Surface Chemical Coordination Stabilizes Ni-Rich Cathodes for High-Energy Li-Metal Batteries

The stability of the electrode-electrolyte interface is a critical factor influencing the electrochemical performance of Li-metal batteries. However, on the delithiated Ni-rich cathode surface, the strong catalytic effects of transition metals with coordination deficiency significantly aggravate the parasitic reactions with Li-metal-compatible ether-based electrolytes, thereby reducing the cycling stability of high-voltage Ni-rich batteries. Here, we propose an sp2-induction mechanism to address coordination deficiency through the coupling of interfacial orbitals between molecules and the cathode surface. Sp2-hybrid high-fluorinated olefins, characterized by unsaturated bonds, exhibit highly delocalized electronic properties (electron delocalization index >0.95 au) and elevated anodic stability (ionization potential >10 eV). These characters ensure robust and stable interactions with the Ni-rich cathode, facilitating the formation of induced orbitals. These low-energy orbitals accommodate Ni 3d electrons, effectively mitigating the interfacial coordination deficiency and inhibiting surface side reactions. Among the sp2-hybrid high-fluorinated olefins, (perfluorobutyl)ethylene (PFBE) is identified as an optimal inducing molecule due to its strongest interaction and excellent coordination complementarity on the cathode surface. The PFBE-based electrolyte significantly alleviates the degradation of cathode surface structure and demonstrates remarkable cyclic stability, achieving 80% capacity retention over 320 cycles for a 4.4 V Li||LiNi0.8Mn0.1Co0.1O2 (30 μm Li, high load 3.7 mAh cm-2 NMC811) full cell, compared to 175 cycles with a PFBE-absent electrolyte. This work elucidates the sp2-induction mechanism for passivating the high-catalytic cathode interface, paving the way for durable, high-energy aggressive Li-metal batteries.