Nano-Confined Electrolyte for Sustainable Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are considered as a promising candidate for large-scale electrochemical energy storage devices due to their low cost, abundant upstream resources, and compatible manufacturing processes with lithium-ion batteries. However, the highly active free solvent molecules in the liquid electrolyte trigger continuous interfacial side reactions between electrodes and electrolyte, which degrades the cycling performance of SIBs. Herein, a Cu-based metal-organic framework (MOF) with a uniform nanoporous channel of 1.1 nm is exploited to confine the electrolyte. Benefiting from the highly-aggregated solvation configuration, the MOF-confined electrolyte possesses superior chemical/electrochemical and thermal stability, which guarantees its interface compatibility and flame retardancy. As a result, the batteries with the nano-confined electrolyte and Na 3 V 2 (PO 4 ) 3 cathode show an ultra-long lifetime of 3000 cycles with 93% capacity retention and decent high-temperature performance (600 cycles with 90% capacity retention). This work presents a viable method for fabricating sustainable SIBs and also provides guidance for solving the side reactions between electrolytes and electrodes in electrochemical energy storage systems.