Gelation of organic liquid electrolyte to achieve superior sodium-ion full-cells

The irreversible consumption of active sodium in sodium-ion full-cells (SIFCs) becomes particularly serious due to the existence of unavoidable interface or side reaction, which has become the key to restrict the development of high-performance sodium-ion batteries (SIBs). Interface design and electrolyte optimization have been proved to be effective strategies to improve or solve this problem. In this work, on the basis of traditional organic liquid electrolytes, a novel gel polymer electrolyte with high ionic conductivity (1.13 × 10-3 S cm−1) and wide electrochemical stability window (~4.7 V) was designed and synthesized using bacterial cellulose film as precursor. Compared with the liquid electrolyte, the obtained electrolyte can endow better sodium storage performance in both half- and full-cells. When coupled with sodium hexacyanoferrate cathode and hard carbon anode, a capacity of 94.2 mA h g−1 can be obtained with a capacity retention of 75% after 100 cycles at a current density of 100 mA g−1, while those of with conventional liquid electrolyte can deliver a capacity of 99.0 mA h g−1 but only accompany 58% capacity retention under the same conditions. Significantly, when the current density increases to 800 mA g−1, their capacity difference reaches 23.4 mA h g−1.