Fabrication Of High-performance Ni/Co-based Electrodes For The Construction Of Supercapacitors

Renewable energy utilization is one of the most promising solutions to balance troubles between energy and environment.Development of highly efficient,stable and environment-friendly energy storage devices is the key point for the utilization of renewable energy.Supercapacitors(SCs),with their intrinsic merits of fast recharge capability,excellent power density and long cycling durability,have many competitive edges.Nevertheless,the relatively lower energy density of SCs seriously limits their large-scale commercial applications.Therefore,it is important to explore and develop the SCs with high energy density.This work fabricated electrode materials with high capacity efficiently and constructed high-performance SCs.As follows,the main research results are presented:(1)A rapid and solvent-based synthesis method at room temperature was used to prepare low-crystalline Ni/Co-based MOFs.These Ni/Co-based MOFs with different Ni/Co molar ratios show extraordinary electrochemical activities.Particularly,the Ni₂Co-MOF electrode was found to have a capacity up to 2,149 mC cm^-2 at 1 mA cm^-2.Ni₂Co-MOF//AC hybrid supercapacitor(HSC)devices delivered 66.1 Wh kg^-1 at 800W kg^-1.These results suggest the great potential of such rapidly synthesized Ni/Co-based MOF as electrode materials for practical supercapacitors with high-energy and high-power densities;(2)A coral-like Ni₂P@C composite with superior electrochemical performance and strong cycling stability was successfully derived from Ni-MOF,and the Ni-MOF(as precursor and sacrificed template)was prepared by rapid solvent synthesis at room temperature.The obtained Ni₂P@C composite delivers an outstanding specific capacity of 3,631mC cm^-2at 1 mA cm^-2(979 C g^-1 at 1 A g^-1).The HSC,assembled with Ni₂P@C and AC electrodes,exhibits remarkable cycling durability(90.5%capacity retention after 10,000 cycles);(3)The effect of the Ni:Co for the capacitive properties was investigated experimentally in Ni_1-xCo_x-P@C.The results are presented:(a)the electrochemical activity of Ni_1-xCo_x-P@C electrodes were greatly affected by the content of Co:a certain amount of Co(x?0.2)into Ni₂P may markedly enhance their specific capacity and rate capability,but if the Co content surpasses that of Ni(x?0.5),the specific capacity starts to decrease dramatically;(b)the Ni_0.9Co_0.1-P@C electrode with an optimized Ni:Co ratio shows an extraordinary specific capacity of 4,250 mC cm^-2 at the current density of 1 mA cm^-2(1,327 C g^-1 at 1 A g^-1),which is in the advanced level of TMP electrodes reported so far;(c)the Ni_0.9Co_0.1-P@C electrode also delivery an excellent rate capability,it is a preferred electrode for high energy density supercapacitor.In this thesis,the Ni/Co-MOFs and its transition metal phosphides derived materials were fabricated in a novel method and they were used as electrodes in SCs with high energy density,high power density and strong cycle stability,which provides important theoretical significance and practical value for further application of renewable energy.