Keun Yong Sohn

High‐capacity silicon anodes are attracting more attention, owing to their high theoretical capacities and low working potentials. However, massive volume changes and low intrinsic electric conductivity remain substantial challenges that limit the practical applications of these anodes in lithium‐ion batteries (LIBs). In this study, cobalt‐doped silicon nanoparticles with different Co concentrations (0.1 %, 0.3 %, and 0.5 %) are prepared by using a simple low‐temperature annealing process and are studied as anodes for LIBs. Compared to pure silicon, the obtained 0.5 % cobalt‐doped silicon anode can serve as a promising anode and shows a high discharge capacity of 3409 mAh g⁻¹ (97.2 % capacity retention vs. first reversible capacity) with 98.1 % coulombic efficiency after 40 cycles, at 200 mA g⁻¹. After a long 320 cycles, the electrode delivered 3029 mAh g⁻¹ with 86.4 % capacity retention. This cobalt‐doped silicon anode also exhibits superior rate capability and a highly stable long cycle life at higher current densities as well as high mass loading. These remarkable enhancements in electrochemical properties indicate that cobalt doping yields increased conductivity, mitigates volume expansion, and provides shorter lithium transportation lengths across the silicon nanoparticles.

In this study, a route to synthesize a Si@SiO_x/carbon nanoflake nanocomposite is proposed using ecological and polar solvent‐soluble ethyl cellulose as a promising new carbon source for obtaining silicon composites. Equal proportions of ethylcellulose and commercial nanosilicon powders are used to prepare the silicon/organic hybrid through an in situ chemical process, and the subsequent carbonization affords the Si@SiO_x/C composite. The SiO_x layer is partially formed using the employed method and air drying processes. As an anode electrode for lithium‐ion batteries (LIBs), the composite provides excellent reversible capacity (1830 mAh g⁻¹ at 200 mA g⁻¹ after 60 cycles) with 92 % capacity retention and superior rate performance (1464 mAh g⁻¹ at 3.2 A g⁻¹). The electrode with a high mass loading of 3.42 mg cm⁻² delivered discharge capacities of 753 and 387 mAh g⁻¹ at high current densities of 2 A g⁻¹ and 4 A g⁻¹_, respectively. These results show that the coupling of silicon nanoparticles with an oxide layer and a conductive carbon framework is an effective design to retain the inherent properties of the silicon‐based anode, exhibiting its potential for use as a low‐cost anode for practical applications.