Modification of Nitrate Ion Enables Stable Solid Electrolyte Interphase in Lithium Metal Batteries

The lifespan of high-energy-density lithium metal batteries (LMBs) is hindered by heterogeneous solid electrolyte interphase (SEI). The rational design of electrolytes is strongly considered to obtain uniform SEI in working batteries. Herein, a modification of nitrate ion (NO₃⁻) is proposed and validated to improve the homogeneity of the SEI in practical LMBs. NO₃⁻ is connected to an ether-based moiety to form isosorbide dinitrate (ISDN) to break the resonance structure of NO₃⁻ and improve the reducibility. The decomposition of non-resonant −NO₃ in ISDN enriches SEI with abundant LiN_xO_y and induces uniform lithium deposition. Lithium–sulfur batteries with ISDN additives deliver a capacity retention of 83.7 % for 100 cycles compared with rapid decay with LiNO₃ after 55 cycles. Moreover, lithium–sulfur pouch cells with ISDN additives provide a specific energy of 319 Wh kg⁻¹ and undergo 20 cycles. This work provides a realistic reference in designing additives to modify the SEI for stabilizing LMBs.