A Fe₂C nanocrystals encapsulated into a nitrogen and sulfur dual doped carbon matrix (Fe₂C@C) was first synthesized by a simultaneous polymerization-precipitation technique followed with a high temperature pyrolysis process. This method can lead to an effective and homogenous distribution of core/shell Fe₂C nanoparticles into the carbon matrix. The optimized material was applied as an anode for a lithium-ion battery, which showed a high capacity, excellent rate performance, and good cycling capability. It delivered a high specific capacity of 657.7 mA h g^-1 at a current density of 0.2 A g^-1, and even at a very high current density at 6 A g^-1, the electrode still retained a very high specific capacity of 509.1 mA h g^-1. After 150 cycles of charge/discharge at a current density of 1 A g^-1, no capacity decay was observed which presents itself a promising high performance anode for LIBs. Also, the presence of Fe₂C can greatly stabilize the structure of the electrode and the electrode process for the lithiation/delithiation of LIBs.