Poly-dopamine carbon-coated stable silicon/graphene/CNT composite as anode for lithium ion batteries

To buffer the volume expansion of silicon during charge-discharge process, a 3D carbon-coated stable silicon/graphene/CNT (C@Si/GN/CNT/PDA-C) composite was prepared. Si nanoparticles (SiNPs) were first modified by hexadecyl trimethyl ammonium bromide (CTAB) to enhance their stability and dispersibility in water, then uniformly distributed in graphene/carbon nanotubes (GN/CNT) by electrostatic self-assembly, and ultimately encapsulated by carbonized poly-dopamine carbon layer (PDA-C) at high-temperature. PDA-C not only alleviates the volume expansion of Si and inhibits the direct contact of Si with electrolyte, but also acts as a bridge between the conductive GN/CNT and Si to maintain electrode integrity. As an anode material for lithium-ion batteries, the C@Si/GN/CNT/PDA-C exhibits a superior reversible capacity of 1946 mAh g ^{− 1} after 100 cycles with the capacity retention of 68.9% at a current density of 0.1 A g ^{− 1}, and over 1306 mAh g ^{− 1} after 100 cycles at 1 A g ^{− 1}. The excellent electrochemical performance of C@Si/GN/CNT/PDA-C is attributed to the stable hierarchical structure.