Ultrathin two-dimensional (2D) porous nanosheets are one of the most promising nanomaterials in various applications, whereas their synthesis is still challenging. Herein, ultrathin 2D amorphous TiO 2 (a-TiO 2 ) porous nanosheet aerogel is synthesized via a surfactant-free assembly process followed by low-temperature calcination. The co-existing O-O and -OH groups on the surface of TiO 2 precursor break the 3D spherical symmetry, and the hydrogen bonding among the TiO 2 precursors is proposed as the main driving force guiding the 2D assembly. The surfactant-free assembly endows the ultrathin a-TiO 2 porous nanosheet with improved ionic and electronic conductivity. The porous structure provides high surface area and easy electrolyte penetration, accelerating the Li ion diffusion rate of the a-TiO 2 porous nanosheet. Attributing to the above advantages, the obtained a-TiO 2 porous nanosheets are one of the best anode materials for lithium-ion batteries, which is proved by the enhanced electrochemical performance.