High-Rate and Stable LLZO-Based Lithium–Metal Batteries Enabled via a Tin Interlayer

Lithium–metal batteries with solid electrolyte separators promise improvements in energy density, fast charge capability, and safety. However, the lack of control of the solid electrolyte–lithium–metal interface continues to impede development. Interlayers between lithium–metal and the solid electrolyte are reported to improve performance but have limitations due to stability, rate limitations, and the use of undesirable elements (e.g., Ag, Au). Here, we show that a thin layer of the abundant metal Sn provides the required stability and transport properties to enable commercially relevant current densities (5 mA cm–2) and external pressures (0.3 MPa) at room temperature in Li7La3Zr7O12 (LLZO) hybrid cells. Moreover, these Sn interlayer full cells constructed with NMC cathodes (areal capacity of ∼2.5 mAh cm–2) show no capacity loss for over 500 cycles under symmetric C/3 cycling. Both the interlayer phase behavior and Li transport properties are proposed to underpin the performance of metal-alloy interlayers as indicated by electrochemical and in situ and ex situ characterization techniques.