Nanoengineering of non-aqueous liquid electrolyte solutions for future lithium metal batteries.

High-voltage lithium metal batteries suffer from poor cycling stability caused by the detrimental effect on the cathode of the water moisture present in the non-aqueous liquid electrolyte solution, especially at high operating temperatures (e.g., ≥60 °C). To circumvent this issue, here we report lithium hexamethyldisilazide (LiHMDS) as an electrolyte additive. We demonstrate that the addition of a 0.6 wt% of LiHMDS in a typical fluorine-containing carbonate-based non-aqueous electrolyte solution enables a stable Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) coin cell operation up to 1000 or 500 cycles applying a high cut-off cell voltage of 4.5 V in the 25 °C−60 °C temperature range. The LiHMDS acts as a scavenger for hydrofluoric acid and water and facilitates the formation of an (electro)chemical robust cathode|electrolyte interphase (CEI). The LiHMDS-derived CEI prevents the Ni dissolution of NCM811, mitigates the irreversible phase transformation from layered structure to rock-salt phase and suppresses the side reactions with the electrolyte solution.

Thin films of LiMn2O4 have been prepared by RF magnetron sputtering on interdigitated microarray electrodes. In situ conductivity–potential profiles and cyclic voltammograms during extraction/insertion processes of Li ions were obtained simultaneously in nonaqueous and aqueous electrolyte solutions (1 M LiClO4/propylene carbonate and 1 M LiCl/water). The electronic conductivity of Li1– x Mn2O4 was found not to show metallic transition and maintain its semiconducting state during the extraction/insertion of Li ion. A slight decrease in conductivity was observed with increasing the anodic potential, i.e., with increasing x (lithium extraction) and recovered reversibly when the potential returned to the cathodic side (re-insertion of Li ions). Similar results were obtained in both aqueous and nonaqueous electrolyte solutions.

Thin foil preparation of Mg-Li alloys using a non-aqueous electrolyte

Exploratory studies on some electrochemical cell systems

Perovskite La0.6Sr0.4CoO3-δ (LSC) and Ba0.5Sr0.5Co0.8Fe0.2O3- δ (BSCF) oxides are still low in the catalytic activity of oxygen reduction reaction (ORR) although it exhibits relatively good catalytic activity for oxygen evolution reaction (OER) when using as oxygen electrode catalyst. To improve the ORR activity of the LSC, palladium (Pd) was deposited over the LSC surface with four different weight percent. The physicochemical properties of Pd decorated perovskite La0.6Sr0.4CoO3-δ (Pd/LSC) was studied by using various analytic techniques. It was observed that the palladium is deposited only on the surface of LSC powders in nanostructure forms with a stoichiometric composition, which gives no influence on the crystallinity of LSC. The surface area of the Pd/LSC samples increases with increasing the weight percentage of Pd and, over 10 wt%, dramatically increases due to the formation of Pd porous structure over the perovskite surface. The electrochemical characterization of the Pd/LSC was examined in both aqueous and non-aqueous electrolyte solutions. In aqueous electrolyte, the Pd/LSC materials exhibit higher ORR and OER activities than LSC and KB. The ORR activity rapidly increases with the increase of Pd wt% deposited in order of 5<10<20<30, while the OER activity displays not much different values for all the Pd weight percentages. The Pd/LSC materials were applied as air cathode catalyst of lithium air battery to examine their catalytic performances in non-aqueous electrolyte. The Pd/LSC materials exhibit higher catalytic activities in oxygen electrochemical reactions than LSC and KB. 30wt% Pd/LSC shows the highest discharge capacity and the longest cycle life. It is concluded that the decoration of Pd over perovskite LSC oxide is more effective to increase the ORR activity, resulting in increasing the performance of lithium air battery.

The need for alternative high energy and power density energy sources has led scientists to study extensively the electrochemical energy conversion/storage devices such as electrochemical double layer capacitors (EDLC), batteries, fuel cells, etc. The values of power and energy densities of EDLC depend strongly on the properties of the electrode material and electrolyte used. EDLCs based on non-aqueous electrolytes or room temperature ionic liquids have a wider region of ideal polarizability (ΔE) compared to those based on traditional aqueous electrolytes 1-4. The wider ΔE in turn improves the energy and power density values of EDLCs. The specific adsorption of halide ions at single crystal electrodes from aqueous and non-aqueous electrolyte solutions has been demonstrated before 5,6. However, the specific adsorption of ions is a complicated process (depending on the electrode potential, chemical composition and concentration of halides etc.) and the kinetics of formation/rearrangement of electrical double layer between electrode and ionic liquid (IL) needs an extended examination. The main aim of this work was to characterize the adsorption of iodide ions from the mixture of two ionic liquids based on the same electrochemically stable 1-ethyl-3-methylimidazolium cation. Electrochemical impedance spectroscopy and cyclic voltammetry methods have been applied to study the electrochemical characteristics of the interface between pyrolytic graphite (PG) and mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium iodide (1-10 wt%). All measurements were carried out in a 3-electrode electrochemical cell using a PG as a working, Pt net as a counter, and Ag wire coated with AgCl as a reference electrodes. Current density (i) vs. electrode potential (E) dependencies (Fig. 1) show that two peaks in CV are caused by the addition of x wt% of EMImI into EMImBF4 (for PG | EMImBF4 interface there is no peaks within the potential region from ─1.5 V to +1.5 V (vs. Ag | AgCl)). Reduction and oxidation processes are more intensive in more concentrated solutions. A strong dependence of current density on the potential scanning rate (υ) for PG | EMImBF4+EMImI interface was observed in the region of peaks. Also the capacitance values calculated from CV data (Ccv= i / υ) show the strong dependence on υindicating a very slow adsorption process occurs. The shape of the complex impedance plane, i.e. Nyquist plots, total impedance and phase angle vs. frequency dependences depend strongly on the electrode potential and on the concentration of the I-ions in the solution. The values of series differential capacitance (C s) were calculated from Nyquist dependencies at different fixed ac frequencies (C s = (Z''i2πf)−1; where i = √−1and Z’’ is the imaginary part of impedance). C s depends strongly on ac frequency and electrode potential, increasing at lower ac frequencies and at anodic range of potentials. C s values depend also on the added amount of I-(1-10%) to the solution, increasing from 1 to 5wt% and diminish in more concentrated solutions. References L. Siinor, J. Poom, C. Siimenson, K. Lust, E. Lust, J. Electroanal. Chem., 719, 133 (2014).L. Siinor, C. Siimenson, K. Lust, E. Lust, Electrochem. Commun. 35, 5 (2013).R. Palm, H. Kurig, K. Tõnurist, A. Jänes, E. Lust, Electrochim. Acta, 85, 139 (2012).R. Palm, H. Kurig, K. Tõnurist, A. Jänes, E. Lust, Electrochem. Commun. 22, 203 (2012).L. Siinor, K. Lust, E. Lust, J. Electroanal. Chem., 601, 39 (2007).M. Väärtnõu, E. Lust, J. Electroanal. Chem., 565, 211 (2004). Acknowledgements Estonian Energy Technology Program project SLOKT10209T, Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117, Functional Micro/Mesoporous Nanomaterials for Novel Energy Conversion and Storage Systems IUT 20-13, Functionalization of carbon nanomaterials: synthesis, characterization and application SLOKT12180T.

Electrochemical performance of activated carbons prepared from rice husk in different types of non-aqueous electrolytes

The paper presents three datasets obtained by electrochemical quartz microbalance technique which was applied to studies of conducting polymer film in contact with non-aqueous electrolyte solution. The first dataset describes the calibration procedure of gold-coated quartz crystal, immersed in acetonitrile silver ion-containing electrolyte, by means of silver layer electrodeposition. On the basis of experimentally measured dependence of the resonance frequency on the varying electrode mass in the course of electrochemical silver deposition/dissolution, the calibration coefficient was found to be equal to 13.6 ng/Hz. The second dataset has been collected when thus calibrated EQCM cell was used for determination of the mass change due to the polypyrrole film growth during anodic oxidation of pyrrole monomer from its acetonitrile solution. Its treatment reveals the proportionality between the mass change and the charge spent for pyrrole electrooxidation, the proportionality coefficient being 53.5 g per mole of electrons. The third dataset contains EQCM measurement data during repetitive charge-discharge treatment of the deposited polypyrrole film (cyclic voltammetry, CV) in monomer-free electrolyte. Collected data shows that continuous cycling of the polymer film leads to progressive increase of the cation-exchange contribution to the total ion flux which maintains the film's electroneutrality during variation of its redox state. These findings might be useful both for a qualitative consideration of the cycling stability of polypyrrole in non-aqueous medium and for a quantitative mathematical modelling of polypyrrole electropolymerization and its redox transformations.

Remarkable progress has been achieved during the last 20 years in the experimental study of capacitance properties for a number of solid metals. Those are polycrystalline electrodes of Pb, Bi, Tl, Sb, Cd, Sn, Ga, In, Cu, Zn, Ag, and Au in contact with aqueous electrolyte solutions as well as, in some cases, with nonaqueous ones. Interfacial characteristics have also been measured for some single-crystal faces of Ag, Au, Cu, Zn, Bi, Pb, Cd, Sn in aqueous solutions. Moreover, capacitance properties of a single-crystal face in contact with a nonaqueous electrolyte solution, (111) Bi ethanol solutions, have been determined. A major contribution to this advance was made by a group of Soviet electrochemists headed by Frumkin. Some important results for gold and silver electrodes were obtained by French and Bulgarian scientists.KeywordsCapacitance CurveSolid MetalCompact LayerRoughness FactorDouble Layer StructureThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Lithium metal batteries are widely considered to be a next-generation battery technology due to their high energy density, fast charging capability, and potential to power a wide range of applications, from portable electronics to electric vehicles.Compared to conventional lithium-ion batteries, which use graphite as the anode material, lithium metal batteries have the potential to offer significantly higher energy density. This is because lithium metal has a much higher theoretical capacity than graphite, meaning it can store more energy per unit weight or volume. As a result, lithium metal batteries could potentially offer longer run times and smaller form factors than lithium-ion batteries, which are already widely used in consumer electronics and electric vehicles.In addition to their high energy density, lithium metal batteries also offer fast charging capabilities. This is because the lithium metal anode can be charged more quickly than the graphite anode used in conventional lithium-ion batteries. This could enable faster charging times for electric vehicles and other applications, reducing the time required for recharging and improving their overall usability.However, one of the major challenges with lithium metal batteries is dendrite growth, which can occur when lithium metal ions deposit unevenly on the surface of the anode during charging. These dendrites are needle-like structures that can penetrate the separator and cause short-circuits, leading to reduced battery performance and safety issues. As a result, much of the research on lithium metal batteries has focused on developing strategies to prevent dendrite growth, such as using coatings or electrolytes with additives that can stabilize the lithium metal anode.Despite these challenges, lithium metal batteries continue to be a promising next-generation battery technology. Researchers are working on improving their energy density, charging speed, and safety, and they are exploring a range of applications, from portable electronics to electric vehicles and grid-scale energy storage. If these challenges can be overcome, lithium metal batteries could revolutionize the energy storage industry and enable a wide range of new and exciting applications.To address this issue, we have explored the use of various coatings on the lithium metal anode to prevent dendrite growth. In this study, ordered mesoporous silica with different pore sizes and pore structures, such as SBA-15 and KIT-6, were used as coatings between the lithium metal anode and separator.SBA-15 and KIT-6 are two types of mesoporous silica materials that are widely used in various applications due to their unique properties. The synthesis of these materials involves the use of templates to control the pore size and structure.They are synthesized using a combination of a surfactant(pluronic P123 or cetyltrimethylammonium bromide;CTAB) as the template and tetraethyl orthosilicate(TEOS) as the silica source. The synthesis involves mixing a solution of surfactant and TEOS in acidic conditions, followed by aging and calcination steps. The resulting materials have a highly ordered hexagonal pore structure(SBA-15) and body-centered cubic pore structure(KIT-6) with a pore size ranging from 5 to 20 nm.By coating the surface of the lithium metal with a uniform pore structure material such as ordered mesoporous silica, dendrite growth can be suppressed and lithium deposition can occur more uniformly.The uniform pore structure material acts as a physical barrier to lithium ion diffusion and helps to control the deposition of lithium ions onto the surface of the lithium metal. When lithium ions are deposited onto the surface of the lithium metal, they can form a layer of lithium that can grow and become thick over time. If the lithium layer is too thick, it can become unstable and form dendrites. However, the uniform pore structure material can help to limit the thickness of the lithium layer and promote the deposition of lithium ions in a more uniform manner, thus reducing the likelihood of dendrite formation.Additionally, the uniform pore structure material can help to reduce the concentration of lithium ions at the surface of the lithium metal, which is another factor that can contribute to dendrite growth. By limiting the concentration of lithium ions at the surface, the uniform pore structure material can help to prevent the formation of high-concentration regions that can promote dendrite growth.Overall, the mechanism by which a uniform pore structure material can suppress dendrite growth involves controlling the deposition of lithium ions onto the surface of the lithium metal, limiting the thickness of the lithium layer, and reducing the concentration of lithium ions at the surface. These factors help to promote more uniform lithium deposition and prevent the formation of dendrites, leading to improved battery performance and safety.

<p indent="0mm">Since the commercialization of lithium-ion batteries in the 1990s, lithium-ion batteries have been successfully applied in portable electronics, electric vehicles, and grid energy storage. Although current organic liquid electrolytes have high ionic conductivities, they are inherently flammable, volatile, and prone to leakage. Moreover, severe side reactions and dendrite growth on the surface of the lithium anode during the charge-discharge process can cause safety hazards, which greatly impede their applications in lithium metal batteries. Solid electrolytes, including inorganic solid electrolytes and polymer electrolytes, are regarded as effective alternatives to organic liquid electrolytes for the construction of lithium metal batteries with high energy density and safety. Among them, solid polymer electrolytes offer excellent flexibility, processability, and interfacial compatibility over inorganic solid electrolytes, and they are extraordinarily promising for lithium metal batteries with high energy density and safety. Ideal solid polymer electrolytes should have following features: (1) High ionic conductivity (&gt; <sc>10 ^–4 S cm ^–1) </sc> at room temperature; (2) high lithium ion transference number (~1) to reduce the concentration polarization and improve the rate performance of batteries; (3) intimate contact at the electrode/electrolyte interfaces; (4) wide electrochemical window <sc>(&gt;4.5 V</sc> vs. Li/Li ⁺) to match high-voltage cathodes and improve the energy density of batteries; (5) good mechanical stability to resist processing, buffer electrode volume change and inhibit dendrite growth; (6) good thermal stability to withstand environmental changes. Generally, the ionic conductivity of pure solid polymer electrolytes at room temperature is low <sc>(~10 ^–6 S cm ^–1). </sc> Researchers have tried to improve the ionic conductivities by adjusting the lithium salt concentration, such as developing “polymer-in-salt” solid electrolytes. However, increasing the concentration of lithium salt leads to the deterioration of the mechanical strength. Strategies such as developing novel lithium salts, modifying polymer matrix, and incorporating inorganic fillers into solid polymer electrolytes are proposed to promote ionic conductivities of solid polymer electrolytes. In particular, composite polymer electrolytes, fabricated by dispersing a certain amount of inorganic fillers into solid polymer electrolytes, have improved ionic conductivities without sacrificing their mechanical performances. Poor interfacial property between electrodes and electrolytes is also a critical issue for solid polymer electrolytes. On one hand, poor and uneven solid/solid contacts at the electrode/electrolyte interfaces lead to high resistance and sluggish ionic transport kinetics. Furthermore, the volume change of the positive and negative electrodes in the charge/discharge process deteriorates the interfacial contacts, blocks the ion and electron transport through the interfaces, and greatly reduces the electrochemical reaction kinetics. On the other hand, the electrochemical windows of solid polymer electrolytes are usually narrow <sc>(＜4.5 V).</sc> During cycling, redox reactions are prone to occur at the electrode/electrolyte interfaces, causing battery failure. Solid polymer electrolytes have also poor thermal and mechanical stabilities. Therefore, design and synthesis of polymer-based solid electrolytes with excellent comprehensive performances and construction of fast and stable ion transport channels at the electrolyte/electrode interfaces are of great significance for the successful development of solid-state lithium metal batteries. This paper presents a brief review of the research progress in solid polymer electrolytes from two aspects: Improving the ionic conductivities of solid polymer electrolytes and enhancing the interfacial performance at electrolyte/electrode interfaces. First, targeted optimization strategies on ionic conductivities of solid polymer electrolytes, including constructing continuously aligned ionic transport paths and shortening the ionic transport distance, are summarized. Second, interface optimization strategies, including constructing wetting interfaces and synthesizing asymmetric electrolytes, are presented to reduce the interface resistance and improve the interfacial contact. Finally, perspectives on the development of solid polymer electrolytes and high-performance solid-state lithium metal batteries are discussed, and key research directions and advanced test methods are proposed. This review may provide a comprehensive understanding and further guidance for not only the material design of solid polymer electrolytes, but also the structural design of lithium metal batteries with favorable electrochemical and interfacial performances.

Transport properties of non-aqueous lithium electrolyte coexisting with porous solid materials: Montmorillonite-based electrolyte composite system

A quantum-chemical study on the boron centers in nonaqueous electrolyte solutions and polymer electrolytes

Transference numbers of Cl− ion in nonaqueous electrolyte solutions

Transference numbers of K+ ion in nonaqueous electrolyte solutions