Laser sintering of ceramic-based solid-state battery materials

Abstract

Solid-state batteries (SSBs) are a promising technology for high travelling ranges and safety in future electromobility. In SSBs, separator and liquid electrolyte materials are combined in a solid-state electrolyte layer. Possible materials for SSBs are ceramic oxides, for example LiCoO2 (LCO) as cathode material and Li7La3Zr2O12 (LLZO) as electrolyte material. By means of screen printing, a mixed cathode material (mixture of cathode and electrolyte material to have higher ionic conductivity in the cathode) is applied on a stainless steel current collector foil and after thermal processing, the electrolyte material is printed on top of the sintered mixed cathode to create a half-cell. Both layers are thermally post treated (dried and sintered) in consecutive steps to produce functional layers for SSBs. Conventional heat treatment is done in an oven process. A main disadvantage is the diffusion of materials into adjacent layers due to long process times (range of minutes) at high temperatures. Furthermore, the battery half-cell cannot be treated at high temperatures due to incompatibilities in decomposition temperatures of LLZO and LCO. Preservation of the crystal structure and a suitable temperature management during the sintering process are of enormous importance. By means of laser processing, short interaction times (range of seconds and below) are realized. High heating rates show potential for reducing diffusion processes and preserving the crystal structure of the materials. In this work, the influence of different interaction times on crystal structure and adhesion are investigated for laser sintering of LLZO and LCO micro particle layers.