Investigation of in-situ lithium dendrite growth in the garnet type electrolyte Li7-xLa3Zr2-xTaxO12 (LLZTO) under an applied DC voltage

Abstract

A translucent Al-containing garnet type electrolyte (Al-LLZTO) with high lithium-ion conductivity was made by pressure filtration followed by sintering to study in-situ lithium dendrite growth. A transparent tube furnace was built for in-situ dendrite growth studies above room temperature. In-situ lithium dendrite growth in a garnet-type electrolyte under an applied DC voltage was investigated at three different temperatures (room temperature, 100 °C, and 200 °C (above the melting point of lithium)). Critical current density (CCD) was estimated based on a previous model developed for sodium dendrites (which are actually filaments) in Na-β”-alumina. The CCD defined here is different than most of the reported work in lithium and lithium-ion batteries. When the temperature is higher than room temperature but lower than the melting point of lithium, lithium dendrites grow rapidly. However, when the temperature is above the melting point of lithium, no lithium dendrites were observed under similar testing conditions. This is because the CCD for liquid lithium dendrites to form is much higher than that for solid lithium dendrites to form. Approximate estimates of the CCD below and above the melting point of lithium are also given. This investigation provides significant insights into dendrite (filament) growth above room temperature, and possible prevention of lithium dendrites in working solid-state lithium-ion batteries, and the efficiency improvement of solid-state batteries.