Silica-centered crosslinking solid polymer electrolyte for sodium metal batteries

Replacing flammable liquid electrolytes with solid polymer electrolytes (SPEs) can dramatically improve battery safety. Here, we report the development of silica (SiO 2 )-centered crosslinking SPEs by chemically bonding SiO 2 nanoparticles with the polymer matrix. This innovative design not only ensures the uniform dispersion of SiO 2 nanoparticles throughout the polymer matrix but also builds a robust interface between the nanofillers and the polymer matrix, thereby enhancing Na + ionic conductivity. Simultaneously, it leverages the abundant hydroxyl (OH) groups on SiO 2 nanoparticles to interact with ClO 4 − anions through Lewis acid-base interactions and hydrogen bonding, promoting sodium salt dissociation. Theoretical calculations corroborate these interfacial mechanisms, revealing a 5.6-fold improvement in the Na + diffusion coefficient. As a result, this pioneering design allows SPE to achieve a high Na + ionic conductivity of 7.03 × 10 −4 S cm −1 and an extended electrochemical voltage window up to 5.21 V. The assembled solid-state sodium metal batteries (with Na 3 V 2 (PO 4 ) 3 as the cathode) exhibit dendrite-free Na-metal deposition, promising rate capability, and stable cycling performance with 84.6 % capacity retention over 200 cycles at 0.2C and 64.1 % capacity retention over 200 cycles at 1C. This work introduces a transformative strategy of engineering nanofiller–polymer interactions to enhance the properties of SPEs for solid-state batteries. • Silica (SiO 2 )-centered crosslinking SPEs by chemically bonding SiO 2 nanoparticles with the polymer matrix were designed. • The innovative design builds a robust interface between the nanofillers and the polymer matrix, thereby enhancing Na + conductivity. • Theoretical calculations corroborate these interfacial mechanisms, revealing a 5.6-fold improvement in the Na + diffusion coefficient. • The Na 3 V 2 (PO 4 ) 3 //Na cells exhibit promising rate capability and stable cycling performance over 200 cycles without obvious sodium dendrites.