Multi-component solid PVDF-HFP/PPC/LLTO-nanorods composite electrolyte enabling advanced solid-state lithium metal batteries

Abstract

Substituting flammable and leaky liquid electrolytes with advanced solid composite electrolytes considered as one of the most hopeful strategy to develop solid-state lithium metal batteries with high security and high energy density. However, it is still an arduous task to develop a solid electrolyte with high ionic conductivity and wide electrochemical window. To this end, we designed three-component solid poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(propylene carbonate) (PPC)/Li0.33La0.557TiO3 (LLTO) nanorods composite electrolyte. Oxidation-resistant PVDF-HFP can stabilize the cathode of lithium metal batteries and widen the electrochemical window. The controlled degradation of PPC can wet and stabilize the interface between the electrolyte and the lithium metal anode to a certain extent. The introduction of LLTO nanorods not only decreases the crystallinity of the composite solid electrolyte, but also provides an additional path for the transmission of lithium ions, and improves the ionic conductivity of the electrolyte membrane (2.18×10−4 S·cm−1 at room temperature). The Li/PPLSE3/Li symmetric cell assembled with this electrolyte has a long cycling life of 2000 h at a current density of 0.1 mA·cm−2 at room temperature. The assembled NCM622/PPLSE3/Li full battery has a specific discharge capacity of 142 mAh·g−1 and a capacity retention rate of 84.6% after 100 cycles at room temperature.