In situ generation of Li3N concentration gradient in 3D carbon-based lithium anodes towards highly-stable lithium metal batteries

The uncontrolled dendrite growth of lithium metal anodes (LMAs) caused by unstable anode/electrolyte interface and uneven lithium deposition have impeded the practical applications of lithium metal batteries (LMBs). Constructing a robust artificial solid electrolyte interphase (SEI) and regulating the lithium deposition behavior is an effective strategy to address these issues. Herein, a three-dimensional (3D) lithium anode with gradient Li3N has been in-situ fabricated on carbon-based framework by thermal diffusion method (denoted as CC/Li/Li3N). Density functional theory (DFT) calculations reveal that Li3N can effectively promote the transport of Li+ due to the low energy barrier of Li+ diffusion. As expected, the Li3N-rich conformal artificial SEI film can not only effectively stabilize the interface and avoid parasitic reactions, but also facilitate fast Li+ transport across the SEI layer. The anode matrix with uniformly distributed Li3N can enable homogenous deposition of Li, thus preventing Li dendrite propagation. Benefiting from these merits, the CC/Li/Li3N anode achieves ultralong-term cycling for >1000 h at a current density of 2 mA cm−2 and dendrite-free Li deposition at an ultrahigh rate of 20 mA cm−2. Moreover, the full cells coupled with LiFePO4 cathodes show extraordinary cycling stability for >300 cycles in liquid-electrolyte-based batteries and display a high-capacity retention of 96.7% after 100 cycles in solid-state cells, demonstrating the promising prospects for the practical applications of LMBs.