Figure 3a shows the first three charge–discharge voltage profiles of HGS electrodes selleck chemicals vs. Li/Li+ at the current P505-15 purchase density of 50 mA g-1. The first charge curve for HGSs has plateaus at about 0.7 V representing the solid electrolyte interface (SEI) film formation and the generation of irreversible capacity.
From the second cycle, the charge/discharge curve of HGS slope without distinguishable plateaus, which can be attributed to the smaller crystallite structure, high specific surface area , and disorganized graphene stack [15, 16]. For HGSs, the first-cycle discharge and charge capacities are 1,794 and 902 mA h g-1, respectively. Obviously, the reversible capacity of HGSs is much higher than that of previously reported graphene nanosheets (672 mA h g-1 at a current density of 0.2 mA cm-2) . The possible reason is that the larger surface area and curled morphology of HGSs with fewer layers can provide more lithium
insertion active sites, such as edge-type sites and nanopores . The possible reversible reaction of Li with the residual H in the HGSs and faradaic contribution are also favorable to the large JAK inhibitor reversible capacity . It is well known that the disordered carbons can yield higher capacity values than graphite , and the graphene can be considered as a very disordered carbon. It should be noted that the HGS electrodes exhibit a broad electrochemical window (0.01 to 3.5 V) as a function of lithium
capacity and the large voltage hysteresis between discharge and charge voltage curves, which is different from graphite and similar to the nongraphitic carbons [21, 24–28]. The large voltage hysteresis is related to active defects in the disordered graphene nanosheets. The reaction of Li with the active defects in discharge processes occurs at low voltages, but the break of the relatively strong bonds of Li with the defects MYO10 in charge processes requires higher voltages, thus resulting in the large voltage hysteresis . The reversible specific capacity of the prepared HGSs reduced to 848 mA h g-1 in the second cycle, but it was still maintained at 741 mA h g-1 in the fifth cycle. This evidence indicates that the prepared HGSs exhibited stable cyclic performance from the second cycle because of the formed stable SEI film during the first discharge process. The cyclic voltammograms (CV) of the prepared HGSs are shown in Figure 4. The shape of the CV curves matches well with the discharge/charge profiles (Figure 3a). Figure 3 First three discharge/ charge profiles (a) and cycle performances (b) of HGSs at the current density of 50 mA g – 1 . Figure 4 Cyclic voltammograms (CV) of HGSs. Cycle performance of HGSs at different current densities of 50 mA g-1, 100 mA g-1, 200 m mA g-1, 500 m mA g-1, and 1,000 mA g-1 are shown in Figure 5. After 60 cycles, it was found that the reversible capacity was still maintained at 652 mA g-1 for HGSs.