Regulating Polymer Demixing Dynamics to Construct a Low‐Tortuosity Host for Stable High‐Energy‐Density Lithium Metal Batteries

Lithium (Li) metal anodes, despite their exceptional theoretical capacity (3860 mAh g^-1), suffer from severe dendrite growth, electrolyte decomposition, and structural instability caused by uneven Li-ion flux and significant volume fluctuations. Here, a one-step, scalable fabrication of 3D hosts that synergistically couple tortuosity modulation with a spatially graded lithiophilicity via precise control of demixing kinetics in a nonsolvent-induced phase separation process is reported. Low-tortuosity (LT) hosts integrate vertically aligned channels for fast ion transport with a silver-gradient interface that directs bottom-up Li deposition, enabling concurrent suppression of dendrites and accommodation of plating-induced volume expansion (4.4% swelling). Finite element simulations confirm the cooperative role of structural alignment in mitigating ion depletion and of chemical gradients in guiding uniform deposition, jointly ensuring stable Li cycling. The LT host sustains >5500 h at 1C in symmetric cells and delivers superior durability in full cells with limited-Li anodes (4 mAh cm^-2) paired with LiFePO₄ and high-loading LiNi_0.8Co_0.1Mn_0.1O₂ cathodes. Double-stacked pouch cells (N/P = 0.8, E/C = 2.5 g Ah^-1) achieve 398.1 Wh kg^-1 and 1516.8 Wh L^-1, retaining 94.2% capacity after 80 cycles. This structural-chemical integration strategy offers a practical, scalable route toward next-generation high-energy-density Li metal batteries.