Zwitterionic Thermoplastic Polyurethane‐Based Quasi‐Solid Polymer Electrolytes for Lithium Metal Batteries With Machine‐Learning‐Assisted Mechanistic Insights

ABSTRACT This study presents a quasi‐solid‐state electrolyte based on zwitterionic thermoplastic polyurethane (QS‐Z‐TPU) for lithium metal batteries. Unlike conventional quasi‐solid polymer electrolytes that mainly serve as passive liquid‐electrolyte reservoirs, QS‐Z‐TPU is designed as an active ion‐regulating matrix via phosphorylcholine‐derived zwitterionic groups in the TPU framework. The resulting electrolyte combines the elasticity and film‐forming capability of TPU with dual‐site ion regulation, where phosphate sites coordinate Li + while quaternary ammonium and urethane N‐H groups immobilize TFSI − anions. This design enhances electrolyte affinity while suppressing destructive swelling due to ionic crosslinking. QS‐Z‐TPU exhibits high ionic conductivity, a wide electrochemical stability window, and an enhanced Li + transference number. Machine‐learning‐assisted molecular modeling further reveals that the zwitterionic oligomer stabilizes separated LiTFSI configurations through cooperative Li + coordination and TFSI − association, substantially reducing the energetic penalty for ion‐pair separation. This regulated ion environment promotes uniform Li + flux at the lithium metal interface and facilitates the formation of a stable inorganic‐rich solid electrolyte interphase. Consequently, QS‐Z‐TPU enables stable Li plating/stripping and improves the cycling stability and rate capability of LFP|Li full cells, further validated in flexible pouch‐cell demonstrations. These findings highlight zwitterionic molecular engineering as an effective strategy for interface‐stabilizing quasi‐solid electrolytes.