1. The working principle of sodium ion battery is similar to that of lithium ion battery, which uses the process of embedding and deintercalating sodium ions between positive and negative electrodes to realize charging and discharging.

Secondly, the raw material of sodium salt is abundant and low in price, and the raw material cost is reduced by half compared with the ternary cathode material of lithium ion battery by using Fe-Mn-Ni-based cathode material; Because of the characteristics of sodium salt, it is allowed to use low concentration electrolyte (the conductivity of sodium salt is about 20% higher than that of lithium electrolyte with the same concentration) to reduce the cost; Sodium ions do not alloy with aluminum, and aluminum foil can be used as the current collector of negative electrode, which can further reduce the cost by about 8% and the weight by about 10%.

3. Due to the non-zero discharge characteristics of the sodium ion battery, the sodium ion battery is allowed to discharge to zero volts. The energy density of sodium ion battery is more than 100Wh/kg, which is equivalent to that of lithium iron phosphate battery, but the cost advantage is obvious, and it is expected to replace the traditional lead-acid battery in large-scale energy storage.

4. The research of sodium ion battery first started around 1980s. The electrochemical properties of electrode materials such as MoS2, TiS2 and NaxMO2 designed and developed in the early stage are not ideal, and the development is very slow. Finding suitable sodium ion electrode material is one of the keys to realize the practical application of sodium ion energy storage battery.

5. In recent years, according to the characteristics of sodium ion batteries, a series of anode and cathode materials were designed and developed, which greatly improved the capacity and cycle life, such as hard carbon materials, transition metals and their alloy compounds, polyanion materials, Prussian blue materials and oxide materials, especially layered NaxMO2(M= Fe, Mn, Co, V, Ti) and its binary and ternary materials.