Nickel Cluster-Based Organic Framework-Functionalized Solid-State Electrolyte for Lithium–Metal Batteries

The low ionic conductivity (σ) and poor capacity retention severely hinder the further application of solid-state electrolytes (SSEs) in lithium–metal batteries (LMBs). Herein, novel trinuclear cluster-based metal–organic frameworks (MOFs) with rich cage cavities and characteristic functional group −OH have been synthesized, Ni-MOF–OH (H2N (CH3) 22Ni3 (μ3-O) (XN) (BDC–OH) 3·7. 5 DMFn), and further modified with LiOH into Ni-MOF-OLi-1. The Ni-MOF-OLi-1 SSE exhibits a significant improvement in electrochemical performance with a higher σ of 1. 55 × 10–3 S cm–1, a wider electrochemical stability window of 5. 3 V, and a better Li+ transference number of 0. 69 in comparison with that of Ni-MOF–OH (5. 06 × 10–4 S cm–1, 4. 9 V, 0. 53) at 25 °C. Importantly, Ni-MOF-OLi-1 can maintain excellent σ of 2. 49 × 10–4 and 3. 18 × 10–3 S cm–1 at −40 and 100 °C, respectively. The activation energy (Ea) is as low as 0. 09 eV from 10 to 100 °C. Remarkably, the LiFePO4 (LFP) /Li cell assembled with the Ni-MOF-OLi-1 SSE demonstrates an outstanding capacity retention of 96. 33% after 150 charge–discharge cycles at 0. 5C and 25 °C. This work provides an effective path for the development of high-performance solid electrolytes of LMBs.