Laser-Structured Electrodes for Lithium-Ion-Batteries – Dependence of Structure Density on Fast Charging Capability

Abstract

The significant increase in energy density is a declared development goal for lithium-ion batteries for applications in electric vehicles. This implies the use of electrodes with significantly increased areal capacity and mass loading. It is known from a large number of investigations that with increasing electrode thickness both lithium ion diffusion in the electrolyte and electron transport to the current collector dominate, leading to insufficient current carrying capacity electrodes. To achieve an improvement of the fast charging capability of high areal capacity electrodes, they are getting structured, which maximizes the surface area between the electrolyte and the electrode. By means of structuring, electrodes with a high areal capacity can achieve both a high specific discharge capacity and a sufficient fast charging capability. The aim of the perforation is to minimize the resistances and to generate an increased surface area between the electrolyte and the electrode, which leads to new transport paths for the lithium ions. Previous publications show that the laser-structuring of anodes and cathodes lead in particular to an improvement of the charge/discharge rates and cycle stability [Habedank 2018/2019, Kraft 2019, Smyrek 2019].Recent findings indicate there is a relationship between structure density and electrochemical (fast charge/discharge capability) properties. The goal of the presented work is, to determine the dependence of structure density on fast charging capability. For this purpose, anodes and cathodes are symmetrically processed with different spot density, from which full cells are built and analyzed after electrochemical tests. Graphite-silicon anodes with an area capacity of 8,0 mAh/cm² and cathodes with an area capacity of 6,0 mAh/cm² will be processed with spot distances from 180 µm to 510 µm.