Understanding the Accelerated Sodium-Ion-Transport Mechanism of an Interfacial Modified Polyacrylonitrile Separator

Sodium-ion batteries (SIBs) are considered as the mostattractive candidates for large-scale energy storage systems owing to theirlow cost and abundant reserves. They need a special separator with rapid Na+transport for a satisfactory power performance. Herein, an alkaline-solution-treated electrospun polyacrylonitrile separator with an in situ chemical-graftedgraphene oxide (denoted as M-PAN-GO) is prepared via regulating theinterfacial group. The increased amount and variety of oxygen-containing polargroups-COO-,-COOH-, and-OH in the M-PAN-GO separator not onlyincrease the number of active sites for bonding and transferring Na+but alsoproduce more H-bonds that impede the migration of PF6-. The obtained M-PAN-GO separator displayed accelerated transmission of Na+and Li+, and theNa+transference number is larger than that of Li+owing to a more efficientbinding that can be formed between oxygen-containing functional groups andNa+. DFT calculations demonstrate that a greater binding energy is favorable tobinding and promoting ion transport in a certain range. Along with the M-PAN-GO separator's desolvation capability, high Na+transference number (0.70) and ion conductivity (4.53 mS cm-1) of the M-PAN-GO separator in 1 M NaPF6EC DMC electrolyteare obtained. The Na|Na3V2(PO4)3cells assembled with the M-PAN-GO separator have a superior polarization voltage of 0.76 Vrather than 0.97 V at 4 C in SIBs. This work provides a potential high-performance separator for SIBs and lithium-ion batteries.

Automated summary

In this study, an alkaline-solution-treated electrospun polyacrylonitrile separator with an in situ chemical-grafted graphene oxide (M-PAN-GO) was prepared via regulating the interfacial group. The M-PAN-GO separator exhibited accelerated transmission of Na+and Li+, with a higher Na+ transference number due to the efficient binding formed between oxygen-containing functional groups and Na+. Along with its desolvation capability, the M-PAN-GO separator showed high Na+ transference number and ion conductivity in the electrolyte, leading to superior polarization voltage in sodium-ion batteries. This work provides a potential high-performance separator for both sodium-ion batteries and lithium-ion batteries.