3D Carbon-Based Porous Anode with a Pore-Size Gradient for High-Performance Lithium Metal Batteries

Three-dimensional (3D) hosts have been identified as the most promising anode design for lithium metal batteries (LMBs). This has been previously demonstrated to be extremely effective at inhibiting the dendrite growth by reducing the local current densities, resulting in stable cycle performances. However, due to the complex synthetic procedures and low lithium utilization ratios, the practical application of the 3D host anode still remains a challenge. To address these issues, the current study reports the development and synthesis of a 3D-carbon-based porous anode (3D-CPA) with a pore-size gradient using a practical slurry-based process in which the pore sizes decrease from the top to bottom layer. The pore-size gradient design accomplished using carbon materials enables stable Li plating/stripping into the entire inner pores without the formation of dendrites and also confirms the high energy density of LMB. The as-prepared 3D-CPA with a pore-size gradient also demonstrated a higher average coulombic efficiency of 98.8% (250 cycles) than other 3D-CPAs with mono-pore sizes. Additionally, its symmetry cell had a prolonged lifespan of 660 hrs at 1 mAcm^-2 (Li utilization ratio = 50%) and 680 hrs at 2 mAcm^-2 (Li utilization ratio = 30%). Remarkably, a pouch full cell composed of LiNi_0.6Co_0.2Mn_0.2 (NCM622) with 4 mA h cm^-2/as-prepared 3D-CPA retained 87.2% of its capacity after 100 cycles, using a carbonate-based electrolyte. The current study, therefore, highly suggests the use of 3D host designs for the fabrication of LMBs to achieve reversible Li reactions, leading to long-term stability.