Proton-regulated nitrite release enables anion-derived solid electrolyte interphase for stable lithium metal anodes

Lithium (Li) metal anodes hold exceptional promise for next-generation high-energy-density batteries, yet their practical application is hindered by unstable solid electrolyte interphase (SEI) and uncontrolled dendritic growth. Here, we proposed a proton-regulated nitrite release strategy that dynamically modulates the electrolyte solvation structure to engineer a robust and inorganic-rich SEI. Specifically, highly soluble nitrocellulose is introduced as a nitrite (NO₂⁻) reservoir, which continuously releases NO₂⁻ via proton-mediated dissociation triggered by LiPF₆ hydrolysis. The released NO₂⁻ preferentially coordinates with Li⁺, generating an anion-rich solvation sheath, and subsequently undergoes preferential reduction to form an inorganic-rich SEI enriched with Li₃N and LiN_xO_y. The resulting mechanically robust and ionically conductive interphase ensures homogeneous Li⁺ flux, enabling uniform, dendrite-free Li deposition. Moreover, the sustained NO₂⁻ release facilitates dynamic SEI repair during cycling. Consequently, Li||Li symmetric cells operate stably for over 1000 h. Li||LiNi_0.5Co_0.2Mn_0.3O₂ full cells with high-areal-loading cathodes (3.0 mAh cm⁻²) retain 80% capacity after 150 cycles at 1.0 C. Moreover, a practical 409 Wh kg⁻¹ Li||LiNi_0.83Co_0.12Mn_0.05O₂ pouch cell demonstrates stable operation over 50 cycles. This work establishes a dynamically proton-regulated anion-release paradigm for solvation structure regulation, offering a scalable pathway toward high-performance Li metal batteries.