Search

The high energy density and cost‐effectiveness of chloride‐ion batteries (CIBs) make them promising alternatives to lithium‐ion batteries. However, the development of CIBs is greatly restricted by the lack of compatible electrolytes to support cost‐effective anodes. Herein, we present a rationally designed solid polycationic electrolyte (SPE) to enable room‐temperature chloride‐ion batteries utilizing aluminum (Al) metal as an anode. This SPE endows the CIB configuration with improved air stability and safety (i.e. free of flammability and liquid leakage). A high ionic conductivity (1.3×10−2 S cm−1 at 25 °C) has been achieved by the well‐tailored coordination structure of the SPE. Meanwhile, the solid polycationic electrolyte ensures stable electrodes|electrolyte interfaces, which effectively inhibit the growth of dendrites on the Al anodes and degradation of the FeOCl cathodes. The Al|SPE|FeOCl chloride‐ion batteries showcased a high discharge capacity around 250 mAh g−1 (based on the cathodes) and extended lifespan. Our electrolyte design opens a new avenue for developing low‐cost chloride‐ion batteries. [ABSTRACT FROM AUTHOR]

The high energy density and cost‐effectiveness of chloride‐ion batteries (CIBs) make them promising alternatives to lithium‐ion batteries. However, the development of CIBs is greatly restricted by the lack of compatible electrolytes to support cost‐effective anodes. Herein, we present a rationally designed solid polycationic electrolyte (SPE) to enable room‐temperature chloride‐ion batteries utilizing aluminum (Al) metal as an anode. This SPE endows the CIB configuration with improved air stability and safety (i.e. free of flammability and liquid leakage). A high ionic conductivity (1.3×10−2 S cm−1 at 25 °C) has been achieved by the well‐tailored coordination structure of the SPE. Meanwhile, the solid polycationic electrolyte ensures stable electrodes|electrolyte interfaces, which effectively inhibit the growth of dendrites on the Al anodes and degradation of the FeOCl cathodes. The Al|SPE|FeOCl chloride‐ion batteries showcased a high discharge capacity around 250 mAh g−1 (based on the cathodes) and extended lifespan. Our electrolyte design opens a new avenue for developing low‐cost chloride‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur (Li−S) batteries are one of the most potential new energy storage systems due to their high theoretical capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, the application of Li−S batteries is currently restricted due to the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect of lithium polysulfides (LiPSs). Here, we present a Co@MXene‐derived TiO2 heterostructure decorated on carbon sheets derived from folic acid (Co@M‐TiO2/C) as a functional separator coating to trap polysulfide and accelerate redox kinetics in Li−S batteries. The interconnected porous structure with good electrical conductivity of the heterostructure boasts rapid ion diffusion and efficient electron transfer within the battery. By attaching Co and MXene‐derived dual‐phased TiO2 to two‐dimensional carbon sheets, heterostructures are formed, ensuring complete exposure of the active sites. These heterostructures exhibit catalytic effects on LiPSs and excellent adsorption capabilities, effectively inhibiting the shuttle effect and accelerating the redox kinetics. Considering these advantages, the Li−S battery with the optimized Co@M‐TiO2/C modified separator demonstrates a high specific capacity of 1481.7 mAh g−1 at 0.2 C, superior rate performance of 855.5 mAh g−1 at 2 C, and excellent cycling performance under a high sulfur load of 4.4 mg cm−2. [ABSTRACT FROM AUTHOR]

Sodium (Na) metal anodes are promising candidates for various batteries with high energy density and high‐power density, however, the dendrite growth of Na metal is impeding their practical applications. The binary alloy Na–K is in the liquid state at room temperature with a wide composition range, which renders it inherently free from solid dendrite growth. Whereas the application of Na–K alloy is plagued by the lack of a wettable matrix to immobilize the liquid metal. Herein, a facile method is reported to introduce oxygen‐rich functional groups into carbon fiber cloth (O‐CFC), which is initially Na–K phobic yet turns into superwetting after the treatment. The superwetting behavior of the O‐CFC can be attributed to the favorable enthalpy changes as a result of the introduction of O‐rich functional groups. The superwetting property of the O‐CFC exhibits good universality, which can be extended to melting Na and K metals. By adopting the superwetting O‐CFC as a host for liquid Na–K alloy, the liquid metal can be well retained in the matrix and deliver a stable cycling for >1600 h. The concept of enthalpy‐driven wettability regulation can be enlightening for the host material design of other liquid metals and alloys. [ABSTRACT FROM AUTHOR]

Room temperature sodium sulfur (RT Na‐S) batteries with high theoretical energy density and low cost have recently gained extensive attention for potential large‐scale energy storage applications. However, the shuttle effect of sodium polysulfides is still the main challenge that leads to poor cycling stability, which hinders the practical application of RT Na‐S batteries. Herein, a multifunctional hybrid MXene interlayer is designed to stabilize the cycling performance of RT Na‐S batteries. The hybrid MXene interlayer comprises a large‐sized Ti3C2Tx nanosheets inner layer followed by a small‐sized Mo2Ti2C3Tx nanoflake outer layer on the surface of the glass fiber (GF) separator. The large‐sized Ti3C2Tx nanosheet inner layer provides an effective physical block and chemical confinement for the soluble polysulfides. The small‐sized Mo2Ti2C3Tx outer layer offers an excellent polysulfide trapping capability and accelerates the reaction kinetics of polysulfide conversion, due to its superior electronic conductivity, large specific surface area, and Mo‐rich catalytic surfaces. As a result, RT Na‐S batteries with this hybrid MXene interlayer modified glass fiber separator deliver a stable cycling performance over 200 cycles at 1 C with an enhanced capacity retention of 71%. This unique structure design provides a novel strategy to develop 2D material‐based functional interlayer for high‐performance metal‐sulfur batteries. [ABSTRACT FROM AUTHOR]

As the lightest metal, the reversible insertion/extraction properties of lithium have been key findings in lithium metal oxide chemistry. Lithium has been widely used in the oxygen evolution reaction (OER), and the reaction mechanism of lithium‐mediated metal oxides has both similarities and uniqueness compared to typical dual metal oxides. Notably, the insertion/extraction of lithium during the OER is also crucial for the construction of novel surface reconstruction models. This review aims to provide the concepts of general OER pathways and key features of dual metal oxides for the OER. As a comparison then the development of lithium metal oxides for the OER is introduced and the chemistry underlying lithium metal oxide catalysts is unveiled. This review also examines the challenges remaining for the relevant catalysts, with prospects for further improving their OER activities. [ABSTRACT FROM AUTHOR]

Sodium metal batteries are recognized as promising candidates for next‐generation energy storage devices, as a result of their high energy density, low redox potential, and cheap material price. Na metal anodes, however, generally exhibit notorious problems, including progressively thickened interfaces with active Na loss and Na metal dendrite growth with safety hazards. Herein, a lightweight aerogel consisting of MgF2 nanocrystals grown on a reduced graphene oxide (RGO) aerogel matrix (MgF2@RGO) is rationally designed as a multifunctional host material for Na metal anodes. The MgF2 nanocrystals can be electrochemically converted in situ into Mg and NaF nanograins during the first Na plating process, in which the Mg works as sodiophilic nucleation seeds for Na plating and NaF plays a key role in suppressing Na dendrite growth. Significantly, the Na metal anodes with the MgF2@RGO aerogel host deliver significantly enhanced Coulombic efficiency and dramatically improved cycling stability for more than 1600 h. The morphology evolution confirms the advantages of the Na metal anode with the MgF2@RGO host, which exhibits dense and flat interfaces. By pairing with the Na3V2(PO4)3 cathode, the Na metal batteries achieve stable cycling and good rate capability, suggesting the potential of the Na/MgF2@RGO anode for practical applications. [ABSTRACT FROM AUTHOR]

It is vital to dynamically regulate S activity to achieve efficient and stable room‐temperature sodium–sulfur (RT/Na−S) batteries. Herein, we report using cobalt sulfide as an electron reservoir to enhance the activity of sulfur cathodes, and simultaneously combining with cobalt single atoms as double‐end binding sites for a stable S conversion process. The rationally constructed CoS2 electron reservoir enables the straight reduction of S to short‐chain sodium polysulfides (Na2S4) via a streamlined redox path through electron transfer. Meanwhile, cobalt single atoms synergistically work with the electron reservoir to reinforce the streamlined redox path, which immobilize in situ formed long‐chain products and catalyze their conversion, thus realizing high S utilization and sustainable cycling stability. The as‐developed sulfur cathodes exhibit a superior rate performance of 443 mAh g−1 at 5 A g−1 with a high cycling capacity retention of 80 % after 5000 cycles at 5 A g−1. [ABSTRACT FROM AUTHOR]

It is vital to dynamically regulate S activity to achieve efficient and stable room‐temperature sodium–sulfur (RT/Na−S) batteries. Herein, we report using cobalt sulfide as an electron reservoir to enhance the activity of sulfur cathodes, and simultaneously combining with cobalt single atoms as double‐end binding sites for a stable S conversion process. The rationally constructed CoS2 electron reservoir enables the straight reduction of S to short‐chain sodium polysulfides (Na2S4) via a streamlined redox path through electron transfer. Meanwhile, cobalt single atoms synergistically work with the electron reservoir to reinforce the streamlined redox path, which immobilize in situ formed long‐chain products and catalyze their conversion, thus realizing high S utilization and sustainable cycling stability. The as‐developed sulfur cathodes exhibit a superior rate performance of 443 mAh g−1 at 5 A g−1 with a high cycling capacity retention of 80 % after 5000 cycles at 5 A g−1. [ABSTRACT FROM AUTHOR]

Sodium and sulfur offer a promising application in rechargeable batteries due to their low cost, abundant resources and high energy density. Room‐temperature (RT) Na–S batteries have been proposed by paring S cathodes with Na anodes in non‐aqueous liquid electrolytes. Over decades, researchers have mainly focussed on the development of superior electrodes by nano‐engineering efficient S cathodes and stable Na anodes. These studies have effectively improved the electrochemical performance of RT Na–S batteries, validating their bright prospects as stationary energy storage devices for the modern renewable energy trajectory. In comparison, the research on electrolytes receives much less attention, and there is a lack of understanding regarding the impacts of different electrolytes on electrode interfaces and overall battery mechanisms. In this review, multiple‐kinds of electrolytes and the interfaces between electrolytes and electrodes in RT Na–S batteries are comprehensively discussed. Challenges and recent progress are presented in terms of the sulfur electrochemical mechanisms: The solid‐solid and solid‐liquid conversions. With the presentation of the S redox mechanism, future prospects of electrolyte optimizations, cathode, and anode as well as interfacial improvement are systematically discussed. [ABSTRACT FROM AUTHOR]

Room‐temperature sodium–sulfur (RT Na–S) batteries have attracted extensive attention because of their low cost and high specific energy. RT Na–S batteries, however, usually suffer from sluggish reaction kinetics, low reversible capacity, and short lifespans. Herein, it is shown that chain‐mail catalysts, consisting of porous nitrogen doped carbon nanofibers (PCNFs) encapsulating Co nanoparticles (Co@PCNFs), can activate sulfur via electron engineering. The chain‐mail catalysts Co@PCNFs with a micrograde hierarchical structure as a freestanding sulfur cathode (Co@PCNFs/S) can provide space for high mass loading of sulfur and polysulfides. The electrons can rapidly transfer from chain‐mail catalysts to sulfur and polysulfides during discharge–charge processes, therefore boosting its conversion kinetics. As a result, this freestanding Co@PCNFs/S cathode achieves a high sulfur loading of 2.1 ± 0.2 mg cm−2, delivering a high reversible capacity of 398 mA h g−1 at 0.5 C (1 C = 1675 mA g−1) over 600 cycles and superior rate capability of an average capacity of 240 mA h g−1 at 5 C. Experimental results, combined with density functional theory calculations, demonstrate that the Co@PCNFs/S can efficiently improve the conversion kinetics between the polysulfides and Na2S via transferring electrons from Co to them, thereby realizing efficient sulfur redox reactions. [ABSTRACT FROM AUTHOR]

Vacancies created on a surface can alter the local electronic structure, thus enabling a higher intrinsic activity for the evolution of hydrogen and oxygen. Conventional strategies for vacancy engineering, however, have a strong focus on non‐metal sulfur/oxygen defects, which have often overlooked metallic vacancies. Herein, evidence is provided that cobalt vacancies can be atomically tuned to have different sizes to achieve cobalt vacancy clusters through controlling the migration of iridium single atoms. The coalescence of Co vacancy clusters at the surface of an IrCo alloy results in an increased d‐band level and eventually compromises H adsorption, leading to enhanced electrocatalytic activity toward the hydrogen evolution reaction. In addition, the Co vacancy clusters can improve the electronic conductivity with respect to the oxidized Co surface, which substantially aids in strengthening the adsorption of oxygen intermediates toward an effective oxygen evolution reaction at a low overpotential. These collective effects originate from the Co vacancy cluster and specifically enable highly efficient and stable water splitting with a low total overpotential of 384 mV in alkaline media and 365 mV in an acidic environment, achieving a current density of 10 mA cm–2. [ABSTRACT FROM AUTHOR]

Highlights: A ‘solid–liquid’ conversion for increasing the sulfur content from ~ 50 to 72% for RT Na–S batteries is developed. The redox mechanisms of two types of sulfur: sulfur on the surface of a cathode host (155S) and sulfur in the pores of the host (300S) in ether and carbonate ester electrolytes are studied. The function of NaNO3 additive on modifying Na anode and confining the shuttle effect of dissolving polysulfides during ‘solid–liquid’ conversion is visualized.This work reports influence of two different electrolytes, carbonate ester and ether electrolytes, on the sulfur redox reactions in room-temperature Na–S batteries. Two sulfur cathodes with different S loading ratio and status are investigated. A sulfur-rich composite with most sulfur dispersed on the surface of a carbon host can realize a high loading ratio (72% S). In contrast, a confined sulfur sample can encapsulate S into the pores of the carbon host with a low loading ratio (44% S). In carbonate ester electrolyte, only the sulfur trapped in porous structures is active via ‘solid–solid’ behavior during cycling. The S cathode with high surface sulfur shows poor reversible capacity because of the severe side reactions between the surface polysulfides and the carbonate ester solvents. To improve the capacity of the sulfur-rich cathode, ether electrolyte with NaNO3 additive is explored to realize a ‘solid–liquid’ sulfur redox process and confine the shuttle effect of the dissolved polysulfides. As a result, the sulfur-rich cathode achieved high reversible capacity (483 mAh g−1), corresponding to a specific energy of 362 Wh kg−1 after 200 cycles, shedding light on the use of ether electrolyte for high-loading sulfur cathode. [ABSTRACT FROM AUTHOR]

The nickel phosphide (Ni2P) family of materials have become a hot subject in hydrogen evolution reaction (HER) electrocatalyst research. Various studies have reported their high activity, high stability, and high faradaic efficiency. To date, there have been no systematic studies regarding the influence of pH on the HER performance of Ni2P. Here we show that the pH of electrolytes can strongly influence the HER activity of Ni2P electrocatalysts. Tests in 19 electrolytes with pH ranging from 0.52 to 13.53 show that Ni2P is much more active in strongly acidic and basic electrolytes. With the increase of pH, the lower H+ concentration reduces the formation of adsorbed H atoms in the Volmer reaction, resulting in poorer activities. However, the high activity observed in the strongly basic electrolytes is not the intrinsic property of Ni2P. We found that Ni oxides/hydroxides are formed in strongly basic electrolytes under applied potentials, resulting in improved activities. Furthermore, the specific activity based on the electrochemically active surface area of recently reported Ni2P catalysts is not high and requires significant improvements for practical applications. [ABSTRACT FROM AUTHOR]

An efficient catalyst for selective oxidation of alcohols was prepared by grafting the Cu(II) Schiff base complex onto the channels of mesoporous silica material SBA-15. The characterizations illustrated that the functionalized SBA-15 maintained the primary hexagonally ordered mesoporous structure, and the Cu(II) Schiff base complexes were bonded inside the mesoporous channels of SBA-15. The selective oxidation of benzyl alcohol was carried out in water phase with hydrogen peroxide. The CHCHOH conversion could reach 98.5 % with 100 % of the selectivity to CHCHO under the optimum conditions. The catalyst could also react well on the selective oxidation of other primary alcohols. [ABSTRACT FROM AUTHOR]