Quasi-solid Electrolyte Research Articles

A flexible three-dimensional composite nanofiber enhanced quasi-solid electrolyte for high-performance lithium metal batteries

A quasi-solid-state electrolyte based on LATP-PVDF-HFP nanofiber matrix and gel is proposed. The fabricated battery exhibits a good discharge capacity of 146.6 mA h g−1 at 2C, while the capacity retention can reach 97% after 300 cycles at 0.5C.

Super-stretchable and extreme temperature-tolerant supramolecular-polymer double-network eutectogels with ultrafast in situ adhesion and flexible electrochromic behaviour.

The current tough and stretchable gels with various integrated functions are mainly based on polymer hydrogels. By introducing a non-covalent supramolecular self-assembled network into a covalently cross-linked polymer network in the presence of eco-friendly and cost-effective deep eutectic solvents (DESs), we developed a new small molecule-based supramolecular-polymer double-network (SP-DN) eutectogel platform. This exciting material exhibits high stretchability and toughness (>18 000% areal strain), spontaneous self-healing ability, ultrafast (∼5 s) in situ underwater and low-temperature (-80 °C) adhesion, and unusual boiling water-resistance, as well as strong base-, strong acid- (even aqua regia), ultra-low-temperature- (liquid nitrogen, -196 °C), and high-temperature- (200 °C) resistance. All these outstanding properties strongly recommend the SP-DN eutectogels as a quasi-solid electrolyte for soft electrochromic devices, which exhibited exceptional flexibility and consistent electrochromic behaviours in harsh mechanical or temperature environments. The experimental and simulation results uncovered the assembly mechanism of the SP-DN eutectogels. Unlike polymer hydrogels, the obtained SP-DN eutectogels showed high molecular design freedom and structural versatility. The findings of this work offer a promising strategy for developing the next generation of mechanically robust and functionally integrated soft materials with high environmental adaptability.

Quasi-solid electrolyte developed on hierarchical rambutan-like γ-AlOOH microspheres with high ionic conductivity for lithium ion batteries.

Upgrading liquid electrolytes with all-solid-state electrolytes (ASEs) or quasi-solid-state electrolytes (QSEs) for solid-state batteries (SBs) have emerged not only to address the intrinsic disadvantages of traditional liquid lithium ion batteries, but also to offer more possibilities for the development of new battery chemistries. In this work, a novel rambutan-like yolk-shell-structured porous γ-AlOOH microsphere with a large specific surface area of 262.92 m2 g-1 was firstly obtained by a simple hydrothermal synthesis route, which was then utilized as a robust framework to assemble QSE via encapsulating abundant liquid electrolyte (LE). The obtained γ-AlOOH-QSE exhibits a high ionic conductivity of 4.0 × 10-3 S cm-1, a large lithium ion transference number (tLi+) of 0.76, as well as a wide electrochemical window of 4.72 V vs. Li/Li+. Moreover, the assembled cell of LiFePO4/γ-AlOOH-QSE/Li could maintain a high specific capacity of 144.4 mA h g-1 even after 120 cycles with almost negligible capacity decay, which could be mainly attributed to the excellent interfacial compatibility, prominent performance in suppressing lithium dendrite growth upon cycling (rigid characteristic), as well as the high ionic conductivity of γ-AlOOH-QSE (intrinsic advantage). This work could not only expand the applications of QSE with cost-effective aluminum-based oxides with facile fabrication strategy, but also will shed light on the construction of SEs with more integrated QSEs and ASEs in the field of advanced energy storage.

Dye-sensitized solar cells based on MK2 dye, PMMA-based quasi-solid electrolyte, and flexible CNT counter electrode

In this paper, a dye-sensitized solar cell based on organic MK2 dye, a quasi-solid electrolyte, and a flexible counter electrode was investigated. Two types of TiO2 nanoparticles with different sizes were used to make the photoanode with a bi-layer structure. The quasi-solid electrolyte was made based on polymethylmethacrylate (PMMA) and iodide/triiodide couple. The counter electrode was fabricated by electrophoresis deposition of carbon nanotube (CNT) mixed with diallyl dimethylammonium chloride (PDDA) on a flexible stainless-steel mesh. A cellulose separator was used to improve the stability of the solar cell. A simple and low-cost sealing method using polypropylene-based tape has been proposed and used for conducting the stability test. The maximum conversion efficiency of 2.5% (under simulated AM 1.5) was obtained with the fabricated quasi-solid dye-sensitized solar cells.

Development of high-capacity flexible sodium manganese periodate batteries with dual polymer electrolytes

We present the development of a dual-electrolyte, flexible battery based on sodium manganese periodate-zinc system. H3PO4-KCl quasi-solid dual electrolytes separated by an anion-exchange-membrane maintained the desired pH at electrodes and blocked unwanted ion movements. Poly(acrylic acid) based quasi-solid electrolytes were optimized to fortify the electrodes, increase electrode flexibility, eliminate free-flow liquids, and enhance battery performance. Anode electrolyte pH adjustment enhanced ionic conductivity and reduced zinc corrosion. The nano-grade NaMnIO6 showed a specific capacity of 650 mA h g−1, approximately 81 % of its theoretical capacity even when cells are bent. The capacity reported here is at least 80 % higher than other flexible battery reported before.

A design of Nafion-coated bilayered quasi-solid electrolyte for lithium-O2 batteries with high performance

In this paper, a novel bilayer-structured quasi-solid polymer electrolyte (NSPE) has been designed with separate catholyte and anolyte, which compose of P(VDF-HFP)/Li-Nafion solid polymer electrolyte and TEMPO as cathodic additives. The SEM images shows that the surface morphology of NSPE is smoother and more uniform than that of SPE. The Li-O2 battery using NSPE showed high ionic conductivity, low interface impedance, good rate performance, and higher security and good cycling stability while reducing polarization. Lithium-air (also known as lithium-oxygen) batteries have attracted considerable global attention in recent years due to their extremely high energy density (11,140 W·h·kg −1 ). The electrolyte is a key element in lithium-air batteries and the traditional organic electrolyte has great safety risk due to leakage. On the contrary, the polymer electrolyte has the advantages of high safety, high stability and easy processing comparing with the organic liquid electrolytes. In this paper, a new idea was proposed to coat the Nafion membrane on a layer of polymer for blocking the oxidation reduction electric (RM) and Li based on the selective permeability on lithium ion of the Nafion membrane. Self-made thickness-controllable Nafion membrane, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and 2,2,6,6-tetramethylpiperidinooxy (TEMPO) were used to prepare a quasi solid polymer electrolyte (NSPE). Electrochemical workstation and LAND battery testing system were used to perform a galvanostatic charge/discharge test on Li-O 2 . The ionic conductivity of NSPE was 4.3 × 10 −4 S·cm −1 at room temperature and the discharge platform was 2.6 V and the charging voltage was 3.7 V after 50 cycles with the cut-off capacity of 500 mA·h·g −1 .

3D-Printed Energy Storage Devices

The increasing demand for multifunctional portable/wearable electronic devices, including wireless sensors and implantable medical devices is continuously growing. Such devices need rechargeable batteries with dimensions on the scale of 1–10 mm3 (few to tens mm2 footprint area of substrate) including all the components and all the associated packing. Thus, in the past decade, along with the developments in battery materials, the focus has been shifting more and more towards innovative fabrication processes, unconventional configurations, and designs with multi-functional components. 3D printing technologies enable a well-controlled creation of functional materials with three-dimensional architectures, representing a promising approach for fabrication of next-generation electrochemical energy storage (EES) devices with high performance due to a higher electrode/electrolyte interfacial area.In this work, we demonstrate a novel design and a novel approach of 3D printing of batteries of different shapes and size by using filaments composed of active electrode materials bound with polymers. The electrodes were printed by fused-filament fabrication (FFF) method. We demonstrated a reversible electrochemical cycling of 3D printed lithium iron phosphate (LFP) and lithium titanate (LTO) composite polymer electrodes vs. lithium metal anode with high performance and capacity in cells containing both conventional non-aqueous and ionic-liquid electrolytes.In addition, the development and fabrication of a novel 3D-printed solid-state or quasi-solid electrolyte by FFF has been accomplished. The electrolytes are composed primarily of polyethylene oxide (PEO) and polyethylene glycol (PEG) which are known ionic conductors, and polylactic acid (PLA) for enhanced mechanical properties and high temperature durability.Our research introduces novel thick-layer 3D batteries, thus reducing cost related to high mass loading per battery footprint of smart 3D structures with the help of low-cost fabrication method.

Effect of Ionomer Binders on Performance and Durability of Catalyst Layers in Polymer Electrolyte Electrolyzers

Hydrogen based energy conversion devices such as water electrolyzers or fuel cells require catalyst layers as electrode providing the simultaneous movement of gas, liquid, and electron. The movement of ions generated and consumed at two electrodes, i.e., anode and cathode, respectively, takes place by ionomer binders made of perfluorosulfonic acids. Ions should be transported inside electrodes to participate in anodic and cathodic reactions. Ion pathway is normally in liquid electrolyte. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. In addition, if gas penetration or gas evolution is one of phenomena taking place at electrodes, the electrodes should be porous. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion exchangeable polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion exchangeable polymers within electrodes for oxidation and reduction reactions is to solidify catalyst inks consisting of electrocatalyst, dispersion of ion exchangeable polymers, controlling solvents and additives by evaporation of all solvents in catalyst inks. Ion exchangeable polymers could be dispersed in various solvents. It causes different shapes of ion exchangeable polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion exchangeable polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion exchangeable polymers on the performance and durability of catalyst layers was investigated. Electrochemical characterization such as I-V polarization, cyclic voltammetry, impedance and so on and microscopic characterization such as SEM and TEM were carried out to evaluate the performance and durability of catalyst layers. Acknowledgment This research was supported by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning(NRF-2019M3E6A1063677).

Preparation of Anion Conducting Pore Filling Membranes for Direct Hydrazine Fuel Cells

Hydrazine fuel cells in an alkaline medium are a promising energy conversion technology due to the extraordinary properties of hydrazine as a hydrogen carrier. Alkaline electrolyte fuel cells allow the use of less expensive metals such as cobalt and nickel as an electrode catalyst. The devices consist of a pair of electrochemical reactions at electrodes and anion movement through electrolytes to complete full electrochemical cells. Anions move from cathode to anode or vice versa for electron exchanges. Pathway for ions is normally in an aqueous phase. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. An approach to minimize areal resistance of film-type polymeric electrolytes is to make membrane thickness as thin as possible. In this study, pore filling membranes have been studied as a new type of electrolytes. Pore filling membranes are made by impregnating monomers into thin porous substrates, followed by heat or UV cured polymerization. Pore filling membranes with the thickness of 20-50 μm were prepared using porous substrates with hydrophilized surface. A technique to make the surface of pore filling membranes hydrophilic were developed so as to adsorb liquid hydrated hydrazine fuel in KOH supporting electrolyte. Characterization in terms of ion conductivity, ion exchange capacity, water uptake, dimensional stability, mechanical strength was carried out and discussed. Acknowledgment This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning(NRF-2018M1A2A2063866).

Robust Strategy of Quasi-Solid-State Electrolytes to Boost the Stability and Compatibility of Mg Ion Batteries.

Magnesium ion batteries (MIBs) have attracted a lot of attention because of the natural abundance of magnesium, high volumetric energy density, and superior safety. Nevertheless, MIBs are still in their infancy because of the significant challenge in developing a suitable electrolyte with low flammability, high ionic conductivity, and compatibility with the Mg anode. Herein, we construct rechargeable quasi-solid-state MIBs based on tailored polymer electrolytes. The quasi-solid state electrolyte of poly(vinylidene fluoride-co-hexafluoropropylene)-nanosized SiO2-Mg(TFSI)2 combines the outstanding dynamic property of a liquid electrolyte and the good stability of a solid-state electrolyte. It exhibits a highly reversible Mg2+ deposition-dissolution capability, high ion conductivity (0.83 mS cm-1), and superior compatibility with the Mg metal and cathode. The quasi-solid-state MIBs with a layered titanic oxide cathode show a high reversible capacity of 129 mA h g-1 at 50 mA g-1 (150 W h kg-1) without any decay after 100 cycles.

Hydrogel Electrolytes for Quasi-Solid Zinc-Based Batteries.

On account of high energy density depending on the utilized zinc metal anode of high theoretical capacity and its excellent security due to aqueous electrolytes that usually be locked in polymer hosts referred to as hydrogels, quasi-solid zinc-based batteries have been subjected to more and more interest from researchers. The good water retention and electrolyte load capacity of the hydrogel, contributing to the acquirement of high ionic conductivity and durability of the as-obtained quasi-solid electrolyte, play a significant role on the performance of the devices. Moreover, the chemistry of hydrogels can be tuned to endow quasi-solid electrolytes with additional functions in terms of application scenarios of solid-state batteries. Herein, the frontier disciplines of hydrogel electrolytes for Zn-based batteries were reviewed. The cross-linking process of the polymer networks for hydrogel materials with different functions, such as stretchability, compressibility, and self-healing, were also discussed to analyze the properties of the polymer electrolyte. Based on the merits of the functionalized hydrogel, the further application of hydrogel electrolytes in Zn-based batteries is the focus of this paper. The electrochemical performance and mechanical property of Zn-based batteries with functionalized hydrogel electrolytes under extreme conditions were presented to evaluate the crucial role of the polymer hydrogel electrolyte. Finally, the challenges of hydrogel electrolytes for currently developed Zn-based batteries are highlighted with the hope to boost their commercial application in energy conversion devices.

Analysis of Solid-Electrolyte Interphase at the Interface between a Graphite Negative Electrode and a Diluted Solvate Ionic Liquid-Based Quasi-Solid-State Electrolyte

The formation and growth mechanism of a solid-electrolyte interphase (SEI) on a graphite-based negative electrode was investigated to enhance the cycle life of lithium ion batteries with a quasi-solid state electrolyte (QSE). In a QSE, liquid constituents including solvate ionic liquid (SIL), diluting solvent, and additives are quasi-solidified on surface of silica particles, which ensures the safety of a 100 Wh class laminated cell. For the SIL, an equimolar complex composed of tetraethylene glycol dimethyl ether (G4) and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA), was utilized. Propylene carbonate (PC) was used as diluting solvent to enhance the ionic conductivity of the SIL. Vinylene carbonate (VC) additive was introduced to form a robust SEI for inhibiting the reductive decomposition of G4 and PC. Nuclear magnetic resonance and hard X-ray photoelectron spectroscopy revealed that the decompositions of LiTFSA, PC, and G4 contributed to the SEI formation at the initial charge. During charge-discharge cycles, continuous decompositions of G4 and PC were a major reason for the SEI growth. To suppress the decomposition, charging at a low rate was introduced at beginning of the initial charge to enhance the VC decomposition and the robust SEI formation. Consequently, the decomposition of the QSE was inhibited, which enhanced its cycle life.

Characteristics of ionic adsorption on silica nanoparticles and its impact on the long term stability of dye-sensitized solar cells

Quasi-solid electrolytes based on silica nanopowder are well known in literature and these electrolytes are able to match in performance with that of liquid electrolytes. However, contrasting results are observed in literature regarding stability of dye-sensitized solar cells (DSSCs) with most of the reported articles projecting silica-loaded quasi-solid electrolyte-based cells as a stable alternative to liquid electrolyte-based cells, while a few others contradicting the same. The present study demonstrates the effect of ageing under heat (60°C) and illumination on the performance of liquid electrolyte and silica-loaded electrolyte-based DSSCs. It has been observed that DSSC based on silica-loaded electrolyte are less stable than DSSC based on liquid electrolyte even though independent study on both electrolytes by thermal analysis shows silica-loaded electrolyte to be more stable than liquid electrolyte. Segregation of silica in electrolyte has been confirmed through cryo-field emission gun-scanning electron microscopy. Zeta potential measurements show that ions are desorbed from the surface of silica on ageing under heat and illumination.

In situ formation of poly(butyl acrylate)-based non-flammable elastic quasi-solid electrolyte for dendrite-free flexible lithium metal batteries with long cycle life for wearable devices

With the rapid development of wearable devices, there is an increasing demand for ultra-safe flexible lithium-ion batteries (LIBs) capable of delivering high energy density. Because it can provide the highest possible capacity of 3860 mAh g-1, lithium metal has drawn tremendous research attention. However, Li is a highly reactive metal that grows dendrites during the cycling of lithium-metal batteries (LMBs). To resolve the problem, we developed a new non-flammable elastic quasi-solid electrolyte (QSE), which can be polymerized in situ and whose composition is tailored to achieve high elasticity. Moreover, the incorporation of trimethyl phosphate (TMP) renders the electrolyte non-flammable. Thanks to the solid electrolyte interphase (SEI) formed, the LMB with QSE displays excellent cycling stability as it can be operated for 500 cycles, with a capacity retention of 94%. The corresponding symmetric cell cycled stably for more than 500 h. Scanning electron microscopy (SEM) and density functional theory (DFT) calculations reveal that fluoroethylene carbonate (FEC) is critical in forming the LiF-rich SEI that enables long-term cycling stability. In brief, a non-flammable, elastic, and stable QSE is reported for the first time, which is very promising in the application of the next-generation wearable devices.

Development of Rapid Curing SiO2 Aerogel Composite-Based Quasi-Solid-State Dye-Sensitized Solar Cells through Screen-Printing Technology.

Grätzel's dye-sensitized solar cells (DSSCs) can readily convert sunlight into electricity, attracting considerable attention of global scientists. The fabrication efficiency of DSSCs was greatly limited by the slow fabrication (∼3.5-24 h) of quasi-solid (QS) electrolytes to date. In this study, novel composites of SiO2 aerogel with graphene (GR), multi-walled carbon nanotubes, or polyaniline were proposed in the fabrication of QS-state electrolytes. The morphology of these composites was characterized. The gels with SiO2 aerogels as QS electrolytes of DSSCs can be rapidly cured in ∼3 s. Using the screen-printing technology, these QS electrolytes can be readily utilized to construct the QS-DSSC to provide high efficiency and great stability. The photovoltaic parameters and interfacial charge-transfer resistances of the QS-DSSC incorporated with our synthetic composites were investigated in detail. Specifically, the SiO2 aerogel composed of GR (SiO2@GR) as a gel can greatly improve the performance of QS-DSSCs up to 8.25%. It is likely that these SiO2 aerogel composite electrolytes could provide a rapid curing process in the preparation of QS-state DSSCs, which might be useful to promote the development of DSSCs for future industrialization.

Rising the molecular mobility of polyvinyl butyral by plasticizers: towards energy storage applications

The versatile behaviour of poly-vinylbutyral (PVB) and its ability to form quasi-solid polymer electrolytes (SPE) with reliable ionic mobility, has been investigated over the temperature range from 120 K to 350 K, by mechanical and dielectric spectroscopic measurements. Enhancements in the polymer chain flexibility, due to the addition of low molar mass organic liquid plasticizers (acetonitrile, AcN, and methoxy-propionitrile, MPN) favouring the long-range motion of charge carriers, give rise to a room temperature ionic conductivity which in the hybrid PVB/MPN/LiI system increases of about 3 and 9 orders of magnitude with respect to the counterparts PVB/LiI and pure dry-PVB system, respectively. This result proves the existence of coupling between cooperative segmental motion and ion dynamics in such kind of materials.

SYNTHESIS AND CHARACTERIZATION OF CHITOSAN/SODIUM ALGINATE BLEND MEMBRANE FOR APPLICATION IN AN ELECTROCHEMICAL CAPACITOR

In this work, we report a stepwise formation method of a chitosan/sodium alginate polyelectrolyte complex (CS/SA PEC) membrane. The proposed method aiming at the utilization of the ultrasonic treatment of chitosan and sodium alginate solution allowed us to obtain a highly homogeneous hybrid membrane for electrochemical usage. The CS/SA PEC membrane saturated in a 2 M Li2SO4 aqueous solution was used in electrochemical double layer capacitor (EDLC) cell to study its applicability as quasi-solid electrolyte. Electrochemical characteristic of EDLC cells was determined by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge/discharge methods. The results show that the EDLC cell with CS/SA PEC quasi-solid electrolyte exhibit a comparable specific capacitance (102 F g-1 for 0–0.8 V) to CS reference (100 F g-1 for 0–0.8 V) and commercial separator (99 F g-1 for 0–0.8 V) cells. Thus, the CS/SA PEC membrane can be considered as an alternative modification for chitosanbased materials of electrochemical purpose.

A study on the microstructural development of gel polymer electrolytes and different imidazolium-based ionic liquids for dye-sensitized solar cells

Quasi-solid state electrolyte (gel-like) based on polymer matrix PVDF-HFP/PEO is considered as a suitable candidate for producing DSSC due to its essential influence on the performance of the device. In this work, PVDF-HFP/PEO membranes were prepared over the whole composition range in presence of either one of the ionic liquids (ILs) including BMII plus LiI, or BMIMBF4 via phase inversion and compared with liquid electrolyte and ILs individually. It was found that the blend ratio affected some of the membrane properties, such as porosity, pore size, pore connectivity, liquid uptake ability, and morphology. SEM analysis and mercury porosimetry were used to study the pore configuration and porosity of the membranes. The effects of two semicrystalline polymers on the morphology and crystallinity of the membrane were examined by DSC and also WAXD. It was found that there is a direct relationship between the crystallinity reduction and improvement of ionic conductivity of the samples. The photovoltaic performances of the fabricated DSSC at the highest ionic conductive optimized membrane revealed an improvement of Voc, Jsc, fill factor, and the solar conversion efficiency of 6.47%. The long-term durability of the quasi solid DSSC was increased compared to a liquid type electrolyte.

Preparation and characterization of composite quasi-solid electrolytes composed of 75Li2S·25P2S5 glass and phosphate esters

Mechanical properties and ionic conductivities of solid electrolytes are important factors influencing the performance of all-solid-state batteries. This study investigates composite quasi-solid electrolytes composed of Li2S–P2S5 glass and a phosphate ester, prepared via planetary ball milling, and the relative densities of the powder-compressed pellets, formed using the composite quasi-solid electrolytes. Dense pellets of the Li2S–P2S5 glass electrolyte are obtained via addition of phosphate esters; the relative densities increase from 90.6% to 93.1%, without the ionic conductivities decreasing, upon addition of a small quantity of tris (2, 2, 2-trifluoroethyl) phosphate to the Li3PS4 glass. The addition of small quantities of phosphate esters to sulfide solid electrolytes is effective in improving the formability of these solid electrolytes.

Characterization of quasi-solid electrolytes based on Li<sub>3</sub>PS<sub>4</sub> glass with organic carbonate additives

Characterization of quasi-solid electrolytes based on Li<sub>3</sub>PS<sub>4</sub> glass with organic carbonate additives