Hydrogen-bonded organic framework-lithium salt array for rapid lithium ion transport in all-solid-state lithium battery

Abstract Hydrogen-bonded organic frameworks (HOFs) have recently emerged as attractive candidates for solid-state electrolytes (SSEs) due to their structurally ordered pores, tunable chemical structures, and solution processability. However, direct application of HOFs as SSEs is challenging because of the lack of mobile Li+ and low-energy-barrier transport pathways. Herein, we design and fabricate a HOF-lithium salt array SSE with efficient Li+ transport properties through integrating lithium salts (Li-salts) into the hydrogen bond networks of HOF nanosheets as conducting sites. Li-salt anions with different electronegativities (bis(trifluoromethanesulfonyl)imide (TFSI−), tetrafluoroborate (BF4−), and hexafluorophosphate (PF6−)) are utilized to investigate their influence on transport environment and Li+ conductivity. We demonstrate that the strong hydrogen bond interactions between anions and HOF nanosheets provide a loose coordination environment for Li+, enabling efficient Li+ transport. Superior ionic conductivity of 1.0 × 10−4 S·cm−1 at 30 °C and high Li-ion transference number ( tLi+) (0.63) are achieved for the optimized SSE. Consequently, the assembled Li|HOF-LiTFSI|Li cell can stably cycle for over 1000 h at 0.5 mAh·cm−2. The lithium iron phosphate (LFP)|HOF-LiTFSI|Li half-cell exhibits a satisfactory discharge specific capacity of 161.1 mAh·g−1 with a high capacity retention of 99.0% after 300 cycles at 0.5 C and 25 °C. This work highlights the great potential of flexible HOFs as high-performance solid-state electrolyte materials.