Conformally Reactive Interphase Enables Excellent Kinetics and Cyclability in Quasi-Solid-State Sodium Metal Battery

The rational design of flexible and robust anode-electrolyte interface is of great significance for extending the cycle life and improving the kinetics performance for sodium metal batteries (SMBs). Herein, a conformally reactive solid-electrolyte interphase (SEI) is constructed through a spontaneous absorption-oligomerization strategy in a quasi-solid-state polymer electrolyte (QSE-T). The polymeric network in the QSE-T system ensures a stable environment with high Na+ transfer number to suppress Na dendrite growth and chemical corrosion. Simultaneously, the reactive SEI is consisted of inorganic NaF and low crosslinked O-B-O and O-B-F segments derived from the 4-trifluoromethylphenylboronic acid (TFPBA) additive, which exhibits lower Na+ diffusion-barriers, and accommodates the ever-changing quasi-solid interface during cycling. Consequently, the NVP||QSE-T||Na cells exhibit ultra-stable cycling performance and high rate capability, with a high initial capacity of 95.1 mAh g-1 at a high rate of 5 C and a capacity retention rate of 86.6% after 12000 cycles.