Metastable Decomposition Realizing Dendrite‐Free Solid‐State Li Metal Batteries

A stable interface and preventing dendrite-growth are two crucial factors to realize long-life all-solid-state Li batteries (ASSLBs) using sulfide-based solid electrolytes (SEs) and Li metal anodes. But it remains a challenge to accomplish the two factors simultaneously. Here, an effective strategy is reported to realize this goal in Li-argyrodites via self-engineered metastable decomposition that is enabled by Si doping in Cl-rich argyrodites. It is shown that Cl atoms in the lattice become metastable and are highly reactive with Li atoms. The locally deposited/grown Li crystal nuclei are thus depleted by the metastable Cl during electrochemical cycling, in situ generating electrically insulated LiCl shells concentrated at the argyrodite grain boundaries. The shells in turn prevent the autochthonous Li redeposition and act as self-protective layers to restrain the continuous decomposition in the interior argyrodite, that is, self-assembly of reactive-cores-stable-shells to Li metal, thereby enabling an ultra-long life ASSLB using Li metal anodes at room temperature under relatively high current densities.