Institution: | 1. Institute of Physical Chemistry, Justus-Liebig-University Giessen, 35392 Giessen, Germany
Center for Materials Research (ZfM), Justus-Liebig-University Giessen, 35392 Giessen, Germany;2. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109 USA
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109 USA;3. Institute of Physical Chemistry, Justus-Liebig-University Giessen, 35392 Giessen, Germany |
Abstract: | Controlling the lithium growth morphology in lithium reservoir-free cells (RFCs), so-called “anode-free” solid-state batteries, is of key interest to ensure stable battery operation. Despite several benefits of RFCs like improved energy density and easier fabrication, issues during the charging of the cell hinder the transition from lithium metal batteries with a lithium reservoir layer to RFCs. In RFCs, the lithium metal anode is plated during the first charging step at the interface between a metal current collector and the solid electrolyte, which is prone to highly heterogeneous growth instead of the desired homogeneous film-like growth. Herein, the lithium morphology during the first charging step in RFCs is explored as a function of current density and current collector thickness. Using operando scanning electron microscopy, an increase in the lithium particle density is observed with increasing current density at the Cu|Li6.25Al0.25La3Zr2O12 interface. This observation is then applied to improve the area coverage of lithium by pulsed plating. It is also shown that thin current collectors (d = 100 nm) are unsuited for RFCs, as lithium whiskers penetrate them, resulting in highly heterogeneous interfaces. This suggests the use of thicker metal layers (several µm) to mitigate whisker penetration and facilitate homogeneous lithium plating. |