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キーワード:
Cathodes; Electrochemical impedance spectroscopy; Energy policy; Metal ions; Nuclear magnetic resonance; Renewable energy resources; Sodium compounds; Sodium-ion batteries; NASICON type structures; Operando; Operando X-ray diffraction; Rational design; Reaction mechanism; Single phase reactions; Single-phase reaction mechanism; Sodium intercalation; Sodium-deficient; X- ray diffractions; X ray diffraction
要旨:
The rational design of novel high-performance cathode materials for sodium-ion batteries is a challenge for the development of the renewable energy sector. Here, a new sodium-deficient NASICON phosphate, namely Na3.40□0.60Co0.5Fe0.5V(PO4)3, demonstrating the excellent electrochemical performance is reported. The presence of Co allows a third Na+ to participate in the reaction thus exhibiting a high reversible capacity of ≈155 mAh g−1 in the voltage range of 2.0–4.0 V versus Na+/Na with a reversible single-phase mechanism and a small volume shrinkage of ≈5.97 at 4.0 V. 23Na solid-state nuclear magnetic resonance (NMR) combined with ex situ X-ray diffraction (XRD) refinements provide evidence for a preferential Na+ insertion within the Na2 site. Furthermore, the enhanced sodium kinetics ascribed to Co-substitution is also confirmed in combination with electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and theoretical calculation. © 2023 Wiley-VCH GmbH.
