| In contemporary society,the consumption of non-renewable energy and environmental pollution have always been the focus of human thinking.Researchers hope that more sustainable energy will be developed to replace traditional energy sources,which has led to a growing demand for environmentally friendly,low-cost,high-capacity and long-life energy storage devices.In recent years,lithium-ion batteries as the most popular secondary battery are being used in various fields such as cars,watches and computers.However,the scarcity of Li metal,the pollution of organic electrolytes,and the harsh battery assembly environment still restrict its development.Therefore,the aqueous multi-valent ion batteries based on Zn2+,Mg2+ and Al3+ have been paid more and more attention.Among them,the aqueous zinc ion battery is considered to be one of the most promising energy storage devices due to its high theoretical volume capacity(5851 mAh cm-3)and low redox potential(-0.76 V vs.SHE).At present,the commercialization progress of aqueous zinc ion batteries is mainly limited by the damage of anode zinc dendrite to the battery structure,the poor electrical conductivity of cathode materials,the lack of appropriate ion channels,and the easy collapse of the structure.In this study,two steps consisting of hydrothermal and calcination were used to prepare MnO/reduced graphene(rGO)/multi-walled carbon nanotubes(MPGC)with three-dimensional porous structure as cathode materials for aqueous zinc ion batteries.In addition,a simple one-step hydrothermal method was used to prepared Na2V6O16·nH2O with distribution uniform belt structure.The specific research contents are as follows:(1)MPGCs were prepared by adding KMnO4 to a mixture of graphene oxide(GO)and multi-walled carbon nanotubes(MWCNTs),and then undergoing hydrothermal and calcining treatments.The MPGC has a surface area of 116.8 m2 g-1 and a mesoporous pore structure.As a cathode material,its rich mesoporous structure can provide more pathways for Zn2+transfer and more active sites for electron transfer at the interface.In terms of electrochemical performance,it can achieve a high capacity of 293.5 mAh g-1 at a current density of 0.2 A g-1 and maintain a specific capacity of 103.1 mAh g-1 after 550 cycles at a current density of 1.2 A g-1.(2)Commercial V2O5 powders were added to the NaOH solution and Na2V6O16·nH2O with a ribbon structure was prepared by a simple hydrothermal method.The Na+ in Na2V6O16·nH2O can act as a pillar between the vanadium oxide layers,which provides a wider channel for ion transport so as to accelerate the transfer rate of Zn2+.At the same time,the introduction of Na+ can increase the conductivity of vanadium oxide,which is beneficial to improve the reaction kinetics of the material.In terms of electrochemical performance,it can achieve a high capacity of 355.1 mAh g-1 at a current density of 0.1 A g-1 and still achieve a specific capacity of 120.7 mAh g-1 after 600 cycles at a current density of 4 A g-1. |
