Removing the Two-Phase Region in Spinel LiMn₂O₄ Towards High-Rate, High-Energy Density Partially Disordered Spinels

Resource constraints have become critical for the Li-ion industry. Spinel LiMn 2 O 4 presents a cheaper, more sustainable alternative to traditional layered Li-ion cathodes, but its capacity is constrained by a two-phase transition at ~3V associated with a large, inhomogeneous volume change that leads to particle cracking and poor cycling stability. In contrast, the partially disordered spinels (PDS) have more sloping, solid-solution-like behavior, resulting in better rate capability and more homogeneous volume change. In this talk, we demonstrate that PDS achieves this by introducing cation disorder, which can shrink, and even fully remove, the two-phase region. By analyzing samples from cluster expansion-based Monte Carlo simulations, we identify the mechanisms that increase Li solubility in the LiMn 2 O 4 phase and lead to this shortened ~3V plateau. These results provide guidance on the optimal level of disorder in spinels to achieve both solid-solution behavior and good Li mobility and also highlight more generally how disorder can be utilized to reduce the effects of problematic phase transformations in ordered frameworks.