Hydroxypropyl methyl cellulose-based gel polymer electrolyte provides a fast migration channel for sodium-ion batteries

Most gel polymer electrolytes (GPEs) for sodium-ion batteries developed at present have some problems, such as limited absorption uptake of liquid electrolyte (LE) and low ionic conductivity of corresponding GPEs caused by the difficulty of transporting sodium ions with large radius. In view of these problems, hydroxypropyl methyl cellulose (HPMC) is used as raw material to prepare high-performance HPMC-based GPE (HPMC-GPE). When HPMC membrane is added to the LE containing NaClO4 and propylene carbonate (PC) will lead to the ring-opening polymerization of PC, and the products of ring-opening polymerization of PC will be grafted into HPMC side chain. This destroys the dense structure of HPMC membrane and enhances the affinity of HPMC membrane to LE, and then, a large amount of LE (up to 1796 wt.%) can be stored in the molecular chain of HPMC. With the thermal movement of HPMC molecular chain, the volume of HPMC molecular increases significantly in 3D space, providing a large free volume and fast migration channel for sodium ions conduction. The experimental results show that the ionic conductivity of HPMC-GPE is 3.3 × 10–3 S cm−1 and has an electrochemical stability window of 4.72 V. SIB assembled with SnS/rGO working electrode, sodium metal counter electrode and HPMC-GPE has good rate performance and cycle stability.