Electrode Design for Improving Fast Charging Performance without Loss of Energy Density in Lithium Ion Batteries

Abstract

The technical developments of lithium-ion batteries for electric vehicles have been focused on higher energy densities for increased mileage. On the other hand, as the supply of electric vehicles increases, the demand for fast charging is also increasing. Conceptually, lithium ion and electron conduction resistance should be kept as small as possible in order for smooth fast charging without undesirable side reactions. To solve these problems, researches mainly on materials having the larger specific surface area and better electronic conductivity have been conducted, but commercialization of these kinds of researches has not been achieved due to high manufacturing cost, loss of energy density and electrochemical instabilities. For this reason, herein, we have investigated the design of electrodes for fast charging that minimizes material changes without loss of energy density. In an electrode having a high current density, the lithium ion and the electron conduction mentioned above need to be optimized for improvement of fast charging performance, but the conduction directions are opposite to each other. In order to reduce the conduction resistance of lithium ions, it is necessary to supply a sufficient electrolyte around the active materials, so it is necessary to secure open pores in the electrode for the smooth movement of the electrolyte. Whereas, in order to reduce the electronic conduction resistance, it is needed to have a compact electrode structure to achieve close physical contact between materials. In this study, we investigated the effect of various design parameters such as current density, electrode density and types of conducting agent on the fast charging performances. During the CC-CV charging process, the ratio to the reaction capacity in the CC region was measured while varying the C-rate for various design factors. In addition, electrical conductivity and porosity were analyzed to identify the root causes of the electrochemical performance and cyclic voltammetry was performed using the Randles-Sevcik equation for the analysis of lithium ion migration characteristics. Details of the research will be presented through the presentation materials.