Fig. 2

Topotactic reaction pathways during multi-electron transfer in Fe₃O₄ revealed by in situ electron diffraction crystallography. a Represenative diffraction patterns recorded at 0′, 27′, 48′, 54′ (as labeled), respectively. The reflection spots associated with the initial Fe₃O₄, intermediate Li_xFe₃O₄ (being marked by a gray circle), FeO (red), and final phases of Li₂O (green), Fe-I (purple) and Fe-II (orange) indicate the crystallographic orientation of the Fe₃O₄/Li_xFe₃O₄, FeO, Li₂O, Fe-I and Fe-II phases, along the [1\(\bar1\)0], [1\(\bar1\)0], [1\(\bar1\)0], [100] and [10\(\bar1\)] directions, respectively, with well-defined correlation. See also details further elaborated by the movie (Supplementary Movie 1 on the whole process), and indexing of all the diffraction spots (Supplementary Fig. 2) in the Supplementary Information. b Intensity maps of the diffraction peaks (bottom), along 3 different crystallograhic directions as labeled by the boxes in (a) at 0′, and the corresponding intensity profiles at some of the intermediate/final states (top; at 27′, 48′, 54′ as labeled). c Integrated intensities of (111)_Fe3O4, (111)_LixFe3O4, (111)_FeO, (220)_Li2O, (011)_Fe-I and (101)_Fe-II as a function of lithiation time. d Evolution of lattice constant of the involved intermediate phases. The evolution of peak intensity and lattice constant demonstrates a multiple-stage phase transformation, from the intitial Fe₃O₄ to intermediates Li_xFe₃O₄, FeO, and final phases, Fe-I, Fe-II, Li₂O. The lattice constant of FeO is doubled for comparison with other ones. The error bars represent standard deviations of the fitting of intensity profiles (using a Gaussian function)