A lithium nucleation-diffusion-growth mechanism to govern the horizontal deposition of lithium metal anode

The severe lithium (Li) dendrite growth leads to poor cycling stability and serious safety hazards of Li metal batteries, which completely impedes their practical applications. Herein, a novel Li nucleation-diffusion-growth mechanism based on Li-Sn alloy/Li3N electrolyte (LS/LN) composite interface layer is proposed, which synergistically guides the horizontal deposition of Li to suppress the vertical growth of Li dendrite and side reactions with the electrolyte. The lithiophilic Li-Sn alloy captures Li ions to nucleate preferentially on the alloy sites, and simultaneously the Li3N with low diffusion energy barrier and high Li-ion conductivity efficiently transports Li ions to nucleation sites during Li plating, consequently promoting the Li horizontal deposition. As a result, the LS/LN-Li symmetric cells can stably cycle 1600 h even at a high current density of 5 mA cm−2 and deposition capacity of 5 mA h cm−2. The LiFePO4∣LS/LN-Li cells with a high loading of 8.2 mg cm−2 present a high capacity retention of 93.4% after 1000 cycles, much higher than that using bare Li (64.8%). Furthermore, the LiNi0.8Co0.1Mn0.1O2∣LS/LN-Li cells present more excellent cycling stability than the cells using bare Li. The Li nucleation-diffusion-growth mechanism opens a promising route to solve the challenge of the vertical growth of Li dendrite and achieve highly stable Li metal batteries.