Sub-nanopores enabling optimized ion storage performance of carbon cathodes for Zn-ion hybrid supercapacitors.

Aqueous Zn-ion hybrid supercapacitors (ZHSs) are attracting significant attention as a promising electrochemical energy storage system. However, carbon cathodes of ZHSs exhibit unsatisfactory ion storage performance due to the large size of hydrated Zn-ions (e.g., [Zn(H2O)6]2+), which encumbers compact ion arrangement and rapid ion transport at the carbon-electrolyte interfaces. Herein, a porous carbon material (HMFC) with abundant sub-nanopores is synthesized to optimize the ion storage performance of the carbon cathode in ZHSs, in which the sub-nanopores effectively promote the dehydration of hydrated Zn-ions and thus optimize the ion storage performance of the carbon cathode in ZHSs. A novel strategy is proposed to study the dehydration behaviors of hydrated Zn-ions in carbon cathodes, including quantitatively determining the desolvation activation energy of hydrated Zn-ions and in-situ monitoring active water content at the carbon-electrolyte interface. The sub-nanopores-induced desolvation effect is verified, and its coupling with large specific surface area and hierarchically porous structure endows the HMFC cathode with improved electrochemical performance, including a 53 % capacity increase compared to the carbon cathode counterpart without sub-nanopores, fast charge/discharge ability that can output 46.0 Wh/kg energy within only 4.4 s, and 98.2 % capacity retention over 20,000 charge/discharge cycles. This work provides new insights into the rational design of porous carbon cathode materials toward high-performance ZHSs.

Negatively Charged Hydrophobic Carbon Nano-Onion Interfacial Layer Enabling High-Rate and Ultralong-Life Zn-Based Energy Storage.

Zn-based electrochemical energy storage (EES) systems are attracting more attention, whereas their large-scale application is restricted by the dendrite and parasitic reaction-caused unstable Zn anodes. Herein, a negatively charged hydrophobic carbon nano-onion (CNO) interfacial layer is proposed to realize ultrastable and high-rate Zn anodes, enabling high-performance Zn-based EES. For the CNO interfacial layer, its hydrophobicity not only blocks active water but also reduces the Zn2+ desolvation barrier, and meanwhile, the negatively-charged CNO nanoparticles adsorb Zn2+ and repel SO4 2- to homogenize Zn2+ flux, accelerate Zn2+ desolvation and suppress the self-corrosion of Zn anodes. Besides, the conductive CNO interfacial layer increases the surface area for the Zn deposition to reduce local current density. Consequently, under the modulation of the CNO interfacial layer, Zn plating/stripping exhibits impressive reversibility with an average Coulombic efficiency of 99.4% over 800 cycles, and Zn anodes present significantly enhanced electrochemical stability and rate performance, whose operation lifetime exceeds 2000 h at 1 mA cm-2 and 350 h even at 10 mA cm-2 . Moreover, high-rate and ultralong-life Zn-ion hybrid supercapacitors are achieved with the CNO interfacial layer-modulated Zn anode and activated CNO cathode. This work provides new thinking in regulating the Zn deposition interface to realize high-performance Zn-based EES.

Designing of zwitterionic proline hydrogel electrolytes for anti-freezing supercapacitors.

Hydrogel electrolytes containing a large amount of freezable water tend to freeze at subzero temperatures, which catastrophically reduces their ionic conductivity and thus limits their practical applications. In this work, we propose a new type anti-freezing hydrogel electrolyte based on an additive of zwitterionic proline, which can maintain high ionic conductivities of hydrogel electrolytes at subzero temperatures. The unique zwitterionic structure leads to several interesting characters like strong hydration, strong ionic interactions and low self-associations, which is proved to be the keys for the high performance of hydrogel electrolytes under low temperatures. As a result, the proline hydrogel electrolytes show a high ionic conductivity of 4.2 mS cm-1 even at -40 °C. The activated carbon electrode of supercapacitors based on proline hydrogel electrolytes delivers high specific capacitances of 145.8 (at 0.5 A g-1) and 116.1 F g-1 (at 0.5 A g-1) at 25 and -30 °C, respectively. Furthermore, the specific capacitance still shows a high retention of 71% after 12,000 charge/discharge cycles at -30 °C, confirming the good low-temperature adaptability. Such anti-freezing electrolytes with high ionic conductivity will open up a new avenue for anti-freezing energy storage devices, not limited to supercapacitors.

Heteroatom-rich carbon cathodes toward high-performance flexible zinc-ion hybrid supercapacitors.

Aqueous zinc-ion hybrid supercapacitors (ZHSs) are attracting increased attention as emerging electrochemical energy storage systems. However, the design of high-performance carbon cathodes for ZHSs remains a challenge. Herein, we report the synthesis of heteroatom-rich carbon cathodes based on a biomass precursor of yeast and a hydrothermal pre-carbonization strategy, realizing high-performance ZHSs. The yeast is composed of polysaccharide chains containing abundant O/N heteroatoms, and a hydrothermal pre-carbonization process is conducive to preserving these heteroatoms in the high-specific-surface-area carbon materials obtained by carbonizing-activating the yeast precursor. As a result, the synthesized carbon materials are endowed with high O/N heteroatom contents (exceeding 13.9 at%), and present superior electrochemical performance in ZHSs, including a high specific capacity of 132 mAh/g, a high energy density of 94.4 Wh/kg and outstanding cycling stability with ∼100% capacity retention after 7000 cycles at 5 A/g. Besides, the heteroatom-rich carbon cathodes show a high capacity retention of 85.3% when their mass loading increases from 3.8 to 12.2 mg/cm2, demonstrating promising application for practical ZHSs. Electrochemical analysis reveals that the O/N heteroatoms promote ion chemical adsorption and thus the electrochemical properties of the carbon cathodes. Furthermore, flexible ZHS devices constructed with the heteroatom-rich carbon cathodes and a biodegradable ZnSO4/dough solid-state electrolyte exhibit excellent flexibility (as reflected by almost unchanged capacity under different bending states and 85% capacity retention after 500 bending cycles) as well as good repairability after dehydration under abnormal environments. This study offers new thinking in designing high-performance carbon cathodes and promotes nonflexible/flexible ZHSs moving towards practical applications.

Functional Ultrathin Separators Proactively Stabilizing Zinc Anodes for Zinc-Based Energy Storage.

Ultrathin separators are indispensable to high-energy-density zinc-ion batteries (ZIBs), but their easy failure caused by zinc dendrites poses a great challenge. Herein, 23 µm-thick functional ultrathin separators (FUSs), realizing superb electrochemical stability of zinc anodes and outstanding long-term durability of ultrathin separators, are reported. In the FUSs, an ultrathin but mechanically strong nanoporous membrane substrate benefits fast and flux-homogenized Zn2+ transport, while a metal-organic framework (MOF)-derived C/Cu nanocomposite decoration layer provides rich low-barrier zinc nucleation sites, thereby synergistically stabilizing zinc anodes to inhibit zinc dendrites and dendrite-caused separator failure. Investigation of the zinc affinity of the MOF-derived C/Cu nanocomposites unravels the high zincophilicity of heteroatom-containing C/Cu interfaces. Zinc anodes coupled with the FUSs present superior electrochemical stability, whose operation lifetime exceeds 2000 h at 1 mA cm-2 and 600 h at 10 mA cm-2 , 40-50 times longer than that of the zinc anodes using glass-fiber separators. The reliability of the FUSs in ZIBs and zinc-ion hybrid supercapacitors is also validated. This work proposes a new strategy to stabilize zinc anodes and provides theoretical guidance in developing ultrathin separators for high-energy-density zinc-based energy storage.

Sieve-Like interface built by ZnO porous sheets towards stable zinc anodes.

Zn-based electrochemical energy storage (EES) systems are plagued by the uncontrollable generation of dendritic zinc and side reactions on zinc anodes. Herein, we report a ZnO porous sheets-assembled sieve-like interface to stabilize zinc anodes. Specifically, ZnO porous sheets are synthesized through the thermal decomposition of basic zinc sulfate nanoflakes and then served as an artificial zinc anode-electrolyte interface. Benefiting from the sieve-like interface formed by the ZnO porous sheets, Zn2+ flux is effectively homogenized during the zinc plating process and thus zinc dendrite growth is restricted. Meanwhile, the corrosion behavior of zinc anodes is alleviated thanks to the hydrophobic feature of the ZnO porous sheets. As a result, the electrochemical properties of zinc anodes are notably optimized under the protection of such a sieve-like interface. Cycling life evaluated at 1 mA cm-2 of the zinc anodes is prolonged from less than 100 h for bare zinc anodes to 2800 h for the protected zinc anodes (Zn@ZnO), and even at 5 mA cm-2, the latter ones can operate normally for 400 h. As expected, the cycling life of VO2//Zn@ZnO zinc-ion batteries is greatly increased, achieving 90% capacity retention after 1000 cycles at 5 A g-1 and activated carbon fiber//Zn@ZnO zinc-ion hybrid supercapacitors possess 96% capacity retention after 10,000 cycles at 1 A g-1. This work provides a promising approach for improving the electrochemical stability of the Zn-based EES system.

Material Design and Energy Storage Mechanism of Mn-Based Cathodes for Aqueous Zinc-Ion Batteries.

Mn-based cathodes have been widely explored for aqueous zinc-ion batteries (ZIBs), by virtue of their high theoretical capacity and low cost. However, Mn-based cathodes suffer from poor rate capability and cycling performance. Researchers have presented various approaches to address these issues. Therefore, these endeavors scattered in various directions (e. g., designing electrode structures, defect engineering and optimizing electrolytes) are necessary to be connected through a systematic review. Hence, we comprehensively overview Mn-based cathode materials for ZIBs from the aspects of phase compositions, electrochemical behaviors and energy storage mechanisms, and try to build internal relations between these factors. Modification strategies of Mn-based cathodes are then introduced. Furthermore, this review also provides some new perspectives on future efforts toward high-energy and long-life Mn-based cathodes for ZIBs.

Stable Zinc Anodes Enabled by Zincophilic Cu Nanowire Networks.

Zn-based electrochemical energy storage (EES) systems have received tremendous attention in recent years, but their zinc anodes are seriously plagued by the issues of zinc dendrite and side reactions (e.g., corrosion and hydrogen evolution). Herein, we report a novel strategy of employing zincophilic Cu nanowire networks to stabilize zinc anodes from multiple aspects. According to experimental results, COMSOL simulation and density functional theory calculations, the Cu nanowire networks covering on zinc anode surface not only homogenize the surface electric field and Zn2+ concentration field, but also inhibit side reactions through their hydrophobic feature. Meanwhile, facets and edge sites of the Cu nanowires, especially the latter ones, are revealed to be highly zincophilic to induce uniform zinc nucleation/deposition. Consequently, the Cu nanowire networks-protected zinc anodes exhibit an ultralong cycle life of over 2800 h and also can continuously operate for hundreds of hours even at very large charge/discharge currents and areal capacities (e.g., 10 mA cm-2 and 5 mAh cm-2), remarkably superior to bare zinc anodes and most of currently reported zinc anodes, thereby enabling Zn-based EES devices to possess high capacity, 16,000-cycle lifespan and rapid charge/discharge ability. This work provides new thoughts to realize long-life and high-rate zinc anodes.

Simultaneously Regulating Uniform Zn2+ Flux and Electron Conduction by MOF/rGO Interlayers for High-Performance Zn Anodes.

Owing to the merits of low cost, high safety and environmental benignity, rechargeable aqueous Zn-based batteries (ZBs) have gained tremendous attention in recent years. Nevertheless, the poor reversibility of Zn anodes that originates from dendrite growth, surface passivation and corrosion, severely hinders the further development of ZBs. To tackle these issues, here we report a Janus separator based on a Zn-ion conductive metal-organic framework (MOF) and reduced graphene oxide (rGO), which is able to regulate uniform Zn2+ flux and electron conduction simultaneously during battery operation. Facilitated by the MOF/rGO bifunctional interlayers, the Zn anodes demonstrate stable plating/stripping behavior (over 500 h at 1 mA cm-2), high Coulombic efficiency (99.2% at 2 mA cm-2 after 100 cycles) and reduced redox barrier. Moreover, it is also found that the Zn corrosion can be effectively retarded through diminishing the potential discrepancy on Zn surface. Such a separator engineering also saliently promotes the overall performance of Zn|MnO2 full cells, which deliver nearly 100% capacity retention after 2000 cycles at 4 A g-1 and high power density over 10 kW kg-1. This work provides a feasible route to the high-performance Zn anodes for ZBs.

Towards High-Energy and Anti-Self-Discharge Zn-Ion Hybrid Supercapacitors with New Understanding of the Electrochemistry.

Aqueous Zn-ion hybrid supercapacitors (ZHSs) are increasingly being studied as a novel electrochemical energy storage system with prominent electrochemical performance, high safety and low cost. Herein, high-energy and anti-self-discharge ZHSs are realized based on the fibrous carbon cathodes with hierarchically porous surface and O/N heteroatom functional groups. Hierarchically porous surface of the fabricated free-standing fibrous carbon cathodes not only provides abundant active sites for divalent ion storage, but also optimizes ion transport kinetics. Consequently, the cathodes show a high gravimetric capacity of 156 mAh g-1, superior rate capability (79 mAh g-1 with a very short charge/discharge time of 14 s) and exceptional cycling stability. Meanwhile, hierarchical pore structure and suitable surface functional groups of the cathodes endow ZHSs with a high energy density of 127 Wh kg-1, a high power density of 15.3 kW kg-1 and good anti-self-discharge performance. Mechanism investigation reveals that ZHS electrochemistry involves cation adsorption/desorption and Zn4SO4(OH)6·5H2O formation/dissolution at low voltage and anion adsorption/desorption at high voltage on carbon cathodes. The roles of these reactions in energy storage of ZHSs are elucidated. This work not only paves a way for high-performance cathode materials of ZHSs, but also provides a deeper understanding of ZHS electrochemistry.

High-Performance Aqueous Zinc-Ion Batteries Realized by MOF Materials.

Rechargeable aqueous zinc-ion batteries (ZIBs) have been gaining increasing interest for large-scale energy storage applications due to their high safety, good rate capability, and low cost. However, the further development of ZIBs is impeded by two main challenges: Currently reported cathode materials usually suffer from rapid capacity fading or high toxicity, and meanwhile, unstable zinc stripping/plating on Zn anode seriously shortens the cycling life of ZIBs. In this paper, metal-organic framework (MOF) materials are proposed to simultaneously address these issues and realize high-performance ZIBs with Mn(BTC) MOF cathodes and ZIF-8-coated Zn (ZIF-8@Zn) anodes. Various MOF materials were synthesized, and Mn(BTC) MOF was found to exhibit the best Zn2+-storage ability with a capacity of 112 mAh g-1. Zn2+ storage mechanism of the Mn(BTC) was carefully studied. Besides, ZIF-8@Zn anodes were prepared by coating ZIF-8 MOF material on Zn foils. Unique porous structure of the ZIF-8 coating guided uniform Zn stripping/plating on the surface of Zn anodes. As a result, the ZIF-8@Zn anodes exhibited stable Zn stripping/plating behaviors, with 8 times longer cycle life than bare Zn foils. Based on the above, high-performance aqueous ZIBs were constructed using the Mn(BTC) cathodes and the ZIF-8@Zn anodes, which displayed an excellent long-cycling stability without obvious capacity fading after 900 charge/discharge cycles. This work provides a new opportunity for high-performance energy storage system.

Printable Zinc-Ion Hybrid Micro-Capacitors for Flexible Self-Powered Integrated Units.

Wearable self-powered systems integrated with energy conversion and storage devices such as solar-charging power units arouse widespread concerns in scientific and industrial realms. However, their applications are hampered by the restrictions of unbefitting size matching between integrated modules, limited tolerance to the variation of input current, reliability, and safety issues. Herein, flexible solar-charging self-powered units based on printed Zn-ion hybrid micro-capacitor as the energy storage module is developed. Unique 3D micro-/nano-architecture of the biomass kelp-carbon combined with multivalent ion (Zn2+) storage endows the aqueous Zn-ion hybrid capacitor with high specific capacity (196.7 mAh g-1 at 0.1 A g-1). By employing an in-plane asymmetric printing technique, the fabricated quasi-solid-state Zn-ion hybrid micro-capacitors exhibit high rate, long life and energy density up to 8.2 µWh cm-2. After integrating the micro-capacitor with organic solar cells, the derived self-powered system presents outstanding energy conversion/storage efficiency (ηoverall = 17.8%), solar-charging cyclic stability (95% after 100 cycles), wide current tolerance, and good mechanical flexibility. Such portable, wearable, and green integrated units offer new insights into design of advanced self-powered systems toward the goal of developing highly safe, economic, stable, and long-life smart wearable electronics.

K2 Ti2 O5 @C Microspheres with Enhanced K+ Intercalation Pseudocapacitance Ensuring Fast Potassium Storage and Long-Term Cycling Stability.

Benefiting from the natural abundance and low standard redox potential of potassium, potassium-ion batteries (PIBs) are regarded as one of the most promising alternatives to lithium-ion batteries for low-cost energy storage. However, most PIB electrode materials suffer from sluggish thermodynamic kinetics and dramatic volume expansion during K+ (de)intercalation. Herein, it is reported on carbon-coated K2 Ti2 O5 microspheres (S-KTO@C) synthesized through a facile spray drying method. Taking advantage of both the porous microstructure and carbon coating, S-KTO@C shows excellent rate capability and cycling stability as an anode material for PIBs. Furthermore, the intimate integration of carbon coating through chemical vapor deposition technology significantly enhances the K+ intercalation pseudocapacitive behavior. As a proof of concept, a potassium-ion hybrid capacitor is constructed with the S-KTO@C (battery-type anode material) and the activated carbon (capacitor-type cathode material). The assembled device shows a high energy density, high power density, and excellent capacity retention. This work can pave the way for the development of high-performance potassium-based energy storage devices.

Enhanced Hydrogenation Performance over Hollow Structured Co-CoOx@N-C Capsules.

It is desirable to design nonprecious metal nanocatalysts with high stability and catalytic performance for fine chemicals production. Here, a method is reported for the preparation of cobalt metal and cobalt oxide cores confined within nanoporous nitrogen-doped hollow carbon capsules. Core-shell structured Zn/Co-ZIF@polymer materials are fabricated through a facile coating polymer strategy on the surface of zeolitic imidazolate frameworks (ZIF). A series of hollow carbon capsules with cobalt metal and cobalt oxide are derived from a facile confined pyrolysis of Zn/Co-ZIF@polymer. The hollow Co-CoOx@N-C capsules can prevent sintering and agglomeration of the cobalt nanoparticles and the nanoporous shell allows for efficient mass transport. The specific surface area and Co particle size are optimized through finely tuning the original Zn content in ZIF particles, thus enhancing overall catalytic activity. The yolk-shell structured Zn4Co1Ox@carbon hollow capsules are shown to be a highly active and selective catalyst (selectivity >99%) for hydrogenation of nitrobenzene to aniline. Furthermore, Zn4Co1Ox@carbon hollow particles show superior catalytic stability, and no deactivation after 8 cycles of reaction. The hollow Co-CoOx@N-C capsules may shed light on a green and sustainable catalytic process for fine chemicals production.

Room-Temperature Synthesis of Two-Dimensional Hexagonal Boron Nitride Nanosheet-Stabilized CsPbBr3 Perovskite Quantum Dots.

Poor stability always restricts the application of all-inorganic perovskite quantum dots (PQDs). Herein, 2D hexagonal boron nitride ( h-BN) nanosheets were firstly utilized to stabilize CsPbBr3 PQDs through a facile heterogeneous nucleation-growth process at room temperature. In synthesized h-BN/CsPbBr3 PQD nanocomposites, cubic CsPbBr3 PQDs adhere on h-BN nanosheet surfaces, benefiting from the high specific surface area and abundant mesopores of 2D nanosheets. The nanocomposites prepared at optimized loading of h-BN nanosheets and reaction time display good green-emitting performance with a narrow full width at half maximum of ∼20.0 nm and high color purity of 92.0%. Unique 2D structure and excellent thermal conductivity of h-BN nanosheets endow the h-BN/CsPbBr3 PQD nanocomposites with significantly enhanced humidity stability and thermal stability. The white light-emitting diodes (LEDs) assembled with green-emitting nanocomposites, a blue chip, and a commercial red phosphor possess a low correlated color temperature of 4190 K, color-rendering index of 76, and high luminous efficacy of 57 lm/W. Further, the color gamut of the synthetic white light based on blue-emitting h-BN/CsPbBr1.5Cl1.5 PQDs, green-emitting h-BN/CsPbBr3 PQDs, and red-emitting h-BN/CsPbBr1.2I1.8 PQDs is 114% of the National Television System Committee standard. This work paves a new way for utilizing 2D nanomaterials to synthesize stable all-inorganic PQDs for white LEDs and displays.

Novel Insights into Energy Storage Mechanism of Aqueous Rechargeable Zn/MnO2 Batteries with Participation of Mn2.

Aqueous rechargeable Zn/MnO2 zinc-ion batteries (ZIBs) are reviving recently due to their low cost, non-toxicity, and natural abundance. However, their energy storage mechanism remains controversial due to their complicated electrochemical reactions. Meanwhile, to achieve satisfactory cyclic stability and rate performance of the Zn/MnO2 ZIBs, Mn2+ is introduced in the electrolyte (e.g., ZnSO4 solution), which leads to more complicated reactions inside the ZIBs systems. Herein, based on comprehensive analysis methods including electrochemical analysis and Pourbaix diagram, we provide novel insights into the energy storage mechanism of Zn/MnO2 batteries in the presence of Mn2+. A complex series of electrochemical reactions with the co-participation of Zn2+, H+, Mn2+, SO42-, and OH- were revealed. During the first discharge process, co-insertion of Zn2+ and H+ promotes the transformation of MnO2 into ZnxMnO4, MnOOH, and Mn2O3, accompanying with increased electrolyte pH and the formation of ZnSO4·3Zn(OH)2·5H2O. During the subsequent charge process, ZnxMnO4, MnOOH, and Mn2O3 revert to α-MnO2 with the extraction of Zn2+ and H+, while ZnSO4·3Zn(OH)2·5H2O reacts with Mn2+ to form ZnMn3O7·3H2O. In the following charge/discharge processes, besides aforementioned electrochemical reactions, Zn2+ reversibly insert into/extract from α-MnO2, ZnxMnO4, and ZnMn3O7·3H2O hosts; ZnSO4·3Zn(OH)2·5H2O, Zn2Mn3O8, and ZnMn2O4 convert mutually with the participation of Mn2+. This work is believed to provide theoretical guidance for further research on high-performance ZIBs.

High-Power and Ultralong-Life Aqueous Zinc-Ion Hybrid Capacitors Based on Pseudocapacitive Charge Storage.

Rechargeable aqueous zinc-ion hybrid capacitors and zinc-ion batteries are promising safe energy storage systems. In this study, amorphous RuO2·H2O for the first time was employed to achieve fast and ultralong-life Zn2+ storage based on a pseudocapacitive storage mechanism. In the RuO2·H2O||Zn zinc-ion hybrid capacitors with Zn(CF3SO3)2 aqueous electrolyte, the RuO2·H2O cathode can reversibly store Zn2+ in a voltage window of 0.4-1.6 V (vs. Zn/Zn2+), delivering a high discharge capacity of 122 mAh g-1. In particular, the zinc-ion hybrid capacitors can be rapidly charged/discharged within 36 s with a very high power density of 16.74 kW kg-1 and a high energy density of 82 Wh kg-1. Besides, the zinc-ion hybrid capacitors demonstrate an ultralong cycle life (over 10,000 charge/discharge cycles). The kinetic analysis elucidates that the ultrafast Zn2+ storage in the RuO2·H2O cathode originates from redox pseudocapacitive reactions. This work could greatly facilitate the development of high-power and safe electrochemical energy storage.

A Nacre-Like Carbon Nanotube Sheet for High Performance Li-Polysulfide Batteries with High Sulfur Loading.

Lithium-sulfur (Li-S) batteries are considered as one of the most promising energy storage systems for next-generation electric vehicles because of their high-energy density. However, the poor cyclic stability, especially at a high sulfur loading, is the major obstacles retarding their practical use. Inspired by the nacre structure of an abalone, a similar configuration consisting of layered carbon nanotube (CNT) matrix and compactly embedded sulfur is designed as the cathode for Li-S batteries, which are realized by a well-designed unidirectional freeze-drying approach. The compact and lamellar configuration with closely contacted neighboring CNT layers and the strong interaction between the highly conductive network and polysulfides have realized a high sulfur loading with significantly restrained polysulfide shuttling, resulting in a superior cyclic stability and an excellent rate performance for the produced Li-S batteries. Typically, with a sulfur loading of 5 mg cm-2, the assembled batteries demonstrate discharge capacities of 1236 mAh g-1 at 0.1 C, 498 mAh g-1 at 2 C and moreover, when the sulfur loading is further increased to 10 mg cm-2 coupling with a carbon-coated separator, a superhigh areal capacity of 11.0 mAh cm-2 is achieved.

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions.

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb monoliths (MHMs) with micrometer-scale channels are expected as efficient platforms for reactions and separations because of their large surface areas. Up to now, MHMs have been prepared by a unidirectional freeze-drying (UDF) method only from very limited precursors. Herein, we report a protocol from which a series of MHMs consisting of different components can be obtained. Recently, we found that cellulose nanofibers function as a distinct structure-directing agent towards the formation of MHMs through the UDF process. By mixing the cellulose nanofibers with water soluble substances which do not yield MHMs, a variety of composite MHMs can be prepared. This significantly enriches the chemical constitution of MHMs towards versatile applications.

One-Step Preparation of Long-Term Stable and Flexible CsPbBr3 Perovskite Quantum Dots/Ethylene Vinyl Acetate Copolymer Composite Films for White Light-Emitting Diodes.

CsPbBr3 perovskite quantum dots (PQDs)/ethylene vinyl acetate (EVA) composite films were prepared via a one-step method; on the basis of this, both supersaturated recrystallization of CsPbBr3 PQDs and dissolution of EVA were realized in toluene. The prepared films display outstanding green-emitting performance with high color purity of 92% and photoluminescence (PL) quantum yield of 40.5% at appropriate CsPbBr3 PQD loading. They possess long-term stable luminescent properties in the air and in water, benefiting from the effective protection of CsPbBr3 PQDs by the EVA matrix. Besides, the prepared CsPbBr3 PQDs/EVA films are flexible enough to be repeatedly bent for 1000 cycles while keeping unchanged the PL intensity. The optical properties of the CsPbBr3 PQDs/EVA films in white light-emitting diodes were also studied by experiments and theoretical simulation. Overall, facile preparation process, good long-term stability, and high flexibility allow our green-emitting CsPbBr3 PQDs/EVA films to be applied in lighting applications and flexible displays.