fig4

Figure 4. (A) Schematic of electrolyte design with viscoelastic ionic liquid (IL) as interlayers. In Li-metal batteries, the IL interlayers can buffer the interfacial contact and their viscoelasticity can efficiently facilitate the homogeneous deposition of Li ions^[63]. Copyright 2019, Wiley-VCH. (B) Schematic of a heterogeneous multilayered solid electrolyte. When the electrolyte is applied in Li-metal batteries, polyethylene glycol diacrylate (PEGDA) is on the Li anode side and poly(acrylonitrile) (PAN) faces the cathode side. The middle layer is the electrolyte Li_1.4Al_0.4Ge_1.6(PO₄)₃(LAGP) mixed with PAN^[71]. Copyright 2019, Wiley-VCH. (C) The Li-alloy interlayer can turn the surface from lithiophobic to lithiophilic. From the electrochemical impedance spectroscopy (EIS) measurements, the interfacial resistance of symmetric cells with lithiophilic garnet is much lower than that of lithiophobic garnet^[78]. Copyright 2016, American Chemical Society. (D) Comparison of interfaces with and without Li-metal alloy interlayer. The pristine garnet electrolyte exhibits poor wetting behaviors with Li. After coating a metal interlayer, a Li metal alloy will form at the interface and improve the contact, therefore improving the lithiophilicity and decreasing the interfacial resistance^[23]. Copyright 2017, American Association for the Advancement of Science. (E) Classifications of interfaces between Li metal and solid electrolyte along with the changes of Li potentials at different interfaces. Interface I indicates the thermodynamically stable interface. Interface II refers to the electronic isolating interface and interface III refers to the electronic conducting interface. The Li potential drops abruptly from the electrolyte to Li metal in interface II, which can effectively block side reactions^[84]. Copyright 2018, American Association for the Advancement of Science. (F) Comparison of Li stripping/plating behaviors in pristine solid electrolyte and methoxyperfluorobutane (HFE) treated electrolyte. Li dendrites can easily form in the pristine solid electrolyte. The introduced HFE can react with Li and form a LiF interlayer, which can efficiently inhibit dendrite growth. If the Li dendrites break the interlayer, the HFE in electrolytes can still consume the Li and repair the interlayer^[85]. Copyright 2018, Elsevier.