Multiple Electrochemical Interfaces in Lithium-Ion Batteries: A Fluid Density Functional Theory Study

Lithium-ion batteries encompass multiple electrochemical interfaces. At the electrode–electrolyte interface, the structure of the electric double layer (EDL), especially the ion distribution, directly influences the characteristics and efficiency of the electrochemical process. A fast and accurate description of ion distribution is essential for advancing EDL research and improving the performance of quasi-solid-state polymer electrolytes (QPEs). However, experimental methods currently struggle to directly measure the density distribution of the EDL, and traditional molecular simulations are known for their long computational times. In this article, we have developed fluid density functional theory (FDFT), tailored specifically for the QPE system. The use of polymers increases the ionic density at the interface due to the occupying effect. The thickness of EDL is affected by different polymers’ polymerization degrees. Furthermore, the addition of additives increases the concentration of Li⁺ on the surface of the lithium metal anode. With the application of FDFT and the theoretical direction of the design of QPEs, this paper further develops the design method and puts forward some theoretical suggestions.