Solid-State Electrolytes with Ce-Doped LiNbO₃ Nanofiber Fillers Enable High-Performance Lithium Metal Batteries

As one of the most widely used composite electrolyte matrices, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) offers many advantages, such as excellent mechanical flexibility and a high dielectric constant. However, its inadequate mechanical strength leads to a limited ability to inhibit the growth of lithium dendrites, thus restricting its performance in solid-state lithium metal batteries. The key to overcoming this bottleneck lies in incorporating fillers to simultaneously improve the ionic conductivity and mechanical robustness of the electrolyte. In this work, lithium niobate (LiNbO₃) and Ce-doped lithium niobate (LiNb_0.9Ce_0.1O₃) nanofibers were employed as fillers in the PVDF-HFP-based electrolyte to promote the dissociation of lithium salts, thereby establishing a microenvironment conducive to efficient lithium-ion transport. The results demonstrate that when LiNb_0.9Ce_0.1O₃ nanofibers are incorporated as electrolyte fillers, the dissociation of lithium salt is enhanced, thereby improving the ionic conductivity and Li⁺ transference number of the composite electrolyte. Furthermore, the composite solid electrolyte incorporated with LiNb_0.9Ce_0.1O₃ nanofibers (LNCO CSE) exhibited an exceptional dendrite suppression capability, enabling lithium symmetric cells to operate stably at 0.1 mA cm^-2 for over 1100 h. The Li||LNCO CSE||LiFePO₄ full cells demonstrated outstanding rate performance and long-term cycling stability, delivering a reversible specific capacity of 136.9 mAh g^-1 after 600 cycles at 1C. Furthermore, the Li||LNCO CSE||LiNi_0.8Co_0.1Mn_0.1O₂ full cell also exhibited excellent rate capability, and its capacity retention rate reaches as high as 74.1% after 500 cycles at 0.5 C.