Application Of The Composite Structure Of Nickel Nanocylinder Arrays And MnO₂ Nanosheets In Energy Storage

With the rapid development and wide application of small and micro electronic devices,the corresponding energy storage equipment becomes a research hotspot for researchers.In order to meet the increasing energy demand of the social development,the development of energy storage devices with high specific capacity and high power density become the focus of research.As one of the most widely used energy storage devices,supercapacitors have attracted much attention.In practical application,the supercapacitor shows different practical performance with lithium ion battery as their energy storage mechanisms are different,the supercapacitor can quickly perform a charging and discharging process with high power density,while the battery has a larger capacity,so it is often used in conjunction with the latter to achieve different application purposes.Carbon material is one of the widely used materials in supercapacitors.Due to its low theoretical capacity,however,it is difficult to reach the goal of achieving higher capacity for capacitors.The theoretical capacity of transition metal oxides is relatively high because of the reversible redox reaction with ions in electrolyte when they are used as electrode materials.However,only the surface part contacted with the electrolyte can take part in the reaction for bulk active substances,and the other parts are limited by the depth of ion insertion and become dead volume,which reduces the utilization rate of the active substances.To solve this problem,researchers reduced dead volume and increased utilization by nanocrystallizing active substances.In addition,the combination of the active substances with the electrode by coating insulating binders will cause the dead volume and decrease the electrode performance by increasing the contact resistance between the active substances and the electrode.In order to solve these problems,we synthesized the transition metal oxide combined with the nanostructured metal collector by in-situ growth,which effectively avoids the increase of contact resistance caused by the use of insulator binder.In addition,the proper crystal form can improve the transport of ions in the active substances.These methods can guarantee the utilization of active materials and obtain active materials with high capacity,energy density and power density.The paper consists of the following two parts:1.Explore the effects of nanostructures on current collectorsAs the study of active substances has deepened,the methods of collectors have become more complex,which are designed to increase the specific surface area of the current collectors.This paper discusses the simple electro-etching way of treating the foamed nickel as current collector and synthesizing the Ni nanocylinder arrays on the surface of the current collector to increase its surface area.2.Effect of MnO₂ crystal structure on the performance of supercapacitorsThe layered structure ofδ-MnO₂ was grown on the Ni nanocylinder arrays current collector by electrodeposition.In the hybrid electrode,the layered structure of MnO₂facilitates the diffusion of ions in the electrolyte while reducing the charge transfer resistance.At the same time,δ-MnO₂ can also form a semicoherent interface with the Ni current collector,which reduces the contact resistance between the active material and the current collector.The capacitance of the Ni/MnO₂ NCAs hybrid electrode can reach 883 Fg^-1.