Efficient Construction of a C Interlayer for Mechanically Robust, Dendrite-free, and Ultrastable Solid-State Batteries.

Interfacial instability between solid electrolytes (SEs) and lithium metal remains a daunting challenge for solid-sate batteries. Here, a conformal C interlayer is efficiently constructed on LiAlGe(PO) (LAGP) SEs by physical vapor deposition, and an ideal interfacial contact is achieved via forming an ionically conducting matrix of LiC with lithium metal. The obtained LiC is beneficial to hinder the growth of lithium dendrites at interface and release the local stress during the lithiation and delithiation. As a result, the Li/LAGP-C/Li symmetric cells demonstrate ultra-stable cycling performance for more than 4,500 h at a current density of 0.034 mA cm. The Li/LAGP-C/LiFePO full cells deliver a reversible capacity of 152.4 mAh g at room temperature, and the capacity retention rate is 85% after more than 100 cycles. This work provides a feasible and scalable strategy to improve the SEs/Li interface for high-performance solid-state batteries.