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New lithium-ion batteries for electric vehicles
The lithium-ion battery, which is prominent in portable electronics, now positions itself in the markets of batteries for electric vehicles. Increasing the energy density of storage systems while controlling costs is becoming one of the challenges of the twenty-first century.
The operation of a lithium-ion battery is based on the reversible exchange of the lithium ion between a negative electrode, generally made of graphite, and a positive electrode, very often made of lithiated cobalt or manganese oxides, and more recently of lithium iron phosphate LiFePO4 for cost and safety reasons. Indeed, iron is much cheaper than cobalt or manganese and this very stable electrode produces no oxygen, which is the cause of battery explosions and fires.
However, LiFePO4 has intrinsic conductivity limitations that imply it must be used as nanoparticles and/or carbon deposits which respectively decrease the battery’s energy density and increase its cost.
Thanks to a special synthesis strategy centred around the use of ionic liquids, researchers from Amiens have synthesized a new material : fluorinated lithium iron sulphate LiFeSO4F, whose ionic and electronic conduction properties are much higher than LiFePO4, which facilitates the passage of lithium ions from one electrode to the other and thus the production of current. In addition, the specific forming of LiFePO4 is no longer required, which reduces the manufacturing cost of the electrode. The electrode of tomorrow’s Li-ion batteries…?
Laboratoire de réactivité et de chimie des solides, CNRS-Université de Picardie-Amiens Alistore-ERI, Fédération de recherche du CNRS
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