Germanium Anode with Excellent Lithium Storage Performance in a Ge/Lithium-

Transcription

1 Supporting Information Germanium Anode with Excellent Lithium Storage Performance in a Ge/Lithium- Cobalt-Oxide Lithium-Ion Battery Xiuwan Li, Zhibo Yang, Yujun Fu, Li Qiao, Dan Li, Hongwei Yue, and Deyan He* Figure S1. a) XRD patterns and b) micro-raman spectra of the Co 3 O 4 and Ge/Co 3 O 4 nanostructures on Ni foam. 1

2 Figure S2. Cross-sectional SEM morphology of the coaxial Ge/Co 3 O 4 nanorod array. Figure S3. a) Cross-sectional STEM image of a single coaxial Ge/Co 3 O 4 nanorod. c-f) Corresponding line-scan STEM-EDS analysis. 2

3 Figure S4. Cyclic voltammograms for the coaxial Ge/Co 3 O 4 nanorod array electrode measured at a scan rate of 0.1 mv s -1 over a voltage range from 0.02 to1.0 V. Figure S5. Representative -charge voltage profiles at various C rates. 3

4 Figure S6. Discharge-charge capacity of the pure Co 3 O 4 anode at 500 ma cm -2 over a voltage range from 0.02 to 1 V, the inset is the corresponding galvanostatic -charge voltage profiles in the 1st and 50th cycle. Figure S7. a-c) SEM images at different magnifications and d) XRD pattern of the used commercial LCO powder. 4

5 As shown in Figure S7, the used commercial LCO powder is composed of irregular particles. The size of the particles is about 5~10 µm and the surface is relatively smooth. Eight typical diffraction peaks located at 18.9, 37.4, 45.3, 49.4, 59.6, 65.5, 64.4, and 69.7 are observed in Figure S7d, corresponding to the (003), (101), (104), (015), (107), (018), (110), and (113) planes of LCO (JCPDS ), respectively. Figure S8. Electrochemical performance for the used commerical LCO cathode. a) Cyclic voltammograms for the initial three cycles. b) Discharge-charge capacities at a current density of 100 ma g -1, the inset is the corresponding galvanostatic -charge voltage profiles in the second cycle. Figure S8a shows the CV curves of the used commerical LCO cathode, which were recorded in the potential window of V versus Li/Li + at a scan rate of 0.1 mv s -1. Two obvious peaks located at 4.1 and 3.8 V can be observed for the cathodic and anodic scan, 5

6 respectively. As shown in Figure S8b, the initial charge and capacities are 183 and 167 ma h g -1 at a current density of 100 ma g -1, respectively. After 30 cycles, the capacity of the LCO cathode can still remain at 168 ma h g -1. The inset in Figure S8b shows the corresponding charge- voltage profiles in the second cycle. The electrode exhibits two extended voltage plateaus at about 4.0 and 3.8 V for charge and curves, which is consistent with the CV results. Figure S9. a) The 2nd charge (LCO electrode in half-cell, upper) and (Co 3 O 4 electrode in half-cell, lower) curves. b) The 2nd (LCO electrode in half-cell, upper) and charge (Co 3 O 4 electrode in half-cell, lower) curves. 6

7 Figure S10. a) Digital image of a special device for chronopotentiometry. b) V-t curve of the Ge/Co 3 O 4 nanorod array electrode deduced from chronopotentiometry, the low cut-off voltage was set to be 0.7 V. Figure S11. Ragone plot of the Ge/LCO full-cell. 7

8 Table S1. The capacities of the Ge/Co 3 O 4 nanorod array electrodes in the selected cycles at various C rates Rate 1st 100th 298th 383th 500th 600th 0.5 C C C C C The formula of the energy and power are as follows. W = UIt= ItdU (1) P= W t = ItdU t (2) In this work, the current I is a constant, and for the used multichannel battery tester (Neware BTS-610), the minimum time interval t is a constant too. For each t, it will give a corresponding U in the and charge processes. So, t = n t and Eqs. (1) and (2) can be converted as follows. n W = Itd U = I t U k (3) k= 1 n P= W t = I U k n (4) k= 1 8