Redox-active ferrocene upgrading PEO electrolyte for durable all-solid-state lithium-metal batteries

Poly (ethylene oxide) (PEO)-based electrolytes are under intense research because of their high safety, low cost and easy to scale fabrication. But several barriers, such as the poor ionic conductivity, slow reaction kinetics and uneven lithium deposition, still prevent their practical implementation. Herein, ferrocene (Fc) is utilized as a novel redox mediator filler for PEO based-electrolyte to optimize the performance of all-solid-state Li-metal battery. In addition to enhancing the ionic conductivity of electrolyte via Fe-O coordination interaction and Licyclopentadienyl ligands cation-& pi; interaction, Fc can also regulate uniform lithium ionic flux over Li metal and inhibit lithium dendrite growth. Moreover, Fc can accelerate the electron transfer and reaction kinetic of LiFePO4 cathode because of its properties of electron-transfer mediator. As a result, the all-solid-state LiFePO4/PEO electrolyte/Li battery with the addition of Fc shows notable cycling stability. It delivers an initial capacity of 158.2 mAh g-1 at 0.5 C and maintains 146.1 mAh g-1 after 300 cycles with a high capacity retention of 92.5%. This work offers a convenient method for durable all-solid-state lithium-metal batteries.