Super Soft All-Ethylene Oxide Polymer Electrolyte for Safe All-Solid Lithium Batteries

Bioinspired Synaptic Branched Network within Quasi-Solid Polymer Electrolyte for High-Performance Microsupercapacitors

The branched network-driven ion solvating quasi-solid polymer electrolytes (QSPEs) are prepared via one-step photochemical reaction. A poly(ethylene glycol diacrylate) (PEGDA) is combined with an ion-conducting solvate ionic liquid (SIL), where tetraglyme (TEGDME), which acts like interneuron in the human brain and creates branching network points, is mixed with EMIM-NTf2 and Li-NTf2. The QSPE exhibits a unique gyrified morphology, inspired by the cortical surface of human brain, and features well-refined nano-scale ion channels. This human-mimicking method offers excellent ion transport capabilities through a synaptic branched network with high ionic conductivity (σDC ≈ 1.8 mS cm-1 at 298 K), high dielectric constant (εs ≈ 125 at 298 K), and strong ion solvation ability, in addition to superior mechanical flexibility. Furthermore, the interdigitated microsupercapacitors (MSCs) based on the QSPE present excellent electrochemical performance of high energy (E  =  5.37 µWh cm-2) and power density (P  =  2.2 mW cm-2), long-term cycle stability (≈94% retention after 48 000 cycles), and mechanical stability (>94% retention after continuous bending and compressing deformation). Moreover, these MSC devices have flame-retarding properties and operate effectively in air and water across a wide temperature range (275 to 370 K), offering a promising foundation for high-performance, stable next-generation all-solid-state energy storage devices.

Capacity Degradation of Zero-Excess All-Solid-State Li Metal Batteries Using a Poly(ethylene oxide) Based Solid Electrolyte

Solid-state polymer electrolytes (SPEs), such as poly(ethylene oxide) (PEO), have good flexibility when compared to ceramic-type solid electrolytes. Therefore, it could be an ideal solid electrolyte for zero-excess all-solid-state Li metal battery (ZESSLB), also known as anode-free all-solid-state Li battery, development by offering better contact to the Cu current collector. However, the low Coulombic efficiencies observed from polymer type solid-state Li batteries (SSLBs) raise the concern that PEO may consume the limited amount of Li in ZESSLB to fail the system. Here, we designed ZESSLBs by using all-ceramic half-cells and an extra PEO electrolyte interlayer to study the reactivity between PEO and freshly deposited Li under a real battery operating conduction. By shuttling active Li back from the anode to the cathode, the PEO SPEs can be separated from the ZESSLBs for experimental studies without the influence from cathode materials or possible contamination from the usage of Li foil as the anode. Electrochemical cycling of ZESSLBs shows that the capacities of ZESSLBs with solvent-free and solvent-casted PEO SPEs significantly degraded compared to the ones with Li metal as the anode for the all-solid-state Li batteries. The fast capacity degradation of ZESSLBs using different types of PEO SPEs is evidenced to be associated with Li reacting with PEO, residual solvent, and water in PEO and dead Li formation upon the presence or absence of residual solvent. The results suggest that avoiding direct contact between the PEO electrolyte and deposited lithium is necessary when there is only a limited amount of Li available in ZESSLBs.

Applications of Polymer Electrolytes in Lithium-Ion Batteries: A Review

Polymer electrolytes, a type of electrolyte used in lithium-ion batteries, combine polymers and ionic salts. Their integration into lithium-ion batteries has resulted in significant advancements in battery technology, including improved safety, increased capacity, and longer cycle life. This review summarizes the mechanisms governing ion transport mechanism, fundamental characteristics, and preparation methods of different types of polymer electrolytes, including solid polymer electrolytes and gel polymer electrolytes. Furthermore, this work explores recent advancements in non-aqueous Li-based battery systems, where polymer electrolytes lead to inherent performance improvements. These battery systems encompass Li-ion polymer batteries, Li-ion solid-state batteries, Li-air batteries, Li-metal batteries, and Li-sulfur batteries. Notably, the advantages of polymer electrolytes extend beyond enhancing safety. This review also highlights the remaining challenges and provides future perspectives, aiming to propose strategies for developing novel polymer electrolytes for high-performance Li-based batteries.

A Stretchable Solid Ionic Electrode-Based Triboelectric Nanogenerator for Biomechanical Energy Harvesting and Self-Powered Sensors

Stretchable power devices and self-powered sensors have become increasingly desired for wearable electronics and artificial intelligence. In this study, an all-solid-state triboelectric nanogenerator (TENG) is reported, whose one solid-state structure prevents delamination during stretch and release cycles and increasing the patch adhesive force (3.5 N) and strain (586% elongation at break). Through the synergetic virtues of stretchability, ionic conductivity, and excellent adhesion to the tribo-layer, reproducible open-circuit voltage (VOC ) of 84 V, charge (QSC ) of 27.5 nC, and short-circuit current (ISC ) of 3.1 µA after drying at 60°C or 20,000 contact-separation cycles are obtained. Apart from contact-separation, this device shows unprecedented electricity generation through stretch-release of solid materials leading to a linear relationship between VOC and strain. For the first time, this work provides a clear explanation of the working mechanism of contact-free stretching-releasing and investigates the relationships of exerted force, strain, thickness of the device, and electric output. Benefitting from the one solid-state structure, this contact-free device remains stable even after repeated stretch-release cycling, maintaining 100% of its VOC after 2500 stretch-release cycles. These findings provide a strategy toward highly conductive and stretchable electrodes for harvesting mechanical energy and health monitoring.

Quantifying and Reducing Ion Migration in Metal Halide Perovskites through Control of Mobile Ions

The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (N_o) and ionic mobility (µ) and demonstrate that N_o has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.g., Na⁺, K⁺, and Rb⁺) on ion migration. We show that the influence of moisture and cation additive on N_o is less significant than the choice of top electrode in PSCs. We also show that N_o in PSCs remains constant with an increase in temperature but μ increases with temperature because the activation energy is lower than that of ion formation. This work gives design principles regarding the importance of passivation and the effects of operational conditions on ion migration.

Intrinsically Stretchable Integrated Passive Matrix Electrochromic Display Using PEDOT:PSS Ionic Liquid Composite

The low power consumption of electrochromism makes it widely used in actively shaded windows and mirrors, while flexible versions are attractive for use in wearable devices. Initial demonstration of stretchable electrochromic elements promises good conformability to complex surfaces. Here, fully integrated intrinsically stretchable electrochromic devices are demonstrated as single elements and 3 × 3 displays. Conductive and electrochromic ionic liquid-doped poly(3,4-ethylenedioxythiophene) polystyrene sulfonate is combined with poly(vinyl alcohol)-based electrolyte to form complete cells. A transmission change of 15% is demonstrated, along with a reflectance change of 25% for opaque reflective devices, with <7 s switching time, even under 30% strain. Stability under both electrochemical and mechanical strain cycling is demonstrated. A passive matrix display exhibits addressability and low cross-talk under strain. Comparable optical performance to flexible electrochromics and higher deformability provide attractive qualities for use in wearable, biometric monitoring, and robotic skin devices.

A Metal-Organic Framework Based Quasi-Solid-State Electrolyte Enabling Continuous Ion Transport for High-Safety and High-Energy-Density Lithium Metal Batteries

Solid-state lithium metal batteries are promising next-generation rechargeable energy storage systems. However, the poor compatibility of the electrode/electrolyte interface and the low lithium ion conductivity of solid-state electrolytes are key issues hindering the practicality of solid-state electrolytes. Herein, rational designed metal-organic frameworks (MOFs) with the incorporation of two types of ionic liquids (ILs) are fabricated as quasi-solid electrolytes. The obtained MOF-IL electrolytes offer continuous ion transport channels with the functional sulfonic acid groups serving as lithium ion hopping sites, which accelerate the Li⁺ transport both in the bulk and at the interfaces. The quasi-solid MOF-IL electrolytes exhibit competitive ionic conductivities of over 3.0 × 10^-4 S cm^-1 at room temperature, wide electrochemical windows over 5.2 V, and good interfacial compatibility, together with greatly enhanced Li⁺ transference numbers compared to the bare IL electrolyte. Consequently, the assembled quasi-solid Li metal batteries show either superior stability at low C rates or improved rate performance, related to the species of ILs. Overall, the quasi-solid MOF-IL electrolytes possess great application potential in high-safety and high-energy-density lithium metal batteries.

Organoboron- and Cyano-Grafted Solid Polymer Electrolytes Boost the Cyclability and Safety of High-Voltage Lithium Metal Batteries

Solid-state polymer electrolytes (SPEs) are deemed as a class of sought-after candidates for high-safety and high-energy-density solid-state lithium metal batteries, but their low ionic conductivity, narrow electrochemical windows, and severe interfacial deterioration limit their practical implementations. Herein, an organoboron- and cyano-grafted polymer electrolyte (PVNB) was designed using vinylene carbonate as the polymer backbone and organoboron-modified poly(ethylene glycol) methacrylate and acrylonitrile as the grafted phases, which may facilitate Li-ion transport, immobilize the anions, and enlarge the oxidation voltage window; therefore, the well-tailored PVNB exhibits a high Li-ion transference number (t_Li⁺ = 0.86), a wide electrochemical window (>5 V), and a high ionic conductivity (σ = 9.24 × 10^-4 S cm^-1) at room temperature (RT). As a result, the electrochemical cyclability and safety of the Li|LiFePO₄ and Li|LiNi_0.8Co_0.1Mn_0.1O₂ cells with in situ polymerization of PVNB are substantially improved by forming the stable organic-inorganic composite cathode electrolyte interphase (CEI) and the Li₃N-LiF-rich solid electrolyte interphase (SEI).

Extremely Tough, Stretchable Gel Electrolytes with Strong Interpolymer Hydrogen Bonding Prepared Using Concentrated Electrolytes to Stabilize Lithium-Metal Anodes

Extremely tough and stretchable gel electrolytes, which can be prepared by leveraging the strong interpolymer hydrogen bonding in concentrated lithium (Li)-salt electrolytes, are reported. These electrolytes can be realized by optimizing the competitive hydrogen-bonding interactions between polymer chains, solvent molecules, Li cations, and counteranions. Free polar solvent molecules, which typically impede interpolymer hydrogen bonding, are scarce in concentrated electrolytes; this feature can be exploited to prepare hydrogen-bonded gel electrolytes with unprecedented toughness. In contrast, free solvent molecules are abundant in electrolytes with typical concentrations, yielding considerably weaker gel electrolytes. The tough gel electrolyte can be used an artificial protective layer for Li-metal anodes, as it considerably enhances the cycling stability of a Li symmetric cell through uniform Li deposition/dissolution. Additionally, employing the gel electrolyte as the protecting layer significantly improves the cycling performance of the Li||LiNi_0.6 Co_0.2 Mn_0.2 O₂ full cell.

Molecular Self-Assembled Ether-Based Polyrotaxane Solid Electrolyte for Lithium Metal Batteries

Poly(ethylene oxide) has been widely investigated as a potential separator for solid-state lithium metal batteries. However, its applications were significantly restricted by low ionic conductivity and a narrow electrochemical stability window (<4.0 V vs Li/Li⁺) at room temperature. Herein, a novel molecular self-assembled ether-based polyrotaxane electrolyte was designed using different functional units and prepared by threading cyclic 18-crown ether-6 (18C6) to linear poly(ethylene glycol) (PEG) via intermolecular hydrogen bond and terminating with hexamethylene diisocyanate trimer (HDIt), which was strongly confirmed by local structure-sensitive solid/liquid-state nuclear magnetic resonance (NMR) techniques. The designed electrolyte has shown an obviously increased room-temperature ionic conductivity of 3.48 × 10^-4 S cm^-1 compared to 1.12 × 10^-5 S cm^-1 without assembling polyrotaxane functional units, contributing to the enhanced cycling stability of batteries with both LiFePO₄ and LiNi_0.8Co_0.15Al_0.05O₂ cathode materials. This advanced molecular self-assembled strategy provides a new paradigm in designing solid polymer electrolytes with demanded performance for lithium metal batteries.

Insights into the use of polyepichlorohydrin polymer in lithium battery energy storage/conversion devices: review

Abstract

In this paper, the up-to-date state of polyepichlorohydrin-based electrolytes is reviewed. Research works are persistently ongoing to develop free-standing solid polymer electrolytes with exceptional performances and stabilities that can suit the needs of present and next-generation technologies. Polyepichlorohydrin (PECH), for example, is one of the polymer hosts under consideration due to its ether electron donor groups that deliver coordinating spots for cation transport as well as alkyl chloride groups for changing its surface character. Because of this structure, PECH has certain incredible characteristics including small glass transition temperature (Tg), tremendous flexibility, as well as the power to form complexation with diverse salts. Furthermore, the alkyl chloride groups serve as a location for surface modification of the polymer via nucleophilic substitution reactions, resulting in surface changes or bulk properties. As a result, the PECH in chemically modified or pristine form is an emerging option that has been researched and is being considered for use in energy storage devices. This paper reviews the latest studies on the improvements of PECH-based electrolytes for lithium-based battery storage systems. The synthesis methods of PECH polymer, types of lithium batteries, and opportunities and challenges of lithium batteries have been presented briefly. Findings on PECH-based electrolytes have been presented and discussed thoroughly. Lastly, the paper presents, battery performance needs, and cation transportation mechanisms as well as future prospects for the advancement of PECH electrolytes in the field of storage systems.

Article Highlights

UV-derived double crosslinked PEO-based solid polymer electrolyte for room temperature

The low ionic conductivity at room temperature and poor dimensional stability at high temperature of polyethylene oxide (PEO)-based solid electrolytes greatly limit the development and utilization of solid polymer electrolytes (SPEs). To reconcile the contradiction between electrochemical performance and mechanical strength of PEO-based SPEs, a cross-linking structure with active -CH2CH2O- soft chains that doped with rigid segments is designed and prepared through a method of green ultraviolet irradiation without solvent. The obtained solid film shows a high ionic conductivity of 0.2 mS·cm-1 and an ionic transference number of 0.51 at room temperature. The activation energy value of 1.92 kJ·mol-1 gives evidence for a favorable migration mechanism of PTP-SPE. A combination of flexibility and strength can be realized by molecular structure design with a tensile elongation of 40%. The reversible overpotential in galvanostatic cycling over 500 h of a Li||Li symmetrical cell indicates that the compact PTP-SPE can inhibit the formation of lithium dendrites. This work provides a new strategy for designing high-performance composite solid electrolytes at room temperature.

Self-Repairable and Flexible Polymer Network Electrolyte with Enhanced Lithium-Ion Conduction for Lithium Metal Batteries

Developing high-performance functional polymer-based electrolytes is important for realizing next generation safe lithium metal batteries. In this study, a new type of quasi-solid polymer network electrolyte (SIPH-x-y%) was prepared by combining synthesized polymer network (SIPH) containing urethane bond linked ionic liquids (ILs), polyethylene glycol (PEG), and disulfide bond moieties, lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI), and glyme type additive. It was found that SIPH-20-40% was mechanically flexible, self-healable, and showed high ionic conductivity of 2.67×10^-4  S cm^-1 . Also, SIPH-20-40% possesses a high lithium ion transference number of 0.43 and good electrochemical stability. These properties enabled the SIPH-20-40% electrolyte membrane to support Li/Li symmetrical cell to cycle stably during long term Li plating and stripping. The Li/SIPH-20-40%/LFP showed high delivered specific capacity and good stability (166.1 mAh g^-1 after 106 cycles at 0.2 C). Such glyme doped polymer network electrolyte provides new experimental findings for developing polymer-based electrolyte with excellent mechanical integrity and battery related properties.

Increasing the ionic conductivity and lithium-ion transport of photo-cross-linked polymer with hexagonal arranged porous film hybrids

High ionic conductivity, suitable mechanical strength, and electrochemical stability are the main requirements for high-performance poly(ethylene oxide)-based electrolytes. However, the low ionic conductivity owing to the crystallinity of the ethylene oxide chain that limits the discharge rate and low-temperature performance has restricted the development and commercialization of these electrolytes. Lithium electrolytes that combine high ionic conductivity with a high lithium transference number are rare and are essential for high-power batteries. Here, we report hexagonal arranged porous scaffolds for holding prototype polyethylene glycol-based composite electrolytes containing solvate ionic liquid. The appealing electrochemical and thermal properties indicate their potential as electrolytes for safer rechargeable lithium-ion batteries. The porous scaffolds in the composite electrolytes ensure better electrochemical performance towing to their shortened pores (sizes of 3-14 μm), interconnected pathways, and improved lithium mobility. We demonstrate that both molecular design and porous microstructures are essential for improving performance in polymer electrolytes.

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Robust HCPE films were fabricated using the breath-figure method

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HCPE shows high ionic conductivity of 6.66 × 10⁻⁴ S cm⁻¹

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HCPE exhibits ESW of 4.7 V vs Li+/Li at 60°C and excellent compatibility with Li

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Molecular design and porous-microstructures are essential for electrolyte performance

New insights on the origin of chemical instabilities between poly(carbonate)-based polymer and Li-containing inorganic materials

Composites electrolytes, owing to their potential to combine both polymeric and ceramic properties, are promising candidates for Solid-State-Batteries (SSBs). Here, we assessed the effect of ceramic fillers (Li1+xAlxTi2-xP3O12, Li6.55Ga0.15La3Zr2O12, Al2O3) in a poly(ethylene oxide carbonate)-LiTFSI. First, the role of filler chemistry on thermal and electrochemical properties is evaluated: the polymer crystallinity is reduced, resulting in a gain of ionic conductivity at low temperatures; and the ionic conductivity at low temperature (<30 °C) is boosted for LLZO filler particles. This behaviour is commonly attributed to new conduction pathways generated within the fillers; however, here we demonstrate that a polymer degradation induced by the filler chemistry modifies the polymer chemistry in poly(ethylene glycol), initiated by LiOH that can be found on the LLZO surface. The electrolyte containing LATP or Al2O3 does not under any degradation. Hence, special attention must be paid to surface impurities, as instability/degradation may occur.

Polyethylene-oxide: NaI polymer electrolyte: Electrical, structural and photoelectrochemical studies- RAFM

Conducting sodium iodide (NaI) doped polyethylene oxide (PEO) freestanding electrolyte films are prepared by solution cast technique. Electrical, Structural, and device performances are given in detail. Maximum conducting polymer electrolyte has been used to develop electric double-layer capacitors (EDLCs) as well as the dye-sensitized solar cell (DSSC) which shows that ion-conducting polymer electrolyte is a novel candidate for energy devices.

A Smart Lithium Battery with Shape Memory Function

Rapidly growing flexible and wearable electronics highly demand the development of flexible energy storage devices. Yet, these devices are susceptible to extreme, repeated mechanical deformations under working circumstances. Herein, the design and fabrication of a smart, flexible Li-ion battery with shape memory function, which has the ability to restore its shape against severe mechanical deformations, bending, twisting, rolling or elongation, is reported. The shape memory function is induced by the integration of a shape-adjustable solid polymer electrolyte. This Li-ion battery delivers a specific discharge capacity of ≈140 mAh g^-1 at 0.2 C charge/discharge rate with ≈92% capacity retention after 100 cycles and ≈99.85% Coulombic efficiency, at 20 °C. Besides recovery from mechanical deformations, it is visually demonstrated that the shape of this smart battery can be programmed to adjust itself in response to an internal/external heat stimulus for task-specific and advanced applications. Considering the vast range of available shape memory polymers with tunable chemistry, physical, and mechanical characteristics, this study offers a promising approach for engineering smart batteries responsive to unfavorable internal or external stimulus, with potential to have a broad impact on other energy storage technologies in different sizes and shapes.

Ion-Conducting Flexible Thin Films of Composites from Poly(ethylene oxide) and Nematic Liquid Crystals E8-Characterization by Impedance and Dielectric Relaxation Spectroscopy

Complex electrical impedance and dielectric spectroscopy were applied to study the dielectric relaxations and their thermal behavior in ion-conducting composites/complexes from polymer poly(ethylene oxide) (PEO) and E8 nematic liquid crystals (LCs), at the compositional ratio PEO:E8 = 70:30 wt%. Flexible thin films of PEO/E8 with a thickness of 150 μm were inspected, as well as such films from Na+ ion-conducting electrolyte PEO/E8/NaIO4 with the same PEO:E8 compositional ratio, but additionally containing 10 wt.% from the salt sodium metaperiodate (NaIO4) as a dopant of Na+ ions. The molecular dynamics, namely the dielectric relaxation of PEO/E8 and PEO/E8/NaIO4, were characterized through analyses of complex impedance and dielectric spectra measured in the frequency range of 1 Hz-1 MHz, under variation of temperature from below to above the glass-transition temperature of these composites. The relaxation and polarization of dipole formations in PEO/E8 and PEO/E8/NaIO4 were evidenced and compared in terms of both electrical impedance and dielectric response depending on temperature. The results obtained for molecular organization, molecular relaxation dynamics, and electric polarization in the studied ion-conducting polymer/LC composites/complexes can be helpful in the optimization of their structure and performance, and are attractive for applications in flexible organic electronics, energy storage devices, and mechatronics.

Development on Solid Polymer Electrolytes for Electrochemical Devices

Electrochemical devices, especially energy storage, have been around for many decades. Liquid electrolytes (LEs), which are known for their volatility and flammability, are mostly used in the fabrication of the devices. Dye-sensitized solar cells (DSSCs) and quantum dot sensitized solar cells (QDSSCs) are also using electrochemical reaction to operate. Following the demand for green and safer energy sources to replace fossil energy, this has raised the research interest in solid-state electrochemical devices. Solid polymer electrolytes (SPEs) are among the candidates to replace the LEs. Hence, understanding the mechanism of ions' transport in SPEs is crucial to achieve similar, if not better, performance to that of LEs. In this paper, the development of SPE from basic construction to electrolyte optimization, which includes polymer blending and adding various types of additives, such as plasticizers and fillers, is discussed.

Layer-by-Layer Assembly of Strong Thin Films with High Lithium Ion Conductance for Batteries and Beyond

Polyethylene oxide (PEO) is one of the most widely used polymeric ion conductors which has the potential for a wide range of applications in energy storage. The enhancement of ionic conductivity of PEO-based electrolytes is generally achieved by sacrificing the mechanical properties. Using layer-by-layer (LbL) self-assembly with a nanoscale precision, mechanically strong and self-healable PEO/polyacrylic acid composite thin films with a high Li⁺ conductivity of 2.3 ± 0.8 × 10^-4 S cm^-1 at 30 °C, and a strength of 3.7 MPa is prepared. These values make the LbL composite among the best recorded multifunctional solid electrolytes. The electrolyte thin film withstands at least 1000 cycles of striping/plating of Li at 0.05 mA cm^-2 . It is further shown that the LbL thin films can be used as separators for Li-ion batteries to deliver a capacity of 116 mAh g^-1 at 0.1 C in an all-LbL-assembled lithium iron phosphate/lithium titanate battery. Finally, it is demonstrated that the thin films can be used as ion-conducting substrates for flexible electrochemical devices, including micro supercapacitors and electrochemical transistors.

UV-Cured Cross-Linked Astounding Conductive Polymer Electrolyte for Safe and High-Performance Li-Ion Batteries

UV-cured cross-linked polymer electrolytes are promising electrolytes for safe Li-ion batteries (LIBs) application due to their excellent conduction ability, low glass-transition temperature (T_g), and high discharge capacity. Herein, we have prepared novel fluorosulfonylimide methacrylic-based cross-linked polymer electrolyte membranes for LIBs via UV-curing process, which is a well-known, easy, low-cost, fast, and reliable technique. The synthesized UV-reactive novel methacrylate monomer with directly attached fluorosulfonylimide functional group methacryloylcarbamoyl sulfamoyl fluoride (MACSF) was used as a precursor for UV curing along with poly(ethylene glycol) dimethacrylate (PEGDMA) and lithium bis(fluorosulfonyl)imide (LiFSI). The results demonstrated that the cross-linked membrane with an optimized amount (30 wt %) of MACSF monomer (noted as CPE-3) showed the best performance. The nonflammable fluorosulfonyl group (a hydrophilic group of MACSF monomer) in the polymer matrix formed a wide channel, as a result of which Li ion can migrate easily via forming an ionic linkage. The CPE-3 electrolyte exhibited a low T_g (-79 °C), excellent phase separation, high conductivity (σ) (ca. 3.5 × 10^-4 and 8.50 × 10^-3 S·cm^-1 at 30 and 80 °C, respectively), and high flame retardancy. The battery performance of half-cell (LiFePO₄/CPE-3/Li) and full cell (LiFePO₄/CPE-3/graphite) with CPE-3 electrolyte were attractive: discharge capacities (155 and 152 mAh/g) with the capacity retentions of 96.17 and 95.17% after 500 cycles at 0.1 C rate for half-cell and full-cell LIBs, respectively.

Addressing Manufacturability and Processability in Polymer Gel Electrolytes for Li/Na Batteries

Gel electrolytes are prepared with Ultra High Molecular Weight (UHMW) polyethylene oxide (PEO) in a concentration ranging from 5 to 30 wt.% and Li- and Na-doped 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14-TFSI) by a simple procedure consisting of dissolving PEO by melting it directly in the liquid electrolyte while stirring the blend. This procedure is fast, reproducible and needs no auxiliary solvents, which makes it sustainable and potentially easy to scale up for mass production. The viability of the up-scaling by extrusion has been studied. Extrusion has been chosen because it is a processing method commonly employed in the plastics industry. The structure and morphology of the gel electrolytes prepared by both methods have been studied by DSC and FTIR, showing small differences among the two methods. Composite gels incorporation high concentrations of surface modified sepiolite fibers have been successfully prepared by extrusion. The rheological behavior and ionic conductivity of the gels have been characterized, and very similar performance of the extruded and manually mixed gels is detected. Ionic conductivity of all the gels, including the composites, are at or over 0.4 mS cm^-1 at 25 °C, being at the same time thermoreversible and self-healing gels, tough, sticky, transparent and stretchable. This combination of properties, together with the viability of their industrial up-scaling, makes these gel electrolyte families very attractive for their application in energy storage devices.

Cation-Assisted Lithium-Ion Transport for High-Performance PEO-based Ternary Solid Polymer Electrolytes

N-alkyl-N-alkyl pyrrolidinium-based ionic liquids (ILs) are promising candidates as non-flammable plasticizers for lowering the operation temperature of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs), but they present limitations in terms of lithium-ion transport, such as a much lower lithium transference number. Thus, a pyrrolidinium cation was prepared with an oligo(ethylene oxide) substituent with seven repeating units. We show, by a combination of experimental characterizations and simulations, that the cation's solvating properties allow faster lithium-ion transport than alkyl-substituted analogues when incorporated in SPEs. This proceeds not only by accelerating the conduction modes of PEO, but also by enabling new conduction modes linked to the solvation of lithium by a single IL cation. This, combined with favorable interfacial properties versus lithium metal, leads to significantly improved performance on lithium-metal polymer batteries.

A universal strategy to improve interfacial kinetics of solid supercapacitors used in high temperature

The growing application domain of energy storage devices (ESDs) is leading research to temperature tolerant supercapacitors. To realize reliable and safe devices, high modulus solid electrolytes are favored by most researchers. However, the inferior infiltrating ability of such electrolytes usually results in poor electrochemical performances of the ESDs. Herein, we adopted a hierarchical optimization strategy to address the aforementioned interfacial issues. Continuous ionic percolation throughout the hierarchical pores of the 3D electrode was formed by in-situ introducing an ionogel buffer layer. Benefiting from this, the rate of ions diffusing within electrodes was increased by 5 times. Furthermore, the kinetics of ions entering into nanopores was improved via introducing small size ions into ionic liquids (ILs) and adjusting the solvated structures. Both the capacity and rate performance of the electrochemical double layer capacitors (EDLCs) were improved. Additionally, the buffer layer exhibited sufficient thermostability to cooperate with poly(ether ether ketone) (PEEK)-based solid electrolyte. Consequently, the EDLCs exhibited excellent cycling stability (79% capacitance retention after 5000 cycles) at 120 °C and delivered a maximum energy density of 46.9 Wh kg^-1 with a power density of 926.9 W kg^-1. Our strategy is believed to be effective to cooperate with various solid electrolyte systems and offer a general design principle for durable and high performance EDLCs.

Gel-polymer electrolytes based on polyurethane ionomers for lithium power sources

Polyurethanes based on the aminoethers of ortho-phosphoric acid and polyisocyanates of an aliphatic nature were studied as a substrate for the preparation of new polymer electrolyte. The conductivity of polyurethane ionomer samples obtained using the optimal amount of aliphatic polyisocyanates and after keeping them in a 1 M LiBF₄ solution in γ-butyrolactone reaches 0.62 mS cm⁻¹. It has been established that the transport of positively charged ions through the polymer matrix is due to the formation of clusters of phosphate ions and their association into the conducting channels. The introduction of carboxylate ions into the conducting channels by modifying the aminoethers of ortho-phosphoric acid with phthalic anhydride leads to an increase in their size and rise in the mobility of cations. As a result, the conductivity of polyurethane gel electrolytes increased to 2.1 mS cm⁻¹.

Polyurethanes based on the aminoethers of ortho-phosphoric acid and polyisocyanates of an aliphatic nature were studied as a substrate for the preparation of a new polymer electrolyte.

UV-Cured Poly(Siloxane-Urethane)-Based Polymer Composite Materials for Lithium Ion Batteries-The Effect of Modification with Ionic Liquids

The results of studies on the synthesis and characterization of conductive polymer composite materials designed as potential separators for lithium ion batteries are presented. The conductive polymer composites were prepared from UV-cured poly(siloxane-urethanes)s (PSURs) containing poly(ethylene oxide) (PEO) segments and modified with lithium salts and ionic liquids (ILs). The most encouraging results in terms of specific conductivity and mechanical properties of the composite were obtained when part of UV-curable PSUR prepolymer was replaced with a reactive UV-curable IL. Morphology of the composites modified with ILs or containing a standard ethylene carbonate/dimethyl carbonate mixture (EC/DMC) as solvent was compared. It was found that the composites showed a two-phase structure that did not change when non-reactive ILs were applied instead of EC/DMC but was much affected when reactive UV-curable ILs were used. The selected IL-modified UV-cured PSUR composite that did not contain flammable EC/DMC solvent was preliminarily tested as gel polymer electrolyte and separator for lithium ion batteries.

Investigating the Effects of Lithium Phosphorous Oxynitride Coating on Blended Solid Polymer Electrolytes

Solid-state electrolytes are very promising to enhance the safety of lithium-ion batteries. Two classes of solid electrolytes, polymer and ceramic, can be combined to yield a hybrid electrolyte that can synergistically combine the properties of both materials. Chemical stability, thermal stability, and high mechanical modulus of ceramic electrolytes against dendrite penetration can be combined with the flexibility and ease of processing of polymer electrolytes. By coating a polymer electrolyte with a ceramic electrolyte, the stability of the solid electrolyte is expected to improve against lithium metal, and the ionic conductivity could remain close to the value of the original polymer electrolyte, as long as an appropriate thickness of the ceramic electrolyte is applied. Here, we report a bilayered lithium-ion conducting hybrid solid electrolyte consisting of a blended polymer electrolyte (BPE) coated with a thin layer of the inorganic solid electrolyte lithium phosphorous oxynitride (LiPON). The hybrid system was thoroughly studied. First, we investigated the influence of the polymer chain length and lithium salt ratio on the ionic conductivity of the BPE based on poly(ethylene oxide) (PEO) and poly(propylene carbonate) (PPC) with the salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The optimized BPE consisted of 100 k molecular weight PEO, 50 k molecular weight PPC, and 25(w/w)% LiTFSI, (denoted as PEO100PPC50LiTFSI25), which exhibited an ionic conductivity of 2.11 × 10-5 S/cm, and the ionic conductivity showed no thermal memory effects as the PEO crystallites were well disrupted by PPC and LiTFSI. Second, the effects of LiPON coating on the BPE were evaluated as a function of thickness down to 20 nm. The resulting bilayer structure showed an increase in the voltage window from 5.2 to 5.5 V (vs Li/Li+) and thermal activation energies that approached the activation energy of the BPE when thinner LiPON layers were used, resulting in similar ionic conductivities for 30 nm LiPON coatings on PEO100PPC50LiTFSI25. Coating BPEs with a thin layer of LiPON is shown to be an effective strategy to improve the long-term stability against lithium.

An In Situ Cross-Linked Nonaqueous Polymer Electrolyte for Zinc-Metal Polymer Batteries and Hybrid Supercapacitors

This work reports the facile synthesis of nonaqueous zinc-ion conducting polymer electrolyte (ZIP) membranes using an ultraviolet (UV)-light-induced photopolymerization technique, with room temperature (RT) ionic conductivity values in the order of 10^-3 S cm^-1 . The ZIP membranes demonstrate excellent physicochemical and electrochemical properties, including an electrochemical stability window of >2.4 V versus Zn|Zn²⁺ and dendrite-free plating/stripping processes in symmetric Zn||Zn cells. Besides, a UV-polymerization-assisted in situ process is developed to produce ZIP (abbreviated i-ZIP), which is adopted for the first time to fabricate a nonaqueous zinc-metal polymer battery (ZMPB; VOPO₄ |i-ZIP|Zn) and zinc-metal hybrid polymer supercapacitor (ZMPS; activated carbon|i-ZIP|Zn) cells. The VOPO₄ cathode employed in ZMPB possesses a layered morphology, exhibiting a high average operating voltage of ≈1.2 V. As compared to the conventional polymer cell assembling approach using the ex situ process, the in situ process is simple and it enhances the overall electrochemical performance, which enables the widespread intrusion of ZMPBs and ZMPSs into the application domain. Indeed, considering the promising aspects of the proposed ZIP and its easy processability, this work opens up a new direction for the emergence of the zinc-based energy storage technologies.

Structure, Rheology, and Electrokinetics of Soft Colloidal Suspension Electrolytes

When ion transport in a binary liquid electrolyte is driven at potentials above the thermal voltage, an extended space charge region forms at the electrolyte/electrode interface and triggers the hydrodynamic instability termed electroconvection. We experimentally show that this instability can be completely arrested in soft colloidal suspension electrolytes composed of low concentrations of polymer-grafted nanoparticles in a liquid host. The mechanism is revealed by means of X-ray scattering, Brownian dynamics calculations, and linear stability analysis to involve overlap of the soft particles at low particle fractions to create a jammed, nanoporous medium that resists convective flow by a Darcy-Brinkman like drag on the electrolyte solvent.

Properties enhancement of carboxymethyl cellulose with thermo-responsive polymer as solid polymer electrolyte for zinc ion battery

A novel polymer host from carboxymethyl cellulose (CMC)/poly(N-isopropylacrylamide) (PNiPAM) was developed for a high safety solid polymer electrolyte (SPE) in a zinc ion battery. Effects of the PNiPAM loading level in the range of 0-40% by weight ( wt%) on the chemical, mechanical, thermal, and morphological properties of the CMC/PNiPAMx films (where x is the wt% of PNiPAM) were symmetrically investigated. The obtained CMC/PNiPAMx films showed a high compatibility between the polymers. The CMC/PNiPAM20 blend showed the greatest tensile strength and modulus at 37.9 MPa and 2.1 GPa, respectively. Moreover, the thermal degradation of CMC was retarded by the addition of PNiPAM. Scanning electron microscopy images of CMC/PNiPAM20 revealed a porous structure that likely supported Zn2+ movement in the SPEs containing zinc triflate, resulting in the high Zn2+ ion transference number (0.56) and ionic conductivity (1.68 × 10-4 S cm-1). Interestingly, the presence of PNiPAM in the CMC/PNiPAMx blends showed a greater stability during charge-discharge cyclic tests, indicating the ability of PNiPAM to suppress dendrite formation from causing a short circuit. The developed CMC/PNiPAM20 based SPE is a promising material for high ionic conductivity and stability in a Zn ion battery.

Large Area, Multilayer Graphene Films as a Flexible Electronic Material

Chemically reduced graphene oxide possesses unique properties and leads to a secure processing method for many applications. The electrical and optical properties of graphene oxide are strongly dependent on the chemical and atomic structure. In the present work, the reduction of synthesized multilayer graphene oxide sheets by both chemical and thermal methods to use them as a substrate in the field of molecular electronic device fabrication is reported. 1-Dodecanethiol molecules are used to covalently bond on the surface atoms of reduced graphene oxide to constitute molecular electronic devices. The metal-organic molecules-reduced graphene oxide-metal junctions show a significant reduction in current levels and weak diode behavior. The observations confirm the tunneling as the conduction mechanism. The sheets are low cost, highly flexible, and can be used as a substrate to build the molecular electronic junctions.

Solid Polymer Electrolytes with Flexible Framework of SiO2 Nanofibers for Highly Safe Solid Lithium Batteries

Composite electrolytes consisting of polymers and three-dimensional (3D) fillers are considered to be promising electrolytes for solid lithium batteries owing to their virtues of continuous lithium-ion pathways and good mechanical properties. In the present study, an electrolyte with polyethylene oxide-lithium (bis trifluoromethyl) sulfate-succinonitrile (PLS) and frameworks of three-dimensional SiO₂ nanofibers (3D SiO₂ NFs) was prepared. Taking advantage of the highly conductive interfaces between 3D SiO₂ NFs and PLS, the total conductivity of the electrolyte at 30 °C was approximately 9.32 × 10^-5 S cm^-1. With a thickness of 27 μm and a tensile strength of 7.4 MPa, the electrolyte achieved an area specific resistance of 29.0 Ω cm². Moreover, such a 3D configuration could homogenize the electrical field, which was beneficial for suppressing dendrite growth. Consequently, Li/LiFePO₄ cells assembled with PLS and 3D SiO₂ NFs (PLS/3D SiO₂ NFs), which delivered an original specific capacity of 167.9 mAh g^-1, only suffered 3.28% capacity degradation after 100 cycles. In particular, these cells automatically shut down when PLS was decomposed above 400 °C, and the electrodes were separated by the solid framework of 3D SiO₂ NFs. Therefore, the solid lithium batteries based on composite electrolytes reported here offer high safety at elevated temperatures.

Elimination of "Voltage Noise" of Poly (Ethylene Oxide)-Based Solid Electrolytes in High-Voltage Lithium Batteries: Linear versus Network Polymers

Frequently, poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) reveal a failure with high-voltage electrodes, e.g. LiNi_0.6Mn_0.2Co_0.2O₂ in lithium metal batteries, which can be monitored as an arbitrary appearance of a “voltage noise” during charge and can be attributed to Li dendrite-induced cell micro short circuits. This failure behavior disappears when incorporating linear PEO-based SPE in a semi-interpenetrating network (s-IPN) and even enables an adequate charge/discharge cycling performance at 40°C. An impact of any electrolyte oxidation reactions on the performance difference can be excluded, as both SPEs reveal similar (high) bulk oxidation onset potentials of ≈4.6 V versus Li|Li⁺. Instead, improved mechanical properties of the SPE, as revealed by compression tests, are assumed to be determining, as they mechanically better withstand Li dendrite penetration and better maintain the distance of the two electrodes, both rendering cell shorts less likely.

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PEO-based solid polymer electrolytes (SPEs) are stable up to 4.6 V versus Li|Li⁺

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But, linear PEO-based SPE results in a “voltage noise-failure” in NMC‖Li cells

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Failure disappears when PEO is incorporated in a semi-interpenetrating network

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Charge/discharge cycling possible even at 40°C in NMC622‖Li cells

Comprehensive Review of Polymer Architecture for All-Solid-State Lithium Rechargeable Batteries

Solid-state batteries are an emerging option for next-generation traction batteries because they are safe and have a high energy density. Accordingly, in polymer research, one of the main goals is to achieve solid polymer electrolytes (SPEs) that could be facilely fabricated into any preferred size of thin films with high ionic conductivity as well as favorable mechanical properties. In particular, in the past two decades, many polymer materials of various structures have been applied to improve the performance of SPEs. In this review, the influences of polymer architecture on the physical and electrochemical properties of an SPE in lithium solid polymer batteries are systematically summarized. The discussion mainly focuses on four principal categories: linear, comb-like, hyper-branched, and crosslinked polymers, which have been widely reported in recent investigations as capable of optimizing the balance between mechanical resistance, ionic conductivity, and electrochemical stability. This paper presents new insights into the design and exploration of novel high-performance SPEs for lithium solid polymer batteries.