*3.2. Electrochemical Performance*

Figure 4a presents the capacity of all samples when cycled against Li for 200 cycles. It is seen that in all cases the capacity faded continuously with cycling. The lower SnS content electrodes (10SnS/AG and 10SnS/MCMB) had an initial capacity of ~630 mAh g−<sup>1</sup> that reduced to ~260 mAh g−<sup>1</sup> after 120 cycles. This is approximately the capacity of the carbon bases (AG and MCMB) used to support the SnS. The higher SnS content samples (20SnS/AG and 20SnS/MCMB) showed a higher initial capacity of over 700 mAh g<sup>−</sup>1, but a greater capacity decrease during cycling, which reached 100 mAh g−<sup>1</sup> after 120 cycles.

**Figure 4.** (**a**) Cycling performance of the different SnS/C samples; (**b**) discharge voltage capacity profiles for the 100th discharge of the 10SnS/AG, 20SnS/AG, and AG, and for the 2nd discharge of the 10SnS/AG.

The capacity fade shown in Figure 4a is consistent with the decay observed in [5,8], where after 45–50 cycles the initial capacity (~1000 mAh g−1) of SnS/C materials had decreased to half its original value. However, this study goes beyond previous studies, as it is the first to perform long term cycling for SnS/C materials. Particularly, Figure 4a indicates that, for low SnS contents (10%), the capacity drops to that of the graphite base, indicating that SnS may not be playing the role of an active material after initial cycling, while for higher SnS contents (20%), the capacity is much lower than that of both AG and MCMB after 200 cycles.

To better illustrate that, after long term cycling, the capacity of the SnS/C drops to that of pure carbon, the discharge curves at the 100th cycle for pure AG, 10SnS/AG, and 20SnS/AG are plotted together in Figure 4b. It can be observed that all three curves are in close proximity, indicating that the SnS ceased to partake in the reaction with continuous cycling. For comparison purposes, the 2nd discharge curves for the 10SnS/AG and pure AG anodes are also shown in Figure 4b, where it is clear that SnS contributes to the voltage capacity, as it is above the curves obtained after 100 cycles. It should be noted that the 2nd and 100th discharge curves coincide for pure AG and no distinction can be made between them in Figure 4b, which is consistent with the long term electrochemical stability of graphite. Further examination of Figure 4b indicates that the degradation of the voltage capacity curve during the 100th cycle is more severe for the 20SnS/AG material than for the 10SnS/AG material, which is consistent with the capacity fade seen in Figure 4a.
