A low-strain metal organic framework for ultra-stable and long-life sodium-ion batteries

As sodium-ion batteries (SIBs) attract more attention, various host materials allowing Na-ions insertion/extraction are being developed. Among them, Prussian blue analogues (PBAs), as typical metal organic frameworks, are regarded as promising cathodes for SIBs because of their open frame structure and simple synthesis process. However, the presence of [Fe(CN)6] vacancies and crystal water in PBA framework usually induce poor electrochemical performance. Herein, high quality Na-rich monoclinic nickel hexacyanoferrate Na1.95Ni[Fe(CN)6]0.89·2.87H2O with nanocubes morphology (NiHCF–NCs) has been prepared through a simple diethylenetriaminepentaacetic acid disodium (Na2DTPA)-assisted coprecipitation strategy. Benefiting from inhibiting defects and low-strain sodium storage mechanism, as-obtained NiHCF–NCs exhibits superior electrochemical properties in terms of high capacity (81.3 mAh g−1), excellent rate capability (64.5 mAh g−1 at 4000 mA g−1), and outstanding cycle performance (97.1% capacity retention over 2000 cycles). Moreover, full-cell assembled with NiHCF–NCs cathode and NaTi2(PO4)3@C anode presents competitive behaviors of good rate capability and ultra-long cycle lifespan over 5000 cycles, greatly promoting the development of SIBs in practical application. [Display omitted] •Na2DTPA-assisted coprecipitation method for high quality Na-rich PBA material.•Controlled crystallization process induces excellent sodium storage performance.•The low strain during charge/discharge process for high stability of PBA material.•The sodium-ion battery delivers outstanding cycle life over 5000 cycles.