Extreme lithium-metal cycling enabled by a mixed ion- and electron-conducting garnet three-dimensional architecture.

The development of solid-state Li-metal batteries has been limited by the Li-metal plating and stripping rates and the tendency for dendrite shorts to form at commercially relevant current densities. To address this, we developed a single-phase mixed ion- and electron-conducting (MIEC) garnet with comparable Li-ion and electronic conductivities. We demonstrate that in a trilayer architecture with a porous MIEC framework supporting a thin, dense, garnet electrolyte, the critical current density can be increased to a previously unheard of 100 mA cm, with no dendrite-shorting. Additionally, we demonstrate that symmetric Li cells can be continuously cycled at a current density of 60 mA cm with a maximum per-cycle Li plating and stripping capacity of 30 mAh cm, which is 6× the capacity of state-of-the-art cathodes. Moreover, a cumulative Li plating capacity of 18.5 Ah cm was achieved with the MIEC/electrolyte/MIEC architecture, which if paired with a state-of-the-art cathode areal capacity of 5 mAh cm would yield a projected 3,700 cycles, significantly surpassing requirements for commercial electric vehicle battery lifetimes.