High-energy-density batteries are seeing increasingly demand for many applications. Traditional Li-ion batteries based on metal oxide cathode and graphite anode, though under continuous improvement, cannot meet the requirement in the long term due to the theoretical limitation on reaction chemistry. The lithium-sulfur battery is a promising candidate for future energy storage because of its high energy density in theory. However, to achieve high energy density in practical applications, a high areal loading (~10 mg cm^-2) of active material – sulfur is required, which is hindered by deteriorating polysulfides shuttle and lithium dendrite formation. Previous research tackled the problems from either cathode side or anode side, and showed performance improvement based on a low areal loading (<3 mg cm^-2) of sulfur. Here we report a novel trench-wall carbon nanotube sponge acting as a dual host for high-areal-capacity sulfur cathodes and lithium anodes. Created by a controllable mechano-chemical method, the unique trench-wall structure provides nano-reactors for active materials with shortened diffusion length, polysulfides-philic and lithiophilic surface for hosting active materials, and increased surface area for promoting electrochemical reactions. The cell showed excellent areal capacity (10.3 mAh cm^-2) after 100 cycles under a high current density of 4.8 mA cm^-2, demonstrating both high “cell-level” energy density and power. The trench-wall CNT sponge is, to our best knowledge, the first single material used to simultaneously and effectively tackle the problems from both cathode and anode sides of lithium-sulfur batteries. The strategy of creating nano-trenches on the wall of carbon nanotubes paves a new way for designing new materials for high-energy-density batteries.