Pre-curing treatment optimises the grain growth of high-performance Na super ionic conductor–type Na3V2(PO4)3 thin films for sodium-ion batteries

The rapid development of microelectronic devices has increased the demand for miniature energy storage systems that are highly safe and exhibit long cycling life and excellent energy density. However, the lack of low-cost and high-performance fabrication methods presents a significant challenge to thin-film electrode fabrication. This study reports a strategy combining controllable pre-curing treatment with rapid thermal annealing (RTA), which enables in situ fabrication of high-quality sodium vanadium phosphate [Na 3 V 2 (PO 4 ) 3 ] thin films. RTA facilitates the cleavage of weak metal–O bonds in the precursor film, whereas optimisation of the pre-curing duration (0–100 s) effectively eliminates organic residues and strengthens the carbon framework, suppressing particle agglomeration. This synergistic control substantially improves crystallization uniformity and film densification, resulting in a refined grain structure and highly oriented crystal facets. Under optimal conditions, the thin film demonstrates a high specific capacity of 85.6 mAh g −1 at a current density of 1 A g −1 , retains 72.5 mAh g −1 even at 20 A g −1 , and demonstrates 90.3 % capacity retention after 200 cycles. Moreover, the assembled full sodium-ion cell exhibits an average operating voltage of 1.3 V while maintaining 94.2 % capacity retention after 500 cycles. This study elucidates for the first time the synergistic regulation pathway of the pre-curing–RTA coupling mechanism in Na 3 V 2 (PO 4 ) 3 thin-film fabrication and proposes an advanced preparation strategy for cost-effective, highly integrated, high-power sodium-ion thin-film devices, providing critical theoretical foundations and robust technical support for next-generation all–solid state sodium microbattery design and development.