Ultrathin amorphous TiO₂ nanofilm-coated graphene with superior electrochemical performance for lithium-ion batteries

As a novel anode material for lithium-ion batteries, graphene has a higher theoretical capacity than graphite. However, the practical application of graphene suffers from a low coulombic efficiency and poor cycle stability due to the unstable solid electrolyte interphase layer. In this work, ultrathin amorphous TiO₂ nanofilm-coated graphene is fabricated by controlled hydrolysis of tetrabutyl titanate on the surface of graphene, and shows superior cycle and rate performance compared to uncoated graphene because amorphous TiO₂ nanofilms can prevent the detachment of graphene nanosheets and avoids the formation of thick and unstable solid-electrolyte interphase layers during cycling. Moreover, the electrochemical performance of TiO₂-coated graphene can be further improved by controllable calcination of TiO₂-coated graphene under a N₂ atmosphere. The produced porosity of TiO₂ nanofilms after calcination can improve both Li⁺ and electron transport, leading to the further improved lithium storage performance of graphene. This novel synthesis strategy may be employed in other graphene-based anode materials for high-performance lithium-ion batteries and other electrochemical devices. - Highlights: • Amorphous TiO₂ nanofilms are fabricated by hydrolysis of tetrabutyl titanate on the surface of graphene. • TiO₂ nanofilms are broken in some regions to form crystalline TiO₂ nanoparticles after annealing under N₂. • TiO₂-coated graphene shows superior electrochemical performance compared to pure graphene. • TiO₂-coated graphene can be used as flexible anode materials due to the amorphous nature of TiO₂ coating.