Synthesis and electrochemical performance of Co2TiO4 and its core–shell structure of Co2TiO4@C as negative electrodes for Li-ion batteries

Abstract

Spinel Co₂TiO₄ is synthesised using a polymeric precursor method and used as an efficient negative electrode for Li-ion batteries. Precise full-profile Rietveld refinement proves the formation of a single-phase cubic spinel structure with a lattice parameter of a = 8.4190(9) Å, which corresponds to the sample composition of Co_2.05Ti_0.95O₄. Subsequently, a carbon coating around Co₂TiO₄ is achieved through a simple hydrothermal method. TGA analysis implies that Co₂TiO₄@C consists of 17 wt% carbon, and the presence of D and G bands was confirmed through Raman analysis. Transmission electron microscopy (TEM) is employed to probe the morphological features, as well as to confirm the carbon coating on Co₂TiO₄. It shows non uniform shape particles with sizes in the range of 400–750 nm and that the thickness of the carbon coating is 10 nm. The superior electrochemical performance of Co₂TiO₄@C is confirmed by a higher initial discharge–charge capacity (1283/418 mA h g⁻¹), high diffusion coefficient (1.76 × 10⁻¹⁰ cm² s^−1/2) and lower R_ct (after 50 cycles). This is attributed to the increased electrical conductivity and the creation of new active sites due to the synergistic effect of the carbon matrix on Co₂TiO₄, thereby making it a promising candidate for lithium ion battery applications.