Porous nitrogen-doped carbon-coated nano-silicon/graphite ternary composites as high-rate stability anode for Li-ion batteries

Porous nitrogen-doped-carbon-coated nano-Si/graphite ternary composites were prepared by liquid-phase stirring, high-temperature calcination, and acid etching. At the Si and graphite mass ratio of 1:5 in the ternary composites, porous nitrogen-doped-carbon-coated nano-silicon particles were uniformly distributed into the graphite framework, which not only acts as active material for lithium storage but also provides high conductivity for Si particles. The porous amorphous nitrogen-doped carbon shells could further enhance both lithium ion and electrical conductivity of the composite and could also effectively relieve the volume expansion. The composite anode exhibited a highly stable specific capacity of 500 mAh g(-1) after 1000 cycles with the capacity retention of 95.5% at a high current density of 2000 mA g(-1). It also delivered a good rate performance of 739, 662, 589, and 507 mAh g(-1) at the current densities of 300, 500, 1000, and 2000 mA g(-1), respectively.