Polyoxometalate Modified Separator for Performance Enhancement of Magnesium–Sulfur Batteries

The magnesium–sulfur (Mg-S) battery has attracted considerable attention as a candidate of post-lithium battery systems owing to its high volumetric energy density, safety, and cost effectiveness. However, the known shuttle effect of the soluble polysulfides during charge and discharge leads to a rapid capacity fade and hinders the realization of sulfur-based battery technology. Along with the approaches for cathode design and electrolyte formulation, functionalization of separators can be employed to suppress the polysulfide shuttle. In this study, a glass fiber separator coated with decavanadate-based polyoxometalate (POM) clusters/carbon composite is fabricated by electrospinning technique and its impacts on battery performance and suppression of polysulfide shuttling are investigated. Mg–S batteries with such coated separators and non-corrosive Mg[B(hfip)₄]₂ electrolyte show significantly enhanced reversible capacity and cycling stability. Functional modification of separator provides a promising approach for improving metal–sulfur batteries.     

Engineering Crystallinity and Oxygen Vacancies of Co(II) Oxide Nanosheets for High Performance and Robust Rechargeable Zn–Air Batteries

Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes highly rely on the rational design and synthesis of high-performance electrocatalysts. Herein, comprehensive characterizations and density functional theory (DFT) calculations are combined to verify the important roles of the crystallinity and oxygen vacancy levels of Co(II) oxide (CoO) on ORR and OER activities. A facile and controllable vacuum-calcination strategy is utilized to convert Co(OH)₂ into oxygen-defective amorphous-crystalline CoO (namely ODAC-CoO) nanosheets. With the carefully controlled crystallinity and oxygen vacancy levels, the optimal ODAC-CoO sample exhibits dramatically enhanced ORR and OER electrocatalytic activities compared with the pure crystalline CoO counterpart. The assembled liquid and quasi-solid-state Zn–air batteries with ODAC-CoO as cathode material achieve remarkable specific capacity, power density, and excellent cycling stability, outperforming the benchmark Pt/C + IrO₂ catalysts. This study theoretically proposes and experimentally demonstrates that the simultaneous introduction of amorphous structures and oxygen vacancies could be an effective avenue towards high-performance electrocatalytic ORR and OER.     

Synergistic Effect of Crosslinked Organic–Inorganic Composite Protective Layer for High Performance Lithium Metal Batteries

Maintaining a stable interface of lithium metal anodes (LMAs) by implementing a protective layer is a promising approach in extending the cycle life of lithium metal batteries (LMBs). Nevertheless, designing a protective layer with desired physicochemical properties is still a challenging task. Herein, an inorganic–organic composite protective layer consisting of fluorinated graphene oxide (FGO) (inorganic part) and polyacrylic acid (PAA) (organic part) that are in situ crosslinked via poly(ethylene glycol) diglycidyl ether (PEGDE) into a robust network is reported. The mechanical strength of FGO and the elasticity of the polymeric network jointly suppress the unwanted dendritic Li growth while fluorine-functional groups in FGO induce an LiF-enriched interface. This balanced inorganic–organic composite protective layer facilitates charge transfer kinetics for enhanced lithium-ion diffusion at the interface. Utilizing this protective layer, LMB full-cells with LiFePO₄ demonstrate negligible capacity loss for 100 cycles even under an extreme negative/positive capacity (N/P) ratio of 1.0. This study uncovers the possibility of highly robust, reliable LMBs by a sophisticatedly designed protective layer of widely used inorganic and organic components.     

Electrowetting-Assisted Generation of Ultrastable High Charge Densities in Composite Silicon Oxide–Fluoropolymer Electret Samples for Electric Nanogenerators

Electric nanogenerators that directly convert the energy of moving drops into electrical signals require hydrophobic substrates with a high density of static electric charge that is stable in “harsh environments” created by continued exposure to potentially saline water. The recently proposed charge-trapping electric generators (CTEGs) that rely on stacked inorganic oxide–fluoropolymer (FP) composite electrets charged by homogeneous electrowetting-assisted charge injection (h-EWCI) seem to solve both problems, yet the reasons for this success have remained elusive. Here, systematic measurements at variable oxide and FP thickness, charging voltage, and charging time and thermal annealing up to 230 °C are reported, leading to a consistent model of the charging process. It is found to be controlled by an energy barrier at the water-FP interface, followed by trapping at the FP-oxide interface. Protection by the FP layer prevents charge densities up to −1.7 mC m⁻² from degrading and the dielectric strength of SiO₂ enables charge decay times up to 48 h at 230 °C, suggesting lifetimes against thermally activated discharging of thousands of years at room temperature. Combining high dielectric strength oxides and weaker FP top coatings with electrically controlled charging provides a new paradigm for developing ultrastable electrets for applications in energy harvesting and beyond.     

Bio-Derived Materials Achieving High Performance in Alkali Metal–Chalcogen Batteries

Alkali metal – chalcogen batteries (ACBs) have attracted significant attention as next-generation energy storages because of high energy density and reasonable cost as compared to the up-to-date lithium-ion batteries. Nevertheless, their practical applications are harshly inhibited by some drawbacks, such as shuttle effects resulting from dissolved polysulfides and polyselenides, chalcogen volume expansion, and dendrite growth on metal anodes. Functional components, such as chalcogen host, binder, and interlayer, using various polar materials have been introduced to address these issues. Among them, bio-derived materials are regarded as novel eco-friendly alternatives. In this report, the authors focus on the unique physical/chemical/environmental properties of bio-derived materials used in ACBs, including active host materials, polymer binders, separators, and additives. The authors hope that the present report can provide some new insights and directions for future research on high-performance ACBs.     

Regulating Electronic Structure of Fe–N4 Single Atomic Catalyst via Neighboring Sulfur Doping for High Performance Lithium–Sulfur Batteries

Constructing high performance electrocatalysts for lithium polysulfides (LiPSs) adsorption and fast conversion is the effective way to boost practical energy density and cycle life of rechargeable lithium–sulfur (Li–S) batteries, which have been regarded as the most promising next generation high energy density battery but still suffering from LiPSs shuttle effect and slow sulfur redox kinetics. Herein, a single atomic catalyst of Fe–N₄ moiety doping periphery with S (Fe–NSC) is theoretically and experimentally demonstrated to enhance LiPSs adsorption and facilitated sulfur conversion, due to more charge density accumulated around Fe–NSC configuration relative to bare Fe–N₄ moiety. Thereafter, the graphene oxide supported Fe–NSC catalyst (Fe–NSC@GO) is modified to the commercial separator through a simple slurry casting method. Thus, Li–S cells with Fe–NSC@GO modified separators display high discharge capacity and excellent cyclability, showing 1156 mAh g⁻¹ at 1 C rate and a low capacity decay of only 0.022% per cycle over 1000 cycles. Even with a high sulfur loading of 5.1 mg cm⁻², the cell still delivers excellent cycling stability. This work provides a fresh insight into electrocatalyst structural tuning to improve the electrochemical performance of Li–S batteries.     

Organic-Carbon Core–Shell Structure Promotes Cathode Performance for Na-Ion Batteries

The organic-carbon core-shell structure is constructed for the cathode material of [N,N'-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g⁻¹) through an interesting strategy called the surface self-carbonization. As expected, the organic-carbon core–shell structure (PTCDI-DAQ@C) can endow PTCDI-DAQ the outstanding cathode performance in Na-ion batteries. In half cells using 1 m NaPF₆/DME, PTCDI-DAQ@C can maintain 173 mAh g⁻¹ for nearly one year, while PTCDI-DAQ quickly decreases from 203 to 121 mAh g⁻¹ only after 100 cycles. Meanwhile, the constructed Na-ion full cells with the Na-intercalated hard carbon anode can deliver the peak discharge capacity of 195 mAh g⁻¹_cathode and the high median voltage of 1.7 V in 0.9–3.2 V, corresponding to the peak energy densities of 332 Wh kg⁻¹_cathode and 184 Wh kg⁻¹_{total mass}, respectively. Notably, the electrode materials only include the very cheap elements of C, H, O, N, and Na. Furthermore, the Na-ion full cells can also show the very impressive high-temperature (197 mAh g⁻¹_cathode at 50 °C) and subzero (185/90 mAh g⁻¹_cathode at −10/−40 °C) performances, respectively. To the best of the authors’ knowledge, the comprehensive properties of the Na-ion full cells are the best results based on organic cathodes.     

Strategies for Realizing Rechargeable High Volumetric Energy Density Conversion-Based Aluminum–Sulfur Batteries

Aluminum–sulfur batteries (ASBs) are deemed to be alternatives to meet the increasing demands for energy storage due to their high theoretical capacity, high safety, low cost, and the rich abundances of Al and S. However, the challenging problems including sluggish conversion kinetics, inferior electrolyte compatibility, and potential dendrite formation are still remained. This review comprehensively focuses on summarizing the specific strategies from polysulfide shuttling inhibition to form smooth anodic Al activation/deposition. Especially, innovations in cathodic side for achieving electrochemical kinetic modulations, electrolyte optimizations, and anodic interface mediations are discussed. Upon detailed elaborating the formation process, influencing factors, and their interactions in the Al–S electrochemistry, a comprehensive summary of their causative mechanisms and the corresponding strategies are provided, including optimization of electrolytes, innovative in situ detections, and precise electrocatalytic strategies. Based on such a systematic understanding in the Al–S electrochemistry, the possible electrochemical reaction mechanism is deciphered more clearly and enlightened practical strategies on the future development of stable ASBs. Furthermore, future opportunities and directions of high-performance conversion-based Al–S batteries for large-scale energy storage applications are highlighted.     

Multi-Stage Porous Nickel–Iron Oxide Electrode for High Current Alkaline Water Electrolysis

Alkaline water electrolysis (AWE) is the promising technical pathway of large-scale green hydrogen production. The sluggish oxygen evolution reaction seriously hampers the water decomposition reaction kinetics for AWE, especially at high current density above 500 mA cm⁻². It is closely related with bubbles removal dynamic performance of porous electrodes. In this study, the multi-stage porous nickel–iron oxide electrode is prepared by a two-step electro-deposition method. The electrode shows good oxygen evolution reaction performance at high current densitiy of 1000 mA cm⁻², which is attributed to both the good electro-catalytic performance of NiFeO_x with nano-cone structure and good bubbles removal performance of porous Ni interlayer with the curved pore channels. Bubbles motion inside the pore channels is deeply analyzed by Lattice Boltzmann simulation of gas–liquid two-phase flows, combining with the experiments. The results indicate that bubbles motion speed is faster in curved pore channels than that in straight pore channels due to the role of bubble buoyancy. It illuminates the effects of pore channel curvature on bubbles motion for porous electrodes prepared by electro-deposition. It provides the possibility of designing porous electrodes with both good electro-catalytic performance and good bubbles removal performance by the electro-deposition method, from the view of industrial applications.     

Laser-Assisted Printing of Electrodes Using Metal–Organic Frameworks for Micro-Supercapacitors

Direct laser scribing, an advanced printing technique, has been recently developed to enable the carbonization of carbonaceous precursors in a rapid, precise, and cost-effective manner. Herein, it is reported that metal−organic frameworks (MOFs) can be converted into patterned derived carbon with desired structural features using a CO₂ infrared laser system. Metal species in MOFs play a key role in the morphology, porous structure, and crystallinity of the resulting laser-induced products by studying six representative MOFs. Diverse features such as ordered porous structure and continuous network microstructure can be obtained in the laser-induced MOF-derived carbon, which is influenced by the melting and boiling points of metals and their magnetic and catalytic behaviors. Furthermore, a core–shell structured composite (MOF-199@ZIF-67) has been designed and prepared for the fabrication of 12-interdigital electrodes derived from the composite by laser-assisted printing. The as-obtained electrodes with highly porous and hierarchical structure show an enhanced specific capacitance for micro-supercapacitors (MSCs). This work provides a complementary heat treatment method to produce MOF-derived carbon nanomaterials with desired structural features and patterns for MSCs and micro-device-related applications.     

In Situ Deformation Topology of COFs with Shortened Channels and High Redox Properties for Li–S Batteries

Covalent organic frameworks (COFs) with various topologies are typically synthesized by selecting and designing connecting units with rich shapes. However, this process is time-consuming and labour-intensive. Besides, the tight stacking of COFs layers greatly restrict their structural advantages. It is crucial to effectively exploit the high porosity and active sites of COFs by topological design. Herein, for the first time, inducing in situ topological changes in sub-chemometric COFs by adding graphene oxide (GO) without replacing the monomer, is proposed. Surprisingly, GO can slow down the intermolecular stacking and induce rearrangement of COFs nanosheets. The channels of D- [4+3] COFs are significantly altered while the stacking of periodically expanded framework is weakened. This not only maximizes the exposure of pore area and polar groups, but also shortens the channels and increases the redox activity, which enables high loading while enhancing host-guest interactions. This topological transformation to exhibit the structural features of COFs for efficient application is an innovative molecular design strategy.     

Advanced Zinc–Iodine Batteries with Ultrahigh Capacity and Superior Rate Performance Based on Reduced Graphene Oxide and Water-in-Salt Electrolyte

Aqueous rechargeable zinc–iodine batteries have received increasing attention in the field of portable electronics due to their high safety, low-cost, and great electrochemical performance. However, the insulated nature of iodine and the unrestricted shuttle effect of soluble triiodide seriously limit the lifespan and Coulombic efficiency (CE) of the batteries. Herein, a high-performance zinc–iodine energy storage system based on the hydrothermal reduced graphene oxide (rGO) and a high concentration zinc chloride water-in-salt electrolyte are promoted. The 3D microporous structures and outstanding electrical conductivity of rGO make it an excellent host for iodine, while the water-in-salt electrolyte effectively suppresses the shuttle effect of triiodide and improves the CE of the system. As a result, an ultra-high I₂ mass loading of 25.33 mg cm⁻² (loading ratio of 71.69 wt.%) is realized during the continuous charging/discharging process. The batteries deliver a high capacity of 6.5 mAh cm⁻² at 2 mA cm⁻² with a much-improved CE of 95% and a prominent rate performance with capacity of 1 mAh cm⁻² at 80 mA cm⁻². A stable long-term cycling performance is also achieved with capacity retention of 2 mAh cm⁻² after 2000 cycles at 50 mA cm⁻².     

In Situ Induced Core–Shell Carbon-Encapsulated Amorphous Vanadium Oxide for Ultra-Long Cycle Life Aqueous Zinc-Ion Batteries

Inevitable dissolution in aqueous electrolytes, intrinsically low electrical conductivity, and sluggish reaction kinetics have significantly hampered the zinc storage performance of vanadium oxide-based cathode materials. Herein, core–shell N-doped carbon-encapsulated amorphous vanadium oxide arrays, prepared via a one-step nitridation process followed by in situ electrochemical induction, as a highly stable and efficient cathode material for aqueous zinc-ion batteries (AZIBs) are reported. In this design, the amorphous vanadium oxide core provides unobstructed ions diffusion routes and abundant active sites, while the N-doped carbon shell can ensure efficient electron transfer and greatly stabilize the vanadium oxide core. The assembled AZIBs exhibit remarkable discharge capacity (0.92 mAh cm⁻² at 0.5 mA cm⁻²), superior rate capability (0.51 mAh cm⁻² at 20 mA cm⁻²), and ultra-long cycling stability (≈100% capacity retention after 500 cycles at 0.5 mA cm⁻² and 97% capacity retention after 10 000 cycles at 20 mA cm⁻²). The working mechanism is further validated by in situ X-ray diffraction combined with ex situ tests. Moreover, the fabricated cathode is highly flexible, and the assembled quasi-solid-state AZIBs present stable electrochemical performance under large deformations. This work offers insights into the development of high-performance amorphous vanadium oxide-based cathodes for AZIBs.     

Optimizing the Oxygen-Catalytic Performance of Zn–Mn–Co Spinel by Regulating the Bond Competition at Octahedral Sites

By using the more electro-negative Mn³⁺ ion to partially replace Co³⁺ at the octahedral site of spinel ZnCo₂O₄, i.e., forming ternary Zn–Mn–Co spinel oxide, the electrocatalytic oxygen reduction/evolution activity is found to be significantly increased. Considering the physical characterization and theoretical calculations, it demonstrated that the bond competition played a key role in regulating the cobalt valence state and the electrocatalytic activity. The partial replacement of octahedral-site-occupied Co³⁺ by Mn³⁺ can effectively modulate the adjacent Co–O bond and induce the Jahn–Teller effect, thus changing the originally stable crystal structure and optimizing the binding strength between the active center and reaction intermediates. Certainly, the Mn-substituted ZnMn_1.4Co_0.6O₄/NCNTs exhibit higher electrocatalytic oxygen reduction reaction (ORR) activity than that of ZnCo₂O₄/NCNTs and ZnMn₂O₄/NCNTs, supporting that the Co–O bond covalency determines the ORR activity of spinel ZnCo₂O₄. This study offers the competition between adjacent Co–O and Mn–O bonds via the B_Oh–O–B_Oh edge-sharing geometry. The ion substitution at octahedral sites by less electronegative cations can be a new and effective way to improve the electrocatalytic performance of cobalt-based spinel oxides.     

Manipulating the Light-Matter Interaction of PtS/MoS2 p–n Junctions for High Performance Broadband Photodetection

Due to the limited carrier concentration, 2D transition metal dichalcogenides have lower intrinsic dark current, and thus, are widely studied for high performance room photodetection. However, the light-matter interaction is still unclear, thus tuning the photoexcitation and further manipulating the photodetection is a challenge. Herein, large-area PtS films are synthesized, and the growth mechanism is investigated. It is demonstrated that PtS has an orthorhombic structure and exhibits the p-type semiconducting behavior. Then, MoS₂/PtS p–n heterojunction is fabricated, and its energy diagram is discussed based on the Kelvin probe force microscopy. The contact potential difference is about 160 mV, which is much larger than previous 2D junctions facilitating the charge separation. Furthermore, the phototransistor based on MoS₂/PtS p–n heterojunction is prepared, showing broadband photoresponse from visible to near-infrared. The manipulation of an external field on photoresponse, detectivity, and rise/fall time are explored and discussed. The responsivity can reach up to 25.43 A W⁻¹, and the detectivity is 8.54 × 10¹² Jones. These results indicate that PtS film is a prospective candidate for high-performance optoelectronic devices and broaden the scope of infrared detection materials.     

Single-Atom Cadmium-N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra-Long Lifetime

The rechargeable Li–CO₂ battery shows great potential in civil, military, and aerospace fields due to its high theoretical energy density and CO₂ capture capability. To facilitate the practical application of Li–CO₂ battery, the design of efficient, low-cost, and robust non-noble metal cathodes to boost CO₂ reduction/evolution kinetics is highly desirable yet remains a challenge. Herein, single-atom cadmium is reported with a Cd-N₄ coordination structure enable rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li–CO₂ battery, even up to 10 A g⁻¹, and remains stable at a high current density (100 A g⁻¹). An unprecedented discharge capacity of 160045 mAh g⁻¹ is attained at 500 mA g⁻¹. Excellent cycling stability is maintained for 1685 and 669 cycles at 1 A g⁻¹ and capacities of 0.5 and 1 Ah g⁻¹, respectively. Density functional theory calculations reveal low energy barriers for both Li₂CO₃ formation and decomposition reactions during the respective discharge and recharge process, evidencing the high catalytic activity of single Cd sites. This study provides a simple and effective avenue for developing highly active and stable single-atom non-precious metal cathode catalysts for advanced Li–CO₂ batteries.     

Effects of Fluorinated Diluents in Localized High-Concentration Electrolytes for Lithium–Oxygen Batteries

A stable electrolyte is critical for practical application of lithium–oxygen batteries (LOBs). Although the ionic conductivity and electrochemical stability of the electrolytes have been extensively investigated before, their oxygen solubility, viscosity, volatility, and the stability against singlet oxygen (¹O₂) still need to be comprehensively investigated to provide a full picture of the electrolytes, especially for an open system such as LOBs. Herein, a systematic investigation is reported on the localized high-concentration electrolytes (LHCEs) using different fluorinated diluents in comparison with those of conventional electrolytes. The physical properties and activation energies for reactions with singlet oxygen (¹O₂) of these electrolytes are calculated by density functional theory. The electrochemical performances of LOBs using these electrolytes are compared. This study reveals that the correlation between the stability of the electrolytes and their physical and electrochemical properties depends strongly on the diluents in LHCEs. Therefore, it shines light on the rational design of new electrolytes for LOBs.     

Prediction of the Magnitude of the Trapped Charge in the Buried Oxide of Silicon-on-Insulator Structures Using the Poole–Frenkel Effect

Semiconductors - The possibility of predicting the magnitude of the trapped charge in the buried oxide of silicon-on-insulator structures using the Poole–Frenkel effect is investigated. The...