Constructing TiO2 nanotube arrays with oxygen vacancies on a Cu mesh to enable homogeneous Li deposition towards a long-life Li metal anode

Abstract

The high nucleation energy barrier and nonuniform electric field distribution, which will result in uncontrollable growth of Li dendrites and the evolution of dead Li, are the main existing issues that restricted the application of a Li metal anode. A three-dimensional current collector with a large specific surface area can reduce the local current density on the electrode surface and delay the growth of lithium dendrites, while surface lithiophilicity modification is conducive to promoting Li nucleation, thus preventing the generation of dendrites and facilitating uniform Li deposition. In this work, titanium dioxide (TiO₂) nanotube arrays with oxygen vacancies are constructed on a Cu mesh (Cu@TNT), which can serve both as a matrix for the Li metal anode and a current collector. The 3D structure can provide a buffer space for Li during the plating/stripping process, relieving the negative impact of volume change. The large specific surface area of TiO₂ nanotube arrays can reduce the local current density on the electrode surface. TiO₂ with good lithiophilicity can reduce the nucleation overpotential of Li, promoting uniform Li deposition, while the oxygen vacancies on TiO₂ nanotubes can improve electrical conductivity of TiO₂ and increase the adsorption sites of Li ions, which are beneficial to more uniform Li deposition. All these bring a low Li nucleation overpotential of 0.044 V at 1 mA cm⁻², a high Coulombic efficiency of 99.2%, as well as a high cycling stability of over 800 h at 1 mA h cm⁻². The full cell assembled with high loading LiFePO₄ also possesses good cycling stability with a capacity retention rate of 91.87% after 350 cycles at 1C, and fine rate capability.