| Recently,the electronic devices are developping rapidly toward flexible and portable direction.To meet their demands,the persuit of advanced flexible energy conversion and storage devices has become the research hot spot in energy field.Due to the high power density and high energy density,supercapacitors and lithium-sulfur battery have received tremendous attention and are recognized as two promising energy suppliers.However,their electrodes are fabricated by the traditional slurry-coating method,which results in heavy weight and high brittleness,and therefore,making them unapplicable power supplier for flexible electronics.Thus,it is urgent to develop flexible and lightweight electrode materials with high energy density.We fabricate a flexible carbon film with high surface area,excellent electrical conductivity and hierarchical porous structure through combining the high surface area material-metal organic frameworks(MOFs)with high electronic conductorcarbon nanotubes(CNTs).This work offers a facile and customized strategy to fabricate flexbile carbon electrode with high energy density.The main contents and results are as follows:(1)HKUST-1/CNT composite films,as the carbonization precursor,were fabricated via vacuum filtration and solid precursor assisted-confinement conversion process.The porous structure of the HKUST-1/CNT based carbon film(HPCF)can be adjusted by changing the carbonization temperature.The as-prepared HPCF films were directly used as the supercapacitor electrode without adding conductive agents or polymer binder.The electrochemical tests showed that the best electrochemical performance was achieved when the mass ratios of the precursor was 40/1 and the pyrolysis temperature was 800 ?.The prepared HPCF demonstrated high specific capacitance of 194.8 F g-1 at the current density of 2 A g-1.Additionally,the coulombic efficiency remained 95%after 10000 cycles at 10 A g-1 The symmetrical supercapacitor also exhibited high energy density of 9.1 Wh kg-1 with power density of 300O W kg-1.(2)Based on the above work,we prepared sulfur/porous carbon film composite cathode material(S@ISCF)via typical melt-diffusion process.Sulfur was distributed uniformly in the carbon film thanks to the high surface area.And the hierarchical pores achieved good physical sorption of sulfur and polysulfides,which constraining the active materials in the cathode and increasing their utilization.Meanwhile,carbon nanotubes penetrated into the porous carbon polyhedron and formed a three-dimension conductive network,providing easy transportation pathway for electrons and ions as well as suppressing the volume change during the cycling process.As a result,the S@ISCF achieved excellent rate performance and cyclic stability.When sulfur loading was 2 mg cm-2,the capacitance recovered from 650 to 1000 mAh g-1 when the current density reduced from 10 C to C/5,And the capacity retained at 693.2 mAh g-1 after 300 cycles at C/5 under high sulfur loading of 6.4 mg cm-2.The capacity decay rate was as low as 0.02%/cycle when compared with the initial capacity of 761.6 mAh g-1.(3)In order to improve the conductivity of the porous carbon film,ZIF-8/CNT based nitrogen-doped self-standing carbon films(CNCF)were synthesized.The introduction of nitrogen atom improved the electrochemical performance by increasing the electric conductivity as well as the wettability of the carbon film.When used as supercapacitor electrode,the CNCF delivered a high specific capacitance of 340 F g-1 at 2 A g-1,long-term stability with a coulombic efficiency of 97.7%after 10000 cycles at 20 A g-1.When served as sulfur host for the lithium-sulfur battery,the S@CNCF electrode exhibited a high discharge capacity of 614 mAh g-1 after 1800 cycles with an ultra-low overall capacity decay of 0.02%/cycle with sulfur loading of 3 mg cm-2.Moreover,when the sulfur loading was increased to 6.9 mg cm-2,the electrode showed a high initial areal capacity of 7.3 mAh cm-2 with volumetric capacity of 0.94 Ah cm-3. |
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