Molecular Dynamics Simulation Study Of The Energy Storage Mechanism Underlying Supercapacitor With Nanostructured Electrode

With the rapid development of renewable energy in recent years,it requires energy storage devices with high performance,due to the intermittency of renewable energy.As an advanced class of electrical energy storage devices,supercapacitors are very promising due to their good performance.It has been reported that the nano-structured electrode of supercapacitors could make a great impact to their performance.Thus,seeking for high performance materials with controllable nanoporous structure would be of great importance to the application of supercapacitors.By performing molecular dynamics simulation,we have investigated the energy storage mechanism underlying supercapacitors based on different nanopore structure.We hope this study could contribute to finding out highperformance electrode materials with controllable nanoporous structure.In this thesis,we used three types of electrode materials,i.e.,those with cylindrical,slit-shaped and hexagonal surfaces,which are model by carbon nanotube,graphene and conductive metal organic frameworks in molecular dynamics simulations,respectively.Our research to cylindrical pore modeled by opened single walled carbon nanotube revealed a higher differential capacitance of the negative electrode than positive electrode,which can be attributed to the interaction between ions and waters.As for the slit-shaped pore modeled by graphene layers,although a smaller pore size of slit may help increase capacitance,our simulation results suggest that the decrease of net charge of ions inside the pore may weaken this effect,as the association of waters and ions under extreme nanoconfinement.For nanopores with hexagonal surfaces modeled by conductive metal organic frameworks,we analyzed the discrete structure of electrical double layers and the ion exchange mechanism under different voltage,inside the pore.Simulations also suggest that the large pore with a diameter about 2.63 nm might help store more charge.In this thesis,by performing molecular dynamics simulations with different electrode materials,we investigated the electrical double layer of their electrode-electrolyte interface,and the process of ions swapping during the charging process.The performance of each material is evaluated,such as capacitance and differential capacitance.We found out comparable performance between conductive metal organic frameworks and graphene.By virtue of tunable nanopore structure,conductive metal organic frameworks have advantage of other kinds of electrode materials,and can be used in manufacture of supercapacitors with both higher energy and power densities.