Tailoring Li ₃ N‐Contained Complementary Gradient Solid Electrolyte Interphase in High‐Performance 3.2 V Aqueous Lithium‐Ion Batteries

Lithium nitride (Li₃N) as a crucial solid electrolyte interphase (SEI) component to realize high-voltage non-aqueous lithium batteries is rarely reported in aqueous lithium-ion batteries (ALIBs) due to its intense hydrolysis in aqueous solution. To overcome the limited operating voltages (< 3 V) and the unstable electrode/electrolyte interphase in ALIBs, a two-pronged strategy is presented that includes employing asymmetric amide co-solvent and overpotential-driven interfacial engineering. This simple method enables the construction of Li₃N-contained complementary gradient SEI in aqueous media unprecedentedly. By adopting the N-methylformamide (NMF) co-solvent and an appropriate overpotential (0.3 V), a robust complementary gradient SEI composed of LiF (outer) and stable Li₃N (inner) via internal self-protection is established. The potential three-step formation mechanism of LiF/Li₃N complementary gradient SEI involving the sequential decomposition of TFSI^-, NMF, and H₂O is proposed. Consequently, the tailored complementary gradient structure synergistically combines chemical stability with rapid formation dynamics, inhibiting the hydrogen evolution reaction in high-voltage situations. Ultimately, LiMn₂O₄||Li₄Ti₅O₁₂ cells demonstrate excellent cycling stability over 700 and 2000 cycles under 2 and 5C (3.2 V), respectively. This work establishes a span-new idea for stabilizing the Li₃N-contained electrode/electrolyte interphase in aqueous batteries, and offers a distinctive pathway for advancing high-voltage, long-term ALIBs.