Bimetallic zeolitic imidazolate framework-derived substrate-free anode with superior cyclability for high-capacity lithium-ion batteries

Freestanding carbon nanofibers loaded with bimetallic hollow nanocage structures were synthesized.The nanocages inherited the rhombic dodecahedral morphology of the zeolitic imidazolate framework(ZIF)precursors,ZIF-8 and ZIF-67.As anode materials for lithium-ion batteries(LIBs),the bimetallic nanocage-loaded freestanding carbon nanofibers effectively buffered volume expansions and alleviated pulverization through their different reduction and oxidation potentials.The higher capacities of the composite anodes arose via the formation of the Li_(x)Zn alloy and Li_(2)O by Zn and Co ions,respectively,and the enhanced conductivity conferred by the carbon nanofibers.A synergistic effect of the composite components toward the strong electrochemical performance(688 m A h·g^(-1)at 1200 m A·g^(-1))of the bimetallic nanocage-loaded fibers was demonstrated through the superior long-term stability of the anode(1048 m A h·g^(-1)after 300 cycles at 100 m A·g^(-1)),suggesting that the fabricated anode can be a promising material for use in portable LIBs.

Supersonically sprayed self-aligne d rGO nanosheets and ZnO/ZnMn_(2)O_(4)nanowires for high-energy and high-power-density supercapacitors

Core-shell-type bimetallic oxide and carbon composites comprising zinc oxide(ZnO)nanospheres and zinc manganese oxide(ZnMn_(2)O_(4))nanowires were produced by a hydrothermal method,and supersoni-cally sprayed together with reduced graphene oxide(rGO)nanosheets onto Ni foil to fabricate flexible su-percapacitors.The supersonic impact facilitated the exfoliation of the rGO nanosheets,thereby increasing the surface area and adhesion of the composite particles to the substrate.The rGO nanosheets were vertically aligned during the supersonic impact and formed localized zones,enabling optimal accommodation of the ZnO/ZnMn_(2)O_(4)particles.This localization,with the addition of rGO,reduced the agglomeration of ZnO/ZnMn_(2)O_(4)particles.The molar concentration of MnSO_(4)used in the synthesis of ZnO/ZnMn_(2)O_(4)was varied from 0.05 to 0.15 mol/L to determine the optimal MnSO_(4)concentration that would result in the highest energy storage capacitance.The unique nanostructure of ZnO/ZnMn_(2)O_(4)and the self-alignment of rGO sheets facilitated a favorable environment for high energy storage capability with a specific capaci-tance of 276.3 mF·cm^(−2)at a current density of 0.5 mA·cm^(−2)and an energy density of 98.2μWh·cm^(−2)at a power density of 1600μW·cm^(−2).The width of the potential window was increased to 1.2 V,imply-ing a significant increase in the energy storage capability of the supercapacitor.Capacitance retention of 88%was achieved after 10,000 charge/discharge cycles for the supercapacitor fabricated using an optimal MnSO_(4)concentration(0.10 mol/L)during the composite synthesis.

Reduced graphene oxide supersonically sprayed on wearable fabric and decorated with iron oxide for supercapacitor applications

We demonstrate the fabrication of wearable supercapacitor electrodes.The electrodes were applied to wearable fabric by supersonically spraying the fabric with reduced graphene oxide(r GO)followed by decoration with iron oxide(Fe_(2)O_(3))nanoparticles via a hydrothermal process.The integration of iron oxide with r GO flakes on wearable fabric demonstrates immense potential for applications in high-energystorage devices.The synergetic impact of the intermingled r GO flakes and Fe_(2)O_(3) nanoparticles enhances the charge transport within the composite electrode,ultimately improving the overall electrochemical performance.Taking advantage of the porous nature of the fabric,electrolyte diffusion into the active r GO and Fe_(2)O_(3) materials was significantly enhanced and subsequently increased the electrochemical interfacial activities.The effect of the Fe_(2)O_(3) concentration on the overall electrochemical performance was investigated.The optimal composition yields a specific capacitance of 360 F g^(-1) at a current density of 1 Ag^(-1) with a capacitance retention rate of 89%after 8500 galvanostatic cycles,confirming the long-term stability of the Fe_(2)O_(3)/r GO fabric electrode.