solid state sodium ion batteries on the way, page-13

A sodium-ion battery is a secondary battery. Sodium and lithium belong to the same main group of alkali metals on the periodic table and have similar physical and chemical properties to lithium. Similar to lithium-ion batteries, they rely on the reversible migration of sodium ions between the positive and negative electrodes for charging and discharging. Sodium-ion batteries were first proposed in the 1970s, but their research progressed very slowly for the next 30 years or so. It was not until around 2010 that academia returned to research on sodium-ion batteries, and in 2015 the first generation of sodium-ion batteries began to enter the commercialization process.

Sodium-ion batteries have their advantages, on the one hand, safety is sufficient, compared to lithium, the standard voltage range of sodium is larger, in a wider range of safety and applicability; on the other hand, sodium is relatively abundant and very evenly distributed in the earth's reserves, the crustal content of about 2.5%-3%, compared to lithium in the crustal content of only 0.65 ‰, and highly uneven distribution, the distribution of lithium. 80% of domestic lithium resources need to be imported.

Several indicators are not as good as lithium batteries

In the short and medium-term, sodium-ion batteries have many problems.

For one, the energy density is low. In the cathode, the mainstream sodium-ion battery cathode materials NaMnO4, Na3V2(PO4)3, Na2Fe2(SO4)3, etc., theoretical energy density is less than ternary lithium, the actual energy density is lower than lithium iron phosphate. The current energy density of lithium iron phosphate batteries can reach 200Wh/Kg, while sodium-ion batteries in the 100-150Wh/Kg, according to Guotai Junan's calculations, its ceiling can only reach 200Wh/Kg, just the level of lithium iron phosphate.

The negative electrode, sodium ion ionic radius is larger than lithium-ion, resulting in sodium-ion batteries needing to use hard carbon or other anode materials, energy density is lower than graphite materials.

Second, the charge and discharge rate is slow. The larger size makes it difficult to embed sodium ions in the crystal structure of the electrode where the chemical reaction occurs, resulting in a busier movement rate of sodium ions, which affects the charge and discharge rate of sodium ions.

Third, the cost is higher. The actual cost is currently more than 1 yuan / Wh, and the cost of lithium batteries, lithium iron is 0.5 yuan - 0.6 yuan / Wh, although the cost will drop in the future after mass production on a large scale (may drop to 0.2-0.3 yuan / Wh), but there may be quite a long way to go, take the negative electrode, the amount of hard carbon is still relatively small, and now there is no scale.

In addition, the technology of the lithium battery itself is also progressing, there is the possibility of further cost reductions, such as Tesla, which has already compressed the cost of the battery to the extreme, plans to increase the range of the battery pack in the next three years by another 54%, the cost continues to fall by 56%.

These issues determine sodium-ion batteries at least in the next 3 years is difficult to fully replace the possibility of lithium batteries for electric vehicles.