Solid state battery using LISICON electrolyte with green-sheet technique

Abstract

Interface construction must provide electrochemical compatibility between solid electrolyte (oxide) and cathode/anode materials for all-solid-state batteries (ASSBs). Layered rock-salt oxides (cathode) have good compatibility with LISICON compound Li_3.5Ge_0.5V_0.5O₄. The crystal structures of layered rock-salt cathode and LISICON solid electrolyte solid remain almost unchanged even after co-firing at 973 K. Furthermore, mixtures after co-firing exhibited electrochemical activity closely resembling that of pristine cathodes. Based on these findings from experimentation, a green sheet process was conceived with cathode/electrolyte stacking layers prepared by tape casting, stacking, and co-sintering. The obtained laminated cathode/electrolyte composites were evaluated with a half-cell configuration using polymer electrolyte on the Li anode side at 333 K and 0.01C current density, revealing charge-discharge profiles closely resembling those of cathodes in an ordinary liquid electrolyte battery. The areal capacity increased almost in direct proportion to cathode particle loading, reaching approximately ∼1.2 mAhcm⁻². The Li ionic conductivity of the LISICON electrolyte is less than approximately 10⁻⁴ Scm, indicating that the solid electrolyte particles with LLZO garnet core and LISICON shell can be specially designed as a solid electrolyte with higher ionic conductivity. Using them as the electrolyte in laminated composites, we conducted brief charge-discharge experiments.