The market for Lithium-ion batteries is undergoing a rapid expansion as new applications demand higher performances, such as the use of higher voltage positive electrode materials, in our case the spinel LiNi0.4Mn1.6O4 and LiNi1/2Mn3/2O(4-d) positive electrode materials. We choose a very recently proposed low-cost deuterated and stable electrolyte (LiFSi/LiPF6 in EA) for in-situ neutron diffraction measurements, to be studied in the already existing liquid electrolyte-based cell ILLBATT#1. The goal will be to validate this combination "ILLBATT#1/newly deuterated electrolyte" using the high-voltage spinel LiNi0.4Mn1.6O4 positive electrode and optimize the neutron diffraction data obtained. The spinel electrode materials LiNi1/2Mn3/2O(4-d) will then be studied to determine the effect of cation ordering/disordering and oxygen vacancies on the mechanims involved upon cycling. Finally, we will use the newly-developed ILLBATT#2 to get information on the transport properties in these high voltage spinel oxides as a function of the composition and the state of charge.