Si@C Microsphere Composite with Multiple Buffer Structures for High-Performance Lithium-Ion Battery Anodes

In this work, a Si@C microsphere composite with multiple buffer structures is prepared by hydrothermal treatment to solve the fatal drawbacks of serious pulverization and low electronic conductivity of Si anodes. By virtue of ferric citrate being the carefully chosen coating carbon source, the silicon nanoparticles with a SiO_x layer are encapsulated by the homogeneous mesoporous carbon layer. The SiO_x layer with appropriate toughness can primarily suppress the volume expansion of silicon. The plentiful mesopores in the carbon layer and the framework formed by carbon nanotubes with good mechanical strength can effectively buffer and accommodate the volume change of silicon, and greatly improve the infiltration of the electrolyte to the anode. Meanwhile, the mesoporous carbon and carbon nanotube network also enhance the conductivity of the composite. Therefore, the Si@C electrodes exhibit a high initial charge/discharge capacity of 2956/4197 mAh g^-1 at a current density of 0.42 A g^-1 , excellent rate capability, and outstanding cycle performance up to 800 cycles by virtue of the multiple buffer structures.