Development and characterization of half-cells based on thin solid state ionic conductors for Li-ion batteries

Abstract In this study, tape casting has been used to produce thin electrolyte and electrode sheets which were then assembled as half-cells by co-sintering. As a solid electrolyte, Li 0.33 La 0.557 TiO 3 (LLTO), which features a high ionic conductivity between 10 −5  S/cm and 10 −3  S/cm at room temperature, was used. The spinel Li 4 Ti 5 O 12 (LTO) was selected as electrode material, since it is chemically similar to the electrolyte and therefore no undesired foreign phases are expected to occur at the interface. The key challenge was to adjust the processing parameters such that a clean and homogeneous interface forms between LTO and LLTO, even though these materials have different densification properties. Our results demonstrate that it is possible to produce co-sintered crack-free half-cells from LTO and LLTO green tapes. With a thickness of only 25 μm, a very thin electrolyte was realised, maximizing the ionic conductivity of the electrolyte. High co-sintering temperatures, needed to obtain a dense electrolyte, lead to a phase transition in LTO, which causes a drop in ionic conductivity. However, the even at high temperatures still open porosity of the anode offers void for additives, that could provide the necessary electronic and ionic conductivity.