Interfacial Engineering with Li 4 Ti 5 O 12 -Modified Separators for Lithium Metal Batteries toward Enhanced Cycle Stability

Metallic Li is considered a promising anode material for high-energy batteries due to its extremely high theoretical capacity and lowest electrochemical potential. However, the commercialization of lithium metal batteries faces significant challenges, primarily due to uncontrollable growth of lithium dendrites and substantial volume changes during charge and discharge, which result in poor safety, low stability, and limited cycle life. Here, a spinel-type Li 4 Ti 5 O 12 (LTO) coating was prepared by a simple high-temperature solid-phase method and attached to the separator surface of lithium metal batteries as a coating through a mechanical coating approach. Benefiting from its improved electrolyte wettability and high ionic conductivity of the modified coating, it exhibited a low interfacial resistance, enabling lithium ions to rapidly penetrate the coating and maintaining a uniform lithium-ion flux at the electrode interface. It alleviated the growth of Li dendrites caused by the uneven distribution of lithium ions and mitigated the volume change. This composite coating achieves excellent cycling performance in half-cells, symmetric cells and button-type full cells. At a current density of 0.5 mA cm –2 and a capacity of 1 mAh cm –2, the Li/PP@LTO||Cu battery achieves stable cycling for over 180 cycles with a Coulombic efficiency maintained at 98%. At current densities of 1 mA cm –2 and capacity of 1 mAh cm –2, the Li/PP@LTO||Li/PP@LTO composite symmetric battery can stably cycle for 900 h with a polarization voltage stabilized at 25 mV. This work demonstrates a straightforward approach to develop dendrite-free lithium metal anodes, addressing the critical challenges of interface instability in lithium metal batteries.