"Carbon in Metal" Anode with High Processability for Sodium Metal Batteries

Sodium metal batteries are ideal candidates for next-generationgrid-level energy storage systems. However, severe obstacles pertainwith regard to the usage of metallic Na, including poor processability,dendrite growth, and violent side reactions. Herein, we design a "carbonin metal" anode (denoted as CiM) via a facile method by rollinga controllable amount of mesoporous carbon powder into the Na metal.The as-designed composite anode is endowed with dramatically loweredstickiness and increased hardness (3 times higher than that of pureNa metal) and strength along with improved processability, which canbe fabricated into foils with varied patterns and limited thickness(down to 100 mu m). Besides, nitrogen-doped mesoporous carbon,which can increase the sodiophilicity, is applied to fabricate N-dopedcarbon in the metal anode (denoted as N-CiM), which can effectivelyfacilitate the diffusion of Na+ ions and decrease the depositingoverpotential, consequently homogenizing the Na+-ion flowand rendering a dense and flat Na deposition. Therefore, the N-CiManode offers enhanced cycling stability for 800 h at 1 mAh cm(-2) in symmetric cells and 1000 cycles with a high averageCoulomb efficiency (CE) (99.8%) in full cells based on the conventionalcarbonate electrolyte.