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.

Low electrolyte/sulfur ratio (E/S) is an important factor in increasing the energy density of lithium-sulfur batteries (LSBs). Recently, the E/S has been widely lowered using catalytic hosts that can suppress “shuttle effect” during cycling by relying on a limited adsorption area. However, the shelf-lives of these cathodes have not yet received attention. Herein, we show that the self-discharge of sulfur cathodes based on frequently-used catalytic hosts is serious under low E/S because the “shuttle effect” during storage process caused by polysulfides (PSs) disproportionation cannot be suppressed using a limited adsorption area. We further prove that the adsorption strength toward PSs, which is unfortunately weak in commonly-used catalytic hosts, is critical for effectively hindering the disproportionation of the PSs. Subsequently, to verify this conclusion, we prepare a sulfur-doped titanium nitride (S-TiN) catalytic array host. As the adsorption strength and catalytic activity of TiN can be improved by S doping simultaneously, the constructed S/S-TiN cathodes under a low E/S (6.5 μL·mg⁻¹) exhibit better shelf-life and cycle-stability than those of S/TiN cathodes. Our work suggests that enhancing the adsorption strength of catalytic hosts, while maintaining their function to reduce E/S, is crucial for practical LSBs.

Domain boundaries are regarded as the effective active sites for electrochemical energy storage materials due to defects enrichment therein. However, layered double hydroxides (LDHs) tend to grow into single crystalline nano sheets due to their unique two-dimentional (2D) lattice structure. Previously, much efforts were made on the designing hierarchical structure to provide more exposed electroactive sites as well as accelerate the mass transfer. Herein, we demonstrate a strategy to introduce low angle grain boundary (LAGB) in the flakes of Ni/Co layered double hydroxides (NiCo-LDHs). These defect-rich nano flakes were self-assembled into hydrangea-like spheres that further constructed hollow cage structure. Both the formation of hierarchical structure and grain boundaries are interpreted with the synergistic effect of Ni²⁺/Co²⁺ ratio in an “etching-growth” process. The domain boundary defect also results in the preferential formation of oxygen vacancy (Vo). Additionally, density functional theory (DFT) calculation reveals that Co substitution is a critical factor for the formation of adjacent lattice defects, which contributes to the formation of domains boundary. The fabricated battery-type Faradaic NiCo-LDH-2 electrode material exhibits significantly enhanced specific capacitance of 899 C·g⁻¹ at a current density of 1 A·g⁻¹. NiCo-LDH-2//AC asymmetric capacitor shows a maximum energy density of 101.1 Wh·kg⁻¹ at the power density of 1.5 kW·kg⁻¹.

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.