Electrolyte Molecules Research Articles

Permanent Nanobubbles in Water: Liquefied Hollow Carbon Spheres Break the Limiting Diffusion Current of Oxygen Reduction Reaction.

Porous liquids have traditionally been designed with sterically hindered solvents. Alternatively, recent efforts rely on dispersing microporous frameworks in simpler solvents like water. Here we report a unique strategy to construct macroporous water by selectively incorporating hydrophilicity on the surfaces of hydrophobic hollow carbon spheres (HCS). Specifically, we show that the stable dispersion surface ionized HCS in water while retaining the inherent porosity. The electrocatalytic conversion of small gas molecules in aqueous electrolytes is limited by the concentration and diffusion rates of gas molecules in water. In this case, macroporous water exhibited 6 times gas uptake compared to nonporous (pure) water. By leveraging the high gas capacity and enhanced diffusion kinetics, the limiting diffusion current of oxygen reduction reaction (ORR) in macroporous water is 2 times that in nonporous water, offering promising prospects for sustainable energy conversion technologies.

Metallic 1T Phase MoS2 Nanosheets Covalently Functionalized with BBD Molecules for Enhanced Supercapacitor Performances.

Metallic 1T phase molybdenum disulfide (MoS2) is among the most promising electrode materials for supercapacitors, but its capacitance and cyclability remain to be improved to meet the constantly increasing energy storage needs in portable electronics. In this study, we present a strategy, covalent functionalization, which achieves the improvement of capacitance of metallic 1T phase MoS2. Covalently functionalized by the modifier 4-bromobenzenediazonium tetrafluoroborate, the metallic MoS2 membrane exhibits increased interlayer spacing, slightly curled layered architecture, enhanced charge transfer, and improved adsorption capabilities toward electrolyte molecules and ions. Thanks to these boosted properties, the functionalized metallic MoS2 membrane exhibited excellent supercapacitor performances in a 0.5 M TBABF4 (acetonitrile as the solvent) electrolyte (with a specific capacitance of 135.67 F/cm3 at 1 A/g, more than three times that of the unfunctionalized metallic MoS2 membrane) and good stability, which can maintain a capacitance retention of 76.0% after 10 000 charge-discharge cycles.

Regulated Li+ Solvation via Competitive Coordination Mechanism of Organic Cations for High Voltage and Fast Charging Lithium Metal Batteries.

Li+ solvation exerted a decisive effect on electrolyte physicochemical properties. Suitable tuning for Li+ solvation enabled batteries to achieve unexpected performance. Here, we introduced inert organic cations to compete with Li+ for combining electrolyte molecules to modulate Li+ coordination in the electrolyte. The relevance between the number of cationic sites in organic cations and the competitive solvation ability was explored. The organic cations with multiple cationic sites attracted solvent molecules and anions away from Li+ to form new solvated shell, improving the Li+ transport kinetics and desolvation process in electrolyte while enhancing electrolyte oxidation tolerance. Moreover, electrostatic shielding provided by organic cations and anion-derived robust SEI promoted uniform and rapid Li+ deposition on Li electrodes. With the positive effect of organic cations, Li||LiCoO2 (LCO) batteries showed high specific capacity (136.46 mAh g-1) at high charge/discharge rate (10 C). Furthermore, Li||LCO batteries exhibited good capacity retention (70 % after 500 cycles) at 4.6 V charge cut-off voltage. This work provides fresh insights for the optimization of electrolytes and battery performance.

Regulated Li+ Solvation via Competitive Coordination Mechanism of Organic Cations for High Voltage and Fast Charging Lithium Metal Batteries

AbstractLi+ solvation exerted a decisive effect on electrolyte physicochemical properties. Suitable tuning for Li+ solvation enabled batteries to achieve unexpected performance. Here, we introduced inert organic cations to compete with Li+ for combining electrolyte molecules to modulate Li+ coordination in the electrolyte. The relevance between the number of cationic sites in organic cations and the competitive solvation ability was explored. The organic cations with multiple cationic sites attracted solvent molecules and anions away from Li+ to form new solvated shell, improving the Li+ transport kinetics and desolvation process in electrolyte while enhancing electrolyte oxidation tolerance. Moreover, electrostatic shielding provided by organic cations and anion‐derived robust SEI promoted uniform and rapid Li+ deposition on Li electrodes. With the positive effect of organic cations, Li||LiCoO2 (LCO) batteries showed high specific capacity (136.46 mAh g−1) at high charge/discharge rate (10 C). Furthermore, Li||LCO batteries exhibited good capacity retention (70 % after 500 cycles) at 4.6 V charge cut‐off voltage. This work provides fresh insights for the optimization of electrolytes and battery performance.

Unravelling multi-layered structure of native SEI on lithium metal electrode and various electrolytes using reactive molecular dynamics

Lithium metal batteries, directly utilizing lithium metal as an anode, are promising as new-generation energy storage devices, and the characteristics of the solid electrolyte interphase (SEI) layer are critical to battery operation. However, the roles of electrolyte compositions on the structure and thickness of the passivating SEI film at the atomistic level have been previously overlooked, resulting in poor understanding of SEI characteristics. In this study, the formation of the native SEI layer on lithium metal electrode and various electrolyte composition is scrutinised using ReaxFF molecular dynamics (MD) simulations. The study successfully identifies different layers of the SEI film using charge distribution as a tool. The decrease in lithium density and the increase in the charge states of oxidised lithium atoms contribute to the identification of an inner layer and a transition layer within the previously known interface layer, as well as the sparse layer. Additionally, different reaction schemes are observed through the analysis of ratio between consumed lithium atoms and electrolyte molecules. Furthermore, results show the lithium salt concentration effects in suppressing the growth of the SEI between the lithium anode and the liquid electrolyte, and inhibiting the formation of key SEI components. This work provides new insights into the nature of SEI surface chemistry and potentially facilitates the design of artificial SEI layers and optimal electrolyte solutions.

(Invited) Electrocatalysis at Modified Electrochemical Interfaces

Electrochemical energy storage and conversion technologies, which include fuel cells, electrolyzers, batteries, photoelectrochemical devices are at the forefront of the transition to a sustainable future. Although they have all been in use for more than half a century, they are far from reaching their full potential as defined by the laws of thermodynamics. Their performance rests almost entirely on the electrochemical interface - the boundary between the electronic conductor (electrode) and the ionic conductor (electrolyte). The desire of both phases to reduce the surface energy as well as the appearance of electrochemical potential across the interface can manifest itself as the formation of unique (near)surface atom arrangements (e.g. surface relaxation or reconstruction), as significant differences in electrode composition close to the surface (e.g. segregation profile), via substrate-adsorbate covalent and non-covalent interactions, via formation of a passive film as well as ordering of solvent and/or electrolyte molecules several nm away from the surface. This extremely complex and sensitive "interfacial bridge", is a consequence of inherent incompatibility of two materials, brought into contact, and is very hard to control. However, to control it means to control the energy efficiency, power density, durability and safety – the most important metrics of any energy conversion and storage device.In this presentation we will discuss, how the chemical nature of non-covalently and covalently [1,2] adsorbed species as well as thicker passive films and their morphology at the electrochemical interface affect the individual terms of the common rate equation [1], including the free energy of adsorbed intermediates and adsorbed spectators, mass transport, availability of active sites and electronic and ionic resistivity for common electrocatalytic reactions in acid and alkaline aqueous as well as in non-aqueous media on a plethora of metal electrodes (Pt, Ir, Au, Ni, Cu) as well as carbon. We will draw parallels between HER, OER, HOR and ORR in electrolyzers [1], fuel cells [2] and Li-ion batteries [3,4]. The interphase properties will be discussed through the lens of deviations of modified electrode properties from its intrinsic properties. Examples of artificially modified interfaces [5,6] will be given to demonstrate our ability to tailor their activity, stability and selectivity to our liking.[1] Strmcnik, D. Lopes, P.P., Genorio, B., et al. Design principles for hydrogen evolution reaction catalyst materials, Nano Energy, 29, 29-36 (2016)[2] Strmcnik, D., Uchimura, M., Wang, C. et al. Improving the hydrogen oxidation reaction rate by promotion of hydroxyl adsorption. Nature Chem 5, 300–306 (2013)[3] Strmcnik, D., Castelli, I.E., Connell, J.G. et al. Electrocatalytic transformation of HF impurity to H2 and LiF in lithium-ion batteries. Nat Catal 1, 255–262 (2018)[4] Martins, M., Haering, D., Connell, J.G., et al. Role of Catalytic Conversions of Ethylene Carbonate, Water, and HF in Forming the Solid-Electrolyte Interphase of Li-Ion BatteriesACS Catalysis 13, 9289-9301 (2023)[5] Zorko, M. Martins, P.F.B.D., Connell, J.G. et al. Improved Rate for the Oxygen Reduction Reaction in a Sulfuric Acid Electrolyte using a Pt(111) Surface Modified with Melamine, ACS Applied Materials & Interfaces 13, 3369-3376 (2021)[6] Strmcnik, D., Escudero-Escribano, M., Kodama, K. et al. Enhanced electrocatalysis of the oxygen reduction reaction based on patterning of platinum surfaces with cyanide. Nature Chem 2, 880–885 (2010)

(Invited) First-Principles Modeling of Degradation Mechanisms of the NaO2 Discharge Product in Na-O2 Battery Cells

The current climate crisis necessitates the development of improved electrochemical storage devices, such as aprotic alkali metal-O2 batteries (Li/Na-O2), which have greater than threefold higher thermodynamic gravimetric energy densities than Li-ion batteries. With a greater elemental abundance of sodium and low observed overpotential losses, Na-O2 batteries have become a focus of research interest. However, despite recent efforts, poor cell stability continues to plague Na-O2 cells, inhibiting commercial viability. A contributing factor to the poor cell stability is a degradation of the desired NaO2 discharge product at the cathode, resulting from undesirable interactions with the organic cell electrolyte under periods of cell idling where there is no charge transfer between the two electrodes. These undesirable interactions are hypothesized to degrade the NaO2 discharge product through two main pathways: (i) chemical transformation to hydrated sodium-oxygen species resulting from a chemical reaction with the electrolyte molecules and (ii) deleterious dissolution into the electrolyte. Thus far, practical solutions to improve stability have remained elusive, but elucidating molecular-level mechanistic details of these deleterious processes, using combined theory-driven and experimental approaches, could accelerate the discovery of practical design changes to overcome these stability bottlenecks.The goal of the present work is to couple computational and experimental studies to elucidate key molecular-level mechanistic insights of the undesirable interactions between the cell electrolyte and the surface of the NaO2 discharge product. We utilize periodic Density Functional Theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations to probe the two main NaO2 discharge product degradation mechanisms. To model the surface of the NaO2 discharge product, which in the case of high donor number electrolytes is deposited in a cubic confirmation, the cube faces and edges are represented as terrace and step facets, respectively, to capture the fact the undercoordinated cube edges could exhibit a different surface chemistry than the relatively pristine cube faces. At these two surface terminations, we elucidate the energetics that govern the degradation mechanisms of the NaO2 discharge product under cell idling conditions, as described below.To probe the chemical transformation of the NaO2 discharge product towards hydrated sodium-oxygen products, we elucidate the energetics of hydrogen abstractions from the electrolyte molecules to the NaO2 surface. With regards to the hydrogen coverage on the NaO2 surface, we find that there exists a plateau in the abstraction thermodynamics for the uptake of hydrogen, and at high coverages, the terrace NaO2 surface undergoes a series of favorable surface reconstructions towards sodium hydroxide species. Interestingly, we find that the free energy of activation for hydrogen abstraction from the electrolyte is not strongly influenced by the surface termination (terrace vs. step), as one would typically expect based on coordination number arguments. For the study of the deleterious dissolution of the NaO2 discharge product, we elucidate the energetics of elementary material loss mechanisms from the surface. We find that it is thermodynamically favorable for the surface to dissolute as individual NaO2 units, maintaining the NaO2 stoichiometry of the surface, with the thermodynamic surface penalty to undergo dissolution for the step facet being approximately ½ of the penalty for the pristine terrace facet. Further, we find the free energy of activation for dissolution of the step facet to be approximately ½ of the energy barrier of the terrace facet, suggesting that, unlike in the hydrogen abstraction process, the NaO2 cube edges drive the undesirable dissolution during idling. In closing, we comment how the current work lays the groundwork for future combined computational-experimental studies and how they may be used to propose practical design changes.

Operando FTIR Characterization of Interphases from Organosulfur Electrolytes in High Voltage Lithium-Ion Batteries

The widespread adoption of renewable energy storage technologies like electric vehicles and grid storage largely relies on the improvements of the energy density of the batteries inside those devices. Lithium-ion batteries (LIBs) are typically used for these applications due to their high energy density,[1] but the operating voltage of LIBs is limited by the electrochemical stability windows of the electrolyte. Resistive interphase layers form as a result of the breakdown of electrolyte molecules and limit LIB cycling stability. However, there is significant difficulty in the study and characterization of both the components and structure of the electrode-electrolyte interphases formed via electrolyte degradation.[2] Traditional characterization techniques provide information on what the interphase layers look like after cell disassembly, but sample preparations are difficult and destructive.[3] Therefore, it is crucial to develop in operando techniques to better understand the relationship between the interphase layers and battery performance.In this work, we develop a custom surface-enhanced infrared absorption spectroscopy in the attenuated total reflectance mode (ATR-SEIRAS) setup for in operando studies of the solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) in organosulfur electrolyte systems. Organosulfur molecules are potential components for high voltage LIBs due to their excellent performance.[4] We apply our custom ATR-SEIRAS setup to study ethyl methyl sulfone (EMS) containing electrolytes and propose possible reduction routes with the help of ex situ and postmortem characterization techniques. We study both SEI and CEI formed and correlate favorable interphase components with contributing molecules to identify important functional groups for novel molecular design. The work provides an opportunity to elevate our understanding of currently elusive electrochemical phenomena like the structure-reactivity relationships of SEI and CEI, and why certain sulfone systems outperform other formulations. Furthermore, it will provide molecular design principle for electrolyte systems in high performing and high voltage LIBs.References S. Chu, Y. Cui, and N. Liu, Nat. Mater., 16, 16–22 (2017).H. Wan, J. Xu, and C. Wang, Nat. Rev. Chem., 8, 30–44 (2024).A. Dopilka, Y. Gu, J. M. Larson, V. Zorba, and R. Kostecki, ACS Appl. Mater. Interfaces, 15, 6755–6767 (2023).M. A. Dato et al., Adv. Energy Mater., 2303794 (2024).

A Knowledge–Data Dual‐Driven Framework for Predicting the Molecular Properties of Rechargeable Battery Electrolytes

AbstractDeveloping rechargeable batteries that operate within a wide temperature range and possess high safety has become necessary with increasing demands. Rapid and accurate assessment of the melting points (MPs), boiling points (BPs), and flash points (FPs) of electrolyte molecules is essential for expediting battery development. Herein, we introduce Knowledge‐based electrolyte Property prediction Integration (KPI), a knowledge–data dual‐driven framework for molecular property prediction of electrolytes. Initially, the KPI collects molecular structures and properties, and then automatically organizes them into structured datasets. Subsequently, interpretable machine learning further explores the structure–property relationships of molecules from a microscopic perspective. Finally, by embedding the discovered knowledge into property prediction models, the KPI achieved very low mean absolute errors of 10.4, 4.6, and 4.8 K for MP, BP, and FP predictions, respectively. The KPI reached state‐of‐the‐art results in 18 out of 20 datasets. Utilizing molecular neighbor search and high‐throughput screening, 15 and 14 promising molecules, with and without Chemical Abstracts Service Registry Number, respectively, were predicted for wide‐temperature‐range and high‐safety batteries. The KPI not only accurately predicts molecular properties and deepens the understanding of structure–property relationships but also serves as an efficient framework for integrating artificial intelligence and domain knowledge.

A Knowledge-Data Dual-Driven Framework for Predicting the Molecular Properties of Rechargeable Battery Electrolytes.

Developing rechargeable batteries that operate within a wide temperature range and possess high safety has become necessary with increasing demands. Rapid and accurate assessment of the melting points (MPs), boiling points (BPs), and flash points (FPs) of electrolyte molecules is essential for expediting battery development. Herein, we introduce Knowledge-based electrolyte Property prediction Integration (KPI), a knowledge-data dual-driven framework for molecular property prediction of electrolytes. Initially, the KPI collects molecular structures and properties, and then automatically organizes them into structured datasets. Subsequently, interpretable machine learning further explores the structure-property relationships of molecules from a microscopic perspective. Finally, by embedding the discovered knowledge into property prediction models, the KPI achieved very low mean absolute errors of 10.4, 4.6, and 4.8 K for MP, BP, and FP predictions, respectively. The KPI reached state-of-the-art results in 18 out of 20 datasets. Utilizing molecular neighbor search and high-throughput screening, 15 and 14 promising molecules, with and without Chemical Abstracts Service Registry Number, respectively, were predicted for wide-temperature-range and high-safety batteries. The KPI not only accurately predicts molecular properties and deepens the understanding of structure-property relationships but also serves as an efficient framework for integrating artificial intelligence and domain knowledge.

Effects of SiO2 Particle Size in Soggy‐Sand Electrolyte on Electrochemical Performance of Zinc‐Ion Batteries

AbstractThe presence of free water molecules in the aqueous electrolyte leads to serious side reactions at the interface, easy dissolution of the cathode material, and uncontrolled growth of zinc dendrites in Zn‐ion batteries, which hinders their practical applications. Here, we propose a type of SiO2‐based soggy‐sand electrolyte (ZnSO4+MnSO4 electrolyte with SiO2, SiO2‐ZMSO4) and focus on the effect of the SiO2 nanoparticle size on the performance of soggy‐sand electrolyte. It is found that SiO2 with smaller nanoparticle size provides higher porosity, and the SiO2 network‐formed can effectively trap the free water in the electrolyte, which increases the ionic conductivity of electrolyte, widens working voltage window, and decreases the internal resistance of batteries. As a result, the Zn//MnO2 batteries with 20 nm SiO2‐based soggy‐sand electrolyte show stable cycling performance and rate capacities. The specific capacity of the battery can be maintained at 198.5 mAh g−1 after 1200 cycles at 1 A g−1 without capacity degradation. The specific capacity can be increased by 100 mAh g−1 even at a high rate of 5 A g−1. This study provides the rule of particle selection for the development of aqueous soggy‐sand electrolytes used in aqueous rechargeable batteries.

Is the oxygen plasma cleaning technique indicated for any electrochemical purpose?: The case of FTO electrodes

Fluorine-doped tin oxide (FTO) is among the most used transparent conductive oxides (TCOs) in phototovoltaic devices such as photoelectrochemical and solar cells. Preparation of films on these TCOs can be achieved by several deposition techniques including electrodeposition. Among the several cleaning and activation procedures before a thin film deposition there is the oxygen plasma treatment, which has been successfully applied on several kind of substrate materials. Surprisingly, the use of this step on TCOs previously to the electrodeposition of a film is not a usual practice. Here we present a detailed study on the consequences of oxygen plasma process over FTO electrodes that are subsequently employed in several electrochemical reactions of practical importance. Open circuit potential (OCP) measurements from oxygen plasma treated FTO have proven the resorption of ions and/or solvent molecules in aqueous electrolyte following a pseudo-second order kinetic. Electrochemical reactions were quite sensible to the oxygen plasma treatment, even under mild conditions. In all cases FTO become deactivated for such electrochemical processes independently of the plasma set up employed except for metal electrodeposition. Partial recovering of the electrochemical response of FTO in the ferri/ferro system after annealing at 450 °C explains why oxygen plasma process is worthy only for other deposition techniques such as spray pyrolysis where similar temperatures are employed. Electrochemical Impedance Spectroscopy (EIS) analysis revealed a decrease of the majority carrier density (ND). This is mainly attributed to the oxyanion implantation on oxygen vacancies sites during the plasma process thus explaining the loss of activation of FTO. Energy level diagrams reveal the decrease of degeneracy of FTO towards an n-type semiconducting SnO2 film which is also supported by ultraviolet photoelectron spectroscopy (UPS). A band gap energy dependence with the plasma conditions allowed to check the filling of oxygen vacancies on the FTO surface without discard the loss of fluorine. Anodic polarization in acid media proved the impossibility of oxygen vacancies restitution, being the dominating process the partial etching of FTO.

Free-Standing Poly(vinyl benzoquinone)/Reduced Graphene Oxide Composite Films as a Cathode for Lithium-Ion Batteries.

Quinones with a rapid reduction-oxidation rate are promising high-capacity cathodes for lithium-ion batteries. However, the high solubility of quinone molecules in polar organic electrolytes results in low cycle stability, while their low electric conductivity causes low utilization of electrode materials. In this article, a new p-benzoquinone derivative, poly(vinyl benzoquinone) (PVBQ), is designed and synthesized, and a solution-based method of preparing free-standing PVBQ/reduced graphene oxide (RGO) composite films is developed. PVBQ has a high theoretical specific capacity (400 mA h g-1) because of its low dead moiety mass. In the produced composite films, PVBQ nanoparticles are uniformly dispersed on RGO sheets, which endows the composite films with high electric conductivity and inhibits the dissolution of PVBQ through strong adsorption. As a result, the composite films show a high active material utilization, high practical specific capacity, and excellent cycling stability. PVBQ in the composite membrane containing 60.2 wt % RGO deliver 244 mA h g-1 capacity after 200 charge-discharge cycles at a current density of 300 mA g-1. At a current density of 1500 mA g-1, the reversible specific capacity is still 170 mA h g-1. This work provides a high-performance cathode material for lithium-ion batteries, and the molecular structure and electrode structure design ideas are also instructive for developing other organic electrode materials.

Organic molecular intercalation regulated hydrated vanadate cathodes with improved electrochemical properties and fast kinetics for aqueous zinc-ion batteries

Due to the large hydrated zinc ion radius resulting from the stable solvation structure with six water molecules in electrolyte, the interlayer spacing of most vanadium-based materials fails to meet the requirements for efficient insertion and extraction of Zn2+. Therefore, it is crucial to optimize and reconstruct the VO layer structure in order to achieve rapid and stable zinc storage. In this paper, composites of phenylalanine methyl ester (PM) inserted hydrated V2O5 (PMVO) are prepared using a one-step hydrothermal method. With the increase of PM insertion, the electrochemical properties initially exhibit enhancement followed by subsequent decline. Notably, PMVO-1.6 presents exceptional electrochemical performance, including a high capacity of 464 mAh g−1 at 0.1 A g−1, excellent rate capability with 220 mAh g−1 at 7 A g−1, and superior cycling stability with 97.5 % capacity retention after 1000 cycles at 4 A g−1. The incorporation of PM not only serves as stable structural pillars, but also reduces the solubilization of vanadium, facilitates the diffusion kinetics of hydrated zinc ions, and enhances the surface pseudo-capacitance effect.

Calcined Nickel Oxide Nanostructures at Different Temperatures Onto Graphite for Efficient Electro‐Oxidation of Ethylene Glycol in Basic Electrolyte

ABSTRACTFabricating a highly active and stable nanocatalyst material displays a great concern when constructing a commercially viable ethylene glycol (EG) fuel cell. Herein, nickel oxide nanostructures were grown onto graphite (NO/T) using coprecipitation and calcination protocol at different temperatures. Techniques for XRD, TEM, SEM, and EDX investigations were used to look into the produced crystal planes, shape, and elemental mapping of synthesized nickel oxide nanoparticles. Different NO/T nanocatalyst electroactivities were examined in order to oxidize EG molecules in basic electrolyte. The surface area values of calcined nanostructures at 200°C and 300°C were much higher than those measured at NO/T‐400 by 7.62 and 3.71 folds to explain their outstanding performance. Some kinetic information for varied NO/T nanocatalysts was derived including the electron transfer coefficient, rate constant, and surface coverage values. Electron transfer rate constants of 0.1946, 0.3734, 0.0113, and 0.0303 s−1 were calculated at NO/T‐200, NO/T‐300, NO/T‐400, and NO/T‐500, respectively. Increased oxidation current densities could be achieved when NO/T nanomaterials were subjected to lowered calcination temperatures. NO/T‐200 and NO/T‐300 nanocatalysts also displayed decreased Eonset for alcohol oxidation process by 20 and 41 mV in relation to that at NO/T‐400. Moreover, chronoamperometric experiments revealed the prevalence of the stable behavior during EG oxidation at these nanostructures, especially for calcined ones at 200°C and 300°C. Much reduced poisoning rates were measured at NO/T‐200 (0.171 s−1) and NO/T‐300 (0.067 s−1) when contrasted to that at NO/T‐500 (0.727 s−1). Increasing the alcohol and supporting electrolyte concentrations was beneficial in improving the charge transfer characteristics of NO/T nanocatalysts as demonstrated by EIS measurements. This study supports the promising activity of NiO nanoparticles onto graphite as anode materials for direct alcohol fuel cells.

Deep learning-assisted research on high-performance electrolyte for zinc-ion capacitors

Zinc-ion capacitors (ZICs) have garnered significant attention due to their ability to balance energy density and power density. The properties of electrolytes greatly influence the electrochemical performance of ZICs, and the oxidation potential (OP) of electrolytes can be used to determine the most suitable electrolyte for ZICs. However, traditional methods for exploring OP are time-consuming and inefficient, making it difficult to effectively determine the most suitable electrolyte for ZICs. Herein, we propose a machine learning-assisted method that combines deep learning with the traditional machine learning algorithm Gradient Boosting Regression (GBR), which we refer to as DeepGBR. This method can accurately predict the OP of electrolytes even when dealing with complex features and small datasets. Furthermore, with the assistance of deep learning, the accuracy of the predictions improves as the dataset size increases. We further validated the model with four common electrolyte molecules, finding that the predicted results are highly consistent with the theoretical values. The results show that acetonitrile has a high OP, which can achieve high energy density and long-cycle stability when used as an electrolyte solvent for ZICs. This work provides a certain reference for the database modeling strategy of electrolytes for electrochemical energy storage devices.

Investigation of the Activity and Stability of Manganese-Based Electrocatalysts for the Electrochemical Oxidation of Water and Small Organic Molecules in Acidic Electrolyte

Water electrolysis is a crucial process for hydrogen production, providing a clean and sustainable method for H2 production. Iridium-based catalysts are particularly effective in promoting the oxygen evolution reaction (OER) that takes place at the anode of electrolyzers. The unique properties of iridium make it well-suited for this purpose, but its high cost becomes a bottleneck in making water electrolysis economically viable on a large scale. Manganese-based electrocatalysts have emerged as promising candidates for the OER, mainly due to their earth abundance, low toxicity, and activity. It has been shown that manganese oxide can operate stably in acid, in a restricted potential window, where the formation of permanganate ions is avoided. Thus, for practical application, the stability must be improved, so a larger potential window can be employed. To address this challenge, some approaches have emerged from combining a catalytically active, but instable oxide, with the one that is stable, but inactive for the OER. In the presentation, we will show the results of activity, stability, and faradaic efficiency (FE) for O2 formation for water electro-oxidation on manganese oxide, and on manganese oxide combined with antimony, tin, titanium, niobium, and silicon oxide. The faradaic efficiencies, determined via EC-MS (Electrochemistry coupled to mass spectrometry) measurements revealed that manganese antimonate and pure manganese oxide have the highest values for O2 formation, with the former presenting higher stability at high overpotentials. We will discuss the obtained trends in stability and FEs for the other synthesized oxides. Additionally, for these two most efficient electrocatalysts, EC-MS measurements were conducted for the electrochemical oxidation of some small organic molecules, such as formic acid, methanol, ethanol, and ethylene glycol (electrochemical reforming for H2 production). The results showed that the selectivity for the electro-oxidation of water and/or of the organic molecule (monitoring the formation of CO2) strongly depends on the catalyst composition and on the number of carbon atoms of the molecule. We will further discuss, in the presentation, the factors that govern the selectivity and stability for each case. The obtained results of this study may be helpful for developing more efficient, selective and, mainly, more stable earth-abundant electrocatalysts for electrolyzers.

(Digital Presentation) Graphene as Barriers to Prevent Phosphoric Acid Leaching in High-Temperature PEMFCs

High-temperature PEMFCs running at 120-200℃ with the simplified water management has attracted more attention [1]. However, phosphoric acid molecules in polybenzimidazole membrane electrolyte (PA/PBI) are easily leaching to electrodes, which block pores of carbon fiber electrodes and impact gas transfer. Finally, the power density and durability of PEMFCs are extremely reduced [2].Graphene is a kind of two-dimensional (2D) structure of honeycomb lattice material and can block the penetration of almost all molecules and atoms, which is able to prevent PA molecules leaching as [3]. Our group has investigated a nitrogen-modified reduced graphene oxide (NrEGO) prepared by the electrochemical exfoliation, which has shown excellent performance in enhancing the activity and stability of catalysts [4]. Meanwhile, our previous research developed a single layer graphene loaded electrode. The power density of high-temperature PEMFCs is improved compared with commercial cells after accelerated stress test [5].Therefore, this work used NrEGO flakes as barriers to prevent phosphoric acid leaching to gas diffusion layer with lower Pt loading. In the present results, when the ratio of NrEGO and CB is 2 to 3 and the Pt loading is 0.25 mgPt/cm2, the cell improves 20% of the maximum power density and shows more stable with a decay of voltage by only 0.02 mV/h, which is quiet lower compared with that of 1.14 mV/h in commercial Pt/C.

Unraveling the Dynamics of Solid-Electrolyte Interphase (SEI) Formation on Lithium Metal: Insights from Multiscale Modeling

We need batteries to get the best out of renewable energies and other low-carbon energy sources, and the most promising path forward is to invest in high-energy-density battery technologies. In this regard, lithium metal is the best candidate for the anode electrode as it is the lightest metal on earth and has the lowest electrochemical potential (-3.04 V vs. SHE). However, the challenge to overcome for mass commercializing lithium-metal batteries (LMB) is stabilizing the solid electrolyte interphase that naturally grows at the electrode-electrolyte interface to avoid uncontrolled reactions leading to lithium depletion. Since the successful introduction of lithium-ion batteries (LIB), it has been known that tuning of the SEI composition and morphology is fundamental to prolong the battery life span; a well-engineered SEI layer simultaneously serves as an electron barrier and favors Li+ ion conduction across it, ensuring proper battery performance. However, the engineering of the SEI layer in LMB is more complex than its counterpart LIB batteries, given that lithium metal is overwhelmingly more reactive than graphite and the overall Li+ ion current across it is orders of magnitude higher. The up-to-date knowledge on the SEI morphology indicates that inorganic phases produced upon the decomposition of lithium salts present in the electrolyte tends to grow dominantly buried within the SEI layer, acting as an intermediate between the surviving lithium metal and the outermost organic SEI phase grown after decomposition of solvent molecules. The effect of electrolyte additives and diluents is to tweak the SEI composition. The narrative built after years of experimentation tells that proper battery functioning depends heavily on the ability of the incoming Li+ ions to desolve near the SEI outermost layer without triggering further side reactions, penetrate the inner SEI, and deposit in the anode as reduced lithium. However, the intricacies of the elementary reactions and the stage where the reduction takes place still fall beyond detailed comprehension, even though the development of in situ and operando analytical techniques has brought us a level of understanding on the subject that was unimaginable a few decades ago.In this talk, we discuss the instrumental impact that multiscale modeling techniques have played in clarifying the elementary steps of the SEI formation on pristine lithium metal, providing a comprehensive understanding of the precursors formed in the early stages of Solid-Electrolyte Interphase (SEI) growth. For instance, density functional theory (DFT) calculations have revealed that electrolyte diluents, such as TTE, previously considered inert to lithium metal, actively modify the liquid electrolyte solvation structure by weakly interacting with Li+ ions. Additionally, these diluents decompose against lithium metal, releasing fluoride ions and inundating the SEI layer with LiF. Similarly, DFT-based molecular dynamics (MD) techniques, including ab initio (AIMD) and reactive classical molecular dynamics methods (ReaxFF MD, among others), have facilitated a picoseconds (ps) scale observation of the temporal evolution of these SEI precursors, propelling a mechanistic understanding of the dynamics of the SEI formation; it is now recognized that there is an initial and rapid electrolyte decomposition occurring within the first tens of picoseconds after contact with lithium metal, preceding a longer-scale mass transfer segregation process leading to the formation of a myriad of organic and inorganic microphases within the SEI structure. However, the accessible time and space windows to MD methods fall within few hundred ps, leaving out the study of the morphological aspects of the SEI over extended cycling. In this sense, we discuss through kinetic Monte Carlo (kMC) calculations the evolution of the SEI formation on lithium metal and confirm the critical role that dislocations and grain boundaries play in ensuring proper lithium plating and mobility within the SEI layer over cycling. We confirm that bulk lithium diffusion within the inorganic SEI microphases, such as LiF and Li2O, is significantly lower than lithium mobility across LiF/Li2O interfaces. We also discuss the impact of electrolyte tunning on SEI morphology and provide insights into developing an SEI formation strategy based on the electrolyte molecules electrochemical stability and their relative contents of heteroatom species, such as F and O, to seed in the SEI composition and morphology, which we believe could have a significant impact on the development of stable LMB batteries.

Suitable Stereoscopic Configuration of Electrolyte Additive Enabling Highly Reversible and High-Rate Zn Anodes.

Electrolyte additive engineering is a crucial method for enhancing the performance of aqueous zinc-ion batteries (AZIBs). Recently, most research predominantly focuses on the role of functional groups in regulating electrolytes, often overlooking the impact of molecule stereoscopic configuration. Herein, two isomeric sugar alcohols, mannitol and sorbitol, are employed as electrolyte additives to investigate the impact of the stereoscopic configuration of additives on the ZnSO4 electrolyte. Experimental analysis and theoretical calculations reveal that the primary factor for improving Zn anode performance is the regulation of the solvation sheath by these additives. Among the isomers, mannitol exhibits stronger binding energies with Zn2+ ions and water molecules due to its more suitable stereoscopic configuration. These enhanced bindings allow mannitol to coordinate with Zn2+, contributing to solvation structure formation and reducing the active H2O molecules in the bulk electrolyte, resulting in suppressed parasitic reactions and inhibited dendritic growth. As a result, the zinc electrodes in mannitol-modified electrolyte exhibit excellent cycling stability of 1600 h at 1 mA cm-2 and 900 h at 10 mA cm-2, respectively. Hence, this study provides novel insights into the importance of suitable stereoscopic molecule configurations in the design of electrolyte additives for highly reversible and high-rate Zn anodes.