It is understood that sodium-ion battery is a secondary battery (rechargeable battery) with a similar working principle to lithium-ion battery. The positive and negative electrodes are composed of two different sodium ion embedded compounds. During charging, Na+ is extracted from the positive electrode and embedded in the negative electrode through the electrolyte. At the same time, the compensation charge of the electrons is supplied to the negative electrode through the external circuit to ensure the charge balance of the positive and negative electrodes. During discharge, the opposite is true. Na+ is extracted from the negative electrode and embedded in the positive electrode through the electrolyte. Under normal charging and discharging conditions, the embedding and extraction of sodium ions between the positive and negative electrodes does not destroy the basic chemical stru...