Tailoring Na2FePO4F nanoparticles as the high-rate capability and Long-life cathode towards fast chargeable sodium-ion full batteries

•Ultra-small Na2FePO4F were prepared by a modified colloidal synthesis.•Network structure endowed NFPF/C/MWCNTs with excellent electrochemical performance.•NFPF/C/MWCNTs exhibited a favorable structural reversibility.•NFPF/C/MWCNTs||HC showed excellent performances at an ultrahigh rate of 10C. Na2FePO4F (NFPF) with two-dimensional channels for transferring Na ions is considered as the promising cathode material for high-performance sodium-ion batteries (SIBs), while the electrochemical performance in full-cell devices remains unsatisfactory. Here, we developed a method combining high-boiling organic solvents assisted colloidal synthesis (HOS-CS) and subsequent calcination for preparing 20–30 nm of NFPF nanoparticles (NPs) wrapped by conductive carbon as the efficient cathode. HOS-CS demonstrated merits in terms of high utilization of precursors, high synthetic efficiency, and uniform distribution of both sizes and composition of NPs. Impressively, the as-obtained NFPF/C/MWCNTs delivered a reversible capacity up to 118.4 mAh/g at 0.1C. As a bonus, the full-cell configuration fabricated via NFPF/C/MWCNTs cathode and hard carbon (HC) anode demonstrated extraordinary rate capability and cyclic stability. Even at an ultrahigh rate of 10C, 54.7 mAh/g of initial reversible capacity and nearly 80.7 % of capacity retention after 200 cycles were achieved, highlighting the great potentials of NFPF/C/MWCNTs||HC full cell for practical applications in the fields of fast chargeable SIBs. This work offers a novel synthetic method for the preparation of efficient NFPF-based cathode.