Improving the ionic transport properties of graphite anodes for lithium ion batteries by surface modification using nanosecond laser

Ion transport limitation is a well-known problem that occurs when the energy density of a battery is increased by using thicker or higher densified electrodes. To counteract this effect, several studies are currently investigating post-processing methods such as ablative trenching or perforation. This is a promising approach as long as significant loss of active material is accepted. In this study, a pulsed nanosecond laser machining is presented, which aims at a material-preserving surface treatment. Microscopic images show the exposure of additional accesses into the microporous structure of the anodes. At the same time, there is an increase in the outer surface area and roughness. This leads to reduced cell overpotentials and an increased rate capability of the anodes. For example, it is reflected in a higher CC share of up to 50% of the CC-CV charge capacity. Reduced ionic resistance of the laser treated anode layers are measured by impedance spectroscopy. The cyclic stability of the electrodes is not affected. Anodes of 3 mAh/cm2 and layer densities of 1.4 g/cm³ to 1.7 g/cm³ were investigated. Electrochemical tests were performed with half- and full-cells using Li metal and NCM622 counter electrodes as well as symmetrical anode cells.