Directional Modification-Functionalized Metal-Organic Framework Solid-State Electrolytes for Highly Stable Li-O₂ Batteries

Metal-organic frameworks (MOFs) with accurately directional and well-ordered channels are considered ideal solid-state Li-ion conductors and are expected to be utilized in solid-state lithium-oxygen (Li-O-2) batteries to achieve rechargeable batteries with high energy density. However, the instability of MOFs toward air and lithium metal has become a crucial problem to overcome. Herein, a breakthrough is first realized in overcoming these challenges by utilizing cationic MOF (CMOF) as an advanced Li-ion conductor. Benefiting from the positively charged sites in the CMOF, an outstanding Li+ conductivity of 6.45 x 10(-4) S cm(-1) at room temperature, a low activation energy of 0.15 eV, and a high transference number of 0.59 are achieved. In particular, the CMOF shows high flame retardancy, H2O, and O-2(-) stability, which are key factors that affect the battery performance of Li-O-2 batteries. Such extraordinary Li+ transport makes the assembled solid-state Li-O-2 battery cycle up to 790 h with a low overpotential of 1.09 V. The proposed novel directional modification strategy is of great significance to developing high-performance SSEs for solid-state Li-O-2 batteries and other lithium batteries.