Molecular Dynamic Study Of Supercapacitors Prepared By 2D Nano Materials

In the past decades,molecular dynamics simulations have become an important tool in the fields of materials science,physics,chemistry and biology.Simulation technology has been widely used in the field of electrochemical simulation,but the existing simulation method to achieve accurate calculation requires a lot of computing power and cannot calculate the CV curve in the process of electrode discharge,in this paper we introduce a LAMMPS application in electrochemical,we designed a new theoretical calculation method for simulating the surface of supercapacitor electrode ions,the main research content is as follows:1.In the introduction,we introduce the Constant Charge Method and the Constant Potential Method,and summarize the differences and advantages and disadvantages of the two methods.On this basis,we propose a new theoretical calculation method that combines the advantages of both methods.By using this calculation method and taking the MXene supercapacitor as an example,we obtain the CV curve of the supercapacitor electrode during charging and discharging,and give the new motion law of electrolyte ions around the electrode by using a more fitting model to the experiment.2.In the following chapters,we delve into the effect of electrode current intensity on the simulation results in LAMMPS molecular dynamics simulation.We found that the electrode surface charge/discharge rate is not high at a charging interval of 0.1 ns,that is,under high current intensity,the movement of charged particles in the electrolyte cannot keep up with the changes in the charge on the electrode,which is consistent with the phenomenon observed in the experimental supercapacitor.At a charging interval of 0.2 ns and 0.3 ns,that is,under lower electrode current intensity,the charging completion rate is high,and the movement of electrolyte ions is relatively stable.We also found that the discharge completion rate is much lower than the charging completion rate when using this method,which is an area that needs improvement.3.In the final chapter,we combine theory and experiment.We combine this molecular dynamics theory technology with experiments and prepare a supercapacitor composed of copper sulfide and nickel sulfide composites,in which nickel sulfide serves as a collector and copper sulfide serves as an active material.We model and study the effect of nickel sulfide pore channels on electrolyte ion movement during charging and discharging.We found that the copper sulfide tunnel grown on the Ni3S2 substrate will limit the movement of K+ions and increase the surface OH.ion density on the positive electrode surface.According to the reversible redox reaction occurring on the surface,we can further deduce that this mechanism can improve the capacitance of the Ni₃S₂@Cu S supercapacitor.