in forward bias have proven to overcome current limitations in state-of-the-art alkaline CO2 electrolyzers. These limitations are CO2 cross-over and carbonate deposition in the cathode catalyst layer, which limit the large-scale development of alkaline CO2 electrolyzers. Devices with a BPM in forward bias (Figure 1) solve these issues by setting the anode under acidic conditions while keeping the cathode alkaline. This configuration prevents carbonate ions to reach the anode and thus suppresses CO2 cross-over. Moreover, it allows pure water as an anolyte. Pure water eradicates unwanted cation cross-over and thus prevents carbonate deposition at the cathode. However, the use of a BPM for CO2 also has limitations. The most prominent ones are low stability and high over-voltage. These are partly caused by the complex and unexplored water transport.

This work presents efforts to characterize and optimize different water transport phenomena. For this, we study cells of different complexity. It implies understanding first the water diffusion across the membrane, by setting a water concentration gradient between the electrodes and analyzing water transport by dew point measurement. The membrane hydration state can be determined with the simultaneously measured ion conductivity. Then, the water transport of a full cell is measured in parallel to its electrochemical performance. In this setup, a gas chromatograph and a mass spectrometer measure the selectivity of the cathode reaction.

The optimal conditions at the cathode are a subtle balance between excess and scarcity of water. Water is a reactant in the CO2 reduction reaction and helps to humidify the membrane, ensuring good ionic conductivity. Additionally, water is formed by ion recombination at the BPM junction affecting the membrane hydration state. Still, we observe that the water supply at the cathode can be insufficient, especially at high current density. However, too much water can flood the cathode and block CO2 transport to the catalyst layer.

In summary, we deliver a clearer picture of the water paths and demonstrate that optimized material and operating conditions help to overcome current limitations.

Figure 1
Early Failure Detection for CO2 Reduction Electrolyzers Via in-Line Electrochemical Impedance Spectroscopy
Authors: O'Brien Colin P. , Warkentin Hugh , Holowka Sarah , Maxwell Benjamin , Awara Mariam , Bouman Mark , Shayesteh Ali , Nicholas Rachael , Ip Alexander , Elsahwi Essam , Gabardo Christine , Sinton David
Published: February 2024

The electrochemical CO2 reduction reaction (CO2RR) presents the opportunity to produce chemical feedstocks and fuels directly from CO2. Recent achievements in energy efficiency and current density are approaching the targets required for commercial viability; however, stability remains more than two orders of magnitude below the required 80,000 h. In CO2RR there is a challenge to distinguish the cause of failure among many possibilities. Failure can result from initial setup (e.g. over or under compression of the membrane and electrodes), gradual degradation of components (e.g. cathode and anode catalyst restructuring and dissolution), accumulation of products or byproducts (e.g. alcohols or salt accumulation), or immediate failures (e.g. a hole in the membrane or a short circuit). These failure modes must be addressed to reach the targeted stability needed for the wide-scale adoption of this technology. Early identification and mitigation of these failures would increase the electrolyzer lifetime and the commercial viability of CO2RR electrolyzers.

Current techniques to characterize failures of the electrolyzer rely on post-mortem analysis of cell components. The analysis of individual components after operation may not accurately reflect their state in operando. There are techniques that are capable of analyzing the cell in operation (e.g. XAS, Raman, and TEM), but these typically require modified cell architectures and are operated at lower reaction rates. To effectively diagnose failure, the analysis technique should be applied to electrolyzers operating under realistic conditions.

Here we implement an in-line real-time electrochemical impedance spectroscopy (EIS) technique to monitor CO2RR electrolyzers during operation. EIS is a non-destructive technique that can provide continuous information on the performance of specific components within the electrolyzer. We characterize common failure modes, such as poor compression, salt formation, catalyst degradation, and short circuits, and their identifying changes to the EIS response. We extract key electrochemical parameters from the EIS response and use them to develop a framework to identify and prevent the most common failure modes. Among other applications, this framework allowed for the detection of anode catalyst degradation 11 h before other indicators, such as cell voltage or product selectivity. This technique and framework can be applied to monitor CO2 electrolyzers as they are scaled and stacked.
On the Chemomechanical Behavior in Solid-State Sodium Sulfur Batteries
Authors: Nguyen Hung Quoc , Todt Juraj , Keckes Jozef , Mehraj Ud Din Mir , Rettenwander Daniel
Published: February 2024

Sodium-sulfur batteries are promising for grid energy storage applications thanks to their high theoretical capacity, their abundance in the Earth’s crust and raw materials being cost effective. Unfortunately, their practical application is limited by several technical challenges, especially polysulfide shuttling phenomenon and accompanied volume expansion, which can lead to serious capacity degradation [1]. In this case, solid-state sodium-sulfur battery (S4B) can effectively suppress the shuttle phenomenon [2]. However, the poor triple-phase contact among active material, solid electrolytes and electroconductive agent limits the battery performance. During cycling, the complete conversion of one mole S8 into eight mole Na2S expands its volume by 260 %, and contracts upon dissociation [1].This phenomenon causes the chemo-mechanical failure, results in contact lost within the cathode composite and decreases the reversible capacity. In contrast to solid-state Li-S batteries [3][4], the understanding in case of S4B is lacking. In this study, the battery using composite cathode preparing by ball milling achieved the first discharge capacity of 1640 mAh/g and 50 mA/g current density which is close to the theoretical capacity of sulfur. This is owing to the homogeneous distribution of sulfur within the electrode and intimate contact of sulfur, solid electrolyte, and conductive carbon. Upon cycling the chemo-mechanical impact on the global performance of S4B has been studied using operando XRD, SAXS, WAXS, and electrochemical dilatometry.

References

[1] Wang, L., Wang, T., Peng, L., Wang, Y., Zhang, M., Zhou, J., ... & Duan, X. (2022). The promises, challenges, and pathways to room-temperature sodium-sulfur batteries. Nat Sci Rev, 9(3), nwab050.

[2] Tanibata, N., Deguchi, M., Hayashi, A., & Tatsumisago, M. (2017). All-solid-state Na/S batteries with a Na3PS4 electrolyte operating at room temperature. Chem Mater, 29(12), 5232-5238.

[3] Ohno, S., Koerver, R., Dewald, G., Rosenbach, C., Titscher, P., Steckermeier, D., ... & Zeier, W. G. (2019). Observation of chemomechanical failure and the influence of cutoff potentials in all-solid-state Li–S batteries. Chem Mater, 31(8), 2930-2940.

[4] Ohno, S., & Zeier, W. G. (2021). Toward Practical Solid-State Lithium–Sulfur Batteries: Challenges and Perspectives. Acc Mater Res, 2(10), 869-880.

Acknowledgement

We acknowledge financial support by Norwegian University of Science and Technology, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries).
Molten Salt Based High Entropy Electrolytes for Calcium Batteries
Authors: Timhagen Johanna , Weidow Jonathan , Johansson Patrik
Published: February 2024

Calcium (Ca) is in principle a very attractive metal anode for rechargeable batteries due to the large abundance of calcium in the Earth’s crust, its low electrochemical potential, and its low cost1. Until rather recently2, however, stable plating and stripping of Ca and hence rechargeability of Ca-batteries was deemed impossible, due to the stable phases formed at the electrolyte/electrode interface, completely blocking Ca2+ transfer3.Since this pivotal breakthrough, Ca-batteries have attracted more interest, but they are still in their very infancy and new battery designs – such as using novel electrolyte concepts – are needed to achieve stable cycling of Ca metal anodes, and this preferably at room temperature.

Here we report on the use of molten salt electrolytes, i.e. binary and multi-component systems of inorganic cations and anions, and more specifically on their physico-chemical and electrochemical properties as a function of composition with special emphasis on the compositional entropy. By using completely solvent-free electrolytes issues associated with organic electrolytes and solvents, such as the blocking of Ca2+ transfer and electrolyte flammability3, are avoided. Furthermore, they should/do not induce any large polarization, as opposed to ionic liquid-based electrolytes4.

In more detail, using the Ca(FSI)2 salt in combination with the analogous Li-, Na-, and KFSI salts in equimolar compositions, all with melting temperatures (significantly) above 100 °C, we can create electrolytes melting at ca. 60-75 °C for the ternary systems, which is further reduced to ca. 55 °C for the quaternary system. These lowered melting temperatures are achieved by increased entropy of mixing, reducing the Gibbs free energy. This can for example be illustrated by Raman spectroscopy via comparing the spectra of “as cast” electrolytes with the spectra for the ones “aged” for one week (Figure 1). Here the FSI anion band at 772 cm-1 (νsS-N-S)5 shows that the electrolytes partially (re-)crystallize/micro-separate for the ternary systems, but stay more stable for the quaternary system, which we, at least partially, attribute to an entropy effect.

Reference
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M. E. Arroyo-De Dompablo, A. Ponrouch, P. Johansson, and M. R. Palacín, Chem
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Rev., 120, 6331–6357 (2020).

A. Ponrouch, C. Frontera, F. Bardé, and M. R. Palacín, Nat. Mater., 15, 169–172 (2016).

D. Aurbach, R. Skaletsky, and Y. Gofer, J
. Electrochem Soc., 138, 3536–3545 (1991).

Q. Pang et al., Nature, 608, 704–711 (2022).

K. Matsumoto, T. Oka, T. Nohira, and R. Hagiwara, Inorg
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Figure 1
Tight-Binding Modelling of Deep Eutectic Solvent Based Electrolytes
Authors: Alhanash Mirna , Johansson Patrik
Published: February 2024

Deep eutectic solvents (DES) have in recent years gained momentum in the development of new electrolytes for lithium-ion batteries (LiBs)1. Due to their easy creation, tuning possibilities, wide electrochemical stability windows, and low vapor pressures, they are not only able to create safer LiB electrolytes as compared to traditional organic electrolytes, but more importantly, they may enable high voltage LIB cells2. One aspect not yet fully understood is the connection between the symmetry and entropy of the DES local structure and their macroscopic properties. Exploring this connection could assist in rational design of more performant electrolytes, including controlled electrochemical properties, by symmetry and entropy tuning.

Herein, we have studied in detail a few simple DES electrolytes created using the hydrogen bond donor N-methyl-acetamide (MAc) combined with each of the three different lithium salts: LiBF4, LiDFOB, and LiBOB, in 1:4 molar ratios – as previously shown advantageous 3. We chose these salts as they exhibit pseudospherical (BF4-), asymmetrical linear (DFOB), and symmetric linear (BOB) anion geometries and thus are plausible to introduce local symmetry differences. Molecular dynamic simulations were run using DFTB+ 4 and the xTB method 5, and as a first level geometrical analysis we look at the (partial) coordination and solvation numbers of the lithium ions.

References:

1. A. M. Navarro-Suarez and P. Johansson, J. Electrochem. Soc. 167 (2020) 070511.

2. H. Ogawa et al., Phys. Chem. Chem. Phys. 22 (2020) 8853-8863.

3. B. Bang et al., Korean J. Chem. Eng. 33 (2016) 1441–1446.

4. H. B. Aradi et al., J. Phys. Chem. A 111 (2007) 5678–5684.

5. S. Grimme et al., J. Chem. Theory Comp. 13 (2017) 1989-2009.
Li1.3Al0.3Ti1.7(PO4)3 /PEO Polymer Double-Layer Electrolyte to Improve Electrochemical Properties of Li-CO2 Battery
Authors: Lim HakBeom , Kim Jae-Kwang
Published: February 2024

Li−CO2 batteries are explored as promising power systems to alleviate environmental issues and to implement space applications. However, sluggish cathode kinetics of CO2 reduction/evolution result in low round-trip efficiency and poor cycling stability of the fabricated energy-storage devices.

Herein, we design a double-layer solid electrolyte to decrease interfacial resistance. Li-CO2 battery with high stability and energy density was developed using Li1.3Al0.3Ti1.7(PO4)3 (LATP) as the solid-state electrolyte and a polyethylene oxide (PEO) polymer electrolyte film together. The oxide solid electrolyte LATP has temperature stability and physical solidity, but it has a metal substitution reaction with lithium metal and a low interfacial stability with the electrode. However, this drawback can be solved by using the polymer electrolyte PEO to avoid direct contact between the lithium metal electrode and LATP. The mechanism of the Li-CO2 battery, a carbon capture technology, is used, and the characteristics of the oxide solid electrolyte and polymer electrolyte are combined to suggest a new solution for improving the stability and performance of the battery.
Designing Fluorine-Free Electrolytes for Practical Sodium Metal Anodes and Seawater Batteries
Authors: Kim Jinuk , KIM JI OH , Lee Jinwoo
Published: February 2024

Fluorine (F) is regarded as a key element in electrolytes for sodium metal anodes (SMAs) because of the formation of NaF containing solid–electrolyte interphase (SEI) layers; however, the high-cost and HF formation issues experienced by F-based electrolytes should be addressed. Herein, F-free, cost-effective 1 M NaBH4/ether-based electrolytes are proposed, motivated by the recent speculation that NaH is a “good SEI layer.” The time-of-flight secondary ion mass spectrometry (TOF-SIMS) results of sodium metal electrodes after galvanostatic cycling demonstrated that NaH is a major component of the SEI layer. In addition, the native oxide surface of sodium was converted into NaH and NaBO2 after soaking in the electrolytes, implying that “SEI reconstruction” occurred by chemical reduction. Accordingly, significantly longer cyclability was obtained in the Na‖Na symmetric cell (1200 h, 1 mA cm−2, 1 mA h cm−2) than in F-based electrolytes. In seawater batteries (SWBs), 1 M NaBH4/DEGDME (diethylene glycol dimethyl ether) delivers higher power density (2.82 mW cm−2
vs. 2.27 mW cm−2) and cyclability (300 h vs. 50 h) under 1 mA cm−2 than 1 M NaOTf/TEGDME (tetraethylene glycol dimethyl ether), which is commonly used in SWBs. In conclusion, two novel contributions of this study include the demonstration that NaH can work as a “good SEI layer” apart from NaF and the proposal of a cost-effective, F-free electrolyte for practical and large-scale SWBs.
Formation of N-Rich Solid Electrolyte Interphase with LiNO3 Solution for Lithium Metal Powder Batteries
Authors: Kang Dongyoon , Dzakpasu Cyril Bubu Bubu , Ryou Sun-Yul , Lee Hongkyung , Lee Yong Min
Published: February 2024

Conventional manufacturing process of Li metal anodes employs extrusion-pressing or deposition methods resulting in sheet or film-types, respectively. Considering the demands for high-gravimetric energy density, thinner Li metal is crucial for realizing the desired weight ratio of anode in Li metal batteries (LMBs). However, during the manufacturing process at high rate, there could be limitations such as Li damage or dendritic growth caused by excessive pressure or non-uniform deposition. Li metal powders (LMPs) are beneficial for fabricating thin Li anodes within a short time via a slurry coating process. Despite the advantages of LMP, the Li2CO3 passivation layer unevenly covering the LMP surface results in dendritic Li growth. Thus, modification of the passivation layer is very crucial to control the Li plating/stripping behavior.

Here, we suggest a LiNO3 solution-treated LMP electrode for securing robust cyclability with low overpotential in LMBs. The dissolved LiNO3 in the LMP slurry can effectively modify the passivation layer into an N-rich SEI, enabling a uniform Li+ flux. Additionally, the well-distributed LiNO3 in the LMP anode could continuously repair the SEI during cycling via a slow-release mechanism into the carbonate-based electrolyte system. As a result, the LiNO3-treated LMP electrode effectively enhances the performance and stability of LMBs. Therefore, LiNO3 solution treatment of Li metal is an attractive approach to achieving a stable and robust SEI in LMBs.
Calcium – Oxygen Batteries: Challenges and Possibilities
Authors: Slim Zaher , Šekularac Gavrilo , Mihalinec Grgur , Johansson Patrik , Panić Vladimir , Mandic Zoran
Published: February 2024

The present lithium-ion battery technology has a hard time keeping pace with the ever-increasing demands and requirements of various applications and markets. To enable continuous and sustainable growth of society, we need to develop new less expensive and less environmentally unfriendly energy storage solutions, and preferably also with higher gravimetric and volumetric energy densities, high power densities, and long(er) cycle-life. In this context, rechargeable metal–oxygen batteries are often considered the “Holy Grail” – this as the cathode of conventional metal-ion batteries most often is the most expensive component and at the same time the most challenging from both environmental and resource perspectives. An oxygen/air cathode, especially when used with a multivalent metal anode, can thus be a path to secure reliable energy storage for the future with significantly fewer concerns.

Herein we describe the efforts made in the framework of our NATO-funded project: “High-energy Ca–O2 batteries”. The overall objective is to overcome the challenges of both a reversible oxygen cathode and the passivation of calcium metal via a proper selection of Ca metal, electrolyte design, and oxygen reduction catalysts/oxygen evolution mediators. We do this by developing two compatible half-cells with full cell KPIs in mind.

Initially, we have explored, mainly via cyclic voltammetry, standard style organic electrolytes based on either Ca(TFSI)2 or Ca(OTf)2 and a boron-based additive, showing the latter to significantly enhance the Ca plating/stripping at room temperature. For the Ca(OTf)2 salt we create electrolytes using a tailored mixture of organic solvents, which not only allows for higher salt concentrations but also a wide ranges of additives possible.

At the cathode/electrolyte interface a novel bi-functional multi-component catalyst has been employed to create gas-diffusion electrode (GDE) assemblies based on transition metal (Co, Mn) oxides as interactive supports for Ir and Pt in few-monolayer sizes. These are first tested using model aqueous solutions before turning to the organic electrolytes. Preliminary tests indicate controlled kinetics of the hydrothermal oxide generation and the electrochemical deposition/galvanic replacement, which could result in adequate bi-functional activity.

Figure 1
Modelling Interfaces for Solid Electrolytes
Authors: Dippell Jan , Danner Timo , Latz Arnulf
Published: February 2024

All-solid-state batteries (ASSBs) are candidates for the next-generation of battery electric vehicles. They potentially enable the use of lithium metal as an anode material thereby highly improving the energy density of the battery. Among the most promising candidates for solid electrolytes are polycrystalline materials such as LLZO, due to their high ionic conductivity and chemical stability. Lithium dendrites form above a critical current density (CDC) of as low as 0.6 mA/cm² [1], however. While some explanations where suggested, the underlying mechanisms are not yet understood. In a recent paper a more viable CDC of 5 mA/cm² was reported, which was achieved by protonating the interfaces and grain boundaries [2], this shows that understanding both external and internal interfaces is crucial for the successful development of ASSBs.

One often used tool in battery analysis is Electrochemical Impedance Spectroscopy (EIS). We developed a continuum scale model [3] in order to compare experimental impedance data with simulated impedances for a range of possible interface configurations. Space charge layers and their effects are resolved in the model and material properties are informed by atomistic simulations.

In our contribution we simulate impedances at ASSB internal and external interfaces. The comparison to experiment helps us validate the model while better understanding the effect that different interface configurations have on resistance and capacitance. The gained understanding can inform the development and manufacturing of future ASSBs.

Acknowledgements

This work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm-Karlsruhe). The authors thank the German Ministry of Education and Research (BMBF) for funding of the project CatSE II under grant number 03XP0223E.

Han, F., Westover, A. S. et al. Nature Energy 2019, 4(3), 187-196. DOI: 1038/s41560-018-0312-z

Kim, S., Kim, J. S. et al. Nature Commun 2022, 13(1), 1-12. DOI: 10.1038/s41467-022-29531-x

Becker-Steinberger, K., Schardt, S. et al. arXiv 2021 DOI: 10.48550/arXiv.2101.10294
Li2GeS3: New Structural Type of Lithium Solid Electrolyte for All-Solid-State Batteries
Authors: Roh Ji Hun , Hong Seung-Tae
Published: February 2024

Sulfide inorganic materials exhibit favorable qualities such as high ionic conductivity and mechanical softness, making them promising candidates for solid electrolytes in Li-ion all-solid-state batteries. Sulfide solid electrolytes exist in various structural types, including β-Li3PS4, Li10GeP2S12, argyrodite, Li4PS4I, Li7P3S11, and Li1.82SiP0.036S3. While these materials exhibit high ionic conductivities of up to ~10−
2 S cm−
1 at room temperature and possess mechanical softness, they also have limitations, such as a narrow electrochemical stability window and air instability, which can hinder their scalability. The electrochemical and air stabilities of a solid electrolyte (Li–M–S, where M = non-Li metal ions) are largely governed by its stability of crystal structure consisting of MSn polyhedra and Li ions. A material with a different crystal structure would show its distinct properties. However, despite extensive research, no single structure known to date has proven superior in all aspects of performance. Given the importance of crystal structure in developing high-performance solid electrolytes, exploring and identifying novel ion-conducting materials with unique crystal structures is imperative. Additionally, once a new structural type of material is discovered, its performance can be adjusted, enhanced, or optimized through various techniques, such as chemical substitution, morphology and particle size control, and surface coating. In this work, we discovered a new crystal structural type of Li-ion conductor Li2GeS3. It was first known in 2000 by Kanno et al., with only orthorhombic unit cell dimension reported. However, our study using ab initio structure determination techniques from powder X-ray diffraction data, similar to our previous works, unveiled its structure possessing a hexagonal P61
symmetry with lattice parameters of a = 6.80098(4) Å and c = 17.92827(11) Å, revealing a new type of crystal structure. Its structure is comprised of a distorted hexagonal close-packed arrangement of sulfur anions with three asymmetric metal atoms: Ge and Li2 are in tetrahedral cavities surrounded by sulfur atoms; Li1 is in the trigonal bipyramidal cavity. The material displayed an ionic conductivity of 1.63 × 10−
8 S cm−
1 at 303 K and 2.45 × 10−
7 S cm−
1 at 383 K. Bond valence energy landscape calculations revealed three-dimensional lithium diffusion pathways within the structure. These results suggest that Li2GeS3 is expected to be a host structure from which improved ionic conductors can be derived through appropriate chemical substitution.
(Invited) New Synthesis Strategies to Develop High Performance Sulfur-Carbon Composites Cathodes for Lithium/Sulfur Batteries
Authors: Hwa Yoon
Published: February 2024

Lithium/sulfur cells (Li/S) are recognized as a highly promising, inexpensive, and high-specific energy storage system due to the low cost of elemental sulfur and high theoretical specific capacity (1,675 mAh/g) of a sulfur cathode when paired with a lithium anode.1 However, practical applications of Li/S cells have been impeded by challenges related to sulfur cathodes, such as low sulfur conductivity of sulfur, the polysulfides shuttle, and changes in electrode microstructure during cycling.2-4 Sulfur-carbon (S-C) composites have been extensively studied as an effective approach to overcome these issues and improve the electrochemical performance of Li/S cells. Carbon materials, including graphene oxide, carbon nanotubes or nanofibers, and porous carbon, have been used in sulfur cathodes due to their high surface area, excellent electrical conductivity, and sulfur-immobilizing ability from their porous structure or surface functional groups.4 Designing high-performance S-C composites involves carefully considering various factors, such as the type of carbon materials, surface area or pore volume of carbon, sulfur-carbon weight ratio, and synthesis method, to achieve optimal performance. Key design strategies for high-performance S-C composites include: (1) confining nano-sized sulfur in porous carbon, (2) coating nano-sized sulfur onto sulfur-philic functional carbon surface, (3) engineering sulfur structures that form an adequate sulfur-electrolyte interface, and (4) preserving the electronically conductive carbon network in sulfur-carbon composite to minimize the electronic resistance of the sulfur cathode.4 S-C composites consisting of sulfur nanostructures confined in carbon porous structures or coated onto large sulfur-philic surface areas of carbon (e.g., graphene oxide) are promising composite designs as they can promote the kinetics and reversibility of the electrochemical process of the sulfur cathode. In this presentation, important recent findings about how to design and synthesize high performance S-C composite design will be introduced, and their effects on the electrochemical behavior of the sulfur cathode for Li/S cells will be discussed.

References

Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Tarascon, J.-M., Nat. Mater. 2012, 11, 19–29.

Fotouhi, A.; Auger, D.J.; O’Neill, L.; Cleaver, T.; Walus, S., Energies 2017, 10, 1937.

Peng, H.-J.; Huang, J.-Q.; Cheng, X.-B.; Zhang, Q., Adv. Energy Mater. 2017, 7, 1700260.

Hwa, Y.; Cairn, E. J., ChemElectroChem 2020, 7, 3927-3942.
Engineering Transition Metal Layers for Long Lasting Anionic Redox in Layered Sodium Manganese Oxide
Authors: Voronina Natalia , Myung Seung-Taek
Published: February 2024

Oxygen-redox-based layered cathode materials are of great importance in realizing high-energy-density sodium-ion batteries (SIBs) that can satisfy the demands of next-generation energy storage technologies. However, Mn-based layered materials (P2-type Na-poor Nay[AxMn1−x]O2, where A=alkali ions) still suffer from poor reversibility during oxygen-redox reactions and low conductivity. Herein, we introduce P2-Na0.75[Li0.15Ni0.15Mn0.7]O2 and P2-Na0.6[Li0.15Co0.15Mn0.7]O2, an oxygen-redox-based layered oxide cathode materials for SIBs. The effect of Ni and Co doping on the electrochemical performance was investigated by comparison with Ni-free and Co-free P2-Na0.67[Li0.22Mn0.78]O2 material. Combined experiments (galvanostatic cycling, neutron powder diffraction (NPD), X-ray absorption spectroscopy (XANES), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (7Li NMR)) and theoretical studies (density functional theory, DFT calculations) confirmed that Ni substitution not only increases the operating voltage and decreases voltage hysteresis but also improves the cycling stability by reducing Li migration from transition metal (TM) to Na layers. It is also anticipated that having Na–O–Li configuration in a Mn4+-based layered material is important to active oxygen redox and that Co doping is crucial for improving the electrical conductivity. This research demonstrates the effect of Ni and Co doping in P2-type layered materials and suggests a new strategy of using Mn-rich cathode materials via oxygen redox with optimization of doping elements for SIBs.
(Invited) Different Designs for Ta-Doped Llzo Based Solid State Battery Prepared By Tape-Casting
Authors: Vestli Mihkel , Pateli Ioanna , Irvine John
Published: February 2024

One pathway for moving forward from current Li-ion battery technology based on organic liquid electrolytes to next-generation battery design can be implementation of solid state electrolyte along with Li metal based negative electrode. This step would result in a battery with higher energy density and improved safety.

One promising candidate material for ceramic electrolyte is garnet-type oxide LLZO (Li7La3Zr2O12) due to its relatively good chemical stability which allows relaxed requirements for processing and handling. Additionally, the doped LLZO has sufficiently good Li+ ionic conductivity (0.1 – 1 mS/cm at room temperature) and exhibits (electro-)chemical stability with the electrode materials currently under focus. To achieve low resistance values, the LLZO electrolyte needs to be prepared as a thin layer with high density. In order to integrate fabrication of LLZO electrolyte into industrial manufacturing, tape-casting can be considered as one of the low-cost scalable method for producing ceramic layers.

In this study tape-casting was used to produce Ta-doped LLZO electrolyte layers with relative density of 98% and total conductivity of 0.3 mS/cm at room temperature. In order to obtain Li/LLZO/Li symmetrical cells, interfacial treatment was used for surface of LLZO to achieve good contact and low interfacial resistance with Li metal electrode. Current densities up to 300 µA/cm2 were achieved during galvanostatic cycling for flat LLZO pellet sample at 40 °C. The cell was galvanostatically cycled with high stability for long term at current density of 100 µA/cm2.

Another design that can be considered for LLZO-based solid state battery is porous-dense-porous multilayers. This architecture has the advantage to provide support for electrolyte layer allowing to reduce its thickness and also increases the interfacial surface area which will reduce interfacial resistance. The described design allows to obtain lower resistance for the solid state battery with higher accessible current densities (>1mA/cm2), thus providing higher performance.
Sintered Electrospun Fibrous Electrodes via Compression and Laser Perforation for Redox Flow Battery
Authors: Lee Kyu , Pahlevaninezhad Maedeh , Abouali Sara , Orfino Francesco P , Roberts Edward P.L. , Kjeang Erik , Pope Michael , Gostick Jeff
Published: February 2024

The principal sources of new renewable energy, such as solar and wind power, depend strongly on the weather conditions, leading to the unstable electric power supply. Energy storage systems (ESS) has been developed to address this problem. One of the most promising technologies for energy storage device is redox flow batteries due to its high capacity and design flexibility. In particular, the vanadium redox flow battery is considered as a next-generation battery because of its safety and high efficiency, but not yet widely deployed owing to its low power density. The carbonized electrospun fibrous materials have been utilized as electrodes to overcome the flaw, because of their high specific surface area for reaction, high porosity to support flow and diffusion, and good electrical conductivity through the interconnected fibers. Typically, smaller fiber is preferential due to the exponential increase of surface area, but the small pores among the fibers reduce the permeability, limiting the electrolyte transportation or increasing parasitic pumping costs. In this study, flow battery electrodes made of electrospun carbon fibers were synthesized by applying compression during the stabilization stage. The objective was to create flow battery electrodes with higher volumetric surface area to support the electrochemical reaction while retaining the permeability. A porosity reduction of 12% was attained by this method, yielding a 50% increase of volumetric surface area, while the in-plane permeability and tortuosity were found to remain consistent. In addition, the holes perforated by a carbon dioxide laser addressed the issue of low through-plane permeability caused by the compacted fibers. All electrospun samples outperformed commercial carbon mats in flow cell tests. The compressed samples showed markedly better performance in the activation region but showed serious mass transport polarization at higher current density. The laser perforations significantly eliminated this flaw, yielding the best performance over the entire range of current density.

Figure 1