SnS2 quantum dot as bifunctional “electrolyte additive” for lithium metal anode

[Display omitted] •SnS2 quantum dots were used as bifunctional “electrolyte additive” for LMBs.•The SnS2 QDs was reduced to LiSn alloy and Li2S on the current collector.•The as-formed components stabilize the interface and induce uniform deposition.•SnS2 QDs-contained cells display superior performance in half- and full- cells. The practical application of lithium metal battery has been impeded by the uneven lithium deposition and lithium dendrite growth. In this work, the tin sulfide (SnS2) quantum dots (QDs) are dispersed in the electrolyte and used as “electrolyte additive” to help constructing the high-performance lithium metal anode. Prior to lithium deposition, the SnS2 QDs were reduced to satisfactory interface components Li2S and lithiophilic LiSn alloy during the activation process. The as-formed Li2S and LiSn alloy can stabilize the interface structure, facilitate efficient ion transportation, and induce uniform lithium nucleation. As expected, the Li//Cu half-cell using electrolyte containing SnS2 QDs shows obviously improved coulombic efficiency and symmetric cell cyclic performance, which can sustain for longer than 900 h at a current density of 1.0 mA cm−2 with ultra-low overpotential of 10 mV. Moreover, the full cell using LiFePO4 cathode exhibited both excellent rate capability and cycling performance, i.e., capacity retention of 96.7 % after 400 cycles at 1.0 C.