A Safe Flexible Self-Powered Wristband System by Integrating Defective MnO2-x Nanosheet-Based Zinc-Ion Batteries with Perovskite Solar Cells

A multifunctional phenylphosphinamide additive for stable flexible inverted perovskite solar cells

The multifunctional phenylphosphinamide additive is used in flexible inverted perovskite solar cells to release tensile strain and increase the toughness of the perovskite film, achieving enhanced device efficiency and stability.

Poly(3,4-ethylenedioxythiophene)-Coated Vanadium-Doped MnO2 Nanorods for High-Performance Flexible Aqueous Zinc-Ion Battery Cathode

Manganese-based aqueous zinc-ion batteries (AZIBs) are considered promising cathode materials for large-scale energy storage applications due to their low cost and high safety. However, the primary constraints on achieving high specific capacity and cycling stability are the inherent low conductivity and suboptimal structural stability of the AZIB cathodes. Herein, we report a high-performance poly(3,4-ethylenedioxythiophene) (PEDOT)-coated vanadium-doped MnO2 nanorod (NR) electrode for AZIBs. First, vanadium-doped MnO2 (V-MnO2) NRs were synthesized by a simple hydrothermal synthesis method. The V-MnO2 NRs were further encapsulated with a nanolayer of PEDOT through an in situ polymerization process, which was subsequently treated with sulfuric acid to achieve a smooth surface. The V doping creates oxygen vacancies within the MnO2, allowing for the rapid embedding and diffusion of Zn2+. The PEDOT nanolayer greatly enhances the conductivity and structural stability of the V-MnO2. Benefiting from the unique features, an optimal composite NRs electrode exhibits a high specific capacity of 250 mAh g-1 at 0.4 A g-1, a high energy density (388 Wh kg-1 at 151 W kg-1), and excellent stability over 5000 cycles at 3 A g-1. In addition, the flexible pouch cell assembled with the electrode shows good stability under bending. Given the positive outcomes, the material holds great potential for use as a cathode in next-generation flexible energy storage systems.

Customization of Manganese Oxide Cathodes via Precise Electrochemical Lithium-Ion Intercalation for Diverse Zinc-Ion Batteries

Manganese oxide-based aqueous zinc-ion batteries (ZIBs) are attractive energy storage devices, owing to their good safety, low cost, and ecofriendly features. However, various critical issues, including poor conductivity, sluggish reaction kinetics, and unstable structure still restrict their further development. Oxygen defect engineering is an effective strategy to improve the electrochemical performance of manganese oxides, but challenging in the accurate regulation of oxygen defects. In this work, an effective and controllable defect engineering strategy-controllable electrochemical lithium-ion intercalation - is proposed to tackle this issue. The incorporation of lithium ions and oxygen defects can promote the conductivity, lattice spacing, and structural stability of Mn2O3 (MO), thus improving its capacity (232.7 mAh g-1), rate performance, and long-term cycling stability (99.0% capacity retention after 3000 cycles). Interestingly, the optimal ratio of intercalated lithium-ion varies at different temperature or mass-loading of MO, which provides the possibility to customize diverse ZIBs to meet different application conditions. In addition, the fabricated ZIBs present good flexibility, superior safety, and admirable adaptability under extreme temperatures (-20-100 °C). This work provides an inspiration on the structural customization of metal oxide nanomaterials for diverse ZIBs, and sheds light on the construction of future portable electronics.

An ultraflexible energy harvesting-storage system for wearable applications

The swift progress in wearable technology has accentuated the need for flexible power systems. Such systems are anticipated to exhibit high efficiency, robust durability, consistent power output, and the potential for effortless integration. Integrating ultraflexible energy harvesters and energy storage devices to form an autonomous, efficient, and mechanically compliant power system remains a significant challenge. In this work, we report a 90 µm-thick energy harvesting and storage system (FEHSS) consisting of high-performance organic photovoltaics and zinc-ion batteries within an ultraflexible configuration. With a power conversion efficiency surpassing 16%, power output exceeding 10 mW cm-2, and an energy density beyond 5.82 mWh cm-2, the FEHSS can be tailored to meet the power demands of wearable sensors and gadgets. Without cumbersome and rigid components, FEHSS shows immense potential as a versatile power source to advance wearable electronics and contribute toward a sustainable future.

Flexible electrochemical energy storage devices and related applications: recent progress and challenges

Given the escalating demand for wearable electronics, there is an urgent need to explore cost-effective and environmentally friendly flexible energy storage devices with exceptional electrochemical properties. However, the existing types of flexible energy storage devices encounter challenges in effectively integrating mechanical and electrochemical performances. This review is intended to provide strategies for the design of components in flexible energy storage devices (electrode materials, gel electrolytes, and separators) with the aim of developing energy storage systems with excellent performance and deformability. Firstly, a concise overview is provided on the structural characteristics and properties of carbon-based materials and conductive polymer materials utilized in flexible energy storage devices. Secondly, the fabrication process and strategies for optimizing their structures are summarized. Subsequently, a comprehensive review is presented regarding the applications of carbon-based materials and conductive polymer materials in various fields of flexible energy storage, such as supercapacitors, lithium-ion batteries, and zinc-ion batteries. Finally, the challenges and future directions for next-generation flexible energy storage systems are proposed.

High Performance Aqueous Zinc-Ion Batteries Developed by PANI Intercalation Strategy and Separator Engineering

Aqueous zinc-ion batteries (ZIBs) have attracted burgeoning attention and emerged as prospective alternatives for scalable energy storage applications due to their unique merits such as high volumetric capacity, low cost, environmentally friendly, and reliable safety. Nevertheless, current ZIBs still suffer from some thorny issues, including low intrinsic electron conductivity, poor reversibility, zinc anode dendrites, and side reactions. Herein, conductive polyaniline (PANI) is intercalated as a pillar into the hydrated V2O5 (PAVO) to stabilize the structure of the cathode material. Meanwhile, graphene oxide (GO) was modified onto the glass fiber (GF) membrane through simple electrospinning and laser reduction methods to inhibit dendrite growth. As a result, the prepared cells present excellent electrochemical performance with enhanced specific capacity (362 mAh g-1 at 0.1 A g-1), significant rate capability (280 mAh g-1 at 10 A g-1), and admirable cycling stability (74% capacity retention after 4800 cycles at 5 A g-1). These findings provide key insights into the development of high-performance zinc-ion batteries.

Air-Processed All-Inorganic Halide Perovskites Integrated Photorechargeable Supercapacitors

Due to their easy integration for self-powered operation, integrated energy harvesting and storage could be the game changer in smart, flexible, and portable electronic devices. Three-electrode integration is the most promising approach among all possible configurations because it is less complex and compatible with most techniques. Although the photoconversion efficiency has increased above 20% due to the integration of high-performance perovskite solar cells, the electrochemical storage efficiency (efficacy of the integration) is much below 80% due to a significant potential drop and impedance mismatch. In this context, we introduced perovskite-based solid-state thin film supercapacitors integrated with stable, air-processed perovskite solar cells for an uninterrupted power supply. Our measurement shows that the best performance can be achieved by optimizing several parameters, including series-connected solar cells, light intensity, and photovoltaic active area. The critical challenge with these integrated systems is to maintain a uniform charging current of the supercapacitors throughout the charging cycle while minimizing self-discharging. We achieved an electrochemical storage efficiency of ∼87% at an overpotential of 0.8 V. The overpotential can be as low as 2 mV. We fabricated fully solution-processed series-connected solar cells to integrate with stacked supercapacitors to improve the operating voltage beyond 2.1 V. The photocharging and dark discharging of these integrated devices have been tested over 200 cycles, and a negligible drop in efficiency has been observed. Our detailed energy conversion and storage analysis in these systems unveils the mechanism and losses due to three-terminal integration.

Mesoporous copper-doped δ-MnO2 superstructures to enable high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are competitive alternatives for large-scale energy-storage devices owing to the abundance of zinc and low cost, high theoretical specific capacity, and high safety of these batteries. High-performance and stable cathode materials in AZIBs are the key to storing Zn2+. Manganese-based cathode materials have attracted considerable attention because of their abundance, low toxicity, low cost, and abundant valence states (Mn2+, Mn3+, Mn4+, and Mn7+). However, as a typical cathode material, birnessite-MnO2 (δ-MnO2) has low conductivity and structural instability. The crystal structure may undergo severe distortion, disorder, and structural damage, leading to severe cyclic instability. In addition, its energy-storage mechanism is still unclear, and most of the reported manganese oxide-based materials do not have excellent electrochemical performance. Herein, we propose a copper-doped Cu0.05K0.11Mn0.84O2·0.54H2O (Cu2-KMO) cathode, which exhibits a large interlayer spacing, a stable structure, and accelerated reaction kinetics. This cathode was prepared using a simple hydrothermal method. The AZIB assembled using Cu2-KMO showed high specific capacity (600 mA h g-1 at 0.1 A g-1 after 75 cycles). The dissolution-deposition energy storage mechanism of Cu-KMO in AZIBs with double electron transfer was revealed using ex situ tests. The good electrochemical performance of the Cu2-KMO cathode fabricated by the doping strategy in this study provides ideas for the subsequent preparation of manganese dioxide using other strategies.

The Latest Advances in Ink-Based Nanogenerators: From Materials to Applications

Nanogenerators possess the capability to harvest faint energy from the environment. Among them, thermoelectric (TE), triboelectric, piezoelectric (PE), and moisture-enabled nanogenerators represent promising approaches to micro-nano energy collection. These nanogenerators have seen considerable progress in material optimization and structural design. Printing technology has facilitated the large-scale manufacturing of nanogenerators. Although inks can be compatible with most traditional functional materials, this inevitably leads to a decrease in the electrical performance of the materials, necessitating control over the rheological properties of the inks. Furthermore, printing technology offers increased structural design flexibility. This review provides a comprehensive framework for ink-based nanogenerators, encompassing ink material optimization and device structural design, including improvements in ink performance, control of rheological properties, and efficient energy harvesting structures. Additionally, it highlights ink-based nanogenerators that incorporate textile technology and hybrid energy technologies, reviewing their latest advancements in energy collection and self-powered sensing. The discussion also addresses the main challenges faced and future directions for development.

3D Hierarchical Sunflower-Shaped MoS2/SnO2 Photocathodes for Photo-Rechargeable Zinc Ion Batteries

Photo-rechargeable zinc-ion batteries (PRZIBs) have attracted much attention in the field of energy storage due to their high safety and dexterity compared with currently integrated lithium-ion batteries and solar cells. However, challenges remain toward their practical applications, originating from the unsatisfactory structural design of photocathodes, which results in low photoelectric conversion efficiency (PCE). Herein, a flexible MoS2/SnO2-based photocathode is developed via constructing a sunflower-shaped light-trapping nanostructure with 3D hierarchical and self-supporting properties, enabled by the hierarchical embellishment of MoS2 nanosheets and SnO2 quantum dots on carbon cloth (MoS2/SnO2 QDs@CC). This structural design provides a favorable pathway for the effective separation of photogenerated electron-hole pairs and the efficient storage of Zn2+ on photocathodes. Consequently, the PRZIB assembled with MoS2/SnO2 QDs@CC delivers a desirable capacity of 366 mAh g-1 under a light intensity of 100 mW cm-2, and achieves an ultra-high PCE of 2.7% at a current density of 0.125 mA cm-2. In practice, an integrated battery system consisting of four series-connected quasi-solid-state PRZIBs is successfully applied as a wearable wristband of smartwatches, which opens a new door for the application of PRZIBs in next-generation flexible energy storage devices.

Rational Design of High-Loading Electrodes with Superior Performances Toward Practical Application for Energy Storage Devices

High-loading electrodes play a crucial role in designing practical high-energy batteries as they reduce the proportion of non-active materials, such as current separators, collectors, and battery packaging components. This design approach not only enhances battery performance but also facilitates faster processing and assembly, ultimately leading to reduced production costs. Despite the existing strategies to improve rechargeable battery performance, which mainly focus on novel electrode materials and high-performance electrolyte, most reported high electrochemical performances are achieved with low loading of active materials (<2 mg cm-2). Such low loading, however, fails to meet application requirements. Moreover, when attempting to scale up the loading of active materials, significant challenges are identified, including sluggish ion diffusion and electron conduction kinetics, volume expansion, high reaction barriers, and limitations associated with conventional electrode preparation processes. Unfortunately, these issues are often overlooked. In this review, the mechanisms responsible for the decay in the electrochemical performance of high-loading electrodes are thoroughly discussed. Additionally, efficient solutions, such as doping and structural design, are summarized to address these challenges. Drawing from the current achievements, this review proposes future directions for development and identifies technological challenges that must be tackled to facilitate the commercialization of high-energy-density rechargeable batteries.

A Hydrogel Electrolyte toward a Flexible Zinc-Ion Battery and Multifunctional Health Monitoring Electronics

The compact design of an environmentally adaptive battery and effectors forms the foundation for wearable electronics capable of time-resolved, long-term signal monitoring. Herein, we present a one-body strategy that utilizes a hydrogel as the ionic conductive medium for both flexible aqueous zinc-ion batteries and wearable strain sensors. The poly(vinyl alcohol) hydrogel network incorporates nano-SiO2 and cellulose nanofibers (referred to as PSC) in an ethylene glycol/water mixed solvent, balancing the mechanical properties (tensile strength of 6 MPa) and ionic diffusivity at -20 °C (2 orders of magnitude higher than 2 M ZnCl2 electrolyte). Meanwhile, cathode lattice breathing during the solvated Zn2+ intercalation and dendritic Zn protrusion at the anode interface are mitigated. Besides the robust cyclability of the Zn∥PSC∥V2O5 prototype within a wide temperature range (from -20 to 80 °C), this microdevice seamlessly integrates a zinc-ion battery with a strain sensor, enabling precise monitoring of the muscle response during dynamic body movement. By employing transmission-mode operando XRD, the self-powered sensor accurately documents the real-time phasic evolution of the layered cathode and synchronized strain change induced by Zn deposition, which presents a feasible solution of health monitoring by the miniaturized electronics.

Three-dimensional Ordered Macroporous Flexible Electrode Design toward High-Performance Zinc-Ion Batteries

Flexible zinc-ion batteries (ZIBs) have been considered to have huge potential in portable and wearable electronics due to their high safety, cost efficiency, and considerable energy density. Therein, the design and construction of flexible electrodes significantly determine the performance and lifespan of flexible battery devices. In this work, an ultrathin flexible three-dimensional ordered macroporous (3DOM) Sn@Zn anode (60 μm in thickness) is presented to relieve dendrite growth and expand the lifespan of flexible ZIBs. The 3DOM structure can ensure uniform electric field distribution, guide oriented zinc plating/stripping, and extend the lifespan of anodes. The rich zincophilic Sn sites on the electrode surface significantly facilitate Zn nucleation. Accordingly, a lowered nucleation overpotential of 8.9 mV and an ultralong cycling performance of 2400 h at 0.1 mA cm-2 and 0.1 mAh cm-2 are achieved in symmetric cells, and the 3DOM Sn@Zn anode can also operate in deep cycling for over 200 h at 10 mA cm-2 and 5 mAh cm-2. A flexible 3DOM MnO2/Ni cathode with a high structural stability and a high mass-specific capacity is fabricated to match with the anode to form a flexible ZIB with a total thickness of 200 μm. The flexible device delivers a high volumetric energy density of 11.76 mWh cm-3 at 100 mA gMnO2-1 and a high average open-circuit voltage of 1.5 V and exhibits high-performance power supply under deformation in practical application scenarios. This work may shed some light on the design and fabrication of flexible energy-storage devices.

Highly Efficient and Stable ITO-Free Organic Solar Cells Based on Squaraine N-Doped Quaternary Bulk Heterojunction

Simultaneously achieving high efficiency and robust device stability remains a significant challenge for organic solar cells (OSCs). Solving this challenge is highly dependent on the film morphology of the bulk heterojunction (BHJ) photoactive blends; however, there is a lack of rational control strategy. Herein, it is shown that the molecular crystallinity and nanomorphology of nonfullerene-based BHJ can be effectively controlled by a squaraine-based doping strategy, leading to an increase in device efficiency from 17.26% to 18.5% when doping 2 wt% squaraine into the PBDB-TF:BTP-eC9:PC71 BM ternary BHJ. The efficiency is further improved to 19.11% (certified 19.06%) using an indium-tin-oxide-free column-patterned microcavity (CPM) architecture. Combined with interfacial modification, CPM quaternary OSC excitingly shows an extrapolated lifetime of ≈23 years based on accelerated aging test, with the mechanism behind enhanced stability well studied. Furthermore, a flexible OSC module with a high and stable efficiency of 15.2% and an overall area of 5 cm2 is successfully fabricated, exhibiting a high average output power for wearable electronics. This work demonstrates that OSCs with new design of BHJ and device architecture are highly promising to be practical relevance with excellent performance and stability.

Perovskite-Solar-Cell-Powered Integrated Fuel Conversion and Energy-Storage Devices

Metal halide hybrid perovskite solar cells (PSCs) have received considerable attention over the past decade owing to their potential for low-cost, solution-processable, earth-abundant, and high-performance superiority, increasing power conversion efficiencies of up to 25.7%. Solar energy conversion into electricity is highly efficient and sustainable, but direct utilization, storage, and poor energy diversity are difficult to achieve, resulting in a potential waste of resources. Considering its convenience and feasibility, converting solar energy into chemical fuels is regarded as a promising pathway for boosting energy diversity and expanding its utilization. In addition, the energy conversion-storage integrated system can efficiently sequentially capture, convert, and store energy in electrochemical energy storage devices. However, a comprehensive overview focusing on PSC-self-driven integrated devices with a discussion of their development and limitations remains lacking. Here, focus is on the development of representative configurations of emerging PSC-based photo-electrochemical devices including self-charging power packs, unassisted solar water splitting/CO2 reduction. The advanced progresses in this field, including configuration design, key parameters, working principles, integration strategies, electrode materials, and their performance evaluations are also summarized. Finally, scientific challenges and future perspectives for ongoing research in this field are presented.

Near-Neighbor Electron Orbital Coupling Effect of Single-Atomic-Layer Au Cluster Intercalated Bilayer 2H-TaS2 for Surface Enhanced Raman Scattering Sensing

It is difficult to perfectly analyze the enhancement mechanism of two-dimensional (2D) materials and their combination with precious metals as surface enhanced Raman scattering (SERS) substrates using chemical enhancement mechanisms. Here, we propose a new mentality based on the coupling effect of neighboring electron orbitals to elucidate the electromagnetic field enhancement mechanism of single-atom-layer Au clusters embedded in double-layer 2H-TaS2 for SRES sensing. The insertion of Au atoms into the 2H-TaS2 interlayer was verified by XRD, AFM, and HRTEM, and a SERS signal enhancement of 2 orders of magnitude was obtained compared to the pure 2H-TaS2. XPS and micro-UV/vis-NIR spectra indicate that the outer electrons of neighboring Au and 2H-TaS2 overlap and migrate from Au to 2H-TaS2. First-principles calculations suggest strong electronic coupling between Au and 2H-TaS2. This study offers insights into SERS enhancement in nonprecious metal compounds and guides the development of new SERS substrates.

Highly Reversible Zn Metal Anode with Low Voltage Hysteresis Enabled by Tannic Acid Chemistry

The zinc dendrites and side reactions formed on the zinc anode have greatly hindered the development of aqueous zinc-ion batteries (ZIBs). Herein, we introduce tannic acid (TA) as an additive in the ZnSO4 (ZSO) electrolyte to enhance the reversible Zn plating/stripping behavior. TA molecules are found to adsorb onto the zinc surface, forming a passivation layer and replacing some of the H2O molecules in the Zn2+ solvation sheath to form the [Zn(H2O)6-xTAx]2+ complex; this process effectively prevents side reactions. Moreover, the lower desolvation energy barrier of the [Zn(H2O)6-xTAx]2+ structure facilitates uniform Zn metal deposition and enables a stable plating/stripping lifespan of 2500 h with low voltage hysteresis (53 mV at 0.5 mA cm-2) as compared to the ZSO electrolyte (167 h and 104 mV). Additionally, the incorporation of the MnO2 cathode in the TA + ZSO electrolyte shows improved cycling capacity retention, from 64% (ZSO) to 85% (TA + ZSO), after 250 cycles at 1 A g-1, demonstrating the effectiveness of the TA additive in enhancing the performance of ZIBs.

Single-Ion-Conducting Hydrogel Electrolytes Based on Slide-Ring Pseudo-Polyrotaxane for Ultralong-Cycling Flexible Zinc-Ion Batteries

Flexible zinc-ion batteries (ZIBs) with high capacity and long cycle stability are essential for wearable electronic devices. Hydrogel electrolytes have been developed to provide ion-transfer channels while maintaining the integrity of ZIBs under mechanical strain. However, hydrogel matrices are typically swollen with aqueous salt solutions to increase ionic conductivity, which can hinder intimate contact with electrodes and reduce mechanical properties. To address this, a single-Zn-ion-conducting hydrogel electrolyte (SIHE) is developed by integrating polyacrylamide network and pseudo-polyrotaxane structure. The SIHE exhibits a high Zn2+ transference number of 0.923 and a high ionic conductivity of 22.4 mS cm-1 at room temperature. Symmetric batteries with SIHE demonstrate stable Zn plating/stripping performance for over 160 h, with a homogenous and smooth Zn deposition layer. Full cells with La-V2 O5 cathodes exhibit a high capacity of 439 mA h g-1 at 0.1 A g-1 and excellent capacity retention of 90.2% after 3500 cycles at 5 A g-1 . Moreover, the flexible ZIBs display stable electrochemical performance under harsh conditions, such as bending, cutting, puncturing, and soaking. This work provides a simple design strategy for single-ion-conducting hydrogel electrolytes, which could pave the way for long-life aqueous batteries.

Highly Robust {In2}-Organic Framework for Efficiently Catalyzing CO2 Cycloaddition and Knoevenagel Condensation

To improve the catalytic performance of metal-organic frameworks (MOFs), creating higher defects is now considered as the most effective strategy, which can not only optimize the Lewis acidity of metal ions but also create more pore space to enhance diffusion and mass transfer in the channels. Herein, the exquisite combination of scarcely reported [In₂(CO₂)₅(H₂O)₂(DMF)₂] clusters and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H₅BDCP) under solvothermal conditions generated a highly robust nanoporous framework of {[In₂(BDCP)(DMF)₂(H₂O)₂](NO₃)}_n (NUC-65) with nanocaged voids (14.1 Å) and rectangular nanochannels (15.94 Å × 11.77 Å) along the a axis. It is worth mentioning that an In(1) ion displays extremely low tetra-coordination modes after the thermal removal of its associated four solvent molecules of H₂O and DMF. Activated {[In₂(BDCP)](Br)}_n (NUC-65Br), as a defective material because of its extremely unsaturated metal centers, could be generated by bromine ion exchange, solvent exchange, and vacuum drying. Catalytic experiments proved that the conversion of epichlorohydrin with 1 atm CO₂ into 4-(chloromethyl)-1,3-dioxolan-2-one catalyzed by 0.11 mol % NUC-65Br could reach 99% at 65 °C within 24 h. Moreover, with the aid of 5 mol % cocatalyst n-Bu₄NBr, heterogeneous NUC-65Br owns excellent universal catalytic performance in most epoxides under mild conditions. In addition, NUC-65Br, as a heterogeneous catalyst, exhibits higher activity and better selectivity for Knoevenagel condensation of aldehydes and malononitrile. Hence, this work offers a fresh insight into the design of structure defect cationic metal-organic frameworks, which can be better applied to various fields because of their promoted performance.

2D Materials Boost Advanced Zn Anodes: Principles, Advances, and Challenges

Aqueous zinc-ion battery (ZIB) featuring with high safety, low cost, environmentally friendly, and high energy density is one of the most promising systems for large-scale energy storage application. Despite extensive research progress made in developing high-performance cathodes, the Zn anode issues, such as Zn dendrites, corrosion, and hydrogen evolution, have been observed to shorten ZIB's lifespan seriously, thus restricting their practical application. Engineering advanced Zn anodes based on two-dimensional (2D) materials are widely investigated to address these issues. With atomic thickness, 2D materials possess ultrahigh specific surface area, much exposed active sites, superior mechanical strength and flexibility, and unique electrical properties, which confirm to be a promising alternative anode material for ZIBs. This review aims to boost rational design strategies of 2D materials for practical application of ZIB by combining the fundamental principle and research progress. Firstly, the fundamental principles of 2D materials against the drawbacks of Zn anode are introduced. Then, the designed strategies of several typical 2D materials for stable Zn anodes are comprehensively summarized. Finally, perspectives on the future development of advanced Zn anodes by taking advantage of these unique properties of 2D materials are proposed.

Rationally designed Mn2O3@ZnMn2O4/C core-shell hollow microspheres for aqueous zinc-ion batteries

Manganese-based oxides are common cathode materials for aqueous zinc ion batteries (AZIBs) because of their great capacity and high working voltage. However, the sharp decline of capacity caused by the dissolution of manganese-based cathode materials and the low-rate performance restrict their development. To address these problems, unique core-shell structured Mn₂O₃@ZnMn₂O₄/C hollow microspheres are reported as an ideal cathode material for AZIBs. Benefiting from the hollow structure, the zeolitic imidazolate framework (ZIF)-derived carbon and ZnMn₂O₄. Its application in AZIBs as the cathode demonstrates its satisfactory rate performance, high cycle stability, and excellent reversibility. Its high reversible capacity is remarkable, which reaches its maximum of 289.9 mA h g^-1 at 200 mA g^-1 and maintains a capacity of 203.5 mA h g^-1 after cycling for 700 times at 1000 mA g^-1. These excellent performances indicate that this material is a potential cathode material of AZIBs.

Oxygen vacancies refilling and potassium ions intercalation of δ-manganese dioxide with high structural stability toward 2.3 V high voltage asymmetric supercapacitors

Oxygen vacancies occupation and coordination environment modulation of the transition-metal based electrodes are effective strategies to improve the structural stability and electrochemical performance. In this work, the 2-methylimidazole (2-MI) doped manganese dioxide (MnO2) anchored on carbon cloth (CC) is fabricated via a simple method (MI-MnO2-x/CC), where the oxygen defects on/inside the K+ doped δ-MnO2 nanosheets are in-situ created by reductive ethanol/Mn2+ and occupied by 2-MI ligands. With the pre-embedded K+ ions and abundant ligand-refilled defects, the electronic coordination structure, structural stability and electron/ion diffusion efficiency can be effectively enhanced. Therefore, the MI-MnO2-x/CC reveals a remarkable specific capacitance of 721.2 mF cm-2 with excellent cycle durability (capacitance retention of 93.4% after 10,000 cycles) under 1.3 V operation potential window. In addition, an asymmetric supercapacitor assembled by MI-MnO2-x/CC and activated mechanical exfoliated graphene oxide yields a maximum energy density of 57.0 Wh kg-1 and a highest power density of 23.0 kW kg-1 under 2.3 V. This effective oxygen defect stabilization strategy by ligands refilling can be extended to various metal oxide-based electrodes for energy storage and conversion.

Unlocking the Potential of Vanadium Oxide for Ultrafast and Stable Zn2+ Storage Through Optimized Stress Distribution: From Engineering Simulation to Elaborate Structure Design

Compared with lithium-ion batteries (LIBs), aqueous zinc batteries (AZIBs) have received extensive attention due to their safety and cost advantages in recent years. The cathode determines the electrochemical performance of AZIBs to a large extent. Vanadium-based materials exhibit excellent capacity when used as AZIB cathodes. However, unexpected structural stress is inevitably induced during cycling and high current densities, which can gradually lead to structural deterioration and capacity decay. In fact, the stress/strain distribution in nanomaterials is crucial for electrochemical performance. In this work, the optimized stress distribution of the hierarchical hollow structure is verified by the finite element simulation of COMSOL software firstly. Guided by this model, a simple solvothermal method to synthesize hierarchical hollow vanadium oxide nanospheres (VO-NSs), consisting of ≈10 nm ultrathin nanosheets and ≈500 nm hollow inner cavities, is employed. And a highly disordered structure is introduced to the VO-NSs by in situ electrochemical oxidation, which can also weaken the structural stress during Zn²⁺ insertion and extraction. Benefiting from this unique structure, VO-NSs exhibit high-rate and stable Zn²⁺ storage capability. The strategy of engineering-driven material design provides new insights into the development of AZIB cathodes.

Manipulating Oxygen Vacancies by K+ Doping and Controlling Mn2+ Deposition to Boost Energy Storage in β-MnO2

Aqueous zinc-ion batteries (ZIBs) have gained wide attention for their low cost, high safety, and environmental friendliness in recent years. β-MnO₂, a potential cathode material for ZIBs, has been restricted by its small channels for efficient charge storage. Herein, β-MnO₂ nanorods with oxygen vacancies are fabricated by a K⁺-doping strategy to improve the performance of ZIBs. The assembled batteries exhibit a capacity of 468 mAh g^-1, a power density of 2605 W kg^-1, and an energy density of 179 Wh kg^-1, which outperforms most reported ZIBs. Such a performance is owing to the synergistic combination of the oxygen vacancies in β-MnO₂ and concurrent deposition of ε-MnO₂ from Mn²⁺ in the electrolyte. Furthermore, superior cycling stability with negligible capacity decay in these batteries is demonstrated over 1000 cycles at a high current of 2 A g^-1. This study reveals the importance of oxygen vacancies and Mn²⁺ deposition effect in understanding the mechanism of charge storage in MnO₂-based ZIBs.

Fluorine-Functionalized NbO-Type {Cu2}-Organic Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation

The high catalytic activity of metal-organic frameworks (MOFs) can be realized by increasing their effective active sites, which prompts us to perform the functionalization on selected linkers by introducing a strong Lewis basic group of fluorine. Herein, the exquisite combination of paddle-wheel [Cu₂(CO₂)₄(H₂O)] clusters and meticulously designed fluorine-funtionalized tetratopic 2',3'-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid (F-H₄ptta) engenders one peculiar nanocaged {Cu₂}-organic framework of {[Cu₂(F-ptta)(H₂O)₂]·5DMF·2H₂O}_n (NUC-54), which features two types of nanocaged voids (9.8 Å × 17.2 Å and 10.1 Å × 12.4 Å) shaped by 12 paddle-wheel [Cu₂(COO)₄H₂O)₂] secondary building units, leaving a calculated solvent-accessible void volume of 60.6%. Because of the introduction of plentifully Lewis base sites of fluorine groups, activated NUC-54a exhibits excellent catalytic performance on the cycloaddition reaction of CO₂ with various epoxides under mild conditions. Moreover, to expand the catalytic scope, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile were performed using the heterogenous catalyst of NUC-54a. Also, NUC-54a features high recyclability and catalytic stability with excellent catalytic performance in subsequent catalytic tests. Therefore, this work not only puts forward a new solution for developing high-efficiency heterogeneous catalysts, but also enriches the functionalization strategies for nanoporous MOFs.

Boosting Li-Ion Diffusion Kinetics of Na2Ti6-xMoxO13 via Coherent Dimensional Engineering and Lattice Tailoring: An Alternative High-Rate Anode

Featured with an exposed active facet, favorable ion diffusion pathway, and tailorable interfacial properties, low-dimensional structures are extensively explored as alternative electroactive materials with game-changing redox properties. Through a stepwise "proton exchange-insertion-exfoliation" procedure, in this article, we develop Na₂Ti_6-xMo_xO₁₃ (NTMO) nanosheets with weakened out-of-plane bonding and in-plane Mo⁶⁺ doping of the tunnel structure. Real-time phase tracking of the laminated NTMO structures upon the lithiation/delithiation process suggests mitigated lattice variation; meanwhile, the kinetics simulation shows a mitigated Li-ion diffusion barrier along the [010] orientation. At an industrial-level areal capacity loading (2.5 mAh cm^-2), the NTMO electrode maintains robust cycling endurance (91% capacity retention for 2000 cycles) even at 40 C, as well as the high energy/power densities in the as-constructed NTMO||LiFePO₄ full cell prototype. The dimensional and lattice modifications presented in this study thus encourage further exploration of the tailored cation diffusion pathway for the construction of fast-charging batteries.

Ten-Gram-Scale Mechanochemical Synthesis of Ternary Lanthanum Coordination Polymers for Antibacterial and Antitumor Activities

As rare-earth coordination polymers (CPs) have appreciable antimicrobial properties, ternary lanthanum CPs have been widely synthesized and investigated in recent years. Here, we report convenient, solvent-free reactions between the lanthanum salt and two ligands at mild temperatures that form ternary lanthanum nanoscale CPs with 10-gram-scale. The structural features and morphologies were characterized using a scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), ultraviolet-visible (UV–Vis), X-ray diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), Brunauer–Emmett–Teller (BET), elemental analysis, inductively coupled plasma mass spectrometry (ICP-MS), electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR), dynamic light scattering (DLS) and analyzer, and thermogravimetric and differential thermal analyzer (TG-DTA). Furthermore, the in vitro antibacterial activities of these ternary hybrids were studied using the zone of inhibition (ZOI) method, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and transmission electron microscope (TEM) and were found to have excellent antibacterial properties. The in vitro antitumor activities were performed in determining the absorbance values by CCK-8 (Cell Counting Kit-8) assay. This facile synthetic method would potentially enable the mass production of ternary lanthanum CPs at room temperature, which can be promising candidates as antibacterial compounds and antitumor agents.

Intercalation-Activated Layered MoO3 Nanobelts as Biodegradable Nanozymes for Tumor-Specific Photo-Enhanced Catalytic Therapy

The existence of natural van der Waals gaps in layered materials allows them to be easily intercalated with varying guest species, offering an appealing strategy to optimize their physicochemical properties and application performance. Herein, we report the activation of layered MoO₃ nanobelts via aqueous intercalation as an efficient biodegradable nanozyme for tumor-specific photo-enhanced catalytic therapy. The long MoO₃ nanobelts are grinded and then intercalated with Na⁺ and H₂ O to obtain the short Na⁺ /H₂ O co-intercalated MoO_3-x (NH-MoO_3-x ) nanobelts. In contrast to the inert MoO₃ nanobelts, the NH-MoO_3-x nanobelts exhibit excellent enzyme-mimicking catalytic activity for generation of reactive oxygen species, which can be further enhanced by the photothermal effect under a 1064 nm laser irradiation. Thus, after bovine serum albumin modification, the NH-MoO_3-x nanobelts can efficiently kill cancer cells in vitro and eliminate tumors in vivo facilitating with 1064 nm laser irradiation.

Boosting Zn2+ Diffusion via Tunnel-Type Hydrogen Vanadium Bronze for High-Performance Zinc Ion Batteries

Aqueous zinc ion batteries (ZIBs) are emerging as a promising candidate in the post-lithium ion battery era, while the limited choice of cathode materials plagues their further development, especially the tunnel-type cathode materials with high electrochemical performance. Here, a tunnel-type vanadium-based compound based on hydrogen vanadium bronze (H_xV₂O₅) microspheres has been fabricated and employed as the cathode for fast Zn²⁺ ions' intercalation/deintercalation, which delivers an excellent capacity (425 mAh g^-1 at 0.1 A g^-1), a remarkable cyclability (91.3% after 5000 cycles at 20 A g^-1), and a sufficient energy density (311.5 Wh kg^-1). As revealed by the experimental and theoretical results, such excellent electrochemical performance is confirmed to result from the fast ions/electrons diffusion kinetics promoted by the unique tunnel structure (3.7 × 4.22 Ų, along the c direction), which accomplishes a low Zn²⁺ ion diffusion barrier and the superior electron-transfer capability of H_xV₂O₅. These results shed light on designing tunnel-type vanadium-based compounds to boost the prosperous development of Zn²⁺ ion storage cathodes.

Sodium tungsten bronze-supported Pt electrocatalysts for the high-performance hydrogen evolution reaction

NaxWO3 nanotube bundle was fabricated as a support for hosting Pt nanoparticle. Benefitting from the metal–support interaction, the optimal catalyst shows excellent activity with 46 mV overpotential at −100 mA cm−2, superior to the commercial Pt/C.

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

The electronic structure regulation of the electrode materials can improve the ion/electron kinetics, which are beneficial to the cyclic performance and rate capability for lithium ion batteries (LIBs). Herein, we...

Current advances and challenges in nanosheet-based wearable power supply devices

Nowadays, wearable devices mainly exist in the form of portable accessories with various functions, connecting various kinds of terminals like mobile phones to form various wearable systems. In a wearable system, the wearable power supply device is the key component as energy dispenser for all devices. Nanosheets, a kind of two-dimensional material, which always displays a high surface-to-volume ratio and thus is lightweight and has remarkable conductive as well as electrochemical properties, have become the optimal choice for wearable power supply devices. The development and status of nanosheet-based wearable power supply devices including nanosheet-based wearable batteries, nanosheet-based wearable supercapacitors, nanosheet-based wearable self-powered energy suppliers are introduced in this article. Besides, the future opportunities and challenges of wearable devices are discussed.

Multifunctional ionic liquid-assisted interfacial engineering towards ZnS nanodots with ultrastable high-rate lithium storage performance

In this article, a new zinc-containing ionic liquid (IL) [HMMIm]₂[ZnCl₄] (HMMIm = 1-hexyl-2,3-dimethyl-imidazolium) is designed, which acts as a multifunctional source for the interfacial engineering of ZnS nanodots (NDs). Given the electrostatic interaction driven by the imidazolium cation, the steric effect of the alkyl chain, and the in situ released Zn ion from the IL, [HMMIm]₂[ZnCl₄] shows great advantages in controlling the formation of ZnS NDs. Based on this strategy, a nanocomposite consisting of homodispersed ZnS NDs anchored on sulfur/nitrogen dual-doped reduced graphene oxide (ZnS-NDs@SNG) is prepared. When evaluated as an anode material for lithium-ion batteries (LIBs), the nanocomposite delivers high reversible specific capacity, excellent high-rate performance, and superior cycling life. In particular, a discharge capacity of 648.1 mA h g^-1 can be achieved at a high current density (10.0 A g^-1) over 5000 cycles. Benefitting from the multifunctional IL and the simple synthesis protocol, the IL-assisted interfacial engineering strategy will enable a new avenue for the controllable synthesis of metal-sulfide-based anode materials.

Graphene-Based Cathode Materials for Lithium-Ion Capacitors: A Review

Lithium-ion capacitors (LICs) are attracting increasing attention because of their potential to bridge the electrochemical performance gap between batteries and supercapacitors. However, the commercial application of current LICs is still impeded by their inferior energy density, which is mainly due to the low capacity of the cathode. Therefore, tremendous efforts have been made in developing novel cathode materials with high capacity and excellent rate capability. Graphene-based nanomaterials have been recognized as one of the most promising cathodes for LICs due to their unique properties, and exciting progress has been achieved. Herein, in this review, the recent advances of graphene-based cathode materials for LICs are systematically summarized. Especially, the synthesis method, structure characterization and electrochemical performance of various graphene-based cathodes are comprehensively discussed and compared. Furthermore, their merits and limitations are also emphasized. Finally, a summary and outlook are presented to highlight some challenges of graphene-based cathode materials in the future applications of LICs.

Green and Scalable Fabrication of Sandwich-like NG/SiOx/NG Homogenous Hybrids for Superior Lithium-Ion Batteries

SiOx is considered as a promising anode for next-generation Li-ions batteries (LIBs) due to its high theoretical capacity; however, mechanical damage originated from volumetric variation during cycles, low intrinsic conductivity, and the complicated or toxic fabrication approaches critically hampered its practical application. Herein, a green, inexpensive, and scalable strategy was employed to fabricate NG/SiOx/NG (N-doped reduced graphene oxide) homogenous hybrids via a freeze-drying combined thermal decomposition method. The stable sandwich structure provided open channels for ion diffusion and relieved the mechanical stress originated from volumetric variation. The homogenous hybrids guaranteed the uniform and agglomeration-free distribution of SiOx into conductive substrate, which efficiently improved the electric conductivity of the electrodes, favoring the fast electrochemical kinetics and further relieving the volumetric variation during lithiation/delithiation. N doping modulated the disproportionation reaction of SiOx into Si and created more defects for ion storage, resulting in a high specific capacity. Deservedly, the prepared electrode exhibited a high specific capacity of 545 mAh g-1 at 2 A g-1, a high areal capacity of 2.06 mAh cm-2 after 450 cycles at 1.5 mA cm-2 in half-cell and tolerable lithium storage performance in full-cell. The green, scalable synthesis strategy and prominent electrochemical performance made the NG/SiOx/NG electrode one of the most promising practicable anodes for LIBs.