The demand for optimized and affordable lithium-ion battery systems increases with the growing number of electrified vehicles. To this aim, 3D electrode architectures and new high energy density materials like silicon are in the focus of research. To implement silicon in the LIFT-process for fast prototype development, a silicon-rich paste was developed and optimized for the printing. The electrodes containing the silicon-rich paste showed a rather high specific capacity of 3029 mAh⋅g -1. To achieve an enhanced cyclability, a new electrode architecture was developed by using subtractive and additive laser processing in a process chain. For this purpose, a state-of-the-art coated graphite electrode was structured, and the cavities were subsequently partially filled with the silicon-rich paste. After reaching end-of-life, the coin cells were disassembled and analyzed using SEM and LIBS measurements regarding the failure mechanisms.
The expansion of renewable energies is increasing the demand for affordable and enhanced energy storage systems. Here, 3D lithium-ion battery concepts represent a promising approach to improve e.g., energy and power density as well as lifetime of batteries. This work explores the potential of the laser induced forward transfer (LIFT) method as a tool for the realization of new types of 3D electrode architectures on structural and compositional level. Using a pulsed nanosecond UV laser, several parameters were examined to determine the variables affecting reliable material and voxel transfer, including laser fluence as a function of donor layer thickness and donor paste-to-substrate distances, as well as the influence of viscosity and solid content of the anode paste. In addition, a 3D anode is produced by combining laser structuring with subsequent localized laser printing with silicon-rich anode paste.
Possible laser processes in battery manufacturing are quite diverse regarding the control of electrochemical characteristics: LIPSS on current collector surfaces are used to adjust the adhesion of composite electrodes to current collectors, laser surface patterning turns ceramic-coated separator materials into superwicking with regard to electrolyte wetting properties, and laser structuring of composite thick film electrodes is applied to generate 3D electrode architectures with shortened lithium-ion diffusion pathways. In the field of cathode thick film development, secondary particles with nanoscaled primary particles are used and ultrafast laser ablation is applied to pattern the composite electrodes to optimize the lithiumion diffusion kinetics by enlarging the active material surface with a view to reducing cell polarization, which develops at high battery power. This enables high energy batteries to be upgraded for operation at high power. In the field of anode development for electromotive vehicles, efforts are being made to develop silicon anodes in order to significantly increase the energy density. In addition, the issue of fast charging, mainly influenced by the anode architecture, is a major topic in research and industrial development. Silicon nanoparticles are used and combined with graphite particles in a binder matrix. The large volume change as a result of the lithiation of silicon during battery operation requires laser structuring of the composite electrodes in order to counteract mechanical degradation. Analogous to cathode materials, the lithium diffusion kinetics for anodes are also significantly enhanced by the applied 3D battery concept. The impact of laser structuring and modification of battery materials on the electrochemical performance with respect to the nanoscale is of considerable relevance for future applications in battery manufacturing.
Further efforts are needed to increase the power and energy density of lithium-ion batteries. This increase can be achieved by developing new electrode architectures and new active materials. As a new active material for anodes, silicon is in the focus of current research, as it has an order of magnitude higher specific energy density compared to the commonly used graphite. In terms of new architecture, printing anodes with the "laser induced forward transfer" (LIFT) process offers a variety of possibilities. For this work, printing with LIFT adapted anode paste was realized and corresponding laser parameters were optimized. The anodes were printed with graphite for subsequent analyses in a coin cell and compared with state-of-the-art coated electrodes made with the same paste. The conventional coated electrodes were either calendered or uncalendered. It was shown that the electrochemical behavior of the printed anodes is comparable to that of the conventional coated anodes. Finally, preliminary studies were made to print an anode with a multilayer architecture. Within the anode layer, which consists of three individual printed layers, silicon layers are incorporated in order to significantly increase the specific capacity.
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