Search

The practical application of lithium–sulfur (Li–S) batteries has been handicapped by the notorious polysulfide shuttling and sluggish sulfur conversion kinetics. Although the functional modification of separator is readily proposed as an effective strategy to optimize the Li–S redox reactions, the excessive material dosage and invalid structural design still result in inferior electrocatalyst utilization. Herein, generic graphene‐metal selenide heterostructures (Gr‐MxSey, M = Mo, W, Mn, Cu and Zn) are controllably grown on commercial glass fiber (GF) separator employing a sequential low‐temperature chemical vapor deposition procedure. Such a tailored reservoir can not only render ample active sites but also realize the synergy of polar and catalytic framework, which maximizes the electrochemical functions in alleviating shuttle effect and guiding Li2S nucleation/decomposition. The thus‐derived Gr‐MxSey/GF separator affording favorable heatproof feature endows the Li–S battery with an outstanding cycling stability (100% capacity retention over 100 cycles at 0.2 C). Furthermore, the flexible Li–S pouch cell based on this new separator delivers good device performance (with a capacity decay of 0.25% per cycle over 100 cycles). This study offers comprehensive insight into the reliable separator design toward working Li–S batteries. [ABSTRACT FROM AUTHOR]

Direct synthesis of large‐area graphene on functional substrates via chemical vapor deposition has become a frontier research stream targeting practical applications. However, the batch production of transfer‐free graphene film with favorable quality and homogeneity remains a grand challenge. Herein, the direct growth of 12‐inch‐sized graphene is demonstrated over fused quartz in a batch manner. The key design of the synthetic route is the construction of a nano‐scale compartment to allow the formation of free molecular flow during growth, as well as to trap the hydroxyl species in situ released from the quartz substrates. Density functional theory calculations reveal that the hydroxyl species help decrease the energy barrier for feedstock decomposition and facilitate the carbon attachment to boost graphene growth. Thus‐prepared graphene possesses excellent optical transmittance (96% ± 1%) and electrical properties (1.22 ± 0.08 kΩ sq‒1). These findings unlock new opportunities for achieving batch production of graphene‐skinned functional materials with practical scalability and quality toward emerging uses. [ABSTRACT FROM AUTHOR]

Separator modification has recently blossomed as an effective strategy to enable dendrite‐free Zn metal anodes. Nonetheless, the explored avenues are not conducive to mass production by far, and little attention is paid to the essence of separator regulation. Herein, a scalable Ti3C2Tx MXene‐decorated Janus separator is designed by spray‐printing MXene nanosheets over one side of commercial glass fibre (GF). The thus‐derived MXene‐GF separator affords abundant surface polar groups, good electrolyte wettability, and high ionic conductivity, which is beneficial to homogenizing local current distribution and promoting Zn nucleation kinetics. It is noted that MXene‐GF displays adjustable dielectric constants with an optimized value of 53.5, offering a directional electrical field to expedite Zn‐ion flux and repel anions. Accordingly, dendrite‐free Zn anode equipped within symmetric cells can be achieved with MXene‐GF, enabling a stable cycling for 1180 h at 1 mA cm−2 and 1200 h at 5 mA cm−2. More impressively, the assembled aqueous Zn‐ion battery full cell with Janus MXene‐GF separator realizes a favorable capacity retention ratio (77.9%) upon cycling for 1000 cycles at 5.0 A g−1. This strategy with scalability and effectiveness offers a new insight into high‐performance metal anodes. [ABSTRACT FROM AUTHOR]

The heteroatom co‐doped carbonaceous anodes have readily attracted great attention in potassium‐ion batteries (PIBs), owing to their augmented carbon interlayer distances and increased K+ storage sites to induce enhanced capacity value. Nevertheless, the synergistic effect of dual‐doped heteroatoms is still unclear and lacks systematic explorations. In addition, traditional synthetic routes are cumbersome with template removal step, which are normally deficient in product scalability. Herein, a generic protic‐salt strategy is devised to realize sulfur‐, phosphorus‐ or boron‐nitrogen dual‐doped carbon (SNC, PNC, or BNC) via varying the types of protic precursors (e.g., the acid). Throughout comprehensive instrumental probing and theoretical simulation, it is identified that the presence of B–N moiety can harvest high adsorption capability of K+ and hence exhibit more obvious pseudo‐capacitance behavior than bare N‐doped carbon counterpart. As a PIB anode, the BNC electrode displays an impressive reversible capacity (360.5 mAh g−1 at 0.1 A g−1) and cycle stability (125.4 mAh g−1 at 1 A g−1 after 3000 cycles). In situ/ex situ characterizations further reveal the origin of the excellent electrochemical properties of the BNC electrode. Such a tailorable protic‐salt derived anode material offers new possibilities to advance PIB devices. [ABSTRACT FROM AUTHOR]

Sn4P3 binary alloy anode has attracted much attention, not only because of the synergistic effect of P and Sn, but also its universal popularity in alkali metal ion batteries (AIBs), including lithium‐ion batteries (LIBs), sodium‐ion batteries (SIBs), and potassium‐ion batteries (PIBs). However, the alkali metal ion (A+) storage and capacity attenuation mechanism of Sn4P3 anodes in AIBs are not well understood. Herein, a combination of ex situ X‐ray diffraction, transmission electron microscopy, and density functional theory calculations reveals that the Sn4P3 anode undergoes segregation of Sn and P, followed by the intercalation of A+ in P and then in Sn. In addition, differential electrochemical curves and ex situ XPS results demonstrate that the deep insertion of A+ in P and Sn, especially in P, contributes to the reduction in capacity of AIBs. Serious sodium metal dendrite growth causes further reduction in the capacity of SIBs, while in PIBs it is the unstable solid electrolyte interphase and sluggish dynamics that lead to capacity decay. Not only the failure mechanism, including structural deterioration, unstable SEI, dendrite growth, and sluggish kinetics, but also the modification strategy and systematic analysis method provide theoretical guidance for the development of other alloy‐based anode materials. [ABSTRACT FROM AUTHOR]

Functionalizing carbon cathode surfaces with oxygen functional groups is an effective way to simultaneously tailor the fundamental properties and customize the electrochemical properties of aqueous Zn‐ion hybrid capacitors. In this work, the oxygen functional groups of chemically reduced graphene oxide (rGO) are systematically regulated via a series of reductants and varied experimental conductions. Carboxyl and carbonyl have been proven to significantly enhance the aqueous electrolyte wettability, Zn‐ion chemical adsorption, and pseudocapacitive redox activity by experimental study and computational analysis. The rGO cathode produced through hydrogen peroxide assisted hydrothermal reduction exhibits a specific capacitance of 277 F g−1 in 1 m ZnSO4 after optimization of surface oxygen functional groups. In addition, a quasi‐solid‐state flexible Zn‐ion hybrid capacitor (ZHC) with a polyacrylamide gel electrolyte and a high loading mass of 5.1 mg cm−2 are assembled. The as‐prepared quasi‐solid state ZHC can offer a superior areal capacitance of 1257 mF cm−2 and distinguished areal energy density of 342 µW h cm−2. The significant enhancement of redox activity and Zn‐ion storage capability by regulating the oxygen functional groups can shed light on the promotion of electrochemical charge storage properties even beyond protic electrolyte systems. [ABSTRACT FROM AUTHOR]

The rational design of electrocatalyst has readily stimulated a burgeoning interest in expediting polysulfide conversion and hence essentially restricting the "shuttle effect" in Li–S systems. Nevertheless, seldom efforts have been devoted to probing the dual‐directional polysulfide electrocatalysis to date. Herein, a CoFe alloy decorated mesoporous carbon sphere (CoFe‐MCS) serving as a promising mediator for Li–S batteries is reported. Such bimetallic alloying boosts dual‐directional electrocatalytic activity toward effective polysulfide conversion throughout detailed electroanalytic characterization, theoretical calculation, and operando instrumental probing. Accordingly, the S@CoFe‐MCS cathode harvests a stable cycling with a low capacity decay rate of 0.062% per cycle over 500 cycles at 2.0 C. More encouragingly, benefiting from the optimized redox kinetics and delicate grid architecture, printable S@CoFe‐MCS cathode achieves an excellent rate performance at a sulfur loading of 4.0 mg cm−2 and advanced areal capacity of 6.0 mAh cm−2 at 7.7 mg cm−2. This work explores non‐precious metal alloy electrocatalysts in printable cathodes toward dual‐directional polysulfide conversion, holding great potential in the pursuit of Li–S commercialization. [ABSTRACT FROM AUTHOR]

Electrolyte additive engineering is a feasible protocol in improving Zn anode stability. Typical additive designs center on the regulation of Zn deposition; nevertheless, versatile additives are urgently requested to comprehensively manage the surface landscape, interface physicochemistry, and by‐product elimination. Here, a straightforward strategy is presented to meet such needs employing an environmentally‐friendly chelator, hydroxyethyl‐ethylenediaminetriacetate acid (HEDTA), as an additive for ZnSO4 electrolyte. Throughout theoretical computations and experimental investigations, it is demonstrated that protons released from the gradual ionization of HEDTA during rest periods aid in the mild engraving of the Zn surface. Both the amino and carboxyl groups of HEDTA⁻ can be protonated, which effectively buffers the interfacial pH value in the entire battery lifespan and eliminates the formation of by‐products. The HEDTA− anions can also adsorb onto the Zn surface, helping facilitate Zn2⁺ mass transfer and accelerate the desolvation process. Benefiting from the synchronous modulation of surface topography and interfacial physicochemistry, the assembled half cells affording HEDTA additive maintain a durable operation of up to 8821 cycles at 5.0 mA cm−2/1.0 mAh cm−2. Additionally, symmetric cells manifest stable cycling for over 4600 h at 0.5 mA cm−2/0.25 mAh cm−2. [ABSTRACT FROM AUTHOR]

Potassium‐ion hybrid capacitors (KICs) reconciling the advantages of batteries and supercapacitors have stimulated growing attention for practical energy storage because of the high abundance and low cost of potassium sources. Nevertheless, daunting challenge remains for developing high‐performance potassium accommodation materials due to the large radius of potassium ions. Molybdenum diselenide (MoSe2) has recently been recognized as a promising anode material for potassium‐ion batteries, achieving high capacity and favorable cycling stability. However, KICs based on MoSe2 are scarcely demonstrated by far. Herein, a diatomite‐templated synthetic strategy is devised to fabricate nitrogen‐doped MoSe2/graphene (N‐MoSe2/G) composites with favorable pseudocapacitive potassium storage targeting a superior anode material for KICs. Benefiting from the unique biomorphic structure, high electron/K‐ion conductivity, enriched active sites, and the conspicuous pseudocapacitive effect of N‐MoSe2/G, thus‐derived KIC full‐cell manifests high energy/power densities (maximum 119 Wh kg−1/7212 W kg−1), outperforming those of recently reported KIC counterparts. Furthermore, the potassium storage mechanism of N‐MoSe2/G composite is systematically explored with the aid of first‐principles calculations in combination of in situ X‐ray diffraction and ex situ Raman spectroscopy/transmission electron microscopy/X‐ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]