Toward efficient electrodes for a high-performance fast-charge Li-ion battery: molecular dynamics simulation and DFT calculations

Abstract

Due to the increasing demand for electrochemical energy storage, rechargeable lithium-ion batteries (LIBs) are gaining more and more attention. However, much research still needs to be conducted to enhance their cycling and storage capacity. Recently, computational studies have provided valuable information for LIB development, which is very difficult and expensive to obtain experimentally. In this study, molecular dynamics (MD) simulation and first-principles calculations are performed to investigate the potential of a Cu-BHT MOF and phosphorene as the cathode and anode, respectively. An external electrical field is applied to simulate the charging process and study lithium-ion behavior during migration from the cathode to the anode in an electrolyte. Time and space-dependent variables such as energy, radial distribution function, mean square displacement (MSD), density, and so on have been used to evaluate the studied system. The MSD calculations showed that there are two different regimes in the MSD curves of Li-ions; diffusion and cage. In the designed LIB, the cathode has a better performance in the presence of a high electric field, whereas under an external electric field of 1.5 V Å⁻¹, more lithium ions move from the cathode to the anode. By using first-principles calculations the lithium insertion in phosphorene and Cu-BHT is studied in various configurations and concentrations. The obtained results indicated that the adsorption energy of lithium on the cathode in the most stable configuration is −3.21 eV which is enough to prevent the clustering effect. Furthermore, the interaction of Li with phosphorene is strong enough and forms a stable complex. It is found that by insertion of Li into the anode the band gap is decreased which indicates the possibility of fast charging of LIBs. Investigation of different concentrations of ions reveals that the Li–Li repulsive interactions lead to a decrease in the adsorption energy of Li with the anode and cathode. The results of this study provide an in-depth insight into LIBs.