Mesoporous and Nanostructured TiO₂ layer with Ultra-High Loading on Nitrogen-Doped Carbon Foams as Flexible and Free-Standing Electrodes for Lithium-Ion Batteries

A simple and green method is developed for the preparation of nanostructured TiO₂ supported on nitrogen-doped carbon foams (NCFs) as a free-standing and flexible electrode for lithium-ion batteries (LIBs), in which the TiO₂ with 2.5–4 times higher loading than the conventional TiO₂-based flexible electrodes acts as the active material. In addition, the NCFs act as a flexible substrate and efficient conductive networks. The nanocrystalline TiO₂ with a uniform size of ≈10 nm form a mesoporous layer covering the wall of the carbon foam. When used directly as a flexible electrode in a LIB, a capacity of 188 mA h g⁻¹ is achieved at a current density of 200 mA g⁻¹ for a potential window of 1.0–3.0 V, and a specific capacity of 149 mA h g⁻¹ after 100 cycles at a current density of 1000 mA g⁻¹ is maintained. The highly conductive NCF and flexible network, the mesoporous structure and nanocrystalline size of the TiO₂ phase, the firm adhesion of TiO₂ over the wall of the NCFs, the small volume change in the TiO₂ during the charge/discharge processes, and the high cut-off potential contribute to the excellent capacity, rate capability, and cycling stability of the TiO₂/NCFs flexible electrode.