Extending Cycling Life Beyond 300 000 Cycles in Aqueous Zinc Ion Capacitors Through Additive Interface Engineering.

Developing low-cost and long-cycling-life aqueous zinc (Zn) ion capacitors (AZICs) for large-scale electrochemical energy storage still faces the challenges of dendritic Zn deposition and interfacial side reactions. Here, an interface engineering strategy utilizing a dibenzenesulfonimide (BBI) additive is employed to enhance the stability of the Zn metal anode/electrolyte interface. The first-principles calculation results demonstrate that BBI anions can be chemically adsorbed on Zn metal. Meanwhile, the experimental results confirm that the BBI-Zn interfacial layer converts the original water-richelectric double layer (EDL) into a water-poor EDL, effectively inhibiting the water related parasitic reaction at the electrode/electrolyte interface. In addition, the BBI-Zn interfacial layer introduces an additional Zn ions (Zn2+) migration energy barrier, increasing the Zn2+ de-solvation activation energy, consequently raising the Zn2+ nucleation overpotential, and thus achieving the compact and uniform Zn deposition behavior. Furthermore, the solid electrolyte interphase (SEI) layer derived from the BBI-Zn interfacial layer during cycling can further maintain the interfacial stability of the Zn anode. Owing to the above favorable features, the assembled AZIC exhibits an ultra-long cycling life of over 300 000 cycles based on the additive engineering strategy, which shows application prospects in high-performance AZICs.

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.

Long-lifespan Zinc-ion Capacitors Enabled by Anodes Integrated with Interconnected Mesoporous Chitosan Membranes through Electrophoresis-driven Phase Separation.

The advancement of highly secure and inexpensive aqueous zinc ion energy storage devices is impeded by issues, including dendrite growth, hydrogen evolution and corrosion of zinc anodes. It is essential to modify the interface of zinc anodes that homogenizes ion flux and facilitates highly reversible zinc planarized deposition and stripping. Herein, by coupling zinc ion coordination with acid-base neutralization under the driving of electrophoresis, manageable mesoscopic phase separation for constructing chitosan frameworks was achieved, thereby fabricating interconnected mesoporous chitosan membranes based heterogeneous quasi-solid-state electrolytes integrated with anodes. The framework is constructed by twisted chitosan nanofiber bundles, forming a three-dimensional continuous spindle-shaped pore structure. With this framework, the electrolyte provides exceptional ion conductivity of 25.1 mS cm-1 , with a puncture resistance strength of 2.3 GPa. In addition, the amino groups of chitosan molecule can make the surface of the framework positively charged. Thus, reversible zinc planarized deposition is successfully induced by the synergistic effect of stress constraint and electrostatic modulation. As a result, as-assembled zinc ion capacitor has an excellent cycle life and sustains the capacity by over 95 % after 20000 cycles at a current density of 5 A g-1 . This research presents a constructive strategy for stable electrolytes-integrated zinc anodes.

Intrinsically Decoupled Coordination Chemistries Enable Quasi-Eutectic Electrolytes with Fast Kinetics toward Enhanced Zinc-Ion Capacitors.

Eutectic electrolytes show potential beyond conventional low-concentration electrolytes (LCEs) in zinc (Zn)-ion capacitors (ZICs) yet suffer from high viscosity and sluggish kinetics. Herein, we originally propose a universal theory of intrinsically decoupling to address these issues, producing a novel electrolyte termed "quasi-eutectic" electrolyte (quasi-EE). Joint experimental and theoretical analyses confirm its unique solution coordination structure doped with near-LCE domains. This enables the quasi-EE well inherit the advanced properties at deep-eutectic states while provide facilitated kinetics as well as lower energy barriers via a vehicle/hopping-hybridized charge transfer mechanism. Consequently, a homogeneous electroplating pattern with much enhanced Sand's time is achieved on the Zn surface, followed by a twofold prolonged service-life with drastically reduced concentration polarization. More encouragingly, the quasi-EE also delivers increased capacitance output in ZICs, which is elevated by 12.4 %-144.6 % compared to that before decoupling. Furthermore, the pouch cell with a cathodic mass loading of 36.6 mg cm-2 maintains competitive cycling performances over 600 cycles, far exceeding other Zn-based counterparts. This work offers fresh insights into eutectic decoupling and beyond.

Micro/Meso-Porous Double-Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc-Ion Capacitor.

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g-1 in supercapacitor and specific capacitance of 260 F g-1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Effects of Anion Carriers on Capacitance and Self-Discharge Behaviors of Zinc Ion Capacitors.

Pseudocapacitive behavior and ion hybrid capacitors can improve the energy density of supercapacitors, but research has only considered the reaction of cations during the electrochemical process, leading to a flawed mechanistic understanding. Here, the effects of various anions carriers on the electrochemical behaviors of titanium nitride-based zinc ion capacitor (Zn-TiN capacitor) were explored. DFT calculations revealed the stable structure of TiN-SO4 after adsorbed process, enabling SO4 2- participate in the electrochemical process and construct a two-step adsorption and intercalation energy storage mechanism, improving the capacitance and anti-self-discharge ability of the Zn-TiN capacitor, which delivered an ultrahigh capacitance of 489.8 F g-1 and retained 83.92 % of capacitance even after 500 h resting time. An energy storage system involving anions in the electrochemical process can improve capacitance and anti-self-discharge ability of ion hybrid capacitors.

A Corrosion-Resistant and Dendrite-Free Zinc Metal Anode in Aqueous Systems.

Rechargeable aqueous zinc (Zn) ion-based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual-functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle-life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal-based energy storage systems.

Multifunctional Zincophilic Hydrogel Electrolyte with Abundant Hydrogen Bonds for Zinc-Ion Capacitors and Supercapacitors.

The new-generation flexible Zn-ion capacitors (ZICs) require multifunctionality and environmental adaptability for practical applications. This essentially means that hydrogel electrolytes are expected to possess superior mechanical properties, temperature resistance, and tunable interface properties to resist flexibility loss and performance degradation over a wide operating temperatures range. Herein, a multifunctional polyzwitterionic hydrogel electrolyte (PAM/LA/PSBMA) with wide operating temperatures, excellent tensile ability, high water retention, and self-adhesion is designed. Molecular dynamics simulations and experimental results show that polar functional groups (-COO-, -SO3-, -C═O, and -NHCO-) in the hydrogel can form abundant hydrogen bonds with water molecules, which can destroy the original hydrogen bonds (HBs) network between the water molecules and have a low freezing point. It can also form coordination with Zn2+, so that the deposition of Zn2+ electric field homogenization effectively alleviates the growth of Zn dendrites. On this basis, the constructed Zn//Zn cell can be stably cycled 290 h at 10 mA cm-2 (1 mA h cm-2). The constructed ZICs and supercapacitor have a high specific capacitance, excellent energy density, good ionic conductivity, and long cycling stability. This study provides guidance on molecular design for the development of integrated multifunctional smart electronic devices that are environmentally adaptable, resistant to drying, and highly flexible.

Ethanol Solvent Used in Constructing Ultra-Low-Temperature Zinc-Ion Capacitors with a Long Cycling Life.

Zinc-ion capacitors (ZICs) gain enormous attraction for their high power density, low cost, and long life, but their poor low-temperature performance is still a challenge due to the dissatisfactory freezing point of aqueous electrolyte solution. It is difficult for them to meet the requirements in cold environments as well as the extreme low temperature and severe temperature fluctuations in aerospace environments. Herein, ethanol (EtOH) solvent with ZnCl2 is used as an electrolyte to address these issues. Benefiting from the low freezing point (-114 °C) of EtOH, the ZIC with the ZnCl2/EtOH electrolyte can be operated at an ultralow temperature of -78 °C. It also demonstrates long cycling stability over 30,000 cycles. Such an enhancement is attributed to the unique properties of [ZnCl(EtOH)5]+ that can stabilize the coordination environment of Zn2+, slow the diffusivity, and raise the nucleation overpotential, leading to uniform Zn plating/stripping and subsequently suppressing dendrite growth. Meanwhile, the lower activation energy in ZnCl2/EtOH than that in ZnSO4/H2O electrolytes endows the ZIC excellent charge transfer properties. This work provides a fascinating electrolyte and a feasible pathway for ultra-low-temperature ZICs with a long cycling life.

Electrolyte for High-Energy- and Power-Density Zinc Batteries and Ion Capacitors.

Growth of dendrites, limited coulombic efficiency (CE), and the lack of high-voltage electrolytes restrict the commercialization of zinc batteries and capacitors. These issues are resolved by a new electrolyte, based on the zinc(II)-betaine complex [Zn(bet)2 ][NTf2 ]2 . Solutions in acetonitrile (AN) avoid dendrite formation. A Zn||Zn cell operates stably over 10 110 h (5055 cycles) at 0.2 mA cm-2 or 110 h at 50 mA cm-2 , and has an area capacity of 113 mAh cm-2 at 80% depth of discharge. A zinc-graphite battery performs at 2.6 V with a midpoint discharge-voltage of 2.4 V. The capacity-retention at 3 A g-1 (150 C) is 97% after 1000 cycles and 68% after 10 000 cycles. The charge/discharge time is about 24 s at 3.0 A g-1 with an energy density of 49 Wh kg-1 at a power density of 6864 W kg-1 based on the cathode. A zinc||activated-carbon ion-capacitor (coin cell) exhibits an operating-voltage window of 2.5 V, an energy density of 96 Wh kg-1 with a power density of 610 W kg-1 at 0.5 A g-1 . At 12 A g-1 , 36 Wh kg-1 , and 13 600 W kg-1 are achieved with 90% capacity-retention and an average CE of 96% over 10 000 cycles. Quantum-chemical methods and vibrational spectroscopy reveal [Zn(bet)2 (AN)2 ]2+ as the dominant complex in the electrolyte.

Porous Carbon Coated on Cadmium Sulfide-Decorated Zinc Oxide Nanorod Photocathodes for Photo-accelerated Zinc Ion Capacitors.

The development of devices with dual solar energy-harvesting and storage functionalities has recently gained significant traction for off-grid power supply. In their most compact embodiment, these devices rely on the same electrode to harvest and store energy; however, in this approach, the development of energy-efficient photoelectrodes with intrinsic characteristics of good optical and electrochemical activities remains challenging. Here, we propose photoelectrodes with a porous carbon coated on a zinc oxide-cadmium sulfide heterostructure as an energy-efficient photocathode for photo-accelerated zinc ion capacitors (Photo-ZICs). The Photo-ZICs harvest light energy and store charge simultaneously, resulting in efficient charge storage performance under illumination compared to dark conditions (∼99% capacity enhancement at 500 mA g-1 under illumination compared to dark conditions). The light absorption ability and charge separation efficiency achieved by the photocathodes meet the requirements for photo-ZIC applications. Moreover, Photo-ZICs display stable charge storage capacities over long-term cycling, that is, ∼1% capacity loss after 10,000 cycles.

Integrated Construction of a Long-Life Stretchable Zinc-Ion Capacitor.

The major challenge in achieving high-performance stretchable zinc-ion energy-storage devices is the combination of stretchable dendrite-free zinc negative electrodes and sufficient bonding between components (current collector, electrode, separator, and package). Herein, based on a series of physicochemically tunable self-healing polyurethanes, an elastic current collector is prepared through a swelling-induced wrinkling method, and then a stretchable zinc negative electrode prepared through in situ confined electroplating. The elastic current collector has a nano-network structure with polyurethane encapsulation, and exhibits both geometric and intrinsic stretchability. The stretchable zinc negative electrode formed in situ has high electrochemical activity and exhibits an excellent cycle life under the protection of a Zn2+ -permeable coating. Furthermore, fully polyurethane-based stretchable zinc-ion capacitors are assembled through in situ electrospinning and hot-pressing techniques. Due to the high stretchability of the components and the interfusion of the matrixes, the integrated device exhibits excellent deformability and desirable electrochemical stability. This work provides a systematic construction plan for stretchable zinc-ion energy-storage devices in three aspects: material synthesis, component preparation, and device assembly.

High Energy and Power Zinc Ion Capacitors: A Dual-Ion Adsorption and Reversible Chemical Adsorption Coupling Mechanism.

Zinc ion capacitors (ZICs) hold great promise in large-scale energy storage by inheriting the superiorities of zinc ion batteries and supercapacitors. However, the mismatch of kinetics and capacity between a Zn anode and a capacitive-type cathode is still the Achilles' heel of this technology. Herein, porous carbons are fabricated by using tetra-alkali metal pyromellitic acid salts as precursors through a carbonization/self-activation procedure for enhancing zinc ion storage. The optimized rubidium-activated porous carbon (RbPC) is verified to hold immense surface area, suitable porosity structure, massive lattice defects, and luxuriant oxygen functional groups. These structural and compositional merits endow RbPC with the promoted zinc ion storage capability and more matchable kinetics and capacity with a Zn anode. Consequently, RbPC-based ZIC delivers a high specific energy of 178.2 W h kg-1 and a peak power density of 72.3 kW kg-1. A systematic ex situ characterization analysis coupled with in situ electrochemical quartz crystal microbalance tests reveal that the preeminent zinc ion storage properties are ascribed to the synergistic effect of the dual-ion adsorption and reversible chemical adsorption of RbPC. This work provides an efficient strategy to the rational design and construction of high-performance electrodes for ZICs and furthers the fundamental understanding of their charge storage mechanisms or extends the understanding toward other electrochemical energy storage devices.

Eliminating the Micropore Confinement Effect of Carbonaceous Electrodes for Promoting Zn-Ion Storage Capability.

Zinc-ion capacitors (ZICs) are promising technology for large-scale energy storage by integrating the attributes of supercapacitors and zinc-ion batteries. Unfortunately, the insufficient Zn2+ -storage active sites of carbonaceous cathode materials and the mismatch of pore sizes with charge carriers lead to unsatisfactory Zn2+ storage capability. Herein, new insights for boosting Zn2+ storage capability of activated nitrogen-doped hierarchical porous carbon materials (ANHPC-x) are reported by effectively eliminating the micropore confinement effect and synchronously elevating the utilization of active sites. Therefore, the best-performed ANHPC-2 delivers impressive electrochemical properties for ZICs in terms of excellent capacity (199.1 mAh g-1 ), energy density (155.2 Wh kg-1 ), and durability (65 000 cycles). Systematic ex situ characterizations together with in situ electrochemical quartz crystal microbalance and Raman spectra measurements reveal that the remarkable electrochemical performance is assigned to the synergism of the Zn2+ , H+ , and SO4 2- co-adsorption mechanism and reversible chemical adsorption. Furthermore, the ANHPC-2-based quasi-solid-state ZIC demonstrates excellent electrochemical capability with an ultralong lifespan of up to 100 000 cycles. This work not only provides a promising strategy to improve the Zn2+ storage capability of carbonaceous materials but also sheds lights on charge-storage mechanism and advanced electrode materials' design for ZICs toward practical applications.