Removing the Two-Phase Transition in Spinel LiMn2O4 through Cation Disorder

Resource constraints have become critical for the Li-ion industry. Spinel LiMn2O4 presents a cheaper, more sustainable alternative to traditional layered Li-ion cathodes, but its capacity is constrained by a two-phase transition at 3 V associated with large, inhomogeneous volume change leading to capacity loss. In this Letter, we argue that disorder can replace the two-phase region with solid-solution behavior to create high-capacity cathodes. By investigating the voltage curve and lithiation pathway of LiMn2O4 spinel with varying levels of Mn disorder, we find that disorder shortens the 3 V plateau by raising the energy landscape and stabilizing motifs found in solid-solution configurations. The plateau disappears completely with 25% Mn 16c occupancy. 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.

Automated summary

Resource constraints have become critical for the Li-ion industry. Spinel LiMn2O4 is proposed as a cheaper and more sustainable alternative to traditional cathodes, but it faces capacity loss due to a two-phase transition. This study demonstrates that introducing disorder can replace the two-phase region with solid-solution behavior, leading to high-capacity cathodes. The results provide guidance on the optimal level of disorder in spinels to achieve solid-solution behavior and good Li mobility, and suggest the potential of utilizing disorder to mitigate problematic phase transformations.