N,S-codoped carbon dots as deposition regulating electrolyte additive for stable lithium metal anode

Lithium metal anode is widely studied owing to its feature of ultrahigh theoretical specific capacity with lowest electrochemical potential. Nevertheless, the inhomogeneous deposition of Li+ ions is apt to accelerate the emergence of dendritic Li, which is a brake on the practical application of lithium metal batteries. To solve this issue, herein, we propose nitrogen, sulfur-codoped carbon dots (N,S-CDs) as the deposition regulating additives of electrolyte to guide lithium ion homogeneous deposition. Within the electrolyte, N,S-CDs additives can absorb the surrounding Li+ ions and deposit homogeneously on the current collector, resulting in a uniform lithium deposition layer. As expected, at the presence of 0.3 mg/mL N,S-CDs, the long-term cycling stability over 1200 h and 300 h with low polarization are achieved both in the Li|Li symmetric cell at current density of 1.0 and 3.0 mA cm−2, respectively. Meanwhile, there is an obvious contrast between the capacity retention in the Li-S full cell between the cell with and without N,S-CDs. In addition, it is worth noting that the beneficial effect of N,S-CDs for stable lithium metal anode is firstly demonstrated by means of confocal laser scanning microscope as well.