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Using {100} plane-capped cubic K0.33FeFe(CN)6/RGO as the cathode, an initial discharge–charge capacity of 159–161 mA h g−1 at 0.5C, and a superior capacity retention of 90.1% at 10C after 500 cycles can be obtained.

Low-cost manganese hexacyanoferrate (NMHCF) possesses many favorable advantages including high theoretical capacity, ease of preparation, and robust open channels that enable faster Na diffusion kinetics. However, high lattice water and low electronic conductivity are the main bottlenecks to their pragmatic realization. Here, we present a strategy by anchoring NMHCF on reduced graphene oxide (RGO) to alleviate these problems, featuring a specific discharge capacity of 161/121 mA h g at a current density of 20/200 mA g. Moreover, the sodiation process is well revealed by ex situ X-ray diffraction, EIS and Car-Parrinello molecular dynamics simulations. At a rate of 20 mA g, the hard carbon//NMHCF/RGO full cell affords a stable discharge capacity of 84 mA h g (based on the weights of cathode mass) over 50 cycles, thus highlighting NMHCF/RGO an alternative cathode for sodium-ion batteries.

Recently, abundant resources, low-cost sodium-ion batteries are deemed to the new-generation battery in the field of large-scale energy storage. Nevertheless, poor active reaction dynamics, dissolution of intermediates and electrolyte matching problems are significant challenges that need to be solved. Herein, dimensional gradient structure of sheet–tube–dots is constructed with CoSe2@CNTs–MXene. Gradient structure is conducive to fast migration of electrons and ions with the association of ether electrolyte. For half-cell, CoSe2@CNTs–MXene exhibits high initial coulomb efficiency (81.7%) and excellent cycling performance (400 mAh g−1 cycling for 200 times in 2 A g−1). Phase transformation pathway from crystalline CoSe2–Na2Se with Co and then amorphous CoSe2 in the discharge/charge process is also explored by in situ X-ray diffraction. Density functional theory study discloses the CoSe2@CNTs–MXene in ether electrolyte system which contributes to stable sodium storage performance owing to the strong adsorption force from hierarchical structure and weak interaction between electrolyte and electrode interface. For full cell, CoSe2@CNTs–MXene//Na3V2 (PO4)3/C full battery can also afford a competitively reversible capacity of 280 mAh g−1 over 50 cycles. Concisely, profiting from dimensional gradient structure and matched electrolyte of CoSe2@CNTs–MXene hold great application potential for stable sodium storage.

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