High-performance MOF-derived polymer electrolytes with modified ionic transport for solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) have been considered as promising candidates for large-scale applications in solid-state lithium metal batteries (SSLMBs) due to their flexibility, interfacial compatibility, and processability. However, their low ionic conductivity and poor resistance to dendrites limit their further commercial applications. In this study, a novel SPE (MOF-PISE) composed of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (P14TFSI) ionic liquid and a three-dimensional nanoflower-like metal-organic framework (NiCo-MOF) is proposed to address these issues. Under the combined impact of NiCo-MOF and P14TFSI, the crystallinity of PVDF-HFP is dramatically reduced, leading to a superior ionic conductivity of 0.68 mS cm-1 for MOF-PISE. In addition, the strong coordination between NiCo-MOF and P14TFSI greatly inhibits TFSI- anion and facilitates the migration of Li+, leading to improved Li+ transfer and enhanced Li+ transference number (tLi+, 0.49). The unique structure of NiCo-MOF endows SPE with excellent mechanical properties, greatly inhibiting the growth of dendrites. The smooth Li+ transport and dendrite inhibition properties of MOF-PISE enable it to exhibit excellent electrochemical stability in long-term cycling. Therefore, the MOF-PISE-based LiFePO4 (LFP)// Li cell demonstrates extraordinary cycling stability at room temperature (RT), with a capacity retention rate of 92.7 % after 800 cycles at 0.5C. Furthermore, the LFP/MOF-PISE/Li cell exhibits a remarkable discharge capacity of 158.5 mAh g- 1 at room temperature at 0.1C. It demonstrates an outstanding capacity of 147.9 mAh g- 1 under a high temperature of 100 degrees C at 3C, and its capacity remains 87.5 % after cycling 600 times. In addition, the scale-up LFP/MOF-PISE/Li pouch cell shows remarkable cycling stability and safety. High-voltage LiNi0.33Mn0.33Co0.33O2 (NCM111)//Li cell based on MOF-PISE also exhibits remarkable cycling and rate performance. The investigation of MOF-PISE in this study advances the research on high-performance SSLMBs.