Suppression strategy for parametrically excited lateral vibration of mass-loaded string

This paper discusses a simple way to suppress the parametrically excited lateral vibration of a mass-loaded string. Supposing that the mass at the lower end of the string is subjected to a vertical harmonic excitation and neglecting the higher order vibration modes, the equation of motion for the mass-loaded string can be represented by a Mathieus equation with cubic nonlinearity. According to the theory of the Mathieus equation, in the mass-loaded string system, when the vertical vibration frequency of the mass approaches twice the natural frequency of the string lateral vibration, once the vertical vibration amplitude of the mass exceeds a critical value, the parametric resonance will occur in the string. To avoid the parametric resonance, a vibration absorber, composed of a thin beam and two mass blocks attached at both sides of the beam symmetrically, is proposed to install with the mass to reduce its vertical vibration, and ultimately suppress the lateral vibration of the string. Such a suppression strategy is finally validated by experiments.

High mass-loading and binder-free flexible vanadium-based oxide cathode for zinc-ion battery via a bridge of MXene

Flexible zinc-ion batteries(ZIBs)are promising power sources for portable devices due to their high safety and low production cost.However,the low mass-loading and limited areal capacity of cathode materials are the major problems blocking the practicability of ZIBs.Herein,a high mass-loading and binder-free flexible vanadium oxide(MCV@CC)cathode with a large areal capacity was fabricated via the bridge effect of MXene.The functional MXene bridge induces the growth of the vanadium oxide active layer on the carbon cloth(CC)flexible substrate.The binder-free cathode can reduce the electrochemically inactive weight of the whole electrode,which enhances the energy density of ZIBs.Consequently,the MCV@CC cathode(mass-loading of∼7 mg cm^(−2))delivers a desirable areal capacity(2.36 mAh cm^(−2))and good cycling stability(capacity retention of 86.1%after 1200 cycles at 10 mA cm^(−2)).Moreover,several ex-situ characterization results indicate that the reaction mechanism upon battery cycling is based on the reversible Zn^(2+)/H^(+)(de)intercalation in the vanadium oxide interlayer.Furthermore,the assembled quasi-solid-state MCV@CC//Zn flexible battery exhibits decent performance at different bending states.Such a bridge effect strategy sheds light on the construction of high mass-loading flexible electrodes for ZIBs applications.

High mass-loadingα-Fe_(2)O_(3)nanoparticles anchored on nitrogen-doped wood carbon for high-energy-density supercapacitor

The trade-off between mass-loading and cycling stability is always a big challenge for iron oxide-based electrodes.Herein,α-Fe_(2)O_(3)nanoparticles uniformly anchored on nitrogen-doped wood carbons with high mass-loading have been synthesized via a facile electrodeposition method accompanied by post-heating treatment.The resultant composite delivers a high specific capacitance of 603 F/g at 0.1 A/g and superior capacitance retention of 85.5%after 10,000 cycles at 10 A/g,indicating excellent long-term cycling stability.Such excellent electrochemical performance can be attributed to the synergistic effects ofα-Fe_(2)O_(3)nanoparticles and the conductive matrix as well as the formation of interfacial Fe-O-C bonding,which enables the composite electrode to provide plenty of accessible redox active sites,sufficient electron transport and electrolyte ions diffusion,and robust interfacial interaction.Consequently,the asymmetrical supercapacitor exhibits a high energy density of 30.3 Wh/kg at 125W/kg,suggesting its great potential forpracticalapplications.

Design of solid-state sodium-ion batteries with high mass-loading cathode by porous-dense bilayer electrolyte

Solid-state sodium-ion batteries with sodium metal anodes possess high safety and reliability,which are considered as a promising candidate for the next generation of energy storage technology.However,poor electronic and ionic conductivities at the interface between electrodes and solid-state electrolytes restrict its practical application.Herein,we demonstrate a β″-Al_(2)O_(3) electrolyte with a vertically porousdense bilayer structure to solve this problem.The carbon-coated vertically porous layer serves as a high mass-loading host for Na_(3)V_(2)(PO_(4))_(3) cathode and provides fast electronically and ionically conductive pathways.In addition,the dense layer is produced to prevent sodium dendrite growth and improve mechanical strength of β″-Al_(2)O_(3) electrolyte.Experimental results show that the cathode loading in vertically porous layer can reach to 8 mg cm^(-2),and the porous-dense bilayer β″-Al_(2)O_(3) electrolyte-based battery exhibits a reversible specific capacity of 87 mAh g^(-1) and a capacity retention of 95.5%over 100 cycles at a current density of 0.1 C,which is superior to that of the traditional dense β″-Al_(2)O_(3) electrolytebased battery.This work based on electrolyte structure design represents an efficient strategy for the development of solid-state sodium-ion batteries with high mass-loading cathode.

Wood-derived biochar as thick electrodes for high-rate performance supercapacitors

Developing effective electrodes with commercial-level active mass-loading(>10 mg cm^(−2))is vital for the practical application of supercapacitors.However,high active mass-loading usually requires thick active mass layer,which severely hinders the ion/electron transport and results in poor capacitive performance.Herein,a self-standing biochar electrode with active mass-loading of ca.40 mg cm^(−2) and thickness of 800μm has been developed from basswood.The basswood was treated with formamide to incorporate N/O in the carbon structure,followed by mild KOH activation to ameliorate the pore size and introduce more O species in the carbon matrix.The as-prepared carbon monoliths possess well conductive carbon skeleton,abundant N/O dopant and 3D porous structure,which are favorable for the ion/electron transport and promoting capacitance performance.The self-standing carbon electrode not only exhibits the maximum areal/mass/volumetric specific capacitance of 5037.5 mF cm^(−2)/172.5 F g^(−1)/63.0 F cm^(−3) at 2 mA cm^(−2)(0.05 A g^(−1)),but also displays excellent rate performance with 76%capacitance retention at 500 mA cm^(−2)(12.5 A g^(−1))in a symmetric supercapacitor,surpassing the state-of-art biomass-based thick carbon electrode.The assembled model can power typical electron devices including a fan,a digital watch and a logo made up of 34 light-emitting diodes for a proper period,revealing its practical application potential.This study not only puts forward a commercial-level high active mass-loading electrode from biomass for supercapacitor,but also bridges the gap between the experimental research and practical application.