Electrochemical Properties of Laser-Printed Multilayer Anodes for Lithium-Ion Batteries.

New electrode architectures promise huge potential for improving batteries' electrochemical properties, such as power density, energy density, and lifetime. In this work, the use of laser-induced forward transfer (LIFT) was employed and evaluated as a tool for the development of advanced electrode architectures. For this purpose, it was first confirmed that the printing process has no effect on the transferred battery material by comparing the electrochemical performance of the printed anodes with state-of-the-art coated ones. For this, polyvinylidene fluoride (PVDF) was used as a binder and n-methyl-2-pyrrolidone (NMP) as a solvent, which is reported to be printable. Subsequently, multilayer electrodes with flake-like and spherical graphite particles were printed to test if a combination of their electrochemical related properties can be realized with measured specific capacities ranging from 321 mAh·g-1 to 351 mAh·g-1. Further, a multilayer anode design with a silicon-rich intermediate layer was printed and electrochemically characterized. The initial specific capacity was found to be 745 mAh·g-1. The presented results show that the LIFT technology offers the possibility to generate alternative electrode designs, promoting research in the optimization of 3D battery systems.

Transition delay using biomimetic fish scale arrays.

Aquatic animals have developed effective strategies to reduce their body drag over a long period of time. In this work, the influence of the scales of fish on the laminar-to-turbulent transition in the boundary layer is investigated. Arrays of biomimetic fish scales in typical overlapping arrangements are placed on a flat plate in a low-turbulence laminar water channel. Transition to turbulence is triggered by controlled excitation of a Tollmien-Schlichting (TS) wave. It was found that the TS wave can be attenuated with scales on the plate which generate streamwise streaks. As a consequence, the transition location was substantially delayed in the downstream direction by 55% with respect to the uncontrolled reference case. This corresponds to a theoretical drag reduction of about 27%. We thus hypothesize that fish scales can stabilize the laminar boundary layer and prevent it from early transition, reducing friction drag. This technique can possibly be used for bio-inspired surfaces as a laminar flow control means.