TiO₂ Nanofiber-Modified Lithium Metal Composite Anode for Solid-State Lithium Batteries

Solid-state lithium metal batteries (SSLMBs), using lithium metal as the anode and garnet-structured Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) as the electrolyte, are attractive and promising due to their high energy density and safety. However, the interface contact between the lithium metal and LLZTO is a major obstacle to the performance of SSLMBs. Here, we successfully improve the interface wettability by introducing one-dimensional (1D) TiO₂ nanofibers into the lithium metal to obtain a Li-lithiated TiO₂ composite anode (Li-TiO₂). When 10 wt % TiO₂ nanofibers are added, the formed composite anode offers a seamless interface contact with LLZTO and enables an interfacial resistance of 27 Ω cm², which is much smaller than 374 Ω cm² of pristine lithium metal. Due to the enhanced interface wettability, the symmetric Li-TiO₂|LLZTO|Li-TiO₂ cell upgrades the critical current density to 2.2 mA cm^-2 and endures stable cycling over 550 h. Furthermore, by coupling the Li-TiO₂ composite anode with the LiFePO₄ cathode, the full cell shows stable cycling performance. This work proves the role of TiO₂ nanofibers in enhancing the interface contact between the garnet electrolyte and the lithium metal anode and improving the performance of SSLMBs and provides an effective approach with 1D additives for solving the interface issues.