A biomass derived carbon material is obtained by simple carbonization of cassava and it is used to prepare a carbon sheet as an interlayer for Li–S batteries. The as-prepared carbon sheet possesses macroporous structure and high conductivity, which is in favor of electrolyte permeation and helps to accelerate the electrochemical kinetics. The cell with the as-prepared interlayer shows superior rate performance and cyclability. Even at an ultrahigh rate (4 C, 1 C = 1675 mA h g_sulfur⁻¹), a discharge capacity of 640 mA h g⁻¹ is still retained for the cell. Meanwhile, the cell with the as-prepared interlayer exhibits a superior reversible capacity of 811 mA h g⁻¹ after 100 cycles at 0.5 C, and the discharge capacity retention is over 62%. The excellent electrochemical property probably is attributed to the high conductivity and macroporous structure of the as-prepared interlayer, which contribute to the accommodation of migrating polysulfides accelerating the transfer of electrons and ions, and consequently, enhancing the electrochemical reactivity of the cathode as well as suppressing the formation of the Li₂S layer on the cathode.