Asymmetric Air Cathode Design for Enhanced Interfacial Electrocatalytic Reactions in High-Performance Zinc–Air Batteries

The rechargeable zinc–air battery (ZAB) is a promising energy storage technology owing to its high energy density and safe aqueous electrolyte, but there is a significant performance bottleneck. Generally, cathode reactions only occur at multiphase interfaces, where the electrocatalytic active sites can participate in redox reactions effectively. In the conventional air cathode, the 2D multiphase interface on the surface of the gas diffusion layer (GDL) inevitably results in an insufficient amount of active sites and poor interfacial contact, leading to sluggish reaction kinetics. To address this problem, a 3D multiphase interface strategy is proposed to extend the reactive interface into the interior of the GDL. Based on this concept, an asymmetric air cathode is designed to increase the accessible active sites, accelerate mass transfer, and generate a dynamically stabilized reactive interface. With a NiFe layered-double-hydroxide electrocatalyst, ZABs based on the asymmetric cathode deliver a small charge/discharge voltage gap (0.81 V at 5.0 mA cm⁻²), a high power density, and a stable cyclability (over 2000 cycles). This 3D reactive interface strategy provides a feasible method for enhancing the air cathode kinetics and further enlightens electrode designs for energy devices involving multiphase electrochemical reactions.     

Orbital Degeneracy, Jahn–Teller Effect, and Superconductivity in Transition-Metal Chalcogenides

We have studied the electronic structure of FeSe_1?x Te _x and Ir_1?x Pt _x Te₂ using photoemission spectroscopy. For FeSe_1?x Te _x , angle-resolved photoemission results indicate that the Fe 3d yz/zx orbital degeneracy at ?? point and orbitally induced Peierls effect in the tetragonal lattice play important roles for the superconductivity. It is suggested that the Jahn-Teller instability of the yz/zx states couples with local lattice distortion derived from the Te substitution for Se and provides an inhomogeneous electronic state. Photoemission results of IrTe₂ with triangular lattice are also consistent with the orbitally induced Peierls scenario. The Pt substitution for Ir suppresses the static band Jahn?CTeller effect and induces an inhomogeneous electronic state in which orbital (or bond or nematic) fluctuations may help superconductivity through the Peierls effect.     

Biomass-Derived Bifunctional Cathode Electrocatalyst and Multiadaptive Gel Electrolyte for High-Performance Flexible Zn–Air Batteries in Wide Temperature Range

High-efficiency and low-cost bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as gel electrolytes with high thermal and mechanical adaptability are required for the development of flexible batteries. Herein, abundant Setaria Viridis (SV) biomass is selected as the precursor to prepare porous N-doped carbon tubes with high specific surface area and the 900 °C calcination product of SV (SV-900) shows the optimum ORR/OER activities with a small E_OER–E_ORR of 0.734 V. Meanwhile, a new multifunctional gel electrolyte named C20E2G5 is prepared using cellulose extracted from another widely distributed biomass named flax as the skeleton, epichlorohydrin as the cross-linker and glycerol as the antifreezing agent. C20E2G5 possesses high ionic conductivity from −40 to + 60 °C, excellent tensile and compressive resistance, high adhesion, strong freezing and heat resistance. Moreover, the symmetrical cell assembled with C20E2G5 can significantly inhibit Zn dendrite growth. Finally, flexible solid-state Zn–air batteries assembled with SV-900 and C20E2G5 show high open circuit voltage, large energy density, and long-term operation stability between −40 and + 60 °C. This biomass-based approach is generic and can be used for the development of diverse next-generation electrochemical energy conversion and storage devices.     

Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS₂ and Mo₁ (S@MoS₂-Mo₁/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS₂-Mo₁/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g⁻¹ at 0.1 A g⁻¹ and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.     

Double-Walled NiTeSe–NiSe2 Nanotubes Anode for Stable and High-Rate Sodium-Ion Batteries

Electrodes made of composites with heterogeneous structure hold great potential for boosting ionic and charge transfer and accelerating electrochemical reaction kinetics. Herein, hierarchical and porous double-walled NiTeSe–NiSe₂ nanotubes are synthesized by a hydrothermal process assisted in situ selenization. Impressively, the nanotubes have abundant pores and multiple active sites, which shorten the ion diffusion length, decrease Na⁺ diffusion barriers, and increase the capacitance contribution ratio of the material at a high rate. Consequently, the anode shows a satisfactory initial capacity (582.5 mA h g⁻¹ at 0.5 A g⁻¹), a high-rate capability, and long cycling stability (1400 cycles, 398.6 mAh g⁻¹ at 10 A g⁻¹, 90.5% capacity retention). Moreover, the sodiation process of NiTeSe–NiSe₂ double-walled nanotubes and underlying mechanism of the enhanced performance are revealed by in situ and ex situ transmission electron microscopy and theoretical calculations.     

Study on Mn-induced Jahn–Teller distortion in BiFeO3 thin films

Present work reports Raman spectroscopy study of single-phase Mn-doped BiFeO₃ [BiFe_1?x Mn _x O₃ (0 ≤ x ≤ 0.20)] polycrystalline thin films carried out in backscattering geometry. De-convolution of Raman spectra showed a gradual transition in the crystal symmetry from rhombohedral (?R) to multiphase [rhombohedral (?R) + tetragonal (?T)] structure with increasing Mn doping concentration in BiFe_1?x Mn _x O₃ (BFMO) thin films. X-ray diffraction (XRD) along with Le-Bail extraction refinement confirms that the structural symmetry lowering in BFMO thin films occurs at about 10 % Mn doping concentration. A blue shift is observed in the direct energy band gap of BFMO thin films from 2.53 to 2.87 eV (at T = 295 K) and is attributed to the local symmetry lowering and local induced strain in Fe³⁺ environment resulted from Jahn–Teller distortion in (MnFe)³⁺O₆ octahedral unit. Second-derivative analysis of FTIR spectra in the spectral regions (420–470) cm^?1 and (480–680) cm^?1 further indicates the favourable structure distortion leading to the simultaneous exhibition of enhanced ferromagnetic and ferroelectric properties owing to Mn substitution in host BiFeO₃ lattice.     

Engineering Strategies for Suppressing the Shuttle Effect in Lithium–Sulfur Batteries

Lithium–sulfur(Li–S) batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost. Nevertheless, the shuttle effect of firm multi-step two-electron reaction between sulfur and lithium in liquid electrolyte makes the capacity much smaller than the theoretical value. Many methods were proposed for inhibiting the shuttle effect of polysulfide, improving corresponding redox kinetics and enhancing the integral performance of Li...     

Effect of Heterostructure-Modified Separator in Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries with high energy density and low cost are the most promising competitor in the next generation of new energy reserve devices. However, there are still many problems that hinder its commercialization, mainly including shuttle of soluble polysulfides, slow reaction kinetics, and growth of Li dendrites. In order to solve above issues, various explorations have been carried out for various configurations, such as electrodes, separators, and electrolytes. Among them, the separator in contact with both anode and cathode is in a particularly special position. Reasonable design-modified material of separator can solve above key problems. Heterostructure engineering as a promising modification method can combine characteristics of different materials to generate synergistic effect at heterogeneous interface that is conducive to Li–S electrochemical behavior. This review not only elaborates the role of heterostructure-modified separators in dealing with above problems, but also analyzes the improvement of wettability and thermal stability of separators by modification of heterostructure materials, systematically clarifies its advantages, and summarizes some related progress in recent years. Finally, future development direction of heterostructure-based separator in Li–S batteries is given.     

Introducing Hybrid Defects of Silicon Doping and Oxygen Vacancies into MOF-Derived TiO2–X@Carbon Nanotablets Toward High-Performance Sodium-Ion Storage

Titanium dioxide (TiO₂) is a promising anode material for sodium–ion batteries (SIBs), which suffer from the intrinsic sluggish ion transferability and poor conductivity. To overcome these drawbacks, a facile strategy is developed to synergistically engineer the lattice defects (i.e., heteroatom doping and oxygen vacancy generation) and the fine microstructure (i.e., carbon hybridization and porous structure) of TiO₂-based anode, which efficiently enhances the sodium storage performance. Herein, it is successfully realized that the Si-doping into the MIL-125 metal-organic framework structure, which can be easily converted to SiO₂/TiO_2–x@C nanotablets by annealing under inert atmosphere. After NaOH etching SiO₂/TiO_2–x@C which contains unbonded SiO₂ and chemically bonded Si O Ti, thus the lattice Si-doped TiO_2–x@C (Si-TiO_2–x@C) nanotablets with rich Ti³⁺/oxygen vacancies and abundant inner pores are developed. When examined as an anode for SIB, the Si-TiO_2–x@C exhibits a high sodium storage capacity (285 mAh g⁻¹ at 0.2 A g⁻¹), excellent long-term cycling, and high-rate performances (190 mAh g⁻¹ at 2 A g⁻¹ after 2500 cycles with 95.1% capacity retention). Theoretical calculations indicate that the rich Ti³⁺/oxygen vacancies and Si-doping synergistically contribute to a narrowed bandgap and lower sodiation barrier, which thus lead to fast electron/ion transfer coefficients and the predominant pseudocapacitive sodium storage behavior.     

Heterogeneous Mediator Enabling Three-Dimensional Growth of Lithium Sulfide for High-Performance Lithium–Sulfur Batteries

Two-dimensional(2D) deposition regime of insulating lithium sulfide(Li₂S) is a major obstacle to achieve high reversible capacity in the conventional glyme-based lithium–sulfur(Li–S) batteries as it leads to rapid loss of active electrode surface and low sulfur utilization. Achieving three-dimensional(3D)growth of Li₂S is therefore considered to be necessary, but the available strategies are mainly based on the electrolyte manipulations, which inevitably lead to added compl...     

1T-WS2 Nanosheet-Modified Biomass Carbon as Sulfur Host for High-Performance Lithium–Sulfur Batteries

The sluggish sulfur reaction kinetics and fast capacity attenuation still pose great challenges to lithium–sulfur (Li–S) batteries. Herein, tubular carbonl (HPOC) is obtained by carbonization of the cattail fiber. 1T-WS₂@HPOC is prepared by solvothermal method, and their sulfur composite, 1T-WS₂@HPOC/S and HPOC/S as sulfur host composite, is obtained by sulfur melting. The composite materials are characterized by scanning electron microscopy, X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, etc. Results show that 1T-WS₂ grows uniformly on the HPOC substrate and has abundant active sites, which can effectively improve the physicochemical adsorption capacity of S-fixation (76 wt%) and polysulfide. Battery assembly and electrochemical performance tests are conducted for the HPOC/S and 1T-WS₂@HPOC/S composites. Results show that the initial discharge capacity of the 1T-WS₂@HPOC/S positive electrode is 1272 mAh g⁻¹ at 0.1 C, higher than the HPOC/S positive electrode (1025 mAh g⁻¹). 1T-WS₂@HPOC/S maintains a discharge capacity of 695 mAh g⁻¹ after 500 cycles at 0.5 C, with a capacity decay rate of only 0.054% per cycle. With a discharge capacity of 504 mAh g⁻¹ after 400 cycles at 1 C, the Coulomb efficiency is 98.9%. The 1T-WS₂@HPOC/S composites with unique structure and excellent electrochemical performance have broad application prospects in the field of Li–S batteries.     

A High-Kinetics Sulfur Cathode with a Highly Efficient Mechanism for Superior Room-Temperature Na–S Batteries

Applications of room-temperature–sodium sulfur (RT-Na/S) batteries are currently impeded by the insulating nature of sulfur, the slow redox kinetics of sulfur with sodium, and the dissolution and migration of sodium polysulfides. Herein, a novel micrometer-sized hierarchical S cathode supported by FeS₂ electrocatalyst, which is grown in situ in well-confined carbon nanocage assemblies, is presented. The hierarchical carbon matrix can provide multiple physical entrapment to polysulfides, and the FeS₂ nanograins exhibit a low Na-ion diffusion barrier, strong binding energy, and high affinity for sodium polysulfides. Their combination makes it an ideal sulfur host to immobilize the polysulfides and achieve reversible conversion of polysulfides toward Na₂S. Importantly, the hierarchical S cathode is suitable for large-scale production via the inexpensive and green spray-drying method. The porous hierarchical S cathode offers a high sulfur content of 65.5 wt%, and can deliver high reversible capacity (524 mAh g⁻¹ over 300 cycles at 0.1 A g⁻¹) and outstanding rate capability (395 mAh g⁻¹ at 1 A g⁻¹ for 850 cycles), holding great promise for both scientific research and real application.     

Regulating Electrochemical Kinetics of CoP by Incorporating Oxygen on Surface for High-Performance Li–S Batteries

Lithium–sulfur (Li–S) batteries are widely studied because of their high theoretical specific capacity and environmental friendliness. However, the further development of Li–S batteries is hindered by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Since the adsorption and catalytic conversion of LiPSs mainly occur on the surface of the electrocatalyst, regulating the surface structure of electrocatalysts is an advisable strategy to solve the obstacles in Li–S batteries. Herein, CoP nanoparticles with high oxygen content on surface embedded in hollow carbon nanocages (C/O-CoP) is employed to functionalize the separators and the effect of the surface oxygen content of CoP on the electrochemical performance is systematically explored. Increasing the oxygen content on CoP surface can enhance the chemical adsorption to lithium polysulfides and accelerate the redox conversions kinetics of polysulfides. The cell with C/O-CoP modified separator can achieve the capacity of 1033 mAh g⁻¹ and maintain 749 mAh g⁻¹ after 200 cycles at 2 C. Moreover, DFT calculations are used to reveal the enhancement mechanism of oxygen content on surface of CoP in Li–S chemistry. This work offers a new insight into developing high-performance Li–S batteries from the perspective of surface engineering.     

Remedies for Polysulfide Dissolution in Room-Temperature Sodium–Sulfur Batteries

Rechargeable room-temperature sodium–sulfur (RT-NaS) batteries represent one of the most attractive technologies for future stationary energy storage due to their high energy density and low cost. The S cathodes can react with Na ions via two-electron conversion reactions, thus achieving ultrahigh theoretical capacity (1672 mAh g⁻¹) and specific energy (1273 Wh kg⁻¹). Unfortunately, the sluggish reaction kinetics of the nonconductive S, severe polysulfide dissolution, and the use of metallic Na are causing enormous challenges for the development of RT-NaS batteries. Fatal polysulfide dissolution is highlighted, important studies toward polysulfide immobilization and conversion are presented, and the reported remedies in terms of intact physical confinement, strong chemical interaction, blocking layers, and optimization of electrolytes are summarized. Future research directions toward practical RT-NaS batteries are summarized.     

High-Performance,Long-Life,Rechargeable Li–CO2 Batteries based on a 3D Holey Graphene Cathode Implanted with Single Iron Atoms

A highly efficient cathode catalyst for rechargeable Li–CO₂ batteries is successfully synthesized by implanting single iron atoms into 3D porous carbon architectures, consisting of interconnected N,S-codoped holey graphene (HG) sheets. The unique porous 3D hierarchical architecture of the catalyst with a large surface area and sufficient space within the interconnected HG framework can not only facilitate electron transport and CO₂/Li⁺ diffusion, but also allow for a high uptake of Li₂CO₃ to ensure a high capacity. Consequently, the resultant rechargeable Li–CO₂ batteries exhibit a low potential gap of ≈1.17 V at 100 mA g⁻¹ and can be repeatedly charged and discharged for over 200 cycles with a cut-off capacity of 1000 mAh g⁻¹ at a high current density of 1 A g⁻¹. Density functional theory calculations are performed and the observed appealing catalytic performance is correlated with the hierarchical structure of the carbon catalyst. This work provides an effective approach to the development of highly efficient cathode catalysts for metal–CO₂ batteries and beyond.     

Bidirectional Catalysts for Liquid–Solid Redox Conversion in Lithium–Sulfur Batteries

Accelerated conversion by catalysis is a promising way to inhibit shuttling of soluble polysulfides in lithium–sulfur (Li–S) batteries, but most of the reported catalysts work only for one direction sulfur reaction (reduction or oxidation), which is still not a root solution since fast cycled use of sulfur species is not finally realized. A bidirectional catalyst design, oxide–sulfide heterostructure, is proposed to accelerate both reduction of soluble polysulfides and oxidation of insoluble discharge products (e.g., Li₂S), indicating a fundamental way for improving both the cycling stability and sulfur utilization. Typically, a TiO₂–Ni₃S₂ heterostructure is prepared by in situ growing TiO₂ nanoparticles on Ni₃S₂ surface and the intimately bonded interfaces are the key for bidirectional catalysis. For reduction, TiO₂ traps while Ni₃S₂ catalytically converts polysulfides. For oxidation, TiO₂ and Ni₃S₂ both show catalytic activity for Li₂S dissolution, refreshing the catalyst surface. The produced sulfur cathode with TiO₂–Ni₃S₂ delivers a low capacity decay of 0.038% per cycle for 900 cycles at 0.5C and specially, with a sulfur loading of 3.9 mg cm⁻², achieves a high capacity retention of 65% over 500 cycles at 0.3C. This work unlocks how a bidirectional catalyst works for boosting Li–S batteries approaching practical uses.     

Paramagnetic Meissner Effect and AC Magnetization in Roll-Bonded Cu–Nb Layered Composites

The paramagnetic Meissner effect (PME) is related to the appearance of a positive magnetization when a superconducting specimen is field cooled through its critical temperature. In this work we report on the PME and ac magnetization in roll-bonded Cu–Nb (RB/Cu–Nb) layered composites. We present typical DC magnetization loops obtained in the normal magnetic field configuration that show the PME. In addition, we present ac magnetization measurements that reveal a crossover behavior at a characteristic field value. We show evidence that such a crossover behavior, attributed to activation processes of vortices, is probably related to the disappearance of the PME in the RB/Cu–Nb layered composites.     

MOF-Derived Mn2O3 Nanocage with Oxygen Vacancies as Efficient Cathode Catalysts for Li–O2 Batteries

Designing efficient and cost-effective electrocatalysts is the primary imperative for addressing the pivotal concerns confronting lithium–oxygen batteries (LOBs). The microstructure of the catalyst is one of the key factors that influence the catalytic performance. This study proceeds to the advantage of metal-organic frameworks (MOFs) derivatives by annealing manganese 1,2,3-triazolate (MET-2) at different temperatures to optimize Mn₂O₃ crystals for special microstructures. It is found that at 350 °C annealing temperature, the derived Mn₂O₃ nanocage maintains the structure of MOF, the inherited high porosity and large specific surface area provide more channels for Li⁺ and O₂ diffusion, beside the oxygen vacancies on the surface of Mn₂O₃ nanocages enhance the electrocatalytic activity. With the synergy of unique structure and rich oxygen vacancies, the Mn₂O₃ nanocage exhibits ultrahigh discharge capacity (21 070.6 mAh g⁻¹ at 500 mA g⁻¹) and excellent cycling stability (180 cycles at the limited capacity of 600 mAh g⁻¹ with a current of 500 mA g⁻¹). This study demonstrates that the Mn₂O₃ nanocage structure containing oxygen vacancies can significantly enhance catalytic performance for LOBs, which provide a simple method for structurally designed transition metal oxide electrocatalysts.     

Oxygen?Defect Enhanced Anion Adsorption Energy Toward Super?Rate and Durable Cathode for Ni–Zn Batteries

The alkaline zinc-based batteries with high energy density are becoming a research hotspot. However, the poor cycle stability and low-rate performance limit the...