Effect of SiO2 microstructure on ionic transport behavior of self-healing composite electrolytes for sodium metal batteries

Batteries matched with flexible intelligent electronic devices are required in the future to supply dense and reliable power security. In addition to energy storage performance, functionalized design of batteries with good mechanical properties and self-healing ability is critical to the development of flexible intelligent electronic devices. The polymer with quadruple hydrogen bonds can give materials the ability to repair mechanical damage and restore the original mechanical properties. The incorporation of inorganic fillers into polymer electrolytes can improve the electrochemical properties and stability of the electrolytes. Optimization of the geometry of inorganic materials could further improve the electrical conductivity of composite electrolytes. In this work, a flexible self-healing polymer electrolyte (Poly (ethylene glycol)-co-ureidopyrimidinone), PEG-UPy) was syn-thesized. Three different microstructures of SiO2 fillers (solid, mesoporous, and hollow mesoporous) with UPy modified were designed to improve the sodium ion transport performance of the PEG-UPy self-healing polymer electrolyte for sodium ion batteries. The PEG-UPy electrolyte filled with hollow mesoporous SiO2 (PEG-UPy@hSiO2) exhibits an excellent electrochemical performance due to its unique structure among the samples. The PEG-UPy@hSiO2 electrolyte shows the highest ionic conductivity, sodium ion transference number, and appropriate self-healing property. The discharge capacity of NVP/PEG-UPy@hSiO2-NaTFSI (HCPE)/Na cell could reach 110.5 mAh g-1 at 0.1C and the capacity retention rate could reach more than 77.6% after 200 cycles at 60 degrees C.