Polypyrrole Polyethylene Composite for Controllable Linear Actuators in Different Organic Electrolytes

Controllable linear actuation of polypyrrole (PPy) is the envisaged goal where only one ion dominates direction (here anions) in reversible redox cycles. PPy with polyethylene oxide (PEO) doped with dodecylbenzenesulfonate forms PPy-PEO/DBS films (PPy-PEO), which are applied in propylene carbonate (PC) solvent with electrolytes such as 1-ethyl-2,3-dimethylimidazolium trifluoromethanesulfonate (EDMICF3SO3), sodium perchlorate (NaClO4) and tetrabutylammonium hexafluorophosphate (TBAPF6) and compared in their linear actuation properties with pristine PPy/DBS samples. PPy-PEO showed for all applied electrolytes that only expansion at oxidation appeared in cyclic voltammetric studies, while pristine PPy/DBS had mixed-ion actuation in all electrolytes. The electrolyte TBAPF6-PC revealed for PPy-PEO best results with 18% strain (PPy/DBS had 8.5% strain), 2 times better strain rates, 1.8 times higher electronic conductivity, 1.4 times higher charge densities and 1.5 times higher diffusion coefficients in comparison to PPy/DBS. Long-term measurements up to 1000 cycles at 0.1 Hz revealed strain over 4% for PPy-PEO linear actuators, showing that combination of PPy/DBS with PEO gives excellent material for artificial muscle-like applications envisaged for smart textiles and soft robotics. FTIR and Raman spectroscopy confirmed PEO content in PPy. Electrochemical impedance spectroscopy (EIS) of PPy samples revealed 1.3 times higher ion conductivity of PPy-PEO films in PC solvent. Scanning electron microscopy (SEM) was used to investigate morphologies of PPy samples, and EDX spectroscopy was conducted to determine ion contents of oxidized/reduced films.

Novel 3D grid porous Li4Ti5O12 thick electrodes fabricated by 3D printing for high performance lithium-ion batteries

Three-dimensional (3D) grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions (Li-ions), thereby reducing the total transport distance of Li-ions and improving the reaction kinetics. Although there have been other studies focusing on 3D electrodes fabricated by 3D printing, there still exists a gap between electrode design and their electrochemical performance. In this study, we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity, active material particle diameter, electrode electronic conductivity, electrode thickness, line width, and pore size on the electrochemical performance. Both numerical simulations and experimental investigations are conducted to systematically examine these effects. 3D grid porous Li4Ti5O12 (LTO) thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085 µm and areal mass loading of 39.44 mg·cm−2 are obtained. The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm−[email protected] C, areal energy density of 28.95 J·cm−[email protected] C, and areal power density of 8.04 mW·cm−[email protected] C. This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.

High performance silicon electrode enabled by titanicone coating

This paper presents the electrochemical performance and characterization of nano Si electrodes coated with titanicone (TiGL) as an anode for Li ion batteries (LIBs). Atomic layer deposition (ALD) of the metal combined with the molecular layer deposition (MLD) of the organic precursor is used to prepare coated electrodes at different temperatures with improved performance compared to the uncoated Si electrode. Coated electrodes prepared at 150 °C deliver the highest capacity and best current response of 1800 mAh g−1 at 0.1 C and 150 mAh g−1 at 20 C. This represented a substantial improvement compared to the Si baseline which delivers a capacity of 1100 mAh g−1 at 0.1 C but fails to deliver capacity at 20 C. Moreover, the optimized coated electrode shows an outstanding capacity of 1200 mAh g−1 at 1 C for 350 cycles with a capacity retention of 93%. The improved discharge capacity, electrode efficiencies, rate capability and electrochemical stability for the Si-based electrode presented in this manuscript are directly correlated to the optimized TiGL coating layer deposited by the ALD/MLD processes, which enhances lithium kinetics and electronic conductivity as demonstrated by equivalent circuit analysis of low frequency impedance data and conductivity measurements. The coating strategy also stabilizes SEI film formation with better Coulombic efficiencies (CE) and improves long cycling stability by reducing capacity lost.

Investigating a promising iron-doped graphene sensor for SO2 gas: DFT calculations and QTAIM analysis

Examination of a promising iron-doped graphene (FG) sensor for the sulfur oxide (SO2) toxic gas was done in this work at the molecular and atomic scales of density functional theory (DFT). The models were stabilized by performing optimization calculations and their electronic features were evaluated. Two models were obtained by relaxing each of the O or S atoms towards the Fe-doped region of surface. Energy values indicated higher strength for formation of the O@FG model in comparison with the S@FG model. The evaluated quantities and qualities of electronic molecular orbitals indicated the effects of occurrence of adsorption processes on the electronic conductivity property of FG as a required feature of a sensor material. As a consequence, the idea of proposing the investigated FG as a promising sensor of the hazardous SO2 gas was affirmed in this work based on the obtained structural and electronic features.

Anthozoan-like Porous Nanocages with Nano-Cobalt Armed CNTs Multifunctional Layer as Cathode Material for High-stable Na-S Battery

The capacity decay of room-temperature Na-S batteries is mainly caused by the poor electronic conductivity, shuttle effect, and volume expansion of sulfur/polysulfides (NaPSs). Herein, anthozoan-like nitrogen-doped porous carbon nanocages with...

Water as Hole-Predatory Instrumental to Create Metal Nanoparticles on Triple-Conducting Oxides

Single-phase materials with mixed ionic and electronic conductivity underpin multiple solid-state electrochemical devices as promising electrodes. In particular, triple-conducting oxides that carry protons, oxygen ions, and electron holes simultaneously have...

Biaxial Tensile Strain-Induced Enhancement of Thermoelectric Efficiency of α-Phase Se2Te and SeTe2 Monolayers

Thermoelectric (TE) materials can convert waste heat into electrical energy, which has attracted great interest in recent years. In this paper, the effect of biaxial-tensile strain on the electronic properties, lattice thermal conductivity, and thermoelectric performance of α-phase Se2Te and SeTe2 monolayers are calculated based on density-functional theory and the semiclassical Boltzmann theory. The calculated results show that the tensile strain reduces the bandgap because the bond length between atoms enlarges. Moreover, the tensile strain strengthens the scatting rate while it weakens the group velocity and softens the phonon model, leading to lower lattice thermal conductivity kl. Simultaneously, combined with the weakened kl, the tensile strain can also effectively modulate the electronic transport coefficients, such as the electronic conductivity, Seebeck coefficient, and electronic thermal conductivity, to greatly enhance the ZT value. In particular, the maximum n-type doping ZT under 1% and 3% strain increases up to six and five times higher than the corresponding ZT without strain for the Se2Te and SeTe2 monolayers, respectively. Our calculations indicated that the tensile strain can effectively enhance the thermoelectric efficiency of Se2Te and SeTe2 monolayers and they have great potential as TE materials.