Oxidic Solid Electrolytes and Their Challenges for All-Solid-State Batteries

摘要

Highly conductive, electrochemical stable solid electrolytes are essential achieving significantly higher energy and power density as common Li-ion batteries. Meanwhile solid-state electrolytes improve safety due to the absence of flammable liquids. Two of the most promising materials are the oxidic Li-ion conductors Li7La2Zr3O12 (LLZO) and Li20-A1203-Ti02-P205 (LATP). They are chemical stable in dry air and common battery electrolytes. Cubic LLZO possesses a total ionic conductivity of 3x10-4 S/cm and stability against lithium metal. LATP is the material of interest for ionic conduction in cathodes. It has a grain-core conductivity of 1x10-3 S/cm, a total conductivity of 2x10-4 S/cm and excellent compatibility with most cathode materials. Both materials sufficiently prevent self-discharge of batteries as their electronic conductivity is 6 orders of magnitude lower than their ionic conductivity. Furthermore, their transference number of ~ 1 allows fast charging of batteries. One of the key challenges is the controlled processing of LLZO and LATP enabling low interfacial resistances against other solid-state battery components. For this purpose, surface contamination of particles and components manufactured from solid electrolyte materials has to be reduced as far as possible. Regarding these aspects, latest improvements by orders of magnitude based on advanced processing of such material will be shown. Proof of sufficient Li-ion conductivity will be reported.