The "dual-layer sulfur cathode" strategy: An In2S3/Bi2S3@rGO heterostructure as an interlayer/modified separator for boosting the areal capacities of lithium-sulfur batteries

The specific energies and energy densities of lithium-sulfur (Li-S) batteries are influenced by various cell parameters, including the sulfur loading, the sulfur weight percentage in the cathode, and the electrolyte/sulfur ratio. An In2S3/Bi2S3@rGO heterostructure was obtained by growing indium sulfide nanoparticles on the surface of bismuth sulfide nanoflowers in a graphene oxide (GO) solution via a one-step solvothermal approach. This structure was introduced as a modified separator/dual-layer sulfur cathode for Li-S batteries. The Bi2S3/In2S3 heterointerfaces act as active sites to speed up interfacial electron transfer, along with the entrapment, diffusion, and transformation of lithium polysulfides. A Li-S cell containing a dual-layer sulfur cathode (thin layer of In2S3/Bi2S3@rGO sandwiched between two thick layers of sulfur) and coupled with an In2S3/Bi2S3@rGO-coated separator suppressed the polysulfide shuttle effect. The cell based on the dual-layer sulfur cathode technology and operated at a current rate of 0.3C achieved a high capacity (7.1 mAh cm-2) after the 200th cycle, giving an electrolyte/sulfur ratio (10 µL mg-1) under a high sulfur loading (11.53 mg cm-2). These results demonstrate the unique nature of the dual-layer sulfur cathode technique, which can yield high energy density Li-S batteries with high sulfur loadings and low electrolyte/sulfur ratios.

Superhydrophilic/superaerophobic amorphous Ni3S2/NiMoS electrocatalyst for enhanced hydrogen evolution

It is important to develop electrocatalysts that are cheap and have high activity for hydrogen evolution reaction (HER). In this work, Ni3S2/NiMoS with amorphous phase and unique candied-haws shaped nanoarray structure was successfully grown on nickel foam (Ni3S2/NiMoS/NF) as efficient HER catalyst. Combining Ni3S2 with NiMoS resulted in the extension of the heterointerfaces between the materials, which facilitated the HER process in alkaline medium. The amorphous Ni3S2/NiMoS with disordered atom arrangement provided abundant active sites. Also, the unique morphology of the catalytic electrode simultaneously enabled it exhibit superhydrophilicity and underwater superaerophobicity. It is beneficial for the sufficient diffusion of the electrolyte onto the catalyst surface and the fast departure of hydrogen bubbles from the surface. As a result, the activity of Ni3S2/NiMoS/NF was higher than that of Pt/C even at high current densities. It is very valuable for industrial applications that require high current density. The superior stability of Ni3S2/NiMoS/NF compared to Pt/C further demonstrated that this catalytic electrode has potential for industrial applications.

Fabrication of dual-hollow heterostructure of Ni2CoS4 sphere and nanotubes as advanced electrode for high-performance flexible all-solid-state supercapacitors

High-energy-density and flexible supercapacitors have shown numerous application potential in modern portable electronics. However, the relatively low specific capacity, poor rate retentions, and limited durability have hindered their implement. Herein, a novel hierarchical dual-hollow electrode, composed of a hollow Ni₂CoS₄ sphere and outer hollow Ni₂CoS₄ nanotubes (Ni₂CoS₄HS-HTs), is elaborately constructed. The Ni₂CoS₄HS-HT-5 exhibits a high specific capacity of 817.5 C g^-1 at a current density of 1 A g^-1 with remarkable rate retention of 75.3% at 50 A g^-1. In an all-solid-state asymmetric supercapacitor of Ni₂CoS₄HS-HT-5//CAC, a high capacitance of 1511.5 mF cm^-2 at 5 mA cm^-2 is obtained with an exceptional energy density of 13.6 mWh cm^-3 at a power density of 92.6 mW cm^-3. In addition, the capacity retention reaches 96% over 2000 cycles at 20 mA cm^-3, implying the outstanding durability. The flexibility and mechanical stability are demonstrated by the intact electrochemical performances under different bending angles. As a proof-of-concept, two Ni₂CoS₄HS-HT-5//CACs in series could successfully illuminate 31 LED indicators for more than 8 mins. These fascinating electrochemical performances benefit from the novel electrode structure and depict great potential for modern energy storage applications.