Role of transition metals in layered Li[Ni,Co,Mn]O2 under electrochemical operation

With variations in compositions in layered LiNi,Co,Mn]O₂, we could change the several factors that might be considered to influence the electrochemical properties. The crystallographic characteristics of the samples were studied by neutron diffraction Rietveld analysis. After electrochemical operation, we measured the macroscopic crystal structure changes, the valence state of transition metals and the variations of interatomic distance for M-O (M: transition metal) through XRD and XAS. The variation in macroscopic lattice parameters was well coincident with the variation in microscopic structure changes viz. the variation of interatomic distance. We discussed the characteristics of transition metals in the structure and their effects on the electrochemical properties of the samples under electrochemical operation. We found that LiLi_1/10Ni_2/10Co_3/10Mn_4/10]O₂ with the lowest Ni/(Mn + Co) ratio among the samples showed the best capacity retention up to the 30th cycle.