Polythiophene-coated porous silicon core-shell nanospheres (Si@PTh) composite are synthesized by a simple chemical oxidative polymerization approach. The polythiophene acts as a flexible layer to hold silicon grains when they are repeatedly alloying/dealloying with lithium during the discharge/charge process. The long lifespan and high-current-density rate capability (at a current of 8 A g(-1)) of the Si@PTh composite are vastly improved compared with as-prepared Si spheres. Typically, these Si@PTh composite electrodes achieve a reversible capacity of 1130.5 mA h g(-1) at 1 A g(-1) current density after 500 cycles, and can even possess a discharge capacity up to 451.8 mA h g(-1) at 8 A g(-1). The improved electrochemical performance can be ascribed to the synergy effects of the flexible PTh coating and the distinctive core-shell nanospheres with porous structure, which can largely alleviate the volume expansion of the Si during alloying with lithium.