Gram-scale carbothermic control of LLZO garnet solid electrolyte particle size

Abstract

In recent years, solid electrolytes have become an enticing alternative to liquid electrolytes in lithium based batteries. However, the high synthesis temperatures and difficult optimization of solid-state electrolytes are a significant drawback in a high-scale application. In this work, we demonstrate that the synthesis process of garnet-based Li7La3Zr2O12 (LLZO) electrolyte can be accelerated while reducing the formation temperature of cubic LLZO to about 720 °C from a standard temperature of 780 °C by supplementing the process with a carbon additive. These carbon-rich LLZO samples have a homogeneous particle distribution with a decreased average size, which is influenced by the type of carbon additive itself. The materials with high carbon content show an improved densification after hot-pressing at a low temperature of 800 °C, which is reflected in their electrochemical performance, since LLZO sample with 10% of DENKA carbon additive shows a total ionic conductivity of 5.95 × 10−5 S cm−1, about 40% higher than the one of carbon-free LLZO (3.53 × 10−5 S cm−1).