Facile synthesis of Si/C composites for high-performance lithium-ion battery anodes†

Abstract

Nanotization and surface coating of silicon (Si) particles are effective methods to mitigate volume expansion and protect the solid electrolyte interphase (SEI) film during charge and discharge cycles. We utilized a magnesium-thermal reduction process to form nano-sized Si particles and applied a simple spray solidification and calcination technique to coat the surface with carbon (Si/C). The resulting carbon-coated core-structured Si/0.01C composite, with an optimal carbon layer, exhibits outstanding electrochemical performance. Specifically, it demonstrates a discharge capacity of 3119 mA h g⁻¹ at a current density of 0.2 A g⁻¹ and 1010 mA h g⁻¹ at 2 A g⁻¹. When employed in lithium-ion batteries (LIBs), the Si/0.01C electrode maintains a discharge capacity of 1159 mA h g⁻¹ after 173 cycles, with an impressive capacity retention of 85.8% between cycles 73 and 173, measured at 1 A g⁻¹. This assessment of its continuous cycling performance at 1 A g⁻¹ followed initial C-rate characterization (0.2 → 0.4 → 0.6 → 0.8 → 1 → 2 → 0.2 → 1 A g⁻¹). The enhanced capacity and cycling stability of the carbon-coated Si/C composite compared to those of pure Si nanoparticles are attributed to the encapsulation of Si nanoparticles within the carbon layer, which mitigates volume expansion.