Researchers at the Bordeaux Institute of Condensed Matter Chemistry (CNRS/Bordeaux University, ENSCPB) working with at team from the CEA-Liten Innovation Laboratory for New Energy Technologies and Nanomaterials have shed light on this paradox. Their research results have just been published in the August issue of Nature Materials. Although lithium iron phosphate is the best candidate for the lithium batteries in future electric cars because of its qualities, the material does not have the ionic and electrical conduction properties needed to make the electrode work.
The scientists have shown that the charge-discharge cycles of the battery are made possible by a domino cascade process, a phenomenon occurring as soon as stress occurs at the interface between the discharging material and the material in the discharged state. Electrical and ionic conduction is then extremely rapid in the interfacial zone, spreading from one spot to the next like dominos as the interface moves. The model has been verified by microscopic measurements.
The novel reaction process resembling a wave sweeping through the crystal explains how two insulating materials (one in the charged state and the other in the discharged state) can nonetheless make lithium-ion batteries work. The results are an important step in the quest for new low-cost and safer electrode materials for future lithium batteries. The research has also cleared the way for understanding the processes taking place at the nanometer scale in lithium iron phosphate based batteries, which may be used in tomorrow's hybrid and electric cars.
