Laser sintering of ceramic-based solid-state battery materials

Summary:

Ceramic solid-state batteries can increase both gravimetric energy density and safety compared to conventional lithium-ion batteries. In a solid-state battery, separator and electrolyte materials are combined in a solid-state electrolyte layer. Materials of high ion conductivity are lithium lanthanum zirconate (LLZ) and lithium cobalt oxide (LCO). The materials are applied to a metallic carrier foil by means of screen printing and then thermally post treated (dried and sintered) to produce adhesive layers or layer systems with the highest possible density. The conventional heat treatment is done in an oven process. Disadvantage of oven processes are the possible diffusion of the coating materials into adjacent layers due to long process times (in the range of minutes) at high temperatures and the high energy consumption. Furthermore, multilayer systems, containing different materials with varying decomposition temperatures, cannot be treated successfully.
For the construction of a battery cell, the preservation of the crystal structure and thus a suitable temperature management during the drying and sintering process are of enormous importance. By means of laser processing, short interaction times within the range of seconds and below are realised. High heating and cooling rates show potential for reducing diffusion processes and preserving the crystal structure of the materials.
In this work, the laser sintering of LLZ and LCO micro particle layers is presented, addressing the challenges of reaching a rather homogeneous temperature profile across the coating thickness within short processing times while preserving the materials integrity and bonding the layer to the substrate. The influence of different interaction times, scanning strategies as well as use of sintering additives on the crystal structure, the electrochemical properties and adhesion are investigated.