Low Electrolyte Concentrations Research Articles

A low concentration electrolyte additive for constructing solid-electrolyte interphase on a Zn metal anode for aqueous batteries.

Zn metal anodes in aqueous batteries experience inhomogeneous deposition and corrosion issues. Herein, we introduced, at a low concentration, dioxane (DX) as an electrolyte additive to stabilize a Zn anode. The oxygen sites of DX endowed it with a strong affinity for Zn and Zn2+, resulting in its adsorption onto the Zn electrode surface and its coordination with Zn2+ locally. The Zn2+-DX species exhibited a decreased lowest unoccupied molecular orbital energy level relative to those of water-involved components. The DX additive not only inhibited side reactions but also generated a stable solid-electrolyte interphase on the Zn electrode, ensuring a uniform Zn deposition. As a result of including the additive, the cycle life of the Zn symmetric cell was extended from 99 h to 2100 h, and the coulombic efficiency in Zn//Cu cell reached 99.5%.

Revealing the enhancement of Li plating/stripping efficiency in TEGDME-based low-concentration electrolytes for anode-free lithium metal batteries.

Anode-free lithium metal batteries (AFLMBs) have attracted great attention owing to their higher energy density compared to conventional lithium metal batteries. Unfortunately, AFLMBs still suffer from poor Coulombic efficiency (CE) due to severe dendrite growth and the unstable solid-electrolyte interface (SEI) at the anode. Therefore, we explored the effect of concentration and LiNO3 additive on the SEI layer and on Li plating/stripping efficiency using a low-concentration tetraethylene glycol dimethyl ether (TEGDME)-based electrolyte in an AFLMB anode half-cell configuration. It was found that the formation of protective Li2O-based SEI layers when blocking the oxidative subsequent SEI formation (called "OSS") above 2.2 V vs. Li/Li+ improved Li plating/stripping stability, while the LiNO3 additive suppressed the oxidation of Li2O into Li2O2 and sustained the existence of Li2O without blocking OSS, therefore improving CE performance. Although increasing the concentration (from 0.4 M to 2.0 M) did not have a major effect, the 2.0 M electrolyte with LiNO3 additive shifted the dominant SEI species from Li2O to LiF, further enhancing CE performance.

Developing diluted low-concentration electrolyte with a high anion-to-solvent ratio for high-voltage lithium metal batteries

The most positive surface potential (ESPmax) of a diluent can be taken as a descriptor for its anti-solvating power, which guides the rational design of diluted low-concentration electrolyte (DLCE) with a high anion-to-solvent ratio.

Nanoarchitectonics for a long-life and robust Na-ion battery at low temperature with Prussian blue cathode and low-concentration electrolyte

Na-ion batteries are considered as promising battery systems for large-scale energy storage. Although Na-ion batteries exhibit enhanced low-temperature cycling performance compared with lithium-ion batteries, there is still a great challenge to overcome for practical low-temperature applications. In this work, we propose a low-performance Na-ion battery composed of FeNi co-doped Mn-based Prussian cathode (FeNi-MnHCF) and a low-concentration electrolyte (0.5 mol L−1) containing a small amount of 2,2,2-trifluoroethyl acetate (ETFA, 1 wt%). The introduction of ETFA could decrease the viscosity, increase ionic conductivity and change the solvation structure of the electrolyte at low temperature. ETFA could also participate in constructing a uniform, stable, and Na-ion conductive CEI layer, enabling rapid Na-ion transport and effective protection of FeNi-MnHCF. The cells with the ETFA-contained electrolyte and FeNi-MnHCF cathode exhibit excellent rate capability and long cycle life at low temperature. When being cycled at −20 °C, the cell with ETFA could retain 92.1 % of the capacity after 1120 cycles at 1 C. The cell could also show stable cycling after overcharge to 4.8 V or overdischarge to 1.2 V at −20 °C. This work sheds light on the design of long-life and robust Na-ion batteries for sustainable energy storage at low temperature.

Effects of electrolyte type and concentration on the anodic oxidation of 4H-SiC (0001) in slurryless electrochemical mechanical polishing

Slurryless electrochemical mechanical polishing (ECMP) is a promising polishing method for SiC wafers. To achieve a high polishing efficiency, low surface roughness, low cost, and low environmental load, the effects of the electrolyte type and concentration on the anodic oxidation and ECMP of the 4H-SiC (0001) surface were investigated. It is confirmed that the anodic oxidation rate is mainly affected by the conductivity but not the type of electrolyte, and the electric conductivity affects the oxidation current that determines the anodic oxidation rate and performance. The anodic oxidation rate of the SiC surface was restricted by the conductivity at low electrolyte concentrations, and the anodic oxidation rate increased with increasing electrolyte concentration in this stage. The anodic oxidation rate decreased with increasing electrolyte concentration after the conductivity exceeded ∼0.1 S/m, owing to the increasing resistance of the generated oxide layer. Overall, the anodic oxidation uniformity of the SiC surface increased with increasing electrolyte concentration owing to the increasing anodic oxidation current density. The changes in material removal rate of ECMP with increasing electrolyte concentration were consistent with those of the anodic oxidation rate, while the surface roughness obtained by ECMP always decreased with increasing electrolyte concentration. This study provides a new way to improve the performance of slurryless ECMP.

Multifunctional Acetamide Additive Combined with LiNO3 Co-Assists Low-Concentration Electrolyte Interfacial Stability for Lithium Metal Batteries.

Lithium metal batteries (LMBs) are expected to upgrade their energy density to meet the growing battery market demand; however, intractable lithium dendrites and prominent electrode-electrolyte interface problems have been the stumbling block to their practical applications. Electrolytes play a crucial role in LMBs and are directly involved in the establishment of the electrode-electrolyte interface. In particular, low-concentration electrolytes (LCEs) can significantly save electrolyte costs, but the interface issue is more noteworthy. Here, multifunctional acetamide (N-methyl-N-(trimethylsilyl)-trifluoroacetamide, MTA) and lithium nitrate (LiNO3) additives were introduced together to enhance the performance of LMBs in LCEs. The MTA additive effectively removes the trace water and corrosive HF from the electrolyte, thus suppressing lithium salt decomposition and enhancing the stability of LCEs. Moreover, the MTA additive can construct an inorganic-rich interphase layer on the cathode/anode surface to protect the electrode. Especially, MTA can cooperate with LiNO3 additive to suppress lithium dendrites and reduce interfacial impedance, thus effectively enhancing lithium metal anode stability. Benefiting from the introduction of MTA and LiNO3 additives in the LCEs, the Li||NMC811 metal battery still has a capacity of 110 mA h g-1 after 500 cycles at room temperature, while the reference batteries have failed. The rate capacity and high temperature (50 °C) performance of the Li||NCM811 batteries have also been significantly improved. Significantly, this research explores a cost-effective method of using multifunctional additives to enhance LMBs' stability in LCEs.

Low Concentration Electrolyte Enabling Anti‐Clustering of Lithium Polysulfides and 3D‐Growth of Li2S for Low Temperature Li–S Conversion Chemistry

AbstractThe development of low‐temperature lithium–sulfur batteries (LSB) has been suppressed by rather poor sulfur utilization and cycle performance, caused by planar Li2S growth, hindered lithium polysulfides (LiPSs) transformation, and poor stability of the anode. Recently, low‐concentration electrolytes (LCE) have been employed as promising solutions to solve the above issues. However, aggregation and deposition behavior of polysulfides have been rarely studied. In this work, by comparing the performance of 0.1 and 1 m LiFSI electrolytes, LCEs are proven beneficial for low‐temperature LSBs via new fundamental insights. According to growth pattern analyses by both morphology observation and theoretical models, Li2S nucleation in LCEs switch into progressive mode with less initial nuclei, which favors the vertical growth of Li2S, resulting in a more complete lithium–sulfur conversion reaction under cold conditions. Through visual experiments, computational simulation, and progressive electrochemical impedance spectroscopy, the ability of LCEs to suppress LiPSs clustering is supported and this anti‐clustering ability effectively enhances the Li–S conversion reaction kinetics. Moreover, in LCEs a protective SEI with LiF and Li2S/Li2S2 is likely to form on and stabilize the anode. As a whole, the boosting effect and the mechanism of LCEs enlighten future designs on low‐temperature electrolytes for high‐performance cryogenic LSBs.

Three-phase fluidized bed electrochemical reactor for the scalable generation of hydrogen peroxide at enzyme compatible conditions

Enzymes, as green biocatalysts, open new and selective syntheses routes for more efficient and direct process steps with minimal by-products. An innovative approach is the combination of an enzymatic reaction with an electrochemical reaction to provide otherwise expensive co-factors for enzymes electrochemically. However, there is a lack of scalable reactor designs with high volume specific electrode surfaces that are required to achieve competitive space time yields for these electro-enzymatic syntheses. Here, we show for the first time a three-phase fluidized bed electrochemical reactor for co-factor generation that allows in-situ delivery of educts for electro-enzymatic syntheses. The performance of the fluidized bed electrode consisting of highly conductive graphite particles, was characterized for the electrochemical generation of H2O2, the co-factor for e.g. industrially relevant hydroxylation reactions applying peroxygenases, via oxygen reduction. The achieved space time yields range up to 5.15 ± 0.27 g/(L∙d) for batch and 10.47 ± 0.73 g/(L∙d) for continuous operation, while reaching current efficiencies of up to 57.0 ± 8.2 %. As the results were obtained at neutral pH and at low electrolyte concentrations the fluidized bed electrode is especially suitable for integrated systems combining enzymatic and electrochemical reactions in one reaction chamber. By this, we successfully developed a scalable particle electrode reactor for electro-enzymatic synthesis, which takes advantage of the excellent mixing and mass transfer properties of fluidized beds. This reactor allows for controllable co-factor generation through various factors such as pH in the counter electrode, supplied air flow, and applied potential.

Design criteria for selective nanofluidic ion-exchange membranes

Polymeric ion-exchange membranes (IEMs) are key to many electrochemical processes, but their intrinsic selectivity limitations restrict scale-up possibilities. Nanofluidic IEMs, based on inorganic rigid materials and charged nanopores, offer a promising alternative. We present design criteria for selective nanofluidic membranes. We used commercial anodized aluminium oxide (AAO) membranes with varying pore sizes to measure permselectivity between different KCl concentrations. Our experiments reveal that membranes with 10-nm pores have permselectivities above 90%, comparable to those of polymeric IEMs, up to electrolyte concentrations of 0.15 vs. 0.75 M. To our knowledge, this is the highest reported ion selectivity for nanofluidic IEMs. Conversely, asymmetric AAO membranes featuring a thin selective layer, exhibited low permselectivity. We explored the influence of other parameters through simulations using the space-charge model. Our numerical results indicate that pore size and surface potential are the most sensitive parameters for increasing selectivity. Additionally, pore length has a minimum requirement for good performance although increasing it beyond the μm scale yields no significant result. This study highlights nanofluidic IEMs as a promising alternative to polymeric IEMs and their capability to improve performance of many electrochemical processes, especially those involving low electrolyte concentrations on at least one membrane side.

Enrichment of surface charge contributes to the stability of surface nanobubbles

Surface nanobubbles are spontaneously formed at the interface between hydrophobic surfaces and aqueous solutions, which show extraordinarily longer lifetime than that was predicted by the classical thermodynamics model. In the present work, by using a surface plasmon resonance microscopy (SPRM) to quantitatively measure the dissolution kinetics of individual surface nanobubbles in real time, we explored the effects of ionic strength and pH value on the dissolution rates (lifetime) of nanobubbles. The results revealed that nanobubbles could exist stably for a long time in low-concentration electrolyte solutions or high-concentration non-electrolyte solutions, while they dissolved quickly in high-concentration electrolyte solutions. With the increase of ionic strength, the dissolution rates were accelerated by 2–3 orders of magnitude, and thus the lifespan of these surface nanobubbles was significantly shortened. In addition to ionic strength, it was further found that, with the increase of acidity or alkalinity of the solution, the dissolution rates of the surface nanobubbles were faster than that in neutral solution. These results demonstrated that the interfacial charge enrichment significantly contributed to the extraordinary stability of the surface nanobubbles.

Low-temperature anode-free potassium metal batteries

In contrast to conventional batteries, anode-free configurations can extend cell-level energy densities closer to the theoretical limit. However, realizing alkali metal plating/stripping on a bare current collector with high reversibility is challenging, especially at low temperature, as an unstable solid-electrolyte interphase and uncontrolled dendrite growth occur more easily. Here, a low-temperature anode-free potassium (K) metal non-aqueous battery is reported. By introducing Si-O-based additives, namely polydimethylsiloxane, in a weak-solvation low-concentration electrolyte of 0.4 M potassium hexafluorophosphate in 1,2-dimethoxyethane, the in situ formed potassiophilic interface enables uniform K deposition, and offers K||Cu cells with an average K plating/stripping Coulombic efficiency of 99.80% at −40 °C. Consequently, anode-free Cu||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride full batteries achieve stable cycling with a high specific energy of 152 Wh kg−1 based on the total mass of the negative and positive electrodes at 0.2 C (26 mA g−1) charge/discharge and −40 °C.

Fabrication of lead telluride quantum dots and their application in photoelectrochemical-type photodetectors

IV-VI semiconductors have been extensively applied in photo-electrochemical (PEC)-type photodetectors. However, electrolytes with relatively high concentrations have been addressed which could induce electrochemical reactions during the measurement and result in a performance decrement. In this work, lead telluride quantum dots (PbTe QDs) with uniform size distribution are fabricated for PEC-type photodetectors and their performance is systematically investigated in electrolytes with concentrations as low as 10−4 mol/L. As revealed, the PbTe QD-based photodetectors show apparent photo-response with excellent stability in 1000 cycles (decrement of 0.018 % per cycle). In addition, the as-fabricated photodetectors show a broadband response to light in a region of 350–700 nm. These results are well supported by density functional theory calculations based on structural features and electronic and optical properties. Hence, we envisage that this work paves the way to fabricate high-performance photodetectors in relatively low-concentration electrolytes, which also can extend their applications to other optoelectronic devices.

Intercalation pseudocapacitance mechanism realizes high-performance cathode for aqueous potassium ion batteries

Aqueous potassium-ion batteries have garnered significant interest due to their eco-friendly characteristics and affordability. However, The suboptimal lifetime and restricted energy density of electrode materials present considerable obstacles to the advancement of aqueous potassium ion batteries. In this paper, we report a Ce doped MnO2 material (Ce-MnO2). Ce-MnO2 with large lattice spacing and abundant oxygen defects successfully triggered the intercalation pseudocapacitance behavior in aqueous potassium ion batteries. The intercalation pseudocapacitance mechanism gives MnO2 good capacity and enhanced stability. The Ce-MnO2 demonstrates a high discharge capacity of 120 mAh g−1 at 1 A g−1 with a low concentration electrolyte. It also has a capacity retention rate of 82.5% at 2000 cycles at 5 A g−1. The application of the intercalation pseudocapacitance mechanism offers a new approach to addressing the challenges associated with aqueous potassium-ion batteries.

Fine-tuning formulation and biological interaction of doxorubicin-loaded polymeric nanoparticles via electrolyte concentration modulation

Doxorubicin (DOX) is amongst the most widely used chemotherapeutic drugs against various cancers. However, its controlled biodistribution to the tumor site at the required pharmacokinetics profile remains challenging. In this work, a vast study of formulation parameters has been performed to control doxorubicin loading into polymeric nanoparticles in physiological conditions. Water-in-oil-in-water (W1/O/W2) template emulsions have been formulated, including doxorubicin in the internal water phase. Specifically, the system [Doxorubicin in aqueous solution (W1) / Pluronic F-127 (S) and PLGA in ethyl acetate (O)], [Polysorbate 80 (S) in water solution], using phosphate buffer on both aqueous phases at different electrolyte concentrations has been established. The first W1/O nano-emulsion was formed by high-speed homogenization, and the second O/W2 nano-emulsion was formed by the phase inversion composition method, a low-energy emulsification appropriated for pharmaceutical compounds. Although many previous studies had already used double emulsions for DOX encapsulation in nanofluids, here, for the first time, the salt concentration of the water phases has been varied to control the resulting doxorubicin and nanoparticle properties. The addition of high concentrations of electrolytes in both aqueous phases decreases the solubility and dissolution rates of the drug, leading to a high degree of DOX dimerization. This phenomenon significantly impacts the internalization and subcellular localization. Facilitating drug nuclear accumulation is of vital interest, and this is primarily achieved when doxorubicin is incorporated into nanoparticles formulated with PBS at low electrolyte concentrations (2.5 mM), which exhibit exceptional internalization properties. Thus, it has been demonstrated that doxorubicin loading in polymeric nanoparticles can be tuned by only varying salt concentrations of template W1/O/W2 emulsions. Consequently, our results show the adequacy of the double nano-emulsion templating for the generation of non-toxic DOX-loaded polymeric nanoparticles with different physicochemical properties and interaction with the cell surface that would allow their use for various anticancer therapies.

Electro-Oxidative Polymerization of Aromatic Monomers without an Electric Power Supply

Electrochemistry is a powerful tool for organic synthesis based on electron transfer-driven reactions at the substrate/electrode interface. The use of electricity for synthetic reactions without the need for hazardous chemical oxidants and reductants is recognized as a green and sustainable approach. We have recently developed a split bipolar electrode (s-BPE) system [1], in which the redox reactions can be driven in a low electrolyte concentration, with batch [2,3] and flow [4] cells. Herein, we report a novel s-BPE system for organic electrosynthesis driven under a streaming potential condition with a pressure flow. As a proof-of-concept study on electrosynthesis without an electric power supply, electrochemical oxidative polymerization of aromatic monomers such as pyrrole successfully yielded the corresponding polymer films on an electrode surface at the upstream, which acted as an anode [5].[1] Shida, N.; Zhou, Y.; Inagi, S. Chem. Res. 2019, 52, 2598-2608.[2] Miyamoto, K.; Nishiyama, H.; Tomita, I.; Inagi, S. ChemElectroChem 2019, 6, 97-100.[3] Shida, N.; Villani, E.; Sanuki, M.; Miyamoto, K.; Gotou, A.; Isogai, I.; Yamauchi, A.; Fuchigami, T.; Tomita, I.; Inagi, S. Electrochemistry, 2021, 89, 476-479.[4] Sakagami, H.; Takenaka, H.; Iwai, S.; Shida, N.; Villani, E.; Gotou, A.; Isogai, T.; Yamauchi, A.; Kishikawa, Y.; Fuchigami, T.; Tomita, I.; Inagi, S. ChemElectroChem, 2022, 9, e202200084[5] Iwai, S.; Suzuki, T.; Sakagami, H. Miyamoto, K.; Chen, Z.; Konishi, M.; Villani, E.; Shida, N.; Tomita, I.; Inagi, S. Commun. Chem., 2022, 5, 66.

Modeling the Local Environment inside a GDE Pore for CO2 Electrochemical Reduction

Porous Gas Diffusion Electrodes (GDE) have gained a lot of attention in recent years for their ability to overcome the solubility and mass transfer limitations of a planar electrode assembly in CO2 electrochemical reduction (CO2ER) systems. In this work, we present a continuum scale modeling technique based on a set of size-modified Poisson-Nernst-Planck (SMPNP) equations to accurately account for the local environment including the Electric Double Layer (EDL) inside a catalytic nanopore. Most GDE models for CO2ER ignore the EDL or are limited in their applicability at relevant applied potentials due to numerical instability. The local conditions found inside an EDL heavily influence the charge transfer reactions and thus the productivity of desired CO2ER products. Our SMPNP model is able to solve for the concentration and electric field profiles at practical cathodic potentials. We highlight the variation of the predicted CO2 concentration which is often assumed to remain uniform along the radii of the catalytic pores even at high applied potentials. The predicted pH profile also varies significantly along the pore radius, influencing both the CO3 2- balance and the charge transfer reactions. Geometrical parameters such as the diameter and length of the pore, influence the electric field and can potentially be used as control parameters for increasing the selectivity of desired products. We also discuss the implications of double layer overlap as a consequence of small pore radii and low electrolyte concentration. Overall, using the SMPNP model we gain insights into key performance-controlling parameters inside a catalytic nanopore. Furthermore, the model can be used to inform boundary conditions in larger-scale GDE models.

Clarification of the Reaction Mechanism of the Photoassisted Anodic Oxidation of SiC in a Newly Developed Inverted Rotating Disk Electrode Cell Setup

Due to the distinctive chemical and physical properties of silicon carbide (SiC), interest in the material as a substrate for semiconductor industry has risen significantly during the past two decades. As a wide bandgap semiconductor SiC is known to be highly chemically inert. Still, under specific conditions SiC takes part in a number of electrochemical reactions that lead to a rapid oxidation of the surface. The goal of this work is to understand the fundamental factors driving this process for n-type SiC crystals in aqueous electrolytes.In alkaline solutions, the photoelectrochemical behaviour of n-type SiC is determined by two partial reactions (oxidation/dissolution) 1 :(1a) SiC + 6h+ (hν) + 6OH- → SiO2 + CO + 3H2O(1b) SiC + 8h+ (hν) + 8OH- → SiO2 + CO2 + 4H2O(2) SiO2 + 2OH- → [Si(OH)2O2]2- For the investigation of such photoassisted or photoelectrochemical reaction mechanisms involving mass transfer, we specifically developed a new inverted rotating disk electrode (IRDE) cell setup 2 that allows to control the most essential experimental parameters (i.e. potential, diffusion conditions and light intensity).In this setup, rotation of the disk electrode is achieved by magnetic coupling between a driver magnet (i.e. a magnetic stirrer) and the follower magnet included in the sample holder. The cell allows a homogeneous illumination and removal of gaseous reaction products, while still providing leak tightness. The surface of the semiconductor electrode is illuminated with UV light (λ = 365 nm) from a high-power LED. The distance between light source and sample is minimized to achieve maximum surface illumination of the sample.To investigate mass transport phenomena, electrolytes with relatively low solubility of SiO2 are preferable. Therefore, we used potassium hydroxide solutions in a concentration range where mass transport of hydroxide ions plays a major role.Performing cyclic voltammetry in this newly developed IRDE cell allows to distinguish different reaction regimes that are either limited by mass transport, photon flux or hole transport. For low light intensities (either through a large distance between the sample and the LED or through low driving currents through the LED) the number of photon-induced holes is limiting. At low electrolyte concentrations, the transport of hydroxyl ions and the dissolution of the oxidation products determine the reaction rate. At low potentials, hole transport limits the overall current flow. Each of these reaction regimes was studied individually to conduct a potential reaction mechanism.[1] D. H. van Dorp und J. J. Kelly, „Photoelectrochemistry of 4H–SiC in KOH solutions,“ Journal of Electroanalytical Chemistry, Bd. 599, Nr. 2, pp. 260-266, 2007.[2] K. Mairhofer, P. Mayr, S. Radl, M. Nelhiebel, S. Larisegger, G. Fafilek, „An Inherently Leakage-Free Inverted Rotating Disk Electrode Setup“, 2022. Figure 1

(Invited) Aemion+® AEM Water Electrolysis with Excellent Iridium-Free Performance and Industrially Relevant Stability in Hot, Caustic Electrolyte

Hydrogen has a unique ability to maximize the utility of and enable new business models for intermittent renewable deployment. It can be stored cost-effectively in geological storage, transported between regions to suit geographic needs and bridge Dunkelflautes. Global electrolysis capacity must increase from the current <2 GW to 850 GW in 2030 (IEA Net Zero 2050) and in excess of 3500 GW in 2050 to enable this transition.Both traditional Alkaline (AWE) and proton-exchange membrane electrolyzers (PEMWE) are mature technologies that are anticipated to split the overall market share. However, each of these technologies face fundamental challenges:AWE operate at low current density, requiring large and difficult to transport systems, require high concentration electrolytes (e.g. 30 wt% KOH) to conduct hydroxides and ensure low gas solubilities for safety, which necessitates the use of expensive and difficult to machine high-nickel steels, especially in advanced, pressurized designs. Additionally, the porous nature of the electrode separator (e.g. Zirfon) compromises the desired dynamic load for pairing with intermittent renewables.PEMWE use a proton-conductive membrane to enable high current densities, dynamic loads, and differential hydrogen pressures, however, the most efficient operation requires iridium catalyst, which presents a near-term challenges with scalability, together with Ti and PGM structural elements that further impede cost-effectiveness.Alkaline anion-exchange water electrolyzers (AEMWE) address both of these challenges by operating with a cohesive, hydroxide-transporting membrane together with alkaline electrolyte to enable high efficiency, high current density operation, without iridium electrocatalysts or other scarce or expensive components. The realization of capital cost-effectiveness, dynamic load, and compact systems in one technology enables the most cost-effective green hydrogen and represents a step-change in the trajectory towards the DOE Hydrogen Shot target of $1/kg.The instability of alkaline anion exchange membrane chemistries based on quaternary amines or pendant imidazolium groups in relevant temperatures and alkalinities to industrial operations have historically resulted in untenable compromises and too-short lifetimes for industrial-scale deployment. Ionomr's Aemion+® AF2-AWP8-75-X and AF3-HWK9-75-X membranes are based on a sterically-protected imidazolium chemistries that are chemically robust (e.g. 6 months, 1 M, 80 °C without alteration to chemical or mechanical properties), and additionally exhibit low swelling to provide mechanical integrity to electrodes and enable operation in low concentration electrolytes. These membranes are an enabling technology for long-duration AEM water electrolysis.This talk highlights how Ionomr's Aemion+® membranes demonstrate target performances (e.g. >2 A/cm² at 2 V) with non-PGM OER catalysts with no apparent losses to 1000 hours operation across several configurations at ≥70 °C and 1 M KOH operation, and several longer lifetime demonstrations including 1 year durability using AWE electrodes and >6 months including hydrogen crossover measurement. This talk further highlights the potential for the three-dimensionality of electrodes in alkaline AEMWE and the necessary processing and operational requirements to create reproducible and stable GDEs with catalyst ink-based deposition techniques. Figure 1

Effect of hydrodynamic slip on thermoelectric response in negatively-charged nanofluidic channels

Nanofluidic thermoelectrics has attracted significant interest recently due to its potential for low-grade heat recovery. However, the impact of hydrodynamic slippage on power generation performance in nanofluidic channels has generally been ignored in previous studies, although slip velocity boundary conditions are relevant at the nanoscale. To fill this research gap, this study conducted two-dimensional (2D) numerical simulations based on non-isothermal Poisson, Nernst–Planck, Navier–Stokes, and energy equations to investigate the thermoelectric response, including Seebeck coefficient, thermoelectric current, power factor, and normalized maximum power density, within a nanochannel with slippage at the channel walls. The simulations considered three thermal-driven ion transport mechanisms: temperature-dependent ion electrophoretic mobility (TDIEM), Soret-type ion thermodiffusion, and thermoosmosis. The results showed that TDIEM and thermoosmosis primarily dominate the thermoelectric response of electrolyte confined in slip nanochannels in the presence of the overlapping electrical double layer. The study also found that the impact of access resistance on the thermoelectric response must be considered. The slip-enhancement of the Seebeck coefficient, i.e., the thermoelectric voltage at open-circuit condition, is not significant due to the increase in surface conductivity caused by slip-amplified electroosmosis, especially at low electrolyte concentrations. However, slip-amplified thermoosmosis greatly enhances the thermoelectric current at short-circuit condition, in the absence of the access resistance effect, leading to a significant improvement in the performance of ionic thermoelectricity in nanochannels with hydrodynamic slippage. At a moderate slip length ranging from 10 to 50 nm, it was found that the normalized maximum power density in a 2 nm nanochannel exceeded 10 mW K−2 m−2, even under a small temperature difference of 10 K, which is one order of magnitude higher than the typical thermionic capacitors and thermocells. Overall, this study provides valuable insights into developing efficient nanofluidic-based thermoelectric generators for low-grade heat energy harvesting by highlighting the importance of considering the effect of hydrodynamic slippage.

Three-dimensional electrodes in hybrid electrolytes for high-loading and long-lasting calcium-ion batteries

Aqueous calcium-ion batteries (CIBs) exhibit a reliable long-term cycling and rate performance, but they have a low energy density owing to the narrow electrochemical stability window (ESW) of aqueous electrolytes. Highly concentrated water-in-salt electrolytes offer enhanced stability by limiting the number of free water molecules present within the system. However, CIB electrolytes still suffer from low conductivity and high viscosity due to the high concentration of calcium salt. Hence, to resolve this problem, a series of hybrid aqueous/organic calcium electrolytes were formulated to improve the ESW and long-term reversibility while maintaining a low electrolyte concentration. The best hybrid-electrolyte candidate, which had a calcium perchlorate/water/acetonitrile molar ratio of 1.0:4.0:4.8 (i.e., Ca(ClO4)2/(H2O)4.0(AN)4.8), exhibited a wide ESW (≈3.0 V) and a facile insertion of calcium ions into Prussian green host materials, leading to an impressive 90% capacity retention after 1000 cycles. Nickel foam (NF) was also employed as a cathode current collector to investigate the feasibility of the drop-coated three-dimensional electrodes. Owing to its high-porosity architecture, the NF substrate could accommodate for four to eight times higher mass loading than traditional foil-type collectors, resulting in full cells with much higher energy densities.