Preparation And Electrochemical Properties Of Mn-Based/Carbon Composites

At present,non-renwable energy such as coal and oil is constantly consumed.In order to solve this energy crisis,it has become an urgent problem to develop new energy and design high-performance energy storage devices.Therefore,the supercapacitor,that includes high power density,fast charge-discharge rate,long cycle life and low cost and so on advantages,has been invented.But there are some defect in supercapacitor like lower specific energy density which result in that limited largely in supercapacitor applying.Mn based material has higher theory specific capacitanace,natural abundance,lower cost advantages.Therefore,in this paper,we combined metal and metal oxide which are mainly used as electrode material in pseudocapacitive with carbon material which are mainly used in double layer supercapacitor to capture electrode material.Through constantly improve the propotion of material and improve experimental conditions to obtain the best,optimal performance electrode material and then increase the specific energy density of supercapacitor.In this work,we successful introduce the metal and Zn-based zeolite imidazolide material?ZIF-8?in sodium manganese ore material Mn dioxide and improve the performance of Mn dioxide electrode material.I use the simple hydrothermal and magnetic stirring and then capture the composite that ZIF-8 coated with silver and Mn dioxide.According to morphology and performance characterization results show that ZIF-8 successful coated with Mn dioxide increasing the electrochemical activity area of Mn and then producing more activity site for ion desorption.And introduce silver successfully had improved the conductive of all electrode material.When the current density is 1 A g^-1,the specific capacitance of Ag-Mn-ZIF-C is 177 F g^-1 higher than 110F g^-1 of Mn-ZIF-C electrode material.However,through the test of cyclic stability,the specific capacitance value only retains 47%of the initial capacitance value after 1000cycles.In this experiment,the morphology of carbon material is changed to carbon sphere that can improve the specific capacity of carbon based material.And then the core-shell structure is made by coating with MnO₂.A material with lager electrochemical activity surface area than the described above is obtained,and the electrochemical performance of this structure composite have been improved.The results showed that the difference of carbon sphere's structure can increase the valid specific surface area of this composite significantly.And the rapid and smooth transmission of ion can attribute to the uniform distribution and without agglomeration structure of this composite,so there are many wide and effective drill way to ion transmission.Therefore,the electrochemical property of MnO₂@HCS with a core-shell structure is better than those Ag-Mn-ZIF-C composite material.According to GCD curves and cyclic stability test can conclude that the specific capacitance of MnO₂@HCS composites is 227.5 F·g^-1(1 A·g^-1),after 1000 cycles its specific capacitance retention rate is 98%.However,after 1000 cycles Ag-Mn-ZIF-C specific capacitance retention rate is only matain 47%.