Fig. 1. XRD pattern of WO3 (WO-1 and WO-2) and WS2 (WS-1 and WS-2) nanocrystals. The peaks matched those of monoclinic phase WO3 (JCPDS No. 72-1048) and hexagonal phase WS2 (JCPDS No. 84-1398).
Fig. 2. SEM and TEM images showing the general morphology of (a) WO-1, (b) WO-2 (c) WS-1, and (d) WS-2. High-resolution TEM and corresponding FFT images reveal that the distance between the adjacent (010) planes (d020) is 3.8 Å for monoclinic phase WO3 nanocrystals and d010 is 2.7 Å for hexagonal phase WS2 nanosheets. EDX spectrum shows the composition of (e) WO3 (WO-2) and (f) WS2 (WS-2).
Fig. 3. Cyclic voltammetry curve of (a) WO-1 and (b) WO-2. (c) Charge and discharge voltage profiles of LIB half-cell using WO-1, tested between 0.01 and 3 V, at a rate of 0.1 C. (d) Charge/discharge capacity vs. cycle number for half cells using WO-1 and WO-2. The coulomb efficiency is plotted using the right axis. (e) Charge and discharge voltage profiles of LIB half-cell using WO-2, tested between 0.01 and 3 V, at a rate of 0.1 C. (f) Cycling performance of WO-1 and WO-2 as the C-rate is increased from 0.1 C to 5.0 C.
Fig. 4. Nyquist plots of (a) WO-1 and WO-2; (b) WS-1 and (b) WS-2, before the cycle of LIB. The equivalent circuit diagram is shown on the right.
Fig. 5. Cyclic voltammetry curve of (a) WS-1 and (b) WS-2. Charge and discharge voltage profiles of LIB half-cell using (c) WS-1, tested between 0.01 and 3 V, at a rate of 0.1 C. (d) Charge/discharge capacity vs. cycle number for half cells using WS-1 and WS-2. The coulomb efficiency is plotted using the right axis. (e) Charge and discharge voltage profiles of LIB half-cell using WS-2, tested between 0.01 and 3 V, at a rate of 0.1 C. (f) Cycling performance of WS-1 and WS-2, as the C-rate is increased from 0.1 C to 5.0 C.
Table 1. Summary of LIB half-cell capacities (mA h g-1) of WO3 and WS2 nanocrystals during cycles at a rate of 0.1C.
Table 2. Summary of the LIB half-cell capacities (mA h g-1) of WO3 and WS2 nanocrystals as the rate is increased from 0.1 C to 5.0 C.
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