Electrochemically Induced 2H→1T Interfacial Transformation Improves Charge-Transfer Kinetics in LiFe0.6Mn0.4PO4 Cathodes.
Abstract
Polyanion cathodes such as LiFe1- xMnxPO4 (LFMP) offer structural stability and thermal safety but are often limited by sluggish interfacial charge transfer and progressive Mn-related degradation. Here, we report an electrochemically induced interfacial phase transformation in which a surface 2H-MoSx layer is converted into a MoSx-derived metallic interphase containing 1T-LixMoSx and related lithiated species during initial activation. This transformation is directly observed by in situ transmission electron microscopy and is accompanied by changes in interfacial electronic structure, as indicated by spectroscopic measurements. The modified electrode exhibits improved rate capability and reduced polarization compared to pristine LFMP/C. Systematic pre-discharge experiments show that this improvement correlates with the formation of the metallic interphase rather than pre-discharge-induced surface activation alone. Additional analysis suggests reduced Mn cross-talk and improved interfacial stability. These findings demonstrate that electrochemically induced interfacial phase evolution provides an effective strategy for improving interfacial charge-transfer kinetics in polyanionic cathodes. Together, the combined evidence supports a mechanistic picture in which the electrochemically generated metallic interphase contributes to this kinetic enhancement, although the detailed pathway remains to be further clarified.