Enhanced Fast‐Charging Performance of High‐Mass‐Loading Mn‐Rich Li[Mn <sub>1‐</sub> <i> <sub>x</sub> </i> Fe <i> <sub>x</sub> </i> ]PO <sub>4</sub> Cathodes via LiF‐Less Cathode–Electrolyte Interphase
Bonyoung Ku, Lahyeon Jang, Hyunji Kweon, Jinho Ahn, Sun-Young Hwang, Jihoe Lee, Myungeun Choi, Sunyoung Yoo, Kwangho Yoo, Kyu‐young Park, Jongsoon Kim
Abstract
ABSTRACT Mn‐rich Li[Mn 1‐ x Fe x ]PO 4 (LMFP) cathodes are promising candidates for next‐generation lithium‐ion batteries due to their structural stability and cost‐effectiveness. However, under industrially relevant high‐mass‐loading conditions, they still suffer from severe performance degradation, particularly during fast charging. In this study, we systematically demonstrate that charge‐transfer resistance, rather than bulk Li + diffusivity, governs the kinetic limitations of LMFP electrodes with an areal capacity of ∼3.5 mAh cm −2 (∼23 mg cm −2 mass loading). Surface analyses reveal that the buildup of electronically and ionically insulating LiF at the cathode–electrolyte interphase (CEI) is the primary cause of sluggish charge transfer, highlighting a previously overlooked detrimental role of LiF. Guided by this insight, we implement an interfacial engineering strategy that suppresses LiF formation at the CEI. Remarkably, the resulting high‐mass‐loading LMFP cathodes deliver a 1.6‐fold increase in capacity at 5C and retain ∼87% of their initial capacity after 100 cycles at 2C. Moreover, operando structural analysis reveals that electrodes with LiF‐suppressed CEI maintain a robust single‐phase transition during fast cycling, directly linking interfacial LiF suppression to significantly enhanced charge‐transfer kinetics. This work highlights the critical importance of CEI engineering in enabling fast‐charging Mn‐rich olivine cathodes under practical, high‐mass‐loading conditions.