Carbon dioxide solid-phase embedding reaction of silicon-carbon nanoporous composites for lithium-ion batteries

SiO 2 is one of the critical raw materials for preparing Si anode. The direct use of porous Si made from SiO 2 in LIBs is challenging. Although carbon cladding can improve the cycling performance of Si anode materials made from SiO 2 , the surface coating cannot address the comminution inside the material during repeated volume deformation. For the first time, we prepared an in-situ doped Si/carbon anode material that uses SiO 2 and CO 2 as Si and carbon sources and Mg as the reduction medium (Mg 2 Si + CO 2  → MgO + Si + C). The in situ embedded carbon completes the nanosizing of Si (less than50 nm) and forms a three-dimensional (3-D) carbon network that enhances electrical conductivity and acts as a buffer layer. After 500 cycles at 0.5 A g −1 , the discharge specific capacity is 912 mAh g −1 , and the capacity still has 1487 mAh g −1 even at 4 A g −1 . The simple method of preparing Si/carbon composite material in situ provides a new idea for modifying Si-based anode material and provides a valuable reference for carbon doping.