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In this study, the effect of halide anions on the selectivity of the CO2 reduction reaction to CO was investigated in choline‐based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO2RR was studied using silver (Ag) and gold (Au) electrodes in a compact H‐cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride‐containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CO2RR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl− ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion‐induced surface restructuring of Ag and Au electrodes during CO2RR, and its consequences on the reduction performance on such surfaces in non‐aqueous electrolytes. [ABSTRACT FROM AUTHOR]

Ammonia has garnered recognition as a zero-carbon fuel due to its high-density hydrogen storage capacity and its convenience for storage and transportation. To address the challenges associated with the direct usage of ammonia, the development of NH3-to-H2 conversion technologies has emerged as a promising and effective approach. Herein, we present for the first time that crystallized Sm2O3−x electrodes demonstrate high and stable electrocatalytic activities, including N2 evolution rate and Faradaic efficiency, for ammonia electrolysis in a non-aqueous electrolyte. It was observed that Sm2+ ions in samarium oxide play an indispensable role in the ammonia electrooxidation reaction on the anodes. Furthermore, the mechanism of ammonia electrooxidation has also been elucidated, laying the foundation for a better understanding of the relationship between local structure and electrochemical properties in order to facilitate research on Pt-free electrocatalysts for the electrolysis of ammonia into H2. [ABSTRACT FROM AUTHOR]

Strong interaction between positively charged Mn2+ ions and solvent molecules impedes manganese plating process, enabling previous manganese metal batteries non-rechargeable. Now, an innovative halogen-mediated strategy is revealed effective to make manganese metal batteries highly reversible.

A detailed investigation addressing the effects of functionalizing conjugated polymers with oligo(ethylene glycol) (EGn) sidechains on the performance and polymer‐electrolyte compatibility of electrochromic devices (ECDs) is reported. The electrochemistry for a series of donor‐acceptor copolymers having near‐infrared (NIR)‐optical absorption, where the donor fragment is 3,4‐ethylenedioxythiophene (EDOT) or an EGn functionalized bithiophene (g2T) and the acceptor fragment is diketopyrrolopyrrole (DPP) functionalized with branched alkyl or EGn sidechains, is extensively probed. ECDs are next fabricated and it is found that EGn sidechain incorporation must be finely balanced to promote polymer‐electrolyte compatibility and provide efficient ion exchange. Proper electrolyte‐cation pairing and polymer structural tuning affords a 2x increase in optical contrast (from 12% to 24%) and >60x reduction in switching time (from 20 to 0.3 s). Atomic force microscopy (AFM)/grazing incidence wide‐angle X‐ray scattering (GIWAXS) characterization of the polymer film morphology/microstructure reveals that an over‐abundance of EGn sidechains generates large polymer crystallites, which can suppress ion exchange. Lastly, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) indicates sidechain/electrolyte identity does not influence the electrolyte penetration depth into the films, and EGn sidechain inclusion increases electrolyte cation uptake. The material structural design insight and guidelines regarding the polymer‐electrolyte ion insertion/expulsion dynamics reported here should be of significant utility for developing next‐generation mixed ionic‐electronic conducting materials. [ABSTRACT FROM AUTHOR]

Zr-based bulk metallic glasses (BMGs) have many unique properties. Due to their excellent performance and manufacturing process, they have become a research focus in the material science community. Electrolyte Jet Machining (EJM) is a non-contact electrochemical processing method with high surface integrity and high material removal rate (MRR). In this research, the sub-millimeter channels fabricated by EJM on Zr-based BMGs have been studied to explore the dissolution mechanisms and surface integrity under different scanning rates and voltages. The results show that, with other machining parameters holding constant, an increase in voltage leads to a substantial enhancement in both the depth and width of the channels machined on Zr-based BMGs. Notably, the influence of voltage on the depth of the channels is particularly pronounced. Additionally, an escalation in scanning rate correlates with a decrease in channel depth, with minimal variation in channel width. This study indicates that alcohol-based EJM is an effective method to fabricate sub-millimeter channels and modulate structures on Zr-based BMGs. [ABSTRACT FROM AUTHOR]

Ionic liquids have emerged as an environmentally friendly alternative to the standard solvents and are now finding applications in various fields of science and industry like catalysis, electrochemistry, organic synthesis, and as electrolytes in fuel cells or supercapacitors. Recently, interest in their use as electrolytes for batteries has increased as they are thermally stable and non-irritating in contrast to standard electrolytes used in batteries. Application of ionic liquids could improve the safety in the future use of battery-powered devices over a wide range of temperatures. This mini review aims to discuss the literature reports on the use of ionic liquids as electrolytes in hydride batteries and protonic systems.

Zr-based bulk metallic glasses (BMGs) have many unique properties. Due to their excellent performance and manufacturing process, they have become a research focus in the material science community. Electrolyte Jet Machining (EJM) is a non-contact electrochemical processing method with high surface integrity and high material removal rate (MRR). In this research, the sub-millimeter channels fabricated by EJM on Zr-based BMGs have been studied to explore the dissolution mechanisms and surface integrity under different scanning rates and voltages. The results show that, with other machining parameters holding constant, an increase in voltage leads to a substantial enhancement in both the depth and width of the channels machined on Zr-based BMGs. Notably, the influence of voltage on the depth of the channels is particularly pronounced. Additionally, an escalation in scanning rate correlates with a decrease in channel depth, with minimal variation in channel width. This study indicates that alcohol-based EJM is an effective method to fabricate sub-millimeter channels and modulate structures on Zr-based BMGs.

Non‐aqueous redox flow batteries (RFBs) are emerging electrochemical technologies for grid energy storage. Non‐aqueous Mg RFBs that use Mg metal as the anode are especially promising due to various benefits of the Mg metal anode, including its low potential, high volumetric capacity, SEI‐free, highly reversible operation and low cost. Despite the potential, there are rarely any studies on developing non‐aqueous Mg RFBs. Herein, a non‐aqueous Mg redox flow battery using a polymer catholyte is reported. Through rational molecular engineering, a carbonyl‐based moiety is combined with a polyethylene glycol moiety to achieve a polymer with high voltage and high solubility in the ether‐based electrolyte. A series of polymers with different polyethylene glycol chain lengths are synthesized and their performances are measured first at the molecular level, and then at the device level in a Mg redox flow battery using a Mg foil as the anode, the polymer solution as the catholyte and a porous membrane as the separator. The flow battery delivers a voltage of 1.8 V, a maximum capacity of 475 mAh/L, an average Coulombic efficiency of 90.5%, an average voltage efficiency of 67.4%, an energy efficiency of 61.0%, and an energy density of 0.855 Wh/L. Systematic mechanistic studies are performed to understand the performance decay mechanism and possible strategies for future improvement are discussed. This work opens a new avenue for the development of energy storage technologies for grid electricity storage. [ABSTRACT FROM AUTHOR]

Copper electrodeposition on Au(111) from deep eutectic solvents (DESs) type III was investigated employing cyclic voltammetry as well as chronoamperometry. It was further examined on Au(poly) using the electrochemical quartz crystal microbalance (EQCM). The employed DESs are mixtures of choline chloride (ChCl) or choline nitrate (ChNO3) with ethylene glycol (EG) as hydrogen bond donor (HBD), each in a molar ratio of 1 : 2. CuCl, CuCl2, or Cu(NO3)2 ⋅ 3H2O were added as copper sources. Underpotential deposition (UPD) of Cu precedes bulk deposition in chloride as well as nitrate electrolytes. Cu deposition from Cu+ in chloride media is observed as a one‐electron reaction, whereas deposition from Cu2+ occurs in two steps since Cu+ is strongly stabilized by chloride. Cu+ is less stabilized by nitrate and the beginning of bulk deposition in the nitrate‐containing DES with Cu2+ is shifted by several hundred mV to more positive potentials compared to the chloride DES. A diffusion‐controlled, three‐dimensional nucleation and growth mechanism is found by chronoamperometric measurements and analysis based on the model of Scharifker and Mostany. [ABSTRACT FROM AUTHOR]

The necessity for large scale and sustainable energy storage systems is increasing. Lithium-ion batteries have been extensively utilized over the past decades for a range of applications including electronic devices and electric vehicles due to their distinguishing characteristics. Nevertheless, their massive deployment can be questionable due to use of critical materials as well as limited lithium resources and growing costs of extraction. One of the emerging alternative candidates is potassium-ion battery technology due to potassium's extensive reserves along with its physical and chemical properties similar to lithium. The challenge to develop anode materials with good rate capability, stability and high safety yet remains. Iron oxides are potentially promising anodes for both battery systems due to their high theoretical capacity, low cost and abundant reserves, which aligns with the targets of large-scale application and limited environmental footprint. However, they present relevant limitations such as low electronic conductivity, significant volume changes and inadequate energy efficiency. In this review, we discuss some recent design strategies of iron oxide-based materials for both electrochemical systems and highlight the relationships of their structure performance in nanostructured anodes. Finally, we outline challenges and opportunities for these materials for possible development of KIBs as a complementary technology to LIBs. [ABSTRACT FROM AUTHOR]

The electrodeposition of copper onto Au(111) from Deep Eutectic Solvents (DESs) type III has been studied by cyclic voltammetry. Investigations were carried out with mixtures of choline chloride (ChCl) and ethylene glycol (EG) or trifluoroacetamide (TFA). The eutectic compositions and temperatures were determined by differential scanning calorimetry (DSC). For the ChCl/EG DES, a eutectic ratio of 16 : 84 (ChCl:EG) was found instead of the previously reported ratio of 33 : 67. The electrodeposition of copper was studied for electrolytes with different ratios of ChCl to hydrogen bond donor (HBD) to resolve the influence of the composition on the deposition behavior. Both CuCl and CuCl2 were used as Cu salts. Underpotential deposition (UPD) is followed by bulk deposition with the diffusion rate of Cu species being dependent on the ratio of ChCl to HBD. With CuCl2, both Cu+ and Cu2+ species are reduced and deposited, whereby the two‐electron reduction is more dominant with higher chloride content and presence of EG. However, the properties of the Cu electrodeposition do not result from the freezing‐point depression of the DESs, but from the high concentration of ions. [ABSTRACT FROM AUTHOR]

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[Display omitted] • An simple method is reported to fabricate 3D porous Zn-Cu alloy electrodes. • The effect of Cu on the morphology and properties of alloy electrodes are revealed. • The Cu 0.3 Zn 9.7 shows excellent catalytic performance to CO comparable to Au and Ag. • The catalytic performance of Cu 0.3 Zn 9.7 is further improved in a novel electrolyte. Designing cheap and highly active electrochemical CO 2 reduction (ECO 2 R) systems are crucial for their commercial applications. Herein, we report a 3D porous Zn-Cu alloy electrode for ECO 2 R to CO. A small amount of Cu has a dramatic effect on the micro-morphology of the electrode. Furthermore, DFT calculations confirm that Zn-Cu alloying significantly reduces the formation energy barrier of *CO intermediates. The synergy between the unique 3D porous structure and the alloying effect enables the Cu 0.3 Zn 9.7 electrode to achieve up to 90.69 % Faraday efficiency (FE) for CO at −1.2 V (vs. reversible hydrogen electrode (RHE)). Furthermore, we prepare a novel non-aqueous cathode electrolyte consisting of deep eutectic solvent (DES) and propylene carbonate (PC) for ECO 2 R. The FE CO of Cu 0.3 Zn 9.7 increased to 94.89 % and the reduction potential decreased to −1 V (vs. RHE). The low cost of preparing 3D porous electrodes and the ease of synthesizing the novel non-aqueous electrolyte render this ECO 2 R system for CO promising for large-scale application. [ABSTRACT FROM AUTHOR]

The necessity for large scale and sustainable energy storage systems is increasing. Lithium-ion batteries have been extensively utilized over the past decades for a range of applications including electronic devices and electric vehicles due to their distinguishing characteristics. Nevertheless, their massive deployment can be questionable due to use of critical materials as well as limited lithium resources and growing costs of extraction. One of the emerging alternative candidates is potassium-ion battery technology due to potassium’s extensive reserves along with its physical and chemical properties similar to lithium. The challenge to develop anode materials with good rate capability, stability and high safety yet remains. Iron oxides are potentially promising anodes for both battery systems due to their high theoretical capacity, low cost and abundant reserves, which aligns with the targets of large-scale application and limited environmental footprint. However, they present relevant limitations such as low electronic conductivity, significant volume changes and inadequate energy efficiency. In this review, we discuss some recent design strategies of iron oxide-based materials for both electrochemical systems and highlight the relationships of their structure performance in nanostructured anodes. Finally, we outline challenges and opportunities for these materials for possible development of KIBs as a complementary technology to LIBs.

We have investigated the effect of annealing conditions onto the cadmium telluride (CdTe) layers obtained using potentiostatic electrodeposition from non-aqueous electrolyte. A conventional three-electrode geometry consisting; working (FTO), counter (Platinum) and reference (Ag/AgCl) electrodes were employed. The samples electrodeposited at − 0.625 V were annealed at 420 °C and cooled down with different procedures. The samples were characterized to study the structural, optical, morphological, compositional and transport properties. Quenched sample is found better as compared to naturally cooled and as-deposited samples. Growth of cubic polycrystalline crystal structure with improved crystallinity of CdTe is revealed from annealed samples. Highly stoichiometric CdTe layers with densely packed globular surface morphology of particle size ~ 2 μm obtained upon annealing the samples is proposed to be suitable for high efficiency thin film solar cells (TFSCs). The micro-structural Raman analysis supports the increased crystallinity and stoichiometric growth of sample after annealing. Highly ohmic behavior with higher carrier concentration and ideality factor measured for quenched samples is reported to be associated to sink in grain boundaries due to grain growth results the densification of sample leads to less defective layers. The results imply that annealing conditions have significant impact on the properties of CdTe samples and the quenched films may be most appropriate as an absorber layer for TFSC applications. [ABSTRACT FROM AUTHOR]

Although the utilization of deep eutectic solvents (DES) as non-aqueous electrolyte of redox flow batteries has received enormous attention, its properties like high viscosity and low conductivity always remain a matter of concern, due to their negative effect on final battery power performance. Herein, the introduction of two types of additive supporting electrolytes (one: a mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC) and the other: ethyl acetate (EA)) remarkably decreasing the viscosity and impedance of the DES with iron ions is reported, especially for DMC+EC. In addition, the cyclic voltammetry results show that the reversibility of Fe(III)/Fe(II) redox couple, and the reaction kinetics are improved after adding DMC+EC, while EA has little effect on improving the electrochemical performance. From Raman spectroscopy, it is found that a distinct characteristic peak occurs at 895 cm−1 for DMC+EC mixture, whereas the intensity of this peak is weak for EA. It is highly probable that the appearance of this characteristic peak serves to improve the electrochemical properties of DES. [ABSTRACT FROM AUTHOR]

The wafer-scale integration of graphene is of great importance in view of its numerous applications proposed or underway. A good graphene–silicon interface requires the fine control of several parameters and may turn into a high-cost material, suitable for the most advanced applications. Procedures that can be of great use for a wide range of applications are already available, but others are to be found, in order to modulate the offer of different types of materials, at different levels of sophistication and use. We have been exploring different electrochemical approaches over the last 5 years, starting from graphene oxide and resulting in graphene deposited on silicon-oriented surfaces, with the aim of understanding the reactions leading to the re-establishment of the graphene network. Here, we report how a proper choice of both the chemical environment and electrochemical conditions can lead to a more controlled and tunable graphene–Si(111) interface. This can also lead to a deeper understanding of the electrochemical reactions involved in the evolution of graphene oxide to graphene under electrochemical reduction. Results from XPS, the most suitable tool to follow the presence and fate of functional groups at the graphene surface, are reported, together with electrochemical and Raman findings.

Different micro–mesoporous carbons derived from d-glucose (GDC), granulated white sugar (WSDC) and highly decomposed Estonian peat (PDC) were synthesized using hydrothermal carbonization and direct activation methods. The resulting carbonaceous materials were activated using chemical (KOH and ZnCl2) and physical (CO2) activation methods. The electrochemical characteristics of the electrical double-layer capacitors (EDLCs) based on 1 M Et3MeNBF4 solution in acetonitrile and EtMeImBF4 were measured using two-electrode cells. The EDLCs assembled had specific capacitances from 20 up to 158 ± 18 F g−1 (in EtMeImBF4) and phase angle values from − 65° to − 88° (at low frequencies). The characteristic time constant values vary more than 10 times. Applying constant power discharge method, very high energy and power densities (34 W h kg−1 at 10 kW kg−1) for activated carbon powders-based EDLCs have been measured. Fitting of impedance data showed that enhanced mesoporosity reduces the adsorption and mass-transfer resistance values. [ABSTRACT FROM AUTHOR]

Rapid synthesis of gold nanoparticles (AuNPs) by pulsed electrodeposition was investigated in the non-aqueous electrolyte, 1-ethyl-3-methyl-imidazoliumbis(trifluoro-methanesulfonyl)imide ([EMIM]TFSI) with gold trichloride (AuCl3). To aid the dissolution of AuCl3, 1-ethyl-3-methyl-imidazolium chloride ([EMIM]Cl) was used as a supporting electrolyte in [EMIM]TFSI. Cyclic voltammetry experiments revealed a cathodic reaction corresponding to the reduction of gold at −0.4 V vs. Pt-QRE. To confirm the electrodeposition process, potentiostatic electrodeposition of gold in the non-aqueous electrolyte was conducted at −0.4 V for 1 h at room temperature. To synthesize AuNPs, pulsed electrodeposition was conducted with controlled duty factor, pulse duration, and overpotential. The composition, particle-size distribution, and morphology of the AuNPs were confirmed by field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The electrodeposited AuNPs were uniformly distributed on the platinum electrode surface without any impurities arising from the non-aqueous electrolyte. The size distribution of AuNPs could be also controlled by the electrodeposition conditions.

Electrodeposition of palladium from a mixture of choline chloride/urea/palladium(II) chloride (deep eutectic solvent) has been carried out by direct and pulse current electrodeposition. The influence of five organic additives, current mode (direct current vs. pulsed current) and hydrodynamics on the surface morphology of the electrodeposited palladium films was investigated. The surface morphology and thickness of the palladium layers produced was determined by scanning electron microscope and energy dispersive X-ray fluorescence spectroscopy. The experimental results showed that the surface morphology of the palladium deposits could be affected significantly either by applying pulse current and/or addition of organic additives. Current mode, electrolyte agitation and surface effects of the selected additives mutually interfere with each other, causing changes in the microstructure of the deposits (coarse → nodular/smooth). It was possible to improve the palladium deposit quality and metal deposition rate by addition of appropriate additives and by applying pulsed current. [ABSTRACT FROM AUTHOR]

As one of the most promising alternatives to next‐generation energy storage systems, aluminum batteries (ABs) have been attracting rapidly increasing attention over the past few years. In this review, we summarize the recent advancements of ABs based on both aqueous and non‐aqueous electrolytes, with a particular focus on rechargeable non‐aqueous ionic liquid‐based aluminum‐ion batteries (AIBs). Progress of the current intensive investigation on the development of cathode materials and electrolytes in non‐aqueous AIBs are discussed. Then research efforts towards aqueous ABs are described to give readers a broader view of the aluminum battery family. Finally, the review summaries the key challenges underpinning ABs and provides future research perspectives on this growing field. Aluminum Batteries: Thanks to the rich abundance of aluminum, low cost, and the high volumetric capacity, aluminum batteries have been attracting increasing attention over the past few years. This review presents recent progress on both aqueous and non‐aqueous aluminum batteries. Key challenges and future research perspectives in this growing field are discussed. [ABSTRACT FROM AUTHOR]

Electrolyte compatibility with sodium metal and known sodium‐ion battery cathodes is of intense interest recently. In this work, electrolytes including an ionic liquid (IL) additive are formulated and shown to enhance the properties of the well‐known Na3V2(PO4)3/C (NVP/C) cathode. NVP/C composite material was synthesized by a carbothermal reduction process and studied in cells containing either organic electrolyte (1 M NaClO4 in PC) or organic electrolyte with added [C3mpyr][NTf2] IL. In an electrolyte containing 5 wt % [C3mpyr][NTf2] IL, the cathode material exhibited a stable capacity of 107.0±0.7 mAh g−1 after 50 cycles at a C/2 rate; in contrast, the capacity obtained with the organic electrolyte was only 85±1 mAh g−1 after 50 similar cycles. In situ impedance spectroscopy revealed that the electrode‐electrolyte charge‐transfer resistance is lower in the organic electrolyte with IL. Consistent with this finding, XPS, SEM, EDX and TEM results indicate that the interfacial layer formed on the surface of the NVP/C cathode material in the presence of the IL is more compact than that formed in the organic electrolyte, and that reaction between cathode and electrolyte is suppressed by the IL. Ionic liquid based additive electrochemistry: 5 wt.% C3mpyr[TFSI] in organic electrolyte suppressed the polarization loss and formed a stable passivation film on NVP/C cathode material in a sodium ion battery [ABSTRACT FROM AUTHOR]

The application of novel organic redox materials is a plausible pathway towards techno-economic energy storage targets due to their low cost and sustainable design. Their operation in non-aqueous redox flow batteries affords researchers the opportunity to innovate, design and optimise these new chemistries towards practical energy densities. Despite this, the identification of high capacity organics which also display long-term stability is inherently challenging due to the high reactivity of molecular radicals. [ABSTRACT FROM AUTHOR]

Cu 2 O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu 2 O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu 2 O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu 2 O electrode to make the measurement possible, which could result in deviation from actual values. Here we introduce a non-aqueous electrolyte based on tetrabutylammonium-tetrafluoroborate in 3-methoxypropionitrile for electrochemical analysis of Cu 2 O. MS analysis shows reproducible results in terms of dopant density and flat band potential, while the analysis in aqueous (0.5 M Na 2 SO 4 ) electrolyte shows inconsistent, irreproducible results. In the case of IS, the transport resistivity of the layers was evaluated using the new electrolyte and shows a linear trend with thickness, as expected. The proposed non-aqueous electrolyte can potentially be used for the electrochemical analysis of other sensitive semiconductors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new multivalent metal–air battery employing Titanium (Ti) as active anode fuel material is introduced. • Ti metal is highly attractive as it is a light metal that can possibly transfer up to 4 electrons. • Ti–air battery could successfully be operated under relatively high current densities of up to 0.75 mA/cm−2. • Ti–air battery provides an average cell voltage of 1–1.2 V and a discharge capacity of 66 mAh cm−2. • Ti–air battery holds a unique potential to be the only metal with 4 electrons transfer during its operational discharge. A new multivalent metal–air battery employing Titanium (Ti) as active material in EMIm(HF) 2.3 F room temperature ionic liquid electrolyte is introduced. Ti metal is highly attractive as it is a light metal that can possibly transfer up to 4 electrons. The electrochemical behavior of Ti is known for its passivity in various media. Here, we evaluated the electrochemistry of Ti in EMIm(HF) 2.3 F with potentiodynamic polarization and galvanostatic discharge experiments. Ti–air battery could successfully be operated under relatively high current densities (up to 0.75 mA cm−2) with an average cell voltage of 1–1.2 V, yielding up to a discharge capacity of 66 mAh cm−2. When its full potential is harvested, such a metal–battery holds a unique potential to be the only metal with 4 electrons transfer during its discharge. [ABSTRACT FROM AUTHOR]

After determining the optimum composition of the butyronitrile: ethylene carbonate: fluoroethylene carbonate (BN:EC:FEC) solvent/co-solvent/additive mixture, the resulting electrolyte formulation (1M LiPF6 in BN:EC (9:1) + 3% FEC) was evaluated in terms of ionic conductivity and the electrochemical stability window, as well as galvanostatic cycling performance in NMC/graphite cells. This cell chemistry results in remarkable fast charging, required, for instance, for automotive applications. In addition, a good long-term cycling behavior lasts for 1000 charge/discharge cycles and improved ionic conductivity compared to the benchmark counterpart was achieved. XPS sputter depth profiling analysis proved the beneficial behavior of the tuned BN-based electrolyte on the graphite surface, by confirming the formation of an effective solid electrolyte interphase (SEI).

A new electroactive species benzophenone (BP) is identified for the anolyte of an all-organic redox flow battery (AORFB) due to its low redox potential, high electrochemical reversibility and stability, and high solubility in non-aqueous electrolyte. BP also shows high stability in a wide temperature range, and the elevated temperature enhances the redox reactions and the mass transfer rates, leading to an exponential increase of the diffusion coefficient. An AORFB based on BP anolyte is achieved with a cell voltage of 2.41 V and a theoretical energy density of 139 Wh L −1 . The cycling performance shows a stable coulombic efficiency of 81%. The results presented indicate that organic molecule BP is a promising anolyte active species for high-energy density AORFBs. [ABSTRACT FROM AUTHOR]

Propargyl methanesulfonate (PMS) is chosen as an electrolyte additive to study the interfacial performance between the electrolyte and spinel lithium titanate (Li 4 Ti 5 O 12 , LTO) electrode. The result displays that PMS can improve cyclability of Li/LTO cell. Very interestingly, a solid electrolyte interface (SEI) film is formed above 1.0 V in the voltage range of 3.0–0 V. The observations are explained in terms of PMS include triple-bonded compounds and SO 3 . The triple-bonded compounds were able to produce a characteristic SEI with dense and low impedance, which can effectively suppress the decomposition of electrolyte, HF generation and LiF formation upon cycling. The S O groups may acts as the weak base site to hinder the reactivity of PF 5 . Accordingly, the incorporation of PMS into the electrolyte can remarkably enhance the cyclic performance of the Li/LTO cell. [ABSTRACT FROM AUTHOR]

Widely used conductive carbon is found to be a major capacity contributor towards the sodium storage while used in electrode composition, in conjunction with NaClO 4 -PC electrolyte. Experimental studies show that the surface adsorbed sodium is present, confirmed by microscopic and XRD analysis. This unexpected property towards sodium storage in electrode conceals the electrochemical contributions expected from an active material. As the conductive carbon is a desirable component in sodium battery development, therefore this contribution needs to be optimized with respect to Coulombic efficiency. In order to investigate and optimize the unwanted capacity contribution from carbon containing electrode, we introduce an electrolyte system comprise of NaClO 4 -TEGDME, a low-cost electrolyte over extensively used PC-based compositions. This electrolyte composition controls the reversible capacity contribution to a minimum from the conductive carbon, and showed up to ∼97% reversibility with adequate stability till 100 cycles, within the potential range from 0.1 to 3 V. A detailed experimental analysis has been carried out to establish the electrolyte composition against conductive carbon. [ABSTRACT FROM AUTHOR]

Lithium plating and dendrite formation can occur on the graphite surface at high current densities. What is more, graphite generates a 10% volume change during cycling, resulting in a solid electrolyte interface (SEI) crack and further electrolyte decomposition. Here, p-Toluenesulfonyl isocyanate (PTSI) as an electrolyte additive is evaluated to overcome the above problem of Li/graphite cells. The results show that the cycling capacity of Li/graphite cell with 0.5 wt% PTSI is effectively enhanced at high current densities. Remarkably, we find that a stable SEI film derived from PTSI is generated on the graphite surface. The SEI film can obviously inhibit the reductive decomposition of electrolyte, electrode erosion and LiF formation upon cycling. This additive will provide new avenues for the rational engineering of advanced Li-ion batteries. [ABSTRACT FROM AUTHOR]

The importance of the choice of solvent in a non-aqueous redox flow battery (NARFB) cannot be overemphasized. Several studies demonstrated the influence of the solvent on electrolyte performance in terms of reaction rates, energy/power densities, and efficiencies. In this work, we investigate capacity decay as a direct consequence of varying reactant crossover rates through membranes in different solvent environments. Specifically, we demonstrate the superiority of an 84/16 vol% acetonitrile/1,3 dioxolane solvent mixture over pure acetonitrile in terms of energy efficiency (up to 89%) and capacity retention for vanadium NARFBs - while incorporating a Nafion 115 membrane. The permeability of Nafion to the vanadium acetylacetonate active species is an order of magnitude lower when pure acetonitrile is replaced by the solvent mixture. A method to estimate relative membrane permeability is formulated from numerical analysis of self-discharge experimental data. Furthermore, tests on a modified Nafion/SiO 2 membrane, which generally offered low species permeability, also show that different solvents alter membrane permeability. Elemental and morphological analyses of cycled Nafion and NafionSi membranes in different solvent environments indicate that different crossover rates induced by the choice of solvent during cycling are due to changes in the membrane microstructure, intrinsic permeability, swelling rates, and chemical stability. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (NCNTs) are directly grown on the surface of a three-dimensional (3D) Ni foam substrate by floating catalytic chemical vapor deposition (FCCVD). The electrochemical properties of the 3D NCNT-Ni foam are thoroughly examined as a potential electrode for non-aqueous redox flow batteries (RFBs). During synthesis, nitrogen atoms can be successfully doped onto the carbon nanotube (CNT) lattices by forming an abundance of nitrogen-based functional groups. The 3D NCNT-Ni foam electrode exhibits excellent electrochemical activities toward the redox reactions of [Fe (bpy) 3 ] 2+/3+ (in anolyte) and [Co(bpy) 3 ] +/2+ (in catholyte), which are mainly attributed to the hierarchical 3D structure of the NCNT-Ni foam electrode and the catalytic effect of nitrogen atoms doped onto the CNTs; this leads to faster mass transfer and charge transfer during operation. As a result, the RFB cell assembled with 3D NCNT-Ni foam electrodes exhibits a high energy efficiency of 80.4% in the first cycle; this performance is maintained up to the 50 th cycle without efficiency loss. [ABSTRACT FROM AUTHOR]

Employing solvent mixtures in the electrolyte of non-aqueous redox flow batteries can increase energy density and efficiency. In this paper, active species solubility, electrolyte conductivity, and redox reaction rates were examined systematically among a number of binary and ternary mixtures, consisting of acetonitrile and 5 polar aprotic co-solvents to identify mixtures with enhanced active species solubility and redox reaction rates. Although we used vanadium acetylacetonate as a model, the methodologies presented here are applicable when evaluating solvent mixtures for other active species. Our approach is distinctive in that it elucidated the trade-offs in desirable properties that are necessary when solvent mixtures are used for non-aqueous redox flow batteries. We found that in a vanadium acetylacetonate–based non-aqueous redox flow battery, the use of an 84/16 vol% acetonitrile/1,3-dioxolane binary solvent mixture resulted in an increase in the positive and negative sides reaction rates compared to that observed with pure acetonitrile. This binary mixture resulted in an improvement in reaction rate with no decrease in energy density and is a promising solvent system for other active species used for non-aqueous flow batteries. [ABSTRACT FROM AUTHOR]

Exploitation of hierarchical porous carbons is increasingly attractive for high-capacity lithium (Li)-oxygen (O 2 ) battery cathodes. However, their practical applications in non-aqueous electrolytes are limited by poor rechargeability, primarily due to the decomposition of carbon electrode and electrolyte. In this work, we report a vertically aligned carbon nanotube (VACNT)-ruthenium dioxide (RuO 2 ) core-shell (VACNT@RuO 2 ) cathode for non-aqueous Li-O 2 batteries. The cathode is fabricated with VACNT as the core material and hydrous RuO 2 as the shell material, which eliminates the direct contact between the carbon and nucleophilic reactive intermediate species in the electrolyte. In comparison with the VACNT cathode, the VACNT@RuO 2 cathode presents a superior rate capability (3.3-fold less reduction in capacity) and cycling stability (sustainable for 100 cycles), with a maximum capacity as large as 13.2 mAh cm −2 (6600 mAh g electrode −1 ) at 1.0 mA cm −2 . The proposed cathode exhibiting a binder-free and hierarchical core-shell structure is a promising candidate for rechargeable non-aqueous Li-O 2 batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Deposition/dissolution of Cu on Pt from ethaline occur in one-electron reactions. • A full (1 × 1) monolayer of Cu adatoms is formed on Pt(1 1 1) in ethaline. • No voltammetric signals of Cu UPD were observed for Pt(poly) in ethaline. • Surface structure determines the mechanism and rate of Cu OPD at the initial stages. • Cu OPD on Pt(1 1 1) and Pt(poly) in ethaline occurs via 2D and 3D growth, respectively. Deep eutectic solvents (DESs) attract ever greater interest as nonaqueous media for the electrodeposition of metals and alloys. This work investigates the initial stages of Cu electrodeposition from DES representing a mixture of choline chloride and ethylene glycol (ChCl:EG) with a (1:2) molar ratio that contains CuCl or CuCl 2 salts. These studies were performed by means of cyclic voltammetry and scanning probe microscopy on single-crystalline Pt(1 1 1) and polycrystalline Pt(poly) electrodes. Additional experiments on Cu deposition were carried out using an aqueous Cl−-rich solution (3 M NaCl + 0.01 M CuCl). The process of Cu underpotential deposition (UPD) on the surface of Pt(1 1 1) in DES is observed for the first time. It is proposed that a complete (1 × 1) monolayer of Cu adatoms is formed at potentials more positive than the onset of overpotential deposition (OPD). The comparison of results for Pt(1 1 1) and Pt(poly) in ChCl:EG (1:2) and in the aqueous 3 M NaCl solution confirms that the surface morphology and (co)adsorption of solution components play an important role in the Cu UPD process. In DES, as well as in the aqueous solutions containing CuCl, Cu OPD occurs via the reduction of Cu(I) ions. The Cu(I)/Cu(II) redox transition was observed at significantly more positive potentials. We conclude on the basis of voltammetry and in situ scanning tunneling microscopy (STM) data that the mechanism of Cu electrodeposition in DES is determined by the surface structure. STM data demonstrate the layer-by-layer growth of a two-dimensional Cu deposit on Pt(1 1 1), while the resulting Cu deposit on Pt(poly) is characterized by a grain-like morphology. We also demonstrate that the mechanism of Cu OPD affects the initial deposition rate under conditions of diffusion limitations. [ABSTRACT FROM AUTHOR]