Defect-modulated olivine cathodes: Overcoming history-dependent kinetics via multi-dimensional percolation

초록

High-rate lithium-ion batteries are fundamentally limited by one-dimensional lithium transport and blocking antisite defects in olivine cathodes. This slow kinetic response prominently manifests under non-equilibrium conditions as the electrochemical memory effect—a voltage anomaly caused by constrained lithium redistribution during partial cycling. Here, we demonstrate that this history-dependent behavior is a consequence of defect-mediated transport limitations, which can be effectively overcome via defect-modulating compositional tuning. We report that introducing Mn to form LiFe0.5Mn0.5PO4 (LFMP) activates a multi-dimensional percolation network and promotes a thermodynamically favored solid-solution pathway, completely suppressing the memory effect. Structural analysis reveals that Mn incorporation increases the thermodynamic barrier for Li/Fe antisite defect formation and selectively stabilizes the α-phase, eliminating canonical one-dimensional diffusion constraints. Crucially, operando X-ray diffraction and impedance analysis confirm this structurally unblocked network is a prerequisite for a highly reversible solid-solution reaction, effectively eliminating the kinetic bifurcation responsible for particle bipolarization. Consequently, LFMP operates via a kinetically coherent mechanism insensitive to prior cycling history. These findings bridge lattice defect chemistry, reaction thermodynamics, and mesoscale relaxation, offering a strategic pathway for kinetically unimpeded, high-rate cathodes. © 2026 Elsevier B.V.

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