Diffusion Of Electrolyte Ions Research Articles

Lamellar Hierarchical Porous Carbon Prepared from Coal Tar Pitch through a Lamellar Hard Template Combined with the Precarbonization and Activation Method for Supercapacitors

The lamellar porous carbon favors the diffusion and penetration of electrolyte ions and presents a fantastic advantage as an energy storage electrode material. In this work, the lamellar Mg5(OH)4(CO3)2·4H2O template is synthesized via a simple precipitation method in the low-temperature hydrothermal condition. Lamellar hierarchical porous carbon (LHPC) is successfully synthesized through the Mg5(OH)4(CO3)2·4H2O hard template and the KOH activation method using coal tar pitch (CTP) as the carbon source. The effects of activation temperature and activator dosage on the morphology, microstructure, and supercapacitor performance are researched at length. LHPCs-1–700 displays a good lamellar structure and an abundant mesoporous structure, so as to exhibit superior capacitive performance compared with other carbon electrodes. The specific capacitance for LHPCs-1–700 reaches 298 F g–1 at 1 A g–1 and still maintains 234 F g–1 at 50 A g–1 with a high capacitance retention of 78.5% in the three-electrode system. The kinetic behavior of the LHPCs-1–700 electrode was also analyzed according to the CV data obtained at different scan rates, and it was found that the fast kinetic capacitance contribution was up to 87% at 200 mV s–1. The assembled LHPCs-1–700 symmetric supercapacitor delivered an energy density of 16.73 W h kg–1 with a power density of 859.4 W kg–1 in 1 M Na2SO4 solution. Besides, the specific capacitance retention rate could still reach 95.8% after 8000 cycles.

High performing asymmetric supercapacitor fabricated by defect induced cathodic MnV2O7 and biowaste derive anodic activated carbon

The dual metal oxides anticipated prospective substitution of the transition of cathodic energy materials. The prominent attributes like higher specific energy, specific power, and long cycle stability are crucial to a supercapacitor device's energy storage. In this acclaimed research, the novel MnV2O7 composite is fabricated by microwave process and tailed by a hydrothermal method where dimethyl formamide, ethylene glycol, and water are used as solvents separately. The bimetallic oxide's distinctive morphology with crystallinity variation realizes by the solvent. It delineates a higher active surface area that grossly supersedes redox-active sites, which eases diffusion of electrolyte ions and multi-valence redox reaction with ions intercalation. The lignocellulosic bio-waste-derived activated carbon materials are worked as anodic material. The synthesized oxide is investigated using diversified characterization tools to confirm the phase formation and investigated by electron microscopy for structural characteristics. The Hirshfeld surface, EPR and theoretical generalized gradient approximations simulation assist in comprehending the electronic interaction to elucidate the experimental consequences. The MnV2O7 oxide depicts improved capacitance is 402 Fg−1 at 2 mVs−1 scan rate and 364 Fg−1 at 2 mAcm−2 current for dimethyl formamide as solvent compared to rest. Also, composites delineate 96 % long cycle stability up to 10,000 cycles at 40mAcm−2 current with a maximum specific energy of 51.8 Whkg−1 and specific power of 2500 Wkg−1. The integration of augmented energy storage of the composite leads to a perfect candidate to apprehend the urge of novel advanced materials engineering for applications of energy storage.

Evaluation of the Datura peels derived biochar-based Anode for enhancing power output in microbial fuel cell application

Activated biochar utilizing Datura metel peel was synthesized using pyrolysis at 800oC and activated using KOH. The resulting biochar was investigated as an anode material in a Pseudomonas aeruginosa powered microbial fuel cell (MFC) utilizing acetate as the substrate for the first time. The average chemical oxygen demand (COD) elimination was 85.4% in closed circuit mode. The maximum power production was observed in MFC containing 1 mg/cm2 biochar impregnated anode with a peak power density measured at 584.2 mW/m2. The results of biochar characterization using Field Emission Scanning Electron Microscope (FE-SEM) illustrates the presence of spherical globular texture which indicates the nano spherical structure of carbon nanoparticles in the biochar. The porous texture and interlinked characteristics of carbon nano-spheres can significantly enhance the diffusion of electrolyte ions. The confocal laser scanning microscopy (CLSM) results show a high number of cell biomass on 1 mg/cm2 biochar impregnated anode, indicating that 1 mg/cm2 biochar promotes enhanced biofilm formation. These results emphasize the utilization of biochar as electrodes in MFCs to allow for simultaneous wastewater treatment and electricity generation .

Fabrication of Symmetric Polyaniline/Nano‐Titanium Dioxide/Activated Carbon Supercapacitor Device in Different Electrolytic Mediums: Role of High Surface Area of Carbon and Facile Interactions with Nano‐Titanium Dioxide for High‐Performance Supercapacitor

Four nanocomposite samples of polyaniline/nano titanium dioxide/activated carbon (PANI/nTiO2/AC) via ex situ and in situ polymerization methods are prepared and optimized for electrochemical analysis in three different electrolytes, i.e., acidic H2SO4, basic KOH, and neutral Na2SO4. The results indicate that PANI/nTiO2/AC (PTA2) has a good, interconnected network. The presence of TiO2 nanoparticles promotes the faradaic capacitance, and AC also provides a large surface area for proficient redox reactions. The electrochemical performances of the ternary nanocomposite electrode material are examined by cyclic voltammetry, galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy test with three different electrolytes, i.e., acidic (0.1 m H2SO4), basic (0.1 m KOH), and neutral (0.1 m Na2SO4) aqueous electrolytes. The results reveal that present device attains maximum specific capacitance value 827 F g−1 at 10 mV s−1 in 0.1 m H2SO4 for PTA2 supercapacitor device and shows 72% retain specific capacitance from initial value of specific capacitance after 10 000 GCD cycle. Moreover, it also exhibited maximum energy density of 37 Wh kg−1 at 0.5 mA cm−2 with maximum specific power of 1332 W kg−1. The reason may be attributed to increased π–π conjugated system for PANI with titanium dioxide nanoparticles and AC for providing an effective surface area (343 m2 g−1) for the electrolyte ions to penetrate inside the electrode material and also furnishing efficient diffusion of electrolyte ions in PANI matrix. PTA2 ternary nanocomposite shows more thermal stability than PANI alone. It enhances the overall supercapacitive performance of the supercapacitor device (PTA2 device), which is a symbolic improvement compared to reported articles.

Perylene-Templated Hierarchically Porous Carbon Fibers as Efficient Supercapacitor Electrode Material

Abstract Nitrogen-doped nanoporous carbon fibers were prepared using chromonic perylene bisimide self-assemblies as templates. The method involves the formation of perylene-templated silica followed by carbonization and etching. This strategy does not require any additional carbon or nitrogen precursor and therefore omits the associated impregnation step. The obtained carbon fibers were tested as electrode materials for supercapacitor applications. Owing to the high surface area (695 m2 g−1) and well-developed porosity (pore volume ca. 0.67 cm3 g−1) with hierarchical micro- and mesopore structures, N-doping and high-wettability, amorphous carbon fibers show excellent electrical double-layer capacitance with faradaic pseudocapacitance performance in an aqueous electrolyte solution (1 M H2SO4). A working electrode prepared from the optimal sample achieved a high specific capacitance of 317 F g−1 at a current density of 1 A g−1 with excellent capacitance retention of 80% at a high current density of 50 A g−1 suggesting a fast electrolyte ion diffusion at the electrode surface. The electrode also showed outstanding cycle stability of 99% after 10,000 successive charge-discharge cycles. These results show the high potential of chromonic-derived hierarchically porous carbon fibers as electrode materials for high-performance supercapacitors with advantages over electrospinning and catalytic fabrication methods, such as the absence of heavy metals and organic solvents in the preparation procedure.

Vertically aligned polyaniline nano-array decorated on ultra-thin MXene nanosheets for high energy density supercapacitors

Titanium carbide (Ti3C2), with the features of metallic conductivity and two-dimension (2D) structure, is considered as a promising material using in supercapacitors. In this work, a kind of Ti3C2-based nanocomposite with vertically-aligned polyaniline (PANI) nanoarrays was prepared by simple in-situ polymerization, where Ti3C2 served as a conductive substrate supporting the growth of PANI. Vertically aligned PANI nano-array may increase the surface area, provide considerable pseudocapacitance, and prevent the aggregation of Ti3C2 nanosheets. Owing to its hierarchical structure, the composite electrode gained significant advantage in increasing electrochemical active sites and accelerating electrolyte ions diffusion. The energy storage devices with high electrochemical performance and simple preparation methods has attracted much attention reached 536 F g−1 at the current density of 0.1 A g−1, and the composite had a good capacitance retention and cycle stability (86.2 % after 5000 cycles) at a high current density of 10 A g−1. In addition, the symmetric supercapacitor was assembled and displayed a high energy density (933.9 W kg−1) at the power density of 26.9 Wh kg−1. After 5000 charge-discharge cycles, the capacitance retention rate is 70.4 %. The experimental results indicated that the improved electrochemical performance of supercapacitor was closely related to the introduction of Ti3C2 and construction of the hierarchical structure. Furthermore, the preparation strategy of Ti3C2-PANI composite can be used to further produce other composites with similar regular structure and unique electrochemical performance.

Magnetically-oriented porous hydrogel advances wearable electrochemical solidoid sensing heavy metallic ions

Developing wearable sensors to determine chemical contamination in solidoid is currently a great challenge. Hydrogels with polymeric networks have been employed as electrochemical cells and media to realize wearable solidoid sensing. However, it is still a hard task to enable hydrogel to simultaneously possess effective mass transfer, mechanical robustness as well as easy and tight adhesion to sensing electrodes. Routinely, a hydrogel with improved adhesion to the electrode surface by introducing additives may deteriorate the mass transfer capability. Increasing the porosity of hydrogel could enhance mass diffusion but sacrifices mechanical robustness. Herein, a composite hydrogel is achieved by embedding magnetic oriented MWCNT-Fe3O4 strips in porous agarose (MMFPA), which exhibits enhanced permeability and speeding diffusion of electrolyte ions. Moreover, the orientation in order and strip-like MWCNT-Fe3O4 three-dimensional composites improve the compressive strength of hydrogel, which could recover back within 2 min in water after removal of pressure. Such magnetic hydrogel is beneficial to be assembled to the wearable glove sensor by using magnets to achieve a stable and compact sensing platform. As the application example, the resultant wearable sensing protocol is successfully utilized to monitor Cd2+ trace residues in rice, tea, and soil with an affordable response as low as 0.112 mg/kg and rapid signal acquisition (<5 min). It paves an attractive, accessible, and effective way to on-site evaluate solidoid Cd2+ level for forewarning food safety and environmental risk.

Interfacial electronic regulation on NiCo2O4 nanowires@NiFe-LDH nanosheets heterostructure for efficient oxygen evolution

Developing cost-effective, highly efficient, and durable oxygen evolution reaction (OER) catalysts is critical for improving the efficiency of hydrogen production from water splitting. Herein, we reported a novel OER catalyst composed of NiFe layered double hydroxide (NiFe-LDH) nanosheets on NiCo2O4 nanowires (NiCo2O4@NiFe-LDH) supported on carbon cloth through the hydrothermal method and subsequent electrodeposition. The three-dimension (3D) hierarchical architecture facilitates the diffusion of electrolyte ions and O2 release. Experimental results demonstrate that the electrons transfer from the highly conductive NiCo2O4 nanowires to the NiFe-LDH sheets, which could expedite the charge transfer significantly. Importantly, the tunable adsorption/desorption nature of the oxygenated intermediates was achieved through the local delocalization of spin state at the heterointerface through the bridging O2-. Benefiting from the heterostructure and synergistic effects between different components, the optimized NiCo2O4@NiFe-LDH-2 exhibits excellent OER performance with a low overpotential of 270 mV at 50 mA cm−2, a small Tafel slope of 74 mV dec−1 and a good durability for 25 h in 1 M KOH. This work provides a novel approach to fabricate advanced OER catalysts and is expected to be extended to other materials for energy conversion applications.

2H-MoS2 nanosheets-based binder-free electrode material for supercapacitor

Developing advanced electrode materials for supercapacitors (SCs) has received incredible attention. The suitable electrode for high capacitance and energy density are significant challenges for SCs. This work reports an efficient hydrothermal synthesis of MoS2 nanosheets on carbon cloth (MoS2@CC). The large surface area of the binder-free MoS2@CC electrode provides rich active sites and an improved electrolyte ion diffusion rate. The MoS2@CC electrode exhibits good electrochemical performance by delivering a high specific capacitance of 947 F g−1 at the current density of 1.0 A g−1 and retains an excellent capacitance of 96.5% over 10 000 cycles. The high performance of the MoS2@CC electrode can be clarified through density functional theory (DFT) calculations. The DFT outcomes reveal that the electrode possesses favorable Li-ion intercalation and adsorption properties. The calculated adsorption energy of −0.352 eV at the hollow site shows the high stability of the system. The low energy barrier of path 1 (0.83 eV) easily facilitates Li-ions in the electrode material, which is beneficial for its fast electrochemical performance. The obtained results of the MoS2@CC electrode present improved pseudocapacitive performance, showing a significant possibility for high-performance SCs' application.

Self-doped N, S porous carbon from semi-coking wastewater-based phenolic resin for supercapacitor electrodes.

Contamination of phenolic compounds has devastating effects on the environment. Therefore, its harmless treatment and recycling have received extensive attention. Herein, a novel method for preparing N-S doped phenolic resin (NSPR) from phenols, N and S groups in semi-coking wastewater, and formaldehyde are developed. The KOH is consequently incorporated into the NSPR through simultaneous carbonization and activation in a single step to produce porous carbon material (NSPC). The as-obtained NSPC exhibits a high specific capacitance of 182 F g−1 at 0.5 A g−1, a high energy density of 9.1 Wh kg−1 at a power density of 0.15 kW kg−1, and remarkable cycling stability in aqueous KOH electrolyte. This outstanding electrochemical performance is attributed to its ultrahigh specific surface area (SSA, 2,523 m2 g−1), enormous total pore volume (Vt, 1.30 cm3 g−1), rational pore structure, and N-S heteroatom self-doping (0.76 at% N and 0.914 at% S), which ensures adequate charge storage, rapid electrolyte ion diffusion, and contributed pseudo-capacitance. This work not only provides a facile method for transforming phenolic wastewater into high-value products but also offers a cost-effective and high-performance porous carbon material for supercapacitors.

Decorating cobalt selenide nanoparticles on polypyrrole nanowires as nanocomposite electrodes for hybrid supercapacitors

• PPy@Co 0.85 Se nanocomposites are fabricated by a two-step electrochemical method. • Dispersed Co 0.85 Se nanoparticles are decorated on PPy nanowires growing on Ni foam. • PPy@Co 0.85 Se electrodes demonstrate improved rate capacities and cyclic stability. • The improved charge storage property arises from structural merits of nanocomposites. Cobalt selenide electrode materials for hybrid supercapacitors (HSCs) still suffer from the unsatisfactory rate performance and cyclic stability thanks to their limited electrical conductivity and poor structural stability. To address these issues, we here report on the construction of polypyrrole (PPy)@Co 0.85 Se nanocomposites that grow on Ni foam by a two-step electrochemical synthesis method. In such nanocomposites, well dispersed Co 0.85 Se nanoparticles are decorated on conductive PPy nanowires, which are featured by enhanced electrical conductivity, rich electroactive sites, easy adsorption/desorption and diffusion of electrolyte ions, and good mechanical stability. As a result, the obtained PPy@Co 0.85 Se nanocomposites give a maximum specific capacity of 827 C g −1 at 1 A/g, a capacity retention of 67 % at 20 A/g, and an initial capacity retention of 93 % after 5000 cycles at 10 A/g. Furthermore, a two-electrode HSC device is assembled with PPy@Co 0.85 Se as the positive electrode, which demonstrates an energy density of 51.9 Wh kg −1 at a power density of 812 W kg −1 as well as an initial capacity retention of 96 % after 5000 cycles at 5 A/g. These results showcase a great potential for future application of the synthesized PPy@Co 0.85 Se nanocomposites in HSCs, and our work may provide an efficient strategy for engineering other metal selenide-based electrode materials for HSCs.

Design and synthesis of Co3S4@CoCH/NF for high performance asymmetric supercapacitors

As one of the energy storage devices, supercapacitors (SCs) have the advantages of high-power density, short charging time and excellent cycle stability, and have received widespread attention. Therefore, designing and synthesizing a supercapacitor material with high energy density has become a key factor to promote the development of SCs. In this work, the inter-crosslinked Co 3 S 4 nanosheets which derived from ZIF-67 are successfully loaded on Co 2 (CO 3 )(OH) 2 nanowires (CoCH NWs) can significantly facilitate the diffusion of electrolyte ions and enhance mass/electron transfer. The obtained Co 3 S 4 @CoCH composite grows directly on nickel foam (NF) substrates without binder, which improves the conductivity of Co 3 S 4 @CoCH/NF electrode. Consequently, the obtained Co 3 S 4 @CoCH/NF electrode possesses an excellent capacitance of 2697.1 F g −1 at 2 A g −1 and outstanding rate capability (84.4 % retention at 2–20 A g −1 ). In the three-electrode system, the capacitance retention is 79.8 % after 8000 cycles at a current density of 10 A g −1 . An asymmetric supercapacitor assembled from Co 3 S 4 @CoCH/NF and activated carbon as cathode and anode respectively which has fabulous energy density of 42.2 W h kg −1 at 799.0 W kg −1 and stability (74.0 % retention after 8000 cycles). It improves that Co 3 S 4 @CoCH/NF is a promising cathode material for supercapacitors. • Co 3 S 4 are anchored on Co 2 (CO 3 )(OH) 2 nanowires (CoCH NWs) to form composites and supported on foamed nickel. • Co 3 S 4 @CoCH/NF has excellent specific capacitance and outstanding rate capability. • The introduction of CoCH NWs improves the structure of Co 3 S 4 nanosheet. • Asymmetric supercapacitor Co 3 S 4 @CoCH/NF//AC (activated carbon) exhibits great performance.

Self-assembly of biomass derivatives into multiple heteroatom-doped 3D-interconnected porous carbon for advanced supercapacitors

The rational design of the pore structure of carbon materials is of great significance for solving the low specific capacitance and poor rate performance of supercapacitors. Herein, we propose a multiple heteroatom-doped three-dimensional (3D) interconnected carbon material obtained from the self-assembly of biomass derivatives including chitosan and sodium lignosulfonate with the assistance of boric acid. The amino group of chitosan protonated by boric acid can form electrostatic adsorption and hydrogen bonding with the sulfonic acid group of sodium lignosulfonate to form a carbon network structure. Boric acid also acts as a template, and in combination with KOH activation, further promotes the formation of the hierarchical porous structure, resulting in the as-prepared carbon possessing a high specific surface area of 2700.65 m2 g−1. As the electrode material in 6 M KOH electrolyte, it manifests a decent specific capacitance of 332 F g−1 at 1 A g−1 in the three-electrode system, while the symmetric electrode achieves a high energy density of 17.7 W h kg−1 at 166.4 W kg−1. Moreover, the contribution rate of the fast and slow kinetic process, as well as the fast diffusion of electrolyte ions are deeply revealed through the ultrafast charge/discharge and the ion diffusion kinetics analysis, respectively. The symmetric electrode in PVA/KOH gel electrolyte maintains 97% capacitance retention and 100% Coulombic efficiency over 10000 cycles, indicating excellent cycling stability.

Efficient dual conductive network based on layered double hydroxide nanospheres and nanosheets anchored in N-carbon nanofibers for asymmetric supercapacitors

A green electrode material with dual conductive networks via electrospinning with carbonization and co-precipitation method is constructed. Nitrogen-based carbon nanofiber network (CCP-N) is used as the inner-conductive, electrochemical-active substrate and flexible skeleton. The Co Ni layered double hydroxide (Co Ni LDH) nanosheets and flower-like nanospheres, which randomly and closely covering the surface of CCP-N, respectively, just as the fungus grow on trunks in nature, is regarded as outer-conductive and active substance collector in order to provide abundant active centers, sufficient reaction interface to advance fast electrolyte ions diffusion and electrons transport. Furthermore, the growth process of Co Ni LDH on CCP-N is observed by controlling growth time and the Co/Ni ratio of the precursor solution. It is found that the optimal Co/Ni ratio was 2:1, while that optimal growth time is 12 h. The specific capacitance of Co Ni LDH@CCP-N electrode reaches 1319.4 F g-1 at 1 A g-1. The assembled asymmetric supercapacitor device (CCP-N @ Co Ni LDH//CCP-N) possesses a high energy density of 48.1 W h kg-1 at power density of 576.8 W kg-1, excellent cycling stability of 82.2% retention after 10,000 cycles. The results clearly indicate the Co Ni LDH@CCP-N materials have enormously potential in energy storage. This work puts forward a novel strategy for the design and fabrication of green and advanced supercapacitors materials with high power density and energy density.

Hydrothermal synthesis of layered NiS2/Ti3C2Tx composite electrode for supercapacitors

MXene shows potential to be used as electrodes in energy storage devices due to its unusual layered structure. MXene-based electrodes can store high rate faradaic pseudocapacitive energy because of their high surface area, metallic conductivity, thermal/chemical stability, and quick surface redox reactions. We present a hierarchy of NiS2/MXene nanohybrids made using a simple and low cost hydrothermal method. The strong interfacial connection and good electronic coupling between the NiS2 nanocube and MXene nanoplates improve structural stability and electrical conductivity as well as the electrolyte ion diffusion kinetics. Therefore, the obtained battery-type NiS2/MXene composite electrodes delivered 72.0 mAh g−1 at a current density of 1 A g−1 with high cycle stability in 1 M KOH electrolyte, and the fabricated asymmetric supercapacitor (ACS) demonstrates energy densities of 15.4 Wh kg−1 at power density of 351.6 W kg−1. It elucidates the mechanism and strategy for the development of MXene-based nanohybrid materials for electrochemical energy storage devices.

Alleviating the self-discharge and enhancing the polysulphides conversion kinetics with LaCO3OH nanocrystals decorated hierarchical porous carbon

Lithium-sulfur (Li-S) batteries have been recognized as one of the most promising energy storage devices due to their ultrahigh energy density of 2600 Wh kg−1. However, their practical implementation is greatly impeded by the sluggish sulfur conversion kinetics, detrimental “shuttle effect” and severe self-discharge. In this work, LaCO3OH nanocrystals decorated nitrogen-doped carbon nanosheet arrays (MNCS-La) are fabricated via an etching-embedding method, which is further applied as an advanced sulfur reservoir for Li-S batteries. The hierarchical porous architecture of carbon nanosheet arrays provides a huge pore volume, which not only buffers the volume fluctuation of active materials during the discharge–charge process, but also facilitates the electrolyte infiltration and ion diffusion. More importantly, the monodispersed LaCO3OH nanocrystals inhibit the shuttle effect and self-discharge by forming a strong La-S bond with lithium polysulfides (LiPSs) and simultaneously enhance the electrochemical conversion kinetics. Attributed to these synergistic features, the sulfur electrodes based on MNCS-La achieve enhanced electrochemical performance, such as an initial discharge capacity of 1230 mAh/g at 0.2 C and a low capacity attenuation of 0.048% per cycle after 1000 cycles at 1 C. This work provides a feasible structural design of host for the applications of Li-S batteries and calls more attention to lanthanide metals-based composite materials.

High areal energy density micro-supercapacitors from structure-engineered graphene electrodes via self-sacrificing template

The restacking issue between graphene sheets seriously affects the ionic accessibility into the graphene electrodes, resulting in the low energy storage capacity of graphene-based microsupercapacitors. However, improving electrolyte accessibility by constructing porous structure to suppress graphene restacking generally decreases its electrical conductivity. Therefore, taking into account both electron transport and electrolyte ion diffusion in the process of constructing porous structures to solve the restacking issue is the key to improve the electrochemical performance of graphene based micro-supercapacitors. Herein, a facile and efficient self-sacrificing template route is proposed to construct structure-tailored graphene electrodes with balanced electrolyte ions and electron transportation for all-solid-state flexible MSCs. In this route, ethyl cellulose helps graphene evenly dispersed in terpineol to form printable ink, and also acts as self-sacrificing template to rationally tune porous structure during post-processing of the printed electrode. Because of the increasing accessibility of electrolyte ions as well as the enhanced electrical conductivity in the fabricated porous graphene electrode, the MSCs deliver high areal energy density of 2.68 μWh cm−2 and high capacitance retention of 89 % when the current density increased from 0.05 to 0.4 mA cm−2. The devices also exhibit outstanding cycle stability and good mechanical stability. This work demonstrates a simple strategy to construct graphene electrodes for MSCs with high areal energy density.

Enhancing structural and cycle stability of Prussian blue cathode materials for calcium-ion batteries by introducing divalent Fe

Calcium-ion batteries (CIBs) have been of interest for rechargeable batteries due to their high energy density and fast ion diffusion in liquid electrolyte originated from the divalence and low charge/radius ratio of Ca ion. However, exploring high performance cathode materials for CIBs is very challenging. In this work, divalent Fe ions are introduced into copper hexacyanoferrate (CuHCF) to construct a new Prussian blue cathode material rich of Fe2+ by using K4Fe(CN)6 as the precursor instead of K3Fe(CN)6. The Fe2+ ions at low-spin state can improve the structural stability of CuHCF during Ca ions extraction and insertion processes effectively. It is found that the lattice parameter change of CuHCF is only 0.13 % during charge and discharge, much less than the CuHCF with Fe3+. X-ray absorption spectroscopy indicates that the charge compensation of CuHCF(Fe2+) is mainly contributed by Fe2+/Fe3+ redox couple. The octahedral distortion in CuHCF is also suppressed effectively. As a result, the CuHCF(Fe2+) cathode can deliver a reversible capacity of 54.5 mAh/g at 20 mA g−1 with a high capacity retention of 90.43 % after 1000 cycles.

Functionalized and Chemically Exfoliated Molybdenum Oxide Nanosheets As Hybrid Electrodes for High Energy Density Supercapacitors

Energy storage systems are critical for regulating and implementing intermittent renewable resources. In addition, the fast development of energy storage systems accelerated the development of electric vehicles. Supercapacitors' unique properties such as high energy storage, high power output, and varied operational range shall allow them to close the gap between batteries and conventional capacitors.1 In the last few decades, enormous efforts were exalted to enhance the supercapacitors' performance by developing new electrode materials that have a structure with an easy ion diffusion path and a high electrochemical surface area.2 In this work, modified molybdenum oxide (MoOx) nanocomposites have been prepared using a facile hydrothermal-aided process, resulting in 3-dimensional (3D) crumpled MoOx nanosheets intercalated with sulfanilamide (SA) or Adenine (Ad). The intercalation of SA or Ad prevented the aggregation of the MoOx nanosheets and allowed the diffusion of electrolyte ions into the MoOx layers. The synthesized MoOx nanocomposites electrodes exhibited a high specific capacitance at 2 A/g and high stability at 10 A/g over 3000 cycles. The assembled symmetric supercapacitor device consisting of MoOx nanocomposites delivered specific energy and specific power of 66.74 Wh/kg and 3 kW/kg, respectively at 3 A/g, demonstrating a high potential for use in constructing high-performance supercapacitors.

Fabricating of N/O-codoping porous carbon interpenetrating networks for high energy aqueous supercapacitor

Developing high-capacity carbon electrodes with an enlarged potential window is a significant strategy for high energy aqueous supercapacitor. However, engineering synthesis of hierarchical porous carbon networks with the broad electrochemical stability window remains a great challenge. In this work, N/O codoped hierarchical porous carbon networks (MPBx) are constructed based on Schiff-base reaction for the purpose of excellent charge storage and kinetics of electrolyte ions diffusion in “water-in-salt” (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI) electrolyte. When fabricated as an electrode for symmetrical supercapacitor, the 2.25 V LiTFSI-based supercapacitor exploits a superior specific capacitance (180 F g−1, 0.5 A g−1) and an exceptional energy delivery of 31.7 W h kg−1 at the corresponding power output of 562 W kg−1, together with an impressive cycling stability with 93.8 % capacitance retention after 10,000 continuous cycles. The improvement in the superb electrochemical performance can be attributed to the excellent conductive networks, high ion-adsorption area (1902 m2 g−1), interpenetrating porous architecture (macro-, meso- and micropore) and high-level heteroatoms dopants (N: 2.56 at.%, O: 11.46 at.%). The excellent electrochemical performances demonstrate that the carbon networks hold great prospects for promoting the energy delivery of aqueous supercapacitors.