Laser structuring for improved battery performance

Within the last two decades, lithium-ion batteries (LIBs) have emerged as the power source of choice in the high-performance rechargeable battery market.1, 2 LIBs are high-capacity batteries that are able to store electricity converted from green energy sources (e.g., solar and wind power), and they can act as energy sources in pollution-free electric vehicles. Nevertheless, there are several drawbacks to state-of-the-art LIBs, including high production costs, short battery lifetimes, safety issues, and time-consuming charging periods. The main issue in cell production is the electrolyte wetting of LIBs, which is realized through timeand cost-consuming vacuum and storage processes at elevated temperatures. Insufficient wetting of electrodes results in a production failure rate, accompanied by a reduced cell capacity and cell lifetime. The development of 3D electrode architectures in LIBs is a relatively new approach for overcoming the problems related to battery performance (e.g., power losses or high interelectrode ohmic resistances3) and mechanical degradation4 during battery operation. 3D batteries can be used to achieve large areal energy capacities, while simultaneously maintaining high power densities. A common approach is 3D structuring of the electrode substrate (the ‘current collector’) before deposition of the thin-film electrode. Unfortunately, this method is in a very early stage of development for model electrodes in thin-film microbatteries. Furthermore, it is generally not feasible for up-scaling to thick-film composite electrodes or for large electrode footprint areas. At the Karlsruhe Institute of Technology, we have thus developed a new technical approach for the generation of 3D electrode designs that can be applied to all types of LIBs (i.e., thin-film batteries, as well as high-energy and high-power LIBs).5 In this approach, for the first time, we have applied laser-assisted processing to the active electrode material itself. For this Figure 1. Scanning electron microscope images of laser-generated microstructures in composite electrode materials. (a) Self-organized microstructures (produced with the use of an excimer laser) and (b) micro-pillars obtained from direct laser structuring with an ultrafast (femtosecond) laser.