Co-precipitation synthesis of nickel cobalt hexacyanoferrate for binder-free high-performance supercapacitor electrodes

Prussian blue analogue with a typical metal-organic framework has been widely used as an electrode material in supercapacitor. In this work, nickel cobalt hexacyanoferrate (Ni₂CoHCF) was grown on nickel foam directly using a simple co-precipitation method. The as-prepared Ni₂CoHCF was tested by transmission electron microscope, scanning electron microscope, X-ray diffraction and X-ray electron energy spectrum. The results showed that Ni₂CoHCF has a unique open face-centered cubic structure. The Ni₂CoHCF was used to set an asymmetric supercapacitor directly. A series of electrochemical tests showed that Ni₂CoHCF had an excellent electrochemical performance. The specific capacitance of the supercapacitor was 585 C g⁻¹ (1300.0 F g⁻¹, 162.5 mAh g⁻¹) at the current density of 0.5 A g⁻¹. After 2000 cycles, it still maintained 85.57% of its initial specific capacitance at the current density of 10 A g⁻¹. The energy density was 30.59 Wh kg⁻¹ at the power density of 378.7 W kg⁻¹. The results show that the supercapacitor constructed by Ni₂CoHCF as an electrode material has high-current charge-discharge capacity, high energy density and long cycle life.     

Facile synthesis of cauliflower-like cobalt-doped Ni3Se2 nanostructures as high-performance cathode materials for aqueous zinc-ion batteries

Ni₃Se₂ and Co-doped Ni₃Se₂ cauliflower-like nanostructures are synthesized using a simple and feasible electrochemical deposition technique. Electrochemical measurements of the resultant nanostructures in 1 M KOH electrolyte solution revealed that the energy storage performance of the cauliflower-like Ni₃Se₂ nanostructures was considerably improved by cobalt doping. Particularly, 6 wt% Co-doped Ni₃Se₂ electrodes exhibited remarkable high specific capacity (179.34 mAh g⁻¹) and excellent stability with capacity retention of 85.9% over 1000 cycles because of their high electrical conductivity. Furthermore, to verify the feasibility of the optimized Co-doped Ni₃Se₂ electrodes for practical applications, Zn ion batteries were constructed by using a Zn plate as the anode and the Co-doped Ni₃Se₂ nanostructures as the cathode. The constructed Zn ion battery achieved high energy and power densities of 199.34 W h kg⁻¹ and 24,510 W kg⁻¹ at the current densities of 1 and 20 A g⁻¹, respectively. In addition, up to 2.2 electrons per formula unit of Ni₃Se₂ were successfully utilized, indicating considerably higher utilization of Ni²⁺/Ni³⁺ redox sites by Co doping the selenite. This work demonstrated an effectual strategy for rational design of highly robust, low-cost flexible electrodes for energy storage devices.     

A comparative study of various polyelectrolyte/nanocomposite electrode combinations in symmetric supercapacitors

A more practical, nontoxic and cheaper electrolyte, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was used to construct supercapacitors with different nanocomposite electrodes. The flexible devices were fabricated including active carbon (AC) electrode and nanocomposites electrodes of AC/nano-silica (nano-SiO₂) and AC/multiwalled carbon nanotubes (MWCNTs) at various weight percentages. The symmetrical cell made from AC electrodes generated a maximum specific capacitance (Cs) of 315 F g⁻¹ at 0.5 A g⁻¹. The energy density of this device was 55.5 Wh kg⁻¹ at a power density of 690 W kg⁻¹. Excellent performance was achieved after 5000 charge-discharge cycles where the supercapacitor maintains 92% of its activity. The energy storage capability of the supercapacitors was also investigated with the addition of nano-SiO₂ and MWCNTs. The Cs of the supercapacitors made with the electrodes AC/nano-SiO₂ (5%, 10%, 25% and 50%) were 172, 228, 247 and 55 F g⁻¹, respectively. Similarly, the capacity of the device including the electrodes of AC/MWCNTs (5%, 10%, 25% and 50%) varied as 191, 244, 93 and 20 F g⁻¹ at 0.5 A g⁻¹. The maximum energy density of the devices having nano-SiO₂ and MWCNT were 44.4 Wh kg⁻¹ and 43.8 Wh kg⁻¹, respectively at a power density of 520 W kg⁻¹. A supercapacitor with certain dimension successfully operated a light-emitting diode (LED).     

Constructing 3D honeycomb-like CoMn2O4 nanoarchitecture on nitrogen-doped graphene coating Ni foam as flexible battery-type electrodes for advanced supercapattery

Reasonable structural design is significant to enable the performance in advanced energy storage devices. Herein, a 3D honeycomb-like CoMn₂O₄ nanoarchitecture (CMO) on nitrogen-doped graphene (NG) coating Ni foam (denoted as Ni/NG/CMO) flexible battery-type electrode was prepared by a facile two-step hydrothermal strategy. The honeycomb-like CoMn₂O₄ arrays not only provide abundant active sites but can also be closely combined with the Ni foam/NG substrate, which enables high reversible capacity and good cycle stability during the long cycles. Benefiting from the compositional features and 3D honeycomb-like nanoarchitecture, the Ni/NG/CMO composite electrode displays improved electrochemical performance with remarkable specific capacity of 527.0C g⁻¹ at a current density of 1 A g⁻¹, outstanding rate capability (338.6C g⁻¹ even at 20 A g⁻¹). In addition, a flexible binder-free supercapattery device has been assembled with Ni/NG/CMO as positive electrode and 3D Ni/NG as negative electrode. Such a supercapattery delivers a high energy density of 44.1 Wh·kg⁻¹ at 992.6 W kg⁻¹, 20.3 Wh·kg⁻¹ at 12430.0 W kg⁻¹ as well as excellent cycling durability. The 3D honeycomb-like Ni/NG/CMO could be considered as an advanced flexible battery-type material for high capacity and energy density fields.     

Facile sonochemical synthesis of strontium phosphate based materials for potential application in supercapattery devices

Among hybrid energy storage devices, supercapattery gained profound research interest due to its ability to give high energy density while maintaining the power density and cyclic stability. Herein, novel low-cost strontium based materials are synthesized by controlled sonochemical method and subsequently calcined at various temperatures. The multiple phases of the material synergistically contributed in the electrochemical charge storage process and give high specific capacity of 220 C g⁻¹ (as-prepared material) and 213 C g⁻¹ (calcined at 200 °C) at 0.5 A g⁻¹. A thorough electrochemical performance of optimized material is investigated as an electrode in asymmetric device. The supercapattery (SP2//AC) exhibits a specific capacity of 103.4 C g⁻¹ at 0.5 A g⁻¹ in the voltage range of 0–1.7 V. Furthermore, supercapattery offers a considerably high specific energy of 24.4 Wh kg⁻¹ at a specific power of 425 W kg⁻¹ and an excellent specific power of 1870 W kg⁻¹ by maintaining specific energy at 14.5 Wh kg⁻¹. In addition, the device retained its specific capacity to 90% after 3000 charging/discharging cycles at 1 A g⁻¹. Strontium based materials could be proposed as an appropriate electrode material for energy storage systems.     

Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

Sulphur-reduced graphene oxide composite with improved electrochemical performance for supercapacitor applications

In this research, carbon nanorods/fibers materials were successfully synthesized from sulphur-reduced graphene oxide (RGO-S) composite by using an improved Hummers' method. Morphological, structural, compositional and textural characterization of the composite material were obtained via scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrochemical performance of the composite sample as a promising supercapacitor electrode revealed a peak specific capacity of 113.8 mAh g⁻¹ at 0.5 A g⁻¹ estimated via GCD curves in 6 M KOH aqueous electrolyte. The half-cell could retain a columbic efficiency of about 98.7% with a corresponding energy efficiency of about 98.5% over 2000 constant charge/discharge cycle at a specific current of 5 A g⁻¹. Remarkably, an assembled hybrid device with carbonized iron cations (C-FP) and the RGO-S composite delivered high energy and power densities of 35.2 Wh kg⁻¹ and 375 W kg⁻¹ at 0.5 A g⁻¹ within a 1.5 V operating potential, respectively. A good cycling stability performance with an energy efficiency of 99% was observed for the device for up to 10,000 cycling at a specific current of 3 A g⁻¹.     

Facile fabrication of comb-like porous NiCo2O4 nanoneedles on Ni foam as an advanced electrode for high-performance supercapacitor

It is very desirable to develop the high-performance supercapacitors to meet the rapidly growing demands for energy-autonomous operation and miniaturization of devices. Herein, comb-like porous NiCo₂O₄ nanoneedles on the three-dimension (3D) nickel foam (NF) have been successfully synthesized through a facile pulsed laser ablation (PLA) approach without any post-treatments and surfactant (denoted as NiCo₂O₄-PLA). The influence of working solution during the fabricated process on the properties of NiCo₂O₄-PLA has been demonstrated in detail in terms of the crystalline structure, specific surface area, morphology, and electrochemical performance. Benefiting from the large specific surface (261.4 m² g⁻¹), abundant pores, and highly conductive scaffold, the NiCo₂O₄-PLA binder-free electrode exhibits an outstanding specific capacitance (1650 F g⁻¹ at a current density of 1 A g⁻¹) and eminent cycling performance (91.78% retention after a 12,000-cycle test at a current density of 10 A g⁻¹) compared with the control samples. The assembled asymmetric device (NiCo₂O₄-PLA//AC-ASCs) delivers the high specific capacitance of 126.9 F g⁻¹ at the current density of 1 A g⁻¹, the large energy density of 56.7 Wh kg⁻¹ at a power density of 756 W kg⁻¹, and the low internal resistance. The attractive results strongly prove that it is an ideal candidate for advanced supercapacitor application.     

Binder-free engineering design of Ni-MOF ultrathin sheet-like grown on PANI@GO decorated nickel foam as an electrode for in hydrogen evolution reaction and asymmetric supercapacitor

In this study, Ni₃(benzene 1,3,5-tricarboxylic acid)@polyaniline-rGO nanocomposite (Ni-MOF@PANI-rGO) is fabricated by a two-step procedure involving polymerization and hydrothermal operations. This nanocomposite-based Ni-MOF was designed for binder-free surface modification of nickel foam (NF). This is offered a novel approach for enhancing the electrochemical performance, and even energy density with a wider operating potential window. An in-situ Ni-MOF was then synthesized on polyaniline@GO (PANI-GO) using an NH-fragment linker and an in-situ hydrothermal technique. The electrochemical behavior of the nanocomposite was studied in asymmetric systems and exhibited outstanding electrochemical performance, high energy density, and power density (73.99 Wh kg⁻¹ at 848.29 W kg⁻¹). The electrode also showed a high specific capacity (1680 C g⁻¹ at 1.0 A g⁻¹) and exceptional cycling stability (92⁒) after 5000 cycles in a three-electrode system. The present results imply a direct application of Ni-MOF@PANI-rGO composite as a bridge performance between supercapacitors and batteries. In addition, the electrocatalyst activity of Ni-MOF@PANI-rGO toward hydrogen evolution reaction (HER) was investigated by linear sweep voltammetry at a scan rate of 10 mV s⁻¹ in 1.0 M KOH. The results showed that Ni-MOF@PAN-rGO acts as a suitable electrocatalyst with the lowest overpotential at 10, 50, and 80 mA cm⁻² and the lowest Tafel slope.     

Facile preparation of SnS2 nanoflowers and nanoplates for the application of high-performance hybrid supercapacitors

In this work, the SnS₂ nanoflowers (SnS₂ NFs) were solvothermally prepared in the solvent of ethanol, while SnS₂ nanoplates (SnS₂ NPs) were obtained through the identical conditions except for the solvent of water. The flowers were assembled with numerous nanosheets with very thin thickness, and the NPs exhibited hexagonal shape. When used as the battery-type electrode material for supercapacitors, the SnS₂ NFs delivered a specific capacity of as high as 264.4 C g^?1 at 1 A g^?1, which was higher than the 201.6 C g^?1 of SnS₂ NPs. Furthermore, a hybrid supercapacitor (HSC) was assembled with the SnS₂ as positive electrode and activated carbon (AC) as negative electrode, respectively. The SnS₂ NFs//AC HSC exhibited a high energy density of 28.1 Wh kg^?1 at 904.3 W kg^?1, which was higher than the 24.2 Wh kg^?1 at 844.3 W kg^?1 of SnS₂ NPs//AC HSC. Especially, when the power density was enhanced to the highest value of 8666.8 W kg^?1, the NFs-based device could still hold 20.4 Wh kg^?1. In addition, both HSC devices showed an excellent cycling stability after 5000 cycles at 5 A g^?1. The present method is simple and can be extended to the preparation of other transition metal sulfides (TMSs)-based electrode materials with brilliant electrochemical performance for supercapacitors.     

A new Co-ZIF derived nanoporous cobalt-rich carbons with high-potential-window as high-performance electrodes for supercapacitors

In this work, a Co-ZIF material and the derived nanoporous cobalt-rich carbons by direct carbonization of this Co-ZIF material were synthesized and used as electrode materials for supercapacitors. This ZIF material exhibited a high specific capacitance of 160.3 F g⁻¹ at 0.5 A g⁻¹, an excellent rate capability (73.72 F g⁻¹ at 10 A g⁻¹), and a good cycling stability with 100% of its initials specific capacitance after 8000 cycles. In addition, the obtained derived nanoporous carbons displayed ideal capacitor behaviors and were promising electroactive materials for supercapacitors at low current density. The nanoporous carbon obtained at 650 °C possessed a highest specific capacitance of 393 F g⁻¹ at 0.5 A g⁻¹ and a wide potential application range of −1.0–0.33 V. In addition, a symmetric supercapacitor device consisting of Z-C-650 and activated carbon exhibited a maximum energy density of 61.23 Wh Kg⁻¹ at a power density of 700 W kg⁻¹ and predicted that Z-C-650 could be used as a potential energy storage material.     

High-performance hybrid supercapacitor based on the porous copper cobaltite/cupric oxide nanosheets as a battery-type positive electrode material

In this work, CuCo₂O₄/CuO nanosheets (NSs) and CuCo₂O₄ oblique prisms (OPs) were synthesized at 130 °C with different amounts of hexamethyltetramine (HMTA) and reaction time through a hydrothermal method, and followed by an annealing treatment of precursors in air. The CuCo₂O₄/CuO NSs with 40 nm in thickness possessed a large specific surface area of 43.34 m² g⁻¹ and a mean pore size of 18.14 nm. The electrochemical tests revealed that the CuCo₂O₄/CuO NSs were belonged to the battery-type electrode material and exhibited a specific capacity of 395.55 C g⁻¹ at the current density of 1 A g⁻¹, higher than 258.16 C g⁻¹ for CuCo₂O₄ OPs. A hybrid supercapacitor (HSC) was assembled with activated carbon (AC) as negative electrode and CuCo₂O₄-based materials as positive electrode. The CuCo₂O₄/CuO NSs//AC HSC exhibited a high energy density of 30.18 Wh kg⁻¹ at a power density of 869.62 W kg⁻¹, and showed a fantastic cycling performance with 105.22% capacity retention over 5000 cycles. In contrast, the CuCo₂O₄ OPs//AC HSC delivered an energy density 26.27 Wh kg⁻¹ at 916.74 W kg⁻¹. These impressive electrochemical properties indicate that CuCo₂O₄/CuO NSs may serve as a promising electrode material for the highly capable hybrid supercapacitors in the near future.     

Walnut shell-derived hierarchical porous carbon with high performances for electrocatalytic hydrogen evolution and symmetry supercapacitors

Walnut Shell-derived hierarchical porous carbon has been successfully synthesized by the efficient KOH activation process. The hierarchical porous carbon material activated at 600 °C, has the specific micropore area of 1037.31 m² g⁻¹ and micropore volume of 0.51 cm³ g⁻¹, which leads to have electrochemical performances of the hydrogen evolution reaction (HER) and supercapacitors. Specifically, as the hydrogen evolution reaction electrocatalyst, the walnut shell-derived carbon material activated at 600 °C exhibits a lower onset potential of 6.00 mV, a smaller Tafel slope of 69.76 mV dec⁻¹ and outstanding stability above long-term cycling. As a supercapacitor electrode material, the sample possesses specific capacitance of 262.74 F g⁻¹ at 0.5 A g⁻¹, the remarkable rate capability of 224.60 F g⁻¹ at even 10 A g⁻¹ and good long-term stability. A symmetric supercapacitor shows the highly energy density of 7.97 Wh kg⁻¹ at a power density of 180.80 W kg⁻¹. This novel and low-cost biomass material is very promising for the electrocatalytic water splitting and supercapacitors.     

Bio-enzymatic synthesis of nitrogen-doped porous carbon/SnO2/carbon microspheres as high-performance composite materials for lithium-ion and sodium-ion batteries

In this study, a nitrogen-doped 3D porous starch-derived carbon/SnO₂/carbon (PSC/SnO₂/C) composite is synthesized with porous starch as a carbon source by biological enzymatic hydrolysis. Compared with the traditional complex acid-base reagent method, the biological enzymatic method is more environmentally friendly and economical, and it can also naturally introduce nitrogen sources and dope the carbon layer. Many mesoporous nanostructures provide enough buffer space and promote the ions' and electrons’ transmission rate. The formation of the Sn–O–C bond between SnO₂ and carbon ensures the stability of the structure. As a result, the PSC/SnO₂/C composite exhibits a high initial discharge capacity (1802 mAhg⁻¹ at 0.2 A g⁻¹ for LIBs and 549 mAh g⁻¹ at 0.1 A g⁻¹ for SIBs) and good cycle stability (701 mAh g⁻¹ at 0.2 A g⁻¹ after 100 cycles for LIBs and 271 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles for SIBs). This synthesis method can prepare other energy storage systems such as fuel cells, supercapacitors, and metal ion batteries.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

Hybrid high performance supercapacitor based on zeolitic imidazolate frameworks-67-derived nano-structure NiCo2S4

In this work, NiCo₂S₄, nickel-cobalt layered double hydroxides (NiCo-LDH) and CoS₂ electrodes are successfully prepared by using ZIF-67 as the precursor, the results show that NiCo-LDH and NiCo₂S₄ are nano-flower-like structures and CoS₂ exhibits a nano-cage structure. The electrochemical properties of the hybrid supercapacitor assembled with NiCo₂S₄ and activated carbon (AC) as electrodes were tested. As the positive electrode of NiCo₂S₄//AC hybrid supercapacitor, the NiCo₂S₄ electrode has the largest specific capacity of 2934 mAh g^?1 at a current density of 1 A g^?1. The NiCo₂S₄//AC capacitor generates the highest energy density of 38.8 Wh kg^?1 when the power density is 993.0 W kg^?1 and has a nice cycling performance with a capacity retention rate of 81.2% after 10,000 cycles at 5 A g^?1.     

ZnMn2O4/milk-derived Carbon hybrids with enhanced Lithium storage capability

One of the effective ways to improve the conductivity and structural stability of binary metal oxide nanostructures is to tightly composite them with nano-carbon materials with excellent conductivity. However, the introduction of low density carbon materials also reduces the energy density of batteries. Therefore, we provides a new idea to enhance the lithium storage performance of carbon/binary transition metal oxide anode materials by multi-element co-doping carbon. ZnMn₂O₄ provides high lithium storage capacity; non-metallic heteroatoms in milk-derived carbon greatly improve the conductivity of carbon materials; metal heteroatoms in milk-derived carbon increase the density of carbon materials. Multicomponent co-doping carbon can build up the mass specific capacity, ratio performance, cyclic life and mechanical properties of binary metal oxides/porous carbon nanocomposites. As the anode materials of lithium-ion batteries, the ZnMn₂O₄/MC (milk-derived carbon) hybrids deliver a high reversible capacity of 1352 mAh g⁻¹ after 400 cycles at 0.1 A g⁻¹, and a remarkable long-term cyclability with 635 mAh g⁻¹ after 300 cycles at 1.0 A g⁻¹.     

Fabrication of a ternary PANI@Fe3O4@CFs nanocomposite as a high performance electrode for solid-state supercapacitors

In this work, a solid-state high performance supercapacitor is fabricated based on a ternary polyaniline@Fe₃O₄@carbon fibers nanocomposite. To prepare the polyaniline@Fe₃O₄@carbon fibers electrodes, a two-step method including electrophoretic deposition of Fe₃O₄ nanoparticles on carbon fibres followed by an in situ polymerization process of polyaniline is utilized. The results show that the polyaniline@Fe₃O₄@carbon fibers nanocomposite with a layer by layer microstructure is successfully formed. The fabricated nanocomposite represents a specific surface area of 3.12 m² g⁻¹. The electrochemical measurements in a three-electrode configuration reveals a high specific capacitance of 245.5 F g⁻¹ at 0.5 A g⁻¹ and an excellent cycle stability (82.44% after 1000 cycle) of the polyaniline@Fe₃O₄@carbon fibers electrode. The as-fabricated solid-state supercapacitor based on the polyaniline@Fe₃O₄@carbon fiber nanocomposite cloth with a surface area of 25 cm² powers up a blue light-emitting diode for 4 min and delivers a high energy density of 78.6 Wh.kg⁻¹ at a power density of 1047.5 W kg⁻¹.     

ZnSe/CoSe/NCDPH composites as anode materials for lithium ion batteries with high capacity and long cycle

In this paper, dopamine hydrochloride (DPH) is introduced to synthesize ZIF-8@ZIF-67@DPH in the preparation of ZIF-8@ZIF-67. ZnSe/CoSe/NC_DPH (N-doped carbon) composites are calcined in a high-temperature inert atmosphere with ZIF-8@ZIF-67@DPH as the precursor, selenium powder as the selenium source. ZnSe/CoSe/NC_DPH has high discharge specific capacity, good cycle stability and outstanding rate performance. The first discharge capacity of ZnSe/CoSe/NC_DPH is 1616.6 mAh g⁻¹ at the current density of 0.1 A g⁻¹, and the reversible capacity remains at 1214.2 mAh g⁻¹ after 100 cycles, the reversible capacity is 416.7 mAh g⁻¹ after 1000 cycles at 1 A g⁻¹. Therefore, ZnSe/CoSe/NC_DPH composites provide a new step for the research and synthesis of new stable, high-capacity, and safe high-performance lithium ion batteries. The bimetallic selenide composites not only have bimetallic active sites, but also can form synergistic effect between different metal phases, which can effectively reduce the capacity attenuation caused by volume expansion and reactive stress enrichment during lithium storage of metal oxide anode materials. Meanwhile, N-doped carbon can improve the conductivity and provide more active sites to store lithium, thus improving its lithium storage capacity.     

Yuba-like porous carbon microrods derived from celosia cristata for high-performance supercapacitors and efficient oxygen reduction electrocatalysts

Here, a novel yuba-like porous carbon microrod is prepared via a simple and facile strategy by using the fluffy fibers of celosia cristata petals (FCCP) as the raw material. The optimized carbon microrod (FCCP-CM-900) possesses unique yuba-like structure, high specific surface area (1680 m² g⁻¹) and large pore volume (0.98 cm³ g⁻¹), and effective nitrogen (∼4.52 at.%) and oxygen (∼5.49 at.%) doping, which can enhance the wettability and conductivity (7.9 S cm⁻¹). As the electrode material for supercapacitor, FCCP-CM-900-based supercapacitor presents high specific capacitance (314.5 F g⁻¹ at 0.5 A g⁻¹) in 6.0 M KOH aqueous electrolyte. The FCCP-CM-900-based symmetrical supercapacitor displays high energy density (18.6 Wh kg⁻¹ at 233.4 W kg⁻¹) and outstanding cycling stability (98% capacitance retention after 10,000 cycles) in 1.0 M Na₂SO₄ electrolyte. In addition, served as oxygen reduction electrocatalyst, the FCCP-CM-900 also exhibits excellent catalytic activity, good durability, together with high methanol tolerance in alkaline electrolyte, which makes it a highly efficient air cathode material toward zinc–air cell.