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Polyethylene oxide (PEO)-based electrolytes are considered to be promising for all-solid-state battery, benefiting from the superior flexibility, excellent processability and well compatibility. However, the low ionic conductivity at room temperature and poor stability under high voltage limit their further application. Herein, ZIF-8@PVDF-HFP/PEO (PPZ) solid electrolyte was successfully prepared by facial electrospinning process. On one side, the cooperation of PVDF-HFP and ZIF-8 was benefit to decrease the crystallization degree of PEO and thus promoted the Li+ transfer. Moreover, the in-situ formed LiF layer derived from the decomposition of PVDF-HFP protected the electrolyte from contacting directly with the electrode, contributing to a stable electrode/electrolyte interface. The results demonstrated that the electrochemical stability and mechanical property of PPZ electrolyte were significantly improved when compared to the bare PEO electrolyte. The tensile strength increased from 0.5 to 6.7 MPa and the Li+ transference number enlarged from 0.17 to 0.48. More importantly, the assembled LCO(LiCoO 2)||PPZ||Li all-solid-state battery delivered a discharge specific capacity of 144.7 mAh g-1 at 0.2 C, nearly 1.6 times than that of the LCO||PEO||Li (90.7 mAh g-1). Besides that, the retention maintained at 86.3 % even after 200 cycles, manifesting a long-term cycling stability. This work provides a new idea for the practical application of PEO under high voltage. [ABSTRACT FROM AUTHOR]

Abstract A cross-linked porous polymer membrane using vinyl-functionalized aluminum oxide (Al 2 O 3) nanoparticles was prepared and used as a separator for lithium-ion batteries (LIBs). Poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) was first blended with a mixture solution containing poly(ethylene glycol) methyl ether methacrylate (PEGMEMA), vinyl-functionalized Al 2 O 3 nanoparticles (VTMO@Al 2 O 3) as the cross-linker and poly(vinyl pyrrolidone) (PVP) as the pore-forming agent. Subsequently, the membrane was obtained by free radical copolymerization of the above-mentioned mixture and after-treatment. The preparation and properties of the membranes were investigated. It has been found that, under the action of the pore-forming agent of PVP, the obtained membrane (PMAv) had high ionic conductivity (1.37 mS cm−1) at ambient temperature. On account of the existence of the Al 2 O 3 as cross-linking points, the PMAv membrane showed good mechanical strength of 30.4 MPa and excellent thermal stability at 180 °C. Moreover, comparing with the system without PVP or Al 2 O 3 samples, the cell with the PMAv membrane showed the best discharge capacity and most stable capacity retention and cycle performance, indicating that the PMAv membrane is a good polymer separator for LIBs. Highlights • Organic-inorganic hybrid Al 2 O 3 is selected as a cross-linker besides a filler. • The Al 2 O 3 cross-linked network improves thermal stability and mechanical strength. • The prepared membrane can be adjusted using PVP as the pore-forming agent. • The prepared membrane has high ionic conductivity and cycle performance. [ABSTRACT FROM AUTHOR]

Novel gel polymer electrolytes (GPEs) are prepared using poly(vinylidene fluoride-co-hexafluoro propylene) copolymer (PVdF-HFP) and polyethylene oxide (PEO) in presence of fumed silica nanofiller with the designated system of PVdF-HFP:PEO:EC:PC:NaI:SiO 2 :I 2 . GPEs are examined using electrochemical impedance spectroscopy (EIS) and the highest ionic conductivity of 8.84 mS cm −1 is achieved after incorporation of 13 wt.% of fumed silica (SiO 2 ). Temperature-dependent ionic conductivity study confirms that GPE system follows Arrhenius thermal activated model. GPEs are characterized for structural studies using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. GPEs are used to fabricate dye-sensitized solar cells (DSSCs) and tested under 1 Sun irradiation, obtaining the highest energy conversion efficiency of 9.44% after the incorporation of 13 wt.% fumed silica. Cyclic voltammetry has been performed to analyse electrochemical properties of gel polymer electrolytes. [ABSTRACT FROM AUTHOR]

• A three-component solid composite electrolyte is designed. • PVDF-HFP is difficult to be oxidized by high-voltage cathodes. • The controlled degradation of PPC can wet and stabilize the interface. • The NCM622/SCE/Li battery delivers good electrochemical performance Substituting flammable and leaky liquid electrolytes with advanced solid composite electrolytes considered as one of the most hopeful strategy to develop solid-state lithium metal batteries with high security and high energy density. However, it is still an arduous task to develop a solid electrolyte with high ionic conductivity and wide electrochemical window. To this end, we designed three-component solid poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP)/poly(propylene carbonate) (PPC)/Li 0.33 La 0.557 TiO 3 (LLTO) nanorods composite electrolyte. Oxidation-resistant PVDF-HFP can stabilize the cathode of lithium metal batteries and widen the electrochemical window. The controlled degradation of PPC can wet and stabilize the interface between the electrolyte and the lithium metal anode to a certain extent. The introduction of LLTO nanorods not only decreases the crystallinity of the composite solid electrolyte, but also provides an additional path for the transmission of lithium ions, and improves the ionic conductivity of the electrolyte membrane (2.18×10−4 S·cm−1 at room temperature). The Li/PPLSE3/Li symmetric cell assembled with this electrolyte has a long cycling life of 2000 h at a current density of 0.1 mA·cm−2 at room temperature. The assembled NCM622/PPLSE3/Li full battery has a specific discharge capacity of 142 mAh·g−1 and a capacity retention rate of 84.6% after 100 cycles at room temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the background, current research status and problems of separators for Li-ion batteries were reviewed first. Then a novel sandwich-like type of composite nonwoven separators was prepared to improve the performance of composite nonwoven Li-ion battery separators by combining SiO 2 /PVDF-HFP membranes with PVDF-HFP dipped PP nonwoven fabric. The physical and electrochemical properties of the composite separators were measured and analyzed. It is found that the mean pore size of the composite separators was in the range of 100 to 300 nm with maximum pore size less than 2 μm. The composite nonwoven-based separators possessed higher electrolyte uptake, stronger thermal stability, better wettability and lower interfacial resistance than the commercial PE separator. The batteries assembled with composite nonwoven separators showed stable cycling performance and improved rate performance. The composite nonwoven separators are expected to be a promising alternative to commercial PE separator. [ABSTRACT FROM AUTHOR]

A composite separator is prepared to improve the safety of lithium ion batteries (LIBs) based on a gravure coating aqueous slurry and post-hot-pressing method. An environmentally friendly aqueous slurry with an Al 2 O 3 ceramic holder and polyvinylidene difluoride-hexafluoropropylene (PVdF-HFP ) and carboxymethyl cellulose (CMC) dual-binders is coated on a polyolefin (PE) substrate to form a prototype Al-PHC/PE separator. Then, after assembling the separator in the batteries and hot-pressing at 70 °C and 0.8 MPa for 3 h, the granular PVdF-HFP is transformed into a colloidal structure containing an electrolyte, which can binds the Al 2 O 3 nanoparticles together and increases the battery hardness. Compared with a PE separator (9 μm), the Al-PHC/PE-2 separator (12 μm, with a Al 2 O 3 /PVdF-HFP weight ratio of 7/3) displays a comparative ionic conductivity of 9.3 × 10 −4 S cm −2 and exhibits no obvious thermal deformation at 110 °C for 60 min. All of the batteries assembled with Al-PHC/PE-2 separators passed nail penetration and impact tests. In addition, the capacity retention increases from 83.4% to 87.6% when the battery is assembled with Al-PHC/PE-2 instead of a PE separator and charge-discharged at 0.7C/1.0C for 350 cycles. The enhanced safety and cycle performance indicate the promising prospect of Al-PHC/PE separators in LIBs. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) composite polymer electrolyte loaded with 3-isocyanatopropyltriethoxysilane (IPTES) functionalized zirconium oxide (ZrO 2 ) nanoparticles is successfully synthesized and evaluated for electrochromic application. Incorporation of ZrO 2 into the polymeric substrate enhances the ionic conductivity of the electrolyte. Meanwhile, the functionalization of ZrO 2 nanoparticles with IPTES ligand enhances the electrolyte’s optical transmissivity. The amount of ligand and its time of reaction with ZrO 2 are found to affect the overall property of the electrolyte. The electrolyte exhibits a balance of low crystallinity and low ZrO 2 aggregation and agglomeration resulting to a potential next generation electrolyte for energy efficient windows. [ABSTRACT FROM AUTHOR]

• Novel tri-composites for advanced application were prepared by solvent casting. • Tri-composites are based on MFI and [BMIM][SCN] IL fillers dispersed in a PVDF-HFP polymer matrix. • Mechanical and electric properties can be tuned depending on filler type and content. • The tri-composites show a high ionic conductivity of 3.9 × 10−5 S.cm−1 for the composite with 30 wt.% IL content. • The tri-composites are suitable for lithium-ion battery and bending actuator applications. In order to improve the multifunctionality of polymer composites for advanced applications a novel tri-composite material is presented based on the inclusion of MFI zeolite and the ionic liquid (IL) 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) in an electroactive poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix. Tri-composites were produced by solvent casting with a relative overall filler content up to 40 wt.%. A compact film morphology is obtained, and the polymer degradation temperature and degree of crystallinity are independent on the filler content and type. On the other hand, the polymer crystalline phase depends on the presence of the IL but is independent of its content. Regarding the mechanical properties, it is observed that the IL has a plasticizing effect with a significant contribution to the reduction of the Young's modulus from 151 MPa for the pristine polymer to 92 MPa for the 30 wt.%/10 wt.% IL/MFI content sample. A high ionic conductivity value at room temperature of 3.9 × 10−5 S.cm−1 was obtained for the tri-composite with the highest IL content (30 wt.%/10 wt.% IL/MFI). The tri-composite system was studied as solid polymer electrolyte (SPE) for battery and bending actuator applications, demonstrating the multifunctionality of the material. The sample with the best cycling performance was observed for the highest MFI content (10 wt.%/30 wt.% IL/MFI) with a discharge capacity value of 110 mAh.g−1 and maintaining almost 80% of its initial capacity after 30 cycles at the C/10 rate. Regarding to the bending performance, the best bending actuation was detected for highest IL content (30 wt.%/10 wt.% IL/MFI), related to the ionic conductivity of the sample. Thus, it is demonstrated that the new tri-composite system, due to its tunable characteristics as a function of the relative IL and zeolite contents, is suitable for a next generation of multifunctional polymer composite materials for advanced applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([bdmim]BF 4 ) ionic liquid is introduced into poly(vinyl pyrrolidone)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVP/PVdF-HFP) blend host to prepare a gel polymer electrolyte (PVP/PVdF-HF-Mg(CF 3 SO 3 ) 2 ) system for a symmetrical solid-state electrical double layer capacitor (EDLC). Ionic liquid-incorporated gel polymer electrolyte (GPE) containing 7.5 wt.% [bdmim]BF 4 exhibits the optimum room temperature ionic conductivity of (2.92 ± 0.02) × 10 −3 S cm −1 and is electrochemically stable up to +2.4 V. The specific capacitance ( C s ) of the optimised GPE at 100 th cycle with porous carbon as electrode delivers 95, 133, 108 and 117 F g −1 at operating voltage of 0.8, 1.0, 1.6 and 2.0 V, respectively, under a constant current density of 100 mA g −1 . The solid-state displays the highest energy and power density of 14 W h kg −1 and 21 W kg −1 , respectively, at an operating potential of 1.0 V, which qualifies the GPE-IL for symmetrical solid-state EDLC application. [ABSTRACT FROM AUTHOR]

Abstract: In this work, 1–butyl–3–methyl imidazolium trifluoromethanesulfonate (BMITf) is employed as ionic liquid in polymer blend electrolyte system based on poly(ethyl methacrylate) (PEMA) and poly(vinylidenefluoride–co–hexafluoropropylene) (PVdF–HFP) in the weight ratio of 70 to 30. The films were prepared by solution casting. Lithium trifluoromethanesulfonate (LiTf) is the lithium ion (Li+) provider. Addition of BMITf into the optimized PEMA/PVdF–HFP–LiTf composition increased the ionic conductivity of the system. The highest room temperature ionic conductivity of 8.59×10−5 S cm−1 was exhibited by PEMA/PVdF–HFP–LiTf containing 60wt.% BMITf. Vibrational studies by FTIR show that the imidazolium cation (BMI+) interacts with the oxygen atoms in C=O and C–O–C groups of PEMA, and also fluorine atoms in CF2 groups of PVdF–HFP. Addition of BMITf into the PEMA/PVdF–HFP–LiTf system increases the amount of free ions leading to improvement in the ionic conductivity. The thermal stability of the polymer electrolytes is improved to above 275°C by the addition of BMITf. [Copyright &y& Elsevier]

Abstract: Gel type polymer electrolytes with PVDF-HFP as polymer host, NaI salt and EC/PC as plasticizers have been prepared and optimized for use in a dye sensitized solar cell (DSSC). The polymer electrolyte containing 48wt. % (PVDF-HFP)–32wt. % NaI–20wt. % (EC/PC) exhibits the highest room temperature conductivity of 1.53×10−4 S cm−1. This electrolyte has been used in the fabrication of a DSSC with the configuration FTO/TiO2/natural dye/electrolyte/Pt/FTO. The natural dyes used anthocyanin and chlorophyll were solvent extracted from black-rice and pandanus amaryllifolius leaves respectively. UV-vis absorption spectra of anthocyanin, chlorophyll and the mixture of anthocyanin and chlorophyll in the volume ratio 1:1 were recorded. The anthocyanin shows an absorption peak at 532nm. In the same region chlorophyll absorption shows a peak at 536nm and also has a prominant peak at 665nm. On mixing anthocyanin and chlorophyll two prominant peaks are observed at 536 and 665nm. The DSSC containing the dye mixture exhibits the best performance with a short-circuit current density of 2.63mAcm−2, open-circuit voltage of 0.47V, fill factor of 0.58 and the highest photo-conversion efficiency of 0.72% under the illumination of 100mW cm−2 white light. Under illumination of lower light intensity of 60mW cm−2 and 30mW cm−2, the fill factor enhanced from 0.58 to 0.59 and 0.60 and the photo-conversion efficiency increased from 0.72% to 1.11% and 1.85% respectively. [Copyright &y& Elsevier]

Abstract: Core–shell structural single ionic conductor SiO2@Li+ was successfully synthesized from vinyltriethoxysilane, sodium p-styrenesulfonate and LiOH·H2O by hydrolysis, polymerization and ion exchange and confirmed by TEM and FT-IR. The poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP)-based composite polymer electrolyte (CPE) membrane doped with SiO2@Li+ was prepared by phase inversion method and the desirable CPE was obtained after being activated in liquid electrolyte. The physicochemical properties of the CPE were characterized by SEM, XRD, TG, and electrochemical measurements. The results show that the CPE membrane presents uniform surface with abundant interconnected micro-pores and possesses excellent mechanical performance with high decomposition temperature about 450°C; and adding SiO2@Li+ into matrix remarkably decreases the crystallinity but enhances ionic conductivity of the CPE membrane; the ionic conductivity and lithium ion transference number at room temperature are up to 3.885mScm−1 and 0.4374, respectively, and the reciprocal temperature dependence of ionic conductivity of as-prepared CPEs follows Vogel–Tamman–Fulcher relation. The battery properties of the assembled cells using CPE doped with SiO2@Li+ as electrolyte show excellent rate and cycle performance, which is partly attributed to the improved interfacial performance between the electrolyte and electrodes and partly to enhanced electrochemical working window and lithium ion transference number. [Copyright &y& Elsevier]

Abstract: Macroporous polymer separators based on poly(vinylidene fluoride) (PVdF) and several VdF copolymers were prepared by a phase inversion process using acetone as a solvent. The resulting macroporous separators were characterized in terms of morphology, swelling behaviour, thermal and mechanical properties and ionic conductivity. The PVdF separator had a highly porous structure (80%) and exhibited good mechanical properties. Once filled by a molar solution of tetraethylammonium tetrafluoroborate (TEABF4) in acetonitrile (AN) it provided enhanced conductivity (18mScm−1 at 25°C) compared with commercial cellulose and Celgard™ separators. [Copyright &y& Elsevier]

Abstract: In the present work, novel gel-based composite polymer electrolytes for lithium batteries were prepared by introducing a hierarchical mesoporous silica network to the poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based gel electrolytes. As compared with the PVDF-HFP-based gel electrolytes with/without conventional nano-sized silica fillers, the novel electrolytes have shown more homogeneous microstructure, higher ionic conductivity and better mechanical stability, which could be caused by the strong silica network and the effective interactions among the polymer, the liquid electrolytes and the silica. Moreover, the cell with this kind of electrolytes could achieve a discharge capacity as much as 150mAhg−1 at room temperature (LiCoO2 as the cathode active material), with high Coulomb efficiency. [Copyright &y& Elsevier]

Abstract: In order to improve the discharge capacity in lithium ion microbatteries, a thick-film cathode was fabricated by a screen printing using LiCoO2 pastes. The printed cathode showed a different discharge curves when the cell was tested using various (liquid, gel and solid-state) electrolytes. When a cell test was performed with organic liquid electrolyte, the maximum discharge capacity was 200μAhcm−2, which corresponded to approximately 133mAhg−1 when the loading weight of LiCoO2 was calculated. An all-solid-state microbattery could be assembled using sputtered LiPON electrolyte, an evaporated Li anode, and printed LiCoO2 cathode films without delamination or electrical problems. However, the highest discharge capacity showed a very small value (7μAhcm−2). This problem could be improved using a poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) gel electrolyte, which enhanced the contact area and adhesion force between cathode and electrolyte. The discharge value of this cell was measured as approximately 164μAhcm−2 (≈110mAhg−1). As the PVDF-HFP electrolyte had a relatively soft contact property with higher ionic conductance, the cell performance was improved. In addition, the cell can be fabricated in a leakage-free process, which can resolve many safety problems. According to these results, there is a significant possibility that a film prepared using the aforementioned paste with screen printing and PVDF-HFP gel electrolyte is feasible for a microbattery. [Copyright &y& Elsevier]

Abstract: We have built TiO2 Dye sensitized solar cells (DSSCs) that combined flexible TiO2 photoanodes coated on ITO/PET substrates with a gel electrolyte based on PVDF–HFP–SiO2 films. Titanium isopropoxide (TiP4) was used as additive to TiO2 nanoparticles for increasing power conversion efficiency in Dye sensitized solar cell electrodes prepared at low-temperature (130°C). An efficiency η AM1.5G =3.55% on ITO/PET substrates is obtained at 48mW/cm2 illumination with a standard liquid electrolyte based on methoxypropionitrile. Among several solvents forming gels with PVDF–HFP–SiO2, N-methyl (pyrrolidone) (NMP) was found to enable the most stable devices. A power conversion efficiency η AM1.5G =2% was obtained under 10mW/cm2 with flexible TiO2–ITO–PET photoanodes and the PVDF–HFP–SiO2 +NMP gel electrolyte. [Copyright &y& Elsevier]

γ-LiAlO2, Al2O3 and MgO were used as fillers in a PVdF-HFP polymer matrix to form self-standing, intrinsically porous separators for lithium-ion batteries. These separators can be hot-laminated onto the electrodes without losing their ability to adsorb liquid electrolyte. The electrochemical stability of the separators was tested by constructing half-cells with the configuration: Li/fibre-glass/filler-based separator/electrode. MgO-based separators were found to work well with both positive and negative electrodes. An ionic conductivity of about 4×10−4 S cm−1 was calculated for the MgO-based separator containing 40% 1 M solution of LiPF6 in an EC/DMC 1:1 solvent. Self-standing, lithium-ion cells were constructed using the MgO-based separator and the resulting battery performance evaluated in terms of cyclability, power and energy density. [Copyright &y& Elsevier]

• Different lithium salts at various concentrations were impregnated into PVDF:HFP polymer matrix to reveal their effects in various electrochemical performances of Li-O 2 batteries. • Opaque and transparent gel-polymer electrolytes(GPE) were obtained by changing the substrate temperature in which the GPE poured onto. • GPE was coated onto the Gas Diffusion Layer (GDL) cathode to increase the intimate contact. • FTIR analysis was carried out to ascertain the impregnation of lithium salts into PVDF:HFP matrix. • Our results indicate the need for the development of a lithium salts capable of serving decent electrochemical performance in all aspects of electrochemistry. Among rechargeable lithium batteries, lithium-oxygen batteries (Li-O 2) offer remarkable energy densities which make them to be considered as the next generation energy storage systems. However, intrinsic problems arising from the use of liquid electrolytes has to be overcome before their adoption into the market. Gel-polymer electrolytes (GPEs) are now considered as the next-generation electrolytes to be utilized in Li-O 2 systems. PVDF-HFP polymers with different lithium salts were successfully utilized as gel-polymer electrolytes to replace liquid electrolytes in Li-O 2 batteries. However, the electrochemical performance of different lithium salts dissolved in PVDF-HFP matrices are limited in different aspects, i.e. (electro)chemical stability, ionic conductivity, interfacial stability, cycle stability or lithium-ion transference number. In this study, we systematically observed the effect of different lithium salts at various concentrations on the above mentioned electrochemical properties. Our results indicate that LiPF 6 salt imparts best ionic conductivity into GPE systems while LiTFSI has both the widest electrochemical window and highest lithium-ion transference number. Our results indicate that the synthesis of new lithium salts having decent electrochemical performance in all aspects is of great importance in developing GPE systems. [ABSTRACT FROM AUTHOR]