A bifunctional composite artificial solid electrolyte interphase for high stable solid-state lithium batteries

Poor interfacial compatibility between lithium (Li) metal anode and solid electrolyte is the main obstacle for solid-state Li metal batteries. To address which prefabricating an artificial solid electrolyte interphase (SEI) film on the surface of lithium anode is an effective strategy. Here, a bifunctional composite artificial SEI film with high ionic conductivity and interface compatibility is provided via in-situ forming poly-1,3-dioxolane (PDOL)/reduced graphene oxide (rGO) composite film on the surface of Li metal. The flexible high-ionic conductive PDOL improves the physical contact between the solid electrolyte and Li metal anode, and the rigid rGO effectively promotes the uniform plating of lithium ion (Li+) and suppresses the growth of Li dendrites. This rigid/flexible composite artificial SEI film not only boosts the interfacial transport of Li+, but also improves the interfacial compatibility between Li metal anode and solid electrolyte. Matching with PDOL solid electrolyte, the composite SEI film helps the Li symmetric cells to cycle stably for more than 350 h at a high current density of 0.3 mA/cm2 and an areal capacity of 0.3 mAh/cm2. Compared with the discharge specific capacity of pure Li metal anode, the discharge specific capacity of the assembled NCM622/PDOL & rGO-Li cell is increased by 17.5% at 2 C. This bifunctional composite SEI film provides a new idea for the surface modification of lithium metal anode.