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

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.

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.

Multifunctionalized Supramolecular Cyclodextrin Additives Boosting the Durability of Aqueous Zinc-Ion Batteries

The poor cycling stability of aqueous zinc-ion batteries hinders their application in large-scale energy storage due to uncontrollable dendrite growth and harmful hydrogen evolution reactions. Here, we designed and synthesized an electrolyte additive, N-methylimidazolium-β-cyclodextrin p-toluenesulfonate (NMI-CDOTS). The cations of NMI-CD+ are more easily adsorbed on the abrupt Zn surface to regulate the deposition of Zn2+ and reduce dendrite generation under the combined action of the unique cavity structure with abundant hydroxyl groups and the electrostatic force. Meanwhile, p-toluenesulfonate (OTS-) is able to change the Zn2+ solvation structure and suppress the hydrogen evolution reaction by the strong interaction of Zn2+ and OTS-. Benefiting from the synergistic role of NMI-CD+ and OTS-, the Zn||Zn symmetric cell exhibits superior cycling performance as high as 3800 h under 1 mA cm-2 and 1 mA h cm-2. The Zn||V2O5 full battery also shows a high specific capacity (198.3 mA h g-1) under 2.0 A g-1 even after 1500 cycles, and its Coulomb efficiency is nearly 100% during the charging and discharging procedure. These multifunctional composite strategies open up possibilities for the commercial application of aqueous zinc-ion batteries.

Dynamically Ion-Coordinated Bipolar Organodichalcogenide Cathodes Enabling High-Energy and Durable Aqueous Zn Batteries

Bipolar organic cathode materials (OCMs) implementing cation/anion storage mechanisms are promising for high-energy aqueous Zn batteries (AZBs). However, conventional organic functional group active sites in OCMs usually fail to sufficiently unlock the high-voltage/capacity merits. Herein, we initially report dynamically ion-coordinated bipolar OCMs as cathodes with chalcogen active sites to solve this issue. Unlike conventional organic functional groups, chalcogens bonded with conjugated group undergo multielectron-involved positive-valence oxidation and negative-valence reduction, affording higher redox potentials and reversible capacities. With phenyl diselenide (PhSe-SePh, PDSe) as a proof of concept, it exhibits a conversion pathway from (PhSe)- to (PhSe-SePh)0 and then to (PhSe)+ as unveiled by characterization and theoretical simulation, where the diselenide bonds are periodically broken and healed, dynamically coordinating with ions (Zn2+ and OTF-). When confined into ordered mesoporous carbon (CMK-3), the dissolution of PDSe intermediates is greatly inhibited to obtain an ultralong lifespan without voltage/capacity compromise. The PDSe/CMK-3 || Zn batteries display high reversibility capacity (621.4 mAh gPDSe -1), distinct discharge plateau (up to 1.4 V), high energy density (578.3 Wh kgPDSe -1), and ultralong lifespan (12 000 cycles) at 10 A g-1, far outperforming conventional bipolar OCMs. This work sheds new light on conversion-type active site engineering for high-voltage/capacity bipolar OCMs towards high-energy AZBs.

Intermolecular Hydrogen Bonding Networks Stabilized Organic Supramolecular Cathode for Ultra-High Capacity and Ultra-Long Cycle Life Rechargeable Aluminum Batteries

Rechargeable aluminum batteries (RABs) are a promising candidate for large-scale energy storage, attributing to the abundant reserves, low cost, intrinsic safety, and high theoretical capacity of Al. However, the cathode materials reported thus far still face challenges such as limited capacity, sluggish kinetics, and undesirable cycle life. Herein, we propose an organic cathode benzo[i] benzo[6,7] quinoxalino [2,3-a] benzo [6,7] quinoxalino [2,3-c] phenazine-5,8,13,16,21,24-hexaone (BQQPH) for RABs. The six C=O and six C=N redox active sites in each molecule enable BQQPH to deliver a record ultra-high capacity of 413 mAh g-1 at 0.2 A g-1. Encouragingly, the intermolecular hydrogen bonding network and π-π stacking interactions endow BQQPH with robust structural stability and minimal solubility, enabling an ultra-long lifetime of 100,000 cycles. Moreover, the electron-withdrawing carbonyl group induces a reduction in the energy level of the lowest unoccupied molecular orbital and expands the π-conjugated system, which considerably enhances both the discharge voltage and redox kinetics of BQQPH. In situ and ex situ characterizations combined with theoretical calculations unveil that the charge storage mechanism is reversible coordination/dissociation of AlCl2 + with the N and O sites in BQQPH accompanied by 12-electron transfer. This work provides valuable insights into the design of high-performance organic cathode materials for RABs.

In situ Nafion-nanofilm oriented (002) Zn electrodeposition for long-term zinc-ion batteries

Dendrite growth and parasitic reactions of a Zn metal anode in aqueous media hinder the development of up-and-coming Zn-ion batteries. Optimizing the crystal growth after Zn nucleation is promising to enable stable cyclic performance of the anode, but directly regulating specific crystal plane growth for homogenized Zn electrodeposition remains highly challenging. Herein, a perfluoropolymer (Nafion) is introduced into an aqueous electrolyte to activate a thermodynamically ultrastable Zn/electrolyte interface for long-term Zn-ion batteries. The low adsorption energy (-2.09 eV) of Nafion molecules on Zn metal ensures the in situ formation of a Nafion-nanofilm during the first charge process. This ultrathin artificial solid electrolyte interface with zincophilic -SO3- groups guides the directional Zn2+ electrodeposition along the (002) crystal surface even at high current density, yielding a dendrite-free Zn anode. The synergic Zn/electrolyte interphase electrochemistry contributes an average coulombic efficiency of 99.71% after 4500 cycles for Zn‖Cu cells, and Zn‖Zn cells achieve an ultralong lifespan of over 7000 h at 5 mA cm-2. Besides, Zn‖MnO2 cells operate well over 3000 cycles. Even at -40 °C, Zn‖Zn cells achieve stable Zn2+ plating/stripping for 1200 h.

σ-Hole Effect-Induced Electroluminescence of Halogen Cocrystals for Determination of Iodide in Seawater

Developing new electrochemiluminescence (ECL) luminators with high stability, wide applicability, and strong designability is of great strategic significance to promote the ECL field to the frontier. Here, driven by the I···N bond, 1,3,5-trifluoro-2,4,6-triiodobenzene (TFTI) and 2,4,6-trimethyl-1,3,5-triazine (TMT) self-assembled into a novel halogen cocrystal (TFTI-TMT) through slow solution volatilization. Significant difference of charge density existed between the N atoms on TMT and the σ-hole of the I atoms on TFTI. Upon the induction of σ-hole effect, high-speed and spontaneous charge transferring from TMT to the σ-hole of TFTI occurred, stimulating exciting ECL signals. Besides, the σ-hole of the I atoms could capture iodine ions specifically, which blocked the original charge transfer from the N atoms to the σ-hole, causing the ECL signal of TFTI-TMT to undergo a quenching rate as high as 92.9%. Excitingly, the ECL sensing of TFTI-TMT toward I- possessed a wide linear range (10-5000 nM) and ultralow detection limit (3 nM) in a real water sample. The halogen cocrystal strategy makes σ-hole a remarkable new viewpoint of ECL luminator design and enables ECL analysis technology to contribute to addressing the environmental and health threats posed by iodide pollution.

Proton-selective coating enables fast-kinetics high-mass-loading cathodes for sustainable zinc batteries

The pressing demand for sustainable energy storage solutions has spurred the burgeoning development of aqueous zinc batteries. However, kinetics-sluggish Zn2+ as the dominant charge carriers in cathodes leads to suboptimal charge-storage capacity and durability of aqueous zinc batteries. Here, we discover that an ultrathin two-dimensional polyimine membrane, featured by dual ion-transport nanochannels and rich proton-conduction groups, facilitates rapid and selective proton passing. Subsequently, a distinctive electrochemistry transition shifting from sluggish Zn2+-dominated to fast-kinetics H+-dominated Faradic reactions is achieved for high-mass-loading cathodes by using the polyimine membrane as an interfacial coating. Notably, the NaV3O8·1.5H2O cathode (10 mg cm-2) with this interfacial coating exhibits an ultrahigh areal capacity of 4.5 mAh cm-2 and a state-of-the-art energy density of 33.8 Wh m-2, along with apparently enhanced cycling stability. Additionally, we showcase the applicability of the interfacial proton-selective coating to different cathodes and aqueous electrolytes, validating its universality for developing reliable aqueous batteries.

Boosting H+ Storage in Aqueous Zinc Ion Batteries via Integrating Redox-Active Sites into Hydrogen-Bonded Organic Frameworks with Strong π-π Stacking

In the emerging aqueous zinc ion batteries (AZIBs), proton (H+ ) with the smallest molar mass and fast (de)coordination kinetics is considered as the most ideal charge carrier compared with Zn2+ counterpart, however, searching for new hosting materials for H+ storage is still at its infancy. Herein, redox-active hydrogen-bonded organic frameworks (HOFs) assembled from diaminotriazine moiety decorated hexaazatrinnphthalene (HOF-HATN) are for the first time developed as the stable cathode hosting material for boosting H+ storage in AZIBs. The unique integration of hydrogen-bonding networks and strong π-π stacking endow it rapid Grotthuss proton conduction, stable supramolecular structure and inclined H+ storage. As a consequence, HOF-HATN displays a high capacity (320 mAh g-1 at 0.05 A g-1 ) and robust cyclability of (>10000 cycles at 5 A g-1 ) based on three-step cation coordination storage. These findings get insight into the proton transport and storage behavior in HOFs and provide the molecular engineering strategy for constructing well-defined cathode hosting materials for rechargeable aqueous batteries.

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.

Design and synthesis of п-conjugated aromatic heterocyclic materials with dual active sites and ultra-high rate performance for aqueous zinc-organic batteries

Acid anhydride cathode materials garner considerable interest for aqueous zinc ion batteries (AZIBs) due to ideal specific capacity and structural diversity, however, serious solubility leads to capacity degradation. Herein, 1,4,5,8-naphthalene tetracarboxylic acid dianhydride - 2,3-diamino phenothiazine (NTDP) featuring multiple active sites (6 with CN and 2 with CO) and large π-conjugated backbone, was designed and synthesized utilizing solid-phase method. The smallest energy gap (ΔE) and the lowest LUMO levels (against monomers) induced by multiple active sites and п-conjugated backbone with high aromaticity, NTDP exhibited excellent specific capacity (307.5 mA h g-1 under 0.05 A/g), ultrahigh rate performance (194.9 mA h g-1 under 20 A/g) and impressive cycling stability (190.0 mA h g-1 over 9000 cycles with a capacity retention of 91.2 % at 15 A/g). The reversible Zn2+ insertion/removal mechanism on multiple active centers (CO and CN) was proposed through XPS, FT-IR, and Raman. The specific capacity of the NTDP//zinc flexible cell was 112.6 mA h g-1 at 3 A/g under various folding angles (45°, 90°, 135°, and 180° bends), suggesting its practical potential for flexible devices. This work will offer opportunities for the rational design of battery structures.

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.

An approach to enhance carbon/polymer interface compatibility for lithium-ion supercapacitors

Developing high-efficiency and easy machining components, as well as high-performance energy storage components, is a pressing issue on the road to economic and social progress. Optimizing the interface compatibility between composites and promoting the efficient utilization of the electrochemical active sites are crucial factors in improving the electrochemical performance of composite electrode materials. To address this challenge, a carbon-based flexible lithium-ion supercapacitor positive material (Polyaniline @ Carbon Foam-Supercritical carbon dioxide (P@C-SC)) is synthesized using commercial melamine foam and aniline monomer. The synthesis process utilizes supercritical fluid technology, effectively solving the interface compatibility problem between the composite materials. Consequently, the electrochemical performance of the composite electrode materials is significantly improved. The supercapacitive properties of this material are investigated in 1 mol/L sulfuric acid (H2SO4) and lithium sulfate (Li2SO4) electrolytes using a three-electrode system. In H2SO4 electrolyte, the material exhibits a working voltage of up to 2.2 V and a specific capacitance of 898F/g (at 1 A/g), resulting in a maximum energy density of 50.8 Wh kg-1. Furthermore, this electrode demonstrates superior lithium storage performance, with a specific capacity of approximately 900 mAh/g (at 1 A/g) and a retention of about 400 mAh/g after 200 cycles, along with a coulomb efficiency of 100%. This work offers insights into the integrated design of composite materials with improved electrochemical properties and interface compatibility, thus providing potential applicability of supercritical fluids in the field of lithium-ion supercapacitors.

Carboxyl-Substituted Organic Molecule Assembled with MXene Nanosheets for Boosting Aqueous Na+ Storage

Aqueous alkali-ion batteries have enormous promise as a kind of safe, reliable, and sustainable energy technologies for power supplies. Although organic molecules with tunable and diverse configurations are potential electroactive materials, their inadequate redox activity and electron affinity hinder the practical application for aqueous alkali-ion storage. Herein, a novel electron-withdrawing carboxyl-substituted dipyridophenazine (CDPPZ) organic molecule is designed and synthesized for aqueous Na+ storage. Significantly, the introduction of carboxyl functional groups not only serves as additional redox-active sites for reversible Na+ coordination, but also causes the rearrangement of intramolecular electron cloud density to reduce the energy level, thereby ensuring the high redox activity and superior electron affinity of the CDPPZ molecule. For portable electronics, a self-supporting, adhesive-free, and flexible CDPPZ@MXene electrode is further constructed by incorporating highly redox-active CDPPZ molecule with MXene nanosheets, which delivers a fast, stable, and unrivaled aqueous Na+ storage capability with a high reversible capacity of 172.6 mAh cm-3 and excellent redox stability over 4000 cycles. In situ dynamic analysis combined with theoretical calculations illustrates the Na+ storage mechanism and corresponding coordinated pathway. Finally, a high-performance flexible aqueous Na-ion battery is fabricated with exceptional energy/power density and remarkable cycling lifespan, further confirming its promising application prospect.

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.

Hydrogen-Bond-Driven Peptide Nanotube Formation: A DFT Study

DFT calculations were carried out to examine geometries and binding energies of H-bond-driven peptide nanotubes. A bolaamphiphile molecule, consisting of two N-α amido glycylglycine head groups linked by either one CH2 group or seven CH2 groups, is used as a building block for nanotube self-assembly. In addition to hydrogen bonds between adjacent carboxy or amide groups, nanotube formation is also driven by weak C-H· · ·O hydrogen bonds between a methylene group and the carboxy OH group, and between a methylene group and an amide O=C group. The intratubular O-H· · ·O=C hydrogen bonds account for approximately a third of the binding energies. Binding energies calculated with the wB97XD/DGDZVP method show that the hydrocarbon chains play a stabilizing role in nanotube self-assembly. The shortest nanotube has the length of a single monomer and a diameter than increases with the number of monomers. Lengthening of the tubular structure occurs through intertubular O-H· · ·O=C hydrogen bonds. The average intertubular O-H· · ·O=C hydrogen bond binding energy is estimated to change with the size of the nanotubes, decreasing slightly towards some plateau value near 15 kcal/mol according to the wB97XD/DGDZVP method.

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.

Regulating the kinetics of zinc-ion migration in spinel ZnMn2O4 through iron doping boosted aqueous zinc-ion storage performance

Spinel ZnMn₂O₄ with a three-dimensional channel structure is one of the important cathode materials for aqueous zinc ions batteries (AZIBs). However, like other manganese-based materials, spinel ZnMn₂O₄ also has problems such as poor conductivity, slow reaction kinetics and structural instability under long cycles. Herein, ZnMn₂O₄ mesoporous hollow microspheres with metal ion doping were prepared by a simple spray pyrolysis method and applied to the cathode of aqueous zinc ion battery. Cation doping not only introduces defects, changes the electronic structure of the material, improves its conductivity, structural stability, and reaction kinetics, but also weakens the dissolution of Mn²⁺. The optimized 0.1 % Fe-doped ZnMn₂O₄ (0.1% Fe-ZnMn₂O₄) has a capacity of 186.8 mAh g^-1 after 250 charge-discharge cycles at 0.5 A g^-1 and the discharge specific capacity reaches 121.5 mAh g^-1 after 1200 long cycles at 1.0 A g^-1. The theoretical calculation results show that doping causes the change of electronic state structure, accelerates the electron transfer rate, and improves the electrochemical performance and stability of the material.

Copper nanodot-embedded nitrogen and fluorine co-doped porous carbon nanofibers as advanced electrocatalysts for rechargeable zinc-air batteries

Porous carbon-based electrocatalysts for cathodes in zinc-air batteries (ZABs) are limited by their low catalytic activity and poor electronic conductivity, making it difficult for them to be quickly commercialized. To solve these problems of ZABs, copper nanodot-embedded N, F co-doped porous carbon nanofibers (CuNDs@NFPCNFs) are prepared to enhance the electronic conductivity and catalytic activity in this study. The CuNDs@NFPCNFs exhibit excellent oxygen reduction reaction (ORR) performance based on experimental and density functional theory (DFT) simulation results. The copper nanodots (CuNDs) and N, F co-doped carbon nanofibers (NFPCNFs) synergistically enhance the electrocatalytic activity. The CuNDs in the NFPCNFs also enhance the electronic conductivity to facilitate electron transfer during the ORR. The open porous structure of the NFPCNFs promotes the fast diffusion of dissolved oxygen and the formation of abundant gas-liquid-solid interfaces, leading to enhanced ORR activity. Finally, the CuNDs@NFPCNFs show excellent ORR performance, maintaining 92.5% of the catalytic activity after a long-term ORR test of 20000 s. The CuNDs@NFPCNFs also demonstrate super stable charge-discharge cycling for over 400 h, a high specific capacity of 771.3 mAh g^-1 and an excellent power density of 204.9 mW cm^-2 as a cathode electrode in ZABs. This work is expected to provide reference and guidance for research on the mechanism of action of metal nanodot-enhanced carbon materials for ORR electrocatalyst design.

Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators

Zinc ion hybrid capacitors (ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applications. Carbon-based materials are deemed the competitive candidates for cathodes of ZIHC due to their cost-effectiveness, high electronic conductivity, chemical inertness, controllable surface states, and tunable pore architectures. In recent years, great research efforts have been devoted to further improving the energy density and cycling stability of ZIHCs. Reasonable modification and optimization of carbon-based materials offer a remedy for these challenges. In this review, the structural design, and electrochemical properties of carbon-based cathode materials with different dimensions, as well as the selection of compatible, robust current collectors and separators for ZIHCs are discussed. The challenges and prospects of ZIHCs are showcased to guide the innovative development of carbon-based cathode materials and the development of novel ZIHCs.