Synthesis And Supercapacitive Performance Of Copper-based Composites

Rational architecture design and electrochemical performance optimization of the electrode materials are highly desirable in developing high-performance supercapacitor devices.Copper-based substrates present high electrical conductivity with abundant natural resources,while their theoretical capacities are relatively low,so they are usually used as current collectors of thin-film electrodes.However,the slurry of a typical thin-film electrode consists of active materials and binders,the insulating binders may result in microstructural destruction of active materials and increased resistance of the whole electrode,further decreasing the energy storage efficiency.In this thesis,we developed different strategies for the synthesis of binder-free copper-based composites.The energy storage performance of electrodes was significantly improved by multi-dimensional structural design and electrochemical performance optimization of the copper-based materials.The main contents are as follows:First,one-dimensional Cu O nanorod arrays were in-situ synthesized on porous copper foam(CF),then a facile cathodic electrodeposition method was adopted to realize uniform deposition of Zn Co-OH nanosheets on the surface of Cu O nanorods,leading to the successful construction of the three-dimensional Cu O@Zn Co-OH core-shell structural electrode.Benefiting from the fine tuning of Zn/Co ratio in the deposited hydroxide,which effectively enhanced the synergistic effect between different components,the pseudocapacitive performance of Cu O@Zn Co-OH composites was greatly improved.The as-prepared Cu O@Zn₁Co₂-OH electrode exhibited a high areal capacitance of 2.634 F?cm^-2(5 m A?cm^-2),with 71.6%capacitance retention under 30 m A?cm^-2.Meanwhile,loofah sponge derived carbon(LSDC)was fabricated by a high-temperature calcination process with the combination of KOH activation as the negative electrode material.The as-assembled Cu O@Zn₁Co₂-OH//LSDC aqueous asymmetric supercapacitor delivered an energy density of0.21 m Wh?cm^-2(4.08 m W?cm^-2)with a long cycle life(91.7%capacitance retention after 4000cycles under 30 m A?cm^-2).Second,copper-foam supported Cu-doped Ni Co-OH heterostructure was constructed with the super hydrophilic Cu(OH)₂ as the precursor.The long-term electrochemical cycling process triggered the in-situ transformation from Cu/Ni Co-OH to the electrochemically activated Cu O-doped Ni Co-OH(EA-Cu O/Ni Co-OH),accompanying morphological degradation and structural evolution.The electrochemical activation process could induce the dissolution of F anions as well as the irreversible oxidation of Co cations,which not only led to the formation of abundant structural defects but also provided more electroactive sites.The battery-type EA-Cu O/Ni Co-OH electrode achieved a high areal capacity of 4.186 C?cm^-2under 5 m A?cm^-2,with an excellent rate performance(67.5%of initial capacity under 50m A?cm^-2).Moreover,the EA-Cu O/Ni Co-OH//AC aqueous hybrid supercapacitor was assembled using commercial activated carbon(AC)as the negative electrode,which delivered a high energy density of 0.65 m Wh?cm^-2(8.87 m W?cm^-2).The EA-Cu O/Ni Co-OH//AC presented excellent cycle stability with 93.4%capacity retention after 8000 charge-discharge cycles.