Separators For Supercapacitors Research Articles

Unsuspected Organometallic Fibers Used As Potential Separators for Supercapacitors Device

Since the last decade, the interest of organic frameworks for electrochemical application the been more studied.1 In general, very few works have been found in the literature. We can mainly mention the use of these derivatives in the presence of inorganic materials both to form solid electrolytes or to protect electrodes. For example, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (H4DOTA) has been used to functionalize PVA to coat the surface of the negative electrode in order to suppress its degradation.2 This resulted in the improvement of the electrochemical properties of the LMNO/graphite cell. Recently, Kim et al. reported the addition of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane to a carbonate-based electrolyte intended to stabilize the Li metal-electrolyte interface by improving the solid electrolyte interphase.3 More recently, Liu et al. reported a novel carbonyl network polymer NP4 used as a cathode material for organic lithium batteries.4 Very few examples of fully organic frameworks used as separators have been reported.Therefore, our investigation to develop new supramolecular metal-based objects via a self-assembly process of molecular bricks will be presented. The work on cyclen derivatives allows to obtain metal complexes very stable able to pack in a well oriented dimension. Cyclen derivatives, in the presence of metal salts such as copper or zinc chlorides and polar solvents such as aliphatic alcohols, have a strong affinity for metals and spontaneously assemble in some conditions.5 In terms of applications, these self-assembled "organometallic" fibers represent an original and relatively easy to access substrate for fabricating 1D organic objects. Moreover, taking advantage of the properties and potentialities of these materials, we format an adequate shape to handle it as a potential separator for application in Energy Storage Systems (ESS).After a presentation of their synthesis and their formatting as potential separators for supercapacitors, preliminary electrochemical studies will be discussed. 1. J. Mater.Chem. A 2016, 4, 16812; ACS Energy let., 2022, 7, 885.2. ACS Appl. Energy Mater., 2021, 4, 128.3. ACS Appl. Matter. Interface, 2022, 14, 35645.4. J. Electoanalytical. Chem. 2023, 117251.5. Chem. Commun. 2010, 46, 1464. Figure 1

Chitosan derived porous carbon prepared by amino acid proton salt for high-performance quasi-state-solid supercapacitor

The electrode material and electrolyte are the major factors influencing the performance of supercapacitor, and they are the current research hotspots in this field. Herein, three chitosan (CS) based gel electrolytes were prepared by mixing CS with different acidity of amino acids (acidic, neutral and basic) proton salts. The CS/[Asp]NO3 gel film is prepared from aspartate nitrate proton salt ([Asp]NO3) formed by acid amino acid (aspartic acid, Asp) and CS exhibits superior mechanical property. This gel film can immerse in KOH or Na2SO4 solution directly and get alkaline and neutral gel electrolyte films. It possesses high ionic conductivity and excellent mechanical properties when used as gel electrolyte and separator in supercapacitor. Furthermore, the gel film can use as carbon precursor to prepare N-doped porous carbon (HN-HPCs). The as-prepared porous carbon exhibits large specific surface area (1599 m2 g−1), high micropore ratio (88%), hierarchical porous honeycomb structure and high N doping content (7.04 at%). The specific capacitance can reach up to 459 F g−1 in 6 M KOH. The assembled flexible quasi-solid-state supercapacitor using HN-HPCs and prepared gel electrolyte exhibits high energy densities of 28.3 Wh kg−1. It demonstrates an efficient strategy to prepare CS based gel electrolyte and simultaneously use the gel to prepare high N doping and hierarchical porous carbon. This work will provide guidelines for designing high-performance electrode material and electrolyte for flexible supercapacitor.

Application of electrospun polyimide-based porous nano-fibers separators in ionic liquid electrolyte for electrical double-layer capacitors

This paper studies the preparation and characterization of polyimide (PI)-based porous nano-fibers as separator for supercapacitor. PI-based porous nano-fibers were fabricated by electrospinning soluble PI and polyvinyl pyrrolidone (PVP), followed by solution induced phase separation process under ultrasonic-assisted vibration. The morphology and structure of PI-based separator was investigated by means of scanning electronics microscope, pore structure and specific surface area analysis. The electrochemical performances were characterized by alternative current impedance, cyclic voltammetry and constant current charge/discharge test in an ionic liquid electrolyte. The results indicate that PI nano-fibers derived from PI: PVP mass ratio = 1: 1 electrospun fibers exhibit high specific surface area (212.4 m 2 g −1 ), wide stability electrochemical windows (0.0–4.55 V) and high electrolyte uptake (430 wt . %). The graphical abstract is about the tittle Application of electrospun polyimide-based porous nano-fibers separators in ionic liquid electrolyte for electrical double-layer capacitors. • PI-based porous nano-fibers were prepared via PI/PVP blended electrospinning and solvent induce phase separation process. • PI-based nano-fibers are suitable for the adsorption, diffusion and infiltration of ionic liquids with a large ionic size. • PI-based porous nano-fibers separators exhibit high electrolyte uptake (430 wt %), wide stability electrochemical window (0.0 V–4.55 V) in ionic liquids electrolyte.

Trash to treasure: Fallen leaves as separators for supercapacitors

Trash to treasure: Fallen leaves as separators for supercapacitors

PAN-derived electrospun nanofibers for supercapacitor applications: ongoing approaches and challenges

The increasing demand for high-performance supercapacitors stimulates the rapid development of separators and electrodes. PAN-derived nanofibers via electrospinning with one-dimensional morphology, tunable nanostructure, mechanical flexibility, self-functionalities and those that can be added onto them have witnessed the intensive development and extensive applications of supercapacitors. However, the conventional PAN-derived carbon nanofibers are generally featured with rather inferior electrical conductivity and lower specific surface area. Beyond that, PAN-derived carbon nanofibers normally exhibit unsatisfactory electrochemical performance in supercapacitors. So far, several strategies have been proposed, by some of which, conspicuous success has been achieved in addressing the above key issues. Here, a comprehensive review on recent advances of the use of PAN-derived carbon nanofibers as the electrode materials for supercapacitors are provided with a focus on strategies to improve their electrochemical performances, and the basic scientific principles involved in these preparation processes. Next, the recent application progress of PAN-derived nanofibers as the electrode separators for supercapacitors is introduced. Finally, we put forward a series of critical challenges in the above research area and propose some correlative ideas for future research.

Electrospun Poly[poly(2,5-benzophenone)]bibenzopyrrolone/polyimide nanofiber membrane for high-temperature and strong-alkali supercapacitor

The separator is an important component for energy storage devices. At present, the membranes for supercapacitors are rare, especially the ones that work with an alkaline electrolyte. Herein, a type of flexible and highly porous polymer hybrid nanofiber membrane was prepared via a facile electrospinning process and served as a separator for supercapacitor’s work with strong alkaline electrolyte. As obtained, poly[poly(2,5-benzophenone)]bibenzopyrrolone/polyimide (PBPY/PI) membrane showed good thermal stability, high mechanical strength, large electrolyte uptake (452%), and fast ion conductivity (0.68 mS/cm). Moreover, PBPY/PI membrane exhibited excellent alkali resistance. The supercapacitor assembled with PBPY/PI membrane showed much better performance than those assembled with a commercial polypropylene membrane and electrospun polyimide nanofiber membrane and was found without capacitance loss after charge/discharge at 30 A/g for 10,000 cycles at 80 °C. The PBPY/PI membrane is a good candidate with temperature resistance and alkali resistance for high-performance supercapacitors.

Raw cellulose/polyvinyl alcohol blending separators prepared by phase inversion for high-performance supercapacitors

The development of a biodegradable cellulose-based separator with excellent performance has been of great research significance and application potential for the green development of supercapacitors. Herein, the regenerated porous cellulose/Polyvinyl alcohol films (CP-10, CP-15, CP-20, CP-25) with different mass ratio were successfully fabricated by a simple blending and phase inversion process. Their electrochemical properties as separators in assembled supercapacitor were evaluated. Fourier transform infrared spectroscopy and x-ray diffraction analysis indicate that intermolecular and intramolecular hydrogen bonding existed between cellulose and polyvinyl alcohol of the CP films. Compared with other CP films, the CP-20 film shows higher mechanical strength (28.02 MPa), better wettability (79.06°), higher porosity (59.69%) and electrolyte uptake (281.26 wt%). These properties of CP-20 are expected to show better electrochemical performance as separator. Indeed, the electrochemical tests, including electrochemical impedance spectroscopy, cyclic voltammetry, galvanostatic charge discharge, demonstrate that the SC-20 capacitor (with CP-20 as separator) shows the lowest equivalent series resistance of 0.57 Ω, the highest areal capacitance of 1.98 F cm−2 at 10 mV s−1, specific capacitance of 134.41 F g−1 and charge-discharge efficiency of 98.62% at 1 A g−1 among the four capacitors with CP films as separators. Comparing the assembled SC-40 and SC-30 with two commercial separators (TF4040 and MPF30AC) and SC-PVA with Polyvinyl alcohol (PVA) separator, the CV and GCD curves of SC-20 maintain the quasi rectangular and symmetrical triangular profiles respectively at different scan rates in potential window of 0–1 V. SC-20 exhibits the highest value of 28.24 Wh kg−1 at 0.5 A g−1 with a power density of 0.26 kW kg−1, and 13.41 Wh kg−1 at 10 A g−1 with a power density of 6.04 kW kg−1. SC-20 also shows the lowest voltage drop and the highest areal and specific capacitance. Moreover, SC-20 maintains the highest value of 86.81% after 4000 cycles compared to 21.18% of SC-40, 75.07% of SC-30, and 6.66% of SC-PVA, showing a superior rate capability of a supercapacitor. These results indicate that CP films can be served as promising separators for supercapacitors.

Renewable cellulose separator with good thermal stability prepared via phase inversion for high-performance supercapacitors

In this study, the regenerated porous cellulose films were properly prepared by dissolving different masses of cellulose (4%, 6%, 8%) in LiCl/DMAc solvent though a simple phase inversion process and as separator (CLD-4, CLD-6, CLD-8) for the assembled supercapacitors (ABSC-4, ABSC-6, ABSC-8). The investigation on the different masses of cellulose indicated that CLD-8 film showed a stronger hydrogen bond interaction, higher thermal stability and better tensile strength. In addition, CLD-8 has good lyophilicity (101.1°), high porosity (58.43%), and electrolyte absorption (329.30%). Furthermore, different cellulose films as separator were used for assembling supercapacitor. Compared with ABSC-4 and ABSC-6, ABSC-8 showed a lower equivalent series resistance of 0.37Ω, a higher charge-discharge efficiency of 98.87% at 1 A/g, and areal capacitance of 1.16 F/cm2 at 5 mV/s. ABSC-8 also showed a superior capacity retention of 92.09% over 4000 cycles at 1 A/g. So, CLD-8 film has a potential to be used as separator for supercapacitor. Furthermore, the comparative analysis of supercapacitors assembled by CLD-8 separator and two commercial separators were conducted. The results show that ABSC-8 showed a higher value of 25.94 Wh/kg at 0.5 A/g with a powder density of 0.36 kW/kg, a lower voltage drops below 0.02 V at 1.0, and 3.0 A/g, a higher specific capacitance of 123 F/g at 0.5 A/g. Moreover, ABSC-8 maintained their quasi-rectangular and symmetrical triangular profiles of the CV and GCD curves in 0–1 and 0–1.5 V, respectively, suggesting the applicability of a wide working potential window. These results provide insights into the full use of natural and biodegradable cellulose film prepared by a simple phase inversion as separators for supercapacitors.

Nanodiamond‐Based Separators for Supercapacitors Realized on Paper Substrates

In response to the request for sustainable high performance energy storage devices, a significant interest is focused on developing environmentally friendly supercapacitors. In this context, cellulose‐based substrates for energy storage devices can be well‐engineered, lightweight, safe, thin, and flexible. Herein, a scalable, low‐cost, and easy‐to‐process approach for the preparation of supercapacitors using large area techniques like spray and blade coating is presented. Following a green strategy, all components are chosen or formulated in water‐based dispersions. Symmetric supercapacitors using common copy paper and electronic paper as the substrate, and poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) as electrodes, are realized and investigated. The novelty of this work consists of the use of composites based on detonation nanodiamonds (DNDs) and hydroxypropyl cellulose (HPC) as a solid‐state electrolyte and separator. Devices with solution electrolyte using the same HPC + DND composite but with the addition of sodium sulfate are prepared. The performance obtained using solid electrolyte (HPC + DNDs) and liquid electrolyte (HPC + DNDs + Na2SO4) on both substrates is comparable in terms of specific capacitance: ≈0.13 – 0.52 F g−1for (HPC + DNDs) and ≈0.35 – 0.82 F g−1for (HPC + DNDs + Na2SO4), with power density in the range of ≈19 – 24 μW cm−2.

Tree leaves-derived three-dimensional porous networks as separators for graphene-based supercapacitors

The development of environment-friendly separators with low cost and high efficiency is necessary for the application of supercapacitors. Herein, as an inexpensive, clean and renewable biomass, tree leave was developed to be used as a new kind of separator for supercapacitor. After being chemically activated with sodium hydroxide for proper time, four kinds of activated tree leaves exhibited abundant nanosized and interconnected pores on surface, which was beneficial for the ion transport and resulted in better performance of supercapacitor. Particularly, the supercapacitor using activated cinnamomum camphora leaf as the separator displayed the highest specific capacitance (251 F g−1) at the current density of 0.5 A g−1. Meanwhile, the specific capacitance retained about 80% even after 1000 consecutive cycles, showing good stability. All the results indicated the activated tree leaves-based separators with facile fabrication, low cost and high performance had promising application in supercapacitors.

Preparation of a cheap and environmentally friendly separator by coaxial electrospinning toward suppressing self-discharge of supercapacitors

Herein, a cheap, environmentally-friendly and degradable polyacrylonitrile coated by sodium dodecyl benzene sulfonate (PAN@SDBS) nanofibers membrane is prepared by coaxial electrospinning method and further used as a separator for supercapacitor. The self-discharge behavior is well suppressed by restraining the ion diffusion driven by concentration gradient without sacrificing electrochemical performance.

Supported Ionic Liquid Gel Membrane Electrolytes for Flexible Supercapacitors

AbstractIn this work, a novel and easy‐to‐use methodology is developed to prepare supported ionic liquid gel membranes (SILGMs) by incorporating ionogels into commercial porous supports, to use as both electrolytes and separators for supercapacitors. Macroscopic sol–gel transition temperature, Fourier transform infrared spectra, and thermal behaviors of the ionogels are systematically investigated. Ionic conductivities of the ionogels and SILGMs are measured from 25 to 100 °C. The ionic conductivities of the ionogels are lower by one order of magnitude once they are incorporated into the supports. Nonetheless, the ionic conductivity of the SILGMs has reached the practical application level required for energy storage and conversion devices. Furthermore, the stability and flexibility of SILGMs are investigated as flexible electrolytes for supercapacitor devices (see Video in the Supporting Information). Charge–discharge cycling of symmetric supercapacitors based on the SILGMs reveal specific capacitance as high as 153 F g−1 at 0.1 A g−1, and remain at 101 F g−1 at 10 A g−1. The capacitance retention after 10 000 charge–discharge cycles at 5.0 A g−1 is as high as 97%, demonstrating excellent cycle stability of the device. The studies suggest that SILGMs are promising candidates for stable, high performance, and flexible energy storage and conversion devices that could be made by high volume roll‐to‐roll processing.

High performance disulfonated poly(arylene ether sulfone)/poly(ethylene oxide) composite membrane used as a novel separator for supercapacitor with neutral electrolyte and activated carbon electrodes

High performance disulfonated poly(arylene ether sulfone)/poly(ethylene oxide) (SPAES/PEO) composite membranes were prepared by a simple method such as a novel separator saturated by the lithium sulfate (Li2SO4) aqueous electrolyte for application in supercapacitors (SCs). As prepared composite membranes exhibit excellent mechanical properties and thermal stabilities, which are beneficial for the safety in potential applications, meanwhile, the addition of PEO on membrane also enhanced the affinity with electrolyte and the ion conduction for lithium salts. In addition, the SC cell was fabricated with optimized SPAES/PEO composite membrane and activated carbon electrodes with Li2SO4 aqueous electrolyte. The obtained SC with the SPAES/PEO separator revealed a specific capacitance of 142.5 F g−1 at a current density of 0.1 A g−1. Furthermore, the energy density of the SC was promoted to 19.04 Wh kg−1 due to the wide working voltage range of the neutral electrolyte, and the SC exhibited an excellent coulombic efficiency of almost 99% and nearly 100% cycling retention after 5000 galvanostatic charge/discharge cycles. All of these results indicated that SPAES/PEO composite membrane is suitable as a novel separator for SC.

Quaternary ammonium functionalized poly(aryl ether sulfone)s as separators for supercapacitors based on activated carbon electrodes

A series of poly(aryl ether sulfone) copolymers containing quaternary ammonium moieties were obtained by polymerization of methylated copolymers, followed by bromination and derivatization with quaternary-ammonium groups. The copolymer membranes exhibited excellent thermal stability and mechanical properties. Symmetric supercapacitor single cells based on activated carbon and quaternary ammonium functionalized poly(aryl ether sulfone) membranes were fabricated into a three-layer structure: activated carbon electrode//quaternary ammonium functionalized poly(aryl ether sulfone) separator//activated carbon electrode and characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in 6M KOH aqueous solution. The coulombic efficiency of the supercapacitor was as high as 95% over 5000cycles. The effect of different degree of quaternization of PAES copolymer separators on thermal and mechanical properties of separators and performance of the symmetric supercapacitor single cells were investigated.

Polymer membranes as separators for supercapacitors

The purpose of the studies described was to examine the influence of low-energy plasma modification of polyamide and polypropylene polymer nonwoven fabrics on the usable properties of supercapacitors when using these fabrics as the separator material. To achieve this goal the following investigations were carried out: testing the time required for electrolyte saturation of separators and the conductivity of the electrolyte contained in the separator, as well as electrochemical examinations of supercapacitor models in which the modified fabric separators were used. The tests conducted fully confirm the usability of this modification for cleaning the surface and improving the wettability of separators by the electrolyte, which in turn results in a significant decrease of the internal resistance of the supercapacitor, thus increasing the usable power of the device.

Electrospinning Technology for Applications in Supercapacitors

Electrospinning is an effective technology for preparing free-standing fiber mats with ultrathin fiber diameter. In this review, the electrospinning technology for application in supercapacitors is discussed. Electrode materials assembled by electrospinning and other post-treatment and chemical modification for electrical double-layer capacitors and pseudocapacitors are summarized. Meanwhile, the electrospun nanofiber mats for separator in supercapacitor is also highlighted. Keywords: Electrospinning, Supercapacitor, Electrode, Separator.

Using eggshell membrane as a separator in supercapacitor

A separator is prepared based on natural and flexible eggshell membrane (ESM) for supercapacitor application. Morphology observation shows that the ESM is consisted of hierarchically ordered macroporous network. With a high decomposition temperature (>220°C), enough mechanical strength (σmax=6.59±0.48MPa, ɛmax=6.98±0.31%, respectively), and low water uptake and swelling property (<10%), ESM could be a promising candidate for supercapacitor separator. As expected, the supercapacitor with ESM separator exhibits outstanding electrochemical performances, such as low resistance, quick charge–discharge ability (τ is 4.76s), and good cyclic stability (92% retention after 10,000 cycles). However, the one with PE separator shows worse properties (high resistance, low specific capacitance, etc.). This research provides new insight into the preparation of natural, low-cost and high-performance separator for supercapacitor and other applications.