Quasi-solid Polymer Electrolyte Research Articles

PVDF–HFP@Nafion-based quasisolid polymer electrolyte for high migration number in working rechargeable Na–O2 batteries

PVDF–HFP@Nafion-based quasisolid polymer electrolyte for high migration number in working rechargeable Na–O2 batteries

A Dielectric MXene-Induced Self-Built Electric Field in Polymer Electrolyte Triggering Fast Lithium-Ion Transport and High-Voltage Cycling Stability.

Quasi-solid polymer electrolyte (QPE) lithium (Li)-metal battery holds significant promise in the application of high-energy-density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self-built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon-fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF-enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li-ion transfer mechanism and dual-reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF-SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm-1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self-built electric field in QPE-based high-voltage batteries.

A Dielectric MXene‐Induced Self‐Built Electric Field in Polymer Electrolyte Triggering Fast Lithium‐Ion Transport and High‐Voltage Cycling Stability

AbstractQuasi‐solid polymer electrolyte (QPE) lithium (Li)‐metal battery holds significant promise in the application of high‐energy‐density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self‐built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon‐fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF‐enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li‐ion transfer mechanism and dual‐reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF‐SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm−1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self‐built electric field in QPE‐based high‐voltage batteries.

A Healable Quasi-Solid Polymer Electrolyte with Balanced Toughness and Ionic Conductivity.

Solid polymer electrolytes (SPEs) have garnered extensive attention as potential alternatives to traditional liquid electrolytes, primarily due to their prowess in curbing lithium dendrite formation and preventing electrolyte leaks. The quest for SPEs that are both mechanically robust and exhibit superior ionic conductivity has been vigorous. However, achieving a harmonious balance between these two attributes remains a significant challenge. In this study, we introduce a novel quasi-solid electrolyte, ingeniously crafted from a poly(urethane-urea) network, enriched with lithium salts and plasticizers. This innovative composition not only boasts remarkable toughness but also ensures commendable ionic conductivity. Our post-gelation method yields gel polymer electrolytes that undergo rigorous evaluation, leading to an optimized version that stands out with its exceptional room-temperature ionic conductivity (2.94×10-4 S cm-1) and outstanding toughness (11.9 MJ m-3). Moreover, it demonstrates a broad electrochemical window (4.73 V), remarkable stability across a 600-hour cycle test, a high capacity retention exceeding 80 % after 100 cycles at 0.2 C, and a noteworthy self-healing capability. This quasi-solid polymer electrolyte emerges as a promising contender to replace current liquid electrolyte solutions.

Multiple Na+ transport pathways and interfacial compatibility enable high-capacity, room-temperature quasi-solid sodium batteries

Sodium-metal batteries (SMBs) are ideal for large-scale energy storage due to their stable operation and high capacity. However, they have safety issues caused by severe dendrite growth and side reactions, particularly when using liquid electrolytes. Therefore, it is critically important to develop electrolytes with high ionic conductivity and improved safety that are non-flammable and resistant to dendrites. Here, we developed polymerized polyethylene glycol diacrylate (PEGDA)-modified poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) electrolytes (PPEs) with highly conductive sodium bis(trifluoromethanesulfonyl)imide and corrosion-inhibitive sodium bis(oxalato)borate salts for SMBs. Well-complexed PEGDA not only increases the amorphicity of the PVDF matrix, but also offers numerous Lewis basic sites through the polar groups of carbonyl and ether groups (i.e., electron donors). The presence of the Lewis basic sites facilitates the dissociation of sodium salt and transportation of Na+ within the PVDF matrix. This results in the generation of additional Na+ transport pathways, which can enhance the performance of the battery. Among PPEs, the optimized PPE-50 exhibits a high ionic conductivity of 3.42 × 10–4 S cm−1 and a mechanical strength of 14.0 MPa. A Na||Na symmetric cell with PPE-50 displays high stability at 0.2 mA cm−2 for 800 h. PPE-50 further displays high capacity, e.g., a Na3V2(PO4)3|PPE-50|Na battery delivers a decent discharge capacity of 101.5 mAh g−1 at 1.0C after 650 cycles. Our work demonstrates the development of high-performance quasi-solid polymer electrolytes with multiple transport pathways suitable for room-temperature SMBs.

In-situ formation of quasi-solid polymer electrolyte for wide-temperature applicable Li-metal batteries

As next-generation rechargeable batteries, the development of solid-state lithium-metal batteries (LMBs) in a multitude of applications is confronted with a trade-off between high energy density, safety, and wide-temperature tolerance. Especially in cold climates, their applications are challenged by insufficient dynamics in bulk electrolyte and at electrode/electrolyte interface. Herein, a flexible, highly ionic conductive, and low-temperature applicable quasi-solid polymer electrolyte (QSPE) is designed and fabricated, which achieves a stable Li-metal anode over a wide-temperature range (−20 ∼ 60 °C). The QSPEs prepared via in-situ polymerization of polyethylene glycol (PEO)-based monomers in low-melting solvent (1,3-dioxolane (DOL) or ethyl difluoroacetate (EDFA)) endow low-temperature tolerance, prominent ionic conductivity (4.5 × 10−4 S cm−1 at −20 °C) and exceptional electrochemical performance over a wide-temperature range. Consequently, with the DOL-based QSPE (D-QSPE), the Li/D-QSPE/LiFePO4 cell presents stable, long-term cycling at −20 °C (minimal capacity degradation over 550 cycles) and excellent fast-charging capacity (capacity retention of 81 % over 1300 cycles at 5 C). Even utilizing a thin lithium foil (25 μm) and a high mass loading LiFePO4 cathode (2.5 mAh cm−2), the assembled Li/LFP cell with a N/P ratio of 1.96 still exhibits good cycling performance at −20 °C. Additionally, the EDFA-based QSPE (E-QSPE) allows LMBs with NCM811 cathodes cycling over 140 cycles (capacity retention > 95 %) at −20 °C. With the capability of circumventing sluggish ion transport kinetics of quasi-solid polymer LMBs in cold climates, the developed polymer electrolyte provides new pathways for safe, high-capability, and wide-temperature operable batteries.

Highly liquid retentive, ordered ion transport quasi-solid polymer electrolytes for lithium metal batteries

Solid-state lithium metal batteries (SSLMB) offer a compelling solution to address the low energy density issue present in current liquid lithium-ion batteries (LIB). Nevertheless, SSLMB electrolytes continue to face specific challenges that impede their commercial viability. These challenges encompass low ionic conductivity, high production cost, instability of interfacial contact, and other hurdles. In this context, a cost-effective quasi-solid polymer electrolyte (QPE) based on Polyvinylidene fluoride (PVDF) was developed to reshape the transport of lithium-ion (Li+) within the electrolyte, resulting in accelerated Li+ transport, with an achieved ionic conductivity of 0.71 mS cm−1 at 25 °C. The assembled LiFePO4|PVDF-OH|Li cell demonstrates exceptional battery performance, boasting an initial capacity of 145.9 mAh/g at 30 °C and maintaining an impressive capacity retention of 85.4 % even after 1000 cycles. The experimental findings underscore the critical role played by the immobilized solvent within the innovative PVDF-based QPE in facilitating the migration of Li+, consequently enhancing electrochemical performance. This study showcases a pioneering approach aimed at enhancing ionic conductivity, representing a significant stride towards the development of low-cost, high-performance, and easily processable solid polymer electrolytes, with potential implications for broader research in the field of energy storage systems.

Retarding anion migration for alleviating concentration polarization towards stable polymer lithium-metal batteries

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries (LMBs). Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers (SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte (QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt, delivering a high lithium-ion transference number (0.75) and satisfactory ionic conductivity (1.16 × 10−3 S cm−1 at 30 °C). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 °C. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithium-ions migration for high-performance polymer LMBs.

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.

Unconventional PEO-PPC quasi-solid state blend polymer electrolyte for high efficiency solid-state Li-metal batteries

Polymer electrolytes represent a safer alternative over traditional liquid electrolytes, enabling the use of higher energy density active materials as electrodes for batteries. Among the wide variety of different polymeric matrix that are currently been proposed, polyethylene oxide (PEO) is considered one of the most promising. In this work, a PEO-based quasi-solid polymer electrolyte (QSPE) was produced by easily scalable solution casting technique, optimized with addition of plasticizers and blended with polypropylene carbonate (PPC). The resulting polymer electrolyte was ultimately supported to glass fiber separator. Improvement of ionic conductivity, transfer number and electrochemical stability window of the different formulations was confirmed through electrochemical impedance spectroscopy and linear sweep voltammetry. Plating and stripping tests in symmetric LiLi cells and charge–discharge tests in half-cell configuration (Li vs LFP) were performed to evaluate the cyclability and stability of the QSPEs. The PEO-PPC polymer electrolyte showed improved efficiency and stability during charge–discharge cycles, at room temperature, suggesting the positive effect of the presence of carbonate groups in the polymer matrix. The promising results demonstrate that the as-prepared QSPE could represent a feasible and viable alternative to conventional liquid electrolytes and could accelerate the adoption of high energy density storage systems, like Li-metal batteries.

In situ-fabricated quasi-solid polymer electrolytes incorporating an ionic liquid for flexible supercapacitors

A quasi-solid polymer electrolyte is fabricated by an in situ polymerization of PEGDMA in AN solvent based on a thermal initiation mechanism and incorporating the ionic liquid EMITFSI for application in flexible supercapacitors.

A Fully Amorphous, Dynamic Cross-Linked Polymer Electrolyte for Lithium-Sulfur Batteries Operating at Subzero-Temperatures.

Solid-state lithium-sulfur batteries have shown prospects as safe, high-energy electrochemical storage technology for powering regional electrified transportation. Owing to limited ion mobility in crystalline polymer electrolytes, the battery is incapable of operating at subzero temperature. Addition of liquid plasticizer into the polymer electrolyte improves the Li-ion conductivity yet sacrifices the mechanical strength and interfacial stability with both electrodes. In this work, we showed that by introducing a spherical hyperbranched solid polymer plasticizer into a Li+ -conductive linear polymer matrix, an integrated dynamic cross-linked polymer network was built to maintain fully amorphous in a wide temperature range down to subzero. A quasi-solid polymer electrolyte with a solid mass content >90 % was prepared from the cross-linked polymer network, and demonstrated fast Li+ conduction at a low temperature, high mechanical strength, and stable interfacial chemistry. As a result, solid-state lithium-sulfur batteries employing the new electrolyte delivered high reversible capacity and long cycle life at 25 °C, 0 °C and -10 °C to serve energy storage at complex environmental conditions.

Anionic Anchoring Enhanced Quasi Solid Composite Polymer Electrolytes for High Performance Lithium Metal Battery.

Herein, ZIF-8 inorganic particles with different sized reinforced poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) solid composite polymer electrolytes (PVDF-HFP/10%ZIF-8) were prepared via a facile blade-coating approach, and free-standing quasi solid-state composite electrolytes (PVDF-HFP/10%ZIF-8(0.6)/Plasticizer, abbreviated as PH/10%ZIF-8(0.6)/P), were further obtained through the introduction of plasticizer. Optimized PH/10%ZIF-8(0.6)/P exhibited a high ionic conductivity of 2.8 × 10-4 S cm-1 at 30 °C, and superior Li+ transfer number of 0.89 with an ultrathin thickness (26 µm). Therefore, PH/10%ZIF-8(0.6)/P could effectively inhibit the growth of lithium dendrites, and the assembled Li/LiFePO4 cell delivered good cycling stability with a capacity retention rate of 89.1% after 100 cycles at 0.5 C.

A quasi‐solid polymer electrolyte‐based structural battery with high mechanical and electrochemical performance

AbstractStructural batteries are attractive for weight reduction in electric transportation. For their practical applications excellent mechanical properties and electrochemical performance are required simultaneously, which remains a grand challenge. In this study, we present a new scalable and low‐cost design, which uses a quasi‐solid polymer electrolyte (QSPE) to achieve both remarkably improved flexural properties and attractive energy density. The QSPE has a high ionic conductivity of 1.2 mS cm−1 and retains 91% capacity over 500 cycles in graphite/NMC532 cells. Moreover, the resulting structural batteries achieved a modulus of 21.7 GPa and a specific energy of 127 Wh kg−1 based on the total cell weight, which to our knowledge is the highest reported value above 15 GPa. We further demonstrate the application of such structural batteries in a model electric car. The presented design concept enables the industrialization of structural batteries in electric transportation and further applications to improve energy efficiency and multifunctionality.image

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

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

A quasi-solid state polymer electrolyte for high-rate and long-life sodium-metal batteries

High-energy rechargeable sodium metal batteries, featuring quasi-solid polymer electrolytes (QSSPEs), hold the promise of improved safety. However, the low ionic conductivity and limited cyclability of QSSPEs at room temperature have paralyzed the efforts to develop energy-dense metal anode batteries. Herein, we report a QSSPE comprising a blend of polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG). Notably, the porosity and the electrolyte uptake capacity of the QSSPE are highly responsive to the concentration of PEG. The optimized PVP-based QSSPE (PVP-PEG 70 30) shows a high ionic conductivity of 1.06 mS cm−1 at room temperature, along with a high transference number of approximately 0.81. A sodium symmetric cell using PVP-PEG 70 30 demonstrates reversible stripping/plating of sodium for over 700 h at a current density of 1 mA cm−2. Furthermore, PVP-PEG 70 30 alters the localized chemistry of the solid electrolyte interphases (SEIs), facilitating the formation of fluorine-rich SEIs. When coupled with a Prussian blue cathode and sodium metal anode, a full cell employing PVP-PEG 70 30 exhibits an initial discharge capacity of 168 mAh g−1, with an average discharge capacity of 125 mAh g−1 for over 600 cycles at 0.5C. Remarkably, this cell can be cycled stably and reversibly at a high rate of 6.5C. These results suggest that PVP-based QSSPE holds great promise as an electrolyte candidate for high-performance sodium metal batteries.

In situ generated of hybrid interface in poly(1,3-dioxolane) quasi solid electrolyte and extended sulfone cosolvent for lithium-metal batteries

The practical application of lithium metal batteries with high energy density are difficult to apply due to the problem of uncontrolled lithium dendrite growth with commercial liquid electrolytes. Herein, we designed a poly 1,3-dioxolane (PDOL) based quasi solid polymer electrolyte with in-situ polymerization. A small amount of lithium difluoro(oxalato)borate (LiDFOB) provides cationic initiation center for the polymerization of dioxolane (DOL). Sulfolane (SL) were further introduced into the system as a cosolvent and the ionic conductivity was increased to 3.22 × 10-4 S cm-1followed with a high Li+ transfer number of 0.73 at room temperature. Trace amount of SbF3 was introduced to form a robustness inorganic-rich hybrid interface that reduces the decomposition of electrolyte components and retards the formation of lithium dendrites during cycling. The superior rate performance and stable 5C long cycle performance are obtained in LiFePO4||Li full cell owing to the interaction between Li+, SL and PDOL. This work expands the choice of components in quasi solid electrolytes to manufacture qualified LMBs with enhanced performance.

Fluorinated Solid Electrolyte Interphase Derived From Fluorinated Polymer Electrolyte To Stabilize Li Metal.

Unstable interface between highly reductive Li metal and a conventional liquid electrolyte leads to uncontrollable Li dendrites and Li pulverization, thus limiting the practical applications of Li metal batteries with high energy density. Herein, a fluorinated quasi-solid polymer electrolyte is synthesized to stabilize Li metal via the C-F/LiF enriched solid electrolyte interphase (SEI) derived from the fluorinated polymer skeleton. Benefiting from the homogenized ion plating/stripping process guided by lithophilic C-F and rapid Li+ transportation assisted by LiF, Li dendrites and Li pulverization are suppressed. As a result, the Li||Li symmetrical cell with the fluorinated quasi-solid polymer electrolyte remains stable over 1400 h at a current density of 0.3 mA cm-2 . LiNi0.8 Co0.1 Mn0.1 O2 ||Li battery delivers a long-term cycling performance, where the capacity retains 87.77 % of its initial state after 300 cycles at 0.5 C in the voltage range from 2.8 to 4.4 V.

Solvent-free quasi-solid polymer electrolyte with a high dielectric constant for stable lithium metal anodes

Developing Li-metal batteries (LMBs) requires stability and uniform deposition of lithium during operation. However, lithium dendrites and the extremely low conductivity of the quasi-solid polymer electrolyte (qSPE) limit their performance. A high-throughput screen has been carried out here with the assistance of artificial intelligence (AI) to find a promising electrolyte material – Lithium stearate, which is first used to prepare and form qSPE. The qSPE is named as lithium stearate electrolyte (LST) possessing high Li+ ionic transference number (0.67) and conductivity (8.08 × 10−4 S cm−1) at 25 °C, which is attributed to the lithium stearate interweaving and poly(tetrafluoroethylene) (PTFE) fibrilization. Furthermore, the ultrahigh dielectric properties (ε = 792 @ 100 Hz) of LST fixed the anti-ion pair, (stable anion) minimized the space charge region on the surface of the anode. At the same time, the higher LUMO value of LST inhibits the Li-dendrite growth effectively. The excellent properties of quasi-solid polymer electrolytes make them suitable to be used in solid LMBs.

Low-Cost, High-Strength Cellulose-based Quasi-Solid Polymer Electrolyte for Solid-State Lithium-Metal Batteries.

Solid-state lithium-metal batteries are considered as the next generation of high-energy-density batteries. However, their solid electrolytes suffer from low ionic conductivity, poor interface performance, and high production costs, restricting their commercial application. Herein, a low-cost cellulose acetate-based quasi-solid composite polymer electrolyte (C-CLA QPE) was developed with a high Li+ transference number ( ) of 0.85 and excellent interface stability. The prepared LiFePO4 (LFP)|C-CLA QPE|Li batteries exhibited excellent cycle performance with a capacity retention of 97.7 % after 1200 cycles at 1 C and 25 °C. The experimental results and Density Function Theory (DFT) simulation revealed that the partially esterified side groups in the CLA matrix contribute to the migration of Li+ and enhance electrochemical stability. This work provides a promising strategy for fabricating cost-effective, stable polymer electrolytes for solid-state lithium batteries.