Engineering Current Collector with 2D TiO₂ Nanosheets for Stable Lithium Metal Batteries

The formation of lithium dendrites, driven by the non-uniform deposition of lithium, remains a critical challenge for the performance and safety of lithium metal batteries. To address this issue, we engineer the surface of copper current collectors by depositing ultra-thin 2D TiO2 nanosheets with varying thicknesses (0–1200 nm) as a protective layer. Half-cells without the 2D TiO2 coating exhibit a significant decline in Coulombic efficiency after only 65 charge-discharge cycles. In contrast, the modified current collector with the smoothest surface achieves remarkable cycling stability, maintaining ~97.6 % Coulombic efficiency after 200 cycles. Full cells incorporating these nanosheets demonstrate a good discharge capacity of ~134 mAh/g after 150 cycles at a 1 C rate. The improved electrochemical performance is attributed to the high lithium affinity and reduced surface roughness of the current collector facilitated by the 2D TiO₂ buffer layer. These findings emphasize the crucial role of 2D TiO₂ nanosheets in regulating Li-ion deposition, thereby significantly improving the cycling stability and performance of lithium metal batteries.