Studies on Possible Ion-Confinement in Nanopore for Enhanced Supercapacitor Performance in 4V EMIBF4 Ionic Liquids

Bioinspired Solid-State Nanochannel Sensors: From Ionic Current Signals, Current, and Fluorescence Dual Signals to Faraday Current Signals

Inspired from bioprotein channels of living organisms, constructing "abiotic" analogues, solid-state nanochannels, to achieve "smart" sensing towards various targets, is highly seductive. When encountered with certain stimuli, dynamic switch of terminal modified probes in terms of surface charge, conformation, fluorescence property, electric potential as well as wettability can be monitored via transmembrane ionic current, fluorescence intensity, faraday current signals of nanochannels and so on. Herein, the modification methodologies of nanochannels and targets-detecting application are summarized in ions, small molecules, as well as biomolecules, and systematically reviewed are the nanochannel-based detection means including 1) by transmembrane current signals; 2) by the coordination of current- and fluorescence-dual signals; 3) by faraday current signals from nanochannel-based electrode. The coordination of current and fluorescence dual signals offers great benefits for synchronous temporal and spatial monitoring. Faraday signals enable the nanoelectrode to monitor both redox and non-redox components. Notably, by incorporation with confined effect of tip region of a needle-like nanopipette, glorious in-vivo monitoring is conferred on the nanopipette detector at high temporal-spatial resolution. In addition, some outlooks for future application in reliable practical samples analysis and leading research endeavors in the related fantastic fields are provided.

Plasticized Polymer Blend Electrolyte Based on Chitosan for Energy Storage Application: Structural, Circuit Modeling, Morphological and Electrochemical Properties

Chitosan (CS)-dextran (DN) biopolymer electrolytes doped with ammonium iodide (NH₄I) and plasticized with glycerol (GL), then dispersed with Zn(II)-metal complex were fabricated for energy device application. The CS:DN:NH₄I:Zn(II)-complex was plasticized with various amounts of GL and the impact of used metal complex and GL on the properties of the formed electrolyte were investigated.The electrochemical impedance spectroscopy (EIS) measurements have shown that the highest conductivity for the plasticized system was 3.44 × 10⁻⁴ S/cm. From the x-ray diffraction (XRD) measurements, the plasticized electrolyte with minimum degree of crystallinity has shown the maximum conductivity. The effect of (GL) plasticizer on the film morphology was studied using FESEM. It has been confirmed via transference number analysis (TNM) that the transport mechanism in the prepared electrolyte is predominantly ionic in nature with a high transference number of ion (t_i)of 0.983. From a linear sweep voltammetry (LSV) study, the electrolyte was found to be electrochemically constant as the voltage sweeps linearly up to 1.25 V. The cyclic voltammetry (CV) curve covered most of the area of the current–potential plot with no redox peaks and the sweep rate was found to be affecting the capacitance. The electric double-layer capacitor (EDLC) has shown a great performance of specific capacitance (108.3 F/g), ESR(47.8 ohm), energy density (12.2 W/kg) and power density (1743.4 W/kg) for complete 100 cycles at a current density of 0.5 mA cm⁻².

Ghareeb H, Dannoun EMA, M. Abdullah R, Hamsan MH, Kadir MFZ. Plasticized Sodium-Ion Conducting PVA Based Polymer Electrolyte for Electrochemical Energy Storage-EEC Modeling, Transport Properties, and Charge-Discharge Characteristics

This report presents the preparation of plasticized sodium ion-conducting polymer electrolytes based on polyvinyl alcohol (PVA)via solution cast technique. The prepared plasticized polymer electrolytes were utilized in the device fabrication of electrical double-layer capacitors (EDLCs). On an assembly EDLC system, cyclic voltammetry (CV), electrical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), transfer number measurement (TNM) and charge-discharging responses were performed. The influence of plasticization on polymer electrolytes was investigated in terms of electrochemical properties applying EIS and TNM. The EIS was fitted with electrical equivalent circuit (EEC) models and ion transport parameters were estimated with the highest conductivity of 1.17 × 10-3 S cm-1 was recorded. The CV and charge-discharging responses were used to evaluate the capacitance and the equivalent series resistance (ESR), respectively. The ESR of the highest conductive sample was found to be 91.2 Ω at the first cycle, with the decomposition voltage of 2.12 V. The TNM measurement has shown the dominancy of ions with tion = 0.982 for the highest conducting sample. The absence of redox peaks was proved via CV, indicating the charge storing process that comprised ion accumulation at the interfacial region. The fabricated EDLC device is stable for up to 400 cycles. At the first cycle, a high specific capacitance of 169 F/g, an energy density of 19 Wh/kg, and a power density of 600 W/kg were obtained.

The Study of Electrical and Electrochemical Properties of Magnesium Ion Conducting CS: PVA Based Polymer Blend Electrolytes: Role of Lattice Energy of Magnesium Salts on EDLC Performance

Plasticized magnesium ion conducting polymer blend electrolytes based on chitosan (CS): polyvinyl alcohol (PVA) was synthesized with a casting technique. The source of ions is magnesium triflate Mg(CF3SO3)2, and glycerol was used as a plasticizer. The electrical and electrochemical characteristics were examined. The outcome from X-ray diffraction (XRD) examination illustrates that the electrolyte with highest conductivity exhibits the minimum degree of crystallinity. The study of the dielectric relaxation has shown that the peak appearance obeys the non-Debye type of relaxation process. An enhancement in conductivity of ions of the electrolyte system was achieved by insertion of glycerol. The total conductivity is essentially ascribed to ions instead of electrons. The maximum DC ionic conductivity was measured to be 1.016 × 10-5 S cm-1 when 42 wt.% of plasticizer was added. Potential stability of the highest conducting electrolyte was found to be 2.4 V. The cyclic voltammetry (CV) response shows the behavior of the capacitor is non-Faradaic where no redox peaks appear. The shape of the CV response and EDLC specific capacitance are influenced by the scan rate. The specific capacitance values were 7.41 F/g and 32.69 F/g at 100 mV/s and 10 mV/s, respectively. Finally, the electrolyte with maximum conductivity value is obtained and used as electrodes separator in the electrochemical double-layer capacitor (EDLC) applications. The role of lattice energy of magnesium salts in energy storage performance is discussed in detail.

Electrolyte-Dependent Supercapacitor Performance on Nitrogen-Doped Porous Bio-Carbon from Gelatin

The carbon supercapacitance strongly relies upon the electrolyte’s nature, but the clear-cut structure–performance nexus remains elusive. Herein, a series of bio-carbons with gradually varied pore structure and surface chemistry are derived using a new salt template protocol (with eco-benign KNO₃ as the template, activator, and porogen, and cheap gelatin as the carbon precursor), and are used as model systems to probe the dependence of the electrochemical mechanism of such nanocarbons on two typical electrolytes (KOH and EMIBF₄). By only adjusting the KNO₃ dosage, two pivotal figures of merit of biochar—multiscale porosity and surface functionalization—were finely modulated to construct electric double layers. Electrochemical data clarify that the combined porosity and doping effects all contribute to enhanced supercapacitance, but with only one of the two factors playing the leading role in different electrolytes. Kinetic analysis corroborates the fact that ample heteroatom doping can effectively compensate capacitance by intensive surface redox insertion in KOH, while a suitable pore size dispersion plays a preponderant part in self-amplifying the ion partitioning, and thus dictating a good charge separation in EMIBF₄. A quasi-quantitative model of performance–structure relevance in EMIBF₄ is judiciously conjectured to hint at a superb ion–pore-size compatibility, in which the bi- and mono-layer ion confinement coupling in integrated single and double ion-sized pores is found to be more useful for curbing notorious over-screening effects and for changing the coordination number, Coulombic ordering, and phase conformation of EMIBF₄ in several nm-sized nanopores. This unique energy storage fashion in ion-matching pores promotes the energy density of optimal samples to a novel level of 88.3 Wh kg⁻¹ at 1 kW kg⁻¹, which rivals the overwhelming majority of the reported carbon materials. In short, the comparison case study here reveals a valuable correlation of carbon’s figure of merit and electrolyte type, which may act as a vital rudder to design electrolyte-contingent state-of-the-art supercapacitor materials.

Porous Doped Carbons from Anthracite for High-Performance Supercapacitors

Carbon-based materials, as some of the most important electrode materials for supercapacitors (SC), have spurred enormous attentions. Now, it is highly desirable but remains an open challenge to design stable and high-capacity carbons for further enhancing supercapacitive function. Here, a facile chemical activation recipe is introduced to develop biomass-derived functional carbons using cheap and abundant natural resources, anthracite, as the heteroatom-rich carbon sources, and potassium hydroxide (KOH) as activator. These porous carbons have high BET surface areas of roughly 2814 m2 g−1, large pore volumes of up to 1.531 cm3 g−1, and a high porosity that combines micro- and small-sized mesopores. The optimal nanocarbon features two additional outstanding virtues: an appropriate N-doping level (2.77%) and a uniform pore size distribution in the narrow range of 1–4 nm. Synergy of the above unique structural traits and desirable chemical composition endows resultant samples with the much boosted supercapacitive property with remarkable specific capacitance at varied current densities (e.g., 325 F g−1 at 0.5 A/g), impressive energy/power density, and long cycling stability over 5000 cycles at 10 A g−1 (92% capacity retention). When constructing the symmetric supercapacitor utilizing a common neutral Na2SO4 electrolyte that can strongly circumvent the corrosion effect occurring in the strong acid/alkaline solutions, both an elevated operation voltage at 1.8 V and a fascinating energy density of 23.5 Wh kg−1 are attained. The current study paves the way to explore the stable, efficient, and high-voltage SC assembled by the anthracite-derived porous doped nanocarbons for a wide spectrum of applications like automobiles, vehicle devices, and so on.