Three-dimensional structured asymmetric electrolytes for high interface stability and fast Li-ion transport in solid-state Li-metal batteries

Replacing flammable liquid electrolytes with solid polymer electrolytes is a promising route to improve safety of lithium (Li)-metal batteries. However, developing a suitable high-performance electrolyte with both high ionic conductivity and interface stability against electrodes remains as a challenge. Herein, we design a poly(propylene carbonate) (PPC)/poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)]–based asymmetric solid electrolyte with a 3D blow-spun Li7La3Zr2O12 (LLZO) framework. The controllable degradation of PPC facilitates the wettability and stability between the electrolyte and Li metal. The P(VDF-HFP) with good electrochemical stability is used to match with cathode. With the support of the 3D LLZO Li-ion conductor, the electrolyte displays high ionic conductivity (4.9 × 10−4 S cm−1 at room temperature). The Li||Li symmetric cells assembled with this electrolyte show a long cycling life of more than 2700 h at 100 μA cm−2. The electrolyte also delivers an excellent cycling performance in solid-state LiFePO4||Li batteries (300 cycles with a capacity retention of 91.3%).