Ultra-Thin Lithium Silicide Interlayer for Solid-State Lithium-Metal Batteries.

All-solid-state batteries with metallic lithium (Li BCC ) anode and solid-electrolyte (SE) are under active development. However, an unstable SE/Li BCC interface due to electrochemical and mechanical instabilities hinders their operation. Herein, we demonstrate an ultra-thin nanoporous mixed ionic and electronic conductor (MIEC) interlayer (∼3.25 μm), which regulates Li BCC deposition and stripping, serving as a 3-dimensional (3D) scaffold for Li 0 ad-atom formation, Li BCC nucleation, and long-range transport of ions and electrons at SE/Li BCC interface. Consisting of lithium silicide and carbon nanotubes, our MIEC interlayer is thermodynamically stable against Li BCC and highly lithiophilic. Moreover, its nanopores (< 100 nm) confine the deposited Li BCC to the size regime where Li BCC exhibits "smaller is much softer" size-dependent plasticity governed by diffusive deformation mechanisms. The Li BCC thus remains soft enough not to mechanically penetrate SE in contact. Upon further plating, Li BCC grows in between the current collector and the MIEC interlayer, not directly contacting the SE. As a result, a full cell having Li 3.75 Si-CNT/Li BCC foil as an anode and LiNi 0.8 Co 0.1 Mn 0.1 O 2 as a cathode displays a high specific capacity of 207.8 mAh g -1 , 92.0% initial Coulombic efficiency, 88.9% capacity retention after 200 cycles (Coulombic efficiency reaches 99.9% after tens of cycles), and excellent rate capability (76% at 5C). This article is protected by copyright. All rights reserved.