bluuebunny/crossref_metadata_2025 huggingface dataset:
Double Approach Towards 3D Electrodeposited RuOx Porous Structure for High Energy/High Power Micro-Supercapacitors
Authors: Lotfi Benali Karroubi , Patnaik Sai , Guay Daniel , Pech David
Published: December 2020

Hydrous RuOx has been one of the well-studied materials for application in supercapacitors owing to its excellent properties (high conductivity similar to metals, redox activity capable of fast faradaic reactions and structural water enabling swift proton transfer and decreased diffusion distance). The main issue regarding supercapacitors is that, they suffer from low energy density compared to batteries. One way to overcome this problem is to increase surface area of the active material and hence the energy stored through 3D structuration of current collector. Multiple techniques have been used in this regard like 3D printing, pholitography methods...etc.However, these techniques are pretty complex, time consuming and have constraining conditions. Hence, it’s necessary to develop economic and simple routes for 3D structuration of electrodes for micro-supercapacitors. One simple, time efficient and easy to set up method that can be used under ambient conditions is the electrochemical structuration using dynamic hydrogen bubble template (DHBT). With this strategy, 3D scaffolds which can hold small quantities of intrinsic pseudocapacitve materials like RuOx can be fabricated. The challenge in this latter case is magnified, needing controlled decoration of active materials for efficient utilization and full benefit of the 3D framework. Hence, the pursuit of superior micro-supercapacitors not only needs controlled deposition, but also requires stable 3D scaffolds to maximize capacitance per footprint area1. We have previously shown electrodeposition of active RuO2 on porous gold electrodes for micro-supercapacitors achieving a capacitance of 3 F/cm².

One other approach would be to deposit the active material directly by the DHBT method. As RuOx is a good conductor this would not hinder its efficiency (this would not be the case for MnO2 for example). The difficulty here is that, not all metals can be deposited by the DHBT technique as other factors play a crucial role such as the exchanged current density towards H2 evolution and mechanical stability3

In the current work, we report two different strategies for the 3D deposition of RuOx. The first is the successful fabrication of highly porous 3D platinum current collector using DHBT followed by a conformal coating of hydrous RuOx to achieve a specific capacitance as high as 10 F/cm². The second is the direct electrodeposition of the active material, RuOx, in a 3D porous structure. These two approaches are characterized and discussed within the framework of fabricating superior micro-supercapacitors with excellent capacitance and low internal resistance.

References

N. A. Kyeremateng, T. Brousse, and D. Pech, Nat. Nanotechnol., 12, 7–15 (2017)

A. Ferris, S. Garbarino, D. Guay, and D. Pech, Adv. Mater., 27, 6625–6629 (2015)

Plowman, B. J., Jones, L. A., & Bhargava, S. K. Chem. Commun., 51(21), 4331–4346.

Figure 1
Melamine-modulated Porous and Surface Structure of Nitrogendopedcarbon/Graphene Nanosheets as Stable Anode for Lithium-ion Battery
Authors: Arun Kumar P , Gayathri Sampath , Han Jong Hun
Published: December 2020

Nitrogen-doped carbon materials are the highly attractive next-generation anode for Li-ion battery due to high energy density, conducting, porous structure, and large number of binding sites. Despite these properties, intrinsic formation of micropore limits the ion/electrolyte diffusion at high discharge rates, causing capacity fading and poor cycle stability, hindering their practical application. Here, we report zeolitic imidazolate framework-derived mesoporous N-doped carbon/graphene using melamine as the pore and surface modifier. High specific capacity of 775 mAh g−1 were obtained at 1 A g−1 (2C) after 1100 cycles and excellent cycle retention of 163% (after 800 cycles) for the melamine-modified anode, compared to 91% for the unmodified one, indicating the activation-driven by the mesoporous channels. Long cycle life and excellent cycle retention were the attributes of melamine-induced features viz mesoporous structure and defective sites formed on carbon/graphene enabling effective electrolyte percolation and Li-ion storage. This strategy provides a promising approach for the design of heteroatom-doped carbonaceous material for high-performance Li-ion battery.
Molecular Crowding Electrolytes for High-Voltage Aqueous Batteries
Authors: Xie Jing , Liang Zhuojian , Lu Yi-Chun
Published: December 2020

Replacing flammable nonaqueous electrolytes with non-flammable aqueous electrolytes is critical to achieve safe, low-cost and eco-friendly Li-ion batteries. However, the voltage window of an aqueous Li-ion battery is limited by the thermodynamic stability window of water (1.23 V), which limits the energy density of the aqueous Li-ion batteries. Recently developed LiTFSI-based “water-in-salt” electrolytes with highly-concentrated salts (>21 m) have expanded the electrochemical stability window of water to over 3.0 V by decreasing the amount of free water molecules and creating artificial solid-electrode interfaces, however, raise concerns of cost and toxicity.

Molecular crowding is a common phenomenon in living cells where water activity is substantially reduced as a consequence of the changes in the water hydrogen-bonding structuring in the presence of molecular crowding agents. Herein, we introduce a molecular crowding electrolyte using water-miscible polymer poly(ethylene glycol) (PEG) as the crowding agent to decrease water activity, thereby allowing a high operational cell voltage (3.2 V) with a low salt concentration (2 m). Aqueous Li4Ti5O12/LiMn2O4 full cells with stable specific energies between 75-110 Wh kg-1 were demonstrated over 300 cycles. Extensive electrolyte characterizations including nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), online electrochemical mass spectroscopy (OEMS) and density functional theory (DFT)-molecular dynamic (MD) simulation were used to confirm the HER suppression effect of the molecular crowding aqueous electrolyte.

The molecular crowding electrolyte enables numerous negative electrode materials that can not be used in traditional aqueous battery systems. This work provides a new platform for designing aqueous electrolytes with high stability for low-cost and sustainable energy storage.

References:

[1] Xie, J., Liang, Z. & Lu, Y. C. Molecular crowding electrolytes for high-voltage aqueous batteries. Nat. Mater. (2020). https://doi.org/10.1038/s41563-020-0667-y

Acknowledgement

This work is fully supported by a grant from the Research Grant Council of Hong Kong Special Administrative Region, China (Project No. CUHK14307318).
(Invited) Local Structure of Glassy Lithium Phosphorus Oxynitride (LION) Thin Films and Their Interphases with Lithium Metal Anode
Authors: Meng Shirley Shirley
Published: December 2020

Lithium phosphorus oxynitride (LiPON) is a well-known solid-state lithium ion conductor generally produced through the amorphization of lithium phosphate in the presence of nitrogen. Despite its modest ionic conductivity, it remains popular due to its cyclability against lithium metal anodes. The nature of a stable interface beweenn LiPON and Li metal remains elusive due to the difficulty in understanding and characterizing the buried, highly reactive and beam-sensitive interface. Here we successfully preserve and probe the Li/LiPON interface by cryogenic electron microscopy (cryo-EM), one such interface capable of long-term cycling. The chemical and structural evolution along this interface is observed. A reaction mechanism for Li/LiPON interface is proposed based on the observations.
(Invited) Halogenconversion–Intercalation Chemistry in Graphite
Authors: Wang Chunsheng
Published: December 2020

We report a halogen conversion–intercalation chemistry in graphite that produces composite electrodes with a capacity of 243 milliamperehours per gram (for the total weight of the electrode) at an average potential of 4.2 volts versus Li/Li+. Experimental characterization and modelling attribute this high specific capacity to a densely packed stage-I graphite intercalation compound, C3.5[Br0.5Cl0.5], which can form reversibly in water-in-bisalt electrolyte. By coupling this cathode with a passivated graphite anode, we create a 4-voltclass aqueous Li-ion full cell with an energy density of 460 watthours per kilogram of total composite electrode and about 100 per cent Coulombic efficiency. This anion conversion–intercalation mechanism combines the high energy densities of the conversion reactions, the excellent reversibility of the intercalation mechanism and the improved safety of aqueous batteries.
Enhanced Electrode/Electrolyte Interphases in Fluorinated Orthoformate Electrolytes for Stable High-Voltage Lithium Metal Batteries
Authors: Cao Xia , Xu Wu , Zhang Ji-Guang
Published: December 2020

Rechargeable lithium (Li) metal batteries (LMBs) have been revived in recent years because of the ever-increasing demand for high-energy-density batteries. 1,2 However, significant challenges, such as low Columbic efficiency (CE), pulverization and large volume expansion related to the Li metal anode still limit the large-scale application of these batteries. 3 Here, we report an approach to improve the Li CE and minimize the Li pulverization and volume expansion by using fluorinated orthoformate in electrolytes. 4 Tris(2,2,2-trifluoroethyl) orthoformate (TFEO) functions as an efficient diluent in electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) and 1,2-dimethoxyethane (DME) and formulates highly concentrated LiFSI-DME clusters that are dispersed among the TFEO diluent. Such localized high-concentration electrolytes demonstrate superior electrochemical properties when used in LMBs with a high voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. The mechanisms behind the long cycle life of Li||NMC811 cells under practical conditions are mainly the formation of highly effective solid electrolyte interphase and cathode electrolyte interphase, which are monolithic and prevent continuous electrode/electrolyte side reactions. This work provides guidance for further development of electrolytes for high-energy-density LMBs. The details will be discussed during the presentation.

References

1 J.-G. Zhang, W. Xu, W. A. Henderson, Lithium Metal Anodes and Rechargeable Lithium Metal Batteries. XV, 194 (Springer International Publishing, 2017).

2 J. Liu, et al. Pathways for practical high-energy long-cycling lithium metal batteries. Nature Energy
4, 180-186 (2019).

3 C. Niu, et al. High-energy lithium metal pouch cells with limited anode swelling and long stable cycles. Nature Energy
4, 551-559 (2019).

4 X. Cao, et al. Monolithic solid–electrolyte interphases formed in fluorinated orthoformate-based electrolytes minimize Li depletion and pulverization. Nature Energy
4, 796-805 (2019).
Effects of Aniline Tetramer-Co-Acrylic Monomer Grafted to Polysaccharide Backbone As a Conductive and Adhesive Binder for High Capacity Si/C Composite Anodes
Authors: OH Eun-Suok , Gendensuren Bolormaa , Taewon Kim
Published: December 2020

Conducting polymers such as polyaniline and polypyrrole have been sometimes described as a potential candidate binder for high silicon anode materials due to its low price, high conductivity, and simple synthesis. The manufacturing process of conducing polymerbased electrodes requires environmental-unfriendly organic solvents such as n-methylpyrrolidone. Due to the drawback, natural polysaccharides blended with the conductive polymers have been often investigated as water-soluble, electronically conductive, and adhesive binder to improve the electrochemical performance of the high-capacity Si anodes. However, the polymer blends are still needed to modify their properties through functionalization with some additional groups, for example, grafting with adhesive monomers and crosslinking for high adhesion strength.

In this study, we first prepared aniline tetramer-co-acrylic monomer (AT-Am) by two step polymerization using 4-aminodiphenylamine in acidic solution at ~ 0°C, and then AT was reacted with acryloyl chloride monomer at room temperature for 3 hours to produce AT-Am monomer. Finally, AT-Am and pure acrylamide (AAm) monomers with various weight ratios are grafted and polymerized to the backbone of sodium alginate (Alg). Here AT and AAm have roles of electronic conduction and strong adhesion, respectively. This water-treatable alginate-graft-poly(acrylamide-aniline tetramer) (Alg-g-PAAT) was used as a conductive and adhesive binder for Si/C composite anodes to improve electronic conduction and adhesion ability when compared to natural Alg and Alg-g-PAAm. As a result, the Si/C anode containing Alg-g-PAAT yielded 800 mAh g-1 after 200 cycles with maintaining high columbic efficiency when compared to Alg-g-PAAm and physical blend between Alg-g-PAAm and AT.
Effect of CNTs Support in CL of PEMFC on the Structure of Ionomer Ultra-Thin Film
Authors: Wan Yue , Qiu Diankai , Yi Peiyun , Peng Linfa , Lai Xinmin
Published: December 2020

Proton Exchange Membrane Fuel Cell (PEMFC) is an energy converter with high power density, no carbon emissions, and features of quick start-up. It has extremely broad application prospects. However, despite these advantages, there are still several obstacles that hinder the performance improvement of PEMFC. Among them, the ionomer film in the catalyst layer (CL) and the catalyst constitute a multi-phase nano-scale structural morphology, which is essential for the transportation of protons and water, and the improvement of the utilization rate of the catalyst. In order to improve the material transport capacity of the above-mentioned parts, the water transport performance can be optimized by improving the structure of carbon support.A classic molecular dynamics simulation was conducted to established a model of platinum particles on carbon nanotubes (CNTs),which explore the effect of the carbon surface on the molecular level structure of the ionomer film, and the corresponding structure−property relationships. the following simulations is mainly conducted: 1) the influence of CNTs on the self-assembly process of ionomer on its surface, 2) the effect of ionomer ratio on film morphology, 3) structural composition around CNTs with different water contents，4) the influence of the presence of nano-platinum particles on the structure of the ionomer film around the CNTs. At the same time, the above model was used to compare the morphology of the water area inside the nano-thick ionomer film formed under different conditions，the formation process of the water area around the CNTs, and the proton transport capacity of the corresponding structure. These results provide a molecular basis for the study of the morphology of the nanostructures inside the CL, and give the way in which the CNTs affect the ionomer film structure and water transport capacity.

Figure 1
(Invited) Electrolyte and Interphase Revealed By Cryogenic Electron Microscopy and Solvation Measurement
Authors: Cui Yi
Published: December 2020

Obtaining atomic and molecular level understanding of electrolyte and electrode-electrolyte interphase is critical to the battery developments. In this talk, I will present a multimodal approach combining the powerful cryogenic electron microscopy technique, electrochemical technique and solvation entropy and free energy measurements. I will discover including: 1) atom-resolved images of solid electrolyte interphase for Li metal and Si anodes; 2) Insight on the debate on the existence of cathode electrolyte interphase; 3) the solvation structure and related thermodynamic parameters and their correlation with electrochemical performance.
Suppressing Lithium Dendrite Growth with Nanoparticle-Dispersed Colloidal Electrolytes
Authors: Lee Hongkyung , Kwak Won-Jin , Lee Jinhong , Kim Hee-Tak , Lim Hyung-Seok , Cao Xia , Ren Xiaodi , Rodriguez Perez Ismael , Zhang Ji-Guang
Published: December 2020

Lithium (Li) metal has been considered as a very promising anode material for next-generation batteries because of its low electronegativity (-3.04 V), low gravimetric density (0.53 g cc-1) and ultrahigh specific capacity (3860 mAh g-1). The recent simulations forecast that the rechargeable Li metal batteries (LMBs) coupled with the conventional transient metal oxide cathodes and the Li metal anode can deliver a high gravimetric energy density of up to 500 Wh kg-1. However, significant challenges, including low Coulombic eﬃciency (CE), short cycle life, and safety concerns have plagued the practical applications of Li metal as the anode in recharge batteries.

However, its poor cycling stability due to Li dendrite formation and excessive Li pulverization is the major hurdle for its practical applications. In this work, we present a silica (SiO2) nanoparticle-dispersed colloidal electrolyte (NDCE) and its design principle for suppressing Li dendrite formation. SiO2 nanoclusters over the percolated threshold of Li+ ion transport play roles of enhancing the Li+ transference number and increasing the Li+ diffusivity in the vicinity of the Li plating substrate. NDCE enables less-dendritic Li plating by manipulating the nucleation-growth mode and extending Sand's time. Moreover, SiO2 can interplay with the electrolyte at the Li-metal surface, and thus, it can modify the solid-electrolyte interphase (SEI) structure by enriching fluorinated compounds. The initial control of the Li plating morphology and SEI structure by NDCE leads to a more uniform and denser Li deposition upon subsequent cycling, resulting in three-fold enhancement of the cycle life. The efficacy of the NDCEs has been further demonstrated by the practical battery design featuring a commercial-level NMC cathode (4.2 mAh cm-2) and very thin Li metal (40 μm) anode.
Nanospace-Assisted Anti-Oxidative Li Storage on Carbon Nanotubes
Authors: Yoo JongTae , Lee Sang-Young
Published: December 2020

Lithium (Li) metal has attracted significant interest as a next-generation battery anodes due to its high theoretical speciﬁc capacity and low redox potential. However, inhomogeneous plating/stripping behavior of Li metal accelerates Li-consuming parasitic reaction and sometimes provokes an internal short circuit problem. In particular, its environmental vulnerability (e.g., notorious reactivity upon exposure to air and water) due to the electrochemical instability poses a formidable challenge to commercial applications, thus it should be resolved as an indispensable prerequisite in addition to resolving the concerns on cell performance and safety.

Here, we report a new class of anti-oxidative Li reservoir based on nanospaces of carbon nanotube (CNT) bundles. The CNT bundles are formed by assembling themselves via van der Waals interactions, producing one-dimensional nanospaces (i.e., external grooves and interstitial channels). The Li preferentially stored in the interstitial channels is chemically stable against to air and water. Notably, the Li electrochemically extracted from Li-confined CNTs onto a copper (Cu) foil prohibits reliable electrochemical performance (e.g., stable charge/discharge behavior) comparable to those of pristine Li foils. We envision that this nanospace reservoir strategy will open a new avenue for development of environmentally tolerant, high-capacity Li storage.
A Redox-Active Organic Salt for Safer Na-Ion Batteries
Authors: Ji Weixiao
Published: December 2020

Overcharge abuse can trigger thermal runaway when a device is left unattended. Redox shuttles, as economic and efficient electrolyte additives, have been proven to provide reliable and reversible protection for state-of-art Li-ion batteries (LIBs) against overcharge. Here, a functional organic salt, trisaminocyclopropenium perchlorate (TAC•ClO4), is developed and employed as a redox shuttle for overcharge protection in a Na-ion battery system. This type of novel redox shuttle molecule is reported for the first time. As a unique ionic compound with the smallest aromatic ring structure, TAC•ClO4 exhibits distinctive attributes of fast diffusion, high solubility, and ultrahigh chemical/electrochemical stability in both redox states. With merely 0.1 M TAC•ClO4 in electrolyte, Na3V2(PO4)3 cathode can carry overcharge current even up to 10C or 400% SOC. Na3V2(PO4)3/hard carbon cells demonstrated strong anti-overcharging ability of 176 cycles at 0.5C rate and 54 cycles at 1C rate with 100% overcharge. Moreover, TAC•ClO4 addition has little impact on the electrochemical performance of Na-ion batteries, especially on the rate performance and the initial Columbic efficiency. Interestingly, a unique and reversible electrochromic behavior of TAC•ClO4 electrolyte can promptly provide the device an overcharge alarm under a designed potential to further enhance the safety level.
Suitability of Ethyl Cellulose As a Binder in Positive Electrode of Aqueous Li-Ion Battery
Authors: Sepp Silver , Peljo Pekka
Published: December 2020

Novel materials for energy storage devices need to be affordable, durable, safe and environmentally friendly. PVDF, which is the most popular polymer used as a binder in battery cathode electrodes, requires the use of and toxic solvents for processing, such as N-methyl-pyrrolidone (NMP).1 Ethyl cellulose is a biodegradable and water-insoluble polymer. Ethyl cellulose based slurry can be prepared using ethanol as solvent, which makes the process cheaper and more sustainable. Replacing PVDF with more environmentally friendly binder like ethyl cellulose in positive electrode of aqueous Li-ion battery would be beneficial in many ways. It would shorten the assembly procedure due to high speed of solvent evaporation, there are no strict requirements for humidity control and the recycling procedure is easier as there are no fluorinated compounds.2 Therefore, this replacement would enable to produce safer and cheaper energy storage devices.

In this work electrodes with different composition have been described using galvanostatic charging-discharging and cyclic voltammetry. LiMn2O4 (LMO) has been used as active material for cathode, carbon black Super P as conductive additive and PDVF or ethyl cellulose as a binder. The electrodes were prepared using different mass ratios of conductive additive and binder to evaluate the performance of this sustainable polymer. Using ethyl cellulose as a binder, discharge capacity 100 mAhg−
1 was achieved at 0.2C rate for LMO cathode which is comparable to the results obtained with PVDF as a binder. 500 cycles at the rate of 1C showed somewhat better capacity retention for electrodes prepared using PVDF. However, the results show that ethyl cellulose is a promising option to replace PVDF as cathode binder in aqueous systems. Further optimization is needed to prepare these novel and sustainable cathodes for aqueous Li-ion battery.

The research was supported by the Estonian Research Council grant PUTJD956 and Magnus Ehrnrooth Foundation.

References:

I. Doberdò, N. Löffler, N. Laszczynski, D. Cericola, N. Penazzi, S. Bodoardo, G. T. Kim, and S. Passerini, J. Power Sources, 248, 1000–1006 (2014).

L. Ibing, T. Gallasch, P. Schneider, P. Niehoff, A. Hintennach, M. Winter, and F. M. Schappacher, J. Power Sources, 423, 183–191 (2019).
Suppressing Electrochemical Instabilities of Li Metal Using Ionomer-Based Interfaces
Authors: Huang Zhuojun
Published: December 2020

A fundamental challenge shared across many energy storage devices, is the complexity of electrochemistry at the electrode-electrolyte interfaces that impacts the faradaic efficiency, operational rate capability and lifetime. Specifically, in energy-dense lithium metal batteries, the charging process results in morphological heterogeneity of the metal anode, leading to battery failure by short-circuit or capacity fade. Perhaps, a facile way of addressing these challenges is designing a polymer thin-film at the electrode-electrolyte interface. We envision that an ideal interface should be based on several design principles including: presence of Li+ ion conduction pathway; chemically inert, mechanically robust, adaptive to volume changes and solution-processable for large scale thin-film casting.

Here, we use free-radical polymerization technique to synthesize novel stimuli-responsive polymers which exhibit the aforementioned characteristics. Unlike, previous works where the electrode coating acts as a pure physical barrier, the designer polymers in this work possess multifunctional characteristics to suppress different electrochemical instabilities. Because of the viscoelastic and electroactive nature of the polymers, they respond to any morphological changes of the electrodes during electrodeposition, giving rise to an electrochemical shielding mechanism that modulates lithium ion migration pathway and prevents surface roughening.

This work takes advantage of contemporary characterizations techniques like NMR, voltammetry and rheology to mechanistically understand the role of polymer dynamics and ion content on the electrodeposition morphology. We show that systematic optimization of these parameters can significantly boost the coulombic efficiency of the battery. Remarkably, we found that these polymer coatings can enhance the lifetime of conventional high-voltage lithium metal battery by at least two-times.
Rational Design of Solid-Liquid Interphases for High-Energy Sodium Metal Batteries
Authors: Wei Shuya
Published: December 2020

Advances in the basic science and engineering principles of electrochemical energy storage is imperative for significant progress in electronic devices. Metal based batteries comprising of a reactive metal (like Li, Na, Al) as the anode have attracted remarkable attention due to their promise of improving the anode-specific capacity by as much as 10-fold, compared to the current state-of-art Li-ion battery that uses a graphitic anode. A persistent challenge with batteries based on the metallic anode, concerns their propensity to fail due to short-circuits produced by dendrite growth during battery recharge, as well as by runaway of the cell resistance due to internal side reactions with the liquid electrolyte. In this talk, I will discuss my research that utilizes ion transport modeling and contemporary experimental efforts to fundamentally understand and to thereby develop rational designs for electrode-electrolyte interphases that overcome these challenges. On the basis of a linear stability analysis of dendrite growth during metal electrodeposition, we have showed that a small fraction of immobilized anions near the electrodes is important in stabilizing metals against dendrite formation. To evaluate this proposal, we designed polymeric electrolytes with tunable molecular weight and quantified the stability of metal electrodeposition in these systems. Direct visualization of electrodeposition using these electrolytes showed remarkable agreement with the theoretical predictions. Furthermore, when operated in a battery, the polymeric electrolytes demonstrated stable and dendrite-free galvanostatic polarization of sodium metal metals for over 100 hours at relatively high current density.
Solute and Solvent Structural Effects in Concentrated-Electrolyte Transport
Authors: Wang Andrew , Fawdon Jack , Hou Tianhong , Pasta Mauro , Monroe Charles W.
Published: December 2020

Super-concentration of electrolytic solutions has been hypothesized as a route to improve battery performance [1]. To predict electrolyte behavior accurately in superconcentrated systems, one must account for their fundamentally different molecular structures. Interactions between species such as ion pairs in concentrated electrolytes may impact the transport laws governing diffusion, migration, and convection, and solute-volume effects may be large because the solution volume fraction occupied by salt is extremely high.

Transport phenomena relating to solute and solvent structure, such as Faradaic convection and the excluded-volume effect, can become dominant in the superconcentrated regime [2]. In very concentrated electrolytes convection can be important because when the salt occupies a large volume fraction of the solution, salt flux across the boundary of a solution drives a bulk solution velocity through overall mass continuity. Experiments demonstrate that at high concentration, viscosity no longer determines ion mobility, i.e., the Stokes–Einstein relation fails. The dynamics of ion-pair formation and salt association/dissociation kinetics both can impact the availability of charge-carrying species in an electrolyte. Experimentally, Faradaic convection can be quantified by combining densitometry with electrochemical measurements. Ion speciation and extent of dissociation can be quantified with spectroscopic techniques.

Newman’s application of Onsager–Stefan–Maxwell theory to electrochemical transport considers solute/solute interactions neglected in Nernst–Planck dilute solution theory [3]. We will add to this perspective by discussing how solute-volume effects and ion-association equilibria additionally influence apparent flux-explicit transport properties such as conductivity, diffusivity and transference number [4].

[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E. & Yamada, A. Advances and issues in developing salt-concentrated battery electrolytes. Nat. Energy
4, 269–280 (2019).

[2] Liu, J. & Monroe, C. W. Solute-volume effects in electrolyte transport. Electrochim. Acta
135, 447–460 (2014).

[3] Monroe, C. W. & Delacourt, C. Continuum transport laws for locally non-neutral concentrated electrolytes. Electrochim. Acta
114, 649–657 (2013).

[4] Hou, T. & Monroe, C. W. Composition-dependent thermodynamic and mass-transport characterization of lithium hexafluorophosphate in propylene carbonate. Electrochim. Acta (2019).

Figure 1
An Artificial Hybrid Solid Electrolyte Interface for Reviving Lithium Metal Battery
Authors: Pathak Rajesh , Chen Ke , Qiao Qiquan , Zhou Yue
Published: December 2020

Lithium (Li)-metal anode has attracted extensive attention owing to its high theoretical specific capacity (3860 mAh/g), which is more than ten times to that of graphite anode (372 mAh/g). However, the notorious reactivity of Li-metal prevents their practical applications due to undesired Li dendrite growth and unstable solid electrolyte interphase (SEI) formation. Here, we developed a facile, cost-effective and one-step approach for creating an artificial Li-metal/electrolyte interface by treating Li metal anode with an electrolyte containing SnF2. As a result, the artificial SEI composed of LiF, Sn and Sn-Li alloy was formed with higher ionic conductivity and increased Young’s modulus. The higher ionic conductivity and larger Young’s modulus of the artificial layer facilitate fast Li-ion diffusion and suppress Li dendrite growth, respectively. The hybrid artificial SEI showed a synergistic effect of storing Li by a reversible Sn-Li alloy formation and Li plating underneath the SEI. The artificial SEI treated Li symmetrical cells showed outstanding plating/stripping cycles (~2325 hrs) with reduced overpotential compared to the bare Li. Coupled with a high-loading (11.88 mg.cm-2) LiNi1/3Co1/3Mn1/3O2 (NMC111) cathode, the SEI protected Li full cells exhibited remarkable performance such as longer stable cycling, higher capacity retention and higher capacity at higher rates compared to the bare Li anode.
Nanoporous Au-Cu-Pt As a Superior Electro-Catalyst for the Methanol Oxidation Reaction
Authors: Xie Yunxiang , Dimitrov Nikolay
Published: December 2020

Among fuel cells, the direct methanol fuel cell (DMFC) has attracted great attention and has been considered a very promising power source because of the ease of methanol transportation and its high energy density. A major limiting factor hindering DMFC’s commercial application is the poor catalytic performance in the anode (methanol oxidation reaction). The methanol oxidation reaction (MOR) requires (OH-) from water dissociation as an oxygen donor for the reaction; however, the slow water dissociation on Pt limits the rate of MOR. In addition to the sluggish catalytic activity, the other major impediment for Pt catalysts is the generation of carbon monoxide (CO) during the MOR process.In order to improve the catalytic performance of MOR catalysts, a variety of catalyst design strategies have been devised. The interesting way of carrying out the MOR catalytic process is the non-CO pathway which takes place on Pt-Au bimetallic catalysts, thus eliminating CO poisoning. However, the overall activity of Pt-Au alloys in MOR is relatively low, which ultimately limits the application of Pt-Au catalysts.

In this study, a nanoporous (np) Au-Cu-Pt thin-film catalyst with a fine structure and tunable composition is synthesized by using a facile method involving successive electrodeposition and de-alloying. SEM, SEM-EDX and ICP have been used for morphology characterization and composition assessment. Pb under-potential deposition (UPD), H UPD and CO stripping tests have been employed to determine the electrochemical active surface area (ECSA) and to probe the Pt active sites specifically. Also, cyclic voltammetry (CV) tests have been performed to assess the catalytic performance in MOR. Finally, long-term CV and chronoamperometry (constant potential) tests have been used to study and evaluate the durability of accordingly synthesized catalyst for MOR.

The prepared np Au-Cu-(8% in the precursor alloy)Pt catalyst exhibits outstanding mass and specific activity toward the MOR, which is approximately six- and nine-times higher than the activity of a commercial Pt/C(40%) counterpart, respectively. A negative 75 mV onset potential shift upon the MOR anodic scan on the np Au-Cu-(8 %)Pt catalyst in comparison with Pt/C(40%) corroborates its higher catalytic activity. Furthermore, the alloy catalyst demonstrates better durability than the Pt/C(40%) counterpart in a three-hour constant potential test and exhibits full post-factum recovery of its cycling activity. In addition, it retains more than 60% of its original activity after 3000 cycles of an accelerated degradation test.

Reference:

Xie, Y., Li, C., Razek, S.A., Fang, J. and Dimitrov, N., 2020. Synthesis of Nanoporous Au− Cu− Pt Alloy as a Superior Catalyst for the Methanol Oxidation Reaction. ChemElectroChem, 7(2), pp.569-580.
(Keynote) Halide-Based Solid-State Batteries: Electrolyte, Stability, Interface and Electrode
Authors: Sun Xueliang
Published: December 2020

All-state-state lithium batteries (ASSLBs) have gained worldwide attention because of intrinsic safety and increased energy density. Compared with other types of solid-state electrolytes including oxide-based, polymer-based and sulfide-based electrolytes, recently-developed halide-based solid-state electrolytes (SSEs) have garnered considerable attention for all-solid-state lithium batteries (ASSLBs) due to the high ionic conductivity, high oxidation voltage and good stability toward oxide cathode materials [1]. However, there are still many challenges in halide-based solid-state electrolytes for ASSLBs including controllable and mass-production synthesis, achieving high humidity tolerance and demonstrate high-performance of ASSLBs; in particular, increased understanding of mechanisms during synthesis and tuning their properties of the electrolytes as well as interface with electrode materials[1].

In this talk, (i) I will demonstrate synthesis strategy [2-3], in particular, new and salable water-mediated synthesis method [2]. (ii) I will report a systematic study on the correlations among structural evolution, Li+ migration properties, and humidity stability resulting of the halide-based electrolytes, along with in-situ characterization for understanding of the mechanisms [4], (iii) Full cell battery performance will be optimized [5], and (iv) humidity ability [6]. In the end, energy densities of ASSLBs using different solid-state electrolytes in ASSLBs will be discussed.

References:

1. X. Li, J. Liang, X. Yang, K. Adair, C. Wang, F. Zhao, X. Sun. Progress and Perspectives of Halide-based Lithium Conductors for All-Solid-State Batteries. Energy Environ. Sci., 13, 1429-1461 (2020).

2. X. Li, J. Liang, X. Sun, et al., H2O-Mediated Synthesis of Superionic Halide Solid Electrolyte. Angewandte Chemie International Edition, 58,1-7(2019).

3. X. Li, J. Liang, X. Sun, et al.,. Air-Stable Li3InCl6 Electrolyte with High Voltage Compatibility for All-Solid-State Batteries. Energy Environ. Sci., 12, 2665 - 267 (2019).

4. X. Li, J. Liang, X. Sun, et al.,. Origin of Superionic Halide Solid Electrolytes with High Humidity Tolerance, 2020, J. Am. Chem. Soc. 142, 7012-7022 (2020).

5. C. Wang, X. Li, J. Liang, X. Sun, et al., Eliminating Interfacial Resistance in All-Inorganic Batteries by In-situ Interfacial Growth of Halide-based Electrolyte. Nano Energy, 2020, in press.

X. Li, J. Liang, X. Sun, et al., Origin of Superionic Li3Y1-xInxCl6 Halide Solid Electrolytes with High

6. Humidity Tolerance, Nano Letters, in press, 2020.
High Pressure in-Situ X-Ray CT Measurement of Sulfide Solid Electrolyte for All-Solid-State Lithium Ion Battery
Authors: Kodama Manabu , Ohashi Akinari , Horikawa Naoki , Kawamura Katsuyuki , Hirai Shuichiro
Published: December 2020

The sulfide solid electrolyte has a high ionic conductivity and is a candidate for use as the solid electrolyte in lithium ion batteries used for electrical vehicles [1]. A previous study showed that high ionic conductivity is achieved with compression of solid electrolyte powder by suppressing the void between the solid electrolyte particles as the structure of the solid electrolyte has a strong correlation with the ionic conductivity. However, this correlation has not been discussed directly.

In this study, the solid electrolyte three dimensional structure is measured with high pressure in-situ X-ray CT measurement and its ionic conductivity measured by EIS to elucidate the correlation between the structure and ionic conductivity. Moreover, three dimensional electromagnetic field numerical simulations based on the Maxwell and Nernst-Prank equations are conducted with the X-ray CT images to build a numerical model of the ionic conduction in a compressed sulfide solid electrolyte. The solid electrolyte used in this experiment is Li6PS5Cl [2].

Figure 1 illustrates the X-ray CT images of the sulfide solid electrolyte with various applied pressures. With a low applied pressure of 10.5 MPa (Fig.1 (a)), solid electrolyte particles exist independently, and there are many voids between them. The ionic conductivity with this structure is 0.35 mS/cm. With the increase in applied pressure to 95.0 MPa, the voids between the solid electrolyte particles disappear as shown in Fig.1 (b). This disappearance is owing to the room temperature sintering with creeping of solid electrolyte with high pressure [3]. The ionic conductivity with this structure is 1.15 mS/cm. The three dimensional electromagnetic numerical results for each X-ray CT image is 0.21 mS/cm and 1.16 mS/cm and these numerical results almost agree with the experimental results. In the numerical simulation, contact resistance, inhomogeneity of the ionic conductivity, and anisotropy of the ionic conductivity are not considered and only the distribution of the solid electrolyte and voids are inputted. Therefore, this numerical result suggests that the contact resistance between solid electrolyte particles can be neglected for numerical simulation of sulfide solid electrolytes.

Acknowledgement

This study is partially supported by the Japan Keirin Autorace Foundation (JKA).

References

[1] F. Zheng, M. Kotobukia, S. Song, M. O. Lai, L. Lu, J. Power Sources 389 (2018) 198–213.

[2] A. Sakuda, A. Hayashi, M. Tatsumisago, Sci. Rep., 3 (2013), 2261.

[3] S. Boulineau, M. Courty, J. M. Tarascon, V. Viallet, Solid State Ionics, 221 (2012) 1–5.

Figure 1
Carbon Supported Ni-Mo Catalysts for Reversible Alkaline Hydrogen Electrochemistry
Authors: Patil Rituja , House Stephen D , Yang Judith C , McKone James
Published: December 2020

Alkaline anion exchange membrane (AAEM) electrolyzers are attractive for cost-effective production of hydrogen using carbon-free electricity as the energy input. These devices facilitate the use of non-precious metal catalysts and ancillary components, which together offer significant reduction in capital cost. When combined with the low and still rapidly decreasing cost of renewable electricity, AAEM electrolyzers have the potential to meet the cost target of $2/kg for hydrogen production set by the US Department of Energy. Despite this promise, considerable work remains to develop efficient and stable catalysts and membranes for use under alkaline operating conditions. In this context, non-precious Ni-based catalysts are among the most promising for use as hydrogen-evolving cathodes. Our focus is on Ni-Mo composites, which have been studied and deployed for decades as alkaline hydrogen evolution catalysts, but the associated reaction mechanism remains relatively less explored.

We recently showed that Ni-Mo catalysts comprise a Ni-rich metallic core surrounded by Mo-rich oxide shell, where the electrically resistive shell limits the overall catalytic activity in unsupported thin films. By contrast, incorporation of conductive carbon black supports significantly enhances catalyst mass activity toward the alkaline hydrogen evolution reaction (HER) without measurably altering the composition and structure of the active Ni-Mo composite. More recently, we have directly observed the evolution of the core-shell architecture in Ni-Mo catalysts using in situ environmental transmission electron microscopy (ETEM). These measurements suggest that thermal reduction of NiMoO4 precursors proceeds in at least two sequential events. When combined with HER catalytic activity measurements, the ETEM data show that the most competent Ni-Mo catalyst requires intimate contact between a metallic, Ni-rich face-centered cubic alloy phase and a Mo-rich suboxide phase. Carbon supported Ni-Mo catalyst composites were also found to be active for the alkaline hydrogen oxidation reaction (HOR), which lends to their potential use in unitized reversible fuel cell systems. Preliminary results suggest that the Ni-Mo mass loading relative to the carbon support has a stronger influence of its HOR activity than for the HER, suggesting that mass transfer plays a significant role in the practical HOR activity.
Structure–Property Relationship in Poly(Terphenylene)-Based Anion Exchange Membranes; The Impact of Backbone Structure for the Free Volume Control in Alkaline Fuel Cell Application
Authors: T S Mayadevi , Kim Tae-Hyun
Published: December 2020

The commercial application of anion exchange membrane fuel cells (AEMFCs) has been impeded by the lack of high ion conductivity and mechanical/chemical stability of the currently used anion exchange membranes (AEMs). A new class of aromatic polymers, which contain conducting head groups directly onto the polymer backbone were developed to attain long-term stability along with high conductivity. Inspired from this, a series of poly(terphenylene)-based anion exchange membranes devoid of benzylic sites or aryl-ether bonds, that are vulnerable to attack by hydroxide ion, were synthesized and were investigated for their physicochemical properties for alkaline fuel cell applications. The polymer backbones having N,N-dimethylpiperidinium conducting head group were synthesized using acid-catalyzed Friedel-Crafts polycondensation reaction between N-methyl-4-piperidone and meta/para-terphenyl monomers. Along with meta-terphenyl homopolymer, another three sets of copolymers were synthesized by introducing the kink structured meta-terphenyl in different ratios with para-terphenyl to control the free volume. The copolymer membrane, m-p-CoP-50, prepared from meta/para terphenyl monomers with a 1:1 molar ratio displayed a well-balanced water uptake, dimensional stability and the highest conductivity. The experimental procedures and the results will be discussed in detail.
Electrochemical Study of Bi2Se3 Single Crystals
Authors: Yang Chaolong , Song Fengqi , Schwarzacher Walther
Published: December 2020

Bi2Se3 single crystals have attracted the attention of an extensive research community because of their many attractive properties: as a model topological insulator (TI), a layered structure and a promising platform for surface catalysis studies. However, despite often being studied under ultrahigh vacuum, there are very few studies of either the surface chemistry at ambient pressure or their electrochemistry. We have already demonstrated the protection and in-situ imaging and modification of bismuth chalcogenide single crystals in an electrochemical environment1,2. The present work shows that different choices of chalcogenide (Se in place of Te) and electrolyte yield differences in the oxidative dissolution process. We also investigate how the charge transfer resistance changes during electrochemical oxidation and reduction processes. Oxidative dissolution significantly increases the Bi2Se3 charge transfer resistance, measured by electrochemical impedance spectroscopy (EIS) using the ferrocyanide/ferricyanide redox couple. The charge transfer resistance only partially recovers during subsequent electrochemical reduction. As a further step in the electrochemical modification of bismuth chalcogenides, we studied metal electrodeposition. For example, we imaged Bi electrodeposition on a bismuth selenide single crystal in-situ for the first time, showing that it gives rise to characteristic triangular structures with kink-free step edges, the motion of which can be followed during island growth. The deposition is also highly reversible.
Electrochemical Behaviour of Steel in Aqueous Alkanolamines for CO2 capture
Authors: Sadeek Samara , Kelsall Geoff , Sedransk Campbell Kyra , Hankin Anna
Published: December 2020

Carbon dioxide capture using absorption-desorption by alkanolamines can mitigate carbon dioxide emissions, but corrosion of the steel reactor systems remains a limitation that depends on the amine type. The primary amine, monoethanolamine (MEA), a commonly used solvent for this process, forms carbamate ions (CH2CH2OHNHCOO-)when it absorbs CO2 and has been reported to corrode carbon steel. CO2 absorption in another popular solvent, the tertiary amine, methyldiethanolamine (MDEA), does not form carbamate, but rather hydrogen carbonate ions (HCO3
-), which facilitate FeCO3 formation on steel surfaces (Fig.1), limiting their corrosion rates.

The surface reactions on iron in CO2-aqueous alkanolamine solutions were investigated by measuring current transients at an applied potential of -0.350 V vs. SHE at temperatures of 25 – 80 °C, concentrations of 5 and 3 M and various pHs. In aqueous 5 M MDEA solutions, an electrically resistive film formed on iron, evidenced from the sharp decrease in current density to ca. zero (Fig.2); similar behaviour was exhibited in 3 M MDEA(aq). By contrast, current transients measured in aqueous MEA solutions did not decrease sharply. Ex-situ surface characterisation by SEM and EDX detected FeCO3 (Fig.1) on the iron exposed to MDEA, but not on the iron sample exposed to MEA.

We shall explain the formation mechanisms of films, if present, and report impedance spectra used to define conditions corresponding to electrically resistive, stable film formation that could be used to inhibit steel corrosion in carbon capture plants.

Figure 1