Enhanced Light-Harvesting and Energy Transfer in Carbon Dots Embedded Thylakoids for Photonic Hybrid Capacitor Applications.

Nanohybrid photosystems have advantages in converting solar energy into electricity, while natural photosystems based solar-powered energy-storage device is still under developed. Here, we fabricate a new kind of photo-rechargeable zinc-ion hybrid capacitor (ZHC) benefiting from light-harvesting carbon dots (CDs) and natural thylakoids for realizing solar energy harvesting and storage simultaneously. Under solar light irradiation, the embedded CDs in thylakoids (CDs/Thy) can convert the less absorbed green light into highly absorbed red light for thylakoids, besides, Förster resonance energy transfer (FRET) between CDs and Thy also occurs, which facilitates the photoelectrons generation during thylakoids photosynthesis, thereby resulting in 6-fold photocurrent output in CDs/Thy hybrid photosystem, compared to pristine thylakoids. Using CDs/Thy as the photocathode in ZHCs, the photonic hybrid capacitor shows photoelectric conversion and storage features. CDs can improve the photo-charging voltage response of ZHCs to ≈1.2 V with a remarkable capacitance enhancement of 144 % under solar light. This study provides a promising strategy for designing plant-based photonic and electric device for solar energy harvesting and storage.

Simultaneous High Ionic Conductivity and Lithium-Ion Transference Number in Single-Ion Conductor Network Polymer Enabling Fast-Charging Solid-State Lithium Battery.

Developing solid-state electrolyte with sufficient ionic conduction and flexible-intimate interface is vital to advance fast-charging solid-state lithium batteries. Solid polymer electrolyte yields the promise of interfacial compatibility, yet its critical bottleneck is how to simultaneously achieve high ionic conductivity and lithium-ion transference number. Herein, single-ion conducting network polymer electrolyte (SICNP) enabling fast charging is proposed to positively realize fast lithium-ion locomotion with both high ionic conductivity of 1.1 × 10-3 S cm-1 and lithium-ion transference number of 0.92 at room temperature. Experimental characterization and theoretical simulations demonstrate that the construction of polymer network structure for single-ion conductor not only facilitates fast hopping of lithium ions for boosting ionic kinetics, but also enables a high dissociation level of the negative charge for lithium-ion transference number close to unity. As a result, the solid-state lithium batteries constructed by coupling SICNP with lithium anodes and various cathodes (e.g., LiFePO4 , sulfur, and LiCoO2 ) display impressive high-rate cycling performance (e.g., 95% capacity retention at 5 C for 1000 cycles in LiFePO4 |SICNP|lithium cell) and fast-charging capability (e.g., being charged within 6 min and discharged over than 180 min in LiCoO2 |SICNP|lithium cell). Our study provides a prospective direction for solid-state electrolyte that meets the lithium-ion dynamics for practical fast-charging solid-state lithium batteries.

Enhancement of Fluorescence Emission for Tricolor Quantum Dots Assembled in Polysiloxane toward Solar Spectrum-Simulated White Light-Emitting Devices.

Commercial white light-emitting diodes (LEDs) have the undesirable characteristics of blue-rich emission and low color rendering index (CRI), while the constituent quantum dots (QDs) suffer from aggregation-induced fluorescence quenching and poor stability. Herein, a strategy is developed to assemble tricolor QDs into a polysiloxane matrix using a polymer-mediated hybrid approach whereby the hybrid composite exhibits a significant enhancement of aggregation-dispersed emission, outstanding photostability, high thermal stability, and outstanding fluorescence recovery. Using the as-prepared hybrid fluorescent materials, the fabricated LEDs exhibit solar spectrum-simulated emission with adjustable Commission Internationale de L'Eclairage coordinates, correlated color temperature, and a recorded CRI of 97. Furthermore, they present no ultraviolet emission and weak blue emission, thus indicating an ideal healthy and high-CRI white LED lighting source.

Unraveling the Correlation between Structures of Carbon Nanospheres Derived from Polymeric Spheres and Their Electrochemical Performance to Achieve High-Rate Supercapacitors.

Understanding correlation between the nanostructure of porous carbons and their ion transport behavior is critical for achieving high-performance supercapacitors. Herein, the relationship between size and shell thickness of carbon nanospheres (CNSs) and capacitive electrochemical performance is clarified. Structural uniform CNSs with controlled diameters, prepared via template-free interfacial copolymerization, are emerging as an ideal platform for investigating the ion transport behavior. It is found that ionic transport is significantly enhanced while the introduction of hollow cores with thinner shell, by virtue of the hollow nanopore-accelerated mass transport to reduce ion diffusion length. The proof-of-concept supercapacitors, constituted of carbons with diameter and shell thickness of 91 and 28 nm, respectively, can maintain highest capacitance retention ratio of 86% at a high sweep rate of 300 mVs-1 , also far outperforming the commercial activated carbon in terms of capacitance, rate capability, and surface efficiency, promising a brilliant application.

Solid-State Carbon Dots with Red Fluorescence and Efficient Construction of Dual-Fluorescence Morphologies.

Stable solid-state red fluorescence from organosilane-functionalized carbon dots (CDs) with sizes around 3 nm is reported for the first time. Meanwhile, a novel method is also first reported for the efficient construction of dual-fluorescence morphologies. The quantum yield of these solid-state CDs and their aqueous solution is 9.60 and 50.7%, respectively. The fluorescence lifetime is 4.82 ns for solid-state CDs, and 15.57 ns for their aqueous solution. These CDs are detailedly studied how they can exhibit obvious photoluminescence overcoming the self-quenching in solid state. Luminescent materials are constructed with dual fluorescence based on as-prepared single emissive CDs (red emission) and nonfluorescence media (starch, Al2 O3 , and RnOCH3 COONa), with the characteristic peaks located at nearly 440 and 600 nm. Tunable photoluminescence can be successfully achieved by tuning the mass ratio of CDs to solid matrix (such as starch). These constructed dual-fluorescence CDs/starch composites can also be applied in white light-emitting diodes with UV chips (395 nm), and oxygen sensing.

Water-Dispersible, Responsive, and Carbonizable Hairy Microporous Polymeric Nanospheres.

Multifunctionalization of microporous polymers is highly desirable but remains a significant challenge, considering that the current microporous polymers are generally hydrophobic and nonresponsive to different environmental stimuli and difficult to be carbonized without damage of their well-defined nanomorphology. Herein, we demonstrate a facile and versatile method to fabricate water-dispersible, pH/temperature responsive and readily carbonizable hairy microporous polymeric nanospheres based on combination of the hyper-cross-linking chemistry with the surface-initiated atom transfer radical polymerization (SI-ATRP). The hyper-cross-linking creates a highly microporous core, whereas the SI-ATRP provides diverse functionalities by surface grafting of hairy functional blocks. The as-prepared materials present multifunctional properties, including sensitive response to pH/temperature, high adsorption capacity toward adsorbates from aqueous solution, and valuable transformation into well-defined microporous carbon nanospheres because of hybrid of carbonizable core and thermo-decomposable protection shell. We hope this strategy could promote the development of both functional microporous polymers and advanced hairy nanoparticles for multipurpose applications.

Synthesis of well-defined microporous carbons by molecular-scale templating with polyhedral oligomeric silsesquioxane moieties.

Formation of a uniform interface between the carbon precursor and the selected template is critical for preparing high-quality nanoporous carbons. It can be accomplished by various templating procedures but still remains a challenge, especially for microporous carbons. A new strategy to fabricate well-defined microporous carbon nanosphere (MCNS) materials via molecular-scale interfacial engineering using an organic/inorganic hybrid molecule as the building block was designed. A commercially available octaphenyl polyhedral oligomeric silsesquioxane was selected as such a building block and transformed into the MCNS products via cross-linking of organic components, followed by carbonization, and subsequent removal of monodispersed silica domains, surrounded by molecular-scale carbon/silica interfaces. The obtained MCNS materials exhibit very large surface area (e.g., 2264 m(2)/g) and fast and selective sorption, and thus demonstrate excellent adsorption and supercapacitance properties. These findings could provide a new benchmark for preparing well-defined nanoporous carbons for various applications.

Tuning the Covalent Coupling Degree between the Cathode and Electrolyte for Optimized Interfacial Resistance in Solid-State Lithium Batteries.

The development of promising solid-state lithium batteries has been a challenging task mainly due to the poor interfacial contact and high interfacial resistance at the electrode/solid-state electrolyte (SSE) interface. Herein, we propose a strategy for introducing a class of covalent interactions with varying covalent coupling degrees at the cathode/SSE interface. This method significantly reduces interfacial impedances by strengthening the interactions between the cathode and SSE. By adjusting the covalent coupling degree from low to high, an optimal interfacial impedance of 33 Ω cm-2 was achieved, which is even lower than the interfacial impedance using liquid electrolytes (39 Ω cm-2). This work offers a fresh perspective on solving the interfacial contact problem in solid-state lithium batteries.

Construction of Mixed Ionic-Electronic Conducting Scaffolds in Zn Powder: A Scalable Route to Dendrite-Free and Flexible Zn Anodes.

Zn powder (Zn-P)-based anodes are considered ideal candidates for Zn-based batteries because they enable a positive synergistic integration of safety and energy density. However, Zn-P-based anodes still experience easy corrosion, uncontrolled dendrite growth, and poor mechanical strength, which restrict their further application. Herein, a mixed ionic-electronic conducting scaffold is introduced into Zn-P to successfully fabricate anti-corrosive, flexible, and dendrite-free Zn anodes using a scalable tape-casting strategy. The as-established scaffold is characterized by robust flexibility, facile scale-up synthesis methodology, and exceptional anti-corrosive characteristics, and it can effectively homogenize the Zn2+ flux during Zn plating/stripping, thus allowing stable Zn cycling. Benefiting from these comprehensive attributes, the as-prepared Zn-P-based anode provides superior electrochemical performance, including long-life cycling stability and high rate capability in practical coin and flexible pouch cells; thus, it holds great potential for developing advanced Zn-ion batteries. The findings of this study provide insights for a promising scalable pathway to fabricate highly efficient and reliable Zn-based anodes and will aid in the realization of advanced flexible energy-storage devices.

Dual carbon and void space confined SiOx/C@void@Si/C yolk-shell nanospheres with high-rate performances and outstanding cyclability for lithium-ion batteries anodes.

Silicon-based anode materials with high theoretical capacity have great challenges of enormous volume expansion and poor electronic conductivity. Herein, a novel dual carbon confined SiOx/C@void@Si/C yolk-shell monodisperse nanosphere with void space have been fabricated through hydrothermal reaction, carbonization, and in-situ low-temperature aluminothermic reduction. Furthermore, the O/Si ratio and void space between SiOx/C core and Si/C shell can be effectively tuned by the length of aluminothermic reduction time. The SiOx/C core plays a role of maintaining the spherical structure and the void space can accommodate the volume expansion of Si. Moreover, the inner and outer carbons not only alleviate volume variation of SiOx and Si but also enhance the electrical conductivity of composites. Benefiting from the synergy of the double carbon and void space, the optimized VSC-14 anode affords prominent cycle stability with reversible capacity of 1094 mAh g-1 after 550 cycles at 200 mA g-1. By pre-lithiation treatment, the VSC-14 achieves an initial Coulombic efficiency of 93.27% at 200 mA g-1 and a reversible capacity of 348 mAh g-1 at 5 A g-1 after 4000 cycles. Furthermore, the pouch cell using VSC-14 anode and LiFePO4 cathode delivers a reversible capacity of 138 mAh g-1 at 0.2C. We hope this strategy can provide a scientific method to synthesis yolk-shell Si-based materials.

Construction of a hierarchical architecture in a wormhole-like mesostructure for enhanced mass transport.

A unique hierarchical architecture is successfully constructed in a wormhole-like mesopore structure via a multiple nanocasting route. This novel type of hierarchical porous carbon (HPC) consists of three-dimensional ordered macropores (ca. 150 nm) with interconnecting pore windows, and the walls of these macropores are rich in wormhole-like mesopores (ca. 2.7 nm) and large spherical mesopores (ca. 10 nm), as well as a significant microporosity, presenting a macro-meso-microporous structure with a three-dimensional interconnectivity. Such a hierarchically porous structure may provide fine diffusion pathways for reaction species, which is demonstrated by the experimental result of an enhanced performance in a supercapacitor. For example, with the introduction of a hierarchical porous structure for fast transport and effective access of ions, the as-prepared HPC exhibits a specific capacitance as high as 247 F g(-1), whereas traditional wormhole-like mesoporous carbon has only a specific capacitance of 176 F g(-1).

Surface chemical functionality of carbon dots: influence on the structure and energy storage performance of the layered double hydroxide.

As a kind of zero-dimensional material, carbon dots (CDs) have become a kind of promising novel material due to their incomparable unique physical and chemical properties. Despite the optical properties of CDs being widely studied, their surface chemical functions are rarely reported. Here we propose an interesting insight into the important role of surface chemical properties of CDs in adjusting the structure of the layered double hydroxide (LDH) and its energy storage performance. It was demonstrated that CDs with positive charge (p-CDs) not only reduce the size of the flower-like LDH through affecting the growth of LDH sheets, but also act as a structure stabilizer. After calcination, the layered double oxide (LDO) maintained the morphology of the LDH and prevented the stacking of layers. And the superiority of the composite in lithium-ion batteries (LIBs) was demonstrated. When used as an anode of LIBs, composites possess outstanding specific capacity, cycle stability and rate performance. It presents the discharge capacity of 1182 mA h g-1 and capacity retention of 94% at the current density of 100 mA g-1 after 100 cycles. Our work demonstrates the important chemical functions of CDs and expands their future applications.

Homogeneous triple-phase interfaces enabling one-pot route to metal compound/carbon composites.

Metal compounds (e.g., metal phosphides/sulfides/selenides) coupled with carbon materials have recently drawn great attraction for boosting the electrochemical performances because of their appealing synergistic effect and valuable structural stability. Despite many examples for their synthesis exist, there is still a need for a simplistic and comprehensive approach to such metal compound/carbon (MC/C) composites. Herein, an effective, facile, yet versatile strategy to produce various types of MC/C composites is presented. Key to this strategy is construction of a homogeneous triple-phase interface, which is realized by utilization of a hybrid assembly integrated with carbon, metal and sulfide (or selenide, phosphide) precursors through coupling metal cations with anion groups of a functional polymer. Such an intimately binding carbon-metal-sulfide (or selenide, phosphide) interface structure enables the successful in situ generation of MC nanoparticles uniformly encapsulated into the carbon matrix just after a one-step carbonization treatment. The present synthetic strategy provides remarkable adjustability, predictability and generality to facilely fabricate a series of MC/C composites, offering sufficient freedom to explore their unique energy storage/conversation properties. As a proof of concept, the as-prepared SnS/C composite exhibits superior lithium ion and potassium ion storage capabilities when used as anode materials for alkali-metal ion batteries. The present work provides impressive insights into the design principles for MC/C composites that are the potential materials in targeted application fields, and opens up an efficacious avenue for their facile synthesis as well.

Propelling electrochemical kinetics of transition metal oxide for high-rate lithium-ion battery through in situ deoxidation.

To engineer advanced anodes for high-rate lithium-ion battery, rational structural design with insightful understanding of rapid reaction kinetics is important and still highly desirable. In this work, a high-temperature in situ deoxidation strategy is used to propel electrochemical kinetics of NiO through incorporating an intrinsic Ni component. Both theoretical calculation and experimental study demonstrate that the Ni-NiO heterojunction significantly enhances the electronic conductivity and ion diffusion properties. Accordingly, the lithium-ion battery modified with the heterostructured Ni-NiO shows remarkably improved charge transfer efficiency and rate performance, substantially outperforming many reported NiO-based anodes. This work opens up the exploration of heterostructured metal compounds as kinetic regulators for high-rate lithium-ion battery and also enlightens the understanding of defect chemistry in propelling electrochemical reactions.

The changing structure by component: Biomass-based porous carbon for high-performance supercapacitors.

In this work, a simple and efficient method is introduced to prepare biomass-based porous carbon with excellent performance by changing the content of component (e.g., cellulose, hemicellulose, lignin, and extractives) of the raw materials. When the content of the components change, the corresponding carbon skeleton will be separated, resulting in a structure that is conducive to activation conditions. Using bagasse with fiber tubular structure as carbon precursor, the synthetic hierarchical porous carbon (BHPC-4) possesses a high specific surface area (SSA) of 3135 m2 g-1 more than the control sample (2484 m2 g-1). Benefitting from the improvement of the structure, the BHPC-4 electrode exhibits an appealing capacitance of 410.5F g-1 at 0.5 A g-1 and long-term cycling stability of 100% capacitance retention after 10,000 cycles in the 6.0 M KOH system. Furthermore, a delightful energy density of 25.6 Wh kg-1 at a 226 W kg-1 can be achieved in 1.8 V Na2SO4 aqueous symmetrical supercapacitors. This method has universal significance in preparing high-porosity and high-performance biomass-based carbon materials for various energy storage/conversion.

Facile construction of uniform ultramicropores in porous carbon for advanced sodium-ion battery.

Facile fabrication of anode materials with low cost, good rate capability and high capacity is a critical factor towards developing sodium-ion battery for practical applications. Herein, a N, O co-doped porous carbon with uniform ultramicropores (NOPC-UM), is synthesized by an in-situ ultramicro templating strategy, and demonstrated as a high-performance sodium-ion storage material. Key to this strategy is employment of an inherent KCl as untramicro template, which leads to formation of uniform size of ultramicropores and heteroatoms (i.e., N and O) doping after high-temperature pyrolysis. The as-constructed NOPC-UM delivers a large capacity of 305 mAh g-1, accompanying with a 93% specific capacity below 1.00 V, and superior cycling stability about 100% after 4000 cycles. These attractive electrochemical performances endow NOPC-UM with impressive potential use as anode materials of sodium-ion battery.

Calcium-chloride-assisted approach towards green and sustainable synthesis of hierarchical porous carbon microspheres for high-performance supercapacitive energy storage.

Spherical carbon materials exhibit great competence as electrode materials for electrochemical energy storage, owing to the high packing density, low surface to volume ratio, and excellent structure stability. How to utilize renewable biomass precursor by green and efficient strategy to fabricate porous carbon microspheres remains a great challenge. Herein, we report a KOH-free and sustainable strategy to fabricate porous carbon microspheres derived from cassava starch with high specific surface area, high yield, and hierarchical structure, in which potassium oxalate monohydrate (K2C2O4·H2O) and calcium chloride (CaCl2) are employed as novel activator. The green CaCl2 activator is crucial to regulate the graphitization degree, specific surface area, and porosity of the carbon microspheres for improving the electrochemical performance. The as-prepared carbon microspheres exhibit high specific surface area (1668 m2 g-1), wide pore size distribution (0.5-60 nm), high carbon content (95%), and exfoliated surface layer. The hierarchical porous carbon microspheres show high specific and areal capacitance (17.1 µF cm-2), superior rate performance, and impressive cycling stability. Moreover, the carbon microspheres based symmetric supercapacitor exhibits high capacitance and excellent cycling performance (100% after 20 000 cycles at a current density of 5 A g-1). This green and novel approach holds great promise to realize low-cost, high-efficient and scalable of renewable cassava starch-derived carbon materials for advanced supercapacitive energy storage applications.

Mild synthesis of superadhesive hydrogel electrolyte with low interfacial resistance and enhanced ionic conductivity for flexible zinc ion battery.

Flexible aqueous battery is considered to be one of the most promising energy storage devices for powering flexible electronics. However, inferior interfacial compatibility in electrode-electrolyte interfaces and inefficient ionic channel of electrolytes usually result in potential troubles when applied in practical applications. Herein, we report a mild synthetic route to a sodium lignosulfonate-polyacrylamide hydrogel electrolyte with a high adhesiveness to achieve low electrode-electrolyte interfacial resistance and fast ionic conduction. Comprehensive experiments show that the catechol groups from sodium lignosulfonate demonstrate strong interactions with both cathode and anode materials, and thus greatly reduce the contact resistances across the electrodes. Meanwhile, the existence of sulfonate groups significantly enhances the ionic conductivity of the hydrogel electrolyte. Benefiting from this design, a low ohmic resistance of 3.8 Ω (i.e., 11.4 Ω cm2 ), a low charge transfer resistance of 22.5 Ω (i.e., 67.5 Ω cm2 ), a high ionic conductivity of 31.1 mS cm-1 as well as a 100% capacity retention upon harsh bending deformation can be realized in the flexible zinc ion battery, which are significantly superior to those in the traditional candidates. The present investigation provides new insight into addressing the interfacial issue plaguing flexible energy storage devices.

A mild method to prepare nitrogen-rich interlaced porous carbon nanosheets for high-performance supercapacitors.

In this work, a non-toxic and mild strategy was presented to efficiently fabricate porous and nitrogen-doped carbon nanosheets. Silkworm cocoon (SCs) acted as carbon source and original nitrogen source. Sodium carbonate (Na2CO3) could facilitate the SCs to expose silk protein and played a catalytic role in the subsequent activation of calcium chloride (CaCl2). Calcium chloride served as pore-making agent. The as-obtained carbon materials with protuberant porous nanosheets exhibit high specific surface area of 731 m2 g-1, rich native nitrogen-doped of 7.91 atomic %, wide pore size distribution from 0.5 to 65 nm, and thus possessing high areal specific capacitances of 34 µF cm-2 as well as excellent retention rate of 97% after 20 000 cycles at a current density of 20 A g-1 in 6 M KOH electrolyte. The assembled carbon nanosheet-based supercapacitor displays a maximum energy density of 21.06 Wh kg-1 at the power density of 225 W kg-1 in 1 M Na2SO4 electrolyte. Experimental results show that a mild and non-toxic treatment of biomass can be an effective and extensible method for preparing optimal porous carbon for electrochemical energy storage.

Boosting zinc ion energy storage capability of inert MnO cathode by defect engineering.

Aqueous zinc ion battery constitutes a safe, stable and promising next-generation energy storage device, but suffers the lack of suitable host compounds for zinc ion storage. Development of a facile way to emerging cathode materials is strongly requested toward superior electrochemical activities and practical applications. Herein, defect engineering, i.e., simultaneous introduction of nitrogen dopant and oxygen vacancy into commercial and low-cost MnO, is proposed as a positive strategy to activate the originally inert phase for kinetically propelling its zinc ion storage capability. Both experimental characterization and theoretical calculations demonstrate that the nitrogen dopant significantly improves the electric conductivity of electrochemical inert MnO. Simultaneously, the oxygen vacancy creates sufficient large inserted channels and available activated adsorption sites for zinc ions storage. These synergistic structural advantages obviously ameliorate the electrochemical performance of inert MnO. Therefore, even without any conductive agent additive, the as-prepared material shows high specific capacity, superb rate capability, prolonged cycling stability and attractive energy density, which are dramatically superior to those of the pristine MnO as well as many other host cathode materials. This work presents fresh insights on the role of defect engineering in the enhancement of the intrinsic electrochemical reactivity of inert cathode, and an effective strategy for scalable fabrication of high-performance cathode for zinc ion battery.