Oxyphosphate; In situ methods; Synthesis; Characterization; Diffraction; Electrochemical energy storage; Lithium-ion batteries
Godbole VA, Heß M, Villevieille C, Kaiser H, Colin J-F, Novák P (2013), Circular in situ neutron powder diffraction cell for study of reaction mechanism in electrode materials for Li-ion batteries, in RSC Advances
, 3(3), 757-763.
Godbole VA, Villevieille C, Novák P (2013), Effect of metal ion and ball milling on the electrochemical properties of M0.5TiOPO4 (M = Ni, Cu, Mg), in Electrochimica Acta
, 93, 179-188.
Godbole Vikram Anil, Villevieille Claire, Sommer Heino-Harald, Colin Jean-Francois, Novak Petr (2012), A Structural and Electrochemical Study of Ni0.5TiOPO4 Synthesized via Modified Solution Route, in Electrochim. Acta
Godbole Vikram Anil, Colin Jean-Francois, Novak Petr (2011), Study of Overcharge Behavior of Li1+x(Ni1/3Mn1/3Co1/3)1 xO2 Using In situ and Ex situ X ray Synchrotron Diffraction, in J. Electrochem. Soc.
, 158(9), A1005-A1010.
The main goal of this project is the synthesis of new oxyphosphates as high specific charge capacity electrode material for Li-ion batteries.Since the commercialization of the first Li-ion battery by Sony in the early 90’s, oxides, especially LiCoO2, have represented the vast majority of cathodic materials. Even if great improvement have been achieved in the specific charge of this materials, their limits is likely to be soon reached. As the need for much higher specific charge is a major challenge on the way towards electrical vehicles based on Li-ion technology, new classes of materials have to be studied. The two first studies carried on oxyphosphates materials, namely Ni0.5TiOPO4 and Co0.5TiOPO4, have shown they were promising electrode materials with a first charge capacity higher than 400mAh/g and a reversible charge capacity of 275mAh/g. For comparison the specific charge capacity of commercial oxides is close to 150mAh/g. But a lot of questions have to be addressed such as the origin of this high capacity which is not understood yet. We propose herein to clear the reason behind this capacity and apply these results to the synthesis of new high specific charge capacity materials.The project will start with the synthesis of the two oxyphosphates already studied and their deeper electrochemical study and the structural characterization of the lithium insertion in these materials. The only few experiments reported on these compounds indeed show very complex electrochemical curves with evidence of several structure changes. Understanding these changes will help us to clarify the reason of the extra capacity but also of the irreversible capacity. These studies will be mostly carried in situ by synchrotron generated X-ray diffraction. This will allow us to get a really good time resolution and then be able to separate the different structural changes occurring in a narrow voltage window for these compounds. To get more insight on the lithium dynamics during the cycling in situ neutron diffraction will also be used. This latter technique is a real challenge as neutron diffraction and electrochemical cycling have very different optimal conditions. A new cell is now developed in our group to carry these experiments, and to the best of our knowledge no other cell is reported for this purpose.Then other ?xM’yMzOPO4 compounds belonging, as Ni0.5TiOPO4 and Co0.5TiOPO4, to the large lipscombite family will be synthesized and studied via the same methods, in order to build a structure/properties model clarifying the influence of each structural characteristics on the electrochemical behavior (specific capacity, working voltage, …). The amount of vacancies, which can reach up to 37.75%, the nature of M, M’ will be the factors on which we will play.Finally the results of the two previous tasks will allow us to design a brand new high specific charge electrode material. This “ideal” oxyphosphate will then be synthesized through a method derived from the ones used for the known compounds (using solid state or soft chemistry) and depending on the nature of the elements. Another goal of this project will be to take advantage of the structure/properties model to synthesize a MVOPO4 (M= Nb, V) with a lipscombite structure, this would complete the family of the lipscombites, as such compounds have never been reported although some extrapolation shows it should appear when the amount of vacancies reaches 50%.This project should open new perspectives for the search for high specific charge electrode materials. The fact that we cannot explain the origin of the entire charge capacity for the oxyphosphate class of materials indicates that new mechanism of intercalation is certainly underlying it. Getting comprehension on this new mechanism will help taking the step further towards a greener mobility.