Ion-Distribution Modulated Solvent-Cage Electrolyte with Gradient SEI for High-Performance Li-Metal Batteries

Lithium metal batteries (LMBs) offer great promise for next-generation energy storage, but substantial challenges remain in carbonate electrolytes: unstable solid electrolyte interphase (SEI) and lithium dendrite growth. Here we propose an ion-distribution modulated solvent-cage electrolyte system that could generate a stable SEI and enable uniform Li deposition. Specifically, MCM-41 molecular sieves as solvent cages immobilize abundant NO3– via hydrogen bonding, enabling LiNO3 dissolution in carbonate electrolytes and sustained NO3– replenishment in the SEI. This dynamic trapping–release mechanism restructures the SEI into a gradient architecture: a Li3N-rich inner layer and a LiF/LixSiOy-rich outer layer. The gradient composition boosts the Li+ conductivity and reinforces the mechanical robustness, ensuring homogeneous Li deposition. Consequently, Li||Cu cells achieve 99.4% Coulombic efficiency, while Li||Li symmetric cells cycle stably at 0.5 mA cm–2 for over 600 h. Full cells with LiNi0.6Co0.2Mn0.2O2 cathodes retain 83.7% capacity after 600 cycles at 0.5 C, demonstrating the viability of this strategy for high-performance LMBs.