Structural and thermodynamic stability of Li4Ti5O12 anode material for lithium-ion battery

The structural and thermal stability are essential to understand the safety of Li-4-Ti5O12, but it is not fully understood. Here, the structural and thermal stability were investigated by the density functional theory (DFT) plane-wave pseudopotential technique and experimental method. Sub-micro Li-4-Ti5O12 particles were synthesized by a solid-state reaction. The calculated results of lattice parameters are highly coincident with the experimental values. XRD and Raman spectra demonstrate the formation of pure phase Li-4-Ti5O12. There is an amorphous phase and no phase transition when discharged to DV, which confirms that there is a certain reversible intercalation processes cycled below 1 V instead of a reduction decomposition reaction. SEM shows that Li-4-Ti5O12 powder has a uniform, nearly cubic structural morphology with a narrow size distribution of about 500 nm. The low formation enthalpy (-6061.45 +/- 4) indicates that Li-4-Ti5O12 has a high thermodynamic stability. The superior cycling performance at high rates cycled between 0 and 2.5 shows that Li-4-Ti5O12 has a very high structural stability. The high thermodynamic stability of Li-4-Ti5O12 is related to the strong covalent bonding characteristic between Ti and O according to the electron density difference diagram. DSC reveals that PF5 is the main species which damages the SEI layer. (C) 2012 Elsevier B.V. All rights reserved.