Cellulose Derivative and Polyionic Liquid Crosslinked Network Gel Electrolytes for Sodium Metal Quasi‐Solid‐State Batteries

Abstract Sodium metal batteries have gained attention as a potential solution to the low energy densities presented by current sodium‐ion batteries. However, the commonly available electrolyte systems usually fall short in safety performance. Gel polymer electrolytes, closely resembling liquid electrolytes, offer a promising balance of performance and developmental potential. A proposed polymer plastic‐crystal ionic gel composite electrolyte, featuring a polycation auxiliary chain, innovatively copolymerizes ionic liquid cations with electrolyte additives. These auxiliary chains crosslink with the main chain, attracting anions from the ionic liquid and sodium salts. Both experimental evidence and theoretical calculations affirm that this electrolyte exhibits high cation transference numbers and significant mean square displacement radii. By facilitating uniform sodium ion migration, the electrolyte has powered sodium symmetrical cells for over 550 h and has supported stable cycling of Na 3 V 2 (PO 4 ) 3 (NVP)‐sodium metal batteries at a 1 C rate for more than 800 cycles. These achievements underscore its potential in advancing the development of condensed‐state sodium metal batteries.