Enhanced fast charge–discharge performance of Li4Ti5O12 as anode materials for lithium-ion batteries by Ce and CeO2 modification using a facile method

Abstract

A facile solid-state method to improve the fast charge–discharge and kinetic performance of Li₄Ti₅O₁₂ in lithium-ion batteries by Ce and CeO₂ in situ modification is presented in this work. XRD shows that the Ce doping and CeO₂ modification do not change the spinel structure of Li₄Ti₅O₁₂. Little Ce doping (Ti/Ce = 4.9 : 0.1 and Ti/Ce = 4.85 : 0.15) reduces the lattice parameter of doped Li₄Ti₅O₁₂, but more Ce⁴⁺ doping (Ti/Ce = 4.8 : 0.2) increases the lattice parameter due to the large ionic radius of Ce⁴⁺. Raman spectra reveal that CeO₂ is not completely incorporated into the host structure and leads to the formation of a uniform coating on the surface of Li₄Ti₅O₁₂. The doping of Ce⁴⁺ and the combination with in situ generated CeO₂ in Li₄Ti₅O₁₂ are favorable for reducing the electrode polarization and charge-transfer resistance and improve the lithium insertion/extraction kinetics of Li₄Ti₅O₁₂, resulting in its relatively higher capacity at a high charge–discharge rate. The Ce-doped Li₄Ti₅O₁₂–CeO₂ composites show a much improved rate capability and cycling stability compared with pristine Li₄Ti₅O₁₂ at a 10 C charge–discharge rate in a broad voltage window (0–2.5 V). The introduction of Ce and CeO₂ enhances not only the electric conductivity of Li₄Ti₅O₁₂, but also the lithium ion diffusivity in Li₄Ti₅O₁₂, resulting in a significantly improved high-rate capability, cycling stability, and fast charge–discharge performance of Li₄Ti₅O₁₂.