Bare NCM-622 NCM-622@ TiO2 and NCM-622@Ti3+/TiO2 powder

Fig.1 is the SEM image and local enlargement of bare NCM-622NCM-622@ TiO₂ and NCM-622@ Ti³⁺/TiO₂powder samples, as well as TEM and HRTEM images of NCM-622@ Ti3+/TiO₂. Fig.1(a) shows that the morphological characteristics of NCM-622 particles are uniform, large spherical blocks composed of many small particles, and its average particle size is 20 um. It is distinct to see that the surface morphology of NCM-622 has changed after being coated with TiO₂. Comparing the partial enlarged image about Fig.1(a) and(b), We can find that the phase interface between the particles has become blurred, which is a good proof of the formation of a coating on the surface of LiNi_0.6Co_0.2Mn_0.2O₂, and comparing the partial enlarged image of Fig.1(b), we can find the surface morphology of the Fig.1(c) has changed. We speculate reasonably that the doping of Ti³⁺made the surface topography of the TiO₂ coating changed. In order to further visually detect whether the NCM surface is successfully coated with TiO₂ coating. we observed the coated sample with transmission electron microscope(TEM). As shown in Fig.1(d),a conformal amorphous coating layer with a thickness of 25nm.

which is obviously coated on the NCM-622 particles. What needs illustration is that NCM-622@ Ti3+/TiO2samples were made on the basis of NCM-622@ TiO₂ there is little difference between the two HRTEM graphs. Therefore, here we only show the HRTEM image of the NCM-622@ Ti³⁺/TiO₂ sample. Fig.1(e) is the high resolution transmission electron microscope (HRTEM) image of NCM-622@ Ti³⁺/TiO₂ the crystal structure of the coating on the surface of the NCM-622 electrode material can be intuitively seen from the figure. The lattice fringe spacing located on the (0 0 3) crystal plane is 0.475nm and the lattice fringe spacing located on the (101) crystal plane is 0.352 nm, they are LiNi_0.6Co_0.2Mn_0.2O₂and TiO₂ respectively. The mapping of multiple NCM-622@ Ti³⁺/TiO₂particles shows the distribution of the four elements of Ni, Co, Mn and Ti.(Fig.1(f)). The elements of Ti and O are both evenly distributed over the surface of each sample which illustrates that TiO₂was well deposited on the surface of NCM-622.

Fig. 1. (a) SEM micrograph of bare NCM-622 powders, (b) SEM micrograph of NCM-622@ TiO₂ particles, (c) SEM micrograph of NCM-622@Ti³⁺/TiO₂ powders, (d) TEM micrograph of NCM-622@Ti³⁺/TiO₂ particles, (e) HRTEM image of NCM-622@Ti³⁺/TiO₂ (f) elemental mapping recorded from one NCM-622@Ti³⁺/TiO₂ particle with corresponding mappings of different elements.

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