Study On The Preparation Of Honeycomb Carbon-based Electrode Material By Blowing Method And Their Capacitive Performance

As a new type of energy storage device,supercapacitors are widely used in various fields such as power electronics,energy storage power supplies,transportation,civil and military applications due to their high safety,long cycle life,and rapid charging and discharging,which play an important role in promoting energy structure transformation and rapid economic development.As far as electrode materials for supercapacitors are concerned,two-dimensional graphene occupies a dominant position,but the comprehensive consideration of factors such as preparation cost,synthesis process,product yield,purity and quality restrict its further popularization and application.The appearance of two-dimensional graphemic materials obtained by heat treatment of carbon-containing precursors has alleviated this problem faced by graphene to a certain extent,but graphemic materials still have the phenomenon that the common lamellar stacking of two-dimensional materials causes the specific surface area to decrease.Based on this situation,researchers have proposed a solution strategy for the three-dimensionalization of two-dimensional materials.The specific surface area is increased by assembling two-dimensional graphemic materials into a three-dimensional carbon network.However,in practical applications,it has been found that although larger pores in a single three-dimensional carbon network are beneficial to increase the specific surface area,it will also result in a lower density of the material,making it difficult to obtain a higher specific capacity.Although the traditional mechanical compaction method can increase the carbon network density to a certain extent,it also causes disordered accumulation of electrode materials,which leads to a rapid degradation of performance.Therefore,this paper focuses on the problems of the three-dimensional carbon network,introduces new components through the structure regulation method,realizes the simultaneous synthesis of the two-component three-dimensional carbon network while alleviating the problem of low density.In addition,the construction of the multi-component carbon network was completed through the subsequent component regulation strategy,which significantly improved the electrochemical performance of the three-dimensional carbon network,and provided a new direction and way for the development of the three-dimensional carbon network.The core content of this article is divided into the following three parts:（1）Preparation of three-dimensional carbon network substrate.In this paper,we realized the mass production of three-dimensional nitrogen-doped honeycomb carbon nanocages（NHCN）simply via a chemical blowing strategy.Specifically,this strategy is used to rapidly heat the gel precursor formed by the mixture of polyvinylpyrrolidone,nickel nitrate and ethylene glycol,and"blowing"the precursor with the help of nickel nitrate pyrolysis and gas production.Subsequently,through the corresponding physical,chemical,and energy storage properties tests of the products obtained at different temperatures,it was determined that 750℃is the best heat treatment temperature.The product NHCN-750 at this temperature has the largest specific surface area（53 m²/g）and the best electrochemical performance（56.0F/g at 1A/g;24.0F/g at 20A/g）,so this article uses NHCN-750 as the basis for subsequent structure and composition regulation material.（2）The structural regulation of NHCN-750.This article is based on the structural control strategy of chemical vapor deposition（CVD）.During the heat treatment process,a crucible containing a suitable amount of carbon source（ethanol）is introduced upstream during CVD process.With the help of the catalysis of a large number of Ni particles on the surface of NHCN-750,the simultaneous growth of NHCN-750 and carbon nanotubes（CNTs）is realized,and the product NHCN@CNT-750 is finally obtained in a large amount,which completes the structural regulation of the substrate.Compared with NHCN-750,the specific surface area of the structure control product NHCN@CNT-750 reached 214 m²/g,and the specific capacity reached 154.4F/g at 1A/g and 120.0F/g at 20A/g.In the subsequently assembled symmetrical button-type two-electrode test,when the current density is 1A/g and 20A/g,the specific capacity is 50.8F/g and 31.25F/g,respectively.After 3200 long cycles at 2A/g,95.8%of the capacity is still preserved.In the actual application demonstration,two button capacitors connected in series can make a single red LED light bulb work normally for at least 4minutes,further demonstrating the application potential of NHCN@CNT-750.（3）The compositional regulation of NHCN@CNT-750.In order to further improve the electrochemical performance of the structure-regulated products,this paper no longer uses NHCN@CNT-750 directly as the electrode material,but uses it as a conductive substrate to support other high-capacity active materials.The structural regulation scheme used in this experiment is based on the principle of CVD low-temperature solid-phase reaction.NHCN@CNT-750 is heat-treated in the atmosphere of air,sulfur source,and phosphorus source,in order to convert the Ni particles on the surface into corresponding oxides,sulfide and phosphide,thereby obtaining composition regulation products NHCN@CNT@Ni O,NHCN@CNT@Ni S and NHCN@CNT@Ni₂P.From the subsequent physical,chemical,and electrochemical properties test results,it can be seen that the three methods can achieve component control,but the NHCN@CNT@Ni₂P has the best electrochemical performance.The specific capacity at 1A/g is 1382.5F/g,and 770.0F/g at 20A/g.After 1200 long cycles at 2A/g,70.78%of the capacity can be preserved.Finally,by assembling an asymmetric supercapacitor to further test its practical application potential,and put forward the corresponding improvement plan.