Concentration‐Driven Li ⁺ Solvation Engineering with TDMAP‐Based Porphyrin Additives for Dendrite‐Free Li Metal Batteries

ABSTRACT The performance of lithium metal batteries is strongly influenced by Li + solvation and solid electrolyte interphase (SEI), which governs dendrite growth, cycling stability, and Coulombic efficiency. Herein, to modulate Li + solvation structure, the tetrakis(4‐N, N‐dimethylaminophenyl)porphyrin (TDMAP) is introduced as an additive in carbonate‐based electrolyte, further reinforcing SEI stability. Spectroscopical measurements reveal that TDMAP displaces ethylene carbonate (EC) molecules from the first solvation shell, partially forming mixed coordination environments and acting as a ligand that modulates the Li + solvation shell and alters its interaction with PF 6 − anions (Li + –NMe 2 –PF 6 − ). Results show that the electrolyte with optimal 3 mg mL −1 TDMAP (TDMAP‐3) enables and promotes smooth, dense Li deposition and a LiF‐rich and nitrogen‐rich SEI on the condition of the expected Li + solvation structure shell, in contrast to the dendritic and porous Li plating morphology as observed in the base electrolyte. Consequently, the cell with TDMAP‐3 additive reduces the nucleation overpotential from 62 to 20 mV, achieves high Coulombic efficiency (∼99%), and the Li–LiFePO 4 full cell maintains capacity retention of 97.3% over 450 cycles, demonstrating that porphyrin additive effectively regulates Li + solvation and SEI composition for high‐performance Li metal batteries.