Stabilizing a Li_1.3Al_0.3Ti_1.7(PO₄)_{3/Li metal anode interface in solid-state batteries with a LiF/Cu-rich multifunctional interlayer}

Li1.3Al0.3Ti1.7(PO4)(3) (LATP) has attracted much attention due to its high ionic conductivity, good air stability and low cost. However, the practical application of LATP in all-solid-state lithium batteries faces serious challenges, such as high incompatibility with lithium metal and high interfacial impedance. Herein, a CuF2 composite layer was constructed at a Li/LATP interface by a simple drop coating method. CuF2 in the interlayer reacts with lithium metal in situ to form a multifunctional interface rich in Cu and LiF. The multifunctional layer not only brings about close interfacial contact between LATP and Li metal, but also effectively prevents the electrochemical reaction of LATP with Li metal, and suppresses the electron tunneling and dendrite growth at the interface. The interfacial resistance of Li/CuF2@LATP/Li symmetric batteries is significantly reduced from 562 to 92 Omega, and the critical current density is increased to 1.7 mA cm(-2). An impressive stable cycle performance of over 6000 h at 0.1 mA cm(-2)/0.1 mA h cm(-2), 2200 h at 0.2 mA cm(-2)/0.2 mA h cm(-2) and 1600 h at 0.3 mA cm(-2)/0.3 mA h cm(-2) is achieved. Full batteries of LiFePO4/CuF2@LATP/Li also show a high capacity retention ratio of 80.3% after 540 cycles at 25 degrees C. This work provides an effective and simple composite layer solution to address the interfacial problem of Li/LATP.