Search Results (3)

In this study, we systematically analyzed selective lithium plating on graphite (Gr)–silicon (Si) composite anodes for lithium-ion batteries during fast charging, using electrochemical techniques. To achieve this, half-cells were first constructed with single Gr and Si electrodes, and lithium plating on each electrode was examined at different charging rates. It was observed that lithium plating on both electrodes began at a lower state of charge (SoC) as the charge rate increased. Furthermore, at a given charge rate, lithium plating occurred on the Si electrode at a lower SoC than on the Gr electrode. Based on the experimental findings, the lithium plating behavior of Gr and Si as a function of the charge rate was formulated to investigate the plating behavior of hypothetical composite electrodes with varying Gr–Si ratios. The lithium plating behavior observed on the actual composite electrode was consistent with that predicted from the hypothetical composite electrode, which was simulated using the same Gr–Si ratio based on the behaviors of the individual electrodes. By comparing the results from the single and composite electrodes, it is proposed that lithium plating occurs first on Si and then on Gr at low charge rates, whereas, at high charge rates, it proceeds first on Gr and then on Si. We discuss how to extrapolate the preferential plating signals—namely, plating onto Si at low charge rates and onto Gr at high charge rates—that are not directly evident in the signal from the actual composite electrode. Full article

Silicon (Si) is considered a promising anode active material to enhance energy density of lithium-ion batteries. Many studies have focused on new structures and the electrochemical performance, but only a few investigated the particulate properties in detail. Therefore, a comprehensive study on the impact of Si content (5, 10, 15 wt.%) and particle size (120, 160, 250 nm) of core–shell structured Si@Gr composites on particulate and electrode properties was conducted. It was shown that both parameters had significant impact on the specific surface area (SSA) of particles, which was later correlated to the initial capacities and coulombic efficiencies (ICEs). Furthermore, changes in pore size distribution and electrical conductivity were found. The built full cells showed high initial capacities (>150 mAh g⁻¹), good rate capability (75% at 1 C, 50% at 2 C) and ICEs (>80%). The energy density was found to increase by 32% at 15 wt.% Si compared to graphite (Gr), indicating the future potential of Si. In addition, the impact of a carbon coating was investigated (Si@Gr/C), which led to a reduction in SSA, improved particle stability and higher capacity retention. Consequently, this study emphasizes the importance of also investigating the particulate properties of Si anodes. Full article

Commercial Li-ion batteries typically incorporate a small amount of high-capacity silicon (Si)-based materials in the composite graphite-based anode to increase the energy density of the battery. However, very little is known about the effects of Si on the fast-charging behavior of composite anodes. Herein, we examine the effects of the Si/graphite ratio in the composite anode on the fast-charging behavior of full cells. We show that addition of Si increases the rate capability from 1C to 8C and improves the capacity retention in early cycles at 6C due to reduced overpotential in constant current charging cycles. The impacts of Si content on fast-charging aging were identified by Post-Test characterization. Despite realizing benefits of available capacity and reduced Li plating at 6C, silicon–electrolyte interactions lead the time-dependent cell performance to fade quickly in the long term. The Post-Test analysis also revealed the thickening of the electrode and nonuniform distribution of electrolyte decomposition products on the Si-containing anodes, as well as the organic-rich solid electrolyte interphase (SEI), which are the factors behind cell degradation. Our study sheds insight on the advantages and disadvantages of Si/graphite composite anodes when they are used in fast-charging applications and guides further research in the area by designing an optimized composition of Si incorporated in a mature graphite matrix. Full article