Computational modelling studies on discharge of nanoporous LiMn2O4*

The performance of Li-ion batteries can be affected by porosity. In our study molecular dynamics based simulated amorphisation recrystallisation methods [1], were employed to produce nanoporous LixMn2O4 spinels of approximately 25000 atoms, with different pore sizes. The resulting structures were discharged by lithiation in the concentration range x=1 to 2, and were characterised from XRDs, microstructures and mechanical properties. Generally a transition from the cubic to tetragonal spinel phase was observed in the concentration range of x=1.5 to 2. In particular, at x=1.75 a broadening of XRD peaks, multiple grain boundries and a reduction in the yield stress were noted. A pore size that minimises such effects was identified together with associated heterostructures. The thermal stability of such structure was tested by heating it from low to high temperature by molecular dynamics simulations.

[1] Sayle T,X,T, Kgatwane K, Ngoepe P.E, and Sayle D.C., J. Mater. Chem. A, 4, 6465 (2016)