Potential-Driven Selective Na Metal Deposition-Enabled Interphase with High Lithium Dendrite Suppression Capability

Voids formation during Li stripping and Li dendrite growth during Li plating are critical challenges that restrict the practical application of all-solid-state Li-metal batteries (ASSLBs). Extensive research efforts typically address these issues in isolation, thereby limiting the ability of ASSLBs to achieve a stable cyclic performance under low stack pressure. Herein, we address these two challenges simultaneously by using hard carbon-Sn (HC-Sn) as an interlayer and LiNa as an anode. After Li plating/stripping cycles, the Li₆PS₅Cl/HC-Sn/LiNa in situ transfers to the Li₆PS₅Cl/[HC-Li_<i>x</i>Sn]Na/Na/LiNa structure, where [HC-Li_<i>x</i>Sn]Na represents HC-Li_<i>x</i>Sn embedded within the sodium metal. The fast Li⁺ diffusivity of HC-Li_<i>x</i>Sn promotes uniform Li deposition at the [HC-Li_<i>x</i>Sn]Na/Na interface, while the soft Na in the HC-Li_<i>x</i>Sn layer and at the [HC-Li_<i>x</i>Sn]Na/LiNa interface suppresses void formation during Li stripping, thus, high lithium dendrite suppression capability is achieved in Li₆PS₅Cl/HC-Sn/LiNa. As a result, the LiNa/HC-Sn/Li₆PS₅Cl/HC-Sn/LiNa symmetric cell shows stable Li plating/stripping cycles of 1184 h at 1.0 mA cm^-2/4.0 mAh cm^-2 under a low stack pressure of 2.0 MPa. The Co_0.1Fe_0.9S₂/Li₆PS₅Cl/HC-Sn/LiNa cell shows high cycling stability with a capacity retention of 90.0% after 1000 cycles at an areal capacity of ∼1.5 mAh cm^-2 and a high reversible capacity of 3.14 mAh cm^-2 after 300 cycles at an areal capacity of ∼4.0 mAh cm^-2 under the same low stack pressure of 2.0 MPa. This work provides a strategy to design ASSLSBs with a long cycle life at low stack pressure for practical application.