Mn vacancies in Mn3O4: steering lithiation kinetics during solid-state synthesis toward ultrastable spinel cathode materials

Abstract

The lithiation process during solid-state synthesis governs lattice formation, defect evolution and, ultimately, the electrochemical performance of lithium-ion battery cathodes. However, how the competition between lithiation and oxidation during precursor conversion dictates the formation of the final crystal lattice remains poorly understood. Here we reveal the decisive role of competitive lithiation in regulating lattice formation and defect evolution during the conversion of a commercially relevant Mn3O4 precursor into spinel LiMn2O4 (LMO), and establish the underlying thermodynamic and kinetic mechanisms. We show that an Mn3O4 precursor containing intrinsic Mn defects exhibits a lower lithiation formation energy, enabling rapid and homogeneous early-stage lithiation that suppresses the formation of the Mn2O3 intermediate and eliminates competitive lithiation. This pathway promotes the direct reconstruction of the Mn–O framework, yielding LMO with higher lattice integrity, a lower oxygen-vacancy concentration and a more stable Mn–O coordination environment. Consequently, the material delivers an initial discharge capacity of 135.19 mAh g−1 at 5C and retains 90.13% of its capacity after 500 cycles. Rather than relying on conventional post-synthesis optimization strategies such as elemental doping or surface modification, this work establishes a precursor-regulated lithiation strategy that provides new mechanistic insights and general design principles for the controllable synthesis of Mn3O4-derived manganese-based cathode materials.