Mixed ionic/electronic conducting framework enabled by transition metal-ion reduction in Li-LLTO composite anodes for ultrafast lithium diffusion
The unstable Li/LLZO interface during lithium stripping and plating impedes interfacial charge transport and accelerates dendrite growth, limiting the development of LLZO solid electrolytes. A freestanding ultrathin Li-Li0.3La0.5TiO3 (LLTO) composite anode with a three-dimensional interconnected mixed ionic/electronic conducting LLTO framework was developed. The mixed conduction arises from in-situ reduction of Ti4+ by metallic lithium. The composite anode exhibits good affinity toward LLZO, achieving a low interfacial resistance of 11.7 Ω cm2 and a lithium self-diffusion coefficient of 4.5×10−11 cm2/s, about one order of magnitude higher than pure lithium. These features enhance Li-LLTO/LLZO interfacial stability, increasing the critical current density fourfold and enabling a 1300-h symmetrical cell cycling life. Solid-state lithium batteries with this anode deliver 80% capacity retention after 220 cycles. This advancement improves lithium metal anode performance in solid-state batteries and offers insights for next-generation high-energy-density electrochemical energy storage systems.