Numerical modelling of transport limitations in lithium titanate anodes

Lithium titanate oxide (Li4Ti5O12, LTO) is receiving significant attention as an alternative to graphitic anode due to high structural and thermal stability, and reduced possibility of formation of SEI film. In this study, Li4Ti5O12 is synthesized by the solid-state method and its electrochemical characteristics are examined by cyclic voltammetry and galvanostatic charge-discharge techniques. Moreover, we demonstrate the first instance of a numerical model used to understand the role of cell parameters in Li-LTO half-cells. The simulated charge-discharge capacity curves at 0.5, 1.0 and 1.5 C currents are in good agreement with experimental findings. Using this model, the effect of particle size, lithium diffusivity and electrode thickness on the charge-discharge capacity of Li-LTO cells have been investigated. Simulations show that the cell capacity is highly dependent on lithium transport in the solid matrix specifically at high current. Critical analysis of lithium concentration inside the solid matrix reveals a poor utilization of lithium storage sites and lower cyclable lithium in case larger particles and lower lithium diffusivity. The rise in the thickness of electrode leads to the lower achievable specific capacity of the battery due to increased cell overpotential and transport limitations for Li-ions and electrons.