Poly Vinylidene Fluoride-hexafluoropropylene Research Articles

Boosting α to β transformation of PVDF/HFP through natural hydroxyapatite derived from animal bones for eco-friendly energy harvesters

Appropriate additives can significantly enhance the piezoelectric properties of piezoelectric materials. In particular, eco-friendly ceramics made from natural sources, such as animal bones, can be produced in a low-energy process and contribute to a lower carbon footprint. In this study, hydroxyapatite (HA) particles were produced by synthesizing natural bovine bone by means of mechanosynthesis route and employed as nucleating agents to enhance self-polarization of piezoelectric polymers. With a simple and eco-friendly manufacturing process, the HA is embedded in polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). Scanning electron microscope (SEM), and Fourier transform infrared spectroscopy analysis (FTIR) were used to examine the distribution uniformity of hydroxyapatite particles and investigate the effect of particles on the crystallinity of polymer composite. In addition, electrical and piezoelectric measurements were conducted to illustrate the effect of HA contents on the performance of the realized films. By increasing the contents of HP, the relative fraction of β-phase increased sharply for 20 wt % HA/PVDF-HFP film, leading to high piezoelectric performance. The films made with 20 wt%HA/PVDF-HFP had a maximum output voltage of 2 V and a maximum output power of 1.75 μW and were 0.8 V and 0.25 μW for the pristine PVDF-HFP film illustrating the significant role of HA for α-to β-phase transformation. Furthermore, adding 20 wt % hydroxyapatite (HA) to PVDF-HFP enhanced the dielectric properties. Under walking, the realized biocomposite was able to harvest body energy into useable electricity up to 4 V. In this study, bio-derived materials are shown to have great potential for affordable eco-friendly nanogenerators that produce electricity from body movements.

Natural sucrose-assisted controllable porous PVDF-HFP films for self-powered tactile sensors with higher sensitivity

Incorporating porous structures into flexible piezoelectric materials has proven to be an effective strategy to enhance the output performance, but the fabrication processes are often intricate or environmentally harmful. In this study, natural sucrose with substantial hydroxyl groups was firstly introduced into polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a phase formation inducer, and subsequently removed by the dissolution of water as a pore formation agent, yielding a regular porous structure. Furthermore, porosity of the PVDF-HFP film could be simply modulated by adjusting the mass ratio of sucrose to PVDF-HFP. At low porosity levels, the dielectric constant of PVDF-HFP decreased with the increase of porosity, reaching the minimum at the critical threshold porosity of 38.8 %. Owing to the increased β-phase content and the decreased dielectric constant, the sensitivity of the porous PVDF-HFP film based piezoelectric sensor was tripled to 117 mV/N, which held promise for detecting tactile and slip signals in mechanical arms.

Durable hybrid metamaterial with hierarchically porous structure for efficient passive daytime radiative cooling

Passive daytime radiative cooling, which strongly emits heat while minimally absorbing sunlight, constitutes a promising strategy to address the energy density mismatch between solar irradiance and the low infrared radiation flux from material surfaces. However, nanoscale-precision manufacturing and the need for additional metal backing often result in low efficiency and limited applicability. Here, we present a durable hybrid metamaterial (DHM) comprising a randomly distributed inorganic dielectric particle–polymer composite with a hierarchically porous structure created via a simple phase separation method. Despite the absence of a metal backing, the DHM exhibits a broadband, high mid-infrared emissivity of 98.2 % and a high solar reflectivity of 98.0 %, enabling it to strongly radiate heat and scatter sunlight. Outdoor testing demonstrates that the DHM achieves an average cooling temperature of 9.0 °C under an average solar irradiance of 853.4 W·m−2, comparable to recently reported radiative coolers. The high electronegativity of C–F bonds in polyvinylidene fluoride–hexafluoropropylene (PVDF–HFP) and the high thermal and chemical stability of zirconium dioxide microparticles (ZrO2 MPs) endow the DHM with excellent environment durability. Moreover, the DHM provides effective and passive protection for ice and snow under sunlight exposure. Considering its outstanding cooling performance, environmental stability, and scalability, the DHM holds great promise for widespread applications in building and vehicle cooling, as well as glacier preservation efforts.

Evaluation of the dielectric, and piezoelectric properties and optimizing the figure of merit of the 0–3 KNN-0.8ZnO/PVDF-HFP piezoelectric composite by the Taguchi method

Piezoelectric ceramic and composite materials are attractive for various applications, but they can be challenging to process. In this research, KNN-0.8ZnO with high density (ρth=95 %), favorable microstructure, and suitable dielectric and piezoelectric properties (K=875, d33=125 pC/N, tanδ=0.01) was first synthesized. Additionally, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, known for its advantageous piezoelectric and mechanical properties, was selected as the polymer phase. subsequently, the KNN-0.8ZnO/xPVDF-HFP composite samples with a 0–3 connectivity pattern were made with the cold sintering method. The Taguchi design of experiment (DOE) was employed to determine the optimal condition for maximizing the figure of merit (FOM). Furthermore, an analysis of variance (ANOVA) was carried out to evaluate the significance of individual factors on each measured property. Phase identification was performed using X-ray diffraction (XRD) analysis, while the microstructure was examined using scanning electron microscopy. Among the different composite samples fabricated using the L9 orthogonal array (OA) of the Taguchi method, the KNN-0.8ZnO/20PVDF-HFP composite containing 20 wt% polymer phase, that was cold-sintered under a pressure of 400 MPa at 200 ͦC for 2 h, exhibited the highest FOM value of 1.945Pm2/N. This result aligns with the optimal conditions predeicated by the Taguchi DOE method. The compressive strength of the KNN-0.8ZnO/20PVDF-HFP composite was assessed through a compression test, yielding a value of 207 MPa, while the elastic modulus was approximately 3 GPa. The findings of this study demonstrate that the cold sintering method is an effective approach for producing dense piezoelectric composites with favorable electrical and mechanical properties, along with a high FOM for energy harvesting applications.

Construction of flexible asymmetric composite polymer electrolytes for high-voltage lithium metal batteries with superior performance

The primary obstacle hindering the application of composite solid electrolytes lies in the varying demands posed by the Li metal anode and the cathode, which needs to be capable of suppressing dendrite growth and resisting high voltage simultaneously. In this work, a new asymmetric composite solid-state electrolyte prepared via electrospinning and in-situ polymerization is proposed to address these shortcomings. In this bilayer architecture, polyacrylonitrile (PAN) layer of high-voltage tolerance, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) layer of robust mechanical strength and good compatibility towards Li-anode are constructed, and metal-organic-frameworks (MOFs) are pre-embedded within both layers. The unique design provides a wide electrochemical stability window meanwhile ensures uniform lithium deposition. Remarkably, it exhibits a superior lithium utilization of 41 mAh cm−2 using a lean polymer electrolyte precursor and a high critical current density of 2.2 mA cm−2 with a thickness of 40 μm. Beneficial from the formation of a self-adjustable gradient solid electrolyte interphase in the Li/PVDF-HFP interface, the asymmetric electrolyte endows Li||Li and Li||NCM811 cells with excellent cycling stability. Moreover, the solid-state pouch cell exhibits reliable operation under extreme conditions. This work provides inspiration for the design and fabrication of composite solid electrolytes for next-generation high-voltage Li metal batteries.

Piezoelectric properties and microstructural changes of smart asphalt-based composites containing electroactive polymer and carbon black

The requirements for smart asphalt pavement with piezoelectric properties are becoming necessary as the demand for clean energy and intelligent transportation are increased. To develop asphalt-based composite with electroactive performance for pavement electricity generation and to recycle battery waste, carbon black was first added to polyvinylidene fluoride-hexafluoropropylene to prepare electroactive polymer modifier (EPM) with high content of electroactive crystalline phases. Then carbon black and EPM were added into asphalt to prepare asphalt-based composites containing electroactive polymer (ACEP). The Output voltage, environmental scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and basic performance tests were conducted to study the piezoelectric properties, microstructural changes, electroactivity generation mechanism and basic performance of ACEP. The result shows that 5 % EPM has good dispersion, and stable crystallization rate of about 26 % and considerable electroactive crystalline phase content in asphalt, but more holes and defects inside ACEP appears when EPM is excessive. Also, the addition of EPM can slightly improve low-temperature property and thermal stability of ACEP. This is because the F element in EPM can interact with the polar groups in the gum and asphaltene. The 5 % ACEP sample with a thickness of 5 mm can output a voltage of about 260 mV. The penetration, ductility and softening point of 5 % ACEP were 55.2 dmm, 285 mm and 62.3°C, respectively. It is found that ACEP has a good combination of piezoelectric and basic pavement properties and can be used to build smart asphalt pavement with piezoelectric properties. This also provides a way to recycle battery waste.

Biomimetic Ag-modified core-shell nanofibrous membrane with enhanced solar absorption and water replenishment for efficient clean water production and antibacterial activity

Microorganism contamination of evaporators can deteriorate their performance during solar-driven water evaporation. Herein, we developed a biomimetic core-shell nanofibrous membrane with enhanced solar absorption, water replenishment, and antimicrobial properties via modification of silver nanoparticles (Ag-NPs). By mimicking the core-shell structure of natural pine needles, (1) the core of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) nanofiber, like the xylem of pine needles, can act as a support skeleton for dimensional stability; and (2) the shell of Ag-NPs-modified copper oxide (CuO) crystals (Ag@CuO), like the mesophyll of pine needles (photosynthesis for pine growth), can perform the photothermal and antimicrobial properties. The Ag@CuO nanofibrous membrane achieved increased solar absorption from 92.44 % to 95.88 % and decreased water contact angle from 36.1° to 0° after the incorporation of Ag-NPs. Furthermore, the Ag@CuO nanofibrous membrane exhibited stable evaporation rates of 1.31 kg⋅m−2⋅h−1 for 3.5 wt% saline water and 1.27 kg⋅m−2⋅h−1 for actual dye wastewater. Moreover, the nanofibrous membrane possessed excellent flexibility and robust adhesion of Ag-NPs due to the strong interfacial bonding induced by polydopamine. In addition, inhibition rates above 99.97 % against Staphylococcus aureus and Escherichia coli demonstrated the outstanding antimicrobial properties of the Ag@CuO membrane. In conclusion, the high evaporation performance, excellent flexibility, and outstanding antimicrobial properties enable the Ag@CuO nanofibrous membrane to be a good option for sustainable clean water production by treating evaporation media containing microorganisms.

Preparation and sensing performance of wet-spun fabric triboelectric nanogenerator for energy harvesting

Flexible, wearable triboelectric nanogenerators (TENGs) monitoring human movement and health signals have received more attention recently. In particular, developing a flexible TENG combining stress, strain, electrical output performance and durability becomes the current research focus. Herein, a highly stretchable, self-powered coaxial yarn TENGs were manufactured using a low-cost, efficient continuous wet-spinning method. Carbon nanotube/conductive thermoplastic polyurethane (MWCNT/CTPU) and polyvinylidene fluoride-hexafluoropropylene were utilized for the coaxial fibers conductive layers and dielectric layers, respectively. Fibers were continuously collected over a length of 10 m. Excellent electrical output with an open-circuit voltage (Voc) of 11.4 V, short-circuit current (Isc) of 114.8 nA, and short-circuit transfer charge (Qsc) of 6.1 nC was achieved. In addition, fabric TENGs with different two and three dimensional structures were further prepared by the developed coaxial fibers. The corresponding electrical output properties and practical performance were discussed. Results showed that the four-layer three-dimensional angle interlocking structure exhibited the optimal performance with an open-circuit voltage (Voc) of 38.4 V, short-circuit current (Isc) of 451.5 nA, and short-circuit transfer charge (Qsc) of 23.1 nC.

Highly Conductive and Stable Composite Polymer Electrolyte with Boron Nitride Nanotubes for All-Solid-State Lithium Metal Batteries.

All-solid-state lithium metal batteries (ASSLMBs) have emerged as the most promising next-generation energy storage devices. However, the unsatisfactory ionic conductivity of solid electrolytes at room temperature has impeded the advancement of solid-state batteries. In this work, a multifunctional composite solid electrolyte (CSE) is developed by incorporating boron nitride nanotubes (BNNTs) into polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). BNNTs, with a high aspect ratio, trigger the dissociation of Li salts, thus generating a greater population of mobile Li+, and establishing long-distance Li+ transport pathways. PVDF-HFP/BNNT exhibits a high ionic conductivity of 8.0×10-4S cm-1 at room temperature and a Li+ transference number of 0.60. Moreover, a Li//Li symmetric cell based on PVDF-HFP/BNNT demonstrates robust cyclic performance for 3400h at a current density of 0.2mA cm-2. The ASSLMB formed from the assembly of PVDF-HFP/BNNT with LiFePO4 and Li exhibits a capacity retention of 93.2% after 850 cycles at 0.5C and 25°C. The high-voltage all-solid-state LiCoO2/Li cell based on PVDF-HFP/BNNT also exhibits excellent cyclic performance, maintaining a capacity retention of 96.4% after 400 cycles at 1C and 25°C. Furthermore, the introduction of BNNTs is shown to enhance the thermal conductivity and flame retardancy of the CSE.

Microfiber/Nanofiber/Attapulgite Multilayer Separator with a Pore-Size Gradient for High-Performance and Safe Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) have an extremely diverse application nowadays as an environmentally friendly and renewable new energy storage technology. The porous structure of the separator, one essential component of LIBs, provides an ion transport channel for the migration of ions and directly affects the overall performance of the battery. In this work, we fabricated a composite separator (GOP-PH-ATP) via simply laminating an electrospun polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) nanofibrous membrane coated with attapulgite (ATP) nanoparticles onto a PP nonwoven microfibrous fabric, which exhibits a unique porous structure with a pore-size gradient along the thickness direction that ranges from tens of microns to hundreds of nanometers. As a result, besides the enhanced thermal stability given by the chosen materials, the GOP-PH-ATP separator was endowed with a superhigh porosity of ~95%, strong affinity with electrolyte, and great electrolyte uptake of ~760%, thus effectively enabling an ionic conductivity of 2.38 mS cm-1 and a lithium-ion transference number of 0.62. Furthermore, the cell with the GOP-PH-ATP separator shows an excellent cycling performance with a capacity retention of 91.2% after 150 cycles at 1 C, suggesting that the composite separator with a pore-size gradient structure has great potential to be applied in LIBs.

Preparation of Al@FTCS/P(VDF-HFP) Composite Energetic Materials and Their Reaction Properties.

Strengthening the interfacial contact between the reactive components effectively boosts the energy release of energetic materials. In this study, we aimed to create a close-knit interfacial contact condition between aluminum nanoparticles (Al NPs) and Polyvinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) through hydrolytic adsorption and assembling 1H, 1H, 2H, 2H-Perfluorododecyltrichlorosilane (FTCS) on the surface of Al NPs. Leveraging hydrogen bonding between -CF and -CH and the interaction between C-F⋯F-C groups, the adsorbed FTCS directly leads to the growth of the P(VDF-HFP) coating layer around the treated Al NPs, yielding Al@FTCS/P(VDF-HFP) energetic composites. In comparison with the ultrasonically processed Al/P(VDF-HFP) mixture, thermal analysis reveals that Al@FTCS/P(VDF-HFP) exhibits a 57 °C lower reaction onset temperature and a 1646 J/g increase in heat release. Associated combustion tests demonstrate a 52% shorter ignition delay, 62% shorter combustion time, and a 288% faster pressurization rate. These improvements in energetic characteristics stem from the reactivity activation of FTCS towards Al NPs by the etching effect to the surface Al2O3. Moreover, enhanced interfacial contact facilitated by the FTCS-directed growth of P(VDF-HFP) around Al NPs further accelerates the whole reaction process.

Localized high concentration polymer electrolyte enabling room temperature solid-state lithium metal batteries with stable LiF-rich interphases

Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) based polymer electrolyte shows mechanical flexibility, soft and intimidate physical contact and good electrochemical stability, however, low ionic conductivity at room temperature and unstable interphases against Li metal hinder its application. In this article, we propose a universal strategy to prepare localized high concentration polymer electrolytes (LHCPE) in which high concentration lithium salt (LiTFSI) dissolved in tiny residual solvent (DMF) and the PVDF-HFP serves as solid dilution. The LHCPE regulates the solvation structure of lithium ions with anions instead of DMF solvent, allowing more anions to coordinate with Li+ and forming amount contact ion pairs (CIPs) and aggregates (AGGs). As a result, high ionic conductivity (5.9 × 10−4 S cm−1) and low activation energy (0.10 eV) achieved. The LHCPE also induces the decomposition of anions-derived LiF-rich interphases, that is ionic conducive and mechanical robust, thereby greatly improving the charge transfer kinetics and stability towards Li metal anodes. Consequently, at 0.5 mA cm−2 and 0.25 mAh cm−2, stable and long-term cycling over 2000 h obtained under room temperature in Li//Li symmetric cells achieved. The full solid-state LFP//LHCPE//Li cells further exhibit excellent capacity retention of 82.83 % even after 1200 cycles at room temperature and a high rate of 8 C (1C=170 mA·g−1). Our work shed light on the design of high-performance polymer-based composite electrolytes by manipulating the Li solvation structure.

A novel interferometry-based method to study the anisotropy and kinetics of liquid to solid transition in polymer

We propose and demonstrate a first Twin -interferometry based optical approach for studying and exploring anisotropy and directional dependent crystallization kinetic of curing polymers under isothermal condition. A commercial polymeric solution of polyvinylidene fluoride hexa-fluoropropylene (PVDF-HFP) with five different concentrations were prepared and utilised for this study. A Twin-interferometer (TIM) is designed to record the rate of shift in Michelson’s fringes caused by rate of change of optical path length of a transparent polymeric solution in two orthogonal directions during curing. Pair of interferogram referred as Twin- interferogram (TIG) is recorded for the sample of all concentration during its liquid to solid transition. An extraction approach for various crystallization parameters such as anisotropy, crystallization half-life time, constants governing the rate and dimensionality of crystallization, and their variation along distinct direction from TIM is demonstrated. The results provided by TIM are verified by a method of anisotropy annihilation and other experimental techniques includes Scanning electron microscopic (SEM), Polarising optical microscopic (POM) and Dielectric spectroscopic studies.

Piezo-enhanced photocatalysis of MoS2/Bi4O5Br2/PVDF-HFP film for wastewater purification

To date, the piezoelectric field has been demonstrated as a promising approach to inhibit the recombination of photogenerated carrier in photocatalyst applications. Herein we propose a MoS2/Bi4O5Br2/PVDF-HFP piezo-photocatalytic film in the organic pollutants remediation. MoS2/Bi4O5Br2 as the photocatalytic material is incorporated to poly (vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) as the supporting layer via a simple phase transition method. The polarised electric field generated on PVDF-HFP and MoS2/Bi4O5Br2 under aeration synergised with the built-in electric field formed between MoS2/Bi4O5Br2 Z-scheme heterojunction to promote the interfacial charge transfer. The degradation rates of rhodamine B (RhB) and tetracycline hydrochloride (TC) under aeration and visible light irradiation in 60 min reached 98.9% and 92.2%, respectively. Meanwhile, density functional theory calculations (DFT) further demonstrated the effective charge separation and transfer induced by the Z-scheme charge transfer mechanism constructed by MoS2 composite with Bi4O5Br2, as well as the synergistic effect of the double electric field in favour of suppressing carrier recombination. This work provides an interesting solution for effectively combining piezoelectric catalysis with photocatalysis.

Polymer solid electrolytes with ultra-stable cycles and high-capacity retention for all-solid-state Li-metal battery

Polymer electrolytes have become widely popular on account of their low expenses, reduced weight, simple processing, and excellent safety features. However, polymer electrolytes have yet to find use in commercial batteries because of their limited mechanical durability and poor ionic conductivity. In this paper, an ultra-stable cycles and interfaces blending polymer electrolyte (BPE) suitable for all solid-state Li metal batteries was prepared by blending three polymers: polymethyl methacrylate (PMMA), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), and polyethylene oxide (PEO). Microstructure characterization showed numerous amorphous areas with strong interfacial strength of the BPE. The BPE3 exhibited a maximum of 15.65 MPa in tensile strength. BPE2 have excellent electrochemical performance, such as wide electrochemical windows (up to 4.7 V vs Li/Li+), high lithium ion transference numbers (up to 0.75), high ion conductivity (up to 1.87 × 10-4 S cm−1 at 60 °C), and excellent interface stability. By assembling all state-solid LiFePO4/BPE2/Li batteries for electrochemical testing, BPE2 exhibit high electrochemical characteristics. BPE2 discharge specific capacity is as high as 154.7 mAh g−1 at 1C. The BPE2 underwent 200 cycles at 0.5C and 400 cycles at 1C, with capacity retention rates of 95.7 % and 96.6 %, respectively. BPE is a promising electrolyte candidate for flexible lithium metal batteries.

Tailoring porous structure in non-ionic polymer membranes using multiple templates for low-cost iron-lead single-flow batteries

Porous ion-selective membranes are promising alternatives for the expensive perfluorosulfonic acid membranes in redox flow batteries. In this work, novel non-ionic porous polyvinylidene fluoride-hexafluoro propylene membranes are designed for iron-lead single-flow batteries. The membranes are prepared using a multiple template approach, involving simultaneously using polyethylene glycol and dibutyl phthalate (DBP) as pore-forming templates. Their porous structure is finely tuned by adjusting the ratio of the two templates. As a result, dual-porous membranes bearing both macro and micropores are obtained. The H3520 membrane with modified porous structure attains a high proton conductivity of 43.5 mS·cm-1 and a relatively low ferric ion diffusion constant (8.61 × 10-8 cm2·min-1) and demonstrates the best balance between these performance-determining parameters (selectivity 5.04 × 105 S·min·cm-3, higher than that of the N115 membrane). Besides, performance tests of the iron-lead single-flow single cells equipped with the dual-porous membranes show a high energy efficiency, exceeding 87.2% at its rated current density, and outstanding cycling stability over 200 charge-discharge cycles. Altogether, the mixed template method presents a promising strategy to prepare high-performance and low-cost non-ionic membranes for redox flow batteries.

Constructing an All Solid-state Flexible Lithium-Manganese Battery with High Performance

Due to a lack of portable flexible power supply, flexible electronic products can still not be applied in a large scale, particularly in the high energy density devices. To resolve this issue, flexible solid-state lithium batteries with a high safety, excellent mechanical property, and high energy densit，is proposed. In this paper, a flexible solid-state lithium-manganese battery is developed, which is assembled with a lithium cloth composite anode, a composite solid-state electrolyte poly (vinylidene fluoride)-hexafluoropropylene (PVDF-HFP)/Li6.4La3Zr1.4Ta0.6O12 (LLZTO), and a composite cathode (Fe ion-doped MnO2-carbon cloth). To improve the conductivity and stability of cathode, a mixture of conductive carbon black (Super P) and sodium alginate (SA) is employed. To ensure the high capacity and low price, the MnO2-based cathode is used.The obtained solid state batteries can deliver an initial capacity of 275.9 mAh g−1 at a current density of 1 C and a capacity retention of 57.9% (159.7 mAh g−1) after 1000 cycles. Also the produced flexible punch cell can light up the light-emitting diode(LED), and its capacity is 0.58 mAh cm−2 after 100 cycles at current density of 0.2 C.

High performance solid state lithium batteries with a continuous homogeneous Li+ transmission channels

Solid state lithium batteries have been encountering a bottle neck of high solid-solid interface resistance of the membrane/electrode assembly, which is one industrial pain point. Herein, the composite solid electrolyte materials were designed and prepared to act as the double functions of solid state electrolyte membrane and the electrode binder for constructing a continuous homogeneous Li+ transmission channels with high compatibility and ionic conductivity. Firstly, dopamine was oxidized and self-polymerized on the surface of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) to form a polydopamine (PDA) active layer, and the zwitterionic betaine sulfonate (SB) was chemically grafted onto the PDA active layer by Michael addition reaction. Secondly, the composite solid electrolyte materials were prepared by mixing the resultant SB-modified PVDF-HFP was mixed with different contents (0 %, 10 %, 20 %, 30 %) of Li6.75La3Zr1.75Ta0.25O12 (LLZTO) and 20 % bis(trifluoromethane) sulphonyl lithium (LiTFSI). Finally, a series of composite solid electrolyte membranes were prepared by scraping method and labeled as 0%LLZTO/SB-PVDF-HFP/LiTFSI, 10%LLZTO/SB-PVDF-HFP/LiTFSI, 20 %LLZTO/SB-PVDF-HFP/LiTFSI, 30%LLZTO/SB-PVDF-HFP/LiTFSI, respectively. As expected, the cell with optimal 20 %LLZTO/SB-PVDF-HFP/LiTFSI as the solid electrolyte membrane and the electrode binder delivered the reversible capacity of 135.2 mAh/g at 1.0C and maintained high capacity retention of 94.8 % for 200 cycles. The construction of the continuous and homogeneous ion transmission channels should be responsible for high Li-storage performances by improving the interface compatibility of the membrane/electrode assembly and promoting the Li+ transmission.

Multiscale Polyvinylidene Fluoride/Magnesium–Aluminum Layered Double Hydroxide Gel Electrolytes for Lithium Batteries

A multiscale of porous polyvinylidene fluoride–hexafluoropropylene copolymer/magnesium–aluminum layered double hydroxides (MgAl‐LDHs) composite gel polymer electrolyte is prepared by phase separation method. It is discovered that the ionic conductivity of the electrolyte reaches a maximum value of 1.36 × 10−3 S cm−1, the lithium ions’ mobility is 0.66, and the chemical performance is steady within the 4.85 V window along with the concentration of MgAl‐LDHs up to 0.4 wt% at room temperature. The density functional theory calculations show that the adsorption energy of Li+ with MgAl‐LDH is −3.59 eV and the diffusion potential barrier is 0.37 eV, which is favorable for the dissociation and transport of Li+. Moreover, the anode's initial discharge capacity at 0.1 C achieves 144 mAh g−1, keeping 84.7% of the theoretical capacity of 170 mAh g−1, and the capacity retention and the columbic efficiency maintain 92.4% and 95.7% after 100 cycles at 0.2 C, respectively, through assembling into a Li/PVP–MgAl/LiFePO4 battery.

Constructing Enhanced Composite Solid-State Electrolytes with Sb/Nb Co-Doped LLZO and PVDF-HFP

Composite solid-state electrolytes are viewed as promising materials for solid-state lithium-ion batteries due to their combined advantages of inorganic solid-state electrolytes and solid-state polymer electrolytes. In this study, the solid electrolytes Li6.7−xLa3Zr1.7−xSb0.3NbxO12 (LLZSNO) with Sb and Nb co-doping were prepared by a high-temperature solid-phase method. Results indicate that Sb/Nb co-doping causes lattice deformation in LLZO and increases the lithium vacancy concentration and conductivity of LLZO. Then, with the co-doped LLZSNO as an inorganic filler, a composite solid electrolyte of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was prepared with a casting method. The obtained composite solid electrolyte exhibits a high ionic conductivity of 1.76 × 10−4 S/cm at room temperature, a wide electrochemical stable window of 5.2 V, and a lithium-ion transfer number of 0.32. The Li|LiFePO4 coin battery with the composite solid electrolyte shows a high specific capacity of 161.2 mAh/g and a Coulombic efficiency close to 100% at 1 C. In addition, the symmetrical lithium battery Li|Li with the composite electrolyte could cycle stably for about 1500 h without failure at room temperature.