Stable lithium metal anode enabled by a robust artificial fluorinated hybrid interphase

One of the key challenges for achieving stable lithium (Li) metal anode is the construction of the rational solid electrolyte interphase (SEI), but its realization still faces enormous challenges. In this work, a robust artificial fluorinated hybrid interphase consisting of lithium-bismuth (Li₃Bi) alloy and lithium-fluoride (LiF) was designed to regulate Li deposition without Li dendrite growth. The obtained hybrid interphase showed the high Li⁺ diffusion rate (3.5 × 10⁻⁴ S cm⁻¹), high electron resistivity (9.04 × 10⁴ Ω cm), and high mechanical strength (1348 MPa), thus enabling the uniform Li deposition at the Li/SEI interface. Specifically, Li₃Bi alloy, as a superionic conductor, accelerated the Li⁺ transport and stabilized the hybrid interphase. Meanwhile, LiF was identified as a superior electron-blocker to inhibit the electron tunneling from the Li anode into the SEI. As a result, the modified Li anode showed the stable Li plating/stripping behaviors over 1000 cycles even at 20 mA cm⁻². Moreover, it also enabled the Li (50 μm)‖LiNi_0.8Co_0.1Mn_0.1O₂ (4.4 mA h cm⁻²) full cell to achieve an average Coulombic efficiency (CE) of 99.6% and a high-capacity retention of 79.2% after 100 cycles, whereas the bare Li anode only exhibited a low-capacity retention of 8.0%. This work sheds light on the internal mechanism of Li⁺ transport within the hybrid interface and provides an effective approach to stabilize the interface of Li metal anode.