Nanostructured Carbon Nitride Polymer-Reinforced Electrolyte To Enable Dendrite-Suppressed Lithium Metal Batteries

Lithium metal batteries (LMBs) containing S, O₂, and fluoride cathodes are attracting increasing attention owing to their much higher energy density than that of Li-ion batteries. However, current limitation for the progress of LMBs mainly comes from the uncontrolled formation and growth of Li dendrites at the anode side. In order to suppress dendrite growth, exploring novel nanostructured electrolyte of high modulus without degradation of Li-electrolyte interface appears to be a potential solution. Here we propose a lightweight polymer-reinforced electrolyte based on graphitic carbon nitride (g-C₃N₄) mesoporous microspheres as electrolyte filler [bis(trifluoromethanesulfonimide) lithium salt/di(ethylene glycol) dimethyl ether mixed with g-C₃N₄, denoted as LiTFSI-DGM-C₃N₄] for the first time. This nanostructured electrolyte can effectively suppress lithium dendrite growth during cycling, benefiting from the high mechanical strength and nanosheet-built hierarchical structure of g-C₃N₄. The Li/Li symmetrical cell based on this slurrylike electrolyte enables long-term cycling of at least 120 cycles with a high capacity of 6 mA·h/cm² and small plating/stripping overpotential of ∼100 mV at a high current density of 2 mA/cm². g-C₃N₄ filling also enables a separator(Celgard)-free Li/FeS₂ cell with at least 400 cycles. The 3D geometry of g-C₃N₄ shows advantages on interfacial resistance and Li plating/stripping stability compared to its 2D geometry.