A Natural Clay LiNO₃ Solubilizer for Stabilizing Lithium Metal Batteries

The practical deployment of lithium-metal batteries (LMBs) with Ni-rich cathodes is limited by unstable electrode-electrolyte interfaces. Although LiNO₃ is widely recognized as an effective additive for stabilizing these interfaces, its extremely low solubility in carbonate electrolytes (∼0.01 mg mL^-1) severely limits practical use. Here, we introduce dehydrated sepiolite as a structurally simple, cost-effective, and multifunctional LiNO₃ solubilizer for constructing robust electrode-electrolyte interfaces. Sepiolite, with its abundant polar oxygen sites and unique open nanochannels, weakens Li⁺-NO₃^- interactions, thereby increasing LiNO₃ solubility to 13.0 mg mL^-1 (over 1000-fold), while simultaneously scavenging H₂O, HF, and transition-metal ions to mitigate parasitic reactions. These synergistic effects regulate interfacial chemistry and promote the formation of a Li₃N-Li₂O-LiF-rich interphase with high ionic conductivity, stabilizing the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode and enabling uniform lithium deposition. As a result, carbonate electrolytes incorporating the sepiolite-LiNO₃ solubilizer (BE-Sep@NO₃^-) deliver a Coulombic efficiency of 99.0% in Li//Cu cells and stable cycling over 1200 h in Li//Li symmetric cells. Moreover, Li//NCM811 full cells retain 84.6% and 79.5% of their capacity at 0.5 C and 5 C after 400 cycles, respectively, while pouch cells with 50 μm lithium anodes achieve 82.5% capacity retention after 120 cycles with a high energy density of 375.1 Whkg^-1. This work demonstrates that natural dehydrated sepiolite offers an environmentally friendly and scalable pathway to unlock the full potential of LiNO₃ for enabling stable, high-energy LMBs.