Lithium Salt Electrolyte Research Articles

Diverse Microstructures and Quasi-Ionic Liquid-like Transport Mechanisms in Concentrated "Water-in-Salt" Lithium Salt Electrolytes: A Molecular Dynamics Study.

"Water-in-salt"(WIS) electrolytes as potential green and nonflammable electrolytes are currently applied in various energy storage devices, such as lithium-ion batteries and supercapacitors. However, the microstructure at molecular scale and fast ion transport mechanism in such aqueous electrolytes are still under heavy debate due to the complex interactions among ions and water. Here, molecular dynamics simulations are used to study the microstructure and ion transport behaviors from the very dilute LiTFSI/water solution to the highly concentrated WIS electrolytes. It revealed that the diverse microstructures such as completely hydrated ions, ion complexes, and bridge-water molecules are jointly responsible for the electrochemical stability of WIS electrolytes. Diffusion model analysis showed that the Li+ ions exhibit a vehicular transport mechanism with first shell water molecules and structural diffusion mechanism with TFSI- anions. The lithium ion and its first hydration shell act as a single cationic entity. The entity forms a quasi-ionic liquid-like dynamic transport structure with associated anions. Our study challenges previous findings that the high transport dynamics of lithium ions arises from their transport in water-rich nanodomains in high-concentration WIS systems.

Wettability, imbibition and interdiffusion of lithium-based water-in-salt electrolytes in nanoporous carbon in relation to energy storage: A neutron radiography study

Superconcentrated lithium salt electrolytes, or lithium-based Water-in-Salt (WiS) electrolytes emerge as alternative electrolytes in supercapacitors and advanced batteries, such as the Li–O2 ones, especially when combined with a mesoporous carbon with very high surface area. In this work, we analyze the wettability, imbibition, and diffusivity of very concentrated lithium salts in a bimodal mesoporous carbon with pores of 5 nm and 25 nm in diameter. For the first time a neutron radiography technique is used to determine the imbibition and interdiffusion of lithium salts in mesoporous carbon. We found that a 20 m LiTFSI aqueous solution wets the surface of graphite and mesoporous carbon better than water. As a consequence, this WiS electrolyte is embedded rather fast in the mesoporous carbon by the action of capillary forces, exhibiting an intrinsic permeability K = (1.16 ± 0.03).10−18 m2. Finally, by resorting to the different cross-section of the 6Li and 7Li isotopes for the neutron capture, we could analyze the diffusion of LiCl in D2O confined in the mesoporous carbon. The interdiffusion coefficient of the confined LiCl is 5.0 10−7 cm2 s−1, corresponding to a tortuosity coefficient τ = 1.32. This moderate confinement effect results from the strong ion association of the LiCl that precludes the electrostatic interactions of Li+ ions with the negative charge on the pore walls. In summary, the combined properties of the lithium-based WiS electrolytes and the mesoporous carbon allow us to glimpse their use in supercapacitors and Li–O2 batteries.

Additive-rejuvenated anions (De)intercalation into graphite cathode enables optimum dual-ion battery

Cathode-electrolyte interphase (CEI) has particular function in maintaining electrolyte and cathode stability. However, the CEI will also cause some negative effects on ion transport. It is crucial for optimizing the structure of CEI through additives in the electrolyte to improve the electrode reaction. In this study, we proposed using C3H3FO3 (FEC) as an additive to optimize an aqueous LiTFSI (bistrifluoromethanesulfonimide lithium salt) electrolyte. The incorporation of FEC modified the solvation structure of TFSI–, inhibit the formation of CEI with thicker size, thereby facilitating the intercalation of TFSI– into the selected graphite cathode. Consequently, the graphite's discharge capacity was doubled, reaching 47 mAh g−1. The influence of TFSI– solvation structure on CEI formation was further studied by the emerging correlative SEM, Raman imaging and TOF-SIMS techniques and theoretical calculation techniques. Using this optimization strategy, we successfully constructed an aqueous dual-ion battery using C24H10N2O4 and graphite as the anode and cathode with an impressive potential window of 2.55 V, which delivered the energy density of 66 Wh kg−1 at the power density of 128 W kg–1.

Ultrathin solid polymer electrolyte enabling mechanically-strong energy storing fiber reinforced composites

Structural batteries attract enormous research interest due to their advantages of integrated energy storage function in structure. Superior to the co-cured composite structural batteries based on glass fiber supported/reinforced liquid/low-strength polymer electrolyte, enhanced mechanical strength of solid polymer electrolyte would enable the facile fabrication of composite structural batteries through layer-by-layer stack up of composites and solid-state batteries. This work encloses a mechanically strong and self-supportive solid polymer electrolyte with a tensile strength of 9.28 MPa, significantly superior to the traditional PEO (Lithium salt) electrolyte. Systematic analysis of phase-microstructure-mechanical/electrochemical properties relationship of SPE with different fluoroethylene carbonate (FEC) amounts helps to find out a solid polymer electrolyte (SPE) with satisfactory ionic conductivity (0.35 × 10−4 S/cm) and high electrochemical stability window (4.6 V vs Li/Li+), based on which dimension-adaptable and mechanically-strong energy storing laminates which have high tensile strength of 343 MPa, tensile modulus of 30.6 GPa, flexural strength of 308 MPa, and high impact resistance have been successfully fabricated. The most surprising result is a capacity retention of as high as 67% of the original capacity in the 1st cycle and stable cycling of composite structural batteries over 50 cycles for the failed tensile sample, which points out its potential application in emergency rescue. We believe this work not only presents a facile method to fabricate solid polymer electrolytes but demonstrates the potential of this solid polymer electrolyte in facile fabrication of mechanically-strong composite structural batteries.

Improved Electrochemical Properties of Aqueous Lithium-Ion Batteries Via the Optimization of Gel Polymer Electrolytes

Lithium-ion batteries (LIBs) have been developed for their high energy density and long cycle life in military systems. However, the use of non-aqueous electrolytes based on toxic and flammable organic solvents have raised serious safety concerns including fire and explosion in LIBs. Aqueous LIBs with non-flammable and environmental aqueous electrolytes are promising alternative to eliminate the safety issues. Because aqueous batteries use water as a solvent of electrolyte, they are stable with no flammable. However, the narrow electrochemical stability window (ESW) of water in aqueous electrolytes limits operating voltage and energy density of aqueous batteries. Recently, ESW was expanded by applying a high concentration lithium salt electrolyte called “water-in-bisalt” (WIBS). A 4.0 V aqueous LIB was developed by passivating graphite anodes with hydrophobic LiTFSI-HFE gels, which effectively extended electrolyte stability [1].In this study, we developed a 4.0 V aqueous LIBs using UV-cured gel polymer electrolytes. Highly concentrated UV-cured gel polymer electrolytes were coated to cathodes and UV-cured gel protection layers were applied to anode surfaces for improving stability. Also, gel polymer electrolytes were optimized with various lithium salts and additives. We also evaluated cycle performance and safety such as cutting, penetration test with LiMn2O4∥graphite pouch type cells. There were no fires and explosions.

Design of Symmetric TiO2/LiI/TiO2 Electrochromic Devices for Gradient Shaded Smart Windows with Enhanced Switching and Cycling Properties

AbstractLi+ insertion and extraction inherently impact the switching dynamics and cycling stability of inorganic electrochromic (EC) electrodes. Herein, the extraction of Li+ out of the TiO2 lattice to release the electron is replaced by the charge recombination of the electron with I3− at the TiO2‐electrolyte interface, which avoids the mechanical breakdown of the electrodes and renders self‐bleaching with no applied voltages. A device design of the same two TiO2 nanocrystal (NC) electrodes combined with the redox lithium salt (LiI) electrolyte confers symmetric electrochromism. By applying a forward or reverse bias, the two TiO2 electrodes alternately serve as the electrochromic electrode and exhibit voltage‐controlled gradient coloration, a maximum optical modulation of 90% at 700 nm, and a doubled cycling performance. The microstructure of the TiO2 NC film is characterized by transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and Brunauer–Emmett–Teller methods. The electrochemical and electrochromic properties of the device are investigated using cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and Mott–Schottky method.

Solid polymer electrolytes: Ion conduction mechanisms and enhancement strategies

Solid polymer electrolytes (SPEs) possess comprehensive advantages such as high flexibility, low interfacial resistance with the electrodes, excellent film-forming ability, and low price, however, their applications in solid-state batteries are mainly hindered by the insufficient ionic conductivity especially below the melting temperatures, etc. To improve the ion conduction capability and other properties, a variety of modification strategies have been exploited. In this review article, we scrutinize the structure characteristics and the ion transfer behaviors of the SPEs (and their composites) and then disclose the ion conduction mechanisms. The ion transport involves the ion hopping and the polymer segmental motion, and the improvement in the ionic conductivity is mainly attributed to the increase of the concentration and mobility of the charge carriers and the construction of fast-ion pathways. Furthermore, the recent advances on the modification strategies of the SPEs to enhance the ion conduction from copolymer structure design to lithium salt exploitation, additive engineering, and electrolyte micromorphology adjustion are summarized. This article intends to give a comprehensive, systemic, and profound understanding of the ion conduction and enhancement mechanisms of the SPEs for their viable applications in solid-state batteries with high safety and energy density.

Deciphering reduction stability of sulfone and fluorinated sulfone electrolytes:Insight from quantum chemical calculations

Sulfones and fluorinated sulfones are preferred in high-voltage lithium-ion batteries, but the reasons for their decreased stability in various lithium salt electrolytes remain unknown. Twelve different sulfone-based solvents, Li+-solvent and Li+-solvent-anion complexes were studied herein via quantum chemical calculations to compare reduction potentials and initial decomposition reactions. The results show that position of fluorination has significant effect on the reduction potentials and significant elongation (over 50 %) of SC bond is responsible for the abnormal increase of reduction potential for α-fluorinated sulfones, leading to their poor reduction stability. Li+-solvent-FSI-/PF6- complexes have the preference for anionic reduction, spontaneous defluorination and production of LiF, which can produce a LiF-rich solid-electrolyte interface on graphite. Therefore, most β-fluorinated sulfones and regular sulfones are stable to graphite at high lithium salt concentrations, while only β-fluorinated sulfones are stable to graphite at low salt concentrations.

Achieving fast and stable Li+ transport in lithium-sulfur battery via a high ionic conduction and high adhesion solid polymer electrolyte

Solid-state lithium (Li)-sulfur (S) batteries are promising secondary batteries because of their high energy density and high safety, but their practical application is severely hindered by poor Li-ions (Li+) transport in batteries due to low ionic conduction of the electrolyte and unstable electrode/electrolyte interface. Here, we address the issue by using a polyurethane (PU)-based electrolyte. The polar urethane/urea groups of PU reduce the hopping energy barrier of Li+, which results in high ionic conductivity of 1.8 × 10-4 S cm-1 (25 °C), high ion transference number of 0.54, and low activation energy of 0.39 eV. In addition, the polar urethane/urea groups endow the electrolyte with high adhesion, which allows the electrode/electrolyte interfaces to self-heal timely after being damaged during cycling. Benefiting from these merits, a symmetric Li||Li cell using the polyolefin-PU-bis(trifluoromethane)sulfonimide lithium salt electrolyte can cycle for approximately 800 h with a stable overpotential (approximately 40 mV), and a solid-state Li-S battery using the electrolyte delivers a specific capacity of approximately 610 mAh g-1 after testing for 125 cycles at a S loading of about 4 mg cm-2. Self-healing of the electrode/electrolyte interfaces during cycling was observed in situ by a laser confocal microscope. This study demonstrates the importance of polar groups in electrolytes in maintaining a fast and stable Li+ transport, which can be applied to other solid-state batteries.

Performance Comparison of Reduced Graphene Oxide (rGO)-polyaniline (PANI) Supercapacitors with LiCl, Li2SO4, and H2SO4 Electrolytes

Reduced graphene oxide (rGO)-polyaniline (PANI) supercapacitors (SCs) are tested with 1 M LiCl, Li2SO4, and H2SO4 electrolytes. The SC performance is evaluated by electrical impedance spectroscopy, cyclic voltammetry (CV), and galvanostatic charging/discharging measurements. Electrochemical experiments indicate that rGO-PANI SCs with lithium salt electrolytes show a large pseudocapacitance (PC) effect whereas that with H2SO4 electrolyte shows a large electrical double-layer capacitance (EDLC) effect. The rGO-PANI SC with H2SO4 electrolyte has the largest areal capacitance of 48.83 mF/cm2, whereas those with LiCl and Li2SO4 electrolytes have the areal capacitances of 31.69 mF/cm2 and 22.35 mF/cm2, respectively. After a 10,000-cycle CV stability test, the rGO-PANI SC with Li2SO4 electrolyte shows some ion embedding, resulting in better cycling stability than those of SCs with LiCl and H2SO4 electrolytes.

Electroreduction of nitrogen with almost 100% current-to-ammonia efficiency.

In addition to its use in the fertilizer and chemical industries1, ammonia is currently seen as a potential replacement for carbon-based fuels and as a carrier for worldwide transportation of renewable energy2. Implementation of this vision requires transformation of the existing fossil-fuel-based technology for NH3 production3 to a simpler, scale-flexible technology, such as the electrochemical lithium-mediated nitrogen-reduction reaction3,4. This provides a genuine pathway from N2 to ammonia, but it is currently hampered by limited yield rates and low efficiencies4-12. Here we investigate the role of the electrolyte in this reaction and present a high-efficiency, robust process that is enabled by compact ionic layering in the electrode-electrolyte interface region. The interface is generated by a high-concentration imide-based lithium-salt electrolyte, providing stabilized ammonia yield rates of 150 ± 20 nmol s-1 cm-2 and a current-to-ammonia efficiency that is close to 100%. The ionic assembly formed at the electrode surface suppresses the electrolyte decomposition and supports stable N2 reduction. Our study highlights the interrelation between the performance of the lithium-mediated nitrogen-reduction reaction and the physicochemical properties of the electrode-electrolyte interface. We anticipate that these findings will guide the development of a robust, high-performance process for sustainable ammonia production.

High-Performance Dual-Ion Battery Based on a Layered Tin Disulfide Anode.

Energy issues have attracted great concern worldwide. Developing new energy has been the main choice, and the exploitation of the electrochemical energy storage devices plays an important role. Herein, a high-performance dual-ion battery system is proposed, which consists of a graphite cathode and SnS2 anode, with a high-concentration lithium salt electrolyte (4 M LiTFSI). The benefits from the typical sandwich-like layer structure of SnS2 are as follows: the highest discharge specific capacity of the battery could reach 130.0 mA h g–1 at a current density of 100 mA g–1, and even under an ultra-high current density of 2000 mA g–1, the highest capacity of 66.3 mA h g–1 is still achieved, with an outstanding capacity retention over 100% after 1000 cycles. Inspiringly, this system delivers an excellent low self-discharge of 1.19%/h, surpassing most of the reported dual-ion batteries. In addition, the working mechanism and structural stability are also investigated by X-ray diffraction and Raman spectra, indicating a good reversibility. These results reveal that this graphite/SnS2 dual-ion battery system could provide a promising alternative for a future high-performance energy storage device.

Triethylsulfonium-based ionic liquids enforce lithium salt electrolytes.

The demand for cheap production of energy and its efficient storage is huge nowadays. Sulfonium-based ionic liquids have exhibited a useful set of physical-chemical and electrochemical properties, which make them good prospective electrolytes for electrochemical double-layer capacitors and rechargeable lithium batteries. The ability of the researchers to correctly describe local ionic structural patterns in the electrochemical systems is a cornerstone of achieving sustainable progress in this field. Herein, we report an in silico investigation of a few lithium-triethylsulfonium electrolytes and correlate our results with the recently published electrochemical study. All chosen organic and inorganic anions have been recently used in the supercapacitor and lithium-battery electrolyte systems: bis(trifluoromethylsulfonyl)imide, perchlorate, hexafluorophosphate, and trifluoromethanesulfonate. Analyzing potential energy surfaces, ion-ionic coordination, electron density distributions, and structure properties, we identified that the best-performing electrolyte system is lithium bis(trifluoromethylsulfonyl)imide dissolved in triethylsulfonium bis(trifluoromethylsulfonyl)imide. In the mentioned system, we found the weakest cation-anion binding that resulted in the fastest ionic transport. The lithium-ion plays a paramount role in the coordination of all investigated anions, whereas the impact of the triethylsulfonium cation is relatively insignificant. The lithium-induced structural changes in the local order of the electrolyte are reflected by computed vibrational spectra. In the lithium-free systems, the anions strongly bind the triethylsulfonium cation via its electron-deficient α-methyl groups. Some of these electrostatically driven interactions may be classified as medium-strength hydrogen bonds. The computed cohesion energies explain the conductivity and viscosity trends obtained for similar electrolyte compositions in the recent experiments. The reported results will be interesting for researchers who develop Li-based energy storage devices that use room-temperature ionic liquids as non-volatile and electrochemically stable media.

Solvation Structure around Li+ Ions in Organic Carbonate Electrolytes: Spacer-Free Thin Cell IR Spectroscopy.

Organic carbonate electrolytes are widely used materials for lithium-ion batteries. However, detailed solvation structures and solvent coordination numbers (CNs) of lithium cations in such solutions have not been accurately described nor determined yet. Because transmission-type IR spectroscopy is not of use for measuring the carbonyl stretch modes of electrolytes due to their absorption saturation problem, we here show that simple spacer-free thin cell IR spectroscopy can provide quantitative information on the number of solvating carbonate molecules around each lithium ion. We could estimate the solvent (carbonate) CNs of lithium ions in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propylene carbonate, and butylene carbonate over a wide range of lithium salt concentrations accurately, and they are compared with the previous results obtained with attenuated total reflection IR spectroscopy technique. We anticipate that our spacer-free thin cell approach will potentially be used to investigate the solvation dynamics, chemical exchange process, and vibrational energy transfers between solvating carbonate molecules in lithium salt electrolytes when combined with time-resolved IR spectroscopy.

Physical and charge discharge behavior of facile PVDF-HFP nanocomposite microporous polymer electrolyte for lithium ion polymer batteries

Synthesized wurtzite ZnO nanostructures are incorporated on the poly (vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) matrix, which improves the thermal as well as porosity nature of as obtained thin film nanocomposite microporous polymer membrane (nanoCMPM). The membrane shows a favorable effect on the crystallinity (Xc) of 26.83% and melting temperature (Tm) of 142.9 °C that improves the conductivity of polymer electrolytes. Its characteristics were examined by thermal studies. The optimized polymer membrane was found to have a high degree of porosity (76%) and excellent film strength. The membranes were prepared as a polymer electrolytes in soaking lithium percholoride (LiClO4) salt solution and ethylene carbonate (EC) as well as dimethylene carbonate (DMC) in 1: 1 (v/v) ratio as plasticizer to form gel type nanocomposite microporous polymer electrolytes (nanoCMPE). It shows the ionic conductivity in the order of 10−3 S cm−1 at 298 K for all optimized polymer electrolytes with different lithium salt electrolyte concentrations. The polymer membrane electrolyte has good compatibility and fabricates [LiCoO2/PVDF-HFP-ZnO-LiClO4/mesocarbon microbeads (MCMB)] as coin type cell. The charge–discharge characteristics as well as cell performance were investigated at 0.5 C rate. The polymer electrolyte is a better candidate to perform in lithium ion polymer batteries.

Influence of Lithium Sulfate on the Kinetics of Hydrogen Oxidation in H2so4

During the last few years, development of lithium ion batteries (LIB) offers innovative solutions for energy storage and has major role in the global energy future. Now used for many purposes, the increase in energy demand is driving the development and the production of LIB towards more environmentally friendly methods while also reducing their production costs.Nemaska lithium, a Canadian collaborator in this project, is recognized as a new producer of lithium hydroxide, a key precursor for high capacity Li-ion cathode material production. In order to reduce the energy costs and to increase the efficiency of its LiOH production, Nemaska lithium is actively working on the optimization of its membrane electrolysis system. One of the possibilities is to replace the anode of the existing electrolysis process with a new technology based on Hydrogen Depolarized Anode (HDA). This new technology is based on hydrogen oxidation instead of oxygen evolution reaction, (H2(g) → 2H+ (aq) +2e-; E0=0,00V vs NHE), this configuration allows for the decrease of the voltage of the electrolysis cell.With a structure similar to proton exchange membrane fuel cells (PEMFC) anode, an HDA is a porous electrode, supplied with hydrogen from its gas diffusion side and in contact with the electrolyte in the catalyst coated side. The reaction itself is taking place in a small part of the electrode called the catalytic layer. It consists of a triple phase; an ionomer (for the proton’s transport), platinum nanoparticles (used as catalyst) and a conductive carbon (for electron transport). This study is focusing on two aspects that can influence the performance of the catalytic layer: the impact of the electrolyte on the reaction kinetics and its composition on its efficiency. In order to further advance our knowledge of the reaction mechanism occurring at the HDA, a study on the reaction kinetic of hydrogen oxidation on platinum was conducted. Usually studied in sulphuric acid, the reaction is monitored in this case in the presence of lithium sulfate. For this study, a rotating disk electrode (RDE) has been used. The advantage of this hydrodynamic method is to reduce the dependence of the system on mass transport in order to isolate kinetic current. Using the Koutecky-Levich equation combined with RDE measurements, a logarithmic representation of Tafel slopes for different lithium concentrations have been determined. Linking overpotential to current density, the Tafel curves are used to determine the influence of lithium sulfate on the kinetic of hydrogen oxidation. In a first step, the study was performed on platinum disk electrode. With this well-established system, it was possible to conclude a significant decrease in reaction kinetic in the presence of the salt. Subsequently, the same technique is conducted on a vitreous carbon electrode, where a porous catalytic layer close to HDA configuration is deposited. This configuration allows to study the impact of ionomer presence close to Pt nanoparticles that would change interface between platinum surface and lithium salt electrolyte.

Preparation of Li-S Polymer Battery Utilizing High Compatibility of Carbonaceous Materials with Highly Concentrated Electrolytes

Li-S batteries have received much attention as the next-generation secondary batteries because of their extremely high theoretical energy density. A roll-to-roll fabrication method based on continuous laminating and winding of the sheet-like electrodes and electrolyte without an electrolyte injecting process would enable a more efficient manufacturing process for mass production of Li-S batteries. In order to realize such batteries, it is necessary to prepare the sheet-type sulfur cathode electrode in which an electrolyte is incorporated. We recently reported that a less volatile, highly concentrated lithium salt electrolyte could serve as a good dispersing media of carbon nanotube (CNT).[1] In this study, the same method was applied not only to CNT but also to other carbonaceous materials to obtain sheet sulfur cathode electrode containing highly concentrated electrolytes that serve as the dispersing media. As a result, we fabricated a Li-S polymer battery by combining the sheet sulfur cathode and the polymer gel electrolyte membrane.[2] This is a trail to realize polymer Li-S battery fabricated by the roll-to-roll process.The cathode slurry was prepared by adding a dispersion solvent, NMP (N-methyl-2-pyrrolidone), to the mixture (sulfur, Ketjen black (KB), polymer, and highly concentrated electrolyte: [Li(SL)2][TFSA] (SL : sulfolane, [TFSA] = [N(SO2CF3)2])[3]). This slurry was coated to an Al foil current collector and dried to obtain the gel cathode. The gel electrolyte was prepared from PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) and [Li(SL)2][TFSA] by a solvent casting method. The Li-S polymer battery was then prepared using the gel cathode, electrolyte and Li-anode. Figure 1(a) shows a conceptual scheme of roll-to-roll making process for the Li-S polymer battery. By using the sheet-like cathode and gel electrolyte, a battery can be manufactured simply via laminating them with Li-anode. It is worth mentioning that the subsequent electrolyte injecting step can be omitted here because the gel cathode and electrolyte already contain uniformly distributed electrolytes. Figure 1(b) shows the charge-discharge curves of the Li-S polymer battery. The battery delivered the initial discharge capacity of 850 mAh g−1. After 20 cycles, nearly 700 mAh g−1 of capacity could be retained, which indicated reasonable cycling stability. In our previous research,[1] CNT was used as the carbonaceous material for the S gel cathode. However, in this study, we found the amounts of electrolyte could be greatly reduced by using KB. It is considered that CNT requires more electrolyte to disperse the aggregated bundles and to unbundle them by cation-π interaction. Hence, our results would indicate a great potential on designing the sulfur gel cathode by a very simple method with lower cost materials. The detailed electrochemical behavior of the Li-S polymer batteries will be discussed in the presentation. Further, studies on the effects of composition and thickness of the S gel cathode and gel electrolyte on the electrochemical behavior will be presented.

Influence of Lithium Sulfate on the Kinetics of Hydrogen Oxidation in H2so4

During the last few years, development of lithium ion batteries (LIB) offers innovative solutions for energy storage and has major role in the global energy future. Now used for many purposes, the increase in energy demand is driving the development and the production of LIB towards more environmentally friendly methods while also reducing their production costs.Nemaska lithium, a Canadian collaborator in this project, is recognized as a new producer of lithium hydroxide, a key precursor for high capacity Li-ion cathode material production. In a constant improvement ambition, Nemaska Lithium decided to study the opportunity to use an Hydrogen Depolarized Anode (HDA) in order to save energy for the direct electromembrane synthesis of high purity Lithium Hydroxide (LH). This new technology is based on hydrogen oxidation instead of oxygen evolution reaction, (H2(g) -> 2H+ (aq) +2e-; E0=0,00V vs NHE), this configuration allows for the decrease of the voltage of the electrolysis cell.With a structure similar to proton exchange membrane fuel cells (PEMFC) anode, an HDA is a porous electrode, supplied with hydrogen from its gas diffusion side and in contact with the electrolyte in the catalyst coated side. The reaction itself is taking place in a small part of the electrode called the catalytic layer. It consists of a triple phase point; an ionomer (for the proton’s transport), platinum nanoparticles (used as catalyst) and a conductive carbon (for electron transport). This study is focusing on two aspects that can influence the performance of the catalytic layer: the impact of the electrolyte on the reaction kinetics and its composition on its efficiency. In order to further advance our knowledge of the reaction mechanism occurring at the HDA, a study on the reaction kinetic of hydrogen oxidation on platinum was conducted. Usually studied in sulphuric acid, the reaction is monitored in this case in the presence of lithium sulfate. For this study, a rotating disk electrode (RDE) has been used. The advantage of this hydrodynamic method is to reduce the dependence of the system on mass transport in order to isolate kinetic current. Using the Koutecky-Levich equation combined with RDE measurements, a logarithmic representation of Tafel slopes for different lithium concentrations have been determined. Linking overpotential to current density, the Tafel curves are used to determine the influence of lithium sulfate on the kinetic of hydrogen oxidation. In a first step, the study was performed on platinum disk electrode. With this well-established system, it was possible to conclude a significant decrease in reaction kinetic in the presence of the salt. Subsequently, the same technique is conducted on a vitreous carbon electrode, where a porous catalytic layer close to HDA configuration is deposited. This configuration allows to study the impact of ionomer presence close to Pt nanoparticles that would change interface between platinum surface and lithium salt electrolyte.

Spectral deconvolution in electrophoretic NMR to investigate the migration of neutral molecules in electrolytes.

Electrophoretic nuclear magnetic resonance (eNMR) is a powerful tool in studies of nonaqueous electrolytes, such as ionic liquids. It delivers electrophoretic mobilities of the ionic constituents and thus sheds light on ion correlations. In applications of liquid electrolytes, uncharged additives are often employed, detectable via 1 H NMR. Characterizing their mobility and coordination to charged entities is desirable; however, it is often hampered by small intensities and 1 H signals overlapping with major constituents of the electrolyte. In this work, we evaluate methods of phase analysis of overlapping resonances to yield electrophoretic mobilities even for minor constituents. We use phase-sensitive spectral deconvolution via a set of Lorentz distributions for the investigation of the migration behavior of additives in two different ionic liquid-based lithium salt electrolytes. For vinylene carbonate as an additive, no field-induced drift is observed; thus, its coordination to the Li+ ion does not induce a correlated drift with Li+ . On the other hand, in a solvate ionic liquid with tetraglyme (G4) as an additive, a correlated migration of tetraglyme with lithium as a complex solvate cation is directly proven by eNMR. The phase evaluation procedure of superimposed resonances thus broadens the applicability of eNMR to application-relevant complex electrolyte mixtures containing neutral additives with superimposed resonances.

An ultra-stable lithium plating process enabled by the nanoscale interphase of a macromolecular additive

A nanostructured macromolecular lithium salt electrolyte additive is reported. It can serve as a flexible physical barrier between Li/electrolyte interphase and provide extra Li+. Some of its functional groups can absorb HF, reducing parasitic reactions at high temperature.