3-D microbattery electrolyte by self-assembly of oligomers

This paper reports the preparation and characterization of novel thin film electrolytes by UV cross-linking of poly(propylene glycol) diacrylate in the presence of polyetheramine (glyceryl poly(oxypropylene)triamine) and LiTFSI. The oligomeric surfactant polyetheramine facilitates self-assembly of the electrolyte, enabling it to be applied conformally onto a complex substrate which is necessary for 3D-microbatteries, while the acrylate network supplies mechanical stability. Conformal coatings onto LiFePO₄ electrodes and Cu nanopillars were confirmed by SEM. Ionic conductivities of 3.5 × 10^− 6 and 5.8 × 10^− 5 S/cm were measured at room temperature and 60 °C, respectively, at Li:O = 1:20 and PEA:PPGDA = 2:1 ratios. The electrochemical stability window test showed that the electrolyte is stable above 5.0 V vs. Li/Li⁺. Thermal analyses by TGA and DSC demonstrated that the polymer electrolyte is amorphous and thermally stable up to 300 °C.     

Studies on poly(vinylidene fluoride-co-hexafluoropropylene) based gel electrolyte nanocomposite for sodium-sulfur batteries

Experimental investigations on a sodium ion conducting gel polymer electrolyte nanocomposite based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with silica nanoparticles are reported. The gel nanocomposites have been obtained in the form of dimensionally stable, transparent and free-standing thick films. Physical characterization by X-ray diffraction (XRD), Fourier transform Infra-red (FTIR) spectroscopy and Scanning electron microscopy (SEM) have been performed to study the structural changes and the ion-filler-polymer interactions due to the dispersion of SiO₂ nanoparticles in gel electrolytes. The highest ionic conductivity of the electrolyte has been observed to be 4.1 × 10⁻³ S cm^− 1 at room temperature with ~ 3 wt.% of SiO₂ particles. The temperature dependence of the ionic conductivity has been found to be consistent with Vogel-Tammen-Fulcher (VTF) relationship in the temperature range from 40 to 70 °C. The sodium ion conduction in the gel electrolyte film is confirmed from the cyclic voltammetry, impedance analysis and transport number measurements. The value of sodium ion transport number (t_Na+) of the gel electrolyte is significantly enhanced to a maximum value of 0.52 on the 15 wt.% SiO₂ dispersion. The physical and electrochemical analyses indicate the suitability of the gel electrolyte films in the sodium batteries. A prototype sodium-sulfur battery, fabricated using optimized gel electrolyte, offers the first discharge capacity of ~165 mAh g^− 1 of sulfur.     

Ionic conductivity and electrochemical stability of poly(methylmethacrylate)-poly(ethylene oxide) blend-ceramic fillers composites

The role of inorganic ceramic fillers namely nanosized Al₂O₃ (15-25 nm) and TiO₂ (10-14 nm) and ferroelectric filler SrBi₄Ti₄O₁₅ (SBT CIT) (0.5 μm) synthesized by citrate gel technique (CIT) on the ionic conductivity and electrochemical properties of polymer blend 15 wt% PMMA+PEO₈:LiClO₄+2 wt% EC/PC electrolytes were investigated. Enhancement in conductivity was obtained with a maximum of 0.72×10⁻⁵ S cm⁻¹ at 21 °C for 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) composite polymer electrolyte. The lithium-ion transport number and the electrochemical stability of the composite polymer electrolytes at ambient temperature were analyzed. An enhancement in electrochemical stability was observed for polymer composites containing 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) as fillers.     

Preparation and properties of a gel polymer electrolyte system based on poly-ε-caprolactone containing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Gel polymer electrolytes (GPE) obtained by immobilizing a solution of zinc triflate (ZnTr) in an ionic liquid, namely 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [emim][Tf₂N] within a biodegradable polymeric matrix of poly-ε-caprolactone (PCL) were prepared by a simple solvent cast technique for different concentrations of the ionic liquid. The electrolyte with the composition 75 wt% PCL: 25 wt% ZnTr+100 wt% [emim][Tf₂N] showed the highest ionic conductivity of 1.1×10⁻⁴ S cm⁻¹ at 25 °C and favored by the rich amorphous phase of the GPE as confirmed from room temperature X-ray diffraction analysis (XRD). The morphology of the GPE was examined using scanning electron microscopy (SEM) which revealed the homogeneity of the prepared GPE system. The temperature dependence of electrical conductivity of the GPE followed the Arrhenius behavior. The Zn²⁺ ionic transport number has been determined to be ~0.62 which denotes the predominant contribution of zinc ion towards total ionic conductivity. The electrochemical stability window of GPE is found to be 2.5 V with a thermal stability upto 200 °C. This eco-friendly and safe electrolyte may be used to fabricate compostable batteries, in future, with a suitable selection of other components of the battery system.     

Lithium ion transport and ion-polymer interaction in PEO based polymer electrolyte plasticized with ionic liquid

The polyethylene oxide (PEO) based lithium ion conducting polymer electrolytes complexed with lithium trifluoromethanesulfonate (LiCF₃SO₃ or LiTf) plasticized with an ionic liquid 1-ethyl 3-methyl imidazolium trifluoromethanesulfonate (EMITf) have been reported. Morphological, spectroscopic, thermal and electrochemical investigations demonstrate promising characteristics of the polymer films, suitable as electrolyte in various energy storage/conversion devices. Significant structural changes have been observed in the polymer electrolyte due to the ionic liquid addition, investigated by X-ray diffraction (XRD) and optical microscopy. The ion-polymer interaction, particularly the interaction of imidazolium cation with PEO chains, has been evidenced by IR and Raman spectroscopic studies. The optimized composition of the polymer electrolyte i.e. PEO_25.LiTf + 40 wt.% EMITf offer room temperature ionic conductivity of ~ 3 × 10^− 4 S cm^− 1 with wide electrochemical stability window and excellent thermal stability. The ‘σ versus 1/T’ curves show apparent Arrhenius behavior below and above melting temperature. The ionic conductivity has been observed due to Li⁺ ions, as confirmed from ⁷Li-NMR studies, though the component ions of ionic liquid and anions also contribute significantly to the overall conductivity.     

CuO-PAA hybrid films: Chemical synthesis and supercapacitor behavior

We report the synthesis of CuO-Poly (acrylic) acid (PAA) hybrid thin films by a cost-effective spin coating technique for supercapacitor application. Coated films were annealed at 300, 400 and 500 °C, to study the annealing effect on the supercapacitor behavior. Further films were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform-Raman spectroscopy (FT-Raman) and Fourier transform-Infrared spectroscopy (FT-IR) techniques. Energy dispersive spectroscopy (EDS) shows the formation of amorphous blend of CuO and Cu₂O phases at 300 °C. Further, films annealed at 400 and 500 °C exhibit polycrystalline phase pure CuO with monoclinic structure. The scanning electron microscopy (SEM) micrographs show the transition of island-like structure to CuO crystals surrounded by PAA grafted composite ring with increase in annealing temperature. The possible growth mechanism of PAA and CuO bonding is discussed. Cyclic voltammetry (CV) is employed to calculate the specific capacitance (C_sp) in 1 M H₂SO₄ electrolyte. It is observed that the C_sp increases from 41 to136 F g⁻¹ with increase in annealing temperature.     

Electrochemical synthesis of ammonia based on doped-ceria-carbonate composite electrolyte and perovskite cathode

Electrochemical synthesis of ammonia was investigated using a cobalt-free La_0.6Sr_0.4Fe_0.8Cu_0.2O_3-δ-Ce_0.8Sm_0.2O_2-δ (LSFCu-SDC) composite cathode and SDC-ternary carbonate composite electrolyte. La_0.6Sr_0.4Fe_0.8Cu_0.2O_3-δ and Ce_0.8Sm_0.2O_2-δ were prepared via combined EDTA-citrate complexing sol-gel and glycine nitrate processes, respectively, and characterised by X-ray diffraction (XRD). Ammonia was successfully synthesised from wet hydrogen and dry nitrogen under atmospheric pressure using Ni-SDC, SDC-carbonate and LSFCu-SDC composites as anode, electrolyte and cathode respectively. Ammonia formation was observed at 400, 425, 450 and 475 °C and the maximum rate of ammonia production was found to be 5.39 × 10⁻⁹ mol s⁻¹ cm⁻² at 450 °C and 0.8 V. The AC impedance measurements were recorded before and after the ammonia synthesis in the range of temperature 400-475 °C. The formation of ammonia at the N₂ side together with stable current at 450 °C under constant voltage demonstrates that SDC-(Li/Na/K)₂CO₃ composite electrolyte exhibits significant proton conduction at a temperature around 450 °C.     

An investigation on PAN-PVC-LiTFSI based polymer electrolytes system

Polymer-salt complex with poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) as host polymers blended with lithium bis-(trifluoro methanesulfonyl)imide, LiTFSI [LiN(CF₃SO₂)₂] as dopant salt were prepared in the form of thin film. Fourier transform infrared (FTIR) studies show the evidence of the complexation between PVC, PAN and LiTFSI. Ionic conductivity studies reveal that polymer electrolyte with 30 wt.% LiTFSI has the highest ionic conductivity of 4.39 × 10^− 4 S/cm at room temperature. The polymer electrolytes are also found to be stable up to 315 °C before they decompose. Thermal stability of the polymer electrolytes was also found to increase with increase in salt content. This was proven through thermogravimetric studies.     

Characterization of nanocomposite polymer electrolyte based on P(ECH-EO)

ZrO₂ nanoparticles have been prepared by poly acrylamide gel route. The synthesized nanosized ZrO₂ have been incorporated into plasticized polymer electrolyte (PPE), P(ECH-EO): LiClO₄: γ-BL system to understand the effect of ZrO₂ on the ionic conductivity. The X-ray diffraction pattern of the synthesized ZrO₂ nanoparticles reveals the crystalline phase. The X-ray diffraction patterns of P(ECH-EO) based NCPEM confirm the polymer-salt-nanoparticle complexation. The scanning electron microscope image of NCPEM confirms that the ZrO₂ nanoparticles were distributed uniformly in the polymer matrix. The presence of nano filler has increased the ionic conductivity and the maximum dc conductivity value is found to be 6.24×10⁻⁶ S cm⁻¹ at 303 K for 96(PPE): 4ZrO₂ (mol%).     

Sinteractivity, proton conductivity and chemical stability of BaZr0.7In0.3O3-δ for solid oxide fuel cells (SOFCs)

In³⁺ was used as dopant for BaZrO₃ proton conductor and 30 at%-doped BaZrO₃ samples (BaZr_0.7In_0.3O_3-δ, BZI) were prepared as electrolyte materials for proton-conducting solid oxide fuel cells (SOFCs). The BZI material showed a much improved sinteractivity compared with the conventional Y-doped BaZrO₃. The BZI pellets reached almost full density after sintering at 1600 °C for 10 h, whereas the Y-doped BaZrO₃ samples still remained porous under the same sintering conditions. The conductivity measurements indicated that BZI pellets showed smaller bulk but improved grain boundary proton conductivity, when compared with Y-doped BaZrO₃ samples. A total proton conductivity of 1.7 × 10⁻³ S cm⁻¹ was obtained for the BZI sample at 700 °C in wet 10% H₂ atmosphere. The BZI electrolyte material also showed adequate chemical stability against CO₂ and H₂O, which is promising for application in fuel cells.     

Fabrication of p-type Li-doped ZnO films by pulsed laser deposition

p-Type ZnO thin films have been realized via doping Li as acceptor by using pulsed laser deposition. In our experiment, Li₂CO₃ was used as Li precursor, and the growth temperature was varied from 400 to 600 °C in pure O₂ ambient. The Li-doped ZnO film prepared at 450 °C possessed the lowest resistivity of 34 Ω cm with a Hall mobility of 0.134 cm² V⁻¹ s⁻¹ and hole concentration of 1.37 × 10¹⁸ cm⁻³. X-ray diffraction (XRD) measurements showed that the Li-doped ZnO films grown at different substrate temperatures were of completely (0 0 2)-preferred orientation.     

The electrodeposition behaviors and magnetic properties of Ni-Co films

Ni-Co films with different compositions and microstructures were produced on ITO glasses by electrodeposition from sulphate bath at 25 °C. Cyclic voltammograms give a result that the increase in the Co²⁺ concentration displaces Ni-Co alloy oxidation peaks to negative potential with high Co current distributions. It is observed that the content of cobalt in the films increases from 22.42% to 56.09% as the molar ratio of CoSO₄/NiSO₄ varying from 0.015/0.085 to 0.045/0.055 in electrolyte. XRD patterns reveal that the structure of the films strongly depends on the Co content in the deposited films. The saturation magnetization (M_s) moves up from 144.84 kA m⁻¹ to 342.35 kA m⁻¹ and coercivity (H_c) falls from 15.27 kA m⁻¹ to 7.27 kA m⁻¹ with the heat treatment temperature increasing from 25 °C to 450 °C. The saturation magnetization (M_s) and coercivity (H_c) move up from 340.97 kA m⁻¹ and 7.98 kA m⁻¹ to 971.58 kA m⁻¹ and 18.62 kA m⁻¹ with the Co content increasing from 22.42% to 56.09% after annealing at 450.     

ZrB2-based Ohmic contacts to p-GaN

The annealing temperature dependence of contact resistance and layer stability of ZrB₂/Ti/Au and Ni/Au/ZrB₂/Ti/Au Ohmic contacts on p-GaN is reported. The as-deposited contacts are rectifying and transition to Ohmic behavior for annealing at ≥750 °C, a significant improvement in thermal stability compared to the conventional Ni/Au Ohmic contact on p-GaN, which is stable only to <600 °C. A minimum specific contact resistance of ∼2 × 10⁻³ Ω cm⁻² was obtained for the ZrB₂/Ti/Au after annealing at 800 °C while for Ni/Au/ZrB₂/Ti/Au the minimum value was 10⁻⁴ Ω cm⁻² at 900 °C. Auger Electron Spectroscopy profiling showed significant Ti, Ni and Zr out diffusion at 750 °C in the Ni/Au/ZrB₂/Ti/Au while the Ti and Zr intermix at 900 °C in the ZrB₂/Ti/Au. These boride-based contacts show promise for contacts to p-GaN in high temperature applications.     

Local chemical transformations in poly(dimethylsiloxane) by irradiation with 248 and 266 nm

Poly(dimethylsiloxane) (PDMS) has been irradiated with a frequency quadrupled Nd:YAG laser and a KrF^*-excimer laser at a repetition rate of 1 Hz. The analysis of ablation depth versus pulse number data reveals a pronounced incubation behavior. The thresholds of ablation (266 nm: 210 mJ cm⁻², 248 nm: 940 mJ cm⁻²) and the corresponding effective absorption coefficients α_eff (266 nm: 48900 cm⁻¹, 248 nm: 32700 cm⁻¹, α_lin = 2 cm⁻¹) were determined. The significant differences in the ablation thresholds for both irradiation wavelengths are probably due to the different pulse lengths of both lasers. Since the shorter pulse length yields a lower ablation threshold, the observed incubation can be due to a thermally induced and/or a multi-photon absorption processes of the material or impurities in the polymer.Incubation of polymers is normally related to changes of the chemical structure of the polymer. In the case of PDMS, incubation is associated with local chemical transformations up to several hundred micrometers below the polymer surface. It is possible to study these local chemical transformations by confocal Raman microscopy, because PDMS is transparent in the visible. The domains of transformation consist of carbon and silicon, as indicated by the appearance of the carbon D- and G-bands between 1310 and 1610 cm⁻¹, a band appearing between 502 and 520 cm⁻¹ can be assigned to mono- and/or polycrystalline silicon.The ablation products, which are detected in the surroundings of the ablation crater consist of carbon and amorphous SiO_x (x ≈ 1.5) as detected by infrared spectroscopy.     

Local vibration assisted molecular configurations in poly(vinylidene fluoride) of ordered ferroelectric phase in N,N-dimethylformamide

Amide-based polymer liquids are important for developing biological and optical colloids or nanofluids. Functionalized properties arise from specific molecular structures. In this investigation, we report model molecular configurations of a polymer liquid, 0.3 g/L poly(vinylidene fluoride) (PVF₂) dissolved in liquid N,N-dimethylformamide (DMF), based on the characteristic IR vibration bands. Peculiarly, a ferroelectric β-PVF₂ phase reorders on a linear configuration in support with the DMF molecules, showing a characteristic band 840 cm^− 1 (CH₂ rocking and CF₂ asymmetric stretching) with the trans band at 1275 cm^− 1. Four CO stretching bands ν₁⁰, ν₁¹, ν₁², and ν₁³ of 1650, 1675, 1725, and 1760 cm^− 1 (bandwidth Δν_½ = 180 cm^− 1 in the four bands) arise in four major configurations of DMF-PVF₂ pairs (or derivatives). Only one prominent ν₁⁰ band 1660 cm^− 1 (Δν_½ = 75 cm^− 1) incurs with a shoulder ν₁¹ of 1725 cm^− 1 (Δν_½ = 25 cm^− 1) in two DMF configurations. A ferroelectric field cased in presence of β-PVF₂ leads to enhance IR absorption by as much as an order of magnitude. It leads to converging non-bonding electron density on the amide moiety.     

Preparation of alkaline solid polymer electrolyte based on PVA-TiO2-KOH-H2O and its performance in Zn-Ni battery

A novel composite alkaline polymer electrolyte based on poly(vinyl alcohol) (PVA) polymer matrix, titanium dioxide (TiO₂) ceramic fillers, KOH, and H₂O was prepared by a solution casting method. The properties of PVA-TiO₂-KOH alkaline polymer electrolyte films were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and AC impedance techniques. DSC and XRD results showed that the domain of amorphous region in the PVA polymer matrix augmented when TiO₂ filler was added. The SEM result showed that TiO₂ particles dispersed into the PVA matrix although some TiO₂ aggregates of several micrometers were formed. The alkaline polymer electrolyte showed excellent electrochemical properties. The room temperature (20 °C) ionic conductivity values of typical samples were between 0.102 and 0.171 S cm⁻¹. The Zn-Ni secondary battery with the alkaline polymer electrolyte PVA-TiO₂-KOH had excellent electrochemical property at the low charge-discharge rate.     

A novel method to synthesize LiVPO4F/C composite materials and its electrochemical Li-intercalation performances

Triclinic LiVPO₄F/C composite materials were prepared from a sucrose-containing precursor by one-step heat treatment. As-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that Li₃PO₄ impurity phase appeared in the sample synthesized at 600 °C and pure LiVPO₄F samples could be obtained when the sintered temperature was higher than 650 °C. The sample synthesized at 650 °C presents the highest initial discharge capacity of 132 mAh g⁻¹ at 0.2 C rate, and exhibited better cycling stability (124 mAh g⁻¹ at 50th cycle at 0.2 C rate) and better rate capability (100 mAh g⁻¹ at 50th cycle under 1 C rate) in the voltage range 3.0-4.4 V.     

Effect of hot pressing on the ionic conductivity of the PEO/LiCF3SO3 based electrolyte membranes

PEO/LiCF₃SO₃ (LiTFS) /Ethylene carbonate (EC) polymer electrolyte membranes were prepared with a solution casting method followed by a hot pressing process. The effect of the hot pressing process on the in-plane conductivity of the PEO electrolyte membranes was evaluated using a four-electrode AC impedance method. The composition, morphology, and microstructure of the composite polymer electrolyte were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The AC impedance measurement results indicate that the hot pressing process can increase the room temperature conductivity of the membranes 14 times to 1.7 × 10^− 3 S cm^− 1 depending upon the duration of the hot pressing process. The SEM, FTIR, XRD, and DSC results indicate that the hot pressing process could increase the amorphous part of the polymer electrolyte membrane or convert large spherulite crystals into nano-sized crystals.     

Characterization of YSr2Fe3O8 − δ as electrode materials for SOFC

YSr₂Fe₃O_8 − δ was prepared by traditional solid state reaction method and characterized by X-ray diffraction, ac impedance, dc conductivity, dilatometry and thermogravimetric analysis for possible use in solid oxide fuel cells (SOFCs). YSr₂Fe₃O_8 − δ crystallizes with tetragonal symmetry in the space group P4/mmm and found to be stable at high temperatures under H₂ and air. Four probe dc electrical conductivity measurements show that the conductivity increases up to 745 K and then decreases with temperature; the highest conductivity σ_745K = 43.5 S cm^− 1. The n-type conductivity at low oxygen partial pressure (pO₂) changes to p-type at high pO₂. Polarization behavior was investigated measuring the ac impedance response in symmetrical cell arrangements in air with YSZ and GDC electrolytes. Cathodic area specific resistance (ASR) varies with firing temperature. The lowest area specific resistance was observed with a GDC electrolyte fired at 1000 °C. In case of YSZ, ASR increases and in case of GDC, ASR decreases in air when electrode firing temperature decreases. At 800 °C ASRs are 0.20 Ω cm² and 0.65 Ω cm² with GDC and YSZ electrolytes, respectively, in air. Fuel cell measurements with symmetrical electrodes were performed using a thin YSZ electrolyte under H₂ at anode and air at cathode, show that the power density is about 0.035 W/cm² at 900 °C.