A Ba_0.5Sr_0.5TiO₃ Interlayer Enabling Ultra-Stable Performance in Hybrid Solid–Liquid Lithium Metal Batteries

Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a promising solid-state electrolyte for next-generation solid-state lithium metal batteries, offering high ionic conductivity, superior air stability, and low cost. However, its practical application is hindered by high interface impedance due to rigid solid–solid contact with electrodes and instability when in contact with lithium metal. Here, a hybrid solid–liquid electrolyte is designed, consisting of a porous 3D LATP skeleton infiltrated with carbonate-based organic electrolyte, to ensure sufficient electrolyte wettability. Further, the thermodynamic instability between LATP and Li is solved by magnetron sputtering a layer of ferroelectric Ba_0.5Sr_0.5TiO₃ (BST) onto the LATP surface. This BST interlayer prevents direct contact between LATP and Li metal, enhancing performance by dynamically regulating Li⁺ deposition, inhibiting dendrite growth, reducing overpotential and interface resistance, and improving Li⁺ transport. Compared to the LATP-based electrolyte (LATP-LE), the BST-modified hybrid electrolyte (B@LATP-LE) demonstrates largely improved ionic conductivity (0.42 to 1.38 mS cm⁻¹) and outstanding electrochemical performance, achieving stable cycling for over 7000 h in LiLi cells and superior stability in LiFePO₄Li and LiNi_0.8Co_0.1Mn_0.1O₂Li full cells. This approach offers a cost-effective solution to the interface issues of LATP and provides insights for high-performance lithium metal batteries.