Rapid sintering of Li6.5La3Zr1Nb0.5Ce0.25Ti0.25O12 for high density lithium garnet electrolytes with current induced in situ interfacial resistance reduction

Abstract

A primary target of energy storage is the all solid state battery, however finding a suitable solid state electrolyte has proven troublesome. Lithium garnet materials are promising solid state electrolytes with high room temperature conductivity, a wide electrochemical window, high chemical stability with Li metal and have minimal hazards. However, lithium garnets suffer from slow, energy demanding synthesis, rapid proton exchange (leading to high interfacial resistance between the garnet and electrodes), mechanical instabilities with Li metal and require specific handling methods to achieve the highest performing materials (such as full processing under Ar). Here we report a Ti/Ce co-doped high entropy lithium garnet material with four B site dopants, with the formula Li_6.5La₃Zr₁Nb_0.5Ce_0.25Ti_0.25O₁₂. This material benefits from rapid simultaneous sintering and densification directly from the starting materials, allowing formation of dense pellets in <1 hour at 1100 °C using only a standard, cheap, muffle furnace. Li_6.5La₃Zr₁Nb_0.5Ce_0.25Ti_0.25O₁₂ also has high conductivity (0.5 mS cm⁻¹ at 25 °C), scalability and insensitivity to both rapid furnace ramp rates and long dwell times. There is also an indication of unusual behaviour towards limiting lithium dendrite propagation, which is also discussed.