Boosting fast and durable sodium-ion storage by tailoring well-shaped Na_0.44MnO₂ nanowires cathode

Highlights: • Well-shaped Na_0.44MnO₂ nanowires were prepared via a controllable and green electrospinning-annealing route. • Na_0.44MnO₂ nanowires cathode enabled outstanding rate capability and unprecedented cycling stability in Na-ion batteries. • Highly reversible Na⁺ (de)insertion with low diffusion barrier and proper pseudocapacitive contribution was demonstrated. • A high-energy and long-life pouch-type Na-ion full battery was rationally constructed. -- Abstract: Na_0.44MnO₂ has drawn great attention as a promising cathode material for sodium-ion batteries (SIBs) owing to its unique tunnel-type structure that allows facile Na⁺ insertion/extraction. We here report the controllable preparation of Na_0.44MnO₂ nanowires (NMO NWs) through electrospinning and annealing processes and their SIB cathode application to boost the ionic diffusion dynamics and cyclic stability. The well-shaped NMO NWs with diameters of 50–200 nm effectively favour the easy access to electrolyte, facilitate the electrons/Na⁺ ions transportation, and retard the active materials fracture/pulverization upon prolonged cycling. Consequently, fascinating electrochemical performance in terms of high-rate capability (120.4 mAh g⁻¹ at 0.1C; 31.7 mAh g⁻¹ at 50C) and unprecedentedly long cycling life (89% capacity retention after 3300 cycles) is achieved. Furthermore, the underlying Na-ion storage mechanism and migration kinetics have been pioneeringly elucidated by a combination study of ex-situ structure/valence analyses and first-principles computations. The pseudocapacitive behaviour of NMO NWs electrode is also identified to benefit the high-rate performance. Finally, a pouch-type sodium-ion full battery assembled by the NMO NWs cathode and hard carbon nanofibers anode delivers an admirable energy density of 165.3 Wh kg⁻¹ and an outstanding capacity retention of 88.57% over 200 cycles, showing great prospects.