High-power high-density lithium rechargeable batteries are necessary to meet the energy demand of electric vehicles and high-power stationary grids. Here, we present a straightforward method for obtaining carbon nanofibers (CNFs) as a polysulfide barrier in Li-S cells, resulting in a significant increase in cell performance. CNFs were coated both on the separator and on the cathode. The CNF-coated cathode showed a specific capacity of 1010 mA h g−1 after 250 cycles at 0.2 C, with a capacity fading of 0.021% per cycle. In addition, at 1 C, it delivered 946 mA h g−1, thus presenting a fast Li+ transport with a good capacity. This result turns CNFs-coated cathodes into a promising system for obtaining high-performance Li-S cells.