Ultrafine TiO2 Nanoparticles Confined in N‐Doped Porous Carbon Networks as Anodes of High‐Performance Sodium‐Ion Batteries

Abstract

AbstractTiO2‐based nanocomposites with rationally designed size, structure, and composition are highly desirable for Na‐ion storage. In this work, various TiO2/N‐doped porous carbon nanocomposites (TiO2/NC) have been fabricated by directly carbonizing NH2‐MIL‐125(Ti) at different temperatures. These TiO2/NC nanocomposites exhibit unique structure features, such as ultrafine TiO2 nanoparticles, micro‐mesoporous structure, and N‐doped carbon coating, which can shorten the Na‐ion diffusion distance, enhance the electronic conductivity, and prevent nano‐sized TiO2 from aggregation. When applied as sodium‐ion battery anodes, TiO2/NC‐600 exhibits the best sodium storage properties among the TiO2/NC nanocomposites produced at different carbonization temperatures. Correlations between electrochemical properties and size/structure/composition of the TiO2/NC nanocomposites are disclosed. TiO2/NC‐600 delivers a high reversible capacity of 190 mA h g−1 for up to 500 cycles at 1 C (1 C=335 mA g−1), an ultrahigh capacity of 76 mA h g−1 at a high rate of 20 C, and an excellent long‐term cycling stability with a capacity of 159 mA h g−1 retained after 2500 cycles at 5 C. The outstanding sodium storage performance of TiO2/NC‐600 is attributed to an appropriate crystalline structure, particle size, and high nitrogen‐doping content.