Composite Polymer Electrolyte Membranes Research Articles

Building Bulk and Interface Dual Fast Li+ Conducting Pathway in Composite Solid Polymer Electrolyte Membrane for All–Solid–State Lithium–Metal Batteries

AbstractSolid polymer electrolytes (SPEs) are considered a promising solution to the safety problems of lithium‐ion batteries (LIBs) using liquid electrolytes. However, the high crystallinity and low ionic conductivity hinder the practical application of SPEs. Herein, we design a composite solid polymer electrolyte with a dual fast Li+ conducting pathway in bulk and interface by incorporating highly Li+ conductive ceramic Li6.4Ga0.2La3Zr2O12 (LGLZO) in polyethylene oxide (PEO)/Li–bis (trifluoromethanesulfonyl) imide (LiTFSI) system. Compared to Li6.5La3Zr1.5Ta0.5O12 (LLZTO), LGLZO provides better Li+ conductivity; therefore, a fast Li+ conducting pathway will form in the bulk of LGLZO nanofillers. Besides, LGLZO nanofiller accelerates the dissociation of LiTFSI and benefits the transfer of free Li+ through the SPEs near the LGLZO surface, forming another interface fast Li+ conducting pathway in the SPEs. Benefits from the dual fast Li+ pathway design, the composite electrolyte membrane with 15 wt % LGLZO nanoparticles presents a high ionic conductivity of 8.0×10−4 S cm−1 at 60 °C. The Li−Li symmetric cells with optimized content LGLZO show good cycling stability (no short circuit even after 1000 h), and the all–solid Li/LiFePO4 batteries exhibit excellent cycling performance (remained 154 mAh g−1 after 500 cycles at 0.2 C under 60 °C).

Sulfonated poly(ether ether ketone)-Protic ionic Liquid-Based anhydrous Proton-Conducting composite polymer electrolyte membranes for High-Temperature fuel cell applications

A high-temperature polymer electrolyte membrane fuel cell (PEMFC) has enormous potential to produce clean energy with minimal environmental pollution along with high energy density and conversion efficiency. In the present work, anhydrous proton-conducting polymer electrolyte membranes for prospective high-temperature fuel cell application were successfully prepared using different protic ionic liquids (PILs) and sulfonated poly(ether ether ketone) (SPEEK). The protic ionic liquids (PILs), 2-hydroxyethylammonium formate, diethylmethyl ammonium triflate, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 1,2-dimethyl imidazolium bis(trifluoro methylsulfonyl)imide, and diethylmethylammonium methanesulfonate were selected based on their favorable physicochemical properties. The effect of the incorporation of the PIL on the structural, thermal, and electrical transport properties of the composite SPEEK polymer electrolyte membranes was studied. The prepared polymer electrolyte membranes (PEMs) were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and electrochemical impedance spectroscopy (EIS) techniques. FTIR results indicated an interaction between the PIL and the SPEEK, which resulted in homogeneous and flexible membranes. The DSC results confirmed good miscibility and elucidated plasticizing effect of the incorporated PIL on the SPEEK polymer matrix. All the PEMs showed good thermal stability and high-temperature anhydrous proton conductivity, achieving best proton conductivity, ≈8 × 10–3 S cm−1 at 120 °C and low activation energy ≈0.26 eV, making it suitable for prospective high-temperature PEMFC applications.

Reinforced flexible solid-state electrolyte membrane by polyurethane polymer of intrinsic microporosity for high-energy-density lithium metal battery

Poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are restricted in commercial applications due to the low ionic conductivity at ambient temperature and fragile mechanical properties. Polyurethanes (PUs) are unique materials coupled with superior rigidity and flexibility. Herein, we designed a novel polyurethane polymer of intrinsic microporosity (PPU), which was incorporated with PEO-based polymer electrolyte to prepare composite polymer electrolyte (CPE). The physicochemical and electrochemical properties of CPE membranes were explored. The high ionic conductivity (1.82 × 10−3 S cm−1 at 50 °C) and superior interfacial stability with the lithium anode was obtained. Furthermore, the rate performances and the cycling properties of CPE in LiFePO4 (LFP) batteries were extensively studied. The CPE-15% PPU film showed the excellent electrochemical stability of 84.3% capacity retention after 890 cycles at 0.5 C and 82.4% capacity retention after 500 cycles at 1.0 C at 50 °C. Especially, the CPE matched with high-voltage LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode delivered long-term stable cycling performances. The novel polymer electrolyte acquired could open up a new horizon to achieve high stable lithium metal batteries.

Development of a Novel Composite Polymer Electrolyte Membrane for Application as a Separator in a Dual Chamber Microbial Fuel Cell

Development of a Novel Composite Polymer Electrolyte Membrane for Application as a Separator in a Dual Chamber Microbial Fuel Cell

Composite polymer electrolyte based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) for solid-state batteries

Using solid-state electrolytes (SSEs) with excellent thermal and electrical stability to replace liquid electrolytes, and assembling solid-state lithium-ion batteries (SSLIBs) is considered the best solution to these safety issues. However, it is difficult for a single electrolyte to have the characteristics of high ionic conductivity, low interface resistance, and high stability of the counter electrode at the same time. In this work, the composite polymer electrolyte membrane (CPE) of inorganic Li1.3Al0.3Ti1.7(PO4)3 (LATP) and organic poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) polymer was successfully prepared by traditional casting method. The addition of LATP (10 wt %) ceramic powder makes CPE membrane (CPE-10) exhibit excellent electrochemical performance: the lithium-ion transference number and electrochemical window are as high as 0.60 and 4.94 V, respectively. Moreover, the CPE-10 showed excellent Li-metal stability, thereby enabling the Li–Li symmetric cells to stably run for over 300 h at 0.1 mA/cm2 with effective lithium dendrite inhibition. When paired with a high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, the Li/CPE-10/NCM622 cell exhibited excellent electrochemical performance: the highest specific discharge capacity of 152 mAh/g could be conducted at 0.2C after 50 cycles corresponding to 100% Coulombic efficiencies. The prepared CPE-10 demonstrates excellent electrochemical performance, providing an effective design strategy for SSLMBs.

All-Perfluorosulfonated-Ionomer Composite Membranes Containing Blow-Spun Fibers: Effect of a Thin Fiber Framework on Proton Conductivity and Mechanical Properties.

In this study, thin fiber composite polymer electrolyte membranes (PEMs) were prepared using short side-chain perfluorosulfonic acid (PFSA) ionomers, Aquivion, to create composite PEMs with improved proton conductivity and improved mechanical properties. PFSA thin fiber webs prepared by blow spinning and successive hot pressing were used as the porous substrate. Herein, PFSA ionomers were used for both the substrate and the matrix of the composite PEMs, and their structures, properties, and fuel cell performance were characterized. By adding the PFSA thin fiber webs to the matrix, the proton conductivity was enhanced and the mechanical properties were slightly improved. The prepared PFSA thin fiber composite PEM showed better FC performance than that of the pristine PFSA one for the high-temperature low-humidity condition in addition to the low-temperature high-humidity one. To the best of our knowledge, this is the first report on the all PFSA composite membranes containing a PFSA thin fiber framework.

Flexible Composite Electrolyte Membranes with Fast Ion Transport Channels for Solid-State Lithium Batteries.

Numerous endeavors have been dedicated to the development of composite polymer electrolyte (CPE) membranes for all-solid-state batteries (SSBs). However, insufficient ionic conductivity and mechanical properties still pose great challenges in practical applications. In this study, a flexible composite electrolyte membrane (FCPE) with fast ion transport channels was prepared using a phase conversion process combined with in situ polymerization. The polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) polymer matrix incorporated with lithium lanthanum zirconate (LLZTO) formed a 3D net-like structure, and the in situ polymerized polyvinyl ethylene carbonate (PVEC) enhanced the interface connection. This 3D network, with multiple rapid pathways for Li+ that effectively control Li+ flux, led to uniform lithium deposition. Moreover, the symmetrical lithium cells that used FCPE exhibited high stability after 1200 h of cycling at 0.1 mA cm-2. Specifically, all-solid-state lithium batteries coupled with LiFePO4 cathodes can stably cycle for over 100 cycles at room temperature with high Coulombic efficiencies. Furthermore, after 100 cycles, the infrared spectrum shows that the structure of FCPE remains stable. This work demonstrates a novel insight for designing a flexible composite electrolyte for highly safe SSBs.

Controlling the Potential of Affordable Quasi‐Solid Composite Gel Polymer Electrolytes for High‐Voltage Lithium‐Ion Batteries

AbstractThis study focuses on the development of a composite gel polymer electrolyte membrane (CGPEM) as a solution to address safety concerns arising from the reactivity of lithium metal and the formation of dendrites. The CGPEM integrates a solid polymer matrix, solid‐electrolyte LSiPS (Li10SiP2S12), with a plasticizer that countering the performance decline caused by sulfide solid electrolyte (SSE) interactions with the cathode. Poly ethylene oxide (PEO) emerges as a promising polymer matrix due to its flexibility, cost‐effectiveness, eco‐friendliness, solvability for Li‐salt, mechanical processing adaptability, adhesive strength, and ionic conductivity. Conductivity and processability of CGPEM were optimized through meticulous adjustment of liquid plasticizer concentration. The CGPEM′s chemical and electrochemical stability were systematically investigated using in‐situ electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRTs). A lithium metal battery is constructed against a high voltage cathode and newly developed CGPEM. Impressively, the cell exhibited outstanding performance, maintaining a discharge capacity of around 146.22 mAh/g after 200 cycles, retaining 86.38 % of its initial capacity. The formation of a LiF‐rich interface layer near the lithium surface, a vital element in curbing CGPE degradation and dendritic growth, resulted in enhanced overall cell performance.

Micro Area Interface Wetting Structure with Tailored Li+-Solvation and Fast Transport Properties in Composite Polymer Electrolytes for Enhanced Performance in Solid-State Lithium Batteries.

To satisfy the demand for high safety and energy density in energy storage devices, all-solid-state lithium metal batteries with solid polymer electrolytes (SPE) replacing traditional liquid electrolytes and separators have been proposed and are increasingly regarded as one of the most promising candidates as next-generation energy storage systems. In this study, poly(vinylidene fluoride)-hexafluoropropylene/lignosulfonic acid (PVDF-HFP/LSA) composite polymer electrolyte (CPE) membranes with a micro area interface wetting structure were successfully prepared by incorporating LSA into the PVDF-HFP polymer matrix. The enhanced interaction between the polar functional group in LSA and the C═O in N-methylpyrrolidone (NMP) hinders the evaporation of solvent NMP, thus creating a micro area wetting structure, which offers a flexible region for the chain segment movement and enlarging the area of the amorphous zone in PVDF-HFP. From the results of IR and Raman spectroscopy, it was found that the presence of LSA induced unique ion transport channels created by the massive aggregated ion pair (AGG) and contact ion pair (CIP) of ion cluster structures composed of Li+ and multiple TFSI- and, at the same time, effectively reduced the crystallinity of the polymer electrolyte, hence further contributing to the Li+ diffusion. As a result, at a rate of 2 C, the Li|CPE-15|LiFePO4 solid-state battery delivers an initial discharge-specific capacity of 134.9 mAh g-1 and maintains stability with a retention of 84% during 400 charge-discharge cycles while the Li|CPE-0|LiFePO4 battery fails after only a few cycles at the same rate.

Development of composite solid polymer electrolyte for solid-state lithium battery: Incorporating LLZTO in PVDF-HFP/LiTFSI

Solid-state batteries (SSBs) are regarded as favorable future technology as they promise to deliver high energy density and improved safety. However, despite extensive research efforts, the development of SSBs still fall short of expectations mainly because of suitable solid electrolyte which can provide high ionic conductivity as well as good flexibility to enhance interface contact between electrolyte and electrodes. In this work, we have prepared free-standing, flexible composite solid polymer electrolyte (CSPE) membranes by incorporating LLZTO ceramic particles in PVDF-HFP/LiTFSI based solid polymer electrolyte (SPE). Addition of 20 wt% LLZTO has shown to improve the electrochemical properties of the solid electrolyte such as ionic conductivity (8.2 × 10−4 S cm−1 at 60 °C), transference number, electrochemical stability and long-term interface stability with the lithium-metal also showed significant improvement. Furthermore, solid-state LiFePO4/SPE/Li and LiFePO4/CSPE/Li batteries were fabricated, and charge/discharge cycling was performed, where battery with SPE and CSPE exhibited discharge capacity of 119 mA h g−1 and 131 mA h g−1 respectively at 0.1C rate, 60 °C.

Development of Blend Nanofiber Composite Polymer Electrolyte Membranes with Dual Proton Conductive Mechanism and High Stability for Next-Generation Fuel Cells

Blend polymer nanofibers (BNF), consisting of sulfonated polyimide and polybenzimidazole blends doped with phytic acid, were fabricated and composed with Nafion to give BNF composite membranes for polymer electrolyte fuel cells. The BNF composite membrane possessed high mechanical and chemical stabilities and low gas permeability. In addition, the BNF composite membrane showed higher proton conductivity than the commercial Nafion NR211 membrane, not only at low temperatures but also at high temperatures above 100 °C and low relative humidity (ca. 10% RH). The proton conduction mechanism in the BNF composite membranes was examined and revealed that proton hopping conduction occurred besides the vehicle mechanism in the BNF composite membranes. The BNF composite membrane provided improved fuel cell performances compared to the cell using the conventional Nafion NR211 membrane at high humidity, low humidity, and high temperature/low humidity, suggesting the potential of BNF composite membranes for next-generation fuel cells.

Understanding the Influence of Li7La3Zr2O12 Nanofibers on Critical Current Density and Coulombic Efficiency in Composite Polymer Electrolytes.

Composite polymer electrolytes (CPEs) are attractive materials for solid-state lithium metal batteries, owing to their high ionic conductivity from ceramic ionic conductors and flexibility from polymer components. As with all lithium metal batteries, however, CPEs face the challenge of dendrite formation and propagation. Not only does this lower the critical current density (CCD) before cell shorting, but the uncontrolled growth of lithium deposits may limit Coulombic efficiency (CE) by creating dead lithium. Here, we present a fundamental study on how the ceramic components of CPEs influence these characteristics. CPE membranes based on poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO-LiTFSI) with Li7La3Zr2O12 (LLZO) nanofibers were fabricated with industrially relevant roll-to-roll manufacturing techniques. Galvanostatic cycling with lithium symmetric cells shows that the CCD can be tripled by including 50 wt % LLZO, but half-cell cycling reveals that this comes at the cost of CE. Varying the LLZO loading shows that even a small amount of LLZO drastically lowers the CE, from 88% at 0 wt % LLZO to 77% at just 2 wt % LLZO. Mesoscale modeling reveals that the increase in CCD cannot be explained by an increase in the macroscopic or microscopic stiffness of the electrolyte; only the microstructure of the LLZO nanofibers in the PEO-LiTFSI matrix slows dendrite growth by presenting physical barriers that the dendrites must push or grow around. This tortuous lithium growth mechanism around the LLZO is corroborated with mass spectrometry imaging. This work highlights important elements to consider in the design of CPEs for high-efficiency lithium metal batteries.

Investigation of structural and conductivity properties of poly(vinyl alcohol)‐based electrospun composite polymer blend electrolyte membranes for battery applications

AbstractSolid polymer electrolyte has attracted great interest for the next generation of electrochemical devices such as batteries, but the low ionic conductivity and poor stability has retarded their commercial acceptance for energy storage devices applications. To overcome these issues, strategies to develop composite polymer electrolytes (CPEs) are drawing interest. Nanocomposite solid polymer blend electrolyte membranes based on poly (vinyl alcohol) (PVA), poly (vinyl pyrrolidone) (PVP) of various compositions that contained potassium nitrate (KNO3) as a dopant salt, and Barium Titanate (BaTiO3) as a filler were prepared with various concentrations of filler using electrospinning technique. The structural and complex formations due to interaction of various groups of the prepared composite polymer electrolyte membranes were investigated using X‐ray diffraction (XRD) and Fourier transform infra‐red (FTIR) spectral analysis. The conductivity of the PVA‐PVP‐KNO3‐BaTiO3 polymer electrolyte systems was found to vary between 3.71×10‐9 and 1.99×10‐5 S cm‐1 at 298 K with the increase in filler concentration. The maximum room temperature ionic conductivity (1.99×10‐5 S cm‐1) has been obtained for 9 wt% BaTiO3 doped polymer electrolyte system. The addition of filler also enhanced the thermal stability of the electrolyte. The temperature dependence ionic conductivity of the prepared complexed polymer electrolyte systems appears to obey Arrhenius behaviour.

Effects of a high-performance, solution-cast composite electrolyte on the host electrospun polymer membrane for solid-state lithium metal batteries

Dispersed nano-silica fillers in poly (ethylene oxide) were solution cast on a host electrospun polyacrylonitrile membrane. The host electrospun polyacrylonitrile membrane enhanced the overall elasticity and ionic conductivity of the composite polymer electrolyte membrane for solid-state lithium metal batteries. Three different concentrations of silica fillers were added (1%, 3%, and 5%) called CSE 1, CSE 3, and CSE 5. The composite electrolyte membranes were compared with the 0% concentration of silica fillers and named SE. Among them, the CSE 3 membrane outperformed and delivered an ionic conductivity of 7.1 × 10 −4 S cm−1, lithium-ion transference number of 0.62, and the ultimate tensile strength of 27.3 MPa with 110.9% strain, revealing the elasticity of the CSE 3 membrane. The thermal stability of up to 354 °C and the wide range of electrochemical stabilities of up to 5.1 V were achieved. The symmetric cell Li|CSE 3|Li showed satisfactory long operation of lithium plating/stripping for 500 h without a significant voltage drop or short circuit. Furthermore, the electrode surface showed the homogeneous deposition of lithium on the plated electrode and a relatively smooth surface on the stripped electrode. The LCO|CSE 3|Li exhibits better rate capability and excellent cycling performance with 91.1% capacity retention and maintains 131.9 mAh g−1at 0.5C after 200 cycles.

Physical and electrical property studies on sodium (Na+) – Ion conducting Nano–Composite Polymer Electrolyte membranes

Present work reports that Polymer Electrolyte Membranes: [97PEO: 3NaCOOCH3] dispersed with ceramic filler SiO2 have been synthesized using the hot-press casting technique. Ion transport properties have been evaluated in terms of the essential ionic conductivity (σ) and total ionic (tion) / cationic (t+) transference numbers using different ac/dc techniques to evaluate its usefulness in all-solid-state battery applications. Structural/thermal properties have been characterized using X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) techniques. The thermal laminated pouch cell has been fabricated and tested by sandwiching the best optimized NCPE film between MnO2 cathode and Graphite anode. Cyclic Voltammetry study of NCPE film exhibits good electrochemical behaviour and is more suitable for battery fabrication.

Proton conductivity and dimensional stability of proton exchange membrane: A dilemma solved by chitosan aerogel framework

Increasing proton conductivity of polymer electrolyte membrane (PEM) by introducing more number of proton transfer species, especially sulfonated groups always lead to a decrease in mechanical/dimensional stability. The present work proposes the solution to overcome this dilemma by applying chitosan (CS) interconnected with sulfonated poly(ether ether ketone) (SPEEK) to provide not only the 3D framework for dimensional stability but also the sulfonated groups and amino groups play the role in proton transfer. By simply crosslinking CS with succinic acid (SA) followed by lyophilizing, the stable 3D-framework (CS-x)-SA can be obtained. This (CS-x)-SA framework allows the incorporation of SPEEK during membrane formation results in semi-interpenetrating (CS-x)-SA-SPEEK. The (CS-0.25)-SA-SPEEK membrane obtained performs mechanical stability in terms of tensile strength for 12%, with a proton conductivity increment for 34% as compared to SPEEK. The present work demonstrates an approach to achieve the 3D interconnected composite PEM to achieve the improvement in proton transfer efficiency and mechanical strength as well as dimensional stability.

Performance Enhancement of Poly (Vinyl Alcohol) Composite Polymer Electrolyte for Li-Ion Battery Through Salt Immersion Process

Poly (vinyl alcohol) (PVA) composite membrane as separator-cum-electrolyte for li-ion battery was prepared via solution casting method. Hydrophilicity of PVA helped to substitute flammable, toxic solvents with deionised water. Lithium bis(oxalato) borate (LiBOB) electrolyte salt was incorporated in the membrane to form flexible self-standing membrane of composite polymer electrolyte (CPE). To further enhance the ionic conductivity, CPE membrane was immersed in 1M LiBOB salt dissolved in deionised water. Neat PVA membrane would have been dissolved instantly in any solution involving water; introduction of LiBOB electrolyte salt deprived the hydrogen bond which transform it into an insoluble CPE membrane. EIS measurement showed that salt immersion boosted the CPE membrane ionic conductivity by four orders of magnitude, from 4.77×10–7 S/cm to 1.93×10–3 S/cm at room temperature.

Ultra‐Thin Single‐Particle‐Layer Sodium Beta‐Alumina‐Based Composite Polymer Electrolyte Membrane for Sodium‐Metal Batteries

AbstractInorganic/organic composite polymer electrolytes (CPEs) with good flexibility and electrode contact have been pursued for solid−state sodium‐metal batteries. However, the application of CPEs for high energy density solid−state sodium‐metal batteries is still limited by the low Na+ conductivity, large thickness, and low ion transference number. Herein, an ultra‐thin single‐particle‐layer (UTSPL) composite polymer electrolyte membrane with a thickness of ≈20 µm straddled by a sodium beta−alumina ceramic electrolyte (SBACE) is presented. A ceramic Na+‐ion electrolyte that bridges or percolates across an ultra‐thin and flexible polymer membrane provides: 1) the strength and flexibility from the polymer membrane, 2) excellent electrolyte/electrode interfacial contact, and 3) a percolation path for Na+‐ion transfer. Owing to this novel design, the obtained UTSPL‐35SBACE membrane exhibits a high Na+‐ion conductivity of 0.19 mS cm−1 and a transference number of 0.91 at room temperature, contributing to long−term cycling stability of symmetric sodium cells with a small overpotential. The assembled quasi‐solid‐state cell with the as−prepared UTSPL‐35SBACE membrane displays superior cycling performance with a discharge capacity of 105 mAh g−1 at 0.5 °C rate after 100 cycles and excellent rate performance (82 mAh g−1 at 5 °C rate) at room temperature with the potassium manganese hexacyanoferrate (KMHCF)@CNTs/CNFs cathode, where KMHCF refers to potassium manganese hexacyanoferrate.

In-situ construction of high-temperature-resistant 3D composite polymer electrolyte membranes towards high-performance all-solid-state lithium metal batteries

Enabling solid polymer electrolytes (SPEs) with enhanced electrochemical properties and high-temperature-resistance is highly desirable for developing high-performance lithium metal batteries (LMBs) with high-safety. In this contribution, single-ion conducting polymers and SiO2 particles, as advanced fillers, are in-situ cross-linked in poly(ethylene oxide) (PEO) based SPEs to form three-dimensional (3D) cross-linking inorganic/organic composite SPEs. Benefiting from the hydrogen bond interaction between the additives and PEO chains, the crystallinity of PEO polymers in the resultant SPEs is greatly decreased, giving rise to high conductivity (3.3 × 10−4 S cm−1) and lithium ion transference number (0.60) at 60 °C. The Li/Li symmetrical cells with the composite SPEs can be run stably more than 400 h at 60 °C and 550 h at 120 °C under 0.1 mA cm−2, respectively. Remarkably, the favorable thermal stability of composite SPEs leads to safer solid-state LMBs operating at the high temperature up to 120 °C, where it reaches an outstanding rate performance up to 4C and displays impressive cycling performances with 89.9% retention over 110 cycles at 1C. This work offers tremendous potential in the practical application of dendrite-free and high-performance LMBs.

Flexible ion-conducting membranes with 3D continuous nanohybrid networks for high-performance solid-state metallic lithium batteries

Polyethylene oxide (PEO)-based electrolytes are considered as one of the most promising solid-state electrolytes for next-generation lithium batteries with high safety and energy density; however, the drawbacks such as insufficient ion conductance, mechanical strength and electrochemical stability hinder their applications in metallic lithium batteries. To enhance their overall properties, flexible and thin composite polymer electrolyte (CPE) membranes with 3D continuous aramid nanofiber (ANF)–Li1.4Al0.4Ti1.6(PO4)3 (LATP) nanoparticle hybrid frameworks are facilely prepared by filling PEO–LiTFSI in the 3D nanohybrid scaffolds via a solution infusion way. The construction of the 3D continuous nanohybrid networks can effectively inhibit the PEO crystallization, facilitate the lithium salt dissociation and meanwhile increase the fast-ion transport in the continuous LATP electrolyte phase, and thus greatly improving the ionic conductivity (∼3 times that of the pristine one). With the integration of the 3D continuity and flexibility of the 3D ANF networks and the thermostability of the LATP phase, the CPE membranes also show a wider electrochemical window (∼5.0 V vs. 4.3 V), higher tensile strength (∼4–10 times that of the pristine one) and thermostability, and better lithium dendrite resistance capability. Furthermore, the CPE-based LiFePO4/Li cells exhibit superior cycling stability (133 mAh/g after 100 cycles at 0.3 C) and rate performance (100 mAh/g at 1 C) than the pristine electrolyte-based cell (79 and 29 mAh/g, respectively). This work offers an important CPE design criteria to achieve comprehensively-upgraded solid-state electrolytes for safe and high-energy metal battery applications.