Storage and release of NO3- and I- via layered double hydroxide in carbonate electrolyte for stable lithium metal battery.

The formation of inactive lithium (Li) in Li metal battery (LMB) primarily originates from the undesirable components of solid electrolyte interphase (SEI) and the growth of dendritic Li. LiNO₃ has emerged as a promising electrolyte additive for mitigating interfacial instability and Li dendrite propagation through the in situ construction of nitride-rich SEI. However, the limited solubility of LiNO₃ in carbonate electrolytes hinders its practical utilization. Herein, the bifunctional I^--MgAl layered double hydroxide (LDH) is proposed to synergistically dissolve LiNO₃ and rejuvenate inactive Li. The anion-exchange capability of LDH facilitates the substitution of native I^- with NO₃^-, forming NO₃^--MgAl LDH and simultaneously generating I₃^-/I^- redox mediators in electrolyte. This substitution not only achieves the dissolution of LiNO₃, serving as a sustainable nitrogen source to optimize SEI components, but also enables the extracted I₃^-/I^- redox couple to react spontaneously with inactive Li, remarkably enhancing the coulombic efficiency. Consequently, the engineered electrolyte significantly extends the lifespan of Li||LiFePO₄, Li||NCM, and Li@Cu||LiFePO₄ cells. The unique architecture of LDH can precisely control the storage and release of NO₃^- and I^-, offering a transformative electrolyte design framework for next-generation batteries by integrating two-dimensional material properties with electrochemical mechanisms.