Preparation Of Three-dimensional Transition Metal Oxide/sulfide Composite Aerogels And Their Application In Supercapacitor

With the rapid development of modern technology and new energy system,as well as the excessive consumption of non-renewable energy and the growth of energy demand,efficient renewable energy storage system has attracted wide attention.Supercapacitors（SC）have attracted much attention for its excellent charge-discharge performance,long cycle life,high power density and green sustainability.As a key component of SC,electrode materials determine the electrochemical performance of SC.Transition metal compound（TMC）materials with excellent energy density,high specific capacitance,and fast charge/discharge rate are among the most promising SC electrodes.TMC materials also have the advantages of being easy to prepare,low cost,and abundant raw materials.However,the poor active surface area limits the electrochemical performance,which can be improved by three-dimensional（3D）porous nanomaterials due to their rich specific surface area and fast electron transport rate.Therefore,this paper takes transition metal compound composite porous aerogel prepared 3D structure electrode material as the research object,and assembled the supercapacitor device with excellent energy storage performance,the specific research work is as follows:（1）We designed a large-scale and cost-effective cobalt sulfide nanoparticle/carbon aerogel(Co S_1.97/CA)supercapacitor electrode.The CO²⁺was absorbed and the quantum-sized Co S_1.97 nanoparticles were synthesized by in-situ vulcanization on the surface of CA using watermelon biological tissue with low cost and easy access to raw materials as the template of biomass carbon aerogel.The quantum size of Co S_1.97 nanoparticles can not only act as a collector to accelerate the electron transfer rate,but also provide abundant active sites for the redox reaction of electrolyte ions.Based on its unique 3D porous structure and outstanding electrochemical activity,the Co S_1.97/CA electrode has a high specific capacitance of 1715 C g^-1 at 1 A g^-1 current density.Furthermore,an asymmetric supercapacitor is assembled by employing Co S_1.97/CA-500 as positive electrode and CA as negative electrode,which delivers the highest capacity of 51.5 m Ah g^-1 and energy density of 36.4 Wh kg^-1.In addition,an impressive cycling span of 20000 cycles is obtained with capacity retention reaching up to 98.9%,demonstrating its high stability for real-world application.These findings demonstrate the bio-inspired and cost-effective development of3D carbon aerogel electrode for incorporating with other novel materials for the applications in energy storage.（2）NiCo₂O₄（NCO）microtubules assembled with ultra-thin mesoporous nanosheets were prepared by hydrothermal reaction and deposited on compressible Ti₃C₂T_x MXene/reduced graphene oxide（rGO）aerogel（MGA）with high conductivity and large specific surface area.The optimized NCO/MGA-300 sample shows a reversible compressive strain of 60%and a superior durability.Density functional theory（DFT）calculations reveal that the NCO/MGA-300 heterojunction has high electronic conductivity,fast electron transfer ability,and low adsorption energy for OH^–ions.The electrochemical performance test results show that the NCO/MGA-300 electrode has excellent specific capacitance(1633 F g^-1 at 1 A g^-1)and rate performance(1492 F g^-1 at 10 A g^-1),as well as the initial capacity retention rate can reach 86.6%after 10000 cycles of charge and discharge.Moreover,an assembled asymmetric supercapacitor based on compressible NCO/MGA-300 shows stable electrochemical performances under different compressive strains（20%,40%and 60%）,or after 100 compression-release cycles.This research finding demonstrates the possibility of metal-based electrode for wearable devices with high energy storage capability and good compressibility.