3D N-doped graphene nanomesh foam for long cycle life lithium-sulfur battery

- The nitrogen doping in graphene and etching graphene layers at the same time.
- The nanoholes on the graphene sheet have high density about 1.4 × 1010 holes per cm2.
- The graphene still stable due to the nanoholes on graphene layers with not excessive damage of graphene lattice.
- The nanoholes on graphene layers help the electrolyte infiltrate into the electrode.

The 3D N-doped graphene nanomesh foam (3DNGF) has been synthesized as the Lithium-sulfur battery cathode material for the first time. A method of in situ doping nitrogen and meanwhile etching graphene layer is introduced. The BET result shows the 3DNGF has a large specific surface area more than traditional three-dimensional graphene. Transmission electron microscopy (TEM) observation and Raman spectra confirm the nanoholes on the graphene. The 3DNGF/S composite exhibits an initial discharge capacity of 1134 mAh g−1 at 0.2C in the first cycle with the sulfur utilization of 67%. The electrode reserves a specific capacity of 578 mAh g−1 after 500 cycles at 0.5C, with a capacity decay of 0.06% per cycle. Its specific capacity at 2C can still reach to 729 mAh g−1, indicating the good rate performance.

The 3D N-doped graphene nanomesh foam (3DNGF) was synthesized by an in suit etching method. The nanoholes on the graphene sheets with diameter range approximately from 30 to 70 nm with high density about 1.4 × 1010 holes per cm2. The specific surface area of 3DNGF is 384 m2 g−1, much higher than the common 3D graphene. After 0.5C for 500 cycles, the 3DNGF/S exhibits a specific capacity of 578 mAh g−1 with a capacity decay only 0.06% per cycle. Even at 2C rate, the reversible specific capacity still was 729 mAh g−1.105