Ti-Doped Ultra-Small CoO Nanoparticles Embedded in an Octahedral Carbon Matrix with Enhanced Lithium and Sodium Storage

Herein, we demonstrate the synthesis of ultra-small Ti-doped CoO nanoparticles, embedded in an octahedral carbon matrix, (Ti-doped-CoO@C) by pyrolyzing a Co-Ti-bimetallic metal-organic framework (MOF). The results reveal that optimal pyrolysis resulted in the uniform distribution of the CoO nanoparticles (similar to 10 nm) in an octahedral carbon matrix. Ti-doping enhanced the specific surface area of the as-synthesized Ti-doped-CoO@C nanocomposite. Owing to the octahedral carbon matrix and Ti-doping, the nanocomposite exhibits excellent electrical conductivity and abundant accessible active sites. It is worth noting that the carbon matrix sustains the volumetric changes and the homogenous mesoporous structure facilitates rapid mass transport and electron transfer during the charge/discharge process. Therefore, the as-synthesized Ti-doped-CoO@C nanocomposites exhibited excellent charge storage properties as an anode material in Li- and Na-ion batteries. In Li-ion batteries, the as-synthesized Ti-doped-CoO@C nanocomposites delivered a specific capacity of 1108 mAh g(-1) after 150 cycles at a current density of 200 mA g(-1) and total capacitive contribution reached up to 86.6%, at the scan rate of 0.5 mV s(-1). In Na ion batteries, the Ti-doped-CoO@C nanocomposites demonstrated a stable specific capacity of 285 mAh g(-1) after 100 cycles, at a current density of 100 mA g(-1) and total capacitive contribution reached up to 78.4%, at the scan rate of 0.5 mV s(-1). Furthermore, excellent rate performance and efficient charge transfer behavior have been exhibited by the Ti-doped-CoO@C nanocomposites. The present study provides a generic approach to synthesize MOF-derived heteroatom-doped metal-oxide/carbon nanocomposites for a wide range of applications.