Construction of NiCo_(2)O_(4) nanoflake arrays on cellulose-derived carbon nanofibers as a freestanding electrode for high-performance supercapacitors

Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional electrospinning.Herein,we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly,pre-oxidation and high-temperature carbonization(1600℃),which display a superior electrical conductivity of 31.2 S·cm^(-1)and larger specific surface area of 35.61 m^(2)·g^(-1)than that of the polyacrylonitrile-based carbon nanofibers(electrical conductivity of 18.5 S·cm^(-1),specific surface area of 12 m^(2)·g^(-1).The NiCo_(2)O_(4)nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination method.The as-prepared cellulose-based carbon nanofibers/NiCo_(2)O_(4)nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g^(-1)at 1 A·g^(-1)and a good cycling stability with 90.84%capacitance retention after 3000 times at 10 A·g^(-1).Furthermore,the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo_(2)O_(4)deliver a high energy density of 62 W·h·kg(-1) at a power density of 1200 W·kg^(-1).Six all-solid-state symmetric supercapacitors in series can also power a‘DHU’logo consisted of 36 light emitting diodes,confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices.

XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro fiber networks as freestanding cathode for LieS batteries

Lithium-sulfur(Lisingle bondS)batteries are considered as one of the most promising high-energy storage devices due to the high theoretical capacity(1675 mA·h·g^(-1))and large energy density(2600 W·h·kg^(-1)).However,the poor conductivity of sulfur and“shuttle effect”of soluble polysulfide intermediates limit practical applications of Lisingle bondS batteries.Herein,four kinds of carbon sub-micro fibers with different structures were designed and prepared,the effect of structure on Lisingle bondS battery was studied.On this basis,the XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro carbon fibers(HMCMFs)were prepared by electrospinning and carbonization.The HMCMFs can not only supply nanopores for relieving the expansion of sulfur but also served as high conductivity freestanding substrate for sulfur loading,meanwhile the decorated XO(X=Ti,Mn)can provide powerful chemical adsorption to polysulfide intermediates and limit“shuttle effect”Therefore,the TiO-HMCMFs/S composite shows high specific capacity of 900 mA·h·g^(-1)and maintain stable specific capacities up to∼600 mA·h·g^(-1)over 300 cycles at 0.1 A·g^(-1).This work offers a facile method to build efficient sulfur cathode to acquire Lisingle bondS batteries with high performance.

Carbon‑Based Fibers: Fabrication, Characterization and Application

In recent years,the carbon-based fibers(CBFs)including carbon fibers,carbon nanotube fibers and graphene fibers have received extensive attention due to excellent thermal,electrical and mechanical properties.Here,the current status of CBFs is reviewed from the following aspects:sprecursors,preparation,performance and application.The precursor systems including acrylonitrile copolymers,pitch,cellulose and lignin,carbon nanotube,graphene and other rare synthetic polymeric precursors.The relationship of preparation method and performance of CBFs is presented.In addition,this review gives the overview of application and future development of CBFs.

Fabrication of 3D ordered needle-like polyaniline@hollow carbon nanofibers composites for flexible supercapacitors

Carbon nanofiber-based supercapacitors have broad prospects in powering wearable electronics owing to their high specific capacity,fast charge/discharge process,along with long-cycling life.Herein,a poly(ac rylo n it rile-co-β-methyl hydrogen itaconate) copolymer was prepared and used to synthesize flexible hollow carbon nanofibers(HCNFs) via an electrospinning method without breaking after multiple bending.Subsequently,the inner and outer surfaces of HCNFs were evenly covered with ordered needlelike polyaniline(PANI) through in-situ polymerization methods to obtain three-dimensional flexible HCNFs/PANI composites,which exhibited a high capacity 1196.7 F/g at 1 A/g and good cycling stability(90.1% retention at 5 A/g after 3000 cycles).The symmetrical supercapacitor based on the HCNFs/PANI composites also delive red an outsta nding electrochemical performance with high energy/power density(60.28 Wh/kg at 1000 W/kg) and superior cycling durability(90% capacitance retention after at 5 A/g3000 cycles),which confirmed that the HCNFs/PANI composites had a wide application potential in flexible energy storage devices.

Hollow multi-nanochannel carbon nanofiber/MoS_(2)nanoflower composites as binder-free lithium-ion battery anodes with high capacity and ultralong-cycle life at large current density

The electrode materials with high pseudocapacitance can enhance the rate capability and cycling stability of lithium-ion storage devices.Herein,we fabricated MoS_(2)nanoflowers with ultra-large interlayer spacing on N-doped hollow multi-nanochannel carbon nanofibers(F_(2)-MoS_(2)/NHMCFs)as freestanding binder-free anodes for lithium-ion batteries(LIBs).The ultra-large interlayer spacing(0.78~1.11 nm)of MoS_(2)nanoflowers can not only reduce the internal resistance,but also increase accessible active surface area,which ensures the fast Li+intercalation and deintercalation.The NHMCFs with hollow and multi-nanochannel structure can accommodate the large internal strain and volume change during lithiation/delithiation process,it is beneficial to improving the cycling stability of LIBs.Benefiting from the above combined structure merits,the F_(2)-MoS_(2)/NHMCFs electrodes deliver a high rate capability 832 mA h g^(-1)at 10 A g^(-1)and ultralong cycling stability with 99.29 and 91.60%capacity retention at 10 A g^(-1)after 1000 and 2000 cycles,respectively.It is one of the largest capacities and best cycling stability at10 A g^(-1)ever reported to date,indicating the freestanding F2-MoS_(2)/NHMCFs electrodes have potential applications in high power density LIBs.