High performance porous Si@C anodes synthesized by low temperature aluminothermic reaction

A low temperature (210 °C) aluminothermic reaction process using a eutectic mixture of AlCl₃ and ZnCl₂ as the mediator has been developed to synthesize porous silicon (Si) as an anode for lithium (Li)-ion battery applications. With carbon pre-coating on the porous SiO₂ precursor, carbon coated porous Si (p-Si@C) core-shell structured anodes could be obtained with architecture and morphology similar to that of the porous SiO₂ precursor. The carbon coating network not only facilitates the electron and Li⁺ ion transportation, but also offers good mechanical support minimizing the particle pulverization that is associated with the large volume change of Si during lithiation/delithiation. As a result, p-Si@C anode demonstrates a high specific capacity of ∼2100 mAh g⁻¹ at the current density of 1.2 A g⁻¹ and significantly improved capacity retention of ∼89% over 250 cycles, which is much better than that of p-Si. Therefore, p-Si@C is promising anode for high-energy-density Li-ion batteries. The similar low temperature synthesis approach can also be used to prepare other functional materials.