A stable artificial protective layer for high capacity dendrite-free lithium metal anode

The metallic lithium (Li) is considered as the most promising anode material for high-energy batteries. Nevertheless, the uncontrollable growth of Li dendrite and unstable electrolyte/electrode interface still hinder the development of Li-based battery. In this work, a novel strategy has been proposed to stabilize Li anode by in-situ polymerizing polypyrrole (PPy) layer on Ni foam (PPy@Ni foam) as an artificial protective layer. The PPy protective layer can effectively decrease the contact between Li metal and electrolyte during cycling. In addition, the morphology characterization shows that the PPy layer can help the even Li deposition underneath the layer, leading to a dendrite-free Li anode. As a result, when deposited 2 mAh·cm^-2 Li metal, the PPy@Ni foam can keep stable Coulombic efficiency (99%) during nearly 250 cycles, much better than the pure Ni foam (100 cycles). Even in the case of the Li capacity of 10 mAh·cm^-2, the stable cycling performance for 60 cycles can still be achieved. Furthermore, when assembled with LiFePO₄ material as the cathode for a full cell, the PPy@Ni foam can keep high capacity retention of 85.5% at 500 cycles. In our work, we provide a simple and effective method to enhance the electrochemical performances of Li metal-based batteries, and reveal a new avenue to design three-dimensional (3D) metallic current collector for protecting the Li metal anode.