Li6.25Al0.25La3Zr1.75Nb0.25O12 Nanofiber Fillers Reinforced PVDF-HFP-Based Bilayer Composite Solid-State Electrolytes

Composite solid-state electrolytes (CSEs) combining the advantages of polymer and ceramic electrolytes, are regarded as highly promising candidates for solid-state lithium metal batteries (SSLMBs). However, selecting appropriate polymer and ceramic materials, along with an effective combination method, is crucial in determining the performance of CSEs. To address the challenges of lithium dendrite inhibition and compatibility with cathodes simultaneously, herein, we have constructed a bilayer CSE based on poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP). Al/Nb co-doped Li_6.25Al_0.25La₃Zr_1.75Nb_0.25O₁₂ (LALZNO) nanofibers prepared by an electrostatic spinning technique, are incorporated as fillers to create high-throughput Li⁺ transport pathways and enhance the overall performance of the CSE. Furthermore, polypropylene carbonate is introduced on the anode side of the CSE to enhance the wettability of lithium metal/CSE interface, thus improving the stability of lithium upon cycling. On the cathode side, succinonitrile is added to inhibit the crystallization of PVDF-HFP and facilitate the fast Li⁺ transport. Consequently, the Li||Li cells demonstrate stable plating-stripping performance at 0.1 mA cm⁻² for >520 h. In addition, the Li||LiFePO₄ full cells show improved cycling and rate performance. This work validates the effectiveness of developing bilayer CSEs and showcases their potential application in SSLMBs.