Ultrastable Gel Polymer Lithium Metal Batteries With Novel Nitro‐Substituted Hexafluoride SEI‐Forming Additive

ABSTRACT Employing functional additives can facilitate the formation of stable solid electrolyte interphase (SEI), which has emerged as a promising strategy to improve the electrochemical properties of lithium metal batteries (LMBs). Typical SEI containing inorganic components, such as lithium fluoride (LiF) and lithium nitride (LiN x O y and Li 3 N), have been confirmed to construct an ideal SEI for LMBs. Here, we designed and synthesized a novel molecule named BTFN to act as an SEI‐forming additive containing fluorine and nitro groups. The strong electron‐withdrawing effect greatly reduces the lowest unoccupied molecular orbital (LUMO) energy, facilitating its preferential decomposition during the SEI‐forming process. An SEI with rich LiF, LiN x O y , and Li 3 N forms after its preferential and complete decomposition, greatly enhancing stabilization and uniformity. The lifespan of symmetric LMBs with BTFN significantly increases more than 12 times under the same conditions; the Li/SPE/LFP full batteries cycle more than four times the contrast batteries with a capacity retention of 99.7%. This work provides some experiences and opinions for exploring complex SEI‐forming additives.