Traditional Liquid Electrolytes Research Articles

Influence of low content metal intermixing on electrochemical stability and sodium ion transport in Na2(Mg2−xZnx)TeO6 (x = 0.125, 1.875) for solid state sodium-ion batteries

Based on solid electrolyte instead of traditional liquid electrolyte, all-solid-state battery technology leads to the next generation of high performance sodium ion batteries. In this work, we propose a metal intermixing in the P2-type layered compounds Na2X2TeO6 (X = Mg, Zn), resulting in Na2(Mg2-xZnx)TeO6 (x=0,0.125,1.875,2), for advanced solid-state electrolyte and Na ion conductor, based on first-principles calculations of electrochemical stability and Na ion diffusion. Our calculations reveal that Zn intermixing in a low content with Mg in Na2Mg2TeO6 can effectively improve the electrochemically stable window and Na ion conductivity, whereas Mg intermixing with Zn in Na2Zn2TeO6 slightly reduces the performance. The atom-resolved electronic density of states and electron density differences are analyzed to give an understanding of performance enhancement or deterioration by intermixing. This work highlights the possibility of improving the performance of metal oxide-based solid electrolyte by intermixing metals.

Computational Characterization of β-Li3PS4 Solid Electrolyte: From Bulk and Surfaces to Nanocrystals

The all-solid-state lithium-ion battery is a new class of batteries being developed following today’s demand for renewable energy storage, especially for electric cars. The key component of such batteries is the solid-state electrolyte, a technology that promises increased safety and energy density with respect to the traditional liquid electrolytes. In this view, β-Li3PS4 is emerging as a good solid-state electrolyte candidate due to its stability and ionic conductivity. Despite the number of recent studies on this material, there is still much to understand about its atomic structure, and in particular its surface, a topic that becomes of key relevance for ionic diffusion and chemical stability in grain borders and contact with the other device components. In this study, we performed a density functional study of the structural and electronic properties of β-Li3PS4 surfaces. Starting from the bulk, we first verified that the thermodynamically stable structure featured slight distortion to the structure. Then, the surfaces were cut along different crystallographic planes and compared with each other. The (100) surface is confirmed as the most stable at T = 298 K, closely followed by (011), (010), and (210). Finally, from the computed surface energies, the Wulff nanocrystals were obtained and it was verified that the growth along the (100) and (011) directions reasonably reproduces the shape of the experimentally observed nanocrystal. With this study, we demonstrate that there are other surfaces besides (100) that are stable and can form interfaces with other components of the battery as well as facilitate the Li-migration according to their porous structures.

All-Solid-State Photo-Assisted Li-CO2 Battery Working at an Ultra-Wide Operation Temperature.

At present, photoassisted Li-air batteries are considered to be an effective approach to overcome the sluggish reaction kinetics of the Li-air batteries. And, the organic liquid electrolyte is generally adopted by the current conventional photoassisted Li-air batteries. However, the superior catalytic activity of photoassisted cathode would in turn fasten the degradation of the organic liquid electrolyte, leading to limited battery cycling life. Herein, we tame the above limitation of the traditional liquid electrolyte system for Li-CO2 batteries by constructing a photoassisted all-solid-state Li-CO2 battery with an integrated bilayer Au@TiO2/Li1.5Al0.5Ge1.5(PO4)3 (LAGP)/LAGP (ATLL) framework, which can essentially improve battery stability. Taking advantage of photoelectric and photothermal effects, the Au@TiO2/LAGP layer enables the acceleration of the slow kinetics of the carbon dioxide reduction reaction and evolution reaction processes. The LAGP layer could resolve the problem of liquid electrolyte decomposition under illumination. The integrated double-layer LAGP framework endows the direct transportation of heat and Li+ in the entire system. The photoassisted all-solid-state Li-CO2 battery achieves an ultralow polarization of 0.25 V with illumination, as well as a high round-trip efficiency of 92.4%. Even at an extremely low temperature of -73 °C, the battery can still deliver a small polarization of 0.6 V by converting solar energy into heat to achieve self-heating. This study is not limited to the Li-air batteries but can also be applied to other battery systems, constituting a significant step toward the practical application of all-solid-state photoassisted Li-air batteries.

High-throughput screening of protective layers to stabilize the electrolyte-anode interface in solid-state Li-metal batteries

Solid-state Li-metal batteries have attracted growing interest over the years as a promising candidate for next-generation energy storage. Yet, the Li metal not only spontaneously reacts with most solid-state electrolytes (SSEs), but also triggers Li dendrite growth in the SSEs at a lower current density than traditional liquid electrolytes. Buffering the electrolyte-anode interface with a protective layer could be a viable solution to this problem. Herein, we search for candidate protective-layer materials from 2316 experimentally known Li-containing compounds using high-throughput first principles calculations. Tiered screening of both stability and electronic structure allows the identification of 5, 28 and 7 materials as suitable for protecting Li7La3Zr2O12, Li3PS4 and LiTi2(PO4)3, respectively. We demonstrate that electron transfer from Li metal to SSE is successfully blocked by the protective layer to restrain the dendrite growth. This work enables a significant reduction of search space for materials discoveries in protective layer for solid-state Li-metal batteries.

Design Considerations for Practical Li-S Battery Components for Electric Aviation

The development of high-energy, high-safety, and high-power batteries beyond electric automobile requirements is vital for future electric aviation applications. The transition to non-volatile solid-state electrolytes (SSE) promises many advantages over traditional flammable liquid electrolytes and may also be an enabling technology for next generation chemistries. However, significant manufacturing challenges must be overcome before the adoption of such technology. This study focuses on advancement of previous electrolyte development to produce sulfide-polymer composites with densified thicknesses between 20-30 microns using a tape-casting technique with an elastomer binder [1]. Parameters such as binder type, binder loading, and filler loading are modified to determine their impact on electrochemical performance and mechanical stability. The composites were determined to retain reasonable ionic conductivity with improved flexibility and scalability critical for practical manufacturing of such cells. Films were produced 10-15 times thinner than comparable bulk powder electrolytes and within the range of commercial polyolefin separators (25 micron) used in commercial liquid containing lithium-ion cells. Composite conductivities were maintained above 0.2mS/cm, which holds promise for future electric aviation applications. Processing techniques are investigated to further improve electrochemical performance.[1] Donald A. Dornbusch, Rocco P. Viggiano, John W. Connell, Yi Lin, Vadim F. Lvovich. Practical considerations in designing solid state Li-S cells for electric aviation, Electrochimica Acta, 2021, 139406, ISSN 0013-4686, https://doi.org/10.1016/j.electacta.2021.139406.

Composite solid electrolytes containing single-ion lithium polymer grafted garnet for dendrite-free, long-life all-solid-state lithium metal batteries

Compared with traditional liquid electrolytes, the composite solid electrolytes (CSE) composed of polymer and inorganic particle fillers show better electrochemical stability and safety in lithium-ion batteries. However, the low lithium ion transference number (tLi+) and filler agglomeration still threat CSE performance. In response to these threats, we proposed a flexible anion-immobilized modified ceramic-polymer composite solid electrolyte, which significantly increased the lithium ion transference number and showed promising performance after assembled in an all-solid-state battery. Primarily, the surface of Ta-doped garnet Li6.4La3Zr1.4Ta0.6O12 (@LLZTO) was modified by a silane coupling agent bearing C = C bonds, then the lithium single-ion polymer (lithium (4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (LiSTFSI)) was chemically grafted onto the above particles resulting in the ceramic-polymer composite particles (Li@LLZTO). These particles can be uniformly distributed in the polyethylene oxide (PEO) matrix to form composite solid electrolyte (PL@LCSE). It is found that the PL@LCSE promotes the dissociation of lithium salt and reduces the crystallinity of PEO, and shows a relatively high restriction on the migration of anions. Therefore, PL@LCSE shows a high ionic conductivity (1.5 mS·cm−1), a wide electrochemical window (∼5.3 V vs. Li/ Li+) and a high tLi+ (0.77). The Li/PL@LCSE/Li battery exhibits long cycle stability (cycling more than 1000 h). Excellent cycling stability and high rate capability are demonstrated in the all-solid-state batteries with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. Consequently, the synthesized garnet-lithium single-ion polymer composite micron particles have great potential in the next generation of all-solid-state lithium metal batteries.

A two-step strategy for constructing stable gel polymer electrolyte interfaces for long-life cycle lithium metal batteries

Due to the high reactivity between the lithium metal and traditional organic liquid electrolyte, the reaction of lithium metal electrode is usually uneven and there are also unexpected side reactions. Therefore, construction of a stable solid electrolyte interface (SEI) is highly essential to improve the performance of lithium metal anode. Herein, a sandwich-like gel polymer electrolyte (GPE) is accurately prepared by in-situ polymerization of Polyacrylonitrile (PAN) nanofiber membrane with trihydroxymethylpropyl trimethylacrylate (TMPTMA) and 1,6-hexanediol diacrylate (HDDA). The resulting GPE with a tightly cross-linked gel skeleton exhibits high ionic conductivity and electrochemical window of 5.6 V versus Li/Li+. In particular, the pretreatment of Li metal anode can improve the interfacial wettability, and the synergy of the chemically pretreated Li metal anode surface and the GPE can electrochemically in situ generate SEI with compositionally stable and fluorine-rich inorganic components. Owing to these unique advantages, the interfacial compatibility between the GPE and lithium metal is greatly improved. Meanwhile, the formed SEI can inhibit the formation of lithium dendrites, and decomposition of GPE would be alleviated. The assembled Li-FEC|GPE|LiFePO4 full cell shows a high initial discharge capacity of 157.1 mA h g−1, and maintains a capacity retention of 92.3% after 100 cycles at 0.2C.

A cross-linked tin oxide/polymer composite gel electrolyte with adjustable porosity for enhanced sodium ion batteries

Solid electrolytes have a great potential to replace traditional flammable liquid electrolytes for lithium/sodium ion batteries. However, the solid electrolytes have a low ionic conductivity and poor interface properties, so it is difficult for them to reach the level of conventional liquid electrolyte systems. We have now built an adjustable porous 3D network structure by contacting PVDF-HFP and SnO2, and optimized the ion conductive path in the gel polymer electrolyte by adding 1-(4-cyanophenyl)-guanidine. PVDF-HFP with a 3D network structure provides a channel for storing and transporting sodium ions, and the imino nitrogen atom of 1-(4-cyanophenyl)guanidine can form a ligand with sodium ions to enhance the conduction of Na+. The gel polymer electrolyte (PSGGSE) thus obtained has an ion conductivity of 0.232 mS cm−1 at 70 °C, and is easy to form a stable interface layer with the anode. Further experiments showed that compared with liquid electrolytes, a more stable interface was formed between PSGGSE and the anode. Cycling tests of Na/PSGGSE/Na symmetric batteries under different current densities showed that no short circuit occurred after 400 h, indicating that the battery could not be short-circuited, and PSGGSE can effectively inhibit the growth of Na dendrites. In addition, the Na/PSGGSE/NiMoO4 battery has an excellent cycling stability at the current density of 100 mA g−1, and still maintains a high capacity of 150 mAh g−1 after 200 cycles, which is much higher than that of liquid electrolytes.

Recyclable, Self-Healing Solid Polymer Electrolytes by Soy Protein-Based Dynamic Network.

Compared to traditional organic liquid electrolytes, which often present leakage, flammability, and chemical stability problems, solid polymer electrolytes (SPEs) are widely regarded as one of the most promising candidates for the development of safer lithium‐ion batteries. Vitrimers are a new class of polymer materials consisting of dynamic covalent networks that can change their topology by thermally activated bond‐exchange reactions. Herein, the recyclable and self‐healing solid polymer electrolytes (SPEs) with a soy protein isolate (SPI)‐based imine bond dynamic network are reported. This malleable covalent cross‐linked network polymer can be reshaped and recycled at high temperature (100 °C) or only with water at ambient temperature (25 °C), which may realize the green processing of energy materials. The introduction of bis(trifluoromethane) sulfonimide lithium (LiTFSI) significantly reinforces the conductivity of the dynamic network to a maximum of 3.3 × 10−4 S cm‐1. This simple and applicable method establishes new principles for designing scalable and flexible strategies for fabricating polymer electrolytes.

High voltage stable solid-state lithium battery based on the nano-conductor imbedded flexible hybrid solid electrolyte with hyper-ion conductivity and thermal, mechanical, and adhesive stability

Hybrid solid electrolyte (HSE) is a potential candidate in lithium secondary battery to replace the traditional liquid electrolyte with the superiority of solid state. We propose an optimal design for the high voltage stable solid-state lithium battery system by combining the HSE composed of poly(vinyl alcohol)-g-pyrrole-2-carboxylic acid (PVA-g-PCA) and pyrrole-2-carboxylic acid modified hydrotalcite (HTpca) nano-conductor and the Al2O3 coated LiCoO2 active material. The flexible and non-flammable PVA-g-PCA-80IL-5HTpca HSE exhibits outstanding Li+ conductivity of 4.78 × 10−3 S cm−1 and Li+ transference number of 0.72 at room temperature in a wide electrochemical window up to 5.17 V vs Li+/Li, maintaining the long-term stability with Li metal over 500 cycles and low interfacial resistance of 42 Ω cm2 with cathode prepared by PVA-g-PCA-60IL-5HTpca. Utilized as a conductive binder, PVA-g-PCA-60IL-5HTpca HSE ensures the dense packing and uniform distribution of LiCoO2 particles and the excellent adhesion strength with the current collector (>24 MPa). Assembled with the Al2O3 coated LiCoO2 active material, the solid-state lithium batteries display the specific capacity of 188.7 mAh g−1 and the long-term cycling stability over 200 cycles at 4.5 V and 60 °C.

Tuning Zn2+ coordination tunnel by hierarchical gel electrolyte for dendrite-free zinc anode

Aqueous zinc-ion batteries (ZIBs) are perceived as one of the most upcoming grid-scale storage systems. However, the issues of electrode dissolution, dendrite formation, and corrosion in traditional liquid electrolytes have plagued its progress. In this work, Zn dendrite growth and side reactions are effectively suppressed by a highly-confined tannic acid (TA) modified sodium alginate (SA) composite gel electrolyte (TA-SA). The ion-confinement effect is enhanced by divalent zinc ions coordinated with carboxyl groups and chelated with phenolic hydroxyl groups, thus guiding and regulating Zn deposition to achieve steady zinc plating/stripping behavior. As a consequence, the Zn/TA-SA/NH4V4O10 full cells deliver a high specific capacity of 238.6 mAh g−1 and maintain 94.51% over 900 cycles at 2 A g−1. Notably, after resting over 5 d, the capacity can be stabilized with a capacity retention of 97.25% after 200 cycles at 2 A g−1. This highly-confined and hydrogen bond-strengthened gel electrolyte may provide an effective strategy for the future development of quasi-solid-state metal batteries.

Influence of Inorganic Glass Ceramic Particles on Ion States and Ion Transport in Composite Single-Ion Conducting Gel Polymer Electrolytes with Varying Chain Chemistry

A major goal of next-generation battery development is the engineering of nonflammable solid-state electrolytes with high enough ionic conductivity to compete with traditional liquid electrolytes. Composite polymer electrolytes (CPEs), which combine inorganic fillers or electrolytes with a polymer matrix, are seen as a strategy to boost the ionic conductivity of flexible polymer electrolytes while overcoming the brittle aspect of inorganic electrolytes. In this work, we examine the impact of polymer backbone chemistry on Li+ ion conduction within crosslinked single-ion conducting gel polymer electrolytes (SIPEs) that contain a lithium ion-conducting glass ceramic electrolyte (LICGC). Certain SIPE compositions based on poly(tetrahydrofuran) diacrylate (PTHFDA) crosslinking macromonomers exhibit a significant increase in conductivity with the inclusion of LICGC, a result unexpected from prior literature. With the use of Raman spectroscopy, small angle X-ray scattering, and particle-induced gamma-emission spectroscopy (PIGE), it is proposed that the enhanced conductivity comes from the formation of percolated LICGC particles sheathed in an ion-rich domain. This region develops in the pre-polymer solution due to interactions between the LICGC particle surface and the ionic comonomer, much like the formation of space-charge regions in soggy-sand liquid electrolytes, and persists post-polymerization to yield a CPE of enhanced conductivity. The particle–ionic monomer interactions are modulated by the crosslinking macromonomer polarity, polymer casting solvent, and particle surface area. While there is ample room for continued optimization, the best SIPEs in this study are capable of Li metal dissolution/deposition, and they reach Li+ conductivities greater than 2 × 10–4 S/cm at 25 °C, surpassing the practical use threshold.

Influence of Electron beam radiation on the properties of Surface-Modified Titania-Filled gel polymer electrolytes using vinyltriethoxysilane (VTES) for lithium battery application

Gel polymer electrolytes (GPEs) are regarded as a prospective alternative for traditional liquid electrolytes. The dispersion of nanofiller in GPEs has been proven to improve the electrolyte’s properties, such as reduced reactivity and leakage, improved safety, better shape flexibility, as well as manufacturing integrity. Meanwhile, the introduction of Electron Beam (EB) radiation remarkably enhances the electrochemical properties of GPEs. Therefore, the aim of the present work was to investigate the properties of titania-filled 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4)–poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) upon in-situ surface modification using vinyltriethoxysilane (VTES) coupling agent and its response towards 8 MeV energy EB irradiation. Following the surface modification of titania using VTES at different weight percentages (10–40%) and EB radiation exposure (5–20 kGy), the physicochemical, thermal, morphological, and electrochemical characteristics of the GPE were analyzed via Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), and impedance analysis, respectively. Based on the results, the TGA analysis showed that the thermal stability of the GPE increased with the increment of residues, which indicate the successful ceramics attachment onto the silanol group from the silane in the VTES compound. After the surface modification on the ceramic particle, the obtained average size particle was 50 nm with further enhancement of the particle distribution was observed when exposed to EB radiation. Additionally, the impedance analysis showed that the modified surface of the titania system achieved an optimum ionic conductivity of 10−2 S cm−1 at room temperature. When the electrolytes were exposed to EB radiation, the ionic conductivity increased up to 10−1 S cm−1 with the lithium transference number calculated at 0.52. These remarkable findings indicate that the developed surface modification technique of titania together with EB radiation on GPEs is a promising electrolyte for lithium-ion battery application.

A poly(1,3-dioxolane) based deep-eutectic polymer electrolyte for high performance ambient polymer lithium battery

Solid-state polymer electrolytes have recently drawn intense attention as alternatives to traditional liquid electrolytes in lithium batteries due to their high energy-density and reliable safety. Unfortunately, current all-solid-state polymer electrolytes suffer from the low ionic conductivity, limiting the power density of energy storage batteries. Here, we propose a deep-eutectic electrolyte, formed directly by the interaction between poly (1,3-dioxolane) and lithium salt without other auxiliary solvents. The ionic conductivity of the designed deep-eutectic polymer electrolyte can approach to 1.5 × 10−5 S/cm at ambient temperature, which is twenty times higher than that of polyethylene oxide-based electrolytes. Specifically, solid-state NMR verifies the interaction between oxygen in poly (1,3-dioxolane) and lithium ion. The LiFePO4/Li battery assembled with deep-eutectic polymer electrolyte delivers a discharge capacity of 139.6 mAh/g at 0.1 C and a capacity retention of 90% after 200 cycles at 0.2 C. Pouch LiFePO4/Li batteries also present excellent safety performances. This finding provides a new approach for materials engineering of polymer electrolytes for advanced lithium batteries.

A Hollow Porous Metal‐Organic Framework Enabled Polyethylene Oxide Based Composite Polymer Electrolytes for All‐Solid‐State Lithium Batteries

AbstractComposite polymer electrolytes (CPEs) are replacing traditional liquid electrolytes for next‐generation all‐solid‐state batteries (ASSBs) with enhanced safety and uncompromising electrochemical properties. However, short‐circuit due to lithium‐dendrite growth in the CPEs largely hinders its practical applications. Here, we report a thin CPE composed of the hollow ZIF‐8 encapsulating Li‐ionic liquids (ZIF‐8/IL) nano‐fillers and polyethylene oxide (PEO) matrix. It shows an ionic conductivity of 1.41×10−4 S cm−1 at 25 °C with improved surface roughness, thermal stability, and electrochemical stability. The specific core‐shell structure of fillers benefits from its insulation shell for inhibiting lithium dendrite growth and the inner cavity for storing sufficient Li‐IL with enhanced Li diffusivity. The CPE with 30 % filler (30 H‐Z CPE) content exhibits excellent cycle stability of 770 h in the Li symmetric cell and an outstanding discharge capacity of 182.5 mAh g−1 and capacity retention of 73 % after 100 cycles at 0.1 C and 60 °C in the Li/30 H‐Z CPE/NCM811 asymmetric cell.

Manipulating Ion Concentration to Boost Two‐Electron Mn4+/Mn2+ Redox Kinetics through a Colloid Electrolyte for High‐Capacity Zinc Batteries

AbstractAqueous zinc batteries (ZBs) have flourished due to their advantages of low‐cost and intrinsically safe water‐based electrolytes. However, in the traditional liquid electrolyte, sufficient energy density and efficiency for practical utility have not been realized yet. Here, instead of the use of a strong acid/alkali pH environment to elevate the working voltage in an aqueous solution, an ion concentration/dilution strategy is proposed to trigger the extra deposition/dissolution capacity of the Mn4+/Mn2+ redox reaction in normal Zn/MnO2 batteries. With the precipitation and release of Zn2+ ions during the discharge/charge process, the adjustment of manganese concentration is successfully realized via the reciprocal Zn/Mn ionic exchange rendered by the bentonite colloidal (Ben‐colloid) electrolyte. This electrolyte also triggers a self‐dissolution/deposition reaction even in the cathode‐free system. Consequently, the Zn/MnO2 battery with Ben‐colloid electrolyte affords up to 1.7× capacity release (480.7 mAh g–1) on average compared with a liquid electrolyte at 0.2 A g–1, higher capacity retention (94.3% vs 63.6%) after 500 cycles at 1 A g–1, and good elevated‐temperature endurability (up to 80 °C). This work opens up a new horizon to improve the energy density of water‐based metal ion batteries by the use of a functional electrolyte.

Design of Non-Incendive High-Voltage Liquid Electrolyte Formulation for Safe Lithium-Ion Batteries.

Battery safety has an ever-increasing significance and is required for consumer's safety. The high flammability of traditional organic liquid electrolyte, which consists of ethylene carbonate and highly flammable linear carbonate, is one of the major reasons for thermal runaway and battery fire events. Replacement of flammable liquid electrolyte with non-incendive one is urgently needed for safe lithium-ion batteries. A fluorinated linear sulfate paired with 1 m LiPF6 was developed and evaluated as a solvent of non-incendive liquid electrolyte for a use in high-voltage (4.4 V) and high-temperature (45 °C) LiNi0.82 Mn0.07 Co0.11 O2 (NCM811) chemistry-based lithium-ion batteries. Non-incendive liquid electrolyte containing sulfate with two trifluoroethyl groups exhibited superior anodic and thermal stability and promoted cathode-electrolyte and anode-electrolyte interfacial stability, compared to flammable traditional electrolyte. Non-incendive electrolyte showed markedly improved 300 cycle performance of an industrial graphite‖NCM811 lithium-ion pouch cell with a nominal capacity of 730 mAh under harsh conditions, and high safety of 10 V overcharge abuse tolerance, from which safe and high-performing high-energy lithium-ion batteries and battery-powered electric vehicles and energy storage system are anticipated.

MAS-NMR of [Pyr13][Tf2N] and [Pyr16][Tf2N] Ionic Liquids Confined to Carbon Black: Insights and Pitfalls.

Electrolytes based on ionic liquids (IL) are promising candidates to replace traditional liquid electrolytes in electrochemical systems, particularly in combination with carbon-based porous electrodes. Insight into the dynamics of such systems is imperative for tailoring electrochemical performance. In this work, 1-Methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide and 1-Hexyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide were studied in a carbon black (CB) host using spectrally resolved Carr-Purcell-Meiboom-Gill (CPMG) and 13-interval Pulsed Field Gradient Stimulated Echo (PFGSTE) Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). Data were processed using a sensitivity weighted Laplace inversion algorithm without non-negativity constraint. Previously found relations between the alkyl length and the aggregation behavior of pyrrolidinium-based cations were confirmed and characterized in more detail. For the IL in CB, a different aggregation behavior was found compared to the neat IL, adding the surface of a porous electrode as an additional parameter for the optimization of IL-based electrolytes. Finally, the suitability of MAS was assessed and critically discussed for investigations of this class of samples.

Practical considerations in designing solid state Li-S cells for electric aviation

The development of high-energy, high-safety, and high-power batteries beyond electric automotive standards is critical for future electric aviation applications. Non-volatile solid-state electrolytes (SSE) offer many promising advantages over traditional flammable liquid electrolytes. SSE may become an enabling technology for certain battery chemistries by preventing detrimental interactions that occur with liquid electrolytes, for example preventing dissolution of lithium-sulfur intermediates common in traditional liquid organic solvents. However, significant manufacturing challenges must be overcome before the adoption of such technology. One of the main challenges is the fabrication of sufficiently thin electrolyte layer to maximize specific energy of the solid-state cell. In this work we first show the feasibility in the assembly of an all solid-state battery via the development of composite SSE with ionic conductivity above 0.2mS/cm and thicknesses on the order of 40 micron through a tape-casting technique. With Li/Al alloy as the anode and TiS2 as the active cathode material, the resultant solid-state battery with a thin electrolyte layer and excellent cathode-electrolyte interface represents a prototype vision on a potential solid-state cell required for electric aviation. A detailed parameter analysis is further presented on the influence of the various cell metrics, such as electrolyte thickness, carbon content, active material utilization, and excess lithium, on the cell specific energy. The implications in the optimization of these required parameters to enable practical solid-state Li-S batteries for electric aviation are discussed.

Polyurethane-based polymer electrolytes for lithium Batteries: Advances and perspectives

Polymer electrolytes (PEs) have been widely regarded as an effective approach to eliminate most of the potential safety hazards encountered in traditional liquid electrolytes for lithium batteries (LBs). Substantial research efforts have been devoted to exploiting excellent performance PE systems, including poly(ethylene oxide) (PEO), polyurethane (PU), polysiloxane (PS), polyvinylidene fluoride (PVDF) and polycarbonate (PC)-based PEs. Among them, PU-based PEs have attracted increasing interests due to their flexibility of structure manipulation, excellent mechanical strength, facile modification, high thermal and electrochemical stability. However, to date, separated and detailed reviews on the progress of PU-based PEs are rarely reported. In this review, we comprehensively summarize the key progress on PU-based PEs from the perspective of flexible structure design strategies, basic electrochemical/mechanical properties, typical modification methods, specific functions, and their potential applications in LBs. Furthermore, synthesis routes of PUs and perspectives of PU-based PEs are also discussed. It is believed that this review will be of great guiding significance for exploiting high performance PU-based PEs for next-generation LBs.