Interfacial Molecular Repulsion Engineering for Durable 5 V-Class Cobalt-Free Lithium-Ion Batteries

Abstract

The cobalt-free LiNi0.5Mn1.5O4 (LNMO) cathode exhibits severe interfacial instability when employed with carbonate-based electrolytes. Here, we introduce methyl(3,3,3-trifluoropropyl)diethoxysilane (MFS) as a nonsacrificial additive that creates a molecular “repulsion layer” on LNMO. MFS preferentially adsorbs onto transition-metal sites, stabilizing the inner Helmholtz plane, suppressing solvent decomposition and HF attack, and forming a thin, mechanically robust cathode–electrolyte interphase. This unique interface design maintains fast Li+ transport while blocking parasitic reactions and transition-metal dissolution. With only 0.2 wt % MFS, Gr||LNMO full cells deliver 92% capacity retention after 450 cycles at 4.8 V under room temperature and 73% after 300 cycles at 45 °C. The potential practicality and universality of this strategy are demonstrated in 1.5 Ah Gr||LNMO pouch cells, as well as in cells incorporating lithium-rich layered oxide cathodes. This work establishes a molecular-level paradigm for advancing the development of cobalt-free battery chemistries.