This study introduces 2D TiO₂ nanosheets as an effective protective layer to stabilize the cycling performance of lithium metal batteries. The nanosheet coating reduces the surface roughness and uniformly regulates lithium-ion flux, resulting in lithium dendrites suppression. Consequently, improved electrochemical performance with Coulombic efficiency of 97.6 % over 200 cycles were achieved for half-cell.

Abstract

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.