Diffusion Of Electrolyte Ions Research Articles

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.

The Emergence of 2D MXenes Based Zn-Ion Batteries: Recent Development and Prospects.

Rechargeable zinc-ion batteries (ZIBs) with exceptional theoretical capacity have garnered significant interest in large-scale electrochemical energy storage devices due to their low cost, abundant material, inherent safety, high specific energy, and ecofriendly nature. Metal carbides/nitrides, known as MXenes, have emerged as a large family of 2D transition metal carbides or carbonitrides with excellent properties, e.g., high electrical conductivity, large surface functional groups (e.g., F, O, and OH), low energy barriers for the diffusion of electrolyte ions with wide interlayer spaces. After a decade of effort, significant development has been achieved in the synthesis, properties, and applications of MXenes. Thus, it has opened up various exciting opportunities to construct advanced MXene-based nanostructures for ZIBs with excellent specific energy and power. Herein, this review summarizes the advances across multiple synthesis routes, related properties, morphological and structural characteristics, and chemistries of MXenes for ZIBs. The recent development of MXene-based electrodes is introduced, and electrolytes for ZIBs are elucidated in detail. MXene-based rocking chair ZIBs, strategies to enhance the performance of MXene-based cathodes, suppress the dendrites in MXene-based anodes, and MXene-based flexible ZIBs are pointed out. A rational design and modification of the MXenes as well as the production of composites with metal oxides exhibits promise in solving issues and enhancing the electrochemical performance of ZIBs. Finally, the present challenges and future prospects for MXene-based ZIBs are discussed.

Flower-like nickel hydroxide@tea leaf-derived biochar composite for high-performance supercapacitor application

Renewable and sustainable high-performance energy storage devices are desirable to fulfill the demands of next-generation power sources. In this study, we report a flower-like nickel hydroxide/spent tea leaf-derived biochar (NiNF@TBC) composite for high-performance supercapacitor application. The tea leaf-derived biochar (TBC) with a specific surface area of 1340 m2 g−1 is used as the Ni(OH)2 support to fabricate NiNF@TBC composites. The highly porous and hierarchical structure of the as-synthesized NiNF@TBC composite facilitates the electrolyte ion and electron diffusion and transport more readily. As a result, the decrease in diffusion path and the increase in conductivity of NiNF@TBC for energy storage applications. The NiNF@TBC electrode shows excellent electrochemical properties with a specific capacitance of 945 F g−1 at 1 A g−1 in a three-electrode cell and high stability of 95% after 10,000 cycles. Moreover, the symmetric supercapacitor fabricated with NiNF@TBC delivers a specific capacitance of 163 F g−1 in 1 M Na2SO4 solution. The Ragone plot of the symmetric device exhibits energy density in the range of 19 – 58 Wh kg−1 with power density in the scale of 826 – 6321 W kg−1. An excellent long-term cyclic stability of 94% is obtained after 10,000 charge–discharge cycles. Such an excellent performance has demonstrated the feasibility of utilizing agricultural wastes as green carbon sources, which can combine with various metal hydroxides to produce hybrid nanomaterials as a highly potential electrode material for green sustainable supercapacitor applications.

Lattice-strain engineering of CoOOH induced by NiMn-MOF for high-efficiency supercapacitor and water oxidation electrocatalysis

Lattice strain engineering is desirable to accelerate the electrochemical reaction kinetics but still lacks exploration. Here, we have endowed NiMn-MOF@CoOOH with multiple strains, which were introduced by NiMn-MOF. In such hybrid material, the NiMn-MOF not only stabilizes the structure to prevent the material from breaking during the electro-oxidation phase change process but also serves as an anchor point to tightly connect Co ions. The surface of CoOOH undergoes lattice stretching and compression and builds abundant vacancies and dislocations. The multiple lattice strains enable accelerated ion conduction through tensile/compressive strain and introduce additional electrochemically active sites. Regional vacancies and dislocation can change the stoichiometric ratio of some regions, leading to local electric field distortion and electron density redistribution. Moreover, the stacked network structure of the double-layer sheet provides more electrochemical active interfaces for electrochemical reactions, which greatly reduces the ion transport distance and promotes the rapid diffusion of electrolyte ions. The as-obtained NiMn-MOF@CoOOH demonstrates a superb capacity of 1771.4 at 1 A g−1 in supercapacitors. Meanwhile, when facing the water oxidation electrocatalysis reaction, it delivers low overpotentials of 221 mV at 10 mA cm−2 in an alkaline electrolyte. This report provides a novel strategy for lattice strain engineering on advanced materials for sustainable applications.

Rational design and fabrication of one-dimensional hollow cuboid-like FeMoO4 architecture as a high performance electrode for hybrid supercapacitor

The design and progress of extremely efficient electroactive electrode materials with nano-dimensional architecture are the recent focus of hybrid supercapacitors (HSCs). In particular, the one-dimensional hollow micro-/nanostructures have fascinated wide attention in the next generation energy storage materials due to their unique charge transport and storage properties. Herein, we report a facile fabrication of one-dimensional hollow cuboid-like FeMoO4 (FMO) micro-/nanostructures through a simple hydrothermal approach. Further, the as-prepared FeMoO4 (AFMO) and the calcined FeMoO4 (CFMO) materials were comparatively studied to ensure the electrochemical property of the materials. The unique one-dimension hollow cuboid-like architecture facilitates shorten and fast transportation route of charges to decrease the capacitance fading. Further, the extra void space of the CFMO sample due to the calcination process could facilitate easy access for electrolyte ion diffusion within the interior of the electrode materials, thus shortening the electrolyte's diffusion resistance. Besides, the well-ordered structural stability of the CFMO electrodes could improve the rate capability and cyclic durability, which is apparent in the excellent long-term stability of the HSC. Thus, the CFMO micro-/nanostructures exhibit good electrochemical performance with a maximum specific capacitance (Csp) of 493 F g−1 at a current density of 1 A g−1, which is superior to the AFMO materials (332 F g−1 at the same current density of 1 A g−1). Moreover, the constructed HSC (CFMO//AC) exhibits a maximum Csp of 96 F g−1 and also offers a maximum energy density (ED) of 29.89 W h kg−1 at a power density (PD) of 1001.58 W kg−1. In addition, the HSC exhibits excellent long-term cyclic life with 89.62% capacitance retention over 10,000 repeated charge/discharge cycles.

Copolymerization of Aniline, Melamine and p‐Phenylenediamine for Enhanced Pseudocapacitance Hydrogel Supercapacitor Electrodes

AbstractA novel double‐crosslinked 3D network hydrogel, poly(aniline‐co‐p‐phenylenediamine‐co‐melamine) (PD2M4) is synthesized through the chemical oxidative copolymerization of aniline, melamine, and p‐phenylenediamine, and its properties are compared with those of polyaniline (PANI), poly(aniline‐co‐p‐phenylenediamine) (PPDA2), and poly(aniline‐co‐melamine) (PMA4) hydrogels. The morphologies, mechanical properties, and chemical compositions of the hydrogels are investigated by nitrogen physisorption, rheological test, microscopic measurements, and spectroscopic techniques, while electrochemical techniques are used to evaluate their electrochemical performances. In accordance with PANI, PPDA2, and PMA4 hydrogels, the PD2M4 hydrogel exhibited an interconnected long nanofiber structure that encouraged the diffusion of electrolyte ions. Its double‐crosslinked 3D network and high nitrogen‐doping content (6.3 at. %) offered synergistic effects that generated an impressive pseudocapacitance of 657 F g −1 at 0.2 A g−1, a superior rate capability of 72% retention at a high current density of 30 A g−1, and good cyclic stability of 62% after 2000 charge/discharge cycles. The present work, therefore, provides a novel copolymerization strategy for N‐doping and hierarchical network structure to enhance the electrochemical performances of PANI hydrogel electrodes in supercapacitor applications.

Concentration cell powered by a chemically asymmetric membrane: Experiment

Electrochemical cells are a key technology for a sustainable energy future. Here experiments are presented verifying a new type of cell: the asymmetric membrane concentration cell (AMCC). This cell charges using a unique mechanism: its concentration difference is generated internally by a chemically-asymmetric membrane that drives anisotropic diffusion of electrolyte ions, rather than being provided by an external source. This self-charging mechanism confers potential advantages over other cell types, including improved thermodynamic efficiency, compactness, and economy. For this study, custom membranes were developed to concentrate hydrogen and chloride ions; these were installed in single and series arrangements; the solutions from the latter were incorporated into a chloride-ion concentration cell. Experimental results agree well with theoretical predictions developed in a companion article [1]. Based on these findings, suggestions are made for improving the performance of the AMCC.

Bead‐Like Coal‐Derived Carbon Anodes for High Performance Potassium‐Ion Hybrid Capacitors

AbstractThe pursuit of long life, high rate and low‐cost anode materials is of great significance for potassium‐ion hybrid capacitors (PIHCs). Here, the bead‐like coal‐derived carbon films (BCCFs‐800) for PIHCs were synthesized with low‐cost coal as precursor. Benefiting from the well‐designed composite structure, the wettability on the electrode surface was enhanced and the diffusion of electrolyte ions was also facilitated, thereby improving the electrochemical performance of the electrode. A potassium ion hybrid capacitor was fabricated with BCCFs‐800 as battery‐type anode and active carbon as capacitor‐type cathode, and it delivered promising energy and power densities (119 Wh kg−1 at 186 W kg−1 and 2187 W kg−1 at 52 Wh kg−1). The as‐obtained earth‐abundant and high performance electrodes will promote the green and clean utilization of coal and accelerate the development of potassium ion electrochemical storage technology.

Improvement of forming-free threshold switching reliability of CeO2-based selector device by controlling volatile filament formation behaviors

Diffusive memristor-based threshold switching devices are promising candidates for selectors in the crossbar memory architecture. However, the reliability and uniformity of the devices are primary concerns due to uncontrolled diffusion of metal ions in the solid electrolyte of diffusive memristors. In this study, CeO2-based selectors with Ag electrodes were demonstrated to have forming-free threshold switching characteristics. In particular, by inserting an amorphous SiO2 layer in a CeO2-based selector device, we have effectively controlled volatile filament formation that is essential for uniform and reliable switching operations. The inserted SiO2 layer acts as a barrier that could retard the migration of Ag ions and prevents the formation of strong filaments in the solid electrolyte. This enables the bilayer device to have improved uniformity and cyclic endurance. The proposed selector device, Ag/CeO2/SiO2/Pt, showed excellent DC I–V switching cycles (103), high selectivity of 104, good endurance (>104), and narrow distribution of switching voltages. These results would be helpful to implement CeO2-based threshold switching devices as selectors for high-density storage crossbar memory architectures.

Enhanced Ion Diffusion in Flexible Ti3C2TX MXene Film for High‐Performance Supercapacitors

Ti3C2T x MXene is a good candidate of electrode materials for supercapacitors due to its high conductivity and outstanding pseudocapacitance. However, restacking among MXene sheets is inevitable when they are assembled into a freestanding film electrodes, which hinders electrolyte ion diffusion to active sites and results in sluggish energy‐storage kinetics. Herein, the volumetrically expanded ester reaction between ethanol and phosphoric acid is exploited to improve interlayer path within the Ti3C2T x film. These two kinds of molecules jointly intercalate into the interlayer space of the Ti3C2T x film and then react to produce phosphate under heating, leading to an expanded molecular scale but uniform interlayer gallery. The optimized film shows enhancement in both gravimetric and volumetric capacitances along with better rate capability. It exhibits a capacitance of 297 F g−1/965 F cm−3 at 2 mV s−1 and retains 108 F g−1/300 F cm−3 at 200 mV s−1, which are greatly superior to those of the pristine film without the treatments. The assembled symmetric and asymmetric supercapacitors with optimized film structure can deliver an energy density of 6.33 and 7 Wh Kg−1, respectively. Herein, a novel yet simple method to ameliorate restacking of MXene sheets for its better supercapacitor application is demonstrated.

Electrospinning-chemistry strategy for self-supporting perovskite oxide fabric electrodes towards high-capacitance supercapacitors

Perovskite-type oxides are well-known as promising electrode materials toward supercapacitors. We report an electrospinning-chemistry strategy to continuously fabricate perovskite oxide fabric with ribbon morphology. Interestingly, the perovskite oxide fabric exhibits good self-supporting property. Benefiting from the continuous fibrous network structure and large specific surface area (37.2 m2 g−1), the electrolyte ions diffusion in perovskite oxide fabric electrode is rapid, resulting in high mass capacitance of 862F g−1 at 1 A g−1. This work offers an effective electrospinning-chemistry strategy towards perovskite oxide-based fiber electrodes, greatly important for the development of wearable electronics.

Hierarchical ZnCo2O4-ZnO/ZnCo2O4 core-shell microarchitecture as pseudocapacitive material with ultra-high rate capability and enhanced cyclic stability for asymmetric supercapacitors

Compared with materials for electric double layer capacitors, pseudocapacitive electrode materials have the disadvantage of poor cyclic stability, which is expected to be improved via reasonably designing material microarchitecture. In this work, the hierarchical ZnCo2O4-ZnO/ZnCo2O4 core–shell microarchitecture composite was constructed directly on Ni foam by a two-step solvothermal pathway and calcination. In particular, by growing porous ZnCo2O4 nanosheets on the surface of ZnCo2O4-ZnO microsphere, the pseudocapacitance was significantly enhanced. In addition, this superior configuration provided a stable space structure and highly exposed surface/interface with abundant electrochemical reaction sites, to ensure both the long-term cyclic stability and the diffusion and transfer of electrolyte ions in fast redox kinetics. Consequently, the as-prepared pseudocapacitive material possessed a high specific capacity (2487F g−1 at 1 A g−1), ultrahigh rate capability of 2110F g−1 at 20 A g−1, striking pseudocapacitance contribution (∼95% at 1.0 mV s−1), and ultra-long cycle stability (6000 cycles with 93.3% of capacitance retention). Furthermore, the assembled aqueous asymmetric supercapacitor demonstrated a high energy density of 55.46 W h kg−1 at 1500 W kg−1. The overall results offered a promising approach for rationally designing pseudocapacitive electrode materials with abundant surface/interface active sites for high-performance supercapacitors.

Cation-induced Ti3C2Tx MXene hydrogel for capacitive energy storage

To date, Ti3C2Tx MXene has been a promising candidate for energy storage field, however the construction of 3D MXene hydrogel with their inherent hydrophilicity and high conductivity remains a challenge. Herein, a series of Ti3C2Tx MXene hydrogel was fabricated successfully via a facile and fast cation-induced strategy. Typically, the formation of hydrogel is stem from the quick cross-linking of Ti3C2Tx nanosheets, accompanying with the intercalation of high-concentration cation between the layers. Characterization analyses have demonstrated that the cation-induced Ti3C2Tx hydrogel possesses 3D porous structure and controllable basal spacing, which could synergistically facilitate fast diffusion of electrolyte ions and accessibility of electrochemical active sites. Density functional theory (DFT) calculation shows that larger hydrated radii and more intercalated cation are favorable for the expansion of basal spacing thermodynamically. As a result, the excellent capacitance and high rate-capability are both realized in cation-induced Ti3C2Tx hydrogels. Especially, as-synthesized Al-Ti3C2Tx hydrogel delivery a remarkable capacitance of 675F/g at 1 A/g, along with a specific energy density of 46 Wh/kg when the power density is 349 h/kg, which is superior to the previous reported Ti3C2Tx electrodes. Besides, the well-designed H-Ti3C2Tx hydrogel still achieves 206F/g capacitance when the scan rate is up to 1 V/s, and it could withstand 5000 cycles with only 8% loss of capacitance. This work not only illuminates a straightforward way to construct high-performance MXene electrode for capacitive energy storage, but also provides a new guideline over the manipulation of interlayer spacing and morphology of 2D colloid materials.

High performance Flower-Like Mn3O4/rGO composite for supercapacitor applications

• The flower-like Mn 3 O 4 /rGO composite was prepared by a facile one-step solvothermal process. • The as-prepared Mn 3 O 4 /rGO material exhibits a high specific capacitance of 947F g −1 at a current density of 1 A g −1 and excellent capacitance retention of 88.1% after 4000 GCD cycles at 10 A g −1. • The addition of rGO effectively improved the conductivity of Mn 3 O 4 and providing more buffer space for the electrochemical reaction of Mn 3 O 4 , • The flower-like nanostructure allows for more active sites and a shorter electrolyte ion diffusion pathway. Mn 3 O 4 has attracted great interest due to its pseudocapacitive properties, low cost, and environmental friendliness. However, the low conductivity and high-volume expansion limit its application to supercapacitors. In this research, a flower-like Mn 3 O 4 /reduced graphene (rGO) electrode material was obtained by a one-step solvothermal process. The as-prepared Mn 3 O 4 /rGO electrode exhibits a high capacity of 118.375 mAh g −1 at a current density of 1 A g −1 and an excellent cycle ability of 88.1% after 4000 cycles at a current density of 10 A g −1 . The high performance of the Mn 3 O 4 /rGO electrode can be attributed to the hierarchical structure and improved charge transfer capability as well as buffer space for the volume expansion by the addition of rGO. The nanoflower-like structure of Mn 3 O 4 /rGO provides a more active sites and short ion transport pathway during the redox reaction. The results provide an efficient way of improving the electrochemical performance of Mn 3 O 4 and show its great potential in SC applications.

In situ growth of glucose-intercalated LDHs on NiCo2S4 hollow nanospheres to enhance energy storage capacity for hybrid supercapacitors

Layer double hydroxides (LDHs) have been considered ideal material for energy storage owing to their high theoretical capacity. However, the narrow layer spacing of LDHs affects the diffusion of electrolyte ions and the exposure of active atoms. In addition, intrinsic flaws such as low conductivity and poor cycle still restrict the practical application of LDHs. It is urgent to apply modification strategies to effectively activate intrinsic energy storage performance of LDHs. In this work, we designed glucose-intercalated LDHs on the surface of NiCo2S4 hollow nanospheres by in situ growth strategy to prepare NiCo2S4 @NiCo-G-LDH materials. The glucose-intercalated LDHs showed an appropriate layer spacing of 8.9 Å, which minimized the diffusion path of electrolyte ions and accelerated the kinetics of redox reactions. Besides, the introduction of transition metal sulfides (TMSs) has effectively improved the electrical conductivity of the LDHs, thus showing excellent electrochemical performance. Examined as the supercapacitor electrode; the as-prepared NiCo2S4 @NiCo-G-LDH material possesses an ultrahigh specific capacity of 986 C g−1 at 1 A g−1 and a rate capability of 73.1% even at 30 A g−1. Furthermore, the fabricated hybrid supercapacitor device using NiCo2S4 @NiCo-G-LDH as the positive electrode and commercial activated carbon as the negative electrode achieved a competitive energy density of 54.5 Wh kg−1 at a power density of 400.0 W kg−1 and preeminent cycle stability of 88.9% over 10000 cycles.