Boosting Selective Na+ Migration Kinetics in Structuring Composite Polymer Electrolyte Realizes Ultrastable All-Solid-State Sodium Batteries

Composite polymer electrolytes demonstrate the predictable potential for achieving high-performance all-solid-state sodium metal batteries (ASSMBs). However, the insufficient ionic conductivity resulting from the sluggish Na+ transport kinetics and the inferior interfacial stability caused by simultaneous Na+ and anion transport have hindered practical applications. Herein, a rational structural design strategy is proposed to construct an anion-trapping boron-contained covalent organic framework (B-COF) network in the polymer matrix to facilitate selective Na+ migration and interfacial compatibility for ASSMBs. The abundant Lewis-acid sites on the B-COF network can promote the dissociation of sodium salt and simultaneously constrain the migration of TFSI- anions through the strong anion-capturing effect. Moreover, the well-defined ion-conducting channel formed by the in situ generation of intimately packed B-COF combined with the above synergistic effects can afford continuous and accessible pathways for selectively rapid Na+ transport, which significantly elevates the ionic conductivity and Na+ transference number, respectively. Surprisingly, the Na plating/stripping with small polarization is retained under 0.1 mA cm(-2) for more than 365 d (>8800 h), representing a record-high cycling stability for ASSMBs. As proof of applied studies, the ASSMBs exhibit a high capacity retention (approximate to 81.2%) after 1200 cycles at 1 C, signifying promising application in all-solid-state electrochemical energy storage systems.