Multiscale Optimization of Li-ion Diffusion in Solid Lithium Metal Battery via Ion Conductive Metal-organic Frameworks

Optimization of solid electrolyte (SE) is of great significance for lithium solid state batteries (SSBs). However, insufficient Li ion transport, deficient interfacial compatibility and formation of lithium dendrites lead to poor cycling performance. Based on Li+ conductive metal-organic frameworks (LCMOFs), herein a multiscale optimization strategy is put forward to facilitate Li+ transport within the MOFs (molecular scale), between the MOFs’ boundaries (nano-scale) and across the interface of SE/electrode (micro-scale) in SSB. LCMOFs are obtained by binding Li+ onto ionogenic chemical groups (-CO2H, -SO3H and -OH) in nanoscale dispersed MOFs. Both experimental results and DFT simulations confirm the key role of ionogenic groups for Li+ transport. Furthermore, benefiting from the ameliorative interfaces between LCMOF crystals, SE with excellent electrochemical properties are obtained, including a high ionic conductivity of 1.06 × 10−3 S cm−1 at 25 °C, a wide electrochemical window from 2.0 to 4.5 V, low interfacial resistances and stable Li plating/stripping. The fabricated Li|SE|LiFePO4 SSB exhibits high and stable charge/discharge capacities under wide operation temperature ranging from -20 to 60 °C.