A hybrid solid-state electrolyte endows a Li metal battery with excellent cycling life at 120 °C

Abstract

Lithium-ion batteries (LIBs) equipped with conventional polyolefin separators and organic liquid electrolytes present severely limited high-temperature performances owing to their intrinsic drawbacks of poor thermal stability and high flammability, which can easily cause safety issues of combustion or even explosion. Here, a hybrid solid-state electrolyte (HSSE) is designed by introducing an aluminum-based metal–organic framework (MOF) material. The carefully selected Al-MOF not only exhibits a high-temperature stable microporous structure but also exposes open Al³⁺ coordination sites after activation. The activated MOF can effectively coordinate anions and solvent molecules, which confines the migration of anions and free solvents but dramatically accelerates the Li⁺ transportation (high transference numbers, t_Li⁺ = 0.84), simultaneously inhibiting the side reactions at the interface of electrode/electrolyte. As a result, the nonflammable HSSE shows excellent electrochemical stability (>5.5 V), good ionic conductivity (2.0 × 10⁻⁴ S cm⁻¹), and favorable mechanical stability in wide temperature regions. Compared to a LiFePO₄‖Li cell with a liquid electrolyte that quickly failed in several cycles at 120 °C, the cell with the HSSE keeps cycling for 200 cycles with a capacity retention of 90% and an average coulombic efficiency of 99%. This work sheds light on the practical application of LIBs under extreme high-temperature conditions.