Capacitive Properties Research Articles

Novel Methodology of General Scaling-Approach Normalization of Impedance Parameters of Insertion Battery Electrodes – Case Study on Ni-Rich NMC Cathode: Part II. Detailed Analysis Using a Transmission Line Model

Abstract Here, we extend the general approach shown in PART-1 to a detailed analysis of the measured data using our previously published physics-based transmission line model (TLM). We construct general relationships between the TLM parameters and the electrode mass. We then systematically check the scaling properties of all model parameters by fitting the measured impedance responses of 8 NMC-NMC cells with different masses (thicknesses) of NMC cathodes ranging from 2.3 to 58.5 mg per 2 cm2 of geometric electrode surface. We consider in detail all deviations of the measured spectra from the idealized spectra predicted by the model. Among other things, we discuss the high-frequency inductive effects, the ambiguities in the analysis of the low-frequency diffusion phenomena, and the effects of non-ideal capacitive properties (the so-called constant-phase elements) on the shape of the measured spectra. We also report an unexpected additional feature observed in measurements on thin (light) electrodes: a diffusion arc due to the diffusion of lithium in the electrolyte in the micropores of the NMC aggregates in the material used. Finally, we present a detailed dependence of all model parameters on the mass (thickness) of the electrode and discuss the potential practical significance of such an analysis.

Synthesis of biochar and its metal oxide composites and application on next sustainable electrodes for energy storage devices

Biochar materials have been applied in energy storage due to their unique properties, such as high storage of ions, high conductivity, chemical stability and ease of production. Combining it with the high specific capacitance could be a promising strategy to develop devices and improve the properties. Through a hydrothermal technique the biochar powders were synthesized from sugarcane biomass. An acid pretreatment was carried out before and after the graphitization process aiming to obtain carbon materials with high surface area and porosity. The morphological characterization reveals powders with pores of submicrometer diameter. For the pure biochar it was determined a superficial area of 477.66 m2.g−1 with a median pore size of 42.92 Å and a pore volume of 0.21 cm3.g−1. A carbon-based paste was then prepared to deposit on nickel foam and obtain the electrodes. In a 3-electrode system characterization, biochar has showed higher specific capacitance than the metal oxide composites due to higher surface area and higher medium pore diameter. It was calculated a resistance of 2.7 Ω, a capacitance of 446 mF.g−1, a power density of 46.2 W.kg−1 and an energy density of 1.8 W.h.kg−1. These results indicate the potential use of biochar-based electrodes with high electrical conductivity and improved surface area to obtain higher capacitance properties for development of advanced devices.

Significantly improve capacitive properties of alicyclic polyimide dielectrics at high temperatures via hard/soft segment engineering

The demand for high energy storage density and efficiency of polymer film capacitors at high temperatures is urgently increasing in the electronics and electrical field. However, most traditional high temperature resistant polymers exhibit the low bandgap and high conductive loss because of the presence of conjugated aromatic structures, resulting in a significant decrease in the energy storage performance at high temperatures and high fields. In this paper, a series of alicyclic polyimide dielectric films containing hard segment of phenyl imide and soft segment of cyclohexyl imide are designed and prepared. On the one hand, the introduction of non-coplanar alicyclic ring into main-chain of polyimide can break long distance conjugation effect, weaken the intermolecular and intramolecular charge transfer interaction and improve the bandgap. On the other hand, the physical crossing point formed by the soft segments can sharply increase Young's modulus of the polyimide films. As a result, the terpolymer polyimide film (CPI90) with copolymerization ratio of phenyl/cyclohexyl dianhydride of 9:1 achieves a highest discharge energy density (Ud) of 5.59 J cm−3 at 150 °C. Importantly, the CPI90 film can obtain the Ud of 2.74 J cm−3 at 200 °C. In addition, the CPI90 film possesses a good self-healing ability attributing to a small ratio for the carbon to hydrogen and oxygen. This work offers a new strategy for synergistically promoting the bandgap and Young's modulus of polymer dielectrics via molecular and hard/soft segment engineering.

Enhanced electrochemical energy storage of binder-free ternary copper manganese selenide nanocomposite electrodes via polydopamine coating for quasi-solid-state hybrid supercapacitors

Owing to promising reliability, high energy storage capability, good stability, etc., nanostructured bimetallic selenides have attracted widespread interest in establishing supercapacitor devices with auspicious electrochemical properties. Focusing on this, herein, we proposed a novel polydopamine (PDA)-coated nanostructured copper manganese selenide (CuMn2Se4) on nickel foam via a hydrothermal method. The chemical composition of the cathode electrode was modified according to the chemical formula of CuxMn2-xSe4 (x = 0, 0.5, and 1) (CMS), and its effect on electrochemical properties as well as on surface morphology was investigated. The optimized CMS electrode exhibited an evenly spread petal-like lawn structure, offering rapid electron/ion kinetics, which results in improved capacitive properties. Furthermore, PDA as a redox-active neurotransmitter was evenly coated on the optimized CMS (i.e., PDA@CMS) to increase electron availability, thus enhancing energy storage capacity. The PDA@CMS electrode showed a superior specific capacitance of 3140 F g−1 at 3 A g−1 of current density. The quasi-solid-state hybrid supercapacitor was fabricated using PDA@CMS as a positive electrode and radish-derived carbon as a negative electrode with gel-type electrolyte, which delivered the power and energy densities of 7750 W kg−1 and 21.85 Wh kg−1, respectively with superior cycling stability (96.5 % capacitance retention over 10,000 cycles).

Revealing the Surface and In-Depth Operational Performances of Oxygen-Evolving Anode Coatings: A Guideline for the Synthesis of Inert Durable Anodes in Metal Electrowinning from Acid Solutions

The electrochemical performances of an oxygen-evolving anode produced by the reactivation of waste Ti substrate by a typical IrO2-Ta2O5 coating are correlated to the textural (non)uniformities of the coating and its exhaustion state. Coating degradation is considered operational loss of the activity in a metal electrowinning process. It was found that (pseudo)capacitive performances can vary over the coating surface by 20–30% and depend on the type of dynamics of the input perturbation: constant through cyclic voltammetry (CV) or discontinuous time-dependent through electrochemical impedance spectroscopy (EIS). CV-EIS data correlation enabled profiling of the capacitive properties through the depth of a coating and over its surface. The correlation was confirmed by the findings for the analysis of coating activity for an oxygen evolution reaction, finally resulting in the reliable proposition of a mechanism for the operational loss of the anode. It was found that the less compact and thicker coating parts performed better and operated more efficiently, especially at lower operational current densities.

Frequency-dependent and capacitive tissue electrical properties in spinal cord stimulation models.

Models of spinal cord stimulation (SCS) simulate the electric fields (E-fields) generated in targeted tissues, which in turn can predict physiological and then behavioral outcomes. Notwithstanding increasing sophistication and use in optimizing therapy, SCS models typically calculate E-fields using the quasi-static approximation (QSA). QSA, as implemented in neuromodulation models, neglects the frequency dispersion of tissue conductivity, as well as propagation, capacitive, and inductive effects on the E-field. The reliability of QSA specifically for SCS has not been considered in detail, especially for higher-frequency SCS. We implemented a frequency-dependent finite element method (FEM) and solved a high- resolution RADO-SCS model with voltage-controlled (VC) and current-controlled (CC) stimulation to assess the impact of frequency-dependent conductivity (dispersion) and permittivity of spinal tissues on E-fields generated at three different spinal column locations (epidural space, spinal cord, and root) for frequencies spanning from 1 Hz to 10 MHz. Results were compared with predictions of QSA method, with varied conductivity values of purely resistive tissues. We further assessed the impact of frequency-dependent and capacitive tissue properties on spinal heating and distortion of the E-field waveform. Tissue-specific electric properties around the energized leads and mode of stimulation-control impacted the magnitude of E-fields. In the spinal cord, the VC-SCS E-field generated with the frequency-dependent and capacitive properties was comparable to the QSA with 2X epidural fat conductivity, whereas the CC-SCS generated E-field was minimally impacted by frequency- dependent and capacitive properties up to 10 kHz. Spinal cord heating predicted by frequency- dependent and capacitive tissue properties was comparable to the QSA conditions with VC-SCS, whereas with CC-SCS, there was no impact of the frequency-dependent and capacitive tissue properties in spinal cord heating. E-field waveform distortion in the spinal cord, with CC-SCS at 1 kHz-specific electrical properties, was significant when fat capacitance (permittivity) was increased by 10X, whereas with VC-SCS, there was no effect of tissue capacitance. Regardless of the mode of SCS, QSA was still valid in predicting SCS-induced E-field and heating at the spinal tissues- across α and β dispersion region of spinal tissue's dielectric spectrum for VC-SCS and up to 10 kHz for CC-SCS.

Controlled Hierarchical Construction of Ultrahomogeneous Co9S8@CoAl-LDH/NF Layered Core-Shell Heterostructures for High-Performance Asymmetric Supercapacitors.

The rational collocation and construction of multiphase composite electrode materials with ingenious structures is a key strategic to enhance the electrochemical performance of supercapacitors (SCs). Within this project, a unique Co9S8@CoAl-LDH/NF core-shell heterostructure consisting of CoAl-LDH/NF ultrathin nanosheets sturdily attached to Co9S8/NF needle-like nanorods is grown in situ on self-supported conductive substrate nickel foam (NF) by an effortless and productive multistep hydrothermal method. The construction of the core-shell structure can effectively enhance the capacitive properties as well as the mechanical strength of the material. Compared with the single-component materials Co9S8/NF (1769.6 mF cm-2 and 91.6%) and CoAl-LDH/NF (858 mF cm-2 and 85.2%), the Co9S8@CoAl-LDH/NF composites have excellent capacitance properties (5052.4 mF cm-2) along with exceptional capacitance retention (5000 cycles) 98.5% even after undergoing charging and discharging. Furthermore, the asymmetric SCs fabricated with Co9S8@CoAl-LDH/NF and AC/NF exhibit an energy density of 0.17 mWh cm-2 at 3.20 mW cm-2. Therefore, the innovative core-shell heterostructure of Co9S8@CoAl-LDH/NF presented in this study holds immense practical potential as a groundbreaking electrode material in the realm of SCs.

Nickel foam supported CuO/Co3O4/r-GO is used as electrode material for non-enzymatic glucose sensors and high performance supercapacitors

In order to solve the problem of glucose detection in medical development and meet the urgent demand for new energy storage devices, this paper proposes a new material suitable for glucose sensing and capacitive properties. The sensor was fabricated by depositing Co3O4 nanoparticles onto nickel foam with integrated r-GO via the hydrothermal method, followed by the synthesis of CuO nanoparticles using electroplating. The detection range of the sensor is 0.3–11.3 mM. The sensor's sensitivity is 1000.3 μA mM−1 cm−2, indicating its responsiveness to changes in analyte concentration. In electrochemical test systems, Signal-to-Noise Ratio (SNR) usually represents the relative intensity of the effective current signal and the background noise, reflecting the accuracy and reliability of the measurement. When the SNR is three, the minimum detection limit is 0.431 μM, highlighting its ability to reliably detect analytes at low concentrations amidst background noise. According to electrochemical workstation tests, the sensor demonstrates robust stability. Furthermore, the electrode material proves suitable for asymmetric supercapacitor devices, when the current density is 2 Ag−1, the specific capacitance is 660.5 Fg−1. At the same time, we also explore the cyclic stability of the device, which can retain 92.3 % of its initial specific capacitance after 5000 cycles, showing its remarkable long-term stability. In addition, the prepared nanocomposites can also light the red LED light. The results show that the synthesized CuO/Co3O4/r-GO/NF electrode can be used for electrochemical glucose sensing and supercapacitors, and plays an important role as a multi-functional material in the fields of medical, food, electronics, transportation and energy, providing key technical support for a variety of applications.

Effect of EDOT contribution on the electrochromic and capacitive properties of edot-carbazole based electrochromic polymer: Electrochromic and supercapacitor device applications

3,4-ethylenedioxythiophene (EDOT) based donor-acceptor-donor (DAD) type conjugated polymers generally have extraordinary electrochromic properties due to the excellent nature of the EDOT unit. This work investigates the electrochromic properties of such a system; EDOT-Carbazole-EDOT (ECE) based DAD type of conjugated polymer. Electrochemically synthesized homopolymer film (PECE) showed multichromic behavior with excellent optical properties such as 34 % of optical contrast, subsecond switching response (0.96 s at 478 nm), high coloration efficiency (519 cm2/C at 478 nm) and remarkable specific capacitance (3.04 F/cm2). Inserting more EDOT units into the polymer matrix of PECE via electrochemical synthesis altered the spectral and capacitive behaviors of the resulting copolymers. 2:1 (ECE:EDOT) feeded copolymer exhibited better electrochromic performance than equal feeded copolymer. On the other hand, the capacitive range and capacitance stability were significantly enhanced as the EDOT unit increased in the copolymer matrix.PECE and its copolymers were used to construct dual-type electrochromic devices with poly(3, 4-ethylenedioxythiophene) (PEDOT). ECDs of PECE and copolymers exhibited superior stability upon many switchings, with subsecond switching responses. Furthermore, ECDs can be switched effectively even at the scan rate of 500 mV/s without any loss in charge/discharge amounts. Finally, electrochromic supercapacitor device applications were performed, and a 1.5 V-LED was lighted for up to 25 s with the copolymer supercapacitor device.

Progress in MOFs and MOFs-Integrated MXenes as Electrode Modifiers for Energy Storage and Electrochemical Sensing Applications.

The global energy demand and environmental pollution are the two major challenges of the present scenario. Recently, researchers focused on the preparation and investigation of catalysts for their capacitive properties for energy storage devices. Thus, supercapacitors have received extensive interest from researchers due to their promising energy storage features and decent cyclic stability/performance. The performance of the supercapacitors are significantly influenced by the physicochemical properties of the electrocatalyst. In this review article, we have compiled the previous reports on the fabrication of MOFs-based composite materials with MXenes for energy storage and electrochemical sensing applications. The metallic and bimetallic MOFs and MOFs/MXenes materials for supercapacitor applications are reviewed. In addition, MOFs/MXenes-based hybrid composites are also compiled towards the determination of various toxic/hazardous materials, such as metal ions like copper ions, mercury ions, and picric acid. We believe that present review article may benefit the researchers working on the preparation of MOFs-based catalysts for supercapacitor and electrochemical sensing applications.

Chitosan-Based Electronics: The Importance of Acid Strength and Plasticizing Additives on Device Performance.

A rise in demand for disposable consumer electronics such as smart packaging, wearable electronics, and single-use point-of-source sensors requires the development of eco-friendly and compostable electronic materials. Chitosan is derived from crustacean waste and offers high dielectric constant values without requiring rigorous purification, making it sustainable for large-scale electronic device manufacturing. When processed in acidic media, the protonated backbone of chitosan pairs with counterions from the acid dissociation to form chitosan thin films with electrical double layers (EDLs) and tunable capacitive properties. We report the importance of the choice of acid when processing chitosan by surveying a series of halogenated and biosourced acids with varying pKa values and solutions with different pH values. Oxalic acid outperforms other acids, with a maximum areal capacitance of 161 nF·mm-2. Tartaric acid and citric acid, despite lower capacitance values, showed promising results with a stable EDL capacitance and high reproducibility, making them optimal for large-area manufacturing. The incorporation of sorbitol as a plasticizer boosts the EDL formation onset of all chitosan-acid combinations to 1 × 103-105 Hz and improves reproducibility. High-performing single-walled carbon nanotube thin film transistors were made using chitosan-based dielectrics treated with different acids with and without sorbitol, leading to transconductance as high as ≈5.2 μS and Ion/Ioff of 105. The capacitors and transistors remain functional after one year of storage in ambient conditions. Overall, this study demonstrates durable high-performance electronics based on chitosan and stresses the importance of processing acid and the use of plasticizing additives, such as sorbitol.

Tuning properties of binary functionalization of Sc2C MXenes for supercapacitor electrodes

Surface functionalization of two-dimensional (2D) materials like Sc2C MXenes offers a promising avenue for tailoring their properties for various applications. At the same time, significant research has focused on pure terminations involving oxygen (-O), fluorine (-F), or hydroxyl (-OH) groups. Binary surface functionalization still needs to be explored. Our work addresses this gap by investigating binary functionalized Sc2C monolayers, specifically Sc2CFN and Sc2COS. Using first-principles calculations, we explore the structural, electronic, and quantum capacitance (CQ) properties of pristine Sc2C and functionalized Sc2CFN and Sc2COS. The CQ measurements reveal distinctive electronic behaviour, with Sc2CFN and Sc2COS exhibiting indirect bandgaps of 0.90 and 1.48 eV, respectively. Introducing functional groups induces a metal-to-semiconductor transition, enhancing charge storage at the cathode and increasing the CQ to 371.64 and 341.23 μF/cm2 for Sc2CFN and Sc2COS, respectively. As far as energy applications are concerned, we also calculate the Shockley-Queisser (SQ) efficiency, which is a widely accepted quantity to get an estimate of the photovoltaic efficiency of 28.77 % for Sc2CFN and 32.97 % for Sc2COS materials. Additionally, we analyze the current-voltage (IV) characteristics, uncovering negative differential conductance (NDC) effects in Sc2COS, indicative of its potential for fast molecular switching applications. Our study provides valuable insights into the properties of binary functionalized Sc2C MXenes, paving the way for their utilization in energy storage and nanoelectronic devices.

Evaluating the effect of A- and B-site cobalt doping on the structural, morphological, dielectric, and non-ohmic properties of CaCu3Ti4O12 ceramics prepared by the hydrothermal method

CaCu3Ti4O12 (CCTO), CaCu3-xCoxTi4O12 (CCCxTO) and CaCu3Ti4-xCoxO12 (CCTCxO) ceramics with x = 0.1 were synthesized by the hydrothermal process at 200 °C for 24 h. The influence of cobalt substitution on the copper and titanium sites in CaCu3Ti4O12 on the structural, morphological, and physical properties was investigated. It was shown through the analysis of X-ray diffractograms of CCTO, CCCxTO, and CCTCxO compounds that they crystallized in a pure perovskite structure without the presence of secondary phases. The refinement of the spectra using the Rietveld method showed an efficient formation of the crystalline phase of the cubic structure (Im3¯), which remains unchanged, with an increase in the unit cell due to the substitution of Co2+/Co3+ in the Cu2+ and Ti4+ sites of the CCTO ceramic. Raman spectroscopy was used as a complementary characterization method to XRD in order to detect vibrational bands and highlight any changes in the crystal lattice. SEM results showed that cobalt insertion increased the average grain size. The dielectric properties were studied by complex impedance spectroscopy in a frequency range from 1 kHz to 1 MHz at different temperatures, where the insertion of cobalt in the Cu2+ and Ti4+ sites has a significant effect on the permittivity value (εr) and dielectric losses (tanδ). The non-ohmic characteristics showed that the change in grain size due to cobalt incorporation is beneficial to improving the breakdown strength (Eb) and nonlinear coefficient (α), which can be attributed to the grain boundary properties of the Internal Barrier Layer Capacitor (IBLC) model and the behavior of the Schottky barrier.

Supercapacitive behavior of two-dimensional carbon nanosheets with oxygen-induced interfacial modification

Biomass-derived carbon typically contains abundant heteroatomic defects and interfacial functional groups, which can contribute to additional pseudocapacitance. However, the type of interfacial functional groups in biomass-derived carbon is uncontrollable and variable, reducing their homogeneity. In this work, recyclable boric acid was employed as an activator to convert bioaerogels into carbon nanosheets. Subsequently, low-temperature air oxidation was utilized to modulate their thickness and microstructure. Notably, the multiple and uncontrollable functional groups at the carbon interface were uniformly transformed into oxygen-containing functional groups under oxygen induction, resulting in 2D carbon nanosheet materials with enhanced stability properties. Meanwhile, the introduction of more oxygen-containing functional groups, such as carbonyl (C=O) and carboxyl (-COOH) groups, improves material wettability and capacitive properties. In addition, the boron and nitrogen elements doping introduced by activators and precursors enhances its pseudocapacitive properties and electrical conductivity from the carbon lattice perspective. Moreover, the rich electron/deficient effect of BN valence bond can effectively boost their conductivity and rate performance. In fact, the materials present good capacitive properties (high specific capacitance of 298.5 F g−1 in KOH three-electrode system) and CDI (capacitive deionization) performance (good desalting capacity of 35.2 mg g−1 in CDI system).

Interface-Engineered MoSe2-Co9S8 Nanoheterostructures with Enhanced Charge Storage Performance for Supercapacitor Application.

Cobalt-based chalcogenides have emerged as fascinating materials for supercapacitor applications owing to the presence of various mixed valance oxidation states in their structure along with rich electrochemical properties. However, their limited stability and cyclic performance hinder their viability for practical use in supercapacitors. Herein, a facile hot injection colloidal route is demonstrated to design MoSe2-Co9S8 nanoheterostructures (NHSs), which entails the epitaxial growth of Co9S8 nanoparticles (NPs) over the basal planes of ultrathin MoSe2 nanosheets (NSs). The interfacial engineering of the basal planes of MoSe2 NSs with Co9S8 NPs regulates the electronic properties and defects at the interfaces and increases the overall specific surface area and conductivity. As a result, MoSe2-Co9S8 NHSs electrode unveils a substantially higher specific capacitance of 910.5 F g-1 at 1 A g-1current density surpassing their individual counterparts. In addition, it demonstrates worthy solidity, retaining ≈90% of its capacitance and coulombic efficiency of 93.3% after 10,000 charge-discharge cycles at a high charge-discharge current density of 15 A g-1. As a proof-of-concept, coin cells are fabricated using MoSe2-Co9S8 NHSs which show 93% Coulomb efficiency and 86% capacitance retention. This study would pave the way for designing transition metal dichalcogenides (TMDs) - derived NHSs with superior capacitive properties.

Model-based improvement of a trans-critical CO2 refrigeration plant

Abstract Refrigeration sector including heat pumps, cryogenics and air conditioning is responsible for a share close 10% of the global greenhouse gas emissions. Therefore, a huge effort of the scientific and industrial community is needed on the development of technologies allowing to reduce the environmental impact of this sector. The use of CO2 as working fluid has great interest in food chain conservation and participates to the problem of the impact produced by the traditional synthetic fluids, recently oriented also to hydrocarbons. Main problem of plants using CO2 as working fluid is the low COP, which reduces even more in moderate or hot climate regions in which low temperature thermal energy is more required. To assess the benefits introduced by plant optimization and innovative technologies, many advanced thermodynamic models are developed in the last years. Anyway, few software platforms are developed for the comprehensive analysis of plant behaviour. To fill this gap, this paper presents the results of a theoretical and experimental research done on an industrial trans-critical CO2 refrigeration plant. The aim was to set up energy saving solutions finalized to mitigate the intrinsic low COP values. A detailed physically consistent model of the unit has been developed following an integrated zero and mono-dimensional thermo-fluid-dynamic approach. The propagative, capacitive, and inertial properties of the components have been considered, so going beyond of the theoretical approaches that are typical in the sector. A wide experimental characterization of the unit has been done with the aim to validate the model and to use it as tool to predict the effect on the COP of the operating variables. The reduction of the compressor absorption and the potentiality of the energy recovery from energy usually wasted have been analysed.

Electrochemical performance of MWCNT nanowires-decorated ZnCo2O4 sphere nanocomposite for an asymmetric capacitor

A composite material consisting of porous ZnCo2O4 sphere covered with MWCNT nanowires is synthesised using a hydrothermal technique and thermal annealing. The capacitive properties of the electrode materials are examined. The ZnCo2O4/MWCNT composites have superior capacitive performance in comparison to pure ZnCo2O4 hexagonal nanoplates. The ZnCo2O4/MWCNT composites have a specific capacitance of 2080 F/g at 1 A g−1. The cells also exhibit outstanding rate capacity, maintaining 600 F/g even at 5 A g−1. The nanocomposites have exceptional retention rate, as seen by an only 4.7 % decrease in specific capacitance over 10,000 cycles. The improved capacitive efficiency of ZnCo2O4/MWCNT composites may be ascribed to the structural benefits of large surface area, excellent electrical characteristics, and a well-established network provided by the MWCNT support. The ASC device has a significant energy density of 52.74 Whkg−1 while operating at a power density of 4205 Wkg−1. Additionally, it has an operating voltage window of 0–1.6 V. The excellent capacitive performance shows the potential use of ZnCo2O4/MWCNT composites as electrodes for hybrid capacitors.

Enhanced high-temperature energy storage performance in all-organic dielectric films through synergistic crosslinking of chemical and physical interaction

Advanced electronic devices and energy systems urgently require high-temperature polymer dielectrics that can offer both high discharge energy density and energy storage efficiency. However, the capacitive properties of most polymers sharply deteriorate at elevated temperatures, due to the significant rise in leakage current density and energy loss. Herein, a new design approach is adopted to fabricate high-temperature polyetherimide (PEI) dielectrics with chemical and physical cooperative crosslinking networks, the dual-crosslinked PEI dielectrics are prepared through amine crosslinking agent and the electrostatic interaction of oppositely charged phenyl groups between triptycene (TE) and PEI chain segments. Benefiting from the increased crosslinking sites, the dual-crosslinked PEI films achieve the simultaneously enhancement in Tg, modulus and bandgap compared to un-crosslinked and single-crosslinked polymers. Meanwhile, the PEI with dual-crosslinked network displays higher chain packing density, effectively reducing the mean motion pathways of charge carriers and the conduction loss inside polymer dielectric. Consequently, the dual-crosslinked PEI containing 0.25 wt% TE delivers an outstanding discharge energy density of 2.69 J/cm3 and retains excellent cyclability after 100,000 charge–discharge cycles at 200 ℃. Additionally, finite element analysis and molecular dynamics simulation further confirm that less Joule heat and tighter chain structure are formed in the dual-crosslinked polymer dielectric. This research offers a novel methodology to prepare high-performance polymer dielectrics for high-temperature applications.

Biomimetic Redox Capacitor To Control the Flow of Electrons.

In biological systems, electrons, energy, and information "flow" through the redox modality, and we ask, does biology have redox capacitor capabilities for storing electrons? We describe emerging evidence indicating that biological phenolic/catecholic materials possess such redox capacitor properties. We further describe results that show biomimetic catecholic materials are reversibly redox-active with redox potentials in the midphysiological range and can repeatedly accept electrons (from various reductants), store electrons, and donate electrons (to various oxidants). Importantly, catechol-containing films that are assembled onto electrode surfaces can enhance the flow of electrons, energy, and information. Further, catechol-containing films can serve as redox-based interactive materials capable of actuating biological responses by turning on gene expression from redox-responsive genetic circuits. Looking forward, we envision that the emerging capabilities for measuring dynamic redox processes and reversible redox states will provide new insights into redox biology and will also catalyze new technological opportunities for information processing and energy harvesting.

Magnetic CuFe2O4 Spinel-Polypyrrole Pseudocapacitive Composites for Energy Storage.

This investigation focused on the fabrication of ceramic ferrimagnetic CuFe2O4-conductive polypyrrole (PPy) composites for energy storage. CuFe2O4 with a crystal size of 20-30 nm and saturation magnetization of 31.4 emu g-1 was prepared by hydrothermal synthesis, and PPy was prepared by chemical polymerization. High-active-mass composite electrodes were fabricated for energy storage in supercapacitors for operation in a sodium sulfate electrolyte. The addition of PPy to CuFe2O4 resulted in a decrease in charge transfer resistance and an increase in capacitance in the range from 1.20 F cm-2 (31 F g-1) to 4.52 F cm-2 (117.4 F g-1) at a 1 mV s-1 sweep rate and from 1.17 F cm-2 (29.9 F g-1) to 4.60 F cm-2 (120.1 F g-1) at a 3 mA cm-2 current density. The composites showed higher capacitance than other magnetic ceramic composites of the same mass containing PPy in the same potential range and exhibited improved cyclic stability. The magnetic behavior of the composites was influenced by the magnetic properties of ferrimagnetic CuFe2O4 and paramagnetic PPy. The composites showed a valuable combination of capacitive and magnetic properties and enriched materials science of magnetic supercapacitors for novel applications based on magnetoelectric and magnetocapacitive properties.