Silica Wastes to High‐Performance Lithium Storage Materials: A Rational Designed Al 2 O 3 Coating Assisted Magnesiothermic Process

Si/C yolk–shell structures have been developed to deal with the major issues associated with Si anodes: the huge volume changes and the low electrical conductivity. However, the fabrication process often involves expensive starting materials and/or simultaneously generates insulated SiC, which is harmful for Si anodes. Here, silica wastes from the optical fibers industry are used as starting materials to prepare high performance Si/C materials with Si@void@C yolk–shell structure via a rational designed Al 2 O 3 coating assisted magnesiothermic process. The obtained yolk–shell Si@void@C materials have a capacity of more than 1450 mA h g −1 after 100 cycles at 0.4 A g −1 . Thanks to the easily coated and removed Al 2 O 3 layer, the general formation of SiC can be avoided which is beneficial for improving the rate performances, and a capacity of ≈800 mA h g −1 is still kept after 200 cycles at a high rate of 10 A g −1 with a low capacity loss of 0.08% per cycle.