Optimum Ionic Conductivity Research Articles

Ionic Liquid-Supported Interpenetrating Polymer Network Flexible Solid Electrolytes for Lithium-Ion Batteries

In this report, we have prepared the imidazolium-based ionic liquid-incorporated interpenetrating polymer network (IPN) electrolyte membrane containing cellulose triacetate with polyethylene glycol dimethyl acrylate and polyethylene oxide by the UV-induced polymerization method. A facile IPN electrolyte membrane appears to be homogeneous in nature with high mechanical strength, excellent thermal stability, and exhibits optimum ionic conductivity of the order of 2.84 × 10–3 S cm–1. The oxidative stability of the IPN electrolyte membrane is observed up to 5.2 V at room temperature, which is attributed to immobilized ion networks provided by the imidazolium ionic liquid. The IPN electrolyte membrane is galvanostatically cycled having battery configuration Li/IPN EM/LiFePO4, which shows the first discharge capacity of 110 mA h g–1 at 0.05 C with 93.65% Coulombic efficiency at room temperature. The cell shows discharge capacities of about 85, 82, and 76 mA h g–1 at 0.1, 0.2, and 1 C rates, respectively. The ionic liquid-incorporated IPN electrolyte membrane provides a promising system for stabilizing lithium electrodeposition and fabricating high-performance lithium-ion batteries. Finally, IPN electrolyte membranes could be a potential electrolytes for next-generation high-power and safer solid-state battery technology.

Enhancement of Superionic Conductivity by Halide Substitution in Strongly Stacking Faulted Li3HoBr6–xIx Phases

Ternary lithium halide-based solid electrolytes have attracted broad scientific interest due to their high ionic conductivities in conjunction with good electrochemical stabilities against high-voltage cathode materials. Here, we analyze the structure of the rare earth halide solid solution series Li3HoBr6–xIx and quantify structural defects such as intralayer cation disorder and stacking faults. Almost all members of the solid solution series show strong stacking fault disorder, whereas the intralayer cation disorder systematically increases with increasing iodide content. The substitution of bromide by iodide in Li3HoBr6–xIx leads to an increasing lattice softness and therefore to a higher ionic conductivity and to a lower activation energy. This is counteracted by the increased cation disorder, which also has a strong influence on the ionic conductivity of the solid solution series. Thus, a decrease in ionic conductivity by one order of magnitude is observed when the iodine content exceeds an optimum value. Stacking faults on the other hand do not have a significant impact on the ionic conductivity as the connectivity between neighboring lithium halide octahedra and hence the energy landscape of their migration pathways is not affected for equivalent stacking vectors. The competing factors above give rise to an optimum ionic conductivity at x ≈ 3 with 2.7 × 10–3 S cm–1 at 20 °C and an activation energy of 0.21 eV. While thermal annealing reduces the structural disorder of Li3HoBr6–xIx, the self-healing properties are significantly impeded by mechanical sample treatment, demonstrating the complex interplay between thermal and mechanical effects on the microstructure and, hence, ionic conductivity of layered superionic conductors.

Novel electrospun separator‐electrolyte based on PVA‐K2CO3‐SiO2‐cellulose nanofiber for application in flexible energy storage devices

AbstractElectrospun fiber membrane as a separator‐electrolyte have been prepared in this study using electrospinning process from cellulose acetate, PVA, K2CO3, and SiO2 with different concentrations. Five different concentration were prepared (14–22 wt%) using mixture of dimethyl sulfoxide and acetone in a fixed ratio of 2:3. The prepared electrospun membranes were characterized and shown to exhibit good and well‐structured morphology formed by interlaying of fibers, where the thinnest and finest fibers were achieved at 20 wt% polymer concentration, resulting in average diameters of 480 ± 80 nm. The prepared membranes were activated with plasticized gel polymer electrolyte where its electrochemical properties/performance was evaluated. Based on the good porous nature of the fiber, the membrane with 20 wt% concentration exhibited good electrolyte uptake of 450.75% that is higher than the commercially prepared separator. Similarly, the membranes displayed good electrolyte retention (R) ability of 8.8. The ionic conductivity studies revealed that, the conductivity of the electrospun membranes increased with increasing polymer concentration up to 20 wt% where an optimum ionic conductivity of 3.73 × 10−3 and 7.54 × 10−3 Scm−1 at ambient temperature and 373.15 K, respectively, have been achieved. The oxidation stability of the prepared membrane in this study showed a good electrochemical stability of up to 4.8 V that is higher than that of the commercially prepared membrane and other reported electrolytes.

Studies on the effect of H+ carrier toward ionic conduction properties in alginate-ammonium sulfate complexes–based polymer electrolytes system

The present work highlights the contribution of ammonium sulfate (NH4)2SO4 as H+ carriers in alginate-based solid polymer electrolytes (SPEs) that were successfully prepared via a solution casting technique. The Fourier transform infrared analysis revealed that molecular interactions between the host polymer and the ionic dopant complexes occurred at the wavenumbers 3700–2500 cm−1, 1800–1500 cm−1, and 1200–900 cm−1. These regions corresponded to the O-H stretching, COO− and C-O-C, moieties of alginate, respectively, which coordinated with the H+ carrier from (NH4)2SO4. At ambient temperature, the optimum ionic conductivity was obtained at 3.01 × 10−5 S cm−1 for the sample containing 10 wt.% of (NH4)2SO4. The IR-deconvolution approach shows that the ionic conduction enhancement is governed by the ionic mobility and the diffusion coefficient of H+ carriers, and the findings show that the present biopolymer, which is an alginate-based SPEs system, has an excellent possibility to be used as electrolytes for application in electrochemical devices.

Involvement of ethylene carbonate on the enhancement H+ carriers in structural and ionic conduction performance on alginate bio-based polymer electrolytes

This study investigates the structural and ionic conduction performance with the involvement of ethylene carbonate (EC) in a bio-based polymer electrolytes (BBPEs) system, based on alginate doped glycolic acid (GA). The solution casting technique was used to successfully prepare the BBPEs which were characterized with various approaches to evaluate their ionic conduction performance. It was revealed that at ambient temperature, an optimum ionic conductivity of 9.06 × 10−4 S cm−1 was achieved after the addition of 6 wt% EC, with an observed improvement of the amorphous phase and thermal stability. The enhancement of ionic conduction properties is believed to be due to the protonation (H+) enhancement, as proven by FTIR and TNM studies. The findings show that the developed alginate-GA-EC is a promising candidate for use as electrolytes in electrochemical devices that are based on H+ carriers.

Influence of Electron beam radiation on the properties of Surface-Modified Titania-Filled gel polymer electrolytes using vinyltriethoxysilane (VTES) for lithium battery application

Gel polymer electrolytes (GPEs) are regarded as a prospective alternative for traditional liquid electrolytes. The dispersion of nanofiller in GPEs has been proven to improve the electrolyte’s properties, such as reduced reactivity and leakage, improved safety, better shape flexibility, as well as manufacturing integrity. Meanwhile, the introduction of Electron Beam (EB) radiation remarkably enhances the electrochemical properties of GPEs. Therefore, the aim of the present work was to investigate the properties of titania-filled 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4)–poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) upon in-situ surface modification using vinyltriethoxysilane (VTES) coupling agent and its response towards 8 MeV energy EB irradiation. Following the surface modification of titania using VTES at different weight percentages (10–40%) and EB radiation exposure (5–20 kGy), the physicochemical, thermal, morphological, and electrochemical characteristics of the GPE were analyzed via Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), and impedance analysis, respectively. Based on the results, the TGA analysis showed that the thermal stability of the GPE increased with the increment of residues, which indicate the successful ceramics attachment onto the silanol group from the silane in the VTES compound. After the surface modification on the ceramic particle, the obtained average size particle was 50 nm with further enhancement of the particle distribution was observed when exposed to EB radiation. Additionally, the impedance analysis showed that the modified surface of the titania system achieved an optimum ionic conductivity of 10−2 S cm−1 at room temperature. When the electrolytes were exposed to EB radiation, the ionic conductivity increased up to 10−1 S cm−1 with the lithium transference number calculated at 0.52. These remarkable findings indicate that the developed surface modification technique of titania together with EB radiation on GPEs is a promising electrolyte for lithium-ion battery application.

Efficient improvement of the lithium ionic conductivity for a polymer electrolyte via introducing porous metal-organic frameworks.

The electrolyte membrane plays a vital role in the practical conduction application of lithium-ion batteries. In this study, a series of PVDF-HFP/MOF-5 composite electrolyte materials were harvested by incorporating MOF-5 into PVDF-HFP, presenting excellent electrochemical characteristics and mechanical properties. Importantly, the performances of the PVDF-HFP/MOF-5 composites depended greatly on the content of MOF-5 introduced and the channels change. The PVDF-HFP/MOF-5-II with a MOF-5 content of 2 wt% revealed optimal ionic conductivity of 1.20 × 10-3 S cm-1 and lithium ion transference number of 0.9 at room temperature, which shows potential application prospects in the field of electrolyte materials.

Novel fast lithium-ion conductor LiTa2PO8 enhances the performance of poly(ethylene oxide)-based polymer electrolytes in all-solid-state lithium metal batteries

At present, replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards. Composite solid electrolytes (CPEs) have excellent ionic conductivity and flexibility owing to the combination of functional inorganic materials and polymer solid electrolytes (SPEs). Nevertheless, the ionic conductivity of CPEs is still lower than those of commercial liquid electrolytes, so the development of high-performance CPEs has important practical significance. Herein, a novel fast lithium-ion conductor material LiTa2PO8 was first filled into poly(ethylene oxide) (PEO)-based SPE, and the optimal ionic conductivity was achieved by filling different concentrations (the ionic conductivity is 4.61 × 10−4 S/cm with a filling content of 15 wt% at 60 °C). The enhancement in ionic conductivity is due to the improvement of PEO chain movement and the promotion of LiTFSI dissociation by LiTa2PO8. In addition, LiTa2PO8 also takes the key in enhancing the mechanical strength and thermal stability of CPEs. The assembled LiFePO4 solid-state lithium metal battery displays better rate performance (the specific capacities are as high as 157.3, 152, 142.6, 105 and 53.1 mAh/g under 0.1, 0.2, 0.5, 1 and 2 C at 60 °C, respectively) and higher cycle performance (the capacity retention rate is 86.5% after 200 cycles at 0.5 C and 60 °C). This research demonstrates the feasibility of LiTa2PO8 as a filler to improve the performance of CPEs, which may provide a fresh platform for developing more advanced solid-state electrolytes.

Effect of C3H4O3 on Band Gap Narrowing of Proton Conductive Hybrid Polymer Electrolyte

AbstractIn the present work, hybrid polymer electrolyte based on carboxymethyl cellulose‐polyvinyl alcohol‐ammonium nitrate‐ethylene carbonate (CMC–PVA–NH4NO3–C3H4O3) become the promising materials that has demonstrated outstanding physical properties as an electrolytes system in solar cell. In the frame of solar cell progress, the electrical conductivity and optical bandgap of polymer electrolytes are equally explored. The characterization is carried out via electrical impedance spectroscopy (EIS) and ultraviolet visible‐near infrared (UV‐VIS‐NIR) spectroscopy. An equivalent circuit of parallel combination, bulk resistance (Rb), and constant phase element (CPE) is obtained from transparent conductive film, CMC–PVA–NH4NO3–C3H4O3. The optimum ionic conductivity is accomplished at 3.92 × 10−3 S cm‐1 for sample containing with 6 wt.% of C3H4O3. The absorption spectra are evaluated in the wavelength ranging from 200 to 1100 nm. Theoretical analysis reveals that the addition of 6 wt. % EC is initiating the band gap narrowing from 4.96 to 4.88 eV. The results show that the present developed materials‐based polymer electrolytes have great potential for solar energy devices.

BODIPY‐Pt‐Porphyrins Polyads for Efficient Near‐Infrared Light‐Emitting Electrochemical Cells

The synthesis, characterization, and application in light‐emitting electrochemical cells (LECs) of two near‐infrared (NIR)‐emitting Pt‐porphyrins (Pt‐por) with none or 20 F atoms and their respective Pt‐por polyads containing from 1 to 4 BODIPY (BDP) units (PtBDP) connected via tetra‐fluorophenyl triazole spacer groups are reported. The functionalization of PtBDPs is tuned with respect to the number of BDP units and F atoms optimizing 1) the NIR emission through an efficient energy transfer from the BDP to the Pt‐por core, 2) the electronic structure to decouple charge transport via BDP and exciton formation at the Pt‐por, and 3) the ionic conductivity in thin films. A comprehensive rationale on how the molecular design rules the device performance is provided, achieving LECs with emission at 780 nm. This is realized using PtBDP‐2‐8, in which a host:guest strategy between BDP and Pt‐por in thin films is fully operative accompanied by an optimal ionic conductivity. This is supported by spectroelectrochemical findings and device analysis with both Pt‐por references and the PtBDP series. Overall, this work highlights that Pt‐porphyrins are efficient emitters in developing NIR LECs due to their rich functionalization, enabling to control charge transport, energy transfer, and ionic conductivities.

Phase-field Determination of NaSICON Materials in the Quaternary System Na2 O-P2 O5 -SiO2 -ZrO2 : The Series Na3 Zr3-x Si2 Px O11.5+x/2.

Two types of solid electrolytes have reached technological relevance in the field of sodium batteries: ß/ß”‐aluminas and NaSICON‐type materials. Today, significant attention is paid to room‐temperature stationary electricity storage technologies and all‐solid‐state Na batteries used in combination with these solid electrolytes are an emerging research field besides sodium‐ion batteries. In comparison, NaSICON materials can be processed at lower sintering temperatures than the ß/ß”‐aluminas and have a similarly attractive ionic conductivity. Since Na2O−SiO2−ZrO2−P2O5 ceramics offer wider compositional variability, the series Na3Zr3–xSi2PxO11.5+x/2 with seven compositions (0≤x≤3) was selected from the quasi‐quaternary phase diagram in order to identify the predominant stability region of NaSICON within this series and to explore the full potential of such materials, including the original NaSICON composition of Na3Zr2Si2POl2 as a reference. Several characterization techniques were used for the purpose of better understanding the relationships between processing and properties of the ceramics. X‐ray diffraction analysis revealed that the phase region of NaSICON materials is larger than expected. Moreover, new ceramic NaSICON materials were discovered in the system crystallizing with a monoclinic NaSICON structure (space group C2/c). Impedance spectroscopy was utilized to investigate the ionic conductivity, giving clear evidence for a dependence on crystal symmetry. The monoclinic NaSICON structure showed the highest ionic conductivity with an optimum ionic conductivity of 1.22×10−3 at 25 °C for the composition Na3Zr2Si2PO12. As the degree of P5+ content increases, the total ionic conductivity is initially enhanced until x=1 and then decreases again. Simultaneously, the increasing amount of phosphorus leads a decrease in the sintering temperatures for all samples, which was confirmed by dilatometry measurements. The thermal and microstructural properties of the prepared samples are also evaluated and discussed.

Enhancement on protonation (H+) with incorporation of flexible ethylene carbonate in CMC–PVA–30 wt % NH4NO3 film

In the present work, carboxymethyl cellulose (CMC)–polyvinyl alcohol (PVA)–NH4NO3 with the addition of ethylene carbonate (EC) based polymer blend electrolyte (PBE) was explored. The complexes of PBE with addition of EC revealed that an interaction of the –OH and –COO− of the CMC–PVA blend with the dissociation of H+ from NH4NO3 provides a flexibility pathway for ion hopping. The optimum ionic conductivity at room temperature was found to be 3.92 × 10−3 S/cm for the sample containing 6 wt.% EC with an increment of amorphous phase and thermal stability. Based on the Impedance-Nyquist theoretical approach, it was shown that the ionic conductivity with cation transference number (tH+= 0.48) of the PBE is primarily influenced by the ionic mobility as well as the ions diffusion coefficient. The findings verified that the CMC–PVA–NH4NO3–EC possesses favorable conduction properties upon physical structural modification as a promising polymer electrolyte.

Electrochemical Performance of LixSiON Polymer Electrolytes Derived from an Agriculture Waste Product, Rice Hull Ash

The electrochemical performance of LixSiON (x = 2, 4, and 6) polymer electrolytes derived from the agricultural waste, rice hull ash (RHA, 80–90 wt % SiO2), is reported. Silica can be extracted from RHA by base-catalyzed reaction with hexylene glycol forming the spirosiloxane [(C6H12O2)2Si, SP] that distills from the reaction solution. LixSiON polymer electrolytes form on reacting SP with xLiNH2, offering a low-cost, low-temperature, and green synthesis route. The effect of N and Li+ concentrations in the polymer electrolytes are correlated with ionic and electrical conductivity. X-ray photoelectron spectroscopy studies confirm that N and Li contents increase with increasing LiNH2 content. The amorphous nature and high Li+ contents of the Li6SiON electrolyte provide an optimal ionic conductivity (6.5 × 10–6) at ambient temperature when coated on Celgard. Furthermore, the LixSiON polymer electrolytes offer high Li+ transference numbers (∼0.75–1), enabling assembly of Li symmetric cells with high critical current densities (3.75 mA cm–2). Finally, Li-SPAN (sulfurized, carbonized polyacrylonitrile) half-cells with Li6SiON polymer electrolytes deliver discharge capacities of ∼765 and 725 mAh/g at 0.25 and 0.5 C rates over 50 cycles.

Elucidating the relationship between mechanical properties and ionic conductivity in a highly conductive gel polymer electrolyte

The storage modulus and ionic conductivity of prototypical gel electrolytes consisting of different amounts of poly (vinyl alcohol) and the ionic liquid 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMI TFSI) were made and characterized. Peak ionic conductivity and room temperature storage modulus of 2.4 × 10−2 S cm−1 and 128 MPa respectively were achieved. The gel electrolytes were also characterized with a multifunctional index. It was found that the optimal ionic conductivity and mechanical properties were obtained with 40 wt% EMI TFSI loading, where an ionic conductivity of 1.2 × 10−3 S cm−1 and a room temperature storage modulus of 30.7 MPa were obtained. A specific capacitance of 29.24 F g−1 was obtained in a test supercapacitor device.

Dielectric Study of Gel Polymer Electrolyte Based on PVA-K2CO3-SiO2

In this study, effect of filler (SiO2) on dielectric and electrical properties of gel polymer electrolyte (GPE) based on PVA-K2CO3 has been investigated and reported. The electrolyte were prepared by incorporating silica particle as a filler into the un-plasticized electrolyte (PVA-K2CO3). The prepared electrolyte were characterized physicochemically (FTIR) and electrochemically based on electrochemical impedance spectroscopy (EIS). Based on the impedance spectroscopy, complex permittivity (ε*) (dielectric constant and loss) and complex electrical modulus (M*) (real and imaginary modulus) were calculated. Characterization result indicate that SiO2 particles has successfully interacts with PVA-K2CO3 in the form of a three dimensional polymeric network. At low frequencies, high values of complex permittivity (dielectric constant and dielectric loss) were observed, which increased with increasing temperature, signifying an increase in ionic conductivity of the electrolyte. With the incorporation of filler, the peaks of both ε* and M* shifts towards higher frequency side suggesting the speed up the relaxation time. From the electrical modulus, the developed electrolyte is shown to be highly capacitive in nature. Based on the peak shape of the imaginary part of electric modulus, the non-Debye type relaxation predicted. Analysis of both dielectric permittivity and electrical modulus suggest that ionic and polymer segmental motions are strongly coupled. An optimum ionic conductivity of 3.25 × 104 mScm1 was achieved at ambient temperature at a composition of 15 wt.% SiO2 (PKS15).

Optimization of the Electrochemical Performance of a Composite Polymer Electrolyte Based on PVA-K2CO3-SiO2 Composite.

Composite polymer electrolyte (CPE) based on polyvinyl alcohol (PVA) polymer, potassium carbonate (K2CO3) salt, and silica (SiO2) filler was investigated and optimized in this study for improved ionic conductivity and potential window for use in electrochemical devices. Various quantities of SiO2 in wt.% were incorporated into PVA-K2CO3 complex to prepare the CPEs. To study the effect of SiO2 on PVA-K2CO3 composites, the developed electrolytes were characterized for their chemical structure (FTIR), morphology (FESEM), thermal stabilities (TGA), glass transition temperature (differential scanning calorimetry (DSC)), ionic conductivity using electrochemical impedance spectroscopy (EIS), and potential window using linear sweep voltammetry (LSV). Physicochemical characterization results based on thermal and structural analysis indicated that the addition of SiO2 enhanced the amorphous region of the PVA-K2CO3 composites which enhanced the dissociation of the K2CO3 salt into K+ and CO32− and thus resulting in an increase of the ionic conduction of the electrolyte. An optimum ionic conductivity of 3.25 × 10−4 and 7.86 × 10−3 mScm−1 at ambient temperature and at 373.15 K, respectively, at a potential window of 3.35 V was observed at a composition of 15 wt.% SiO2. From FESEM micrographs, the white granules and aggregate seen on the surface of the samples confirm that SiO2 particles have been successfully dispersed into the PVA-K2CO3 matrix. The observed ionic conductivity increased linearly with increase in temperature confirming the electrolyte as temperature-dependent. Based on the observed performance, it can be concluded that the CPEs based on PVA-K2CO3-SiO2 composites could serve as promising candidate for portable and flexible next generation energy storage devices.

Maximizing ionic transport of Li1+xAlxTi2-xP3O12 electrolytes for all-solid-state lithium-ion storage: A theoretical study

The concept of all-solid-state batteries provides an efficient solution towards highly safe and long-life energy storage, while the electrolyte-related challenges impede their practical application. Li1+xAlxTi2-xP3O12 (0 ≤ x ≤ 1) with superior Li ionic conductivity holds the promise as an ideal solid-state electrolyte. The intrinsic mechanism to reach the most optimum ionic conductivity in Al-doped Li1+xAlxTi2-xP3O12, however, is unclear to date. Herein, this work intends to provide an atomic scale study on the Li-ion transport in Li1+xAlxTi2-xP3O12 electrolyte to rationalize how Al-dopant initiates interstitial Li activity and facilitate their easy mobility combining Density Functional Theory (DFT) and ab initio Molecular dynamics (AIMD) simulations. It is discovered that the interstitial Li ions introduced by Al dopants can effectively activate the neighboring occupied intrinsic Li-ions to induce a long-range mobility in the lattice and the maximum Li ionic conductivity is achieved at 0.50 Al doping concentration. The Li- ion migration paths in Li1+xAlxTi2-xP3O12 have investigated as the degree of distortion of [PO4] tetrahedra and [TiO6] octahedra resulted by different Al doping concentrations. The asymmetry of the surrounding distorted [PO4] and [TiO6] polyhedrons play a critical role in reducing the migration barrier of Li ions in Li1+xAlxTi2-xP3O12. The flexible [TiO6] polyhedrons with a capacity to accommodate the structural distortion govern the Li ionic conductivity in Li1+xAlxTi2-xP3O12. This work rationalizes the mechanism for the most optimum Li ionic conductivity in Al-doped LiTi2P3O12 electrolyte and, more importantly, paves a road for exploring novel all-solid-state lithium battery electrolytes.

Preparation and characterization of Guar gum-based solid biopolymer electrolyte doped with lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) plasticized with glycerol

The Guar gum (GG)–lithium bis(trifluoromethanesulphonyl)imide (LiTFSI)-glycerol-based solid biopolymer electrolyte has been investigated. The polymer electrolytes has been prepared via solution casting technique and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), 3D-laser profilometry and AC impedance studies. The amorphous nature and complexation has been revealed by XRD and FTIR. TGA reveals that the polymer electrolyte is stable up to 260°C. The average roughness was measured using 3D-laser profilometry. The ionic conductivity of the electrolyte was studied using impedance analysis. The best optimum ionic conductivity of 2.041 × 10−3 S cm−1 has been achieved for the film containing 60 wt% GG–40 wt% LiTFSI.

Structural, thermal, optical and conductivity studies of Co/ZnO nanoparticles doped CMC polymer for solid state battery applications

In this study, a simple chemical precipitation method was used to synthesize ZnO: Co2+ as nanoparticles. The solution casting technique was used for the preparation of polymer films of Carboxymethyl cellulose (CMC) doped with different contents (0.5, 1.5, 3, and 5 wt%) of ZnO/Co NPs. As shown by the X-ray diffraction, the average size of ZnO/Co crystallite of the NPs is 25.6 nm. Meanwhile, the addition of ZnO/Co reduced the semi-crystallinity of CMC. The Fourier transform infrared (FTIR) confirmed the interaction between the ZnO/Co NPs and the polymer CMC. The direct and indirect band gap (Eg) was reduced from (5.32–5.01 eV and 5.20 to 4.99 eV respectively) with the increase in ZnO/Co NPs content up to 3 wt% after this content the Eg is increased as shown by the UV–Vis spectra. In addition, the results of TGA displayed the decomposition of the nanocomposite to be little compared to that of the pure CMC indicating the success of fabrication of products. The improvement of the ionic conductivity was noticed upon the addition of ZnO/Co NPs into the polymer CMC system which can be explained in terms of an increase in amorphicity as shown by the impedance spectroscopic study. It was found that the optimum ionic conductivity (3.209 × 10−6 Scm−1) at ambient temperature was higher for the sample containing 1.5 wt% ZnO/Co NPs with highest of amorphicity and the lowest total loss of weight. Therefore, the improvements in optical properties, thermal stability, and AC conductivity which were observed represent a strong support for the use of the nanocomposite films in the solid state battery applications.

Redox active polymer metal chelates for use in flexible symmetrical supercapacitors: Cobalt-containing poly(acrylic acid) polymer electrolytes

The novel polymer metal chelate electrolytes (polychelates) were prepared by incorporation of cobalt sulfate (Co) into poly(acrylic acid) (PAA) host matrix. Quasi-solid state supercapacitor devices were fabricated using polychelates, PAA-CoX (X: 3, 5, 7, and 10) where X represents the doping fraction (w/w) of Co in PAA. All polymer metal electrolytes were showed excellent bending-stretching properties, thermal stability and electrochemical durability with an optimum ionic conductivity of 3.15 × 10−4 S cm−1. Hierarchically porous activated carbon and nano-sized conductive carbon were used to form carbon composite symmetrical device electrodes. The electric double-layer capacitor (EDLC) and redox reactions of Co-incorporated polychelates at the interfaces of porous activated carbon provided an optimum specific capacitance of 341.33 F g−1 with a device of PAA-Co7, which is at least 15 times enhancement compared to the device of pristine PAA. The PAA-Co7 device also provided energy density of 21.25 Wh kg−1 at a power density of 117.69 W kg−1. A prolonged cyclic stability of the device exhibited superior capacitive performance after 10,000 charge–discharge cycles and the maintained 90% of its initial performance. In addition, the supercapacitor with a dimension of 1.5 cm × 3 cm containing PAA-Co7 successfully operated the red-blue-green (RGB) LED light.