Regulation of interfacial stability and lithium-ion transport in LiMn0.6Fe0.4PO4 cathodes via a boroxine-based electrolyte additive

Abstract

LiMn_0.6Fe_0.4PO₄ (LMFP64) is a promising candidate for cathode materials of lithium-ion batteries; however, its high working potential and low Li⁺ diffusivity limit its stable cycling behavior. In this study, 2,4,6-tris(3,4,5-trifluorophenyl)boroxine (TTFB), which is a boron- and fluorine-functionalized molecule, is added to the electrolyte to efficiently create an ion-permeable cathode–electrolyte interphase (CEI) at the surface of LMFP64, thereby enhancing the overall electrochemical performance. The oxidation of TTFB yields B–O- and Li–F-functionalized CEI layers at the LMFP64–electrolyte interface, which not only suppresses undesired reactions during cycling but also exhibits low-temperature compatibility even at −10 °C. Consequently, the capacity retention of the cells containing TTFB increases to 96.4%, whereas those without TTFB retain only 85.2%. Additional systematic analyses, including SEM, TEM, EIS, XPS, and TOF-SIMS, indicate that TTFB dramatically changes the interfacial state of LMFP64, thereby stabilizing the cycling behavior even after 150 cycles.