Hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte for high-performance lithium battery

Ionic liquids (ILs) hold great promise as high-performance electrolyte material due to their unique advantages including nonvolatility, high thermal stability and high ionic conductivity. However, the IL-based electrolytes always suffer from serious ion aggregation and high viscosity at low temperatures, leading to significantly decline in ionic conductivity. Here, hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte (high temperature treatment (HT)-HOF-IL CQSE) was prepared through confining the IL electrolytes (ILEs) into the pore of HOF lamellar framework. The weak hydrogen bonding interactions within HOF nanosheets, together with the generated interactions between ILE and HOF, enable uniform and continuous distribution of ILE in HOF lamellar framework. This effectively inhibits the ion migration of ILE, which meanwhile serves as Li⁺ transfer sites, affording high ionic conductivity of 5.7 × 10⁻⁵ S·cm⁻¹ at −60 °C, with high lithium-ion transference number of 0.69, whereas ILEs usually lose ionic conduction ability at such low temperatures. The assembled Li symmetrical cell can stably cycle at 0.2 mA·cm⁻² and −20 °C for more than 1500 h. The LiFePO₄|HT-HOF-IL CQSE|Li cell shows excellent cycling performance at 0.5 C at a wide temperature range of −20 to 60 °C. This work may pave a new avenue for the development of high-performance IL-based composite electrolytes.