Analysis of sodium-ion batteries: lithium-ion batteries can form a combination

Lithium-ion battery is now limelight, set thousands of pet in one, but in this lively, a crisis is brewing, lithium-ion battery cousins - sodium-ion batteries are brewing power.

Sodium ion battery is the most important feature of the use of Na + instead of the expensive Li +, so the cathode material, anode material and electrolyte have to make the appropriate changes to adapt Na ion batteries. Compared to lithium, sodium is abundant in the earth's crust, and the method of obtaining Na is very simple, so it is more cost-effective than lithium-ion.

The concept of sodium-ion battery started not too late, the last century 80's and lithium-ion battery at the same time started. However, by the 90's, because Na ion battery energy density is lower than the lithium-ion battery, so gradually fade from people's vision. However, due to the relatively scarce resources of lithium resources, so the face of rising prices of lithium carbonate, making people once again concerned about sodium-ion batteries.

At present, the most difficult problem of sodium ion battery is finding a stable negative electrode material of sodium ion battery. The traditional negative electrode material of lithium ion battery, graphite, can combine with Li to form LiC6 compound with the theoretical capacity of 372mAh / g, but Graphite can store only a very limited amount of Na ions, probably because Na first forms a coating on the graphite surface rather than forming a compound with graphite.

In order to improve the performance of graphite materials, one of the research directions for graphite materials is to develop high-pitched graphite materials. For example, by increasing the layer spacing of graphite to 0.43 nm, a reversible capacity of 300 mAh / g or more can be obtained.

Hard carbon is also a negative electrode material that can store Na ions. Due to the low crystallinity of hard carbon materials and the low regularity of carbon atom layers, more Na ions can be stored and the capacity can reach over 300 mAh / g , But the cycle performance is poor. For example, the carbon nanofibers in one dimension have a capacity of only 176 mAh / g after 600 cycles.