An Ultrafast, Durable, and High-Loading Polymer Anode for Aqueous Zinc-Ion Batteries and Supercapacitors

High toughness, high stability and low hysteresis PVA /HPMC/PA/SBMA/ZnCl2 conductive hydrogels for wearable flexible electronics for multifunctional sensors and supercapacitors

PVA-based conductive hydrogels have enormous potential for applications in wearable flexible electronic devices, but their low ionic conductivity and mechanical strength hinder their practical utility. To address this challenge, we propose a PVA-based incorporating metal salt and zwitterion. We use PA(phytic acid) and HPMC (hydroxypropyl methylcellulose) - compatible properties to prepare PSBMA1-PMAZ1.5 interpenetrating conductive hydrogel with good electrical signal responsiveness, repeatability, compression resistance, and low hysteresis (≤11.68 %). The hydrogel-based flexible strain sensor has a wide detection range, high sensitivity (GF = 1.1 at 0 - 600 %), stable electrical signal response to variations in temperature and humidity, and human movement detection capabilities. The detection range of hydrogel - based supercapacitors is 25 °C - 40 °C, which indicates that the device assembled with activated carbon as the electrode has good capacitance characteristics, and the multifunctional characteristics of PSBMA1-PMAZ1.5 hydrogels are poised to serve as a demonstration for a new generation of flexible electronic products.

Pressurized organic electrodes enable practical and extreme batteries

While organic batteries hold promise for sustainable energy storage, a considerable gap persists between research and application concerning testing conditions and cell cost. Here, we report pressurized organic electrodes tailored for practical applications. Outperforming prior organic electrodes, pressurized organic electrodes excel under challenging/extreme condition including high mass loadings (50-150 mg cm-2), active material fraction (up to 95%), low N/P ratio (0.8-2), and lean electrolyte, delivering high areal/volumetric capacity in full cells. Moreover, pressurized organic electrodes exhibit broad applicability, thriving in diverse battery systems (Li+/NH4+/H+/Na+/Zn2+/Mg2+ ion batteries) and organic materials (molecule, polymer, salt), consistently demonstrating enhanced performance compared with unpressurized ones. The improved capacity, rate, and cycling performance of pressurized electrodes result from pressure-induced structural and property changes in organics including crystal orientation, enhanced π-π interaction, favorable electrode porosity/tortuosity, accelerated chemical reactivity, and boosted electronic conductivity. Along with simple, efficient, green, and cost-effective manufacturing features, pressurized organic electrodes offer a promising route towards organic battery application.

Synergy of Strongly Coordinating Salts and Weakly Coordinating Solvents Enables Stable and Fast-Kinetics Zinc Metal Batteries

The development of Zn metal batteries is hindered by Zn dendrites, notorious side reactions, and performance decay in harsh temperatures. Despite the efficacy of strongly coordinating organic solvents in addressing these issues, challenges persist regarding low ionic conductivity, high viscosity, and high desolvation barrier, particularly at low temperatures. Additionally, the strongly coordinating solvents around Zn2+ diminish anions participating in the first solvation shell, leading to the formation of an organic-rich interphase. To achieve balanced physicochemical properties, an electrolyte system combining chaotropic Zn(ClO4)2 salts with weakly coordinating solvents (MeOH) and highly coordinating salts (Zn(OAc)2) is proposed. Experimental and simulation results reveal that this system creates an anion-rich solvation shell with low desolvation barriers, inhibiting water decomposition and promoting the formation of an inorganic-organic-rich solid electrolyte interphase. OAc- also assists in the dense vertical zinc deposition along the (101) crystal plane. The reconstructed weak hydrogen bonds between MeOH and H2O break the highly ordered structure of water at low temperatures, enabling a higher ionic conductivity. Consequently, the battery employing the designed system yields superior electrochemical performance across a wide temperature range (-80 °C-40 °C). The proposed strategy facilitates the electrolyte design for wide-temperature Zn metal batteries with fast reaction kinetics.

High-Energy-Density Aqueous Zinc-Ion Batteries: Recent Progress, Design Strategies, Challenges, and Perspectives

Aqueous zinc-ion batteries (AZIBs) are emerging as a promising energy storage technique supplementary to Li-ion batteries, attracting much research attention owing to their intrinsic safety, cost economy, and environmental friendliness. However, energy densities for AZIBs still do not fulfill practical requirements because of the low specific and areal capacity, limited working potential, and excessive negative-to-positive electrode capacity (N/P) ratio. In this review, a comprehensive overview of basic requirements and major challenges for achieving high-energy-density AZIBs is provided. Following that, recent progress in the optimization of each component and the overall configuration is summarized, and crucial design principles are discussed. Apart from conventional emphasis on each part, especially cathode materials, separately, the comprehensive discussion about the synergistic interactions among all components is conducted. Finally, the outlook and research direction are given to provide valuable guidance for the further holistic development of high-energy-density aqueous zinc-ion batteries.

Noncovalent Interactions Promoted Kinetics in Perylene Diimide-Based Aqueous Zn-Ion Batteries: An Operando Attenuated Total Reflection Infrared Study

Perylene-based organic anodes, as an alternative to metallic Zn for aqueous Zn-ion batteries, store Zn2+ through a Zn enolate coordination mechanism, which potentially bypasses challenges such as dendrite and hydroxide formation associated with a Zn anode. However, organic anodes exhibit low electrical conductivity and show a low rate performance. Molecular aggregation of conjugated aromatics plays a key role in the electrical conductivity of this class of material, and it is important to understand their impact on the battery rate performance. In this work, we combined electrochemistry and in situ attenuated total reflection infrared characterization to demonstrate the dominating role of aggregates in perylene-based electrodes in the enhancement of the electrode kinetics. We demonstrated the use of noncovalent interaction to form a supermolecular network that exhibits more than 4 orders of magnitude increase in the electron transfer rate, and provides nearly doubled charge storage capacity. The aggregation of perylene units was driven by π-π stacking and hydrogen bonding between the active material and a mediator, ethylene diamine. We showed that, in practice, this additive-mediated aggregation can occur during solution process at a moderate temperature.

Advanced electrolyte strategies for dendrite-free aqueous Zn-metal batteries

Aqueous Zn-metal batteries have attracted wide attention due to the abundant Zn reserves and the safety and non-toxicity of aqueous electrolytes, and have become a research hotspot in the field of electrochemical energy. However, the dendrite defects of metal Zn anodes and the resulting interfacial instability limit the large-scale development. Despite comprehensive studies and in-depth understanding, this issue still affects the electrochemical performance of Zn-metal batteries dramatically. In light of the great progress and recent focus, this review analyzes the origin of critical Zn dendrite related problems, and recapitulates the development of electrolyte strategies. In the end, various outlooks are summarized from different angles to improve the performance of Zn metal anodes. This study is expected to provide new inspiration for innovation in aqueous Zn battery electrolytes in the future.

Structural codes of organic electrode materials for rechargeable multivalent metal batteries

Rechargeable multivalent metal batteries (MMBs) are considered as promising alternatives to Li-ion and Pb-acid batteries for grid-scale energy storage applications due to the multi-electron redox capability of metal anodes. However, the conventional inorganic cathodes used in MMBs face challenges with the sluggish diffusivity and poor storage of charge-dense multivalent cations in their crystal lattice. Organic electrode materials (OEMs), on the other hand, offer several advantages as MMB cathodes, including flexible structural designability, high resource availability, sustainability, and a unique ion-coordination storage mechanism. This review explores the intrinsic connection between the structural features of OEMs and their charge storage performance, aiming to unveil key design principles for organic molecules used in various MMB applications. We begin with an overview of the fundamental aspects of different MMBs (i.e., Zn/Mg/Ca/Al batteries), covering electrolyte selection, metal stripping/plating electrochemistry, and the fundamentals of cathode operation. From a theoretical understanding of redox activities, we summarize the properties of different redox sites and correlate the electrochemical properties of OEMs with various structural factors. This analysis further leads to the introduction of critical design considerations for different types of OEMs. We then critically review a wide range of organic compounds for MMBs, from small organic molecules to redox-active polymers and covalent-organic frameworks, focusing on their structure-property relationships, key electrochemical parameters, and strengths and shortcomings for multivalent ion storage. Finally, we discuss the existing challenges and propose potential solutions for further advancing OEMs in MMBs.

Activating Organic Electrode for Zinc Batteries via Adjusting Solvation Structure of Zn Ions

Zinc-organic batteries, combining the low cost and high capacity of Zn anodes with the tunable and sustainable properties of organic cathodes, have garnered significant attention. Herein, we present a zinc-organic battery featuring a poly(benzoquinonyl sulfide) (PBQS) cathode, a Zn anode, and an N,N-dimethylformamide (DMF)-based electrolyte, which delivers a high capacity (200 mAh g-1), excellent rate capability, and an ultra-long cycle life (10,000 cycles) when tested with a low PBQS loading (2 mg cm-2). The charge storage mechanism in the PBQS cathode involves solvated Zn2+ adsorption and consequent Zn2+ coordination with PBQS companied by de-solvation process, as confirmed by in situ FT-IR analysis. However, sluggish Zn2+ de-solvation leads to a loss of Zn2+ coordination capacity when tested with higher PBQS loading (8 mg cm-2) even at a low current density of 0.2 A g-1. Remarkably, the addition of 2 % H2O to the DMF electrolyte incorporates 0.24 H2O into the primary solvation sheath of Zn2+, significantly facilitating the de-solvation process. As a result, the PBQS cathode (8 mg cm-2) retains its Zn2+ storage capacity when using the modified electrolyte. This approach offers a new strategy for improving the rate performance of organic electrodes, complementing existing conductivity enhancements.

Multiple Protophilic Redox-Active Sites in Reticular Organic Skeletons for Superior Proton Storage

Protons (H+) with the smallest size and fastest redox kinetics are regarded as competitive charge carriers in the booming Zn-organic batteries (ZOBs). Developing new H+-storage organic cathode materials with multiple ultralow-energy-barrier protophilic sites and super electron delocalization routes to propel superior ZOBs is crucial but still challenging. Here we design multiple protophilic redox-active reticular organic skeletons (ROSs) for activating better proton storage, triggered by intermolecular H-bonding and π-π stacking interactions between 2,6-diaminoanthraquinone and 2,4,6-triformylphloroglucinol nanofibrous polymer. ROSs expose reticular electron delocalization geometries to fully access build-in protophilic carbonyl sites and promote ultrarapid H+ migration with an ultralow activation energy (0.13 vs. 0.29 eV of Zn2+ ions), thus delivering high capacity (359 mAh g-1) and large-current survivability (100 A g-1). Moreover, the extended interconnected reticular structures strengthen the anti-dissolution of ROSs in aqueous electrolytes, affording long-lasting proton-storage activity in ZOBs to a superior level (60,000 cycles at 20 A g-1). Systematic studies identify the source of excellent charge storage as high-kinetics H+-coupled five-electron redox process of carbonyl motifs in superstable ROSs. These findings can be of importance for evoking superior proton activity in multiple redox organics to build advanced Zn-organic batteries.

A Universal Thick Anode for Aqueous and Seawater Energy Storage Devices

Aqueous and seawater energy storage devices hold great potential for electrical grids application due to safety, affordability, and sustainability. However, their broader deployment has been constrained by the absence of a durable thick anode. Here, the first universal thick anode operating stably across 15 simple-ion and 3 complex-ion systems, including nonmetallic (H+, NH4 +), monovalent (Li+, Na+, K+), multivalent ions (Zn2+, Ca2+, Mg2+, Al3+), and seawater ions (>5 cations) is reported. Composed of polymer nanosheets and carbon nanotubes, this anode supports thick electrode fabrication (e.g., 100 mg cm-2 and 1 mm) with low porosity/tortuosity, superior electrical conductivity, mechanical robustness, and chemical stability. Consequently, it achieves exceptionable cycle life (up to 380 000 cycles) in supercapacitors and ultrahigh areal capacities (6.5 mAh cm-2) in batteries, even under practical/extreme conditions, attributed to the formation of a water-scarce, cation-rich electrical double-layer structure, as revealed by simulations. Compatible with sea salt-based electrolytes and paired with a metal-free cathode, the anode enables seawater batteries with thousands-cycle life and high energy/power density. Of universal ion storage, ultrahigh-loading capability, unlimited resources, and cost-effectiveness, this polymer electrode is promising for practical aqueous (seawater) energy devices.

Multi-N-Heterocycle Donor-Acceptor Conjugated Amphoteric Organic Superstructures for Superior Zinc Batteries

Multiple redox-active amphoteric organics with more n-p fused electron transfer is an ongoing pursuit for superior zinc-organic batteries (ZOBs). Here we report multi-heterocycle-site donor-acceptor conjugated amphoteric organic superstructures (AOSs) by integrating three-electron-accepting n-type triazine motifs and dual-electron-donating p-type piperazine units via H-bonding and π-π stacking. AOSs expose flower-shaped N-heteromacrocyclic electron delocalization topologies to promise full accessibility of built-in n-p redox-active motifs with an ultralow activation energy, thus liberating superior capacity (465 mAh g-1) for Zn||AOSs battery. More importantly, the extended multiple donor-acceptor-fused conjugated AOSs feature satisfied discharge voltage and anti-dissolution in electrolytes, pushing both the energy density and cycle life of the ZOBs to a new level (412 Wh kg-1 and 70,000 cycles@10 A g-1). An anion-cation hybrid 18 e- charge storage mechanism is rationalized for heteromacrocyclic modules of AOSs cathode, entailing six tert-N motifs coupling with CF3SO3 - ions at high potential and twelve imine sites coordinating with Zn2+ ions at low potential. These findings constitute a major advance of amphoteric multielectron organic materials and stand for a good starting point for advanced ZOBs.

Extended π-conjugated N-heteroaromatic molecules for fast-charging and high operating voltage aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) with redox-active organic compounds as electrodes attract wide attention due to their structural diversity, sustainability and inherent safety. However, the rational structural design of advanced organic electrodes with high practical capacity, long cycle life and high rate performance is still a great challenge. Herein, a strategy to improve the electrochemical performance of electrodes in AZIBs by constructing an extended π-conjugated hexaazatrinaphthalene (HATN)-based structure with electron-withdrawing cyano groups, 5, 6, 11, 12, 17, 18-hexaazatrinaphthalene-2, 3, 8, 9, 14, 15-hexacarbonitrile (HATN-6CN), is reported. The reduced lowest unoccupied molecular orbital (LUMO) energy level improves the discharge voltage to 0.71 V. Furthermore, HATN-6CN features abundant redox-active sites, solvent resistance and a smaller energy gap, enabling stable and rapid co-storage of H+ and Zn2+. As expected, HATN-6CN electrode achieves a high reversible capacity of 277mAhg-1 at 0.1Ag-1, an excellent rate capability of 94mAhg-1 at 10Ag-1, and a good capacity retention of 65 % after 10,000 cycles at 10 A/g, simultaneously. The ex-situ characterization and theoretical simulation results demonstrate that Zn2+ and H+ cations coordinate synergistically with CN groups and simultaneously reversibly form zinc hydroxide sulfate hydrate. This work affords an appropriate structural design of advanced organic electrodes for AZIBs.

Insight into Anionic Discrepancies in Bipolar Poly(Thionine) Organic Cathodes for Aqueous Zinc Ion Batteries

Electroactive organic electrode materials exhibit remarkable potential in aqueous zinc ion batteries (AZIBs) due to their abundant availability, customizable structures, sustainability, and high reversibility. However, the research on AZIBs has predominantly concentrated on unraveling the storage mechanism of zinc cations, often neglecting the significance of anions in this regard. Herein, bipolar poly(thionine) is synthesized by a simple and efficient polymerization reaction, and the kinetics of different anions are investigated using poly(thionine) as the cathode of AZIBs. Notably, poly(thionine) is a bipolar organic polymer electrode material and exhibits enhanced stability in aqueous solutions compared to thionine monomers. Kinetic analysis reveals that ClO4 - exhibits the fastest kinetics among SO4 2-, Cl-, and OTF-, demonstrating excellent rate performance (109 mAh g-1 @ 0.5 A g-1 and 92 mAh g-1 @ 20 A g-1). Mechanism studies reveal that the poly(thionine) cathode facilitates the co-storage of both anions and cations in Zn(ClO4)2. Furthermore, the lower electrostatic potential of ClO4 - influences the strength of hydrogen bonding with water molecules, thereby enhancing the overall kinetics in aqueous electrolytes. This work provides an effective strategy for synthesizing high-quality organic materials and offers new insights into the kinetic behavior of anions in AZIBs.

A facile self-saturation process enabling the stable cycling of a small molecule menaquinone cathode in aqueous zinc batteries

Small quinone molecules are promising cathode materials for aqueous zinc batteries. However, they experience fast capacity decay due to dissolution in electrolytes. Herein, we introduce a simple methyl group to a naphthoquinone (NQ) cathode and demonstrate a facile self-saturation strategy. The methyl group exhibits hydrophobic properties together with light weight and a weak electron-donation effect, which allows a good balance among cycling stability, capacity and voltage for cathode materials. The resulting menadione (Me-NQ) presents around one-third solubility of NQ. The former thus rapidly reaches saturation in the electrolyte during cycling, which suppresses subsequent dissolution. Thanks to this process, the Me-NQ cathode preserves 146 mA h g-1 capacity after 3500 cycles at 5 A g-1, far exceeding 88 mA h g-1 for NQ. Me-NQ also delivers a stabilized capacity of 316 mA h g-1 at 0.1 A g-1 with only 0.05 V lower average redox voltage than NQ. The co-storage of Zn2+ and H+ with the redox reactions on the carbonyl sites of Me-NQ is revealed.

Ostwald-Ripening Induced Interfacial Protection Layer Boosts 1,000,000-Cycled Hydronium-Ion Battery

Collapsing and degradation of active materials caused by the electrode/electrolyte interface instability in aqueous batteries are one of the main obstacles that mitigate the capacity. Herein by reversing the notorious side reactions include the loss and dissolution of electrode materials, as we applied Ostwald ripening (OR) in the electrochemical cycling of a copper hexacyanoferrate electrode in a hydronium-ion batteries, the dissolved Cu and Fe ions undergo a crystallization process that creates a stable interface layer of cross-linked cubes on the electrode surface. The layer exposed the low-index crystal planes (100) and (110) through OR-induced electrode particle growth, supplemented by vacancy-ordered (100) superlattices that facilitated ion migration. Our design stabilized the electrode-electrolyte interface considerably, achieving a cycle life of one million cycles with capacity retention of 91.6 %, and a capacity retention of 91.7 % after 3000 cycles for a full battery.

Boosting Spatial Charge Storage in Ion-Compatible Pores of Carbon Superstructures for Advanced Zinc-Ion Capacitors

Capacitive carbon cathodes deliver great potential for zinc-ion hybrid capacitors (ZHCs) due to their resource abundance and structural versatility. However, the dimension mismatch between the micropores of carbons and hydrated Zn2+ ions often results in unsatisfactory charge storage capability. Here well-arranged heterodiatomic carbon superstructures are reported with compatible pore dimensions for activating Zn2+ ions, initiated by the supramolecular self-assembly of 1,3,5-triazine-2,4,6-triamine and cyanuric acid via in-plane hydrogen-bonds and out-of-plane π-π interactions. Flower-shaped carbon superstructures expose more surface-active motifs, continuous charge-transport routes, and more importantly, well-developed pores. The primary subnanopores of 0.82 nm are size-exclusively accessible for solvated Zn2+ ions (0.86 nm) to maximize spatial charge storage, while rich mesopores (1-3 nm) allow for high-kinetics ion migration with a low activation energy. Such favorable superstructure cathodes contribute to all-round performance improvement for ZHCs, including high energy density (158 Wh kg-1), fast-charging ability (50 A g-1), and excellent cyclic lifespan (100 000 cycles). An anion-cation hybrid charge storage mechanism is elucidated for superstructure cathode, which entails alternate physical uptake of Zn2+/CF3SO3 - at electroactive pores and bipedal chemical binding of Zn2+ to electronegative carbonyl/pyridine motifs. This work expands the design landscape of carbon superstructures for advanced energy storage.

Order-in-disordered ultrathin carbon nanostructure with nitrogen-rich defects bridged by pseudographitic domains for high-performance ion capture

Carbon materials with defect-rich structure are highly demanded for various electrochemical scenes, but encountering a conflict with the deteriorative intrinsic conductivity. Herein, we build a highway-mediated nanoarchitecture that consists of the ordered pseudographitic nanodomains among disordered highly nitrogen-doped segments through a supramolecular self-assembly strategy. The "order-in-disorder" nanosheet-like carbon obtained at 800 °C (O/D NSLC-800) achieves a tradeoff with high defect degree (21.9 at% of doped nitrogen) and compensated electrical conductivity simultaneously. As expected, symmetrical O/D NSLC-800 electrodes exhibit superior capacitive deionization (CDI) performance, including brackish water desalination (≈82 mgNaCl g-1 at a cell voltage of 1.6 V in a 1000 mg L-1 NaCl solution) and reusage of actual refining circulating cooling water, outperforming most of the reported state-of-the-art CDI electrodes. The implanted pseudographitic nanodomains lower the resistance and activation energy of charge transfer, which motivates the synergy of hosting sites of multiple nitrogen configurations. Our findings shed light on electrically conductive nanoarchitecture design of defect-rich materials for advanced electrochemical applications based on molecular-level modulation.

Nanosized Chevrel phases for dendrite-free zinc-ion based energy storage: unraveling the phase transformations

The nanoscale form of the Chevrel phase, Mo6S8, is demonstrated to be a highly efficient zinc-free anode in aqueous zinc ion hybrid supercapacitors (ZIHSCs). The unique morphological characteristics of the material when its dimensions approach the nanoscale result in fast zinc intercalation kinetics that surpass the ion transport rate reported for some of the most promising materials, such as TiS2 and TiSe2. In situ Raman spectroscopy, post-mortem X-ray diffraction, Hard X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations were combined to understand the overall mechanism of the zinc ion (de)intercalation process. The previously unknown formation of the sulfur-deficient Zn2.9Mo15S19 (Zn1.6Mo6S7.6) phase is identified, leading to a re-evaluation of the mechanism of the (de)intercalation process. A full cell comprised of an activated carbon (YEC-8A) positive electrode delivers a cell capacity of 38 mA h g-1 and an energy density of 43.8 W h kg-1 at a specific current density of 0.2 A g-1. The excellent cycling stability of the device is demonstrated for up to 8000 cycles at 3 A g-1 with a coulombic efficiency close to 100%. Post-mortem microscopic studies reveal the absence of dendrite formation at the nanosized Mo6S8 anode, in stark contrast to the state-of-the-art zinc electrode.

Tackling the Challenges of Aqueous Zn-Ion Batteries via Polymer-Derived Strategies

Zn-ion batteries (ZIBs) have gathered unprecedented interest recently benefiting from their intrinsic safety, affordability, and environmental benignity. Nevertheless, their practical implementation is hampered by low rate performance, inferior Zn2+ diffusion kinetics, and undesired parasitic reactions. Innovative solutions are put forth to address these issues by optimizing the electrodes, separators, electrolytes, and interfaces. Remarkably, polymers with inherent properties of low-density, high processability, structural flexibility, and superior stability show great promising in tackling the challenges. Herein, the recent progress in the synthesis and customization of functional polymers in aqueous ZIBs is outlined. The recent implementations of polymers into each component are summarized, with a focus on the inherent mechanisms underlying their unique functions. The challenges of incorporating polymers into practical ZIBs are also discussed and possible solutions to circumvent them are proposed. It is hoped that such a deep analysis could accelerate the design of polymer-derived approaches to boost the performance of ZIBs and other aqueous battery systems as they share similarities in many aspects.

Non-Metal Ion Storage in Zinc-Organic Batteries

Zinc-organic batteries (ZOBs) are receiving widespread attention as up-and-coming energy-storage systems due to their sustainability, operational safety and low cost. Charge carrier is one of the critical factors affecting the redox kinetics and electrochemical performances of ZOBs. Compared with conventional large-sized and sluggish Zn2+ storage, non-metallic charge carriers with small hydrated size and light weight show accelerated interfacial dehydration and fast reaction kinetics, enabling superior electrochemical metrics for ZOBs. Thus, it is valuable and ongoing works to build better ZOBs with non-metallic ion storage. In this review, versatile non-metallic cationic (H+, NH4 +) and anionic (Cl-, OH-, CF3SO3 -, SO4 2-) charge carriers of ZOBs are first categorized with a brief comparison of their respective physicochemical properties and chemical interactions with redox-active organic materials. Furthermore, this work highlights the implementation effectiveness of non-metallic ions in ZOBs, giving insights into the impact of ion types on the metrics (capacity, rate capability, operation voltage, and cycle life) of organic cathodes. Finally, the challenges and perspectives of non-metal-ion-based ZOBs are outlined to guild the future development of next-generation energy communities.

Multielectron Redox-Bipolar Tetranitroporphyrin Macrocycle Cathode for High-Performance Zinc-Organic Batteries

Bipolar organics fuse the merits of n/p-type redox reactions for better Zn-organic batteries (ZOBs), but face the capacity plafond due to low density of active units and single-electron reactions. Here we report multielectron redox-bipolar tetranitroporphyrin (TNP) with quadruple two-electron-accepting n-type nitro motifs and dual-electron-donating p-type amine moieties towards high-capacity-voltage ZOBs. TNP cathode initiates high-kinetics, hybrid anion-cation 10e- charge storage involving four nitro sites coordinating with Zn2+ ions at low potential and two amine species coupling with SO4 2- ions at high potential. Consequently, Zn||TNP battery harvests high capacity (338 mAh g-1), boosted average voltage (1.08 V), and outstanding energy density (365 Wh kg-1 TNP). Moreover, the extended π-conjugated TNP macrocycle achieves anti-dissolution in electrolytes, prolonging the battery life to 50,000 cycles at 10 A g-1 with 71.6 % capacity retention. This work expands the chemical landscape of multielectron redox-bipolar organics for state-of-the-art ZOBs.

π-Conjugated molecule mediated self-doped hierarchical porous carbons via self-stacking interaction for high-energy and ultra-stable zinc-ion hybrid capacitors

Understanding the self-stacking interactions in precursors can facilitate the preparation of high-performance carbon materials and promote the commercial application of zinc ion hybrid capacitors (ZIHCs). Here, a π-conjugated molecule mediated pyrolysis strategy is presented to prepare carbon materials. Taking intermolecular force simulation (reduced density gradient plots) as a guide, the relationship between the self-stacking interactions in π-conjugated molecules and the structural parameters of carbon materials can be extrapolated. The resultant self-doped hierarchical porous carbons (NHPCs) derived from 1, 8, 4, 5-naphthalenetetracarboxdiimide with suitable self-stacking interactions empower the highest specific surface areas (2038 m2/g) and surface opening macropores. The NHPCs-based ZIHCs deliver a high capacity of 220 mAh/g, a high energy density of 149.5 Wh kg-1 and a super-stable cycle lifespan with 93.2 % capacity retention after 200, 000 cycles. The excellent electrochemical performance roots in the superior hierarchical porous structure with surface opening macropores, which guarantees the structural stability of carbon cathodes upon repeated rounds. Meanwhile, the heteroatom doping further relieves the kinetics concern of Zn2+ uptake/removal to enhance O-Zn-N binding particularly at high discharge currents. Besides, the proton-assisted Zn2+ dual-ion storage mechanism plays an essential role in the energy storage process. This work demonstrates a facile synthesis method and advances the fundamental understanding of its dual-ion storage mechanism.

The Compatibility of COFs Cathode and Optimized Electrolyte for Ultra-Long Lifetime Rechargeable Aqueous Zinc-Ion Battery

Rechargeable aqueous zinc-ion batteries (RAZIBs) are attractive due to their affordability, safety, and eco-friendliness. However, their potential is limited by the lack of high-capacity cathodes and compatible electrolytes needed for reliable performance. Herein, we have presented a compatibility strategy for the development of a durable and long-lasting RAZIBs. The covalent organic frameworks (COFs) based on anthraquinone (DAAQ-COF) is created and utilized as the cathode, with zinc metal serving as the anode. The electrolyte is made up of an aqueous solution containing zinc salts at various concentrations. The COF cathode has been designed to be endowed with a rich array of redox-active groups, enhancing its electrochemical properties. Meanwhile, the electrolyte is formulated using triflate anions, which have exhibited superiority over sulfate anions. This strategy lead to the development of an optimized COF cathode with fast charging capability, high Coulombic efficiency (nearly 100 %) and long-term cyclability (retention rate of nearly 100 % at 1 A g-1 after 10000 cycles). Moreover, through experimental analysis, a co-insertion mechanism involving Zn2+ and H+ in this cathode is discovered for the first time. These findings represent a promising path for the advancement of organic cathode materials in high-performance and sustainable RAZIBs.

Non-Metallic NH4 + /H+ Co-Storage in Organic Superstructures for Ultra-Fast and Long-Life Zinc-Organic Batteries

Compared with Zn2+ storage, non-metallic charge carrier with small hydrated size and light weight shows fast dehydration and diffusion kinetics for Zn-organic batteries. Here we first report NH4 + /H+ co-storage in self-assembled organic superstructures (OSs) by intermolecular interactions of p-benzoquinone (BQ) and 2, 6-diaminoanthraquinone (DQ) polymer through H-bonding and π-π stacking. BQ-DQ OSs exhibit exposed quadruple-active carbonyl motifs and super electron delocalization routes, which are redox-exclusively coupled with high-kinetics NH4 + /H+ but exclude sluggish and rigid Zn2+ ions. A unique 4e- NH4 + /H+ co-coordination mechanism is unravelled, giving BQ-DQ cathode high capacity (299 mAh g-1 at 1 A g-1 ), large-current tolerance (100 A g-1 ) and ultralong life (50,000 cycles). This strategy further boosts the capacity to 358 mAh g-1 by modulating redox-active building units, giving new insights into ultra-fast and stable NH4 + /H+ storage in organic materials for better Zn batteries.

Nonplanar π-Conjugated Sulfur Heterocyclic Quinone Polymer Cathode for Air-Rechargeable Zinc/Organic Battery with Simultaneously Boosted Output Voltage, Rate Capability, and Cycling Life

π-conjugated organic compounds with a good charge transfer ability and rich redox functional groups are promising cathode candidates for air-rechargeable aqueous Zn-based batteries (AAZBs). However, the output voltage of even the state-of-the-art π-conjugated organic cathodes lies well below 0.8 V, resulting in insufficient energy density. Herein, we design a nonplanar π-conjugated sulfur heterocyclic quinone polymer (SHQP) as an advanced cathode material for AAZBs by polymerization 1,4-Benzoquinone (BQ) and S heteroatoms periodically. The extended π-conjugated plane and enhanced aromaticity endow SHQP with a more sensitive charge transfer ability and robust structure. Furthermore, the delocalized π electrons in the whole system are insufficient as the π orbit of the S heteroatom is not in the same plane with the π orbit of BQ due to its folded configuration, resulting in negligible variation of electron density around C═O after the polymerization. Thus, the output voltage of SHQP shows no significant decrease even though the thioether bond (-S-) functions as electron donor. Consequently, the Zn/SHQP AAZBs can deliver a record high midpoint discharging voltage (0.95 V), rate performance (119 mAh g-1 at 10 A g-1), and durability (98.7% capacity retention after 200 cycles) across a wide temperature range.

Stable zinc anode interface and environmentally adaptable hydrogel electrolytes for stable operation of zinc-ion hybrid supercapacitors

Hydrogel-based zinc ion hybrid supercapacitors (ZIHS) have stood out from many energy storage device candidates due to their battery-level energy density, inherent flexibility, and safety. Nevertheless, the inevitable dendrite growth of Zn anodes and sharp capacity degradation at low-temperature seriously hinder their practical application. Herein, a dense ZnF2 solid electrolyte interface protective layer was constructed in situ on the Zn electrode surface by a simple chemical deposition method, effectively isolating the water molecules and alleviating the water-induced dendrite growth and parasitic reaction. To achieve the flexible ZIHS with environmental adaptability, a self-adhesion and anti-freezing zwitterionic hydrogel electrolyte was fabricated to afford superior ionic conductivity (97.1 mS cm-1), excellent anti-drying ability, and robust interfacial adhesion. Benefitting from the integrated merits of the as-designed electrolyte and electrode, the ZIHS delivered excellent mechanical adaptability, favorable energy density (103.9 Wh kg-1 at 270.1 W kg-1), broad operating temperature range (-40 to 40 °C), along with long-term cycling stability (12,000 cycles) with 90.3 % capacity retention at -25 °C. Notably, the unencapsulated ZIHS achieved exceptional electrochemical stability in an open environment. This finding provides valuable insights for constructing durable, flexible, and environmentally adaptable zinc-based energy storage systems.

Converting commercial Bi2O3 particles into Bi2O2Se@Bi4O8Se nanosheets for "rocking chair" zinc-ion batteries

The development of a low-cost, high-capacity, and insertion-type anode is key for promoting "rocking chair" zinc-ion batteries. Herein, commercial Bi2O3 (BiO) particles are transformed into Bi2O2Se@Bi4O8Se (BiOSe) nanosheets through a simple selenylation process. The change in morphology from commercial BiO particle to BiOSe nanosheet leads to an increased specific surface area of the material. The enhanced electronic/ionic conductivity results in its excellent electrochemical kinetics. Ex situ XRD and XPS tests prove the intercalation-type mechanism of BiO and BiOSe as well as the superior electrochemical reversibility of BiOSe compared to BiO. Furthermore, the H+/Zn2+ co-insertion mechanism of BiOSe is revealed. This makes BiOSe to have low discharge plateaus of 0.38/0.68 V, a high reversible capacity of 182 mA h g-1 at 0.1 A g-1, and a long cyclic life of 500 cycles at 1 A g-1. Besides, the BiOSe//MnO2 "rocking chair" zinc-ion battery offers a high capacity of ≈90 mA h g-1 at 0.2 A g-1. This work provides a reference for turning commercial material into high-performance anode for "rocking chair" zinc-ion batteries.

NH4 + Charge Carrier Coordinated H-Bonded Organic Small Molecule for Fast and Superstable Rechargeable Zinc Batteries

Organic small molecules as high-capacity cathodes for Zn-organic batteries have inspired numerous interests, but are trapped by their easy-dissolution in electrolytes. Here we knit ultrastable lock-and-key hydrogen-bonding networks between 2, 7-dinitropyrene-4, 5, 9, 10-tetraone (DNPT) and NH4 + charge carrier. DNPT with octuple-active carbonyl/nitro centers (H-bond acceptor) are redox-exclusively accessible for flexible tetrahedral NH4 + ions (H-bond donator) but exclude larger and rigid Zn2+ , due to a lower activation energy (0.14 vs. 0.31 eV). NH4 + coordinated H-bonding chemistry conquers the stability barrier of DNPT in electrolyte, and gives fast diffusion kinetics of non-metallic charge carrier. A stable two-step 4e- NH4 + coordination with DNPT cathode harvests a high capacity (320 mAh g-1 ), a high-rate capability (50 A g-1 ) and an ultralong life (60,000 cycles). This finding points to a new paradigm for H-bond stabilized organic small molecules to design advanced zinc batteries.

Progress of Photocapacitors

In response to the current trend of miniaturization of electronic devices and sensors, the complementary coupling of high-efficiency energy conversion and low-loss energy storage technologies has given rise to the development of photocapacitors (PCs), which combine energy conversion and storage in a single device. Photovoltaic systems integrated with supercapacitors offer unique light conversion and storage capabilities, resulting in improved overall efficiency over the past decade. Consequently, researchers have explored a wide range of device combinations, materials, and characterization techniques. This review provides a comprehensive overview of photocapacitors, including their configurations, operating mechanisms, manufacturing techniques, and materials, with a focus on emerging applications in small wireless devices, Internet of Things (IoT), and Internet of Everything (IoE). Furthermore, we highlight the importance of cutting-edge materials such as metal-organic frameworks (MOFs) and organic materials for supercapacitors, as well as novel materials in photovoltaics, in advancing PCs for a carbon-free, sustainable society. We also evaluate the potential development, prospects, and application scenarios of this emerging area of research.

All-Round Enhancement in Zn-Ion Storage Enabled by Solvent-Guided Lewis Acid-Base Self-Assembly of Heterodiatomic Carbon Nanotubes

Designing zincophilic and stable carbon nanostructures is critical for Zn-ion storage with superior capacitive activity and durability. Here, we report solvent-guided Lewis acid-base self-assembly to customize heterodiatomic carbon nanotubes, triggered by the reaction between iron chloride and α,α'-dichloro-p-xylene. In this strategy, modulating the solvent-precursor interaction through the optimization of solvent formula stimulates differential thermodynamic solubilization, growth kinetics, and self-assembly behaviors of Lewis polymeric chains, thereby accurately tailoring carbon nanoarchitectures to evoke superior Zn-ion storage. Featured with open hollow interiors and porous tubular topologies, the solvent-optimized carbon nanotubes allow low ion-migration barriers to deeply access the built-in zincophilic sites by high-kinetics physical Zn²⁺/CF₃SO₃^- adsorption and robust chemical Zn²⁺ redox with pyridine/carbonyl motifs, which maximizes the spatial capacitive charge storage density. Thus, as-designed heterodiatomic carbon nanotube cathodes provide all-round improvement in Zn-ion storage, including a high energy density (140 W h kg^-1), a large current activity (100 A g^-1), and an exceptional long-term cyclability (100,000 cycles at 50 A g^-1). This study provides appealing insights into the solvent-mediated Lewis pair self-assembly design of nanostructured carbons toward advanced Zn-ion energy storage.

Ni-doped Bi2O2CO3 nanosheet with H+/Zn2+ co-insertion for "rocking chair" zinc-ion battery

Developing insertion-type anode is key to advancing "rocking chair" zinc-ion batteries, though there are few reported insertion-type anodes. Herein, the Bi₂O₂CO₃ is a high-potential anode, with a special layered structure. A one-step hydrothermal method was used to prepare Ni-doped Bi₂O₂CO₃ nanosheet, and also a free-standing electrode consisting of Ni-Bi₂O₂CO₃ and CNTs was designed. Both cross-linked CNTs conductive networks and Ni doping improve charge transfer. Ex situ tests (XRD, XPS, TEM, etc.) reveal the H⁺/Zn²⁺ co-insertion mechanism of Bi₂O₂CO₃ and that Ni doping improves its electrochemical reversibility and structural stability. Therefore, this optimized electrode offers a high specific capacity of 159 mAh g^-1 at 100 mA g^-1, a suitable average discharge voltage of ≈0.400 V, and a long-term cycling stability of 2200 cycles at 700 mA g^-1. Besides, the Ni-Bi₂O₂CO₃//MnO₂ "rocking chair" zinc-ion battery (based on the total mass of cathode and anode) delivers a high capacity of ≈100 mAh g^-1 at 50.0 mA g^-1. This work provides a reference for designing high-performance anode in zinc-ion batteries.

Proton-Conductive Supramolecular Hydrogen-Bonded Organic Superstructures for High-Performance Zinc-Organic Batteries

With fast (de)coordination kinetics, the smallest and the lightest proton stands out as the most ideal charge carrier for aqueous Zn-organic batteries (ZOBs). Hydrogen-bonding networks with rapid Grotthuss proton conduction is particularly suitable for organic cathodes, yet not reported. We report the supramolecular self-assembly of cyanuric acid and 1,3,5-triazine-2,4,6-triamine into organic superstructures through in-plane H-bonds and out-of-plane π-π interaction. The supramolecular superstructures exhibit highly stable lock-and-key H-bonding networks with an ultralow activation energy for protonation (0.09 eV vs. 0.25 eV of zincification). Then, high-kinetics H⁺ coordination is prior to Zn²⁺ into protophilic C=O sites via a two-step nine-electron reaction. The assembled ZOBs show high-rate capability (135 mAh g^-1 at 150 A g^-1 ), high energy density (267 Wh kg^-1 _cathode ) and ultra-long life (50 000 cycles at 10 A g^-1 ), becoming the state-of-the-art ZOBs in comprehensive performances.

Highly Flexible K-Intercalated MnO2 /Carbon Membrane for High-Performance Aqueous Zinc-Ion Battery Cathode

The layered MnO₂ is intensively investigated as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs), but its commercialization is severely impeded by the challenging issues of the inferior intrinsic electronic conductivity and undesirable structural stability during the charge-discharge cycles. Herein, the lab-prepared flexible carbon membrane with highly electrical conductivity is first used as the matrix to generate ultrathin δ-MnO₂ with an enlarged interlayer spacing induced by the K⁺ -intercalation to potentially alleviate the structural damage caused by H⁺ /Zn²⁺ co-intercalation, resulting in a high reversible capacity of 190 mAh g^-1 at 3 A g^-1 over 1000 cycles. The in situ/ex-situ characterizations and electrochemical analysis confirm that the enlarged interlayer spacing can provide free space for the reversible deintercalation/intercalation of H⁺ /Zn²⁺ in the structure of δ-MnO₂ , and H⁺ /Zn²⁺ co-intercalation mechanism contributes to the enhanced charge storage in the layered K⁺ -intercalated δ-MnO₂ . This work provides a plausible way to construct a flexible carbon membrane-based cathode for high-performance AZIBs.

Stabilizing Interface pH by Mixing Electrolytes for High-Performance Aqueous Zn Metal Batteries

Aqueous zinc metal batteries with mild acidic electrolytes are considered promising candidates for large-scale energy storage. However, the Zn anode suffers from severe Zn dendrite growth and side reactions due to the unstable interfacial pH and the absence of a solid electrolyte interphase (SEI) protective layer. Herein, a novel and simple mixed electrolyte strategy is proposed to address these problems. The mixed electrolytes of 2 M ZnSO₄ and 2 M Zn (CF₃ SO₃ )₂ can efficiently buffer the interfacial pH and induce the in situ formation of the organic-inorganic SEI layer, which eliminates dendrite growth and prevents side reactions. As a result, Zn anodes in mixed electrolyte exhibit a lifespan enhancement over 400 times, endure stable cycling over 270 h at a high DOD of 62% and achieve high Zn plating/stripping reversibility with an average CE of 99.5% for 1000 cycles at 1 mA cm^-2 . The findings pave the way for developing practical electrolyte systems for Zn batteries.

Zn-Metal-Organic Framework Derived Ordered Mesoporous Carbon-Based Nanostructure for High-Performance and Universal Multivalent Metal Ion Storage

Metal-organic framework (MOF) derivatives promise great potential in energy storage and conversion because of their excellent tunability in both the active metal sites, organic links, and the overall structures down to atomic and up to mesoscale. Nevertheless, a big challenge is to precisely control and thoroughly understand the actual MOF-to-derivative conversion process to realize the template-free synthesis of the MOF-derived ordered mesoporous materials. Here, a class of ordered mesoporous N-doped carbon nanoflakes is presented with slit-shaped pores synthesized by one-step pyrolysis of Zn₁ Cu_x -MOF, where the Cu doping plays a critically important direction-inducing function on the dissociation of organic ligands during the pyrolysis. Benefiting from the uniquely ordered mesoporous structure and large specific surface area (910 m² g^-1 ), the Zn₁ Cu_x -MOF-derived ordered mesoporous carbon nanoflakes present outstanding electrochemical storage performance for multivalent metal ions, such as Mg²⁺ , Ca²⁺ , Co²⁺ , Ni²⁺ , Al³⁺ , and Zn²⁺ , demonstrating the universal nature of the slit-shaped pores in enabling the multivalent metal ions for energy storage. Moreover, the assembled flexible Zn-ion hybrid supercapacitor (ZHSC) delivers a high specific capacity of 134 mAh g^-1 at 0.5 A g^-1 , excellent cycling and mechanical stability, showing great application potential in the new generation energy storage devices.

Hierarchical accordion-like manganese oxide@carbon hybrid with strong interaction heterointerface for high-performance aqueous zinc ion batteries

Aqueous zinc ion batteries have attracted extensive concern as a promising candidate for large-scale energy storage because of their high theoretical specific capacity, low cost and inherent safety. However, the lacking of applicable cathode materials with outstanding electrochemical performance have severely hindered the further development of aqueous zinc ion batteries. Herein, we report a hierarchical accordion-like manganese oxide@carbon (MnO@C) hybrid with strong interaction heterointerface and comprehensively inquire into its electrochemical performance as cathode materials for aqueous zinc ion batteries. The unique hierarchical accordion-like layered structure coupling with strong interaction heterointerface between small MnO and carbon matrix efficaciously improve the ion/electron transfer process and enhance structure stability of the MnO@C hybrid. Benefitting from these unique advantages, the MnO@C hybrid bestows excellent specific capacity of 456 mAh g^-1 at 50 mA g^-1. Impressively, the MnO@C hybrid presents distinguished long-term cycling stability with fairly low decay rates of only 0.0079 % per cycle even over 2000 cycles at 2000 mA g^-1. Moreover, comprehensive characterizations are executed to elucidate the mechanism involved. Therefore, this work affords a new idea for developing outstanding performance manganese-based cathode materials for aqueous zinc ion batteries.