Rechargeable Aluminium–Sulfur Battery with Improved Electrochemical Performance by Cobalt-Containing Electrocatalyst

The rechargeable aluminium–sulfur (Al–S) battery is regarded as a potential alternative beyond lithium-ion battery system owing to its safety, promising energy density, and the high earth abundance of the constituent electrode materials, however, sluggish kinetic response and short life-span are the major issues that limit the battery development towards applications. In this article, we report Co^II,III as an electrochemical catalyst in the sulfur cathode that renders a reduced discharge–charge voltage hysteresis and improved capacity retention and rate capability for Al–S batteries. The structural and electrochemical analysis suggest that the catalytic effect of Co^II,III is closely associated with the formation of cobalt sulfides and the changes in the valence states of the Co^II,III during the electrochemical reactions of the sulfur species, which lead to improved reaction kinetics and sulfur utilization in the cathode. The Al–S battery, assembled with the cathode consisting of Co^II,III decorated carbon matrix, demonstrates a considerably reduced voltage hysteresis of 0.8 V, a reversible specific capacity of ≈500 mAh g⁻¹ at 1 A g⁻¹ after 200 discharge–charge cycles and of ≈300 mAh g⁻¹ at 3 A g⁻¹.     

A Long-Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.     

High-Voltage Rechargeable Alkali–Acid Zn–PbO2 Hybrid Battery

Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23 V) of water leads to their failure in competition with organic-based lithium-ion batteries. Herein, we report an alkali–acid Zn–PbO₂ hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO₂ cathode. It shows the capability to deliver an impressively high open-circuit voltage (V_oc) of 3.09 V and an operate voltage of 2.95 V at 5 mA cm⁻², thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali–acid asymmetric-electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2 mAh cm⁻² or a high energy density of 252.39 Wh kg⁻¹ and shows almost no fading in area capacity over 250 charge–discharge cycles.     

Synergistic Fe−Se Atom Pairs as Bifunctional Oxygen Electrocatalysts Boost Low-Temperature Rechargeable Zn-Air Battery

Herein, we successfully construct bifunctional electrocatalysts by synthesizing atomically dispersed Fe−Se atom pairs supported on N-doped carbon (Fe−Se/NC). The obtained Fe−Se/NC shows a noteworthy bifunctional oxygen catalytic performance with a low potential difference of 0.698 V, far superior to that of reported Fe-based single-atom catalysts. The theoretical calculations reveal that p-d orbital hybridization around the Fe−Se atom pairs leads to remarkably asymmetrical polarized charge distributions. Fe−Se/NC based solid-state rechargeable Zn-air batteries (ZABs−Fe−Se/NC) present stable charge/discharge of 200 h (1090 cycles) at 20 mA cm⁻² at 25 °C, which is 6.9 times of ZABs−Pt/C+Ir/C. At extremely low temperature of −40 °C, ZABs−Fe−Se/NC displays an ultra-robust cycling performance of 741 h (4041 cycles) at 1 mA cm⁻², which is about 11.7 times of ZABs−Pt/C+Ir/C. More importantly, ZABs−Fe−Se/NC could be operated for 133 h (725 cycles) even at 5 mA cm⁻² at −40 °C.     

Proton Insertion Chemistry of a Zinc–Organic Battery

Proton storage in rechargeable aqueous zinc-ion batteries (ZIBs) is attracting extensive attention owing to the fast kinetics of H⁺ insertion/extraction. However, it has not been achieved in organic materials-based ZIBs with a mild electrolyte. Now, aqueous ZIBs based on diquinoxalino [2,3-a:2′,3′-c] phenazine (HATN) in a mild electrolyte are developed. Electrochemical and structural analysis confirm for the first time that such Zn–HATN batteries experience a H⁺ uptake/removal behavior with highly reversible structural evolution of HATN. The H⁺ uptake/removal endows the Zn–HATN batteries with enhanced electrochemical performance. Proton insertion chemistry will broaden the horizons of aqueous Zn–organic batteries and open up new opportunities to construct high-performance ZIBs.     

Starch-Based Superabsorbent Hydrogel with High Electrolyte Retention Capability and Synergistic Interface Engineering for Long-Lifespan Flexible Zinc−Air Batteries

The advent of wearable electronics has strongly stimulated advanced research into the exploration of flexible zinc−air batteries (ZABs) with high theoretical energy density, high inherent safety, and low cost. However, the half-open battery structure and the high concentration of alkaline aqueous environment pose great challenges on the electrolyte retention capability and the zinc anode stability. Herein, a starch-based superabsorbent hydrogel polymer electrolyte (SSHPE) with high ionic conductivity, electrolyte absorption and retention capabilities, strong alkaline resistance and high zinc anode stability has been designed and applied in ZABs. Experimental and calculational analyses probe into the root of the superiority of SSHPEs, confirming the significance of the carboxyl functional groups along their polymer chains. These features endow the as-fabricated ZAB a long cycle life of 300 h, much longer than that with commonly used poly(vinyl alcohol)-based electrolyte.     

Zinc–Organic Battery with a Wide Operation-Temperature Window from −70 to 150 °C

Aqueous zinc (Zn) batteries have been considered as promising candidates for grid-scale energy storage. However, their cycle stability is generally limited by the structure collapse of cathode materials and dendrite formation coupled with undesired hydrogen evolution on the Zn anode. Herein we propose a zinc–organic battery with a phenanthrenequinone macrocyclic trimer (PQ-MCT) cathode, a zinc-foil anode, and a non-aqueous electrolyte of a N,N-dimethylformamide (DMF) solution containing Zn²⁺. The non-aqueous nature of the system and the formation of a Zn²⁺–DMF complex can efficiently eliminate undesired hydrogen evolution and dendrite growth on the Zn anode, respectively. Furthermore, the organic cathode can store Zn²⁺ ions through a reversible coordination reaction with fast kinetics. Therefore, this battery can be cycled 20 000 times with negligible capacity fading. Surprisingly, this battery can even be operated in a wide temperature range from −70 to 150 °C.     

Zeolitic Imidazolate Frameworks Derived Co9S8/Nitrogen-Doped Hollow Porous Carbon Spheres as Efficient Bifunctional Electrocatalysts for Rechargeable Zinc–Air Batteries

The development of nonprecious metal-based electrocatalysts with remarkable catalytic activity and long-cycling lifespan toward oxygen reduction reaction (ORR) and evolution reaction (OER) is especially important for rechargeable zinc–air batteries (ZABs). Herein, monodispersed Co₉S₈ nanoparticles embedded in nitrogen-doped hierarchically porous hollow carbon spheres (Co₉S₈ NPs/NHCS) are synthesized through a template-assisted strategy followed by a co-assembly, thermal annealing, and sulfurization process. Benefiting from larger specific surface area, hierarchically porous hollow structure, and carbon nanotubes self-growth, the obtained Co₉S₈ NPs/NHCS-0.5 electrocatalyst exhibits decent performance for ORR (E_1/2=0.85 V) and OER (E₁₀=1.55 V). A rechargeable ZAB assembled using the Co₉S₈ NPs/NHCS-0.5 as air cathode delivers a maximum power density of 116 mW cm⁻², high open circuit voltage of 1.47 V, and good durability (no obvious voltage decay after 1200 cycles (200 hours)). Such a hierarchically porous hollow structure of Co₉S₈ NPs/NHCS-0.5 provides a confined space shell and an interconnected hollow core to achieve outstanding bifunctional catalytic activity and cycling stability, which surpass the benchmark Pt/C-RuO₂.     

Flexible inorganic–organic hybrids with dual inorganic components

Combining multiple inorganic components is an effective approach to improve the mechanical properties of inorganic–organic hybrid materials. The inorganic components can form interactions with the organic polymer matrix, and there is thus a need to understand the reinforcement mechanism under the optimal combination of organic polymer and inorganic particles. In this work, we prepared a series of dual inorganic particle–based titania/silica–poly(tetrahydrofuran)–poly(ε-caprolactone) (TiO₂/SiO₂–PTHF–PCL) hybrids by means of simultaneous cationic ring-opening polymerization and sol–gel reaction. In addition to constructing hybrid networks, the SiO₂ and TiO₂ components play important roles in multiple toughening mechanisms. The prepared dual inorganic hybrids feature enhanced thermal stability and mechanical properties when compared with the ones with a single inorganic component. The optimized mixing of such two inorganic components is identified through mechanical tests, revealing that the hybrid polymer₇₀/(Si_0.6Ti_0.4)₃₀ (70/18/12 mass ratio) has the highest compressive failure strain (80%) and compressive ultimate strength (1.3 MPa) as well as storage modulus (120 kPa), enabling elongation of up to 37% when compared with its original length. We thus find that the dual inorganic component approach is an effective strategy to enhance the mechanical properties of hybrid materials, suggesting potential applications as scaffolds for tissue engineering and soft robotics.     

High Performance Bifunctional Electrocatalysts Designed Based on Transition-Metal Sulfides for Rechargeable Zn–Air Batteries

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people‘s attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high-efficiency and low-cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition-metal sulfides (TMS) providing ideas for us to rationally design high-performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected.     

Photo-excited Oxygen Reduction and Oxygen Evolution Reactions Enable a High-Performance Zn–Air Battery

The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn–air battery is constructed with two cathodes of poly(1,4-di(2-thienyl))benzene (PDTB) and TiO₂ grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO₂ cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record-high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo-involved Zn–air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo-energy utilization in rechargeable batteries.     

A “Pre-Division Metal Clusters” Strategy to Mediate Efficient Dual-Active Sites ORR Catalyst for Ultralong Rechargeable Zn-Air Battery

To conquer the bottleneck of sluggish kinetics in cathodic oxygen reduction reaction (ORR) of metal-air batteries, catalysts with dual-active centers have stood out. Here, a “pre-division metal clusters” strategy is firstly conceived to fabricate a N,S-dual doped honeycomb-like carbon matrix inlaid with CoN₄ sites and wrapped Co₂P nanoclusters as dual-active centers (Co₂P/CoN₄@NSC-500). A crystalline {Co^II ₂ } coordination cluster divided by periphery second organic layers is well-designed to realize delocalized dispersion before calcination. The optimal Co₂P/CoN₄@NSC-500 executes excellent 4e⁻ ORR activity surpassing the benchmark Pt/C. Theoretical calculation results reveal that the CoN₄ sites and Co₂P nanoclusters can synergistically quicken the formation of *OOH on Co sites. The rechargeable Zn-air battery (ZAB) assembled by Co₂P/CoN₄@NSC-500 delivers ultralong cycling stability over 1742 hours (3484 cycles) under 5 mA cm⁻² and can light up a 2.4 V LED bulb for ≈264 hours, evidencing the promising practical application potentials in portable devices.     

Ionic Liquid Stabilized Gelatin–Lignin Films: A Potential UV-Shielding Material with Excellent Mechanical and Antimicrobial Properties

Significant research is currently underway to develop environmentally friendly UV-shielding materials. Herein, we have constructed choline citrate (a biobased ionic liquid, IL) stabilized homogeneous gelatin–lignin UV-shielding films with excellent antimicrobial and mechanical properties. The synthesis procedure of the films is less energy demanding, one pot, and sustainable in nature. Prepared films were characterized by mechanical and thermal analysis using UTM and TGA, respectively. ATR-IR and PXRD was employed to explore the possible formation of H-bonding between biopolymers and the IL and the change in crystallinity in films after addition of IL to the gelatin–lignin matrix. Surface morphology of prepared films has been studied using optical microscope, AFM, and field emission SEM (FE-SEM). Optical properties of prepared films were measured using UV/Vis spectroscopy. Antimicrobial activity of the prepared films was tested against Bacillus subtilis. Prepared biofilms showed a sun-protection factor (SPF) of up to ≈45.0, large elongation ≈200 %, and tensile strength ≈70 MPa, which are as good as those values exhibited by organic polymeric films, indicating a promising renewable-resources-based material for UV light blocking.     

MnO/N-Doped Mesoporous Carbon as Advanced Oxygen Reduction Reaction Electrocatalyst for Zinc–Air Batteries

The development of alternative electrocatalysts exhibiting high activity in the oxygen reduction reaction (ORR) is vital for the deployment of large-scale clean energy devices, such as fuel cells and zinc–air batteries. N-doped carbon materials offer a promising platform for the design and synthesis of electrocatalysts due to their high ORR activity, high surface area, and tunable porosity. In this study, materials in which MnO nanoparticles are entrapped in N-doped mesoporous carbon (MnO/NC) were developed as electrocatalysts for the ORR, and their performances were evaluated in zinc–air batteries. The obtained carbon materials had large surface area and high electrocatalytic activity toward the ORR. The carbon compounds were fabricated by using NaCl as template in a one-pot process, which significantly simplifies the procedure for preparing mesoporous carbon materials and in turn reduces the total cost. A primary zinc–air battery based on this material exhibits an open-circuit voltage of 1.49 V, which is higher than that of conventional zinc–air batteries with Pt/C (Pt/C cell) as ORR catalyst (1.41 V). The assembled zinc–air battery delivered a peak power density of 168 mW cm⁻² at a current density of about 200 mA cm⁻², which is higher than that of an equivalent Pt/C cell (151 mW cm⁻² at a current density of ca. 200 mA cm⁻²). The electrocatalytic data revealed that MnO/NC is a promising nonprecious-metal ORR catalyst for practical applications in metal–air batteries.     

A Self-Healing Metal–Organic Hydrogel for an All-Solid Flexible Supercapacitor

A zinc containing metal–organic gel (Zn-MOG) with embedded free ions, which exhibits self-healing properties, has been synthesized for application in supercapacitors. The activated carbon-based flexible supercapacitor device with the MOG electrolyte has a broad potential window of 2.1 V, with high retention of specific capacitance compared to the traditional polyvinyl alcohol (PVA)-based gel. The Zn-MOG does not require an additional electrolyte. The sodium and sulphate ions embedded in the MOG are sufficient enough for the charge storage.     

A Full Li–S Battery with Ultralow Excessive Li Enabled via Lithiophilic and Sulfilic W2C Modulation

The practical application of Li–S batteries demands low cell balance (Li_capacity/S_capacity), which involves uniform Li growth, restrained shuttle effect, and fast redox reaction kinetics of S species simultaneously. Herein, with the aid of W₂C nanocrystals, a freestanding 3D current collector is applied as both Li and S hosts owing to its lithiophilic and sulfilic property. On the one hand, the highly conductive W₂C can reduce Li nucleation overpotentials, thus guiding uniform Li nucleation and deposition to suppress Li dendrite growth. On the other hand, the polar W₂C with catalytic effect can enhance the chemisorption affinity to lithium polysulfides (LiPSs) and guarantee fast redox kinetics to restrain S species in cathode region and promote the utilization of S. Surprisingly, a full Li–S battery with ultralow cell balance of 1.5:1 and high sulfur loading of 6.06 mg cm⁻² shows obvious redox plateaus of S and maintains high reversible specific capacity of 1020 mAh g⁻¹ (6.2 mAh cm⁻²) after 200 cycles. This work may shed new sights on the facile design of full Li–S battery with low excessive Li supply.     

Styrene Hydroformylation with In Situ Hydrogen: Regioselectivity Control by Coupling with the Low-Temperature Water–Gas Shift Reaction

The hydroformylation of olefins is one of the most important homogeneously catalyzed industrial reactions for aldehyde synthesis. Various ligands can be used to obtain the desired linear aldehydes in the hydroformylation of aliphatic olefins. However, in the hydroformylation of aromatic substrates, branched aldehydes are formed preferentially with common ligands. In this study, a novel approach to selectively obtain linear aldehydes in the hydroformylation of styrene and its derivatives was developed by coupling with a water–gas shift reaction on a Rh single-atom catalyst without the use of ligands. Detailed studies revealed that the hydrogen generated in situ from the water–gas shift is critical for the highly regioselective formation of linear products. The coupling of a traditional homogeneous catalytic process with a heterogeneous catalytic reaction to tune product selectivity may provide a new avenue for the heterogenization of homogenous catalytic processes.     

Low-Temperature Adsorption–Luminescence Determination of Gold Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups covalently bonded to the surface extracts gold(III) from its hydrochloric solutions in a wide acidity range (from 6 M HCl to pH 8). An adsorption equilibrium is attained in no more than 5 min. The distribution ratio is 1.65 × 10⁴–1 × 10⁵ cm³/g. The intense yellow–orange luminescence (_max = 575 nm) appearing in the adsorbent phase under UV irradiation of wet liquid-nitrogen cooled adsorbates (77 K) is used for the low-temperature adsorption–luminescence determination of gold. The calibration plot is linear in the range of 1–100 g of gold per 0.1 g of adsorbent. The detection limit is 0.05 g/0.1 g of adsorbent. The relative standard deviation for the determination of more than 10 g of gold is no more than 5%.     

MOF-Mediated Fabrication of a Porous 3D Superstructure of Carbon Nanosheets Decorated with Ultrafine Cobalt Phosphide Nanoparticles for Efficient Electrocatalysis and Zinc–Air Batteries

Superstructures have attracted great interest owing to their potential applications. Herein, we report the first scalable preparation of a porous nickel-foam-templated superstructure of carbon nanosheets decorated with ultrafine cobalt phosphide nanoparticles. Uniform two-dimensional (2D) Co-metal organic framework (MOF) nanosheets (Co-MNS) grow on nickel foam, followed by a MOF-mediated tandem (carbonization/phosphidation) pyrolysis. The resulting superstructure has a porous 3D interconnected network with well-arranged 2D carbon nanosheets on it, in which ultrafine cobalt phosphide nanoparticles are tightly immobilized. A single piece of this superstructure can be directly used as a self-supported electrode for electrocatalysis without any binders. This “one-piece” porous superstructure with excellent mass transport and electron transport properties, and catalytically active cobalt phosphide nanoparticles with ultrasmall size (3–4 nm), shows excellent trifunctional electrocatalytic activities for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), achieving great performances in water splitting and Zn–air batteries.     

Zinc(II)–Organic Framework Films with Thermochromic and Solvatochromic Applications

Multiple-stimuli-responsive photoluminescence films based on a Zn^II–organic framework, {[Zn₂(Htpim)(3,4-pydc)₂] ⋅ 4 DMF ⋅ 4 H₂O}_n ( 1 , Htpim=2,4,5-tri(4-pyridyl)imidazole, 3,4-H₂pydc=3,4-pyridinedicarboxylic acid), were fabricated. This compound consisted of a 2D corrugated layer, {Zn(3,4-pydc)}_n, which was further pillared using a Y-shaped pillar N-donor ligand (Htpim) to form a 3D-pillared-layer framework with 1D open channels. The rectangular channels in the as-synthesized compound are fully occupied by guest DMF and H₂O molecules. The framework exhibits instant and reversible thermochromic properties corresponding to the removal of different H₂O and DMF guest molecules as temperature increases. The pale-yellow crystal undergoes significant redshifting to a greenish emission centered at 530 nm. Compound 1 also showed remarkable solvatochromic effects in the presence of various organic solvents without affecting its structural integrity. In addition, polycrystalline MOF films were grown on an α-Al₂O₃ support for switchable and fast-response thermochromic and solvatochromic sensors.