Study On Energy Storage Devices Based On Cobalt-nickel Double Hydroxides And Biomass Carbon

In recent years,with the rapid progress of science and technology,people's demand for flexible energy storage devices is growing,and electrode material is a key factor affecting the performance of various energy storage devices.Among them,carbon materials and cobalt-nickel based metal hydroxides materials have advantages of abundant resources,low cost,and good electrical conductivity,and thereby have been extensively studied.However,the low energy density of carbon materials,the poor ratio performance and cycling stability of cobalt-nickel hydride are the key performance parameters that hinder their wide application.In this study,the cathode electrode material of cobalt-nickel double hydroxides(CoNi-DH)with excellent rate performance and cycle stability was prepared by in-situ hydrolysis method,and the carbon anode material with high specific capacity was prepared by two-step activation method.The detailed research contents of the thesis are as follows(1)A novel wisteria flower-like microstructure of cobalt-nickel double hydroxide(CoNi-DH)is successfully constructed on carbon cloth(CC)using an in-situ hydrolysis-induced exchange process between hydroxide ions and organic ligands of the Co-MOF in four different kinds of solutions containing Ni2".The effects of different anion solutions on the morphology,interlayer spacing and electrochemical properties of CoNi-DH electrode were investigated.As a result,the optimal CoNi-DH-S@CC(CoNi-DH prepared in Ni2SO4)serves as an advanced electrode to show high-rate capability(only 13%Cs decay after a 15-fold current elevation)and a superior specific capacity(Cs)of 929.4 C g-1,which remarkably exceeds those of the other three CoNi-DHs,and other similar metal hydroxides.Moreover,with this CoNi-DH-S electrode as the positive electrode,the as-prepared asymmetric supercapacitor(ASC)delivers an impressive capacity of 204.8 C g-1,a superior energy density of 42.5 Wh kg-1,and satisfactory cycle life(81.5%reservation after 7,500 cycles).As a proof-of-concept application,a quasi-solid-state ASC is further successfully fabricated based on the CoNi-DH-S electrode to exhibit encouraging application potential.(2)With the carbon cloth as a flexible substrate,the 3D hierarchical aluminum-doped cobalt-nickel double hydroxide(Al-CoNi-DH)micro-nano sheet array was prepared by in-situ growth of Co-MOF and subsequent hydrolysis-induced exchange in the mixed solution of NiSO4 and Al2(SO4)3,using carbon cloth as flexible substrate.The effects of the Al amount on the specific capacity and cycle stability of CoNi-DH electrode materials were investigated.When the feeding molar ratio of Al2(SO4)3 to NiSO4 was 5%,the as-prepared 5%Al-CoNi-DH@CC electrode can obtain the best capacity after 5000 cycles(cycle retention rate was 73%),and had a high specific capacity of 233.5 mAh g-1 at the current density of 1 mA cm-2.When the 5%Al-CoNi-DH electrode was applied as the cathode of the Ni-Zn battery,the highest specific capacities of assembled aqueous and quasi-solid-state Ni-Zn batteries were 264.0 mAh g-1 and 149.1 mAh g-1,respectively.These results confirm a great application potential of this electrode in stable Ni-Zn batteries.(3)The activated carbon felt doped with S and N elements(S,N-ACF)was prepared by two-step activation method using carbon felt and soybean protein isolate powder as the raw materials.And it was used as negative electrode material in the supercapacitor.The effects of alkaline activation and heteroatom doping on the morphology and electrochemical properties of carbon felt(CF)were studied.The prepared S,N-ACF material as an electrode showed a high specific capacitance of 333.0 F g-1 at 1 mA cm-2,good rate performance(after a 10-fold current increase,the capacitance can remain at 71%of the initial capacitance),and excellent cycling stability(99.0%reservation after 13100 cycles).With this S,N-ACF as the negative electrode,the as-assembled CoNi-DH-S@CC//S,N-ACF and 5%Al-CoNi-DH@CC//S,N-ACF ASCs exhibited high specific capacities of 215.0 and 201.8 C g-1,and superior energy densities of 44.5 and 41.8 Wh kg-1,respectively.In addition,the satisfying electrochemical performance of the assembled quasi-solid-state ASCs demonstrated the potential application of S,N-ACF electrode in high-performance supercapacitors.