An Asymmetric Supercapacitor–Diode (CAPode) for Unidirectional Energy Storage

A new asymmetric capacitor concept is proposed providing high energy storage capacity for only one charging direction. Size‐selective microporous carbons (w<0.9 nm) with narrow pore size distribution are demonstrated to exclusively electrosorb small anions (BF₄^?) but size‐exclude larger cations (TBA⁺ or TPA⁺), while the counter electrode, an ordered mesoporous carbon (w>2 nm), gives access to both ions. This architecture exclusively charges in one direction with high rectification ratios (RR=12), representing a novel capacitive analogue of semiconductor‐based diodes (“CAPode”). By precise pore size control of microporous carbons (0.6 nm, 0.8 nm and 1.0 nm) combined with an ordered mesoporous counter electrode (CMK‐3, 4.8 nm) electrolyte cation sieving and unidirectional charging is demonstrated by analyzing the device charge‐discharge response and monitoring individual electrodes of the device via in situ NMR spectroscopy.     

Hierarchical Nanotubes Constructed by Carbon‐Coated Ultrathin SnS Nanosheets for Fast Capacitive Sodium Storage

Tin(II) sulfide (SnS) has been an attractive anode material for sodium ion batteries. Herein, an elegant templating method has been developed for the rational design and synthesis of hierarchical SnS nanotubes composed of ultrathin nanosheets. In order to enhance the electrochemical performance, carbon coated hierarchical SnS nanotubes (denoted as SnS@C nanotubes) have also been obtained by simply adding glucose into the reaction system. Benefiting from their unique structural merits, the SnS@C nanotubes exhibit enhanced sodium storage properties in terms of good cycling performance and superior rate capability.     

Heteroatom‐Doped Porous Carbon Materials with Unprecedented High Volumetric Capacitive Performance

The design of carbon‐based materials with a high mass density and large porosity has always been a challenging goal, since they fulfill the demands of next‐generation supercapacitors and other electrochemical devices. We report a new class of high‐density heteroatom‐doped porous carbon that can be used as an aqueous‐based supercapacitor material. The material was synthesized by an in situ dehalogenation reaction between a halogenated conjugated diene and nitrogen‐containing nucleophiles. Under the given conditions, pyridinium salts can only continue to perform the dehalogenation if there is residue water remaining from the starting materials. The obtained carbon materials are highly doped by various heteroatoms, leading to high densities, abundant multimodal pores, and an excellent volumetric capacitive performance. Porous carbon tri‐doped with nitrogen, phosphorous, and oxygen exhibits a high packing density (2.13 g cm^?3) and an exceptional volumetric energy density (36.8 Wh L^?1) in alkaline electrolytes, making it competitive to even some Ni‐MH cells.     

An Aligned and Laminated Nanostructured Carbon Hybrid Cathode for High‐Performance Lithium–Sulfur Batteries

An aligned and laminated sulfur‐absorbed mesoporous carbon/carbon nanotube (CNT) hybrid cathode has been developed for lithium–sulfur batteries with high performance. The mesoporous carbon acts as sulfur host and suppresses the diffusion of polysulfide, while the CNT network anchors the sulfur‐absorbed mesoporous carbon particles, providing pathways for rapid electron transport, alleviating polysulfide migration and enabling a high flexibility. The resulting lithium–sulfur battery delivers a high capacity of 1226 mAh g⁻¹ and achieves a capacity retention of 75 % after 100 cycles at 0.1 C. Moreover, a high capacity of nearly 900 mAh g⁻¹ is obtained for 20 mg cm⁻², which is the highest sulfur load to the best of our knowledge. More importantly, the aligned and laminated hybrid cathode endows the battery with high flexibility and its electrochemical performances are well maintained under bending and after being folded for 500 times.     

Two‐Dimensional Seeded Self‐Assembly of a Complex Hierarchical Perylene‐Based Heterostructure

A complex two‐dimensional (2D) hierarchical heterostructure was fabricated by a sequential two‐dimensional seeded self‐assembly, which consisted of laterally grown nanotubes from one perylene monomer and terminally elongated nanocoils from a similar perylene monomer on microribbon seeds from a third perylene. Because the nanotube and nanocoil monomers can form kinetically trapped off‐pathway aggregates to prevent self‐nucleation and have similar molecular organizations to different facets of the seeds, the nanotube and nanocoil monomers preferentially nucleate and grow on the seed sides and terminal ends, respectively, to form a complex 2D hierarchical heterostructure. The strategy used in this work can be extended to fabricate other complex nanoarchitectures from small molecules.     

Highly Crystalline Mesoporous Phosphotungstic Acid: A High‐Performance Electrode Material for Energy‐Storage Applications

Heteropoly acids (HPAs) are unique materials with interesting properties, including high acidity and proton conductivity. However, their low specific surface area and high solubility in polar solvents make them unattractive for catalytic or energy applications. This obstacle can be overcome by creating nanoporosity within the HPA. We synthesized mesoporous phosphotungstic acid (mPTA) with a spherical morphology through the self‐assembly of phosphotungstic acid (PTA) with a polymeric surfactant as stabilized by KCl and hydrothermal treatment. The mPTA nanostructures had a surface area of 93 m² g^?1 and a pore size of 4 nm. Their high thermal stability (ca. 450 °C) and lack of solubility in ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte are beneficial for lithium‐ion batteries (LIBs). Optimized mPTA showed a reversible capacity of 872 mAh g^?1 at 0.1 A g^?1 even after 100 cycles for LIBs, as attributed to a super‐reduced state of HPA and the storage of Li ions within the mesochannels of mPTA.     

Hydrolytic Transformation of Microporous Metal–Organic Frameworks to Hierarchical Micro‐ and Mesoporous MOFs

A new approach to the synthesis of hierarchical micro‐ and mesoporous MOFs from microporous MOFs involves a simple hydrolytic post‐synthetic procedure. As a proof of concept, a new microporous MOF, POST‐66(Y), was synthesized and its transformation into a hierarchical micro‐ and mesoporous MOF by water treatment was studied. This method produced mesopores in the range of 3 to 20 nm in the MOF while maintaining the original microporous structure, at least in part. The degree of micro‐ and mesoporosity can be controlled by adjusting the time and temperature of hydrolysis. The resulting hierarchical porous MOF, POST‐66(Y)‐wt, can be utilized to encapsulate nanometer‐sized guests such as proteins, and the enhanced stability and recyclability of an encapsulated enzyme is demonstrated.     

Hierarchical Assembly of Peptoid‐Based Cylindrical Micelles Exhibiting Efficient Resonance Energy Transfer in Aqueous Solution

Herein we show that by appending bulky β‐cyclodextrin (CD) groups onto sheet‐forming peptoids, we obtain cylindrical micelles that further assembly into membranes and intertwined ribbons on substrates in aqueous solution, depending on the choice of solution and substrate conditions. In situ atomic force microscopy (AFM) shows that micelle assembly occurs in two steps, starting with “precursor” particles that transform into worm‐like micelles, which extend and coalesce to form the higher order structures with a rate and a degree of cooperativity dependent on pH and Ca²⁺ concentration. After co‐assembly with hydrophobic 4‐(2‐hydroxyethylamino)‐7‐nitro‐2,1,3‐benzoxadiazole (NBD) donors that occupy the hydrophobic core, followed by exposure to hydrophilic Rhodamine B as acceptors that insert into cyclodextrin, the micelles exhibit highly efficient Förster resonance energy transfer efficiency in aqueous solution, thereby mimicking natural light harvesting systems.     

Construction of CoO/Co‐Cu‐S Hierarchical Tubular Heterostructures for Hybrid Supercapacitors

Hierarchical hollow structures for electrode materials of supercapacitors could enlarge the surface area, accelerate the transport of ions and electrons, and accommodate volume expansion during cycling. Besides, construction of heterostructures would enhance the internal electric fields to regulate the electronic structures. All these features of hierarchical hollow heterostructures are beneficial for promoting the electrochemical properties and stability of electrode materials for high‐performance supercapacitors. Herein, CoO/Co‐Cu‐S hierarchical tubular heterostructures (HTHSs) composed of nanoneedles are prepared by an efficient multi‐step approach. The optimized sample exhibits a high specific capacity of 320 mAh g^?1 (2300 F g^?1) at 2.0 A g^?1 and outstanding cycling stability with 96.5 % of the initial capacity retained after 5000 cycles at 10 A g^?1. Moreover, an all‐solid‐state hybrid supercapacitor (HSC) constructed with the CoO/Co‐Cu‐S and actived carbon shows a stable and high energy density of 90.7 Wh kg^?1 at a power density of 800 W kg^?1.     

Stable Conversion Chemistry‐Based Lithium Metal Batteries Enabled by Hierarchical Multifunctional Polymer Electrolytes with Near‐Single Ion Conduction

The low Coulombic efficiency and serious safety issues resulting from uncontrollable dendrite growth have severely impeded the practical applications of lithium (Li) metal anodes. Herein we report a stable quasi‐solid‐state Li metal battery by employing a hierarchical multifunctional polymer electrolyte (HMPE). This hybrid electrolyte was fabricated via in situ copolymerizing lithium 1‐[3‐(methacryloyloxy)propylsulfonyl]‐1‐(trifluoromethanesulfonyl)imide (LiMTFSI) and pentaerythritol tetraacrylate (PETEA) monomers in traditional liquid electrolyte, which is absorbed in a poly(3,3‐dimethylacrylic acid lithium) (PDAALi)‐coated glass fiber membrane. The well‐designed HMPE simultaneously exhibits high ionic conductivity (2.24×10^?3 S cm^?1 at 25 °C), near‐single ion conducting behavior (Li ion transference number of 0.75), good mechanical strength and remarkable suppression for Li dendrite growth. More intriguingly, the cation permselective HMPE efficiently prevents the migration of negatively charged iodine (I) species, which provides the as‐developed Li‐I batteries with high capacity and long cycling stability.     

Mesoporous Carbon@Titanium Nitride Hollow Spheres as an Efficient SeS2 Host for Advanced Li–SeS2 Batteries

The introduction of a certain proportion of selenium into sulfur‐based cathodes is an effective strategy for enhancing the integrated battery performance. However, similar to sulfur, selenium sulfide cathodes suffer from poor cycling stability owing to the dissolution of reaction intermediate products. In this study, to exploit the advantages of SeS₂ to the full and avoid its shortcomings, we designed and synthesized a hollow mesoporous carbon@titanium nitride (HMC@TiN) host for loading 70 wt % of SeS₂ as a cathode material for Li–SeS₂ batteries. Benefiting from both physical and chemical entrapment by hollow mesoporous carbon and TiN, the HMC@TiN/SeS₂ cathode manifests high utilization of the active material and excellent cycling stability. Moreover, it exhibits promising areal capacity (up to 4 mAh cm⁻²) with stable cell performance in the high‐mass‐loading electrode.     

Hierarchical Microboxes Constructed by SnS Nanoplates Coated with Nitrogen‐Doped Carbon for Efficient Sodium Storage

The design and synthesis of hierarchical microboxes, assembled from SnS nanoplates coated with nitrogen‐doped carbon (NC) as an anode material for sodium‐ion batteries, is demonstrated. The template‐engaged multistep synthesis of the SnS@NC microboxes involves sequential phase transformation, polydopamine coating, and thermal annealing in N₂. The SnS@NC composite with two‐dimensional nano‐sized subunits rationally integrates several advantages including shortening the diffusion path of electrons/Na⁺ ions, improving electric conductivity, and alleviating volume variation of the electrode material. As a result, the SnS@NC microboxes show efficient sodium storage performance with high capacity, good cycling stability, and excellent rate capability.     

Conductive Microporous Covalent Triazine‐Based Framework for High‐Performance Electrochemical Capacitive Energy Storage

Nitrogen‐enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area (SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane‐derived conductive microporous covalent triazine‐based frameworks (TCNQ‐CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m² g^?1). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g^?1, considerable energy density of 42.8 Wh kg^?1, and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high‐performance electrode material for electrochemical energy‐storage systems.