Wireless Sensor System Based on Organohydrogel Ionic Skin for Physiological Activity Monitoring.

Supermolecular hydrogel ionic skin (i-skin) linked with smartphones has attracted widespread attention in physiological activity detection due to its good stability in complex scenarios. However, the low ionic conductivity, inferior mechanical properties, poor contact adhesion, and insufficient freeze resistance of most used hydrogels limit their practical application in flexible electronics. Herein, a novel multifunctional poly(vinyl alcohol)-based conductive organohydrogel (PCEL5.0%) with a supermolecular structure was constructed by innovatively employing sodium carboxymethyl cellulose (CMC-Na) as reinforcement material, ethylene glycol as antifreeze, and lithium chloride as a water retaining agent. Thanks to the synergistic effect of these components, the PCEL5.0% organohydrogel shows excellent performance in terms of ionic conductivity (1.61 S m-1), mechanical properties (tensile strength of 70.38 kPa and elongation at break of 537.84%), interfacial adhesion (1.06 kPa to pig skin), frost resistance (-50.4 °C), water retention (67.1% at 22% relative humidity), and remoldability. The resultant PCEL5.0%-based i-skin delivers satisfactory sensitivity (GF = 1.38) with fast response (348 ms) and high precision under different deformations and low temperature (-25 °C). Significantly, the wireless sensor system based on the PCEL5.0% organohydrogel i-skin can transmit signals from physiological activities and sign language to a smartphone by Bluetooth technology and dynamically displays the status of these movements. The organohydrogel i-skin shows great potential in diverse fields of physiological activity detection, human-computer interaction, and rehabilitation medicine.

Interfacial Domino Effect Triggered by ß-alanine Cations Realized Highly Reversible Zinc-Metal Anodes.

Realizing durative dense, dendrite-free, and no by-product deposition configuration on Zn anodes is crucial to solving the short circuit and premature failure of batteries, which is simultaneously determined by the Zn interface chemistry, electro-reduction kinetics, mass transfer process, and their interaction. Herein, this work unmasks a domino effect of the ß-alanine cations (Ala+) within the hydrogel matrix, which effectively triggers the subsequent electrostatic shielding and beneficial knock-on effects via the specifical adsorption earliest event on the Zn anode surface. The electrostatic shielding effect regulates the crystallographic energetic preference of Zn deposits and retards fast electro-reduction kinetics, thereby steering stacked stockier block morphology and realizing crystallographic optimization. Meanwhile, the mass transfer rate of Zn2+ ions was accelerated via the SO42- anion immobilized caused by Ala+ in bulk electrolyte, finally bringing the balance between electroreduction kinetics and mass transfer process, which enables dendrite-free Zn deposition behavior. Concomitantly, the interfacial adsorbed Ala+ cations facilitate the electrochemical reduction of interfacial SO42- anions to form the inorganic-organic hybrid solid electrolyte interphase layer. The above domino effects immensely improve the utilization efficiency of Zn anodes and long-term stability, as demonstrated by the 12 times longer life of Zn||Zn cells (3650 h) and ultrahigh Coulombic efficiency (99.4%).

Tailoring vanadium oxide crystal orientation for high-performance aqueous zinc-ion batteries.

Due to the increasing demand for higher security and low-cost energy storage systems, the main research focus has been developing a suitable substitute for lithium-ion batteries. Aqueous zinc ion batteries (AZIBs) are considered the best alternative to lithium-ion batteries in large-scale energy storage devices. Owing to its high capacity, vanadate is a promising cathode material for AZIBs. The crystallographic orientation of cathode materials dramatically influences the rate performance and cycling life. Here, Mg0.57V5O12·2.3H2O (MgVO) with favorable (001) crystal orientation and significantly improved electrochemical performance is prepared by a simple stirring method. The crystal growth orientations of MgVO are altered by adjusting the aging time of the reactant solution. The (001)-orientated grain growth of MgVO delivers a 232.5 mA h g-1 capacity at 5 A g-1 with a 94% capacity retention rate after 1400 cycles. The zinc ion storage performance of MgVO demonstrates that the orientation-controlled method can design effective cathode materials for high-performance ZIBs.

Oxygen-enriched pitch-derived hierarchically porous carbon toward boosted zinc-ion storage performance.

The lack of cathode materials with satisfactory Zn2+ storage capability substantially hinders the realization of high-performance aqueous zinc-ion hybrid capacitors (ZHCs). Herein, we propose a facile KMnO4 template-assisted KOH activation strategy to prepare a novel oxygen-enriched hierarchically porous carbon (HPC-1-4). This strategy efficiently converts coal tar pitch (CTP) into a well-tuned carbon material with a large specific surface area of 3019 m2 g-1 and a high oxygen content of 9.20 at%, which is conducive to providing rich active sites, rapid charge transport, and appreciable pseudocapacitance for Zn-ion storage. Thus, the as-fabricated HPC-1-4-based aqueous ZHC exhibits prominent performance, including a high gravimetric capacity (206.7 mAh g-1 at 0.25 A g-1), a remarkable energy density (153.4 Wh kg-1 at 184.2 W kg-1), and an impressive power output (15240 W kg-1 at 63.5 Wh kg-1). In-depth ex-situ characterizations indicate that the excellent electrochemical properties of ZHCs are due to the synergistic effect of the Zn2+ adsorption mechanism and reversible chemisorption. In addition, the assembled quasi-solid-state device demonstrates excellent electrochemical stability of up to 100% capacity retention over 50000 cycles, accompanied with a desirable energy density of 115.6 Wh kg-1. The facile preparation method of converting CTP into carbonaceous functional materials has advanced the development of efficient and eco-friendly energy storage technologies.

Realizing Ultrafast and Robust Sodium-Ion Storage of Iron Sulfide Enabled by Heteroatomic Doping and Regulable Interface Engineering.

Fe-based sulfides are a promising type of anode material for sodium-ion batteries (SIBs) due to their high theoretical capacities and affordability. However, these materials often suffer from issues such as capacity deterioration and poor conductivity during practical application. To address these challenges, an N-doped Fe7S8 anode with an N, S co-doped porous carbon framework (PPF-800) was synthesized using a template-assisted method. When serving as an anode for SIBs, it delivers a robust and ultrafast sodium storage performance, with a discharge capacity of 489 mAh g-1 after 500 cycles at 5 A g-1 and 371 mAh g-1 after 1000 cycles at 30 A g-1 in the ether-based electrolyte. This impressive performance is attributed to the combined influence of heteroatomic doping and adjustable interface engineering. The N, S co-doped carbon framework embedded with Fe7S8 nanoparticles effectively addresses the issues of volumetric expansion, reduces the impact of sodium polysulfides, improves intrinsic conductivity, and stimulates the dominant pseudocapacitive contribution (90.3% at 2 mV s-1). Moreover, the formation of a stable solid electrolyte interface (SEI) film by the effect of uniform pore structure in ether-based electrolyte produces a lower transfer resistance during the charge-discharge process, thereby boosting the rate performance of the electrode material. This work expands a facile strategy to optimize the electrochemical performance of other metal sulfides.

Synergistic Structure and Iron-Vacancy Engineering Realizing High Initial Coulombic Efficiency and Kinetically Accelerated Lithium Storage in Lithium Iron Oxide.

Transition metal oxides with high capacity still confront the challenges of low initial coulombic efficiency (ICE, generally <70%) and inferior cyclic stability for practical lithium-storage. Herein, a hollow slender carambola-like Li0.43 FeO1.51 with Fe vacancies is proposed by a facile reaction of Fe3+ -containing metal-organic frameworks with Li2 CO3 . Synthesis experiments combined with synchrotron-radiation X-ray measurements identify that the hollow structure is caused by Li2 CO3 erosion, while the formation of Fe vacancies is resulted from insufficient lithiation process with reduced Li2 CO3 dosage. The optimized lithium iron oxides exhibit remarkably improved ICE (from 68.24% to 86.78%), high-rate performance (357 mAh g-1 at 5 A g-1 ), and superior cycling stability (884 mAh g-1 after 500 cycles at 0.5 A g-1 ). Paring with LiFePO4 cathodes, the full-cells achieve extraordinary cyclic stability with 99.3% retention after 100 cycles. The improved electrochemical performances can be attributed to the synergy of structural characteristics and Fe vacancy engineering. The unique hollow structure alleviates the volume expansion of Li0.43 FeO1.51 , while the in situ generated Fe vacancies are powerful for modulating electronic structure with boosted Li+ transport rate and catalyze more Li2 O decomposition to react with Fe in the first charge process, hence enhancing the ICE of lithium iron oxide anode materials.

Amorphous Heterostructure Derived from Divalent Manganese Borate for Ultrastable and Ultrafast Aqueous Zinc Ion Storage.

Aqueous zinc-manganese (Zn-Mn) batteries have promising potential in large-scale energy storage applications since they are highly safe, environment-friendly, and low-cost. However, the practicality of Mn-based materials is plagued by their structural collapse and uncertain energy storage mechanism upon cycling. Herein, this work designs an amorphous manganese borate (a-MnBOx ) material via disordered coordination to alleviate the above issues and improve the electrochemical performance of Zn-Mn batteries. The unique physicochemical characteristic of a-MnBOx enables the inner a-MnBOx to serve as a robust framework in the initial energy storage process. Additionally, the amorphous manganese dioxide, amorphous Znx MnO(OH)2 , and Zn4 SO4 (OH)6 ·4H2 O active components form on the surface of a-MnBOx during the charge/discharge process. The detailed in situ/ex situ characterization demonstrates that the heterostructure of the inner a-MnBOx and surface multicomponent phases endows two energy storage modes (Zn2+ /H+ intercalation/deintercalation process and reversible conversion mechanism between the Znx MnO(OH)2 and Zn4 SO4 (OH)6 ·4H2 O) phases). Therefore, the obtained Zn//a-MnBOx battery exhibits a high specific capacity of 360.4 mAh g-1 , a high energy density of 484.2 Wh kg-1 , and impressive cycling stability (97.0% capacity retention after 10 000 cycles). This finding on a-MnBOx with a dual-energy storage mechanism provides new opportunities for developing high-performance aqueous Zn-Mn batteries.

Manipulating Deposition Behavior by Polymer Hydrogel Electrolyte Enables Dendrite-Free Zinc Anode for Zinc-Ion Hybrid Capacitors.

Rechargeable aqueous zinc-ion hybrid capacitors (ZHCs) have aroused unprecedented attention because of their high safety, cost effectiveness, and environmental compatibility. However, the intractable issues of dendrite growth and side reactions at the electrode-electrolyte interface deteriorate durability and reversibility of Zn anodes, deeply encumbering the large-scale application of ZHCs. Concerning these obstacles, a negatively charged carboxylated chitosan-intensified hydrogel electrolyte (CGPPHE) with cross-linked networks is reported to stabilize Zn anodes. Beyond possessing good mechanical characteristics, the CGPPHE with polar groups can reduce the desolvation energy barrier of hydrated Zn2+ , constrain the 2D Zn2+ diffusion, and uniformize electric field and Zn2+ flux distributions, assuring dendrite-free Zn deposition with high plating-stripping efficiency. Concurrently, the hydrophilic CGPPHE alleviates harmful hydrogen evolution and corrosion by abating water activity. Accordingly, Zn|CGPPHE|Zn and Zn|CGPPHE|Cu cells exhibit an extended life exceeding 350 h (1600 mAh cm-2 cumulative capacity under 20 mA cm-2 ) and a high average coulombic efficiency of 98.2%, respectively. The resultant flexible ZHCs with CGPPHE and template-regulated carbon cathode present perfect properties in capacity retention (97.7% over 10 000 cycles), energy density (91.8 Wh kg-1 ), and good mechanical adaptability. This study provides insight into developing novel hydrogel electrolytes toward highly rechargeable and stable ZHCs.

Ni activated Mo2C by regulating the interfacial electronic structure for highly efficient lithium-ion storage.

Regulating the electronic structure plays a positive role in improving the ion/electron kinetics of electrode materials for lithium ion batteries (LIBs). Herein, an effective approach is demonstrated to achieve Ni/Mo2C hybrid nanoparticles embedded in porous nitrogen-doped carbon nanofibers (Ni/Mo2C/NC). Density functional theory calculations indicate that Ni can activate the interface of Ni/Mo2C by regulating the electronic structure, and accordingly improve the electron/Li-ion diffusion kinetics. The charge at the interface transfers from Ni atoms to Mo atoms on the surface of Mo2C, illustrating the formation of an interfacial electric field in Ni/Mo2C. The formed interfacial electric field in Ni/Mo2C can improve the intrinsic electronic conductivity, and reduce the Li adsorption energy and the Li+ diffusion barrier. Thus, the obtained Ni/Mo2C/NC shows an excellent high-rate capability of 344.1 mA h g-1 at 10 A g-1, and also displays a superior cyclic performance (remaining at 412.7 mA h g-1 after 1800 cycles at 2 A g-1). This work demonstrates the important role of electronic structure regulation by assembling hybrid materials and provides new guidance for future work on designing novel electrode materials for LIBs.

Regulating the electronic structure of MoO2/Mo2C/C by heterostructure and oxygen vacancies for boosting lithium storage kinetics.

The electronic structure regulation of electrode materials can improve the ion/electron kinetics, which is beneficial to the cyclic performance and rate capability for lithium ion batteries (LIBs). Herein, we propose a facile strategy to achieve a MoO2/Mo2C/C heterostructure with abundant oxygen vacancies. Density functional theory calculations indicate that the heterostructure of MoO2/Mo2C/C can significantly promote the Li+/charge transfer and reduce the Li adsorption energy, and the abundant oxygen vacancies in MoO2/Mo2C/C can improve the intrinsic electronic conductivity and reduce the Li+ diffusion barrier. Benefiting from the multiscale coordinated regulation, the obtained MoO2/Mo2C/C film exhibits outstanding high rate capability (454.7 mA h g-1 at 5 A g-1) and remarkable cyclic performance (retaining 569 mA h g-1 over 1000 cycles at 2 A g-1). The insightful findings in this study can shed light on the behavior of the electron/ion structure regulation by the heterostructure and oxygen vacancies, which can guide future studies on designing other electrode materials with high-performance lithium-ion storage.

Natural Polysaccharide Strengthened Hydrogel Electrolyte and Biopolymer Derived Carbon for Durable Aqueous Zinc Ion Storage.

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) represent one of the current research subjects because of their flame retardancy, ease of manufacturing, and exceptional roundtrip efficiency. With the evolution into real useful energy storage cells, the bottleneck factors of the corrosion and dendrite growth problems must be properly resolved for largely boosting their cycling life and energy efficiency. Herein, a natural polysaccharide strengthened hydrogel electrolyte (denoted as PAAm/agar/Zn(CF3SO3)2) was engineered by designing an asymmetric dual network of covalently cross-linked polyacrylamide (denoted as PAAm) and physically cross-linked loose polysaccharide (e.g., agar) followed by intense uptake of Zn(CF3SO3)2 aqueous electrolyte. In this polymeric matrix, the PAAm chains are responsible for constructing the soft domains to immobilize the water molecules, and the agar component boosts the mechanical performance (by using its inherent reversible sacrificial bonds) and favors the electrolyte ion transport. Due to these reasons, the as-designed hydrogel electrolyte effectively inhibits the zinc dendrite growth, realizes the uniform Zn deposition, and affords a satisfactory ionic conductivity of 1.55 S m-1, excellent tensile strength (78.9 kPa at 507.7% stretchable), and high compression strength (118.0 kPa at 60.0% strain). Additionally, a biopolymer-derived N-doped carbon microsphere cathode material with a highly interconnected porous carbonaceous network (denoted as NC) was also synthesized, which delivers a high capacity of 92.8 mAh g-1, along with superb rate capability and long duration cycling lifespan (95.4% retention for 10000 cycles) in the aqueous Zn//NC ZHSC. More notably, with integrated merits of the PAAm/agar/Zn(CF3SO3)2 hydrogel electrolyte and NC, the as-built quasi-solid-state ZHSC achieves a high specific capacity of 73.4 mAh g-1 and superior energy density of 61.3 Wh kg-1 together with excellent cycling stability for 10000 cycles. This work demonstrated favorable practicability in the structural design of the hydrogel electrolytes and electrode materials for advanced ZHSC applications.

Freeze-Tolerant Hydrogel Electrolyte with High Strength for Stable Operation of Flexible Zinc-Ion Hybrid Supercapacitors.

Constructing ionic conductive hydrogels with diversified properties is crucial for portable zinc-ion hybrid supercapacitors (ZHSCs). Herein, a freeze-tolerant hydrogel electrolyte (AF PVA-CMC/Zn(CF3 SO3 )2 ) is developed by forming a semi-interpenetrating anti-freezing polyvinyl alcohol-carboxymethyl cellulose (AF PVA-CMC) network filled with the ethylene glycol (EG)-containing Zn(CF3 SO3 )2 aqueous solution. The semi-interpenetrating AF PVA-CMC/Zn(CF3 SO3 )2 possesses enhanced mechanical properties, realizes the uniform zinc deposition, and impedes the dendrite growth. Notably, the interaction between PVA and EG suppresses the ice crystal formation and prevents freezing at -20 °C. Due to these advantages, the designed hydrogel owns high ionic conductivity of 1.73/0.75 S m-1 at 20/-20 °C with excellent tensile/compression strength at 20 °C. Impressively, the flexible AF quasi-solid-state ZHSC employing the hydrogel electrolyte achieves a superior energy density at 20/-20 °C (87.9/60.7 Wh kg-1 ). It maintains nearly 84.8% of the initial capacity after 10 000 cycles and a low self-discharge rate (1.77 mV h-1 ) at 20 °C, together with great tolerance to corrosion. Moreover, this device demonstrates a stable electrochemical performance at -20 °C under deformation. The obtained results provide valuable insights for constructing durable hydrogel electrolytes in cold environments.

Kinetics-Favorable Ultrathin NiCo-MOF Nanosheets with Boosted Pseudocapacitive Charge Storage for Quasi-Solid-State Hybrid Supercapacitors.

Bimetallic metal-organic frameworks (MOFs) with an ultrathin configuration are compelling materials for developing high-performance energy storage devices on account of their unique structural merits. Herein, a hydrangea-like NiCo-MOF is well prepared using controllable solvothermal and cation-exchange processes, synchronously achieving bimetallic nodes and hierarchical ultrathin architecture. The structural superiority enables NiCo-MOF of expanded electrons' transfer pathways and multitudinous electrolytes' diffusion channels, resulting in a significant enhancement in pseudocapacitive performance. Coupling with the bimetallic nature and constructional advantages, NiCo-MOF shows superior gravimetric capacity (832.6 C g-1 at 1 A g-1) and electrochemical kinetics to those of monometallic Ni-MOF and Co-MOF. Importantly, the quasi-solid-state hybrid supercapacitor (HSC) based on the NiCo-MOF cathode and active carbon (AC) anode delivers a desirable energy density (45.3 Wh kg-1 at 847.8 W kg-1), a favorable power density (7160.0 W kg-1 at 23.3 Wh kg-1), a remarkable cyclability (82.4% capacity retention over 7000 cycles), and a capability of driving miniature electronics, exhibiting its potential in practical applications. This work presents an efficient design strategy to develop kinetics-favorable MOF materials for energy storage.

Encoding Enantiomeric Molecular Chiralities on Graphene Basal Planes.

Graphene has demonstrated broad applications due to its prominent properties. Its molecular structure makes graphene achiral. Here, we propose a direct way to prepare chiral graphene by transferring chiral structural conformation from chiral conjugated amino acids onto graphene basal plane through π-π interaction followed by thermal fusion. Using atomic resolution transmission electron microscopy, we estimated an areal coverage of the molecular imprints (chiral regions) up to 64 % on the basal plane of graphene (grown by chemical vapor deposition). The high concentration of molecular imprints in their single layer points to a close packing of the deposited amino acid molecules prior to "thermal fusion". Such "molecular chirality-encoded graphene" was tested as an electrode in electrochemical enantioselective recognition. The chirality-encoded graphene might find use for other chirality-related studies and the encoding procedure might be extended to other two-dimensional materials.

Controlled Synthesis of Ultrafine ß-Mo2C Nanoparticles Encapsulated in N-Doped Porous Carbon for Boosting Lithium Storage Kinetics.

Rational construction of anode material architecture to afford excellent cycling stability, fast rate capacity, and large specific capacity is essential to promote further development of lithium-ion batteries in commercial applications. In this work, we propose a facile strategy to anchor ultrafine ß-Mo2C nanoparticles in N-doped porous carbon skeleton (ß-Mo2C@NC) using a scalable salt-template method. The well-defined and abundant hierarchical porous structure of ß-Mo2C@NC can not only significantly enhance the electron/ion transfer but also markedly increase the specific surface area to effectively expose the electrochemically accessible active sites. Besides, the N-doped carbon matrix can turn the d-orbital electrons of the Mo to boost the electron transportation as well as distribute active sites to buffer the volume change of Mo2C and provide conductive pathways during discharge/charge cycles. As a result, the as-prepared ß-Mo2C@NC displays excellent lithium storage performance in terms of 1701.6 mA h g-1 at 0.1 A g-1 after 100 cycles and a large capacity of 816.47 mA h g-1 at 2.0 A g-1 after 500 cycles. The above results distinctly demonstrate that the ß-Mo2C@NC composite has potential application as anode materials in high-performance energy storage devices.

A safe and robust dual-network hydrogel electrolyte coupled with multi-heteroatom doped carbon nanosheets for flexible quasi-solid-state zinc ion hybrid supercapacitors.

Aqueous zinc ion hybrid supercapacitors (ZHSCs) are receiving increasing research interest because of their superiority in safety, economy, and high water compatibility. However, the corrosion problems coupled with dendrite growth in an aqueous system severely limit the potential use of zinc storage systems with long service life. To delicately address the above obstacles, a κ-carrageenan/polyacrylamide/Zn(CF3SO3)2 hydrogel electrolyte (denoted as κ-CG/PAAm/Zn(CF3SO3)2) with an ionically and covalently double crosslinked network was constructed, which possesses a high ionic conductivity of 2.3 S m-1, a high tensile strength of 34.6 kPa with a superior stretchability of 599.0%, and an excellent compression strength of 75.3 kPa at 75.0% strain. The double crosslinked polymer chains realize uniform zinc deposition. In addition, the intrinsic hydrophilic groups in the κ-carrageenan (κ-CG) and polyacrylamide (PAAm) chains can well immobilize water molecules, which favor electrolyte ion transport. Moreover, nitrogen and sulphur co-doped carbon nanosheets (denoted as ACNS) characterized by the rich amorphous phase associated with lots of short-range ordered microcrystalline regions were prepared as the cathode material in this work, which exhibits a high capacity of 116.4 mA h g-1 coupled with superior rate performance and long-term cycling stability (108.0% capacity retention over 10 000 cycles) for an aqueous Zn//ACNS ZHSC. A quasi-solid-state ZHSC based on ACNS and κ-CG/PAAm/Zn(CF3SO3)2 exhibits a specific capacity of 100.5 mA h g-1 at 0.25 A g-1 with a high capacity retention of 50.8% at 20 A g-1. The as-fabricated ZHSC also shows excellent cycling stability of 10 000 cycles as well as a superior energy density of 86.5 W h kg-1 at a power density of 215.3 W kg-1. The ZHSC can also be used as a reliable source to drive various kinds of electronics (e.g., mobile phones and electronic timers), which uncovers a feasible strategy for engineering the high-performance hydrogel electrolytes and cathode materials for ZHSC applications.

Oriented Nanosheet-Assembled CoNi-LDH Cages with Efficient Ion Diffusion for Quasi-Solid-State Hybrid Supercapacitors.

Fast-charged energy-storage technologies have become important nowadays as they are required by many applications, including automobiles. This inspires the exploitation of hybrid supercapacitors (HSCs) with the advantages of fast charge offered by the capacitor characters and high energy density from the property of battery technology. The challenges lay in the construction of advanced materials with high pseudocapacitive activity. Herein, a metal-organic framework derivative is utilized to address the problems. Specifically, polyhedral CoNi layered double hydroxide (CoNi-LDHx) cages assembled in the form of nanosheet arrays are prepared from ZIF-67 using a facile ion-exchange approach. Based on the control over the mass ratio of ZIF-67 to Ni salt, the optimal CoNi-LDH2 is attained. It exhibits ultrahigh capacities ranging from 1031.4 to 667.3 C g-1 under 1-25 A g-1, thanks to rich Faradaic active spots and the accelerated kinetics provided by the synergy between nanosheet arrays and the hollow structure. The CoNi-LDH2-based HSC with the gel electrolyte shares remarkable energy output of 49 Wh kg-1 and approving cyclability with almost no capacity decay after 12 000 cycles. This is an advancement vs many related studies and can arouse tremendous interests of researchers in solving the main problems of energy storage.

Phosphate-modified Co-Ni phosphide heterostructure formed by interfacial and electronic tuning for boosted faradaic properties.

Rational structural and compositional modulation endows electrode materials with unique physicochemical characteristics due to their adjustable electronic properties. Herein, a phosphate-modified hierarchical nanoarray consisting of a heterojunction with a well-aligned cobalt phosphide nanowire core and nickel phosphide nanosheet shell on flexible carbon cloth (denoted as CoP@Ni2P-CC) is engineered. The phosphate-modulated heterogeneous phosphide with a tuned electronic structure, additional heterojunction interfaces, and high degree of covalency in the chemical bonds accelerates the reaction kinetics and enhances the energy storage performance. Due to these reasons, the as-obtained phosphide-based heterostructured CoP@Ni2P-CC electrode delivers a capacity of 475.9 C g-1 at 0.5 A g-1 with a satisfying rate capability, which is greatly superior to that of its transition metal counterparts (sulfide, selenide, and oxide). After being assembled into a flexible hybrid supercapacitor (FHSC), a wide operating voltage (1.8 V), high energy/power densities (49.8 W h kg-1/8.6 kW kg-1), and long-term stability (85.1% capacity retention after 10 000 cycles) were achieved. This work may provide a general method from multiple strategies for designing reliable pseudocapacitive materials for flexible electronics.

Design and Fabrication of Hierarchical NiCoP-MOF Heterostructure with Enhanced Pseudocapacitive Properties.

Metal-organic framework (MOF)-derived heterostructures possessing the merits of each component are thought to display the enhanced energy storage performance due to their synergistic effect. Herein, a functional heterostructure (NiCoP-MOF) composed of nickel/cobalt-MOF (NiCo-MOF) and phosphide (NiCoP) is designed and fabricated via the localized phosphorization of unusual lamellar brick-stacked NiCo-MOF assemblies obtained by a hydrothermal method. The experimental and computational analyses reveal that such-fabricated heterostructures possess the modulated electronic structure, abundant active sites, and hybrid crystalline feature, which is kinetically beneficial for fast electron/ion transport to enhance the charge storage capability. Examined as the supercapacitor electrode, the obtained NiCoP-MOF compared to the NiCo-MOF delivers a high capacity of 728 C g-1 (1.82 C cm-2 ) at 1 A g-1 with a high capacity retention of 430 C g-1 (1.08 C cm-2 ) when increasing the current density to 20 A g-1 . Importantly, the assembled solid-state NiCoP-MOF-based hybrid supercapacitor displays superior properties regarding the capacity (226.3 C g-1 ), energy density (50.3 Wh kg-1 ), and durability (≈100% capacity retention over 10 000 cycles). This in situ heterogenization approach sheds light on the electronic structure modulation while maintaining the well-defined porosity and morphology, holding promise for designing MOF-based derivatives for high performance energy storage devices.

Engineering Kinetics-Favorable Carbon Sheets with an Intrinsic Network for a Superior Supercapacitor Containing a Dual Cross-linked Hydrogel Electrolyte.

Despite the physicochemical advantages of two-dimensional (2D) carbons for supercapacitors, the inappropriate texture within 2D carbon materials suppresses the charge storage capability. Reported here are heteroatom-rich carbon sheets with the overall network engineered by molecular structure modulation and subsequent chemical activation of a three-dimensional (3D) cross-linked polymer. The 3D-to-2D reconstruction mechanism is unveiled. The architecture with a large active surface, fully interpenetrating and conductive network, and rich surface heteroatoms relieves well the ionic diffusion restriction within thick sheets and reduces the overall resistance, exhibiting fast transport kinetics and excellent stability. Indeed, high gravimetric capacitance (281.1 F g-1 at 0.5 A g-1), ultrahigh retention rate (92.5% at 100 A g-1), and impressive cyclability (89.7% retention after 20 000 cycles) are achieved by this material. It also possesses a high areal capacitance of 3.56 F cm-2 at 0.5 A g-1 under a high loading of 25 mg cm-2. When coupled with the developed dual cross-linked hydrogel electrolyte (Al-alginate/poly(acrylamide)/sodium sulfate), a quasi-solid-state supercapacitor delivers an energy density of 28.3 Wh kg-1 at 250.1 W kg-1, which is significantly higher than those of some reported aqueous carbon-based symmetric devices. Moreover, the device displays excellent durability over 10 000 charge/discharge cycles. The proposed cross-linked polymer strategy provides an efficient platform for constructing dynamics-favorable carbon architectures and attractive hydrogel electrolytes toward improved energy supply devices.