Sodium-ion battery, positive electrode plate for sodium-ion battery, positive active material, battery module, battery pack, and device

A sodium-ion battery, comprising a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution, wherein

• the positive electrode plate comprises a positive active material, a molecular formula of the positive active material satisfies NaaLibM0.7Fe0.3−bO2±δ, M is a combination of Mn and one of Cu, Zn, and Mg, 0.67<a<1.1, 0.05<b<0.2, 0<δ<0.1, and in a charge and discharge curve of a button battery made of the positive active material, a ratio of Rct to Rf of the positive active material satisfies 2<Rct/Rf<3 for the first cycle and 4.29≤Rct/Rf≤6.72 for the 100th cycle;
• Rct is a charge transfer resistance of the positive active material measured in the button battery based on alternating current impedance spectroscopy;
• and
• Rf is a diffusion resistance of the positive active material measured in the button battery based on the alternating current impedance spectroscopy,
• a median diameter Dv50 of the positive active material (μm), a specific surface area S (m2/g) of the positive active material, and the Rct/Rf satisfy:
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