Controllable Synthesis Of Graphene-Based 2D Mesoporous Materials For Micro-Supercapacitors

With the rapid development of 5G and Internet of Things technology,it is urgent to exploit micro-energy storage devices matching with portable intelligent electronic products.Due to high power density,long cycle life and excellent safety,micro-supercapacitors（MSCs）are regarded as one of the most promising micro-energy storage devices.However,the low energy density of MSCs severely limits their practical application.Therefore,developing high-performance electrode materials is considered as the key to enhance their energy density.In recent years,graphene-based2 D mesoporous materials with large specific surface area,rich active sites,fast ion transport and excellent energy storage capacity,have been developed as highperformance active electrode materials for MSCs.But the controllable preparation of graphene based 2D mesoporous materials remains a huge challenge owing to the uncontrollability of intermolecular forces between precursor and graphene.In addition,studying the structure-activity relationship is instructive for the structural design,electrochemical performance and practical application of graphene based 2D mesoporous materials.Based on these issues,we have developed an interfacial induced self-assembly method to prepare graphene-based 2D mesoporous materials with tunable structure and excellent electrochemical performance for MSCs.The main research contents and results are as follows:1.2D mesoporous polydopamine/graphene（m PG）are synthesized for MSCs with high energy density.The m PG nanosheets possess mesoporous structure with different exposure degrees and adjustable thickness（7.5-14.1 nm）.By comparing the electrochemical properties of m PG with different thickness,the structure-activity relationship between them has been revealed.Due to the moderate thickness,exposed mesopore,and large surface area of 108 m2 g^-1,the m PG with 10.8 nm thickness（m PG-2）exhibits 419 F g^-1 at 0.5 A g^-1 and retains 96% of initial capacitance after 5000 cycles.With m PG-2 as active electrode material and PVA/H2SO4 as gel electrolyte,the constructed MSCs show excellent volumetric specific capacitance(34.3 F cm^-3)and volumetric energy density(3.1 m Wh cm^-3).In addition,the symmetric m PG-based MSCs assembled with "water in salt" gel electrolytes display high output voltage（1.6V）and volumetric energy density(11.5 m Wh cm^-3).These MSCs also exhibit outstanding flexibility and self-integration performance.Therefore,this study provides a new design idea for graphene based 2D mesoporous materials and their highperformance MSCs applications.2.2D mesoporous nitrogen-doped carbon/graphene（m NC/G）nanosheets are prepared for high-performance MSCs.This interfacial induced self-assembly preparation strategy uses aniline as the carbon and nitrogen source,graphene oxide as the 2D structure guiding agent,and silica as the mesoporous template.By changing the size of mesoporous template,the pore diameter of m NC/G can be precisely controlled（7 nm,12 nm and 22 nm）,and the structure-activity relationship between them is explored in detail.Notably,the m NC/G nanosheets with 7 nm mesopore（m NC/G-7）exhibit the largest specific surface area(433 m2 g^-1),excellent conductivity and highest specific capacitance(267 F g^-1 at 0.5 A g^-1).Furthermore,the MSCs based on m NC/G-7 reveal high volumetric specific capacitance of 21.0 F cm^-3 and energy density of 1.9m Wh cm^-3,as well as excellent self-integration performance.This work proves that graphene-based 2D mesoporous materials can significantly improve the electrochemical performance of MSCs.