Pyrolytic carbon-coated Si nanoparticles on elastic graphene framework as anode materials for high-performance lithium-ion batteries

Silicon is one of the most attractive anode materials for next-generation lithium-ion batteries, but generally it has poor cycle performance because of its severe volume change during lithiation/delithiation and its low intrinsic electrical conductivity. We fabricated a ternary Si-based composite Si@C/GF in which Si nanoparticles were coated on a thin carbon layer by pyrolysis of phenolic resin and encapsulated in a graphene framework (GF). The GF provides an elastic and robust three-dimensional structure to buffer the large volume change of Si, while the PR-pyrolytic carbon not only limits the huge volume change of Si, but also retains good contact with both the GF and Si to maintain electrode integrity. As a result, the double-protected Si nanoparticles have a much improved cycle stability (85% capacity retention, ca. 650 mAh/g after 200 cycles at 1 A/g) as well as high specific capacity and good rate performance.