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The use of separators that are thinner than conventional separators (> 20 µm) would improve the energy densities and specific energies of lithium batteries. However, thinner separators increase the risk of internal short circuits from lithium dendrites formed in both lithium-ion and lithium metal batteries. Herein, we grow metal-organic frameworks (MOFs) inside the channels of a polypropylene separator (8 µm thick) using current-driven electrosynthesis, which aggregates the electrolyte in the MOF channels. Compared to unmodified polypropylene separators, the MOF-modified separator (9 µm thick) vastly improves the cycling stability and dendrite resistance of cells assembled with Li metal anodes and carbonate-based electrolytes. As a demonstration, a 354 Wh kg −1 pouch cell with a lithium metal anode and LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA)-based cathode (N/P = 3.96) is assembled with 9 µm layer of the MOF-modified separator and retains 80% of its capacity after 200 cycles (charged at 75 mA g −1 , discharged at 100 mA g −1 ) at 25 °C. Thin separators can improve batteries’ energy densities but increase cell shortcircuit risks. Here, the authors report an improved thin metal-organic frameworks separator to improve the dendrite formation resistance and cycling stability of high-voltage lithium battery in carbonate electrolytes.

HighlightsA novel hydrogel with high water retention and Zn2+ transference number of 0.604 was constructed by copolymerizing sulfobetaine and acrylamide in Zn(ClO4)2 solution.The designed electrolyte configuration enables in situ generation of the organic–inorganic hybrid interface, which contributes to the electrodeposition uniformity and corrosion resistance of the anode.Zn–Zn and Zn–MnO2 cells based on hydrogel electrolyte exhibit outstanding cycling stability (over 3000 h under 0.5 mA cm−2/0.5 mAh cm−2 after two-time shelving).Aqueous zinc metal batteries are noted for their cost-effectiveness, safety and environmental friendliness. However, the water-induced notorious issues such as continuous electrolyte decomposition and uneven Zn electrochemical deposition remarkably restrict the development of the long-life zinc metal batteries. In this study, zwitterionic sulfobetaine is introduced to copolymerize with acrylamide in zinc perchlorate (Zn(ClO4)2) solution. The designed gel framework with hydrophilic and charged groups can firmly anchor water molecules and construct ion migration channels to accelerate ion transport. The in situ generated hybrid interface, which is composed of the organic functionalized outer layer and inorganic Cl− containing inner layer, can synergically lower the mass transfer overpotential, reduce water-related side reactions and lead to uniform Zn deposition. Such a novel electrolyte configuration enables Zn//Zn cells with an ultra-long cycling life of over 3000 h and a low polarization potential (~ 0.03 V) and Zn//Cu cells with high Coulombic efficiency of 99.18% for 1000 cycles. Full cells matched with MnO2 cathodes delivered laudable cycling stability and impressive shelving ability. Besides, the flexible quasi-solid-state batteries which are equipped with the anti-vandalism ability (such as cutting, hammering and soaking) can successfully power the LED simultaneously. Such a safe, processable and durable hydrogel promises significant application potential for long-life flexible electronic devices.

The inferior tolerance with reversible accommodation of large‐sized Na+ ion in electrode materials has plagued the adaptability of sodium‐ion chemistry. The sluggish diffusion kinetics of Na+ also baffles the desirability. Herein, a carbon fiber supported binder‐free electrode consisting of bismuth and carbon composite is designed. Well‐confined bismuth nanodots are synthesized by replacing cobalt in the metal–organic frameworks (MOF)–derived, nitrogen‐doped carbon arrays, which are demonstrated with remarkable reversibility during sodiation and desodiation. Cobalt species in the pristine MOF catalyze the graphitization around organic components in calcination, generating a highly conductive network in which the bismuth is to be embedded. The uniformly dispersed bismuth nanodots provide plenty boundaries and abundant active sites in the carbon arrays, where fast sodium storage kinetics are realized to contribute extra capacity and excellent rate performance. Bismuth nanodots are synthesized by confined replacement reaction with cobalt from metal–organic frameworks (MOF)‐derived templates on carbon fiber substrate. As binder‐free electrode for sodium‐ion batteries, nanosized bismuth can accommodate volume changes during sodiation/desodiation. The carbon arrays are with plenty phase boundaries and abundant active sites, which can contribute to extra capacity and excellent rate performance with fast capacitive sodium storage kinetics.

Sodium superionic conductor (NASICON)-type compounds have been regarded as promising cathodes for sodium-ion batteries (SIBs) due to their favorable ionic conductivity and robust structural stability. However, their high cost and relatively low energy density restrict their further practical application, which can be tailored by widening the operating voltages with earth-abundant elements such as Mn. Here, we propose a rational strategy of infusing Mn element in NASICON frameworks with sufficiently mobile sodium ions that enhances the redox voltage and ionic migration activity. The optimized structure of Na 3.5 Mn 0.5 V 1.5 (PO 4 ) 3 /C is achieved and investigated systematically to be a durable cathode (76.6% capacity retention over 5,000 cycles at 20 C) for SIBs, which exhibits high reversible capacity (113.1 mAh·g −1 at 0.5 C) with relatively low volume change (7.6%). Importantly, its high-areal-loading and temperature-resistant sodium ion storage properties are evaluated, and the full-cell configuration is demonstrated. This work indicates that this Na 3.5 Mn 0.5 V 1.5 (PO 4 ) 3 /C composite could be a promising cathode candidate for SIBs.

Hard carbons are promising anode materials for sodium‐ion batteries. To meet practical requirements, searching for durable and conductive carbon with a stable interface is of great importance. Here, we prepare a series of vanadium‐modified hard carbon submicrospheres by using hydrothermal carbonization followed by high‐temperature pyrolysis. Significantly, the introduction of vanadium can facilitate the nucleation and uniform growth of carbon spheres and generate abundant V–O–C interface bonds, thus optimizing the reaction kinetic. Meanwhile, the optimized hard carbon spheres modified by vanadium carbide, with sufficient pseudographitic domains, provide more active sites for Na ion migration and storage. As a result, the HC/VC‐1300 electrode exhibits excellent Na storage performance, including a high capacity of 420 mAh g−1 at 50 mA g−1 and good rate capability at 1 A g−1. This study proposes a new strategy for the synthesis of hard carbon spheres with high tap density and emphasizes the key role of pseudographitic structure for Na storage and interface stabilization. The HC/VC materials were synthesized by using hydrothermal carbonization followed by high‐temperature pyrolysis. The HC/VC‐1300 material has abundant V–O–C interface bonds and sufficient pseudographitic domains to provide more active sites for Na ion migration and storage, optimizing the reaction kinetics, resulting in good structural stability and excellent Na storage properties.

Vanadium oxides with a layered structure are promising candidates for both lithium-ion batteries and sodium-ion batteries （SIBs）. The self-template approach, which involves a transformation from metal-organic frameworks （MOFs） into porous metal oxides, is a novel and effective way to achieve desirable electrochemical performance. In this stud~ porous shuttle-like vanadium oxides （i.e., V205, V203/C） were successfully prepared by using MIL-88B （V） as precursors with a specific calcination process. As a proof-of-concept application, the as- prepared porous shuttle-like VaOdC was used as an anode material for SIBs. The porous shuttle-like V203/C, which had an inherent layered structure with metallic behavior, exhibited excellent electrochemical properties. Remarkable rate capacities of 417, 247, 202, 176, 164, and 149 mAh.g-1 were achieved at current densities of 50, 100, 200, 500, 1,000, and 2,000 mA.g-1, respectively. Under cycling at 2 A.g-1, the specific discharge capacity reached 181 mAh.g-1, with a low capacity fading rate of 0.032% per cycle after 1,000 cycles. Density functional theory calculation results indicated that Na ions preferred to occupy the interlamination rather than the inside of each layer in the V203. Interestingly, the special layered structure with a skeleton of dumbbell-like V-V bonds and metallic behavior was maintained after the insertion of Na ions, which was beneficial for the cycle performance. We consider that the MOF precursor of MIL-88B （V） can be used to synthesize other porous V-based materials for various applications.

HighlightsMoSe2/MoC/C multiphase boundaries boost ionic transfer kinetics.MoSe2 (5–10 nm) with rich edge sites is uniformly coated in N-doped framework.The obtained MoSe2 nanodots achieved ultralong cycle performance in LIBs and high capacity retention in full cell.Interface engineering has been widely explored to improve the electrochemical performances of composite electrodes, which governs the interface charge transfer, electron transportation, and structural stability. Herein, MoC is incorporated into MoSe2/C composite as an intermediate phase to alter the bridging between MoSe2- and nitrogen-doped three-dimensional (3D) carbon framework as MoSe2/MoC/N–C connection, which greatly improve the structural stability, electronic conductivity, and interfacial charge transfer. Moreover, the incorporation of MoC into the composites inhibits the overgrowth of MoSe2 nanosheets on the 3D carbon framework, producing much smaller MoSe2 nanodots. The obtained MoSe2 nanodots with fewer layers, rich edge sites, and heteroatom doping ensure the good kinetics to promote pseudo-capacitance contributions. Employing as anode material for lithium-ion batteries, it shows ultralong cycle life (with 90% capacity retention after 5000 cycles at 2 A g−1) and excellent rate capability. Moreover, the constructed LiFePO4//MoSe2/MoC/N–C full cell exhibits over 86% capacity retention at 2 A g−1 after 300 cycles. The results demonstrate the effectiveness of the interface engineering by incorporation of MoC as interface bridging intermediate to boost the lithium storage capability, which can be extended as a potential general strategy for the interface engineering of composite materials.

Sodium‐ion batteries are widely regarded as a promising supplement for lithium‐ion battery technology. However, it still suffers from some challenges, including low energy/power density and unsatisfactory cycling stability. Here, a cross‐linked graphene‐caged Na3V2(PO4)2F3 microcubes (NVPF@rGO) composite via a one‐pot hydrothermal strategy followed by freeze drying and heat treatment is reported. As a cathode for a sodium‐ion half‐cell, the NVPF@rGO delivers excellent cycling stability and rate capability, as well as good low temperature adaptability. The structural evolution during the repeated Na+ extraction/insertion and Na ions diffusion kinetics in the NVPF@rGO electrode are investigated. Importantly, a practicable sodium‐ion full‐cell is constructed using a NVPF@rGO cathode and a N‐doped carbon anode, which delivers outstanding cycling stability (95.1% capacity retention over 400 cycles at 10 C), as well as an exceptionally high energy density (291 Wh kg−1 at power density of 192 W kg−1). Such micro‐/nanoscale design and engineering strategies, as well as deeper understanding of the ion diffusion kinetics, may also be used to explore other micro‐/nanostructure materials to boost the performance of energy storage devices. A practical sodium‐ion full‐cell is constructed using a Na3V2(PO4)2F3@reduced graphene oxide cathode and a N‐doped carbon anode. It delivers outstanding cycling stability (95.1% capacity retention over 400 cycles at 10 C), as well as an exceptionally high energy density (291 Wh kg−1 at power density of 192 W kg−1).

Indisciplinable dendrite growth, harsh side reactions, and sluggish kinetics at the Zn electrode/electrolyte interface severely obstruct the commercialization of zinc‐metal batteries. Besides, the development of wearable devices has set a higher demand for the safety and biocompatibility of batteries. Herein, an in situ acid dipping approach is devised to spontaneously construct a functional and antibacterial interfacial layer containing carbonyl oxygen groups on the surface of zinc foils, using aqueous malic acid (denoted as MZ@Zn electrode) to tackle the above issues. The interfacial layer possesses satisfactory zincophilicity, promoting the ion kinetics and homogenizing the Zn deposition/dissolution. The MZ layer tightly adhered to the Zn electrode, and the deliberately exposed (0 0 2)Zn planes assure favorable anticorrosive quality. Moreover, the MZ layer possesses high antimicrobial activity, ensuring biological safety. Consequently, the MZ@Zn electrodes display ultralong cycle stability over 3500 h at 5 mA cm−2. Furthermore, the full cells installed with LiFePO4/C (LFP/C) and NH4V4O10 (NVO) cathodes exhibit superior electrochemical performances. Therefore, the stabilized zinc‐metal anode achieved by acid etching to spontaneously construct a functional interfacial layer provides a simple and effective strategy for aqueous zinc‐metal batteries. A functional artificial interfacial layer, containing special carbonyl oxygen groups, is spontaneously constructed in situ on Zn anode by an etching method with malic acid and achieves the long‐term stability of aqueous ZIBs. The carbonyl oxygen with high nucleophilicity and strong zincophilicity can inhibit the side reactions, while enhancing ion‐transfer kinetics and enabling the uniform nucleation and deposition of Zn.

Aqueous zinc‐metal batteries (AZMBs) have received tremendous attentions due to their high safety, low cost, environmental friendliness, and simple process. However, zinc‐metal still suffer from uncontrollable dendrite growth and surface parasitic reactions that reduce the Coulombic efficiency (CE) and lifetime of AZMBs. These problems which are closely related to the active water are not well‐solved. Here, an ultrathin crack‐free metal–organic framework (ZIF‐7 x ‐8) with rigid sub‐nanopore (0.3 nm) is constructed on Zn‐metal to promote the de‐solvation of zinc‐ions before approaching Zn‐metal surface, reduce the contacting opportunity between water and Zn, and consequently eliminate water‐induced corrosion and side‐reactions. Due to the presence of rigid and ordered sub‐nanochannels, Zn‐ions deposits on Zn‐metal follow a highly ordered manner, resulting in a dendrite‐free Zn‐metal with negligible by‐products, which significantly improve the reversibility and lifespan of Zn‐metals. As a result, Zn‐metal protected by ultrathin crack‐free ZIF‐7 x ‐8 layer exhibits excellent cycling stability (over 2200 h) and extremely‐high 99.96% CE during 6000 cycles. The aqueous PANI‐V 2 O 5 //ZIF‐7 x ‐8@Zn full‐cell preserves 86% high‐capacity retention even after ultra‐long 2000 cycles. The practical pouch‐cell can also be cycled for more than 120 cycles. It is believed that the simple strategy demonstrated in this work can accelerate the practical utilizations of AZMBs.