High-performance Si-Containing anode materials in lithium-ion batteries: A superstructure of Si@Co-NC composite works effectively

To mitigate the massive volume expansion of Si-based anode during the charge/discharge cycles, we synthesized a superstructure of Si@Co- NC composite via the carbonization of zeolite imidazolate frameworks incorporated with Si nanoparticles. The Si@Co-NC is comprised of Sinanoparticle core and N-doped/Co-incorporated carbon shell, and there is void space between the core and the shell. When using as anode material for LIBs, Si@Co-NC displayed a super performance with a charge/discharge capacity of 191.6/191.4 mA h g^-1 and a coulombic efficiency of 100.1% at 1000 mA g^-1 after 3000 cycles, and the capacity loss rate is 0.022% per cycle only. The excellent electrochemical property of Si@Co-NC is because its electronic conductivity is enhanced by doping the carbon shell with N atoms and by incorporating with Co particles, and the pathway of lithium ions transmission is shortened by the hollow structure and abundant mesopores in the carbon shell. Also, the volume expansion of Si nanoparticles is well accommodated in the void space and suppressed by the carbon host matrix. This work shows that, through designing a superstructure for the anode materials, we can synergistically reduce the work function and introduce the confinement effect, thus significantly enhancing the anode materials' electrochemical performance in LIBs.