Application Of Transition Metal Compound/porous Carbon Composites In Supercapacitor

Transition metal compound electrode materials have become one of the research hotspots in the field of supercapacitors,but most of them have problems such as complex preparation methods,easy structure collapse and poor electrical conductivity,so it is urgent to use suitable material-loaded transition metal compound electrode materials.Among the current mainstream electrode materials,porous carbon-based materials have the advantages of good conductivity,large specific surface area and excellent chemical stability.However,due to the poor energy storage performance of pure porous carbon materials,they are usually combined with transition metal materials or non-metallic elements to obtain transition metal compounds/porous carbon composites with synergistically enhanced energy storage performance.Therefore,this paper mainly explores the preparation of transition metal compounds/porous carbon composites and their application in energy storage of supercapacitors,specifically as follows:Firstly,nickel-cobalt layered double hydroxide（Ni Co-LDH）nanosheets were grownon the highly graphitized nitrogen-self-doped porous carbon aerogel（HPCA）substrate using biomass chitosan as raw material by hydrothermal reaction,and applied to the positive material of supercapacitor.The porous carbon skeleton with high conductivity and large specific surface area brings a large number of active sites and channels for the rapid transport of electrons and ions,and can control the growth morphology of Ni Co-LDH nanosheets.The results show that compared with other electrode materials,the optimized Ni Co-LDH/HPCA composite has excellent electrochemical performance,which is expected to give full play to the application advantages of high-performance energy storage devices.Secondly,electrode materials based on metal-organic frame materials（MOF）are becoming the research hotspot of positive electrode materials for supercapacitors.Nano-cobalt mental modified nitrogen self-doping porous carbonated aerogel（CCA-Co）was prepared by sol-gel method,freeze-drying method and carbonization method using biomass chitosan powder and cobalt salt as raw materials.Layered composite（CCA-Co@MOF）have been prepared by solvothermal reaction growth of Co-doped Ni-MOF（Co-Ni MOF）microflowers.The presence of cobalt nanoparticles in carbonized chitosan aerogel（CCA）not only promotes the self-assembly of CCA and MOF,but also etched cobalt ions can participate in the growth of MOF,resulting in excellent electrochemical performance.In addition,the asymmetric supercapacitor（CCA-Co@MOF//AC ASC）assembled using CCA-Co@MOF and activated carbon（AC）electrodes has a very high energy density(45.9 Wh kg^-1 at 431.7 W kg^-1).This work highlights the advantages of metal nanoparticles modification and carbonized chitosan aerogel for MOF growth,demonstrating its great value in the field of electrochemical energy storage.Finally,the interconnected nano-porous carbon/nickel?cobalt layered double hydroxide（INPC/Ni Co-LDH）composites were successfully fabricated through calcination and solvothermal techniques,by first depositing 2-methylimidazole cobalt salt（ZIF-67）nanoparticles on the surface of INPC using glucose as the carbon source,followed by an in situ growth of Ni Co-LDH nanosheets by controlling ion etching and co-deposition.The obtained INPC/Ni Co-LDH composite exhibited high mass capacitance(1712 F g^-1 at 0.5 A g^-1),good rate capability and cycling performance（86.1%after 5000 cycles）.The assembled INPC/Ni Co-LDH//INPC asymmetric supercapacitor（ASC）showed excellent capacitive performance(115.9 F g^-1 at 0.5 A g^-1)and high energy density(41.2 Wh kg^-1 at 400 W kg^-1).The three prefabricated all-solid-state INPC/Ni Co-LDH//INPC ASCs linked in series could successfully light up a small light bulb,showing a potential application in real life.