Alternative Electrolyte Research Articles

Protic Ionic Liquid as an Alternative Electrolyte for Simultaneous Electrochemical Determination of Caffeine and Nicotine in Environmental and Food Samples

Caffeine (CAF) and nicotine (NIC) are emerging contaminants and are among the most consumed substances in the world, making it crucial to monitor these contaminants. In this work, an alternative electrolyte, 2-hydroxyethylammonium acetate (2HEAA) was used for the development of an electroanalytical method for determination and quantification of CAF and NIC, simultaneously, using differential pulse voltammetry (DPV). The system with the 2HEAA electrolyte was characterized by cyclic voltammetry and electrochemical impedance spectroscopy, and the DPV parameters were optimized for the best conditions. The method was validated from a calibration curve obtained which showed limit of detection (LOD) of 0.82 and 6.26 μmol L-1 and limit of quantification (LOQ) of 2.73 and 20.8 μmol L-1 for CAF and NIC, respectively. In the precision analyses, values lower than 10% of relative standard deviation were obtained. In the presence of concomitant inorganic and organic species, the system proved to be selective in the determination of analytes. The method was used to determine the analytes in fortified samples (river water, synthetic urine and commercial milk), obtaining recoveries between 87.25 and 111.40%. The 2HEAA demonstrated high efficiency as an alternative electrolyte with good signal-to-noise ratio, increased analytical sensitivity of the method, in addition to presenting low cost and fast electrolyte preparation.

Anodic Dissolution and Electropolishing of Titanium in an Amide-Type Ionic Liquid Containing Halide Ions

Titanium is widely used in the medical, food, aerospace, semiconductor, and chemical industries due to its low density, high corrosion resistance, and biocompatibility. The surface smoothing of the Ti components is often required in these fields. The smooth and bright surface without the Beilby layer can be obtained by electropolishing. However, electropolishing of Ti has been conducted in alcohol-based electrolytes and highly concentrated acidic solutions containing perchlorate acids with applying high voltage. Therefore, a safe and alternative electrolyte is required for electropolishing of Ti with high current efficiency. Amide-type ionic liquids (ILs) composed of bis(trifluoromethylsulfonyl)amide (TFSA–) are attractive candidates as alternative electrolytes for electropolishing of metals and alloys because of the negligible vapor pressure and non-flammability. The surface smoothing and brightening of Sn has been reported to be possible in BMPTFSA (BMP+: 1-butyl-1-methylpyrrolidinium), due to the formation of the viscous layer near the electrode[1]. It is reported that the anodic dissolution of Ti was suppressed by the native oxide film on the surface in TMHATFSA (TMHA+: trimethyl-n-hexylammonium)[2]. On the other hand, the electropolishing of type 316 stainless steel has been reported to be possible in BMPTFSA containing Cl–[3], although the Cr-rich oxide layer is known to act as the protective layer against corrosion. In the present study, the mechanism of anodic dissolution and electropolishing of Ti covered with the native oxide film were investigated in BMPTFSA containing Cl–. In addition, the anodic behavior of Ti in BMPTFSA was also investigated in the presence of Br–. Electrolytes containing halide ions were prepared by dissolving BMPCl and BMPBr in BMPTFSA. Electrochemical measurement was conducted using a three-electrode cell in an Ar-filled glovebox at 353 K. A Ti plate and disc were used as a working electrode. A Pt wire and a glassy carbon plate were used as a counter electrode. An Ag wire immersed in BMPTFSA containing 0.1 M AgCF3SO3 was used as a reference electrode (Ag|Ag(I), +0.43 V vs. ferrocene|ferrocenium at 298 K). The surface of a Ti electrode was observed using a scanning electron microscope. The dissolved Ti species in the electrolyte was identified using an ultraviolet-visible (UV-Vis) spectrometer. The anodic current was observed in a linear sweep voltammogram of a Ti electrode in 0.5 M BMPCl/BMPTFSA, although the anodic current was negligible in BMPTFSA in the absence of Cl–. An absorption peak assignable to [TiCl6]2– was observed in the UV-Vis spectrum of the electrolyte after potentiostatic electrolysis at 0 V vs. Ag|Ag(I), indicating that Ti was anodically dissolved to form the tetravalent complex. The surface of a Ti electrode was brightened and smoothed after the potentiostatic anodic oxidation at 0 V vs. Ag|Ag(I), indicating that electropolishing of Ti covered with the native oxide film was possible in BMPTFSA in the presence of Cl–. The morphology of a Ti electrode changed after anodic polarization in BMPTFSA containing Br–, suggesting that the Ti surface was dissolved in BMPBr/BMPTFSA.[1] N. Yuza, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 168, 036509 (2021).[2] T. Uda, K. Tsuchimoto, H. Nakagawa, K. Murase, Y. Nose, and Y. Awakura, Mater. Trans., 52, 2061 (2011).[3] N. Serizawa, S. Yamasaki, and Y. Katayama, 2023 Joint Symposium of Molten Salts, 1B06 (2023).

Synthetic Graphites as the Cathode Material for Aluminium-Carbon Batteries

Developments such as growth in electric vehicle production and increased use of renewable energy sources, has caused an exponential increase in the demand for batteries [1,2], with Li-ion batteries as the dominating technology. Various issues are associated with the materials of Li-ion batteries, like an uncertainty about the future access, environmental footprint and social impact related to raw materials extraction and production, as well as the challenge of recycling [3]. For this reason, there is a renewed interest in alternative battery chemistries, and one candidate technology is the Aluminium-Carbon (Al-C) battery. This is a so-called dual-ion concept, with an Al anode, a carbon (mostly graphite) cathode, and an electrolyte based on Al salts. During charging, anions intercalate into the graphite, while Al deposits on the anode [4]. Al has a high theoretical volumetric and gravimetric capacity, in addition to being abundant [5]. Like graphite, it is also a low-cost material [4,5], so using these together can provide an affordable battery technology. In addition, these batteries would be very convenient to recycle due to the mature, worldwide recycling infrastructure of Al [6] combined with the fact that graphite can withstand high temperature treatment [7]. The most commonly used electrolyte is AlCl3 in 1-Ethyl-3-methylimidazolium chloride (EMIMCl), which is a thermally stable ionic liquid [8]. It also has a high ionic conductivity [8], allowing high currents and subsequently high-power batteries, but it has the drawback of being highly corrosive [9]. Alternative electrolytes are aluminium trifluoromethanesulfonate (Al(OTF)3) or aluminium bis(trifluoromethanesulfonyl)imide (Al(TFSI)3) and LiAlH4 in tetrahydrofuran (THF), which eliminates the corrosion issue. With Al(OTF)3 as the main salt, it has been shown to reversibly plate Al [10]. However, to the best of our knowledge such electrolytes are not used in Al-C batteries to this date.Work on Al-C batteries have been conducted with a wide range of carbons (e.g. natural and synthetic graphites or fibrous carbon materials), and it has been shown that a high degree of crystalline perfection and flake-shaped particles are preferred for high capacity [4,11]. Capacities obtained when using graphite powders are in the range between 60 and 142 mAh/g, depending on their characteristics [4]. Al-C batteries can also have excellent rate capabilities, as observed in the work of Wu et al. [12] where a 3D graphitic foam gave a stable capacity around 60 mAh/g for 4000 cycles at the high rate of 12 A/g. However, carbon materials for which outstanding results are reported, are not always commercially available. Al-C batteries are still at an early stage of development, and knowledge related to graphite properties and how these affect stability at high voltages, and intercalation of anions from the relevant electrolytes is still limited.In this work, we have studied industrially relevant synthetic graphites as cathodes for Al-C batteries, with the purpose of investigating the anion intercalation and oxidation stability with respect to graphite properties, like surface area, surface structure (edge, basal and defect sites), and surface chemistry. Graphite powders have been investigated by nitrogen adsorption, LECO oxygen analysis and XRD measurements in order to determine the relevant properties. The electrolytes used are AlCl3 in EMIMCl, and Al(OTF)3 as well as Al(TFSI)3 with LiAlH4 in THF. To provide further information about the reactions happening during cycling, post-mortem characterization of cycled electrodes with SEM, AFM, FTIR and Raman spectroscopy is carried out. In this manner it can be investigated if the reactions occurring is the wanted reversible intercalation, or if irreversible reactions at the electrode surface also take place.This project has received funding from The Research Council of Norway: Contract number 331964. Partners in the project are NTNU, SINTEF Industry, Vianode, Beyonder and Equinor ASA.

Spectroscopic Studies of Cation Structure Dependence on Lithium-Ion Conductivity in Phosphonium Ionic Liquid Electrolytes

1. Introduction In recent years, there has been active progress towards transitioning to electric vehicles (EVs) with the aim of realizing a carbon-neutral society, resulting in intensified development of lithium-ion secondary batteries (LIBs) with higher energy density. However, commercially available electrolytes for LIBs, while having a wide electrochemical window, often exhibit high volatility, posing a risk of fire hazard during thermal runaway. Ionic liquids (ILs) are promising materials as alternative electrolytes because of their excellent properties such as flame retardance, volatility resistance, and wide potential window.In our laboratory, we have focused on quaternary phosphonium-based ILs, which show higher electrochemical stability compared to common ILs such as imidazolium, pyrrolidinium, and ammonium, and evaluated them as electrolytes for LIBs.1) As a result, by optimizing the cation structure, we have found that ILs derived from trimethylphosphine can achieve relatively high-rate charge-discharge capability.2) In this study, we aimed to clarify the effect of the phosphonium cationic structure of ionic liquids on discharge rate characteristics. 2. Experimental Bis(fluorosulfonyl)amide (FSA)-based phosphonium ILs, triethyl(buthyl)phosphonium FSA (P2224-FSA) and triethyl(ethoxymethyl)phosphonium FSA (P222(2O1)-FSA), were dried by heating and stirring at over 80 °C for 24 h under vacuum. Then lithium salt (LiFSA) was added to these ILs (0.2–1.5 mol dm–3).Electrochemical measurements were conducted using a two electrodes half-cell. The cell was assembled using Li metal and graphite as the positive and negative electrodes, respectively, with a separator between them. The charge–discharge tests were conducted at 303 K in a constant current (CC) mode between 0 and 1.5 V (vs. Li metal). For the discharge rate test condition was followings, the charge condition was fixed at 0.05 C, and the discharge conditions were set to 0.05 C, 0.5 C, 1 C, 2 C, and 5 C. Self-diffusion coefficients of Li+, phosphonium and FSA– were determined by PGSTE-NMR. The conductivities were determined by an ac impedance measurement using a two Au-electrode cell. Raman spectra of the ILs were measured by micro-Raman spectroscopy featuring a continuous-wave green laser at room temperature (293 K). 3. Results and discussion Fig. 1 shows the results of the discharge rate test with phosphonium ILs electrolytes. Although the discharge capacity of P2224-FSA decreased with increasing the C-rate, P222(2O1)-FSA, which includes an ether structure, maintained high discharge capacity even at high-rate conditions In this study, we investigated the spectroscopic behavior of phosuphonium ILs for clarifying their ionic conduction mechanism.The self-diffusion coefficients, ionic transfusion numbers and conductivities of each C Li + = 1 M ILs are listed in Table 1. Despite the higher self-diffusion coefficients of the respective ions in P222(2O1)-FSA than in P2224-FSA, there was no significant difference between each IL’s ionic conductivity.Raman spectroscopy was used to evaluate the interaction between Li+ and FSA–. Fig. 2 shows the Raman spectra of C Li + = 1.5 M P2224-FSA and P222(2O1)-FSA. Two peaks appear around 1,220 cm–1 and 1,230 cm–1, which originate fromfree FSA– and Li+-boundFSA, respectively.3) The intensity ratio of these bands tended to change with IL cation species. The ratio derived from free FSA– was greater for P222(2O1)-FSA than for P2224-FSA. These results suggested that the structure of phosphonium affected Li+ solvation of phosphonium ILs. 4. Conclusions We found that the phosphonium cation with an ether chain weakens the FSA– solvation to Li+. This suggests that desolvation of part of the FSA– might occur due to the interaction of the ether chain with Li+. In ILs based on phosphoniums with ether chains, the ILs cationic structure might more influence on the Li+ conduction mechanism than in phosphonium ILs whiout ether chain. Acknowledgments This study was supported by a Grant-in-Aid for Scientific Research (B) from JSPS, Japan. This work was partly supported by a project, Gear of Education and Advanced Resourced (Gear 5.0). References 1) Tsunashima and M. Sugiya, Electrochem. commun., 9, 2353–2358 (2007).2) Matsumoto et al., SSRN Electron. J., (2023).3) Fujii, et al., J. Phys. Chem. C, 117, 19314−19324 (2013). Figure 1

Deep Eutectic Solvents As Novel Solvent-Electrolyte System for Electroreductive Transformations

Organic electrosynthesis is regarded as a sustainable alternative to traditional organic synthesis as it enables replacement of stochiometric redox agents with electricity – which can be generated from renewable sources – and high product selectivity at ambient conditions [1]. However, the poor conductivity of the organic solvents typically requires the addition of large amounts of supporting electrolyte salts, leading to increased waste generation and lowered atom economy of the process.Alternative solvents such as room temperature ionic liquids (RTILs) and deep eutectic solvents (DESs) represent a promising alternative electrolyte and solvent in electrosynthesis. They are conducting, non-volatile and able to solubilize several organic compounds as well as easily separated from products by extraction and thus prone for reuse [2-4]. In addition, they have a tunable, large electrochemical window and this has already led to their use as electrolytes in other fields of electrochemistry, including batteries, electrochromic devices, supercapacitors and in electrodeposition processes [5-6].DESs offer some advantages compared to RTILs, including that their synthesis is comparable inexpensive and simple, requiring no purification. In addition, some of the DES are biodegradable. DESs have already been use in organic synthesis as solvents and catalysts, however only few examples use DESs as electrolyte systems in organic electrosynthesis despite their advantageous properties. DESs can also solubilize untreated biomass and biomass components, and thus they are attractive solvents for several biorefinery processes including pretreatment, fractionation, and catalytic conversion [7]. Selective reductive transformations are key in biomass valorization to yield precursors for fuels and chemicals.In this work, we show how DESs can play a dual role as solvent and electrolyte for reductive transformations of organic compounds. The physical and electrochemical properties of the DESs and their role in the reaction are investigated. In addition, the feasibility of reusing the DES over several reactions is examined.[1] Frontana-Uribe, B.A.; Little, R. D.; Ibanez, J. G.; Palma, A. & Vasquez-Medrano, R. Green Chem. 2010, 12, 2099-2119.[2] Singh, S. K. & Savoy, A. W. J. Mol. Liquids 2020, 297, 1120938[3] Hansen, B. B.; Spittle, S.; Chen, B.; Poe, D.; Zhang; Y., Klein; J. M.; Horton, A.; Adhikari, L.; Zelovich, T.; Doherty, B. W.; Gurkan, B.; Maginn, E. J.; Ragauskas, A.; Dadmun, M.; Zawodzinski, T. A.; Baker, G. A.; Tuckerman, M. E.; Savinell, R. F. & Sangoro, J. R. Chem. Rev. 2021, 121, 1232–1285.[4] Kathiresan, M., & Velayutham, D. Chem. Commun. 2015, 51, 17499.[5] Armand, M.; Endres, F.; MacFarlane, D. R.; Ohno, H. & Scrosati, B. Nat. Mater. 2009, 8, 621–629.[6] Abbott, A. P. Curr. Opin. Green Sustain. Chem. 2022, 36, 100649.[7] Wang, Y.; Kim, K. H.; Jeong, K.; Kim, N. K.; Yoo, C. G. Curr. Opin. Green Sustain. Chem. 2021, 27, 100396.

Resilient and Confined Polymer Microlattices for Low-Swelling, Pressure-Free Lithium Metal Pouch Cells

Automotive and consumer applications require batteries that last longer, recharge faster, and readily integrate into mass-manufactured battery packs. Of the available cell packaging designs, pouch cells with lithium (Li) metal anodes are attractive because they can achieve ~95% packaging efficiency, allow size and shape flexibility, and have high theoretical specific energy. Li metal anodes, however, suffer from dramatic thickness increases as they are cycled, which leads to pouch cell swelling of up to 220% by volume. Although current Li metal pouch cells incorporate alternative electrolytes, protective layers, and current collectors to prevent Li dendrite growth and stabilize the solid-electrolyte interphase (SEI), high initial external pressures of 54 to 1,000 kPa are required to suppress cell swelling and maintain stable Li deposition. Maintaining a high pressure is impractical in most applications, requires considerable extra mass and volume not accounted for in reported battery metrics, and increases the complexity of cooling. Despite these applied pressures, Li pouch cells still swell at least 39%, which is far from commercial requirements of less than 10%, causes serious safety issues, and makes integration incompatible with most electric devices. In a cell with 39% swelling, the Li anode swells up to 300% so that the final anode volume is four times the initial volume and the volumetric capacity is 33% of Li’s 2093 mAh cm-3 theoretical capacity, which is lower than the volumetric capacity of lithiated graphite (790 mAh cm-3). Additionally, these challenges are escalated in high-capacity and high-rate Li metal pouch cells. New Li electrode designs that provide control over interfacial chemistry while accommodating the extreme mechanics of Li plating and etching are required to break current technical bottlenecks for practical Li metal batteries.This talk will report the use of architected polymer microlattices that combine chemical and mechanical functions to enable high-rate, swelling-free, and pressure-free Li anodes and anode-less pouch cells. The 3D printed gyroidal polymer contains Li+ affinitive sites that accelerate Li+ transport and the gyroidal microgeometry is highly resilient and confines Li growth. Unlike prior Li anodes and porous Li scaffolds that need an SEI layer across large surface areas, 89% of the Li surface in the gyroid is covered by the polymer and the microgeometry is optimized so the remaining Li-electrolyte interface is protected by a LiF-rich SEI layer generated by F donating groups on the polymer. We study the LiF generated at the polymer and show that it moves up to 100 micrometers across the Li surface to enhance the anode stability. We also show how the combined chemical, mechanical, and geometric control allows dense and void-free Li metal to grow into complex 3D shapes. In a 5 mAh cm-2 pouch cell with zero external pressure, we demonstrate swelling-free Li deposition at 5-30 mA cm-2, or 1–6 C-rates, for over 100 cycles. Li deposition efficiency was 99.86% in a carbonate electrolyte with an areal capacity of 10 mAh cm-2 and 10 mA cm-2 current density. The Li anode achieved a 1,580 mAh cm-3 volumetric capacity. A 366 Wh kg-1 anode-less Li metal pouch cell (15.4 Ah) incorporating polymer microlattices on copper as the anode and a LiNi0.8Mn0.1Co0.1O2 (NMC) cathode achieved over 333 cycles with 80% capacity retention. The final cell swelling was below 2%. Insights into the excellent performance of these batteries can provide new paths towards achieving high rate and long life Li metal pouch cells with zero swelling.Figure Caption: Polymer microlattice enabling pressure-free and swelling-free Li metal pouch cells. a, During Li deposition, the growth and merging of Li particles generate voids even under a pressure of 54-1,000 kPa, causing cell swelling of 39-220%. b, Polymer microlattices confine Li deposition in the gyroidal channels through chemical interactions and mechanical resilience. The polymer contains -NH2 or CH2CH2O- groups to accelerate Li+ transport and -SO2F to generate LiF to protect the remaining Li surface. The crosslinked polymer is highly resilient and restrains Li for dense deposition. c,d,Cycling stability (a) and voltage profiles (b) of an anode-less Li metal pouch cell, presenting a cell-level energy density of 366 Wh kg-1. NMC was used as the cathode. e, The measurement of cell thickness upon cycling. 6 sampling points were collected. Figure 1

Investigation of structural and electrical properties of electrolyte LaGaO3 for solid oxide fuel cell.

Electrochemical devices such as solid oxide fuel cells (SOFCs) allow the direct transformation of fuel's chemical energy into electrical power. Even though YSZ electrolyte-based conventional SOFCs are widely used in both laboratories and on a commercial scale, developing alternative ion-conducting electrolytes is crucial for enhancing SOFC performance at lower operating temperatures. In this work, we conducted a thorough computational analysis on the characteristics of Sr- and Mg-doped superior oxide ion conductors. We have used the DFT technique to examine the system's electrical and structural characteristics and the impact of doping. The GII value and LaGaO3 formation energy are used to investigate thermodynamical and structural stability, respectively. Theoretical investigations are validated against data to ensure the accuracy of the computational model. The research shows that the properties of Sr- and Mg-doped LaGaO3 have changed in a desirable way. This DFT study sheds light on the underlying mechanisms that affect the structural and electronic properties of LaGaO3 electrolytes and offers a thorough investigation of the synergistic effects of strontium and magnesium co-doping. The knowledge acquired is critical for the logical design and development of more stable and efficient solid oxide fuel cells.

400 °C operable SOFCs based on ceria electrolyte for powering wireless sensor in internet of things

Solid oxide fuel cells (SOFCs) can generate high-efficiency and clean power but face a high-temperature bottleneck that hinders their widespread application. If alternative electrolytes can be developed to reduce the operating temperatures, the application of SOFCs will possibly be expanded to more scenarios, such as power sources for the Internet of Things (IoT). Herein, as a proof of the concept, a 400 °C operable SOFC is developed based on a precipitation-method prepared CeO2 electrolyte for powering wireless sensor in IoT system. Material studies indicate the CeO2 electrolyte sample forms a coating structure with a thin layer of amorphous carbonate covering the surface of CeO2 particles, which could result in fast hybrid proton and oxygen ion transport. The fabricated CeO2 electrolyte-based SOFCs exhibit promising power densities of 0.275–0.650 W cm−2 with open circuit voltages of 1.04–1.11 V at 400–500 °C, indicative of feasible cell operation at 400 °C. It is also found the cell has high repeatability and good stability for 150 h under different current densities. With the aid of a power management unit, the developed SOFC is further applied to charge a supercapacitor, for powering a customized IoT system to monitor environmental parameters. The charge process is fast and stable. Our study thus developed a 400 °C operable SOFC based on CeO2 electrolyte and demonstrates the feasibility of SOFC as power sources for LoT technology for the first time.

Comparative Study of High Voltage Spinel∥Lithium Titanate Lithium‐ion Batteries in Ethylene Carbonate Free Electrolytes

AbstractA persistent obstacle towards the realization of high voltage cathodes is electrolyte instability where oxidation and transition metal dissolution manifest in rapid capacity failure with both issues connected to the presence of ethylene carbonate in the electrolyte. Here, alternative electrolyte co‐solvents are investigated and compared, where the cyclic carbonate is replaced with sulfones ethyl methyl sulfone (EMS) and tetra methylene sulfone (TMS) and fluoroethylene carbonate (FEC). The best full cell performance was observed for cells cycled in a FEC/EMC (3/7) and FEC/EMC (1/1) electrolytes which exhibited 84–85 % capacity retention after 500 cycles. TMS/EMC (3/7), was determined to be the best performing sulfone electrolyte and maintained 71 % capacity after 500 cycles. Post‐mortem XPS analysis indicated different film forming mechanisms for the respective co‐solvent. A thicker cathode electrolyte interphase (CEI) on the LNMO was observed for the FEC containing electrolytes (relative to when TMS was used as the co‐solvent) indicating more effective passivation of the reactive cathode surface which correlated well with the enhanced cycling stability observed. For LTO, more evidence of transition metal migration and a thicker solid electrolyte interphase (SEI) layer was observed for the sulfone electrolyte suggesting more parasitic anode‐electrolyte interactions and an inability to mitigate Mn2+/Ni2+ crosstalk.

A Multifunctional Additive for Long‐Cycling Lithium‐Sulfur Batteries Under Lean‐Ether‐Electrolyte Conditions

AbstractThe failure of lithium‐sulfur (Li‐S) batteries operating under lean‐ether‐electrolyte conditions can be ascribed to the deterioration of electrolytes, the passivation of cathodes, and the degeneration of lithium anodes. Efforts to address these challenges by exploring alternative electrolytes beyond commonly used ether‐based systems often introduce new complications. In this study, the utilization of a multifunctional additive, 2‐Bromoacetamide (BA), for ether electrolytes is proposed to achieve stable Li‐S batteries under lean‐electrolyte conditions. These investigations reveal that the amide bond in BA forms hydrogen bonds with sulfur atoms, promoting the dissolution of lithium sulfides (Li2S) in ether electrolytes and mediating the conversion of lithium polysulfides. This enhanced solubility of Li2S facilitates 3D deposition (vertical to the substrate) rather than the typical 2D deposition (parallel to the substrate) of Li2S, and thus alleviates the passivation of cathodes. Furthermore, the incorporation of BA promotes uniform and dense lithium deposition. The use of the BA‐containing electrolyte enables stable cycling of a Li‐S pouch cell for 40 cycles, even under a low electrolyte‐to‐sulfur ratio of 4 µL mg−1. This multifunctional strategy offers an effective solution to extend the lifetime of Li‐S batteries under lean‐electrolyte conditions, thereby paving the way for practical applications of Li‐S battery technology.

On the moisture tolerance of LiFSI based lithium-ion batteries: A systematic study on NMC622/graphite full cells

Lithium-ion battery (LIB) technology is state-of-the-art energy storage technology for portable electronics and electric vehicles (EVs). In this incumbent LIB technology, lithium hexafluorophosphate (LiPF6) is the most widely used electrolyte salt to date. However, the challenges related to its chemical/thermal stability, sensitivity to moisture and the consequent formation of strong acids such as hydrogen fluoride (HF) need to be resolved with alternative salts. Due to its better chemical/thermal stability, resistance to moisture and HF formation, and better ionic conductivity, lithium bis(fluorosulfonyl)imide (LiFSI) has been considered as a promising alternative electrolyte salt to LiPF6. In this study, the effect of addition of 1000 ppm water on LiFSI based electrolytes was systematically investigated by testing NMC622/lithium and artificial graphite/lithium half and NMC622/graphite full cells in four LiFSI based electrolytes; plain LiFSI, LiFSI + 1000 ppm H2O, LiFSI + 10 wt% FEC, and LiFSI + 1000 ppm H2O + 10 wt% FEC. Post mortem characterization of selected electrodes was also conducted with SEM imaging and XPS to study the surface chemistry and morphology of cycled electrodes. Overall, this study shows that 1000 ppm water can slightly improve the electrochemical performance of NMC622/lithium half cells; however, the same amount of moisture severly degrades the graphite half and NMC622/graphite full cells.

Benchmarking the Performance of Lithium and Sodium‐Ion Batteries With Different Electrode and Electrolyte Materials

ABSTRACTSodium‐ion (Na‐ion) batteries are considered a promising alternative to lithium‐ion (Li‐ion) batteries due to the abundant availability of sodium, which helps mitigate supply chain risks associated with Li‐ion batteries. Many studies have focused on the design of Li‐ion batteries, exploring their energy, power, and cost aspects. However, there is still a lack of similar research conducted on Na‐ion batteries. A comparison of the cell voltage characteristics and rate capability of sodium and lithium‐ion batteries using different types of electrodes and electrolytes. For sodium‐ion batteries electrolytes used are NaPF6 and NaClO4 and electrodes used are NaCoO2, NaNiO2, NaFePO4, (Na3V2(PO4)3), graphite, hard carbon, sodium metal, and sodium titanate. For lithium‐ion batteries with LiPF6 and KOH electrolytes and electrodes as LiCoO2, NMC, LVP, Li2MnSiO4, graphite, silicon, lithium titanate (LTO), lithium metal. A thorough analysis of six important performance metrics is part of the investigation: Ragone plots, Electrolyte salt concentration versus spatial coordinate, electrolyte potential versus spatial coordinate, Cell voltage versus battery cell state of charge, Cell voltage versus time, and state variable versus time. Comparing operating voltage and rated capacity NMC and graphite is selected for lithium‐ion batteries as this combination provides operating voltage up to 4.2 V and a rated capacity of 275 Wh/kg, for sodium‐ion for NaCoO2 and hard carbon which has an operating voltage of 2.5–3.8 V and rated capacity around 200 Wh/kg and another combination of electrode as NaFePO4 and sodium metal with NaClO4 electrolyte has a maximum operating voltage of 2.8–3.8 V and rated capacity around 200 Wh/kg. This paper shows significant influence of electrolyte selection on battery performance. The Ragone plots demonstrate that LiPF6 electrolytes in lithium‐ion batteries and NaPF6 electrolytes in sodium‐ion batteries both exhibit superior specific energy densities compared to their KOH and NaClO4 counterparts, respectively. The work presented in this paper encourages researchers to select alternate electrolytes and electrodes for lithium‐ion and sodium‐ion batteries in order to obtain optimal device performance.

Enhancing the stability of sodium-ion capacitors by introducing glyoxylic-acetal based electrolyte

Sodium-ion Capacitors (SICs) are becoming increasingly important energy storage devices. This study presents an in-depth comparison of a largely used electrolyte for said application, sodium hexafluorophosphate in ethylene carbonate:propylene carbonate (NaPF6 in EC:PC), with the novel electrolyte sodium bis(trifluoromethanesulfonyl)imide in 1,1,2,2-tetraethoxyethane:propylene carbonate (NaTFSI in TEG:PC). Firstly, half-cells of the SIC standard electrode materials, hard carbon (HC) and activated carbon (AC), are shown to perform comparably well with the two electrolytes. However, the use of the novel electrolyte in SICs allows for an improved stability during float tests. All in all, the novel electrolyte NaTFSI in TEG:PC appears to be a very promising alternative electrolyte for SIC application.

Enriching Nano-Heterointerfaces in Proton Conducting TiO2-SrTiO3@TiO2 Yolk-Shell Electrolyte for Low-Temperature Solid Oxide Fuel Cells.

A challenging task in solid oxide fuel cells (SOFCs) is seeking for an alternative electrolyte, enabling high ionic conduction at relatively low operating temperatures, i.e., 300-600°C. Proton-conducting candidates, in particular, hold a significant promise due to their low transport activation energy to deliver protons. Here, a unique hierarchical TiO2-SrTiO3@TiO2 structure is developed inside an intercalated TiO2-SrTiO3 core as "yolk" decorating densely packed flake TiO2 as shell, creating plentiful nano-heterointerfaces with a continuous TiO2 and SrTiO3 "in-house" interfaces, as well the interfaces between TiO2-SrTiO3 yolk and TiO2 shell. It exhibits a reduced activation energy, down to 0.225eV, and an unexpectedly high proton conductivity at low temperature, e.g., 0.084 S cm-1 at 550°C, confirmed by experimentally H/D isotope method and proton-filtrating membrane measurement. Raman mapping technique identifies the presence of hydrogenated HO─Sr bonds, providing further evidence for proton conduction. And its interfacial conduction is comparatively analyzed with a directly-mixing TiO2-SrTiO3 composite electrolyte. Consequently, a single fuel cell based on the TiO2-SrTiO3@TiO2 heterogeneous electrolyte delivers a good peak power density of 799.7mW cm-2 at 550°C. These findings highlight a dexterous nano-heterointerface design strategy of highly proton-conductive electrolytes at reduced operating temperatures for SOFC technology.

Utilizing phytochemical-rich spent coffee ground extract for eco-friendly ZnO electrochemical synthesis: Assessing photocatalytic efficacy in 2,4-dichlorophenol degradation

The study explores an alternative electrolyte derived from spent coffee ground (SCG) extract for electrochemical synthesis of zinc oxide (ZnO), aiming to address limitations associated with toxic electrolytes. Three extraction methods specifically, facile, microwave-assisted, and ultrasonic-assisted, were employed to prepare SCG extracts, resulting in ZnO-F, ZnO-MW, and ZnO-UAE, respectively. An organic solvent-mediated catalyst, ZnO-DMF, was synthesized using N, N-dimethylformamide, and served as a comparison. All catalysts were characterized via FTIR, SEM, XRD, BET, PSA, XPS and UV-DRS. The photocatalytic activity was evaluated under visible light through 2,4-dichlorophenol (2,4-DCP) degradation. The facile extraction method yielded the most phytochemical-rich SCG extract, leading to the highest catalytic activity of ZnO-F (92.6 %), followed by ZnO-MW (89.2 %) and ZnO-UAE (83.4 %). Notably, ZnO-DMF exhibited similar degradation efficiency (92 %) to ZnO-F. The ZnO-F’s smaller particle size distribution (Dv [90] = 186 µm) and smaller band gap energy (Eg, 3.18 eV) accredited to phytochemicals involvement during electrosynthesis, compensated its poor crystallinity (relative to ZnO-DMF) hence resulting in equivalent photocatalytic capacity with the organic solvent-mediated ZnO. Further optimization using ZnO-F identified pH 3, 30 ppm of 2,4-DCP, and 0.01 g of catalyst loading as the optimal conditions. The reusability test revealed that ZnO-F can be reused for a maximum of 3 cycles with 80 % degradation at the final cycle. Kinetic and scavenger studies revealed a pseudo-first-order degradation mechanism and photogenerated holes as the main species influencing 2,4-DCP degradation, respectively. This investigation accentuates the potential of SCG extract as a green electrolyte for eco-friendly ZnO synthesis with promising photocatalytic applications.

Characterization of Degradation Mechanisms of Alternative Electrolytes Solutions in Fast Charging Li-Ion Batteries

While the idea that fast charging batteries could be utilized in electric vehicles is enticing, current fast charging batteries face significant challenges that must be mitigated before this application is realized. Fast charging batteries currently suffer from capacity loss and degradation over time which not only affects battery life but poses a safety hazard. The current electrolyte, 1.2 M LiPF6 in 3:7 wt.% EC/EMC (Gen2), contains the salt LiPF6 that when exposed to moisture can form dangerous hydrofluoric acid and contains a carbonate-based solvent that when exposed to oxygen can ignite. In addition, batteries experience degradation over many cycles of fast charging which results in capacity fade and poor battery performance. However, previous studies have shown the potential for other electrolyte systems to mitigate these problems, specifically by using highly concentrated electrolytes1. These studies claim that using these electrolytes results in the formation of a solid electrolyte interphase (SEI) that passivates Li ions better than the Gen2 electrolyte. The SEI is a layer that forms on the anode within the battery and serves as a protective layer that allows for Li intercalation into graphite and can therefore protect against degradation. By using different electrolytes, a different SEI is formed, and different degradation mechanisms are observed. In this way, the SEI can be tuned to improve Li passivation and ionic conductivity by changing the electrolyte’s composition and concentration2. This research focuses on such alternative electrolyte systems and aims to characterize the different degradation mechanisms corresponding to each electrolyte. Favorable performance has been observed using 1.2 M LiFSI in 3:7 wt.% EC/EMC as an electrolyte. We are studying LiFSI in acetonitrile (AN) at higher concentrations than traditional Gen2 to quantify the SEI. We expect AN to form an anion derived SEI, a composition of which results in improved passivation of Li ions1. In this study, we characterize degradation of alternative electrolyte systems through x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through these methods we can observe and quantify both crystalline, amorphous degradation products due to loss of Li inventory and loss of active material. XPS allows quantification of compositional changes in the SEI layer at the surface of the electrode. The SEM provides qualitative information on degradation such as visualizing lithium plating and dendrite formation. We implement quantitative XRD to measure the crystalline phases of the graphite anode, showing the degree of lithium intercalation and further quantifying degradation such as Li plating. Putting the results of these three characterization techniques together in tandem with electrochemical cycling data paints a picture of the degradation that happens on the anode of a fast-charging lithium-ion battery with respect to electrolyte composition.[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E., & Yamada, A. (2019). Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy. [2] Logan, E. R., & Dahn, J. R. (2020). Electrolyte Design for Fast-Charging Li-ion Batteries. Trends in Chemistry.

Solving ZIB Challenges: The Dynamic Role of Water in Deep Eutectic Solvents Electrolyte

Zinc-Ion batteries (ZIBs) are considered one of the most promising technologies in the realm of post-lithium-ion batteries. Rechargeable chemistries with zinc anodes hold significant technological potential due to their high theoretical energy density, lower manufacturing costs, abundant raw materials, and inherent safety. ZIBs typically feature neutral or weakly acidic aqueous electrolytes and exhibit typical drawbacks of Zn anodes: hydrogen evolution, passivation, and shape changes.In aqueous electrolytes, two types of water molecules can be described: free water molecules and solvated water molecules that participate in Zn2+ solvation structure [Zn(H2O)6]2+. The free water easily reacts with metallic Zn at the electrode/electrolyte interface, leading to the aforementioned irreversibilities. Alternative electrolytes such as Deep Eutectic Solvents (DESs) can be used to modulate Zn solvation shell, preserving the green and safe characteristics of aqueous-based ones. DESs show relevant characteristics for battery applications, such as low vapor pressure, good thermal and chemical stability, non-flammability, easy moldability, wide electrochemical window, and structured interface. However, a main drawback for electrochemical applications is the high viscosity, low diffusivity, and sluggish kinetics.Water molecules can be added as a cosolvent to eutectic mixtures to increase the diffusion coefficient of electroactive species and reduce the electrolyte viscosity without destroying the eutectic nature by up to 40%. The hydration percentage of DES can modify the thickness of the electrolyte-electrode interface and the Zn2+ solvation structure. Thus, the tuning capability, on one hand, of the solution chemistry of Zn2+ containing electroactive species, and on the other hand, of the electrode–electrolyte interfacial structure and chemistry by the combined use of DES and water provides a flexible tool to control Zn plating and stripping processes.In this study, we investigate the electrochemistry of Zn in ethaline DES with different percentages of water (0%, 5%, 10%, 25%, 50%, 70%, respectively), transitioning from a water-in-salt structure to a salt-in-water one. Fundamental electrokinetic and electrocrystallization studies based on cyclic voltammetry and chronoamperometry at different cathodic substrates were complemented with galvanostatic cycling tests of Zn|Zn symmetric CR2032 coin cells, SEM imaging of electrodes, and in situ Surface Enhanced Raman spectroscopy (SERS).Moreover, the Zn solvation structure was investigated using spontaneous Raman spectroscopy . The employed methodology provided valuable insights into the Zn plating reaction. Water molecules are present in a "confined" state rather than a free one, directly interacting with choline cations and being trapped in the eutectic framework if the molar fraction is kept below 40%.When ZnSO4 is dissolved in anhydrous ethaline, the [ZnCl4]2− species is formed and stabilized by choline. The peculiarities of Zn2+ coordination were found to result in unusual voltammetric behavior, characterized by a cathodic peak in the cathodic branch of the anodic-going scan.Although tetrachlorozincate is the dominant species, it does not seem to be the complex from which Zn is deposited; indeed, [ZnCl4]2− has a very negative reduction potential. Mechanistic studies of Zn electrodeposition onto different cathodic materials have concluded that the metal is formed by the reduction of an intermediate Zn-containing species. The two organic components of the eutectic solvents can be dehydrogenated at a negative potential, forming RO-, which can replace one or more chloride ligands in [ZnCl4]2−.Hydrated DES exhibits faster kinetics, which, in turn, leads to a lower nucleation overpotential. This phenomenon has been explained with two different mechanisms occurring at the same time. Firstly, by increasing the hydration percentage in the eutectic framework, the coordination of Zn2+ changes, forming [ZnCl3(H2O)]-. The water molecule in the Zn2+ sheath has a lower energy barrier than chlorine in the step-by-step desolvation of Zn2+. Consequently, the [ZnCl3(H2O)]- complex exhibits a lower dissociation energy than [ZnCl4]2- present in anhydrous ethaline, resulting in a faster desolvation process that can reduce nucleation overpotentials.Secondly, water molecules hydrogen-bonded to DES components can be reduced at cathodic potential, forming H· radicals that can then participate in the decomposition of the organic component. This apparent side reaction can aid in the formation of RO- ligands that participate in the Zn-species undergoing reduction, thereby increasing the amount of reactants.This multi-technique approach, also applicable to the study of new electrolytes, leads to the optimization of DES hydration, reducing the presence of free water and addressing the main drawbacks associated with eutectic electrolytes. The nuanced understanding of the interplay between solvent composition, Zn solvation, and electrodeposition mechanisms paves the way for the development of more efficient and sustainable ZIB technologies. Figure 1

(Invited) Overview of Ion-Conducting Polymer Membranes and Membrane Separators for Water Electrolysis

Traditional liquid alkaline electrolyzer uses a porous diaphragm to allow diffusion of hydroxide ion from a feed of concentrated KOH solution while separating anode and cathode and suppressing mixing of produced H2 and O2 gases. Although liquid alkaline electrolyzer is considered as a matured technology, recent renaissance of new electrode separators suggests there is significant potential for improvement in efficiency and cost reduction by lowering area specific resistance and increasing operation current density.Ion-conducting polymers (e.g., proton or hydroxide) are used as a key component of polymer electrolyte membranes, such as acidic proton exchange membrane (PEM) and alkaline anion exchange membrane (AEM), in electrochemical energy conversion and storage technologies including water electrolyzers. For example, the state-of-the-art PEM electrolyzers have used Nafion for a PEM and ionomer catalyst binder for decades, though it is not ideal proton-conducting membrane material for those applications. Recent pressure on perfluoroalkyl substrates (PFASs) from government and environmental activist groups due to their environmental and health hazard has attracted the development of alternative polymer electrolyte membranes based on hydrocarbon polymers within electrochemical society. Compared to perfluorosulfonated Nafion, hydrocarbon ion-conducting polymers (both PEMs and AEMs) can offer advantages of flexible synthetic tunability, lower gas permeability, and importantly lower production cost.In this tutorial, an overview of recent progress in the development of advanced porous membrane separators, PEMs and AEMs, their key membrane properties, and the state-of-the-art performance in applications of water electrolyzers will be discussed. Figure 1

Colloid Electrolyte Containing Li3P Nanoparticles for Highly Stable 4.7 V Lithium Metal Batteries.

Lithium metal batteries (LMBs) with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes have garnered significant interest as next-generation energy storage devices due to their high energy density. However, the instability of their electrode/electrolyte interfaces in regular carbonate electrolytes (RCEs) results in a rapid capacity decay. To address this, a colloid electrolyte consisting of Li3P nanoparticles uniformly dispersed in the RCE is developed by a one-step synthesis. This design concurrently creates stable cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) on both electrode surfaces. The cathode interface derived from this colloid electrolyte significantly facilitates the decomposition of Li salts (LiPF6 and LiDFOB) on the cathode surface by weakening the P-F and B-F bonds. This in situ formed P/LiF-rich CEI effectively protects the NCM811 cathode from side reactions. Furthermore, the Li3P embedded in the SEI optimizes and homogenizes the Li-ion transport, enabling dendrite-free Li deposition. Compared to the RCE, the designed colloid electrolyte enables robust cathode and anode interfaces in NCM811||Li full cells, minimizing gas and dendrite formation, and delivering a superior capacity retention of 82% over 120 cycles at a 4.7 V cutoff voltage. This approach offers different insights into electrolyte regulation and explores alternative electrolyte shapes and formulations.

The Interactions between Ionic Liquids and Lithium Polysulfides in Lithium-Sulfur Batteries: A Systematic Density Functional Theory Study.

Ionic liquids (ILs) based on hybrid anions have recently garnered attention as beguiling alternative electrolytes for energy storage devices. This attention stems from the potential of these asymmetric anions to reduce the melting point of ILs and impede the crystallization of ILs. Furthermore, they uphold the advantages associated with their more conventional symmetric counterparts. In this study, we employed dispersion-corrected density functional theory (DFT-D) calculations to scrutinize the interplay between two hybrid anions found in ionic liquids [FTFSA]- and [MCTFSA]- and the [C4mpyr]+ cation, as well as in lithium polysulfides in lithium-sulfur batteries. For comparison, we also examined the corresponding ILs containing symmetric anions, [TFSA]- and [FSA]-. We found that the hybrid anion [MCTFSA]- and its ionic liquid exhibited exceptional stability and interaction strength. Additionally, our investigation unveiled a remarkably consistent interaction between ionic liquids (ILs) and anions with lithium polysulfides (and S8) during the transition from octathiocane (S8) to the liquid long-chain Li2Sn (4 ≤ n ≤ 8). This contrasts with the gradual alignment observed between cations and lithium polysulfides during the intermediate state from Li2S4 to the solid short-chain Li2S2 and Li2S1. We thoroughly analyzed the interaction mechanism of ionic liquids composed of different symmetry anions and their interactions with lithium polysulfides.