Molecularly engineered membrane-driven interphase stabilization of electrodes for Li||NCM811 cells under practical operating conditions

Abstract

Achieving durable, high-energy-density lithium metal batteries (LMBs) remains a major challenge under practical conditions such as elevated temperatures, lean electrolyte content, and low negative-to-positive capacity ratios. Here, we report a molecularly functionalized separator incorporating polar fluorine and oxygen groups that concurrently stabilize lithium metal anodes and Ni-rich cathodes by spatially modulating the interfacial reactions. This functional membrane facilitates uniform lithium fluoride formation at the anode and suppresses hydrofluoric acid generation at the cathode, thereby mitigating dendritic growth, structural degradation, and chemical crosstalk. Advanced synchrotron-based nano-computed tomography and scanning transmission electron microscopy reveal that the separator markedly suppresses intergranular cracking and layered-to-rock-salt phase transitions in Ni-rich cathodes, while density functional theory calculations elucidate the molecular-level mechanisms of LiF promotion and PF5 stabilization. Full cells using conventional carbonate-based electrolytes, high-loading cathodes (5.3 mAh cm-2) and thin lithium anodes (40 mu m) demonstrate 80% capacity retention after 208 cycles at 55 degrees C. Notably, a pouch-type bi-cell operating under a stringent low N/P ratio and lean electrolyte achieved exceptional energy densities of 385.1 Wh kgcell-1 and 1135.6 Wh Lcell-1, including the packaging materials. These findings highlight a scalable, material-based strategy for overcoming interfacial instability, offering a promising route toward the practical deployment of next-generation LMBs.