Logo: to the web site of Uppsala University

Lithium-sulfur (Li-S) batteries, renowned for their exceptional theoretical energy density, are positioned as a leading candidate for future energy storage systems, offering a potential pathway to overcome the energy density limitations of conventional lithium-ion batteries. Nevertheless, the notorious lithium polysulfides (LiPSs) shuttle effect and sluggish redox kinetics hinder their practical application. To resolve these challenges, we report a novel NiO-Ni₂P/C₃N₄ heterostructure synthesized via an in-situ phosphation process. Herein, we present an in situ phosphorylation strategy for the construction of NiO-Ni₂P heterojunctions anchored on a conductive C₃N₄ substrate (NiO-Ni₂P/C₃N₄) for further integration into commercial polypropylene (PP) separator (denoted as NiO-Ni₂P/C₃N₄@PP). Mechanistic studies demonstrated that the NiO phase facilitated strong chemisorption of LiPSs, while the Ni₂P component reduced the energy barrier for Li₂S dissolution through optimised d-band electron transfer. Concurrently, the C₃N₄ framework enhanced the interfacial charge transfer and significantly reduced the charge transfer resistance. Benefiting from the synergistic “adsorption-transformation-conduction” triple-function, the cells with the NiO-Ni₂P/C₃N₄@PP separator exhibit remarkable cycling stability (over 300 cycles at 3C) and outstanding rate capability (82.5 % capacity retention after 200 cycles at 5C). This work provides atomic-level insights into the engineering of multi-step sulfur electrochemical heterostructures, providing a generic design paradigm for high-energy metal-sulfur batteries.

Redox mediators (RMs) have shown promise in enhancing Li-O₂ battery cycling stability by reducing overpotential. However, their application is hindered by the shuttle effect, leading to RM loss and Li anode corrosion. Here, we introduce a polyionic liquid, poly (1-Butyl-3-vinylimidazolium bis(trifluoromethanesulfonylimine)) ([PBVIm]-TFSI) as an additive, showcasing a novel Li anode protection strategy for LiI-mediated Li-O₂ batteries. [PBVIm]⁺ cations migrate to the Li anode, forming a protective cationic shield that promotes uniform Li⁺ deposition. The addition of [PBVIm]-TFSI enhances the cycling stability, achieving 105 cycles at 200 mA⋅g⁻¹, compared to the cell with LiI which exhibited 38 cycles under the same conditions. Synchrotron X-ray tomography reveals the evolution of this protective layer, providing insights into its formation mechanism, in conjunction with XPS analysis. Our findings offer a new approach to Li anode protection in Li-O₂ batteries, emphasizing the critical role of interfacial engineering for battery performance.

The polysulfide shuttling effect and safety concerns associated with liquid electrolytes impede the commercialization of lithium-sulfur (Li-S) batteries. We report a novel gel polymer electrolyte (GPE) denoted as "PTPHS" prepared via facile ultraviolet polymerization of pentaerythritol tetrakis (3-mercaptopropionate) (PETT) and pentaerythritol tetraacrylate (PETEA) with poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the polymer matrix. Soluble starch (SST) is incorporated as an interacting filler to construct a 3D network structure with intermolecular hydrogen bonds. This unique architecture not only ensures high ionic conductivity and mechanical robustness but also effectively mitigates the polysulfide shuttling effect, thereby improving cycling stability. The PTPHS-based Li-S cell exhibits stable cycling over 150 cycles at 0.2 C with 87.6 % capacity retention. This strategy provides insights into material development and structural design of GPEs for highperformance quasi-solid-state Li-S batteries.

In situ characterization on interface stability has been hardly tried in redox mediator (RM)-involved Li-O₂ battery thus far. Here, benzyltriethylammonium iodide (BTEAI) can act as a self-defensive RM in the electrolyte LiTFSI/TEGDME to enhance the reaction kinetics and increase the cycling stability by suppressing the redox shuttling. I^- effectively reduces the charging overpotential by changing decomposition route for Li₂O_2. BTEA⁺ can facilitate LiTFSI decomposition in the electrolyte, and participate in formation of an organic–inorganic composite SEI-contained layer on Li anode. Moreover, for the first time, non-destructive synchrotron X-Ray tomography is used to investigate the mechanism of suppressing shuttle effect by monitoring the morphological evolution of electrodes interface. This work provides an insight into the development of functional RM and in situ protection strategies for Li anodes in Li-O₂ batteries.

Although lithium iodide (LiI) as a redox mediator (RM) can decrease the overpotential in Li-O₂ batteries, the stability of the Li anode is still one critical issue due to the redox shuttling. Here, we firstly present a novel approach for generating Ag and LiTFSI enriched Li anode (designated as ALE@Li anode) via a spontaneous substitution between pure Li and bis(trifluoromethanesulfonyl)imide silver, in a LiI-participated Li-O₂ cell. It can induce the generation of a lithiophilic solid electrolyte interphase (SEI) enriched with Ag, F, and N species (e.g., Ag₂O, Li-Ag alloy, LiF, and Li₃N) during cell operation, which contributes to promoting the electrochemical performance through the shuttling inhibition. Compared to a cell with a bare Li anode, the one with as-prepared ALE@Li anode shows an enhanced cyclability, a considerable rate capability, and a good reversibility. In addition, a synchrotron X-ray computed tomography technique is employed to investigate the inhibition mechanism for shuttling effect by monitoring the morphological evolution on the cell interfaces. Therefore, this work highlights the deliberate design in the modified Li anode in an easy-to-operate and cost-effective way as well as providing guidance for the construction of artificial SEI layers to suppress the redox shuttling of RMs in Li-O₂ batteries.

The role of oxygen vacancies in enhancing photocatalytic activity has attracted increasing attention. In this work, ZnO nanorods with enriched surface oxygen vacancies were successfully synthesized via a facile hydrothermal process combined with calcination in the presence of urea, and the content of the oxygen vacancies could be tuned by adjusting the calcination temperature and time. The characterization results proved that the content of oxygen vacancies reached 45.47% with a calcination temperature and time of 500 degrees C and 4 h, respectively. Additionally, the increased oxygen vacancy content was conducive to not only narrowing the ZnO bandgap, but also accelerating the separation and transfer of photoproduced electron-hole pairs, thus enhancing the methylene blue (MB) removal. The maximum removal efficiency of MB reached 97.65% within 120 min under simulated sunlight irradiation, and the catalyst exhibited stable performance after five consecutive cycles. The degradation intermediates of MB determined by liquid chromatograph-mass spectrometer (LC-MS) were the aromatic and ring-opening products of demethylation, desulfurization and hydroxylation. The toxicities of these compounds decreased significantly based on the germination and growth of Vigna radiata. This study provides a controllable and simple strategy for the design of ZnO with abundant oxygen vacancies and high activity in a photocatalytic system under simulated sunlight.

The commercialization of lithium -sulfur (Li -S) batteries faces several challenges, including poor conductivity, unexpected volume expansion, and continuous sulfur loss from the cathode due to redox shuttling. In this study, we introduce a novel polymer via a simple cross -linking between poly(ether-thioureas) (PETU) and poly(3,4-ethylenedioxythiophene)- poly(styrenesulfonate) (PEDOT:PSS) as a bifunctional binder for Li -S batteries (devotes as "PPTU"). Compared to polyvinylidene fluoride (PVDF), as -prepared PPTU exhibits significantly higher electrical conductivity, facilitating electrochemical reactions. Additionally, PPTU demonstrates effective adsorption of lithium polysulfides, leading to improved cycling stability by suppressing the shuttling effect. We investigate this behavior by monitoring morphological changes at the cell interface using synchrotron X-ray tomography. Cells with PPTU binders exhibit remarkable rate performance, desired reversibility, and excellent cycling stability even under stringent bending and twisting conditions. Our work represents promising progress in functional polymer binder development for Li -S batteries. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Electrochemical water-splitting is widely acknowledged as a renewable strategy for hydrogen production, but it is primarily constrained by the sluggish reaction kinetics of the anode oxygen evolution reaction (OER). In our study, we employ a fast room-temperature corrosion engineering strategy for the construction of a sulfur-doped Ni-Fe layered dihydroxide catalyst (S-NiFe LDH). With the assistance of a sulfur source, microsphere morphology with an ultra-thin lamellar surface cross-arrangement can be rapidly grown on the surface of an iron foam substrate, ensuring a substantial electrochemical interface. The composition of Ni species in the catalysts can be regulated by simply adjusting the amount of Ni²⁺ and reaction time. Functioning as an OER catalyst, the S-NiFe LDH demonstrates high activity and reaction kinetics, featuring a minimal overpotential of 120.0 mV to deliver a current density of 10 mA cm⁻², a small Tafel slope of 39.5 mV dec⁻¹ and a notable electrical double-layer capacitance (C_dl) of 31.3 mF cm⁻². The remarkable electrocatalytic performance can be attributed to its distinctive three-dimensional (3D) structure and sulfur dopants, which effectively regulate the electrochemical interface and electronic structure of NiFe LDH. This work provides valuable insights for expeditious materials design.

Constructing a Z-scheme heterojunction with enhanced photocatalytic hydrogen evolution for graphitic carbon nitride-based (g-C3N4) composites is challenging because integrating g-C3N4 with other semiconductors, without specific band structure design, typically results in type I or type II heterojunctions. These heterojunctions have lower redox ability and limited enhancement in photocatalysis. Herein, we select highly crystalline carbon nitride (HCCN) as a proof-of-concept substrate. For the first time, we develop a AgBr nanosphere/HCCN composite photocatalyst that features an all -solid -state direct Z-scheme heterojunction for visible-light photocatalytic hydrogen evolution. The electron transfer mechanism is initially studied from the band structures and Fermi levels of HCCN and AgBr. It is subsequently confirmed by X-ray photoelectron spectroscopy (XPS), and electron microscopy. The close heterojunction contact and the built-in electron field of the Z-scheme heterojunction promote the migration and separation of photogenerated electrons and holes in the composite photocatalyst. Due to the redistribution of charge carriers, the photocatalyst shows superior redox capability and a markedly enhanced hydrogen evolution performance compared to its individual components. Combining all the advantages, AgBr nanosphere/HCCN reached an apparent quantum efficiency (AQE) of 6 % under the illumination of 410 nm, which is 4 times higher than that of the single HCCN component.

The utilization of the organic-inorganic hybrid photocatalysts for water splitting has gained significant attention due to their ability to combine the advantages of both materials and generate synergistic effects. However, they are still far from practical application due to the limited understanding of the interactions between these two components and the complexity of their preparation process. Herein, a facial approach by combining a glycolated conjugated polymer with a TiO2-X mesoporous sphere to prepare high-efficiency hybrid photocatalysts is presented. The functionalization of conjugated polymers with hydrophilic oligo (ethylene glycol) side chains can not only facilitate the dispersion of conjugated polymers in water but also promote the interaction with TiO2-X forming stable heterojunction nanoparticles. An apparent quantum yield of 53.3% at 365 nm and a hydrogen evolution rate of 35.7 mmol h(-1) g(-1) is achieved by the photocatalyst in the presence of Pt co-catalyst. Advanced photophysical studies based on femtosecond transient absorption spectroscopy and in situ, XPS analyses reveal the charge transfer mechanism at type II heterojunction interfaces. This work shows the promising prospect of glycolated polymers in the construction of hybrid heterojunctions for photocatalytic hydrogen production and offers a deep understanding of high photocatalytic performance by such heterojunction photocatalysts.