Temperature dependent flux balance of the Li/Li7La3Zr2O12 interface

Abstract The potential for safe, high energy-density Li-ion batteries has motivated the development of the solid electrolyte Li 7 La 3 Zr 2 O 12 (LLZO) to physically stabilize the Li-electrolyte interface. Although dense LLZO is a relatively hard ceramic, it has been observed that above a certain critical current density (CCD), Li metal can still propagate through both polycrystalline and single crystalline LLZO. However, reported values of CCD are still well below the current density regimes relevant to applications like electric vehicles (≥3 mA cm −2 ). The relationship between CCD and temperature was studied using recently developed methods for achieving consistently low interfacial impedances without interfacial coatings that can complicate the analysis of what controls interface stability. By analyzing the flux of Li + ions at the Li-electrolyte interface, it is hypothesized here that solid-state diffusivity of Li in the Li electrode may be a governing mechanism that controls the CCD. These results demonstrate an improvement for dendrite-free cycling in LLZO up to ∼1 mA cm −2 at room temperature and ∼7 mA cm −2 at 100 °C without the need for coatings to achieve low interface resistances (∼10 Ω cm 2 ). Furthermore, the presented analysis may provide additional insight on the role of Li diffusivity in Li propagation through ceramic electrolytes.