Fig. 1

(a) XRD patterns of the as-synthesized Li x (Mg, Ni, Zn, Cu, Co)1-x O HEOs; (b) Lattice parameters and crystallite size calculated by the Rietveld refinement method"

Fig. 2

High-resolution XPS spectra of (a) Co 2p; (b) Ni 2p; (c) Li 1s; (d) Mg 1s; (e) Cu 2p; (f) Zn 2p and (g) O 1s for Li x (Mg, Ni, Zn, Cu, Co)1-x O"

Fig. 3

SEM images of (a) HEO 0; (b) HEO 8; (c) HEO 16 and (d) HEO 20 for Li x (Mg, Ni, Zn, Cu, Co)1-x O"

Fig. 4

(a) SAED pattern; (b) HAADF image and EDX mappings of Mg, Ni, Zn, Cu, Co, O；and (c) HRTEM image of HEO 0; (d) SAED pattern; (e) HAADF image and EDX mappings of Mg, Ni, Zn, Cu, Co, O；and (f) HRTEM images of HEO 16"

Fig. 5

CV curves of Li x (Mg, Ni, Zn, Cu, Co)1-x O electrodes obtained after (a) the first cycle and (b) the 2nd cycle; CV curves obtained for (c) HEO 0; (d) HEO 8; (e) HEO 16 and (f) HEO 20 electrodes after different cycles"

Fig. 6

(a) Voltage profiles obtained for Li x (Mg, Ni, Zn, Cu, Co)1-x O electrodes after the first cycle at 100 mA/g; (b) Voltage profiles obtained for HEO 0 electrode after different cycles at 100 mA/g; (c) Voltage profiles obtained for HEO 16 electrode after different cycles at 100 mA/g; (d) Cycling performance of Li x (Mg, Ni, Zn, Cu, Co)1-x O electrodes at 100 mA/g; (e) Rate capability of Li x (Mg, Ni, Zn, Cu, Co)1-x O electrodes; (f) Cycling performance of HEO 16 electrode at 1000 mA/g"

Fig. 7

(a) EIS spectra of fresh HEO 0 and HEO 16 electrodes and corresponding (b) fitting results; (c) EIS spectra of HEO 16 electrodes after different cycles and corresponding (d) fitting results; SEM images of HEO 16 electrodes (e) before cycling and after (f) the first cycle; (g) 10th cycles; (h) 50th cycles; and (i) 100th cycles"

Fig. 8

(a) CV curves of the HEO 16 electrode measured with different scanning rates; (b) relationship between Ip and logν for lithiation and delithiation peaks of the HEO 16; (c) contribution ratios of the capacitive and diffusion-controlled charge versus scan rates of the HEO 16；(d) CV curves of the HEO 0 electrode measured with different scanning rates; (e) relationship between Ip and logν for lithiation and delithiation peaks of the HEO 0; (f) Contribution ratios of the capacitive and diffusion-controlled charge versus scan rates of the HEO 0"