| Solid-state lithium metal batteries have attracted extensive attention due to their high energy density and safety.However,the poor interfacial contact of inorganic ceramic electrolyte and the low ionic conductivity of organic polymer electrolyte have become the main factors restricting the development of solid-state batteries.Combining inorganic ceramics with organic polymers by physical or chemical methods not only effectively alleviates the problem of interfacial contact,but also has no significant decrease in ionic conductivity compared with inorganic ceramics,so it becomes one of the powerful candidate materials for next-generation electrolytes.In this paper,two different types of composite electrolytes were synthesized by solution casting and in-situ polymerization respectively,and their applications in batteries were studied.The specific research contents are as follows:（1）We choose Li1.3Al0.3Ti1.7（PO4）3（LATP）with high ionic conductivity and environmental stability as filler,choose poly（vinylidene fluoride-co-hexafluoropropylene）（PVDF-HFP）with high dielectric constant as polymer matrix,and integrated them by solution casting method.In view of the instability of LATP to metallic lithium,we attached nanoscale Si O powder to the surface of LATP particles by ball milling.The existence of the Si O coated layer not only effectively improves the ionic conductivity(1.68×10-4 S cm-1 at 60℃),electrochemical window（4.8 V）and ion transport number（0.44）,but also avoids the side reaction between LATP and metallic lithium.Through the XPS test,we found that the chemical reaction between Si O and lithium metal forms a stable LixSi Oyinterface,which effectively improves the stability of electrolyte to metal lithium and realizes the free transport of ions between LATP phase and polymer phase.Through galvanostatic tests,the assembled Li/CSEs/Li symmetric batteries cycled over 800 h at a current density of 0.1 m A cm-2.（2）To solve the problem of the agglomeration of filler in the polymer,we used polyester fiber mesh as the matrix to fabricate 3D Li6.4La3Zr1.4Ta0.6O12（LLZTO）framework by casting-hot pressing.Then,3D composite was obtained by in situ polymerizing organic monomers with 3D LLZTO framework.Among them,3D LLZTO framework provides a continuous transport channel for ions,while the polymer realizes the tight connection between the electrolyte/electrode.The experimental results show that the addition of the 3D framework effectively improves the ionic conductivity of the electrolyte(1.96×10-3 S cm-1 at 60°C).meanwhile,the mechanical properties and thermal stability of the electrolyte have also been improved.Solid-state nuclear magnetic resonance results reveal that lithium ions can be transported along the ceramic and polymer phases as well as along the ceramic/polymer interface.The assembled LFP/CSEs/Li battery showed excellent cycling performance,with 89%capacity retention rate after 120 cycles at 0.1 C. |
