Entering 2021, NIO is focusing on solid-state batteries, while Panasonic intends to develop cobalt-free batteries. So, what is the relationship between solid-state batteries and cobalt-free batteries? Are solid-state batteries the same as cobalt-free batteries?
Early solid-state batteries used polymer electrolytes, with PEO (polyethylene oxide) being the most common. PEO's electrochemical stability window (oxidation potential) is 3.8V, which is incompatible with high-voltage cathode materials (lithium cobalt oxide, ternary materials, etc.). Only lithium iron phosphate could be used as the cathode, so the idea that cobalt was not used has been passed down.
However, early solid-state batteries had a drawback: their energy density was not high. For example, the solid-state battery from Bolloré in France used a PEO electrolyte and a lithium iron phosphate cathode, with an energy density of only 170Wh/kg and an operating temperature as high as 80 degrees Celsius. Therefore, it was not widely adopted and was only installed in 3,000 vehicles.
In other words, early solid-state batteries were actually lithium iron phosphate solid-state batteries, which did not use cobalt, so it is not an exaggeration to call them cobalt-free batteries.
With the development of battery technology, most solid-state batteries currently under research and development use cobalt-containing cathodes, primarily lithium cobalt oxide and ternary materials. The core of solid-state batteries is the electrolyte, which is currently mainly divided into two categories: polymer electrolytes and inorganic electrolytes. Inorganic electrolytes include oxides and sulfides, with electrochemical windows of approximately 5.4V and 5.7V respectively. Lithium cobalt oxide and ternary materials can be used to improve battery density and performance. Although other types of cathode materials are also under research, none are as mature as lithium cobalt oxide and ternary materials.
Using lithium cobalt oxide and ternary materials as cathodes can significantly improve the energy density of batteries. For example, Toyota also uses lithium cobalt oxide as its cathode material, achieving an energy density of 400 Wh/kg.
So here's the conclusion: solid-state batteries using lithium cobalt oxide and ternary materials as cathodes contain cobalt; these are not cobalt-free batteries.
Clearly, current cobalt-containing solid-state batteries are superior to earlier cobalt-free ones. Some argue that in the foreseeable future, solid-state batteries will inevitably require cobalt, and in a higher proportion than lithium-ion batteries!
