Integrate multifunctional ionic sieve lithiated X zeolite-ionic liquid electrolyte for solid-state lithium metal batteries with ultralong lifespan

Solid-state lithium metal batteries with higher energy density and safety are regarded as the promising next-generation energy storage devices. Porous materials hybrid with ionic liquids are becoming an important solid electrolyte due to the high ionic conductivity and enhanced interfacial compatibility. However, their poor electrochemical stability and limited Li⁺ transport pathways remain challenged. Herein, an ionic-liquid-X zeolite hybrid is designed as the solid composite electrolyte to settle the above issues. The three-dimensional open framework of X zeolite acts as the “reservoir” of the ionic liquid providing a solid interconnected pathway to facilitate an effective lithium transmission. This transport is supported by both the TFSI⁻ adsorption and EMIM⁺ substitution in zeolite structure, which benefits the compatibility at electrolyte/lithium anode interface. The obtained composite electrolyte (Li-X-30) exhibits a superior ionic conductivity of 3.3 × 10⁻⁴ S·cm⁻¹ and a widened electrochemical window of 5.4 V. An ultralong lifespan of the assembled solid-state LiFePO₄//metallic lithium battery is achieved with an outstanding capacity retention of 96% after 850 cycles. The designed electrolyte with ultra-long cycling stability may provide inspiration for the development of frontier solid electrolytes with potential applications in K, Na and other types of energy storage systems.