Tetraglyme Research Articles

Phthalocyanine-based bifunctional soluble hybrid catalyst for rechargeable lithium-oxygen batteries

A mixture of tetrabutylammonium lithium phthalocyanine (TBA-LiPc) and dilithium phthalocyanine (Li2Pc) (2:1 mol ratio) functions as a bifunctional soluble hybrid catalyst in tetraethylene glycol dimethyl ether (TEGDME) for a rechargeable lithium-oxygen cell. Cyclic voltammetry (CV) measurements of the hybrid catalyst in TEGDME show highly symmetrical peaks at 2.54 V and 3.22 V vs Li/Li+ corresponding to oxygen reduction and oxygen oxidation reactions, respectively. Long-term cycling of cells with PVP-modified graphene nanosheets (GNSs) coated hierarchical porous carbons (HPC) cathodes at a fixed capacity of 1200 mAh/g (carbon) exhibits 402 and 379 cycles in oxygen and dry-air, respectively.

Basic properties of glyme-based electrolytes doped with lithium 2,4,5-tricyanoimidazolide (LiTIM)

The article presents the electrolyte's basic physicochemical and electrochemical properties based on the new type of lithium salt for lithium batteries - lithium 2,4,5-tricyanoimidazolide (LiTIM). Two series of the electrolytes in diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether were obtained and their electrochemical properties were examined by means of impedance spectroscopy and cyclic voltammetry. Thermal and rheological properties of the electrolytes were tested with differential scanning calorimetry (DSC) and rheometric methods. Single crystal X-ray analysis was performed for LiTIM-crown ethers adducts used as models for solvent-separated and solvent-shared ionic species. Raman spectroscopy was used to obtain a more detailed insight into ionic interactions in the material. The electrochemical stability for the tetraglyme based electrolytes with a salt concentration higher than 0.4 M was 4.7 V vs Li. The high solubility of LiTIM in tetraglyme (up to 6.8 M) and the ability to form an amorphous, stable solution make the electrolyte an interesting candidate for advanced lithium batteries.

A sodium ion conducting gel polymer electrolyte with counterbalance between 1-ethyl-3-methylimidazolium tetrafluoroborate and tetra ethylene glycol dimethyl ether for electrochemical applications.

For sodium batteries, the development of gel polymer electrolytes (GPEs) with remarkable electrochemical properties is in its early stage and persists to be a challenge. In this report we have synthesized a series of GPEs containing a poly(vinyllidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and poly (methyl methacrylate) (PMMA) as blend polymer, sodium perchlorate (NaClO4) as ion-conducting salt and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) and tetra ethylene glycol dimethyl ether (TEGDME) as molecular solvents. The counter balance between EMIM-BF4 and TEGDME is maintained by the electrolyte, which is formed through the optimal weight ratio of 2 : 1. GPEs have an advantageous set of properties, including stability window of 5 V, Na+ transference number of 0.20, and a room-temperature ionic conductivity of 5.8 × 10-3 S cm-1. According to enthalpy and entropy calculations, optimized GPE yields the highest amount of disorder or amorphicity and contributes to greatest conductivity. XRD analysis supports this argument. Thermal investigations show that optimized GPE may preserve gel phase up to 125 °C. The prototype sodium cell fabricated with optimize GPE has a specific capacity of 281 mA h g-1 and open circuit voltage of 2.5 V. The optimized GPE exhibits potential for future electrochemical applications.

Nature of Li2O2 and its relationship to the mechanisms of discharge/charge reactions of lithium-oxygen batteries.

Lithium-air batteries (LABs) are considered one of the most promising energy storage devices because of their large theoretical energy density. However, low cyclability caused by battery degradation prevents its practical use. Thus, to realize practical LABs, it is essential to improve cyclability significantly by understanding how the degradation processes proceed. Here, we used online mass spectrometry for real-time monitoring of gaseous products generated during charging of lithium-oxygen batteries (LOBs), which was operated with pure oxygen not air, with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) tetraethylene glycol dimethyl ether (TEGDME) electrolyte solution. Linear voltage sweep (LVS) and voltage step modes were employed for charge instead of constant current charge so that the energetics of the product formation during the charge process can be understood more quantitatively. The presence of two distinctly different types of Li2O2, one being decomposed in a wide range of relatively low cell voltages (2.8-4.16 V) (l-Li2O2) and the other being decomposed at higher cell voltages than ca. 4.16 V (h-Li2O2), was confirmed by both LVS and step experiments. H2O generation started when the O2 generation rate reached a first maximum and CO2 generation took place accompanied by the decomposition of h-Li2O2. Based on the above results and the effects of discharge time and the use of isotope oxygen during discharge on product distribution during charge, the generation mechanism of O2, H2O, and CO2 during charging is discussed in relation to the reactions during discharge.

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

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

Designing Fluorine-Free Electrolytes for Practical Sodium Metal Anodes and Seawater Batteries

Fluorine (F) is regarded as a key element in electrolytes for sodium metal anodes (SMAs) because of the formation of NaF containing solid–electrolyte interphase (SEI) layers; however, the high-cost and HF formation issues experienced by F-based electrolytes should be addressed. Herein, F-free, cost-effective 1 M NaBH4/ether-based electrolytes are proposed, motivated by the recent speculation that NaH is a “good SEI layer.” The time-of-flight secondary ion mass spectrometry (TOF-SIMS) results of sodium metal electrodes after galvanostatic cycling demonstrated that NaH is a major component of the SEI layer. In addition, the native oxide surface of sodium was converted into NaH and NaBO2 after soaking in the electrolytes, implying that “SEI reconstruction” occurred by chemical reduction. Accordingly, significantly longer cyclability was obtained in the Na‖Na symmetric cell (1200 h, 1 mA cm−2, 1 mA h cm−2) than in F-based electrolytes. In seawater batteries (SWBs), 1 M NaBH4/DEGDME (diethylene glycol dimethyl ether) delivers higher power density (2.82 mW cm−2 vs. 2.27 mW cm−2) and cyclability (300 h vs. 50 h) under 1 mA cm−2 than 1 M NaOTf/TEGDME (tetraethylene glycol dimethyl ether), which is commonly used in SWBs. In conclusion, two novel contributions of this study include the demonstration that NaH can work as a “good SEI layer” apart from NaF and the proposal of a cost-effective, F-free electrolyte for practical and large-scale SWBs.

Ionic Liquid - Glyme Mixtures to Modify Solvation Chemistry, Electrochemical and Physiochemical Properties in Lithium Containing Electrolytes

Pyrrolidinium-based ionic liquids are an intriguing material for lithium-based battery electrolytes due to their inherit non-flammability and large electrochemical windows. Poor lithium-ion transport in ionic liquid-based electrolytes hinder the effectiveness of these electrolytes. Solvate ionic liquids were introduced as a subclass of ionic liquids consisting of high concentrations of lithium salts and glymes. For example, the solvate ionic liquid Li(G4)TFSI is an equimolar ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (G4). In this work, pyrrolidinium-based ionic liquids containing short polyether side chains, structurally analogous to glymes, are mixed with equimolar amounts of LiTFSI and varying portions of G4. These tertiary mixtures were evaluated based on the ratio of solvating oxygen to lithium ion ([O]/[Li+]) present in the mixture. Trends in the oxidative stability, conductivity and lithium transference number were evaluated from mixtures of [O]/[Li+] between 5 to 8. Oxidative stability of tertiary mixtures with [O]/[Li+] = 5 showed improved oxidative stability compared to the binary Li(G4)TFSI, while [O]/[Li+] > 5 had diminished oxidative stability. DSC thermal analysis between -85°C to +120°C showed the tertiary mixtures helped suppress the glass transition temperature of Li(G4)TFSI to lower temperatures. Changes in the solvation structures were evaluate using spectroscopic analysis, including Raman spectroscopy. The changes in the solvation chemistry were correlated to the physiochemical and electrochemical properties.

Poor Cycling Performance of Rechargeable Lithium–Oxygen Batteries Under Lean-Electrolyte and High-Areal-Capacity Conditions: Role of Carbon Electrode Decomposition

There has been considerable interest in developing rechargeable lithium oxygen batteries (LOBs) that have the potential to significantly exceed the energy density limit of a Li ion battery (approximately 300 Wh/kg). Although 500 Wh/kg LOB has been demonstrated and exhibited stable discharge/charge cycle at room temperature condition1, their cyclability remains less than 10 cycle. For realizing the LOB with practically high energy density and long cycle life, the deep understanding of complicated reaction in LOBs has been highly demanded. Especially, the problems specifically associated with the limited electrolyte (“lean-electrolyte”) conditions need to be taken into account in LOBs.Although the importance of investigating negative lithium electrodes in lean-electrolyte systems has been recognised in recent years2,3, specific problems associated with the negative lithium electrode in a LOB has not been investigated so far. In particular, chemical crossover from the positive electrode to the negative electrode is a crucial factor that needs to be taken into consideration. Actually, recent studies have shown that LiOH is formed on the surface of a lithium-metal electrode through reaction with H2O in the electrolyte4,5. This H2O is generated by the decomposition of the tetraethylene glycol dimethyl ether (TEGDME) solvent at the positive oxygen electrode, which then migrates to the negative electrode side to react with the lithium-metal electrode. Consequently, problems related to chemical crossover are prominent in lean-electrolyte LOBs, where the effective water concentration in the electrolyte is much higher than that in an excess electrolyte system.Despite the importance of investigating the reaction of negative lithium electrodes in LOB with appropriate technological parameters, mechanistic details remains unclear due to the technical difficulty for applying non-destructive analytical methods. In the present study, we investigated the reaction of a negative lithium electrode in a lean-electrolyte LOB operating under high areal capacity conditions. The use of advanced non-destructive analytical methods, including three-electrode electrochemical techniques and an in-situ analytical setup revealed that the reaction efficiency of the lithium electrode mostly decreases through chemical crossover from the positive oxygen electrode6. In particular, the H2O generated as a side-product at the positive oxygen electrode crosses over to the negative electrode side and reacts with the lithium-metal electrode to form a porous LiOH/Li2CO3 layer on the electrode surface. LiOH and Li2CO3 accumulates, and the porous layer thickens through repeated discharge/charge cycling, which supresses efficient Li-ion transport through the layer.Furthermore, using a solid-state ceramic-based separator to protect the lithium-metal negative electrode, the side reaction with the negative electrode was considerably suppressed, which helped exclusively assess the degradation phenomena occurring in the oxygen positive electrode. By series of in-situ and ex-situ analysis revealed the following points: (i) Although the electrolyte degradation intensified with increasing repeated discharge/charge cycling, the scarcity of the electrolyte minimally influenced the cycle life of the LOBs. (ii) Most of the Li2CO3-like solid-state side products decomposed during charging at voltages higher than 3.8 V. (iii) Severe decomposition of the carbon electrode occurred during cycling, and an equivalent amount of CO2 was generated during charging at voltages higher than 3.8 V. Because the carbon electrode used in these experiments merely decomposed via simple electrochemical oxidation at voltages up to 4.5 V, the carbon electrode was considered to deteriorate through the decomposition of its solid-state side products. The findings of this study are anticipated to guide future investigations on the advancement of LOBs. In particular, detailed understanding of the reaction at the interface between the carbon electrode and solid-state products is crucial for realizing practical high-energy-density LOBs with long cycle life.

Toward Sustainable Li-S Battery Using Scalable Cathode and Safe Glyme-Based Electrolyte.

The search for safe electrolytes to promote the application of lithium-sulfur (Li-S) batteries may be supported by the investigation of viscous glyme solvents. Hence, electrolytes using nonflammable tetraethylene glycol dimethyl ether added by lowly viscous 1,3-dioxolane (DOL) are herein thoroughly investigated for sustainable Li-S cells. The electrolytes are characterized by low flammability, a thermal stability of ∼200 °C, ionic conductivity exceeding 10-3 S cm-1 at 25 °C, a Li+ transference number of ∼0.5, electrochemical stability window from 0 to ∼4.4 V vs Li+/Li, and a Li stripping-deposition overpotential of ∼0.02 V. The progressive increase of the DOL content from 5 to 15 wt % raises the activation energy for Li+ motion, lowers the transference number, slightly limits the anodic stability, and decreases the Li/electrolyte resistance. The electrolytes are used in Li-S cells with a composite consisting of sulfur and multiwalled carbon nanotubes mixed in the 90:10 weight ratio, exploiting an optimized current collector. The cathode is preliminarily studied in terms of structure, thermal behavior, and morphology and exploited in a cell using standard electrolyte. This cell performs over 200 cycles, with sulfur loading increased to 5.2 mg cm-2 and the electrolyte/sulfur (E/S) ratio decreased to 6 μL mg-1. The above sulfur cathode and the glyme-based electrolytes are subsequently combined in safe Li-S batteries, which exhibit cycle life and delivered capacity relevantly influenced by the DOL content within the studied concentration range.

An efficient upcycling of graphite anode and separator for Na-ion Batteries via solvent-co-intercalation process

The need for efficient energy storage devices has led to a boom in Li-ion battery production, which will be a threat in the future to the global ecosystem in the form of toxic waste if not recycled properly. Herein, we report the electrochemical performance of recycled and fresh polyolefin separators in a glyme-based electrolyte for a recovered graphite/Na3V2(PO4)3-based Na-ion full-cell. An in-depth investigation of the electrolyte stability with tetraethylene glycol dimethyl ether and diethylene glycol dimethyl ether-based electrolytes and the compatibility with polyolefin separators has been done, with successful sodium-plating stripping for 350+ hours. Cycling stabilities with >99.9 % Coulombic efficiency for 250+ cycles have been observed in both half-and full-cell configurations, with robust capacity retention for the full-cell at a current of 1 A g−1.

Polymer gel electrolytes containing sodium salts with BF4−, ClO4− and CF3SO3− anions immobilized in TEGDME molecular liquid for sodium battery and electric double layer capacitor

The present study reports synthesis and analysis of different characteristics of sodium ion conducting polymer gel electrolytes (PGEs) containing sodium salts with BF4−, ClO4− and CF3SO3− anions dissolved in tetraethylene glycol dimethyl ether and immobilized in a copolymer matrix consisting of polymethyl methacrylate and poly(vinylidene fluoride-co-hexafluoropropylene). The PGE containing the NaBF4 salt could deliver an ionic conductivity of 1.4 × 10−3 S cm−1 at room temperature along with superior dielectric properties as compared to the electrolytes with NaClO4 and NaCF3SO3 salts. The feasibility of designing sodium-based batteries and EDLCs has been demonstrated using the optimized PGE containing NaBF4 salt. The prototype sodium‑sulfur (NaS) battery designed by utilizing the optimized PGE, sodium amalgam anode and sulfur cathode provides open circuit voltage of ∼2.4 V and initial discharge capacity of ∼163 mA h g−1 and 126 mA h g−1 at discharge currents of 33 mA g−1 and 66 mA g−1, respectively. This optimized PGE also demonstrate good compatibility with AC electrodes in electric double layer capacitor (EDLC) application and delivered a significant specific capacity ∼64 F g−1 at 0.5 mA cm−2 current.

Enhancing the Performance of Lithium-Oxygen Batteries with Quasi-Solid Polymer Electrolytes.

The quasi-solid electrolyte membranes (QSEs) are obtained by solidifying the precursor of unsaturated polyester and liquid electrolyte in a glass fiber. By modifying the ratio of tetraethylene glycol dimethyl ether, QSE with balanced ionic conductivity, flexibility, and electrochemical stability window is acquired, which is helpful for inhibiting the decomposition of electrolyte on the cathode surface. The QSE is beneficial to the interfacial reaction of Li+, electrons, and O2 in the quasi-solid lithium-oxygen battery (LOB), can reduce the crossover of oxygen to the anode, and extend the cycle life of LOBs to 317 cycles. Benefitting from the application of QSE, a more stable solid electrolyte interface layer can be constructed on the anode side, which can homogenize Li+ flux and facilitate uniform Li deposition. Lithium-oxygen pouch cell with in situ formed QSE2 works well when the cell is folded or a corner is cut off. Our results indicate that the QSE plays important roles in both the cathode and Li metal anode, which can be further improved with the in situ forming strategy.

Mitigating water-related challenges in aqueous zinc-ion batteries through ether-water hybrid electrolytes

Aqueous zinc-ion batteries (AZIBs) are an attractive option for different energy storage applications due to their cost-effectiveness, safety benefits, and high capacity. Nevertheless, their development is constrained by challenges such as hydrogen evolution reaction (HER), significantly affecting the battery lifespan. This work presents a promising solution to this problem using a hybrid electrolyte, consisting of water and tetra ethylene glycol dimethyl ether (TEGDME) containing Zn(OTf)2. Results demonstrate that this hybrid electrolyte can suppress HER and can lessen zinc corrosion by reorienting hydrogen bonds with water and actively participating in the solvation structure of Zn2+ ions. Such reorientation reduces water activity and weakens the interactions between water molecules and between water and Zn2+ ions. By employing an optimal TEGDME/H2O ratio of 2:1 in the hybrid electrolyte, hydrogen evolution overpotential increased by 0.26 V. As a result, in the Zn//Zn symmetrical cells, the developed hybrid electrolyte is seen to enable the Zn electrode to exhibit excellent cycle durability, lasting over 4300 h with coulombic efficiency (CE) of 99.68% at 0.5 mA cm−2 and 0.5 mAh cm−2, surpassing the 92.79% achieved by the base electrolyte (1 M Zn(OTf)2 aqueous solution) cells. Moreover, when implemented in Zn/δ-MnO2 batteries, the hybrid electrolyte maintained its performance for over 1800 cycles at a discharge rate of 100 mA g−1. This cost-effective and adaptable strategy highlights its wide-ranging potential, offering vital insights for the enhancement of AZIB technology.

Comparative study of different lithium salts as electrolyte additives of Li/SiOx–Si–C half-cells for lithium sulfur batteries

Silicon oxide and its derivatives (SiOx, 0 < x < 2) are drawing significant interest as electrode material for Li-ion and Li–S batteries owing to their unique properties of high specific capacity, low working potential, high abundance, and environmental friendliness. In-depth research is done on the effects of electrolyte additives on the electrochemical and interfacial characteristics of SiOx-based anodes for Li–S batteries. Two different electrolyte additives namely lithium bis (fluorosulfonyl imide) (LiFSI) and lithium bis (oxalatoborate) (LiBOB) were incorporated in the supporting electrolyte containing 1 M lithium bis (trifluoromethanesulfonyl imide) (LiTFSI) in tetraethylene glycol dimethyl ether (TEGDME): 1,3 dioxolane (DOL) in the ratio of 1:1 (v/v). The Li/SiOx–Si–C 2032-type half-cells were assembled, and their charge–discharge properties were explored at 0.1 C-rate. Surface morphology and electrochemical impedance investigations of the electrode materials have been performed after cycling. The interfacial properties of SiOx-based electrodes were examined by FTIR and XPS. Among the electrolytes studied LiFSI-added electrolytes offer superior charge–discharge properties, which was attributed to the formation of a stable solid electrolyte interphase (SEI) layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the lithium metal surface. The formation of Li2CO3 and ROCO2Li compounds are identified on lithium surface by XPS data and complemented by NMR analysis.

Inhibiting Vanadium Dissolution of Potassium Vanadate for Stable Transparent Electrochromic Displays

Vanadium oxides are highly valued as electrochromic materials because of their multicolor capabilities. However, their practical applications have been limited due to challenges such as the dissolution of vanadate into aqueous electrolytes, leading to poor long‐term stability. Herein, a solution is proposed to the vanadate dissolution issue by utilizing a hybrid electrolyte consisting of tetraethylene glycol dimethyl ether (TEGDME) and water. This electrolyte has the unique ability to form a robust cathode electrolyte interface layer on vanadium oxide electrodes. As a proof of concept, zinc‐anode‐based multicolor transparent electrochromic displays are prepared using layered potassium vanadate (K2V6O16·1.5H2O, KVO) with a TEGDME–water hybrid electrolyte. By soaking the KVO electrode in the hybrid electrolyte, it is demonstrated that KVO has remarkable stability against dissolution. Furthermore, it is shown that KVO has superior electrochromic performance compared to sodium vanadate (NaV3O8·1.5H2O, SVO), due to the wide KVO interlayer spacing. Given the enhanced performance of this hybrid electrolyte and KVO cathode material, a zinc‐anode‐based electrochromic display prototype is shown to exhibit compelling performance. As such, this work is expected to be a significant catalyst for accelerating the development of vanadate‐based electrochromic displays.

Solvation Structure with Enhanced Anionic Coordination for Stable Anodes in Lithium‐Oxygen Batteries

AbstractLi‐O2 batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation‐regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li‐O2 batteries. Trifluoroacetate anions (TFA−) with strong Li+ affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li+‐G4 interaction and form anion‐dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic‐rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol−1, compared with 1.0 M LiTFSI/G4, for facile interfacial Li+ diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li‐O2 battery with a limited Li anode (7 mAh cm−2). This work gains comprehensive insights into rational electrolyte design for Li‐O2 batteries.

Solvation Structure with Enhanced Anionic Coordination for Stable Anodes in Lithium-Oxygen Batteries.

Li-O2 batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation-regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li-O2 batteries. Trifluoroacetate anions (TFA-) with strong Li+ affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li+-G4 interaction and form anion-dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic-rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol-1, compared with 1.0 M LiTFSI/G4, for facile interfacial Li+ diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li-O2 battery with a limited Li anode (7 mAh cm-2). This work gains comprehensive insights into rational electrolyte design for Li-O2 batteries.

Ultrathin PEO based electrolyte for high voltage lithium metal batteries enabled by polymer host-plasticizer interactions

Poly(ethylene oxide) (PEO) stands out in solid-state Li metal batteries (SSLMBs) for its high viability, low expanse and superior compatibility with Li anode, but its insufficient ionic conductivity at ambient temperature and limited electrochemical stability windows make it difficult to work at ambient temperature and pair with high voltage cathode materials. Herein, an ultrathin dual-solvent PEO based polymer electrolyte (DSPE) with 22 μm is proposed to tackle these issues. The introduction of tetraethylene glycol dimethyl ether (TEGDME) and succinonitrile (SN) as plasticizers friendly to Li anode and NCM622, respectively, not only greatly improves the conductivity of PEO at room temperature, but also significantly enhances the compatibility of electrolyte-electrode interface. More importantly, the PEO polymer host-solvent interactions successfully anchor the free solvent small molecules of TEGDME and SN around PEO host to avoid their damage to the electrolyte-electrode interface. Improved NCM622|DSPE|Li battery provides prominent cycle life with a capacity retention of 80.0 % after 300 cycles at 0.1C at 30 °C. The application of PEO based polymer electrolyte in SSLMBs is successfully realized by taking advantage of polymer host-plasticizer interactions.

Systematic Study of O2 Supply in Li–O2 Batteries with High and Low Doner Number Solvents

The Li–O2 battery is a promising technology due to its high theoretical specific energy. However, its practical capacity and cycling performance need further improvement. In this scenario, the influence of the electrolyte and the supply of air/O2 to the device are essential to enhance the performance and build a commercial prototype. This paper presents a study focusing on the influence of oxygen flow and pressure in the gravimetric capacity of Li–O2 batteries using two different electrolytes: dimethyl sulfoxide (DMSO/LiClO4) and tetraethylene glycol dimethyl ether (TEGDME/LiClO4). This study pointed out the negative influence of flow over the capacity when combined in an open cell. Due to electrolyte loss, the life cycle was also deeply affected using the open cell, especially for DMSO. However, DMSO leads to the best performance due to higher ionic conductivity, oxygen diffusivity, and absence of a direct reaction with the lithium anode. Thus, the closed cell reached a maximum discharge capacity of 22537 mAh g–1 with 26 cycles of 1000 mAh g–1 for DMSO and 8764 mAh g–1 with 13 cycles of 1000 mAh g–1 for TEGDME.

Elucidation of Losses in Cycling Lithium-Metal Anodes in Ether-Based Electrolytes

Electrified-mobility and renewable-energy markets have undergone many developments in recent years and triggered an increase in demand for power-supply improvements, especially for full-electric vehicles (EVs). Rechargeable lithium-metal batteries have been considered one of the most attractive next-generation energy-storage systems (ESS). Many Li-chemistry-based ESS such as Li–S and Li–O2 use liquid electrolyte based on ether solvents such as 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL) and tetraethylene glycol dimethyl ether (TEGDME) with bis(-trifluoromethanesulfonyl) imide (LiTFSI) as a salt. This work studied the effects of several parameters, in ether-based electrolytes, on the properties of the SEI and on capacity losses. The effects of LiNO3 additive, current density and cycle number on the total capacity loss (QTL, Qdeposition—Qdissolution), the capacity needed to repair the SEI after dissolution of lithium (QSEIrepair), two types of “dead” lithium, roundtrip coulombic efficiency and on the correlation among them, will be discussed. Elucidation of these phenomena will lead to the improvement of the lithium deposition/dissolution processes in lithium-metal rechargeable batteries. It was found that cells with 1:1 DME:DOL + 2 M LiTFSI and 0.15 M LiNO3 electrolyte composition present the best cycling performance at low current densities, whereas under higher current conditions, the cell based on 1:1 DME:DOL + 2 M LiTFSI without the LiNO3 additive, presents the best cycling performance.