Hybrid covalent organic-framework-based electrolytes for optimizing interface resistance in solid-state lithium-ion batteries

High ion conductivity and low electrode-electrolyte interface resistance are intensively pursued topics for the development of solid-state Li-ion batteries with high safety and energy density. Here, we propose a design using keto-enamine covalent organic frameworks (TPBD) and polyethylene oxide (PEO) to prepare a solid-state electrolyte (TPBD-LiPF6@PEO), achieving a high ion conductivity of 0.543 mS cm−1 at 25°C and optimizing the electrode-electrolyte interface resistance in Li-ion batteries. Solid-state nuclear magnetic resonance experiments and density functional theory calculations show that the strong interaction between the –C=O site in TPBD and Li+ ions promotes the dissociation of LiPF6. The assembled LiFePO4|TPBD-LiPF6@PEO|Li batteries without using liquid electrolytes offer a specific capacity of nearly 140 mAh g−1 at 0.2 C with a columbic efficiency of 99.6% after 200 cycles at 25°C. This strategy for preparing solid-state electrolytes provides practical ideas and suggestions in the development of solid-state energy devices.