Weakly Solvating Molecule‐Enabled Localized High‐Concentration Electrolytes for Ultralow Temperature Batteries with High‐Nickel Cathode/Lithium‐Metal Anode

Abstract The ultralow temperature performance of lithium metal batteries (LMBs) is fundamentally limited by sluggish ion transport and interfacial instability in conventional electrolytes. To address this challenge, this work proposes a novel localized high‐concentration electrolyte (LHCE) system, which synergistically regulates solvation structures and interfacial chemistry to achieve efficient ion transport and stable electrode/electrolyte interfaces at low temperature. By leveraging weakly solvating solvents 1,2‐diethoxyethane/methyl acetate, the solvation sheath structure is altered in the LHCE, allowing more anions to enter, significantly reducing Li ⁺ de‐solvation activation energy and interfacial resistance. Experimental and simulation results reveal that weakly solvating molecule‐driven anion‐dominated solvation facilitates the formation of inorganic‐rich interphases (LiF/Li ₃ N), effectively suppressing lithium dendrite growth and cathode interface degradation. Therefore, the Li||Cu cell with the designed electrolyte exhibits high lithium plating/stripping coulombic efficiency at −20 °C (>98.8%). Under harsh conditions (4.5 V cutoff, −40 °C), the Li||NCM622 cell maintains 73.4% of the discharge capacity at room temperature and retains 88% of the initial capacity after 400 cycles. This study establishes a novel molecular engineering strategy for electrolyte design, leveraging solvation regulation and targeted interfacial chemistry to unlock high‐performance LMBs.