In-situ Growth Regulation And Energy Storage Characteristics Of Cobalt-nickel-based Self-supporting Electrodes

Supercapacitors and lithium-ion batteries are promising environmental friendly renewable energy storage and conversion devices,but improved demand of their electrochemical storage performance is in great need as they are widely used in portable electronic devices and electric/hybrid vehicles.As it is known to all,electrode materials are the key features in determining the performance of lithium-ion batteries and supercapacitors,so a large number of researchers are committed to develop a new generation of high-performance electrode materials.Cobalt-nickel-based compounds are promising electrode materials due to the features of low prices,rich sources and high theoretical capacity.In addition,three-dimensional self-supporting materials as the electrode materials can efficiently improve the electrochemical performance,as it can shorten the transmission path of electrons and ions.Furthermore,it can increase the effective contact area between the active material and the electrolyte.Based on the above analysis,the research content of this paper is divided into the three parts:1.Ni3S2/NF composites were synthesized by in-situ growth of Ni3S2 nanorods on foam nickel.The three-dimensional self-supporting composites were directly used as electrode materials for supercapacitors.In the 2 M KOH electrolyte,when at the current density of 1A g-1,the specific capacity of the composite can reach 812 F g-1,showing an excellent electrochemical performance.At the same time,the effects of different reaction temperatures on the composites and their electrochemical properties were studied by adjusting the hydrothermal temperature.2.NiCo2S4/carbon cloth(NCS/CC)composites were prepared through "one step"hydrothermal method.When explored as the supercapacitor electrode material,the NCS/CC composites shows high discharge capacity,superior rate performance and stable cycle performance.The specific capacity is up to 1411 F g-1 at 1 A g-1 and even at 20 A g-1,the specific capacity can still reach 1062 F g-1.Moreover,the specific capacity can reach 85.5%of the initial capacity at a current density of 20A g-1 after 2000 cycles.3.The porous NiCo2O4 nanosheets with hierarchical structure were grown on a conductive carbon cloth substrate(NCO-PSA/CC)through a simple hydrothermal and afterward calcination method.Explored as a self-supported lithium ion battery anode,the NCO-PSA/CC showed excellent electrochemical performance(a first discharge capacity of 2090.8 mAh g-1 and a stable capacity of 1687.6 mAh g-1 at 500 mA g-1),superior rate capacity(discharge capacity of 375.5 mAh g-1 at 6000 mA g-1 and excellent reversibility(coulombic efficiency of approximately 100%).The outstanding performance should be ascribed to the good conductivity and the three-dimensional porous structure,which not only ensures the rapid transmission of lithium ions and electrons,but also alleviates the huge volume changes during the lithiation process.