Analysing phase change of LiTi₂(PO₄)₃ solid electrolyte material due to temperature variation

Materials Modelling Centre, University of Limpopo, Private Bag x1106, Sovenga, 0727, South Africa

^* Corresponding author: 201803235@keyaka.ul.ac.za

Abstract

The NASICON-type lithium titanium phosphate (LTP) solid electrolyte is the most promising solid-state electrolyte because of its wide chemical window and excellent chemical stability. Despite its potential, the electronic conductivity of LTP remains too low for practical use; this hampers its commercialisation and further advancement of solid electrolyte technologies. As such, enhancing their electronic conductivity to improve stability and safety during cycling is imperative. In this study, molecular dynamics simulations under the NVE, NVT, NPT, and NST statistical ensembles, were performed using the DL_POLY code to investigate the thermodynamic and structural properties of the LiTi₂(PO₄)₃ structure. Temperature variation calculations on the simulated LiTi₂(PO₄)₃ structure revealed that the total energy increases with the increasing temperature under various ensembles. A transition from crystalline to amorphous state was observed between 2500 K and 2800 K under the NST ensemble. This transition corresponds with reported amorphous temperatures from the literature. The radial distribution functions of the simulated LiTi₂(PO₄)₃ structure under the NST ensembles exhibit substantial peak broadening after 2500 K, which further confirms the successful amorphisation of the structure. These findings indicate that the NST is the most suitable ensemble to carry out atomistic simulation investigations for the LiTi₂(PO₄)₃ structure at the nanoscale.