The leakage of liquid electrolyte and the formation of lithium dendrites pose challenges to safety and stability of lithium metal batteries (LMBs). The appearance of gel polymer electrolyte (GPE) has obviously improved the safety of traditional LMBs. However, the limited inhibition of GPE on lithium dendrites is detrimental to the safety of LMBs. Herein, a kind of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/gelatin (GN) GPE with high ionic conductivity, high-temperature resistance, and flame-retardancy, was prepared by electrospinning and soaking method. Utilizing the electrospinning network of PVDF-HFP, its affinity to liquid electrolytes, makes this GPE more beneficial to ions transport and the formation of gel. And, the GN with sol–gel properties, enhances the mechanical property (13.5 MPa) of HFP-GN GPE. Meanwhile, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) suggest that the attraction of polar groups of GN to Li⁺ can regulate the distribution of Li⁺ and protect Li anodes. Consequently, the application of HFP-GN GPEs to LMBs with cathodes of LiFePO₄ and LiCoO₂ deliver excellent electrochemical performances: after 300 cycles, the LiFePO₄/HFP-GN GPE/Li battery keeps a low capacity decay rate of 0.09% at 5 C; after 400 cycles at 2 C, the LiCoO₂/HFP-GN GPE/Li cell retains a high capacity retention of 74%. This GPE is demonstrated for the application prospect of safe LMBs.

Proper regulation of metal-nitrogen carbon (M-N-C) materials derived from zeolitic imidazolate frameworks (ZIFs) is essential to enhance the oxygen reduction reaction (ORR) performance. However, most of the reports focus on the component regulation, and the structure regulation of ZIFs-derived M-N-C materials by a simple preparation method has been barely reported. Herein, using a one-step electrospinning method with subsequent pyrolysis, we have prepared a bead-like cobalt-nitrogen co-doped carbon nanocage/carbon nanofiber (Co-N-C/CNF) composite electrocatalyst with the porous carbon nanocages arranged one by one in the highly conductive carbon nanofibers. Profiting from the fully exposed active sites and improved conductivity, the Co-N-C/CNF catalyst exhibits an excellent ORR performance even surpassing the commercial Pt/C catalyst. Density functional theory (DFT) results demonstrate that the Co_NP-N₁-C₂ active sites on Co-N-C/CNF make the core contribution to the improvement of ORR properties. Moreover, the zinc-air battery (ZAB) based on the Co-N-C/CNF catalyst also shows outstanding discharge performance. This study provides a new strategy for the preparation and structural design for ZIFs-derived M-N-C materials as efficient ORR catalysts.

Li-S batteries are considered as a highly promising candidate for the next-generation energy storage system, attributing to their tremendous energy density. However, the two-dimensional island nucleation-growth process of lithium sulfide leads to a thick insulating film covering the electrode, inducing slow electrons transfer and mass-transfer of ions and liquid sulfur species in working Li-S cells. Here, we demonstrate a bio-inspired strategy of constructing ant-nest-like hierarchical porous ultrathin carbon nanosheet networks with the implants of metallic nanoparticles electrocatalysts (HPC-MEC) as efficient nanoreactors enabling rapid mass transfer, via a simple and green NaCl template. Such nanoreactors with a large active surface area could effectively anchor polysulfides for mitigating the shuttle effect, facilitating uniformly thin Li₂S film, and promoting the mass transfer for fast sulfur species conversions. This helps contribute to a continuously high sulfur utilization in Li-S batteries with the HPC-MEC reactors. As a typical exhibition, cobalt embedded hierarchical porous carbon (HPC-Co) could realize to deliver a remarkably high specific capacity of 1, 540.6 mAh·g^-1, an excellent rate performance of 878.8 mAh·g^-1 at 2 C, and high area capacity of 11.6 mAh·cm^-2 at a high sulfur load of 10 mg·cm^-2 and low electrolyte/sulfur ratio of 5 μL·mg^-1.