Construction of lithophilic solid electrolyte interfaces with a bottom-up nucleation barrier difference for low-N/P ratio Li-metal batteries

The exploration of interface engineering is one of the critical maneuvers to develop high-energy-density Li metal batteries. Until now, the integrated regulation strategies on ionic conductivity of artificial solid electrolyte interphase (SEI) and lithiophilicity of anode substrate still demonstrate unsatisfactory results. Here, a robust LiF/LixMgy interfacial layer is in-situ constructed on the surface of Cu foil sputtered with Au to achieve bottom-up conductivity and lithiophilicity gradients, so as to regulate Li deposition preferentially between the ionic-conductive LiF/LixMgy SEI and high-lithiophilicity Au layer. Besides, high Young's modulus of the SEI indicates that the artificial layer has a strong ability to suppress dendrite growth during the process of cycling. As a result, the modified symmetric cells possess a long cycle lifespan over 2000 h with a low nucleation overpotential of 13.2 mV; the values are superior to most of the two-dimensional Cu-foil/plate modified strategies. Furthermore, at a low negative/positive electrode capacity (N/P) ratio of ∼ 1.5 and a lean electrolyte content of 6.0 μL g−1, the full cell can still exhibit an outstanding cycling stability for 400 cycles with a retention rate of 80.2%. This bottom-up conductivity and lithiophilicity gradients regulation strategy gives new insights for preferential Li deposition in safe positions and provides a facile approach for the construction of stable Li-metal anodes on commercial Cu foils.