Carbon Layer and CoO Nanosheet Dual-Encapsulated SiOx Particles for Ultra-High Specific Capacity Lithium-Ion Batteries

Silicon-based (Si-based) materials have attracted considerable attention due to their extremely high specific capacity, while the huge volume change up to 400% during cycling severely limits their widespread use. Silicon-oxygen (SiOx) anode materials, belonging to silicon-based materials, are considered to be more promising anode materials for practical applications due to their lower volume expansion without losing the high capacity. However, the existence of the volume expansion and the poor electrical conductivity of SiOx anode materials cannot be ignored. The encapsulation of SiOx particles by introducing a conductive carbon layer can greatly alleviate the volume expansion issue and improve the conductivity of the composites. In addition, to further boost the lithium storage capacity of the composites, the SiOx@C@CoO composites were obtained by an electrostatic self-assembly of CoO nanosheets onto the surface of SiOx@C materials. The introduction of CoO nanosheets increased the specific surface area of the composites, thereby enlarging the contact area with active Li+ and reducing the ion/electron transport radius, which in turn improved the lithium storage capacity of the composites. The final SiOx@C@CoO composite has an excellent electrochemical performance, with a reversible capacity of 1120 mAh g–1 after 100 cycles at 0.2 A g–1.