Zn-ion Hybrid Supercapacitors Research Articles

Preparation of B/N co-doped carbon nanosheets and their electrochemical performance in Zn-ion redox capacitors

The low energy density for conventional supercapacitors has limited their further application in a large scale. To enhance the energy density of supercapacitor, a novel redox Zn-ion supercapacitor is fabricated by using B, N codoped carbon nanosheets as cathode material and hydroquinone as redox electrolyte. The B, N co-doping is found to be beneficial for the enhanced electrochemical performance, and the introduced redox electrolyte has increased the capacitance of supercapacitor greatly. The B, N codoped carbon nanosheets shows a capacity of 168 mAhg−1 in the hydroquinone based redox electrolyte at 2 Ag−1, nearly 2 times as that (83 mAhg−1) in conventional Zn-ion electrolyte. Density functional calculation shows B, N- dual doping can increase the adsorption capability of carbon toward hydroquinone. This work shows that the combination of cathode material modification and redox electrolyte can enhance Zn-ion hybrid supercapacitor.

High-performance Zn-ion hybrid supercapacitor enabled by a lightweight polyimide-based anode

High-performance Zn-ion hybrid supercapacitor enabled by a lightweight polyimide-based anode

Negatively Charged Hydrophobic Carbon Nano-Onion Interfacial Layer Enabling High-Rate and Ultralong-Life Zn-Based Energy Storage.

Zn-based electrochemical energy storage (EES) systems are attracting more attention, whereas their large-scale application is restricted by the dendrite and parasitic reaction-caused unstable Zn anodes. Herein, a negatively charged hydrophobic carbon nano-onion (CNO) interfacial layer is proposed to realize ultrastable and high-rate Zn anodes, enabling high-performance Zn-based EES. For the CNO interfacial layer, its hydrophobicity not only blocks active water but also reduces the Zn2+ desolvation barrier, and meanwhile, the negatively-charged CNO nanoparticles adsorb Zn2+ and repel SO4 2- to homogenize Zn2+ flux, accelerate Zn2+ desolvation and suppress the self-corrosion of Zn anodes. Besides, the conductive CNO interfacial layer increases the surface area for the Zn deposition to reduce local current density. Consequently, under the modulation of the CNO interfacial layer, Zn plating/stripping exhibits impressive reversibility with an average Coulombic efficiency of 99.4% over 800 cycles, and Zn anodes present significantly enhanced electrochemical stability and rate performance, whose operation lifetime exceeds 2000h at 1mAcm-2 and 350h even at 10mAcm-2 . Moreover, high-rate and ultralong-life Zn-ion hybrid supercapacitors are achieved with the CNO interfacial layer-modulated Zn anode and activated CNO cathode. This work provides new thinking in regulating the Zn deposition interface to realize high-performance Zn-based EES.

A durable quasi-solid-state zinc ion hybrid supercapacitor with coal tar pitch derived carbon material

In this work, a porous carbon material (KCC) was prepared by using the coal tar pitch carbon source and energeticZn-basedmetal–organicframework template, which exhibits a high specific surface area (1527.0 m2/g), a high capacity of 133.9 mAh/g, excellent rate performance (50.4% retention at 20 A/g), and long-term cycle stability (103.3% capacity retention after 10,000 cycles). Additionally, a gelatin/polyacrylamide/κ-carrageenan/Zn(CF3SO3)2 hydrogel electrolyte (G/PAAm/κ-CG/Zn(CF3SO3)2) was also constructed. The quasi-solid-state Zn-ion hybrid supercapacitor based on KCC and G/PAAm/κ-CG/Zn(CF3SO3)2 delivers a specific capacity of 85.0 mAh/g at 0.25 A/g, 50.5% capacity retention at 20 A/g, high energy/power densities, and satisfactory cycle stability.

Hierarchically porous N-doped carbon nanosheet aerogel cathodes for Zn-ion hybrid supercapacitors with superhigh energy density

Carbon nanomaterials with large specific surface area and high electronic conductivity, have been widely used as capacitive cathode materials for Zn-ion hybrid supercapacitors. Doping of heteroatoms and regulation of pore structure are crucial for boosting the energy storage performances of the carbon-based cathodes. We propose a N-doped carbon nanosheet aerogel (N-CNAG) with high active N content and hierarchically porous structure, which can be prepared by the bubble-templated polymerization of Py and the carbonization of the PPy nanosheet hydrogel (PPyNHG). The high active N content of N-CNAG can produce high pseudocapacitance through the N-dependent electrochemical redox reactions. The hierarchically porous structure of N-CNAG can facilitate fast electrolyte ion diffusion. Based on the Zn anode and the N-CNAG cathode, the Zn-ion hybrid supercapacitor can provide a remarkable specific capacitance of 706 F g−1 at 1 A g−1 and the rate capability of 50 % from 1 A g−1 to 5 A g−1, mainly attributed to the high active N content and the hierarchically porous structure of N-CNAG. Additionally, this Zn-ion hybrid supercapacitor provides the superhigh energy density of 392 Wh kg−1 at 1 kW kg−1 and the cycling stability of 87.4 % after 10,000 cycles, holding great potential for developing high-energy-density Zn-ion hybrid supercapacitors.

Manipulating cation-water chemistry to inhibit hydrogen evolution of zinc metal anodes

The electrochemical behavior of zinc metal anodes is dominated by the interfacial chemistry between the anode and the electrolyte. The local enrichment of cation-solvent complexes with strong interactions in the Helmholtz plane can lead to the evolution of hydrogen on the Zn anode surface during cycling. To tackle this issue, we propose the addition of low doses of N-dimethylformamide (DMF) solvent into 2 M of ZnSO4 electrolyte (D-ZS) to inhibit hydrogen evolution from water splitting and dendrite growth. Molecular dynamics simulation and nuclear magnetic resonance spectroscopy reveal that high donor-number DMF molecules replace part of H2O molecules, thereby reducing the amount of H2O in the solvated sheath of Zn2+. Furthermore, density functional theory calculations demonstrate that DMF increases the lowest unoccupied molecular orbital level of bound water owing to reduced Zn2+ cation-water interaction, preventing the breakage of O−H bond and reducing side reactions of Zn anodes. In addition, the desolvated DMF molecules prefer to adsorb on the zinc anode surface, hindering the migration of Zn2+ to low surface-energy positions that could lead to dendritic formation. As a result, a symmetric cell with D-ZS electrolyte can operate for over 1970 h at 0.5 mA cm−2 for 0.25 mAh cm−2, and Zn-ion hybrid supercapacitors achieve an exemplary cycle performance (93% of capacity retention rate after 30,000 cycles at 2 A g−11). The present work provides a roadmap for regulating electrolyte structure to inhibit hydrogen evolution of zinc metal anodes by manipulating Zn2+ cation-water chemistry.

A Hollow-Shaped ZIF-8-N-Doped Porous Carbon Fiber for High-Performance Zn-Ion Hybrid Supercapacitors

The advantages of low cost, high theoretical capacity, and dependable safety of aqueous zinc ion hybrid supercapacitors (ZHSCs) enable their promising use in flexible and wearable energy storage devices. However, achieving extended cycling stability in ZHSCs is still challenged by the limited availability of carbon cathode materials that can effectively pair with zinc anode materials. Here, we report a method for synthesising heteroatom-doped carbon nanofibers using electrostatic spinning and metal-organic frameworks (specifically ZIF-8). Assembled Zn//ZPCNF-1.5 ZHSCs exhibited 193 mA h g−1 specific capacity at 1 A g−1 and 162.6 Wh kg−1 energy density at 841.2 kW kg−1. Additionally, the device showed an ultra-long cycle life, maintaining 98% capacity after 20,000 cycles. Experimental analysis revealed an increase in the number of pores and active sites after adding ZIF-8 to the precursor. Furthermore, N doping effectively enhanced Zn2+ ions chemical adsorption and improved Zn-ion storage performance. This work provides a feasible design strategy to enhance ZHSC energy storage capability for practical applications.

Vacancy and surface modulation engineering of CuxCo3-xO4 nanowires as an advanced cathode for zinc-ion hybrid supercapacitors

Zn-ion hybrid supercapacitors (ZHSCs) with high power and energy density have great potential in energy storage applications such as hybrid vehicles and renewable energy storage. However, the large radius of hydrated Zn2+-ions hampers their efficient storage in micropores with limited pore sizes, resulting in limited weight ratio capacitance and poor rate capability of ZHSCs. In this study, we developed the novel N-doped and oxygen vacancy-rich CCO nanowires (N-Ov-CCO@CC) architecture with the help of Chemical Vapor Deposition (CVD). Due to the guiding synergy of N-doping, defects, and surface engineering, N-Ov-CCO@CC exhibits significantly enhanced electrochemical performance. The N-Ov-CCO@CC single electrode exhibits excellent charge storage properties, including a high capacitance of 1480.7 F/g at 1 A/g, excellent rate-capability (88.4 % at 20 A/g), and excellent cycle stability of up to 90.1 % for 5000 cycles. The charge storage mechanism was analyzed by ex-situ XRD and XPS, and it reveals that the pseudocapacitive charge storage characteristics are dominant. Operating in the potential range of 1.2–2.0 V, the N-Ov-CCO@CC//Zn-ZHSC provides a high capacitance of 308.2 F/g at 1 A/g, excellent rate capability (86.9 % at 10 A/g), long lifetime (97 % after 10,000 cycles), and high specific energy/power (134.32 Wh/kg at 9507.6 W/kg). Density function theory (DFT) validations show that the N-Ov-CCO system possesses higher conductivities than Ov-CCO and pristine CCO. This work provides an effective strategy for constructing multifunctional electrochemical energy materials for ZHSCs.

Phosphorus-Mediated Local Charge Distribution of N-Configuration Adsorption Sites with Enhanced Zincophilicity and Hydrophilicity for High-Energy-Density Zn-Ion Hybrid Supercapacitors.

Tailor-made carbonaceous-based cathodes with zincophilicity and hydrophilicity are highly desirable for Zn-ion storage applications, but it remains a great challenge to achieve both advantages in the synthesis. In this work, a template electrospinning strategy is developed to synthesize nitrogen and phosphorous co-doped hollow porous carbon nanofibers (N, P-HPCNFs), which deliver a high capacity of 230.7 mAh g-1 at 0.2 A g-1 , superior rate capability of 131.0 mAh g-1 at 20 A g-1 , and a maximum energy density of 196.10Wh kg-1 at the power density of 155.53W kg-1 . Density functional theory calculations (DFT)reveal that the introduced P dopants regulate the distribution of local charge density of carbon materials and therefore facilitate the adsorption of Zn ions due to the increased electronegativity of pyridinic-N. Ab initio molecular dynamics (AIMD)simulations indicate that the doped P species induce a series of polar sites and create a hydrophilic microenvironment, which decreases the impedance between the electrode and the electrolyte and therefore accelerates the reaction kinetics. The marriage of ex situ/in situ experimental analyses and theoretical simulations uncovers the origin of the enhanced zincophilicity and hydrophilicity of N, P-HPCNFs for energy storage, which accounts for the faster ion migration and electrochemical processes.

CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

Poly(ionic liquid) additive: Aqueous electrolyte engineering for ion rectifying and calendar corrosion relieving

Apart from the key function of regulating zinc (Zn) ions transport kinetics of aqueous Zn-ion energy storage devices, electrolytes also play an important role in restraining the inevitable parasitic reaction and intense dendrite growth on the Zn anode interface. Hence, in this work, a novel poly(ionic liquid) (poly(1-carboxymethyl-3-vinylimidazolium bromide, PCMVIm) additive is rationally designed and applied for Zn ion electrolyte optimization. The carboxyl-rich poly(ionic liquid) additive with polymer chain structure stabilizes the electrode/electrolyte interphase via strong Zn adsorption, and remarkably promotes uniform Zn deposition on its surface, endowing it with strong ion rectifying effects. The PCMVIm additive also effectively reduces byproduct formations on the Zn anode and maintains stable surface impedance against calendar corrosion. Notably, the optimized electrolyte with a 5 % PCMVIm additive ratio exhibits enhanced ionic conductivity (15.13 mS·cm−1) and remarkable Coulombic efficiencies of over 99.4 % for 700 h. The exceptional electrochemical performance of the modified electrolyte endows ultra-long cycle stability, high Coulombic efficiency, and outstanding rate capability for both Zn ion hybrid supercapacitor and Zn ion battery applications. This study provides a novel electrolyte additive engineering for durable aqueous energy storage devices.

Stable β-form zinc phthalocyanine cathodes for flexible Zn-ion hybrid supercapacitors with ultra-long cycling life

Metal phthalocyanine with a unique π-conjugated structure, has shown extraordinary promise for electrocatalysis, batteries and supercapacitors. High-performance Zn-ion hybrid supercapacitors make high demands on the energy storage mechanisms of metal phthalocyanine. We propose a β-form zinc phthalocyanine (ZnPc) molecular crystal as a cathode material for flexible Zn-ion hybrid supercapacitors. The β-ZnPc is facilely synthesized through the annealing treatment of the original ZnPc, which is previously fabricated through a ring-closure reaction assisted by catalysis of sodium methanol and ultrasonic treatment. The structural transformation of ZnPc from α-ZnPc to β-ZnPc is demonstrated at the annealing temperature from 200 °C to 300 °C, probably attributed to the short-range neighbor interaction between the adjacent ZnPc molecular layers. The β-ZnPc electrode exhibits the higher specific capacitance and the better rate capability than those of the α-ZnPc electrode, mainly due to its higher specific surface area and more abundant pore structure. The electron density and adsorption energy of ZnPc are theoretically calculated, revealing the active N sites for the reversible adsorption/desorption of Zn2+. The flexible Zn-ion hybrid supercapacitor provides the maximum energy density of 86.2 Wh kg−1 at 0.22 kW kg−1, and maintains the capacitance retention of 73.4% after 100,000 cycles, opening up a new avenue for developing high-energy and long-life Zn-ion hybrid supercapacitors.

Non-Aqueous Zn-Ion Hybrid Supercapacitors: Acetonitrile vs Propylene Carbonate Based Electrolyte

The development of high efficiency energy storage systems is increasingly important as these systems enable utilize energy from renewable sources and reduce greenhouse gas evolution caused by fuel combustion technologies at the same time. Electrochemical characteristics of Zn-ion hybrid supercapacitor (ZIHS) cells based on 1 M acetonitrile and propylene carbonate electrolytes in zinc tetrafluoroborate (Zn(BF4)2), zinc di[bis(trifluoromethylsulfonyl)imide] (Zn(TFSI)2) and zinc trifluoromethanesulfonate (Zn(OTf)2) have been studied using cyclic voltammetry, constant current charge/discharge and electrochemical impedance methods. The Ragone plots have been calculated from constant power measurement data. Very high energy and power densities (80 Wh kg−1 and 21.2 kW kg−1) have been calculated for 1 M Zn(BF4)2/AN based Zn-ion hybrid supercapacitor. Some assembled ZIHSs had shown excellent cycling and energy stability over 20000 cycles.

N-functionalization and defect engineering in ZnCo2O4 nanosheets boosted the performance of Zn-ion hybrid supercapacitor

Transition-metal oxides are a class of promising pseudocapacitive materials for high energy density supercapacitors, while their low intrinsic conductivity and remarkable volume expansion deteriorate the electrochemical properties. Herein, we develop a binder-free mesoporous architecture supported on a carbon cloth (CC) substrate based on the nitrogen (N)-doped and oxygen vacancy (Ov)-rich zinc cobalt oxide nanosheets (denoted by N-Ov-ZCO@CC). Because of the instructive synergy of doping, defect, and surface engineering achieved by N-functionalization, the N-Ov-ZCO@CC exhibits significantly enhanced electrochemical properties. The N-Ov-ZCO@CC single electrode exhibited a high capacitance of 2166.4 F/g at 1 A/g with superb rate-capability (91.2% at 20 A/g) and superior cycling stability of 98.99% up to 5,000 cycles. In addition, a zinc-ion hybrid supercapacitor (ZHSC) device, assembled with the N-Ov-ZCO@CC as the cathode and Zn-foil as the anode, shows a high energy density of 95.35 Wh/kg at the power density of 10,008 W/kg, superior to most state-of-the-art ZHSCs. This work provides an effective strategy for constructing multifunctional electrochemical energy materials for ZHSCs.

Hydrosoluble diacetone acrylamide as an electrolyte additive for high-capacity Zn-ion hybrid supercapacitors

Rational optimization of electrolytes is of great concern for the improvement of Zn-ion hybrid supercapacitors. Polyacrylamide hydrogels as gel electrolytes, usually suffer from slow electromigration of the hydrated Zn2+ ions limited by the complexation of acylamino groups with the hydrated Zn2+ ions. We propose a new strategy of adding hydrosoluble diacetone acrylamide (DAAM) as an electrolyte additive into the Zn(CF3SO3)2 electrolyte to boost the electrochemical performances of the MnO2//AC Zn-ion hybrid supercapacitors. Theoretically, the formation of double hydrogen bonds between DAAM and H2O can induce the structural transformation of the hydrated Zn2+ ion from [Zn(H2O)6]2+ to [Zn(H2O)5]2+, which can reduce the thickness of the electric double layer to boost the electric double layer capacitance. The theoretical calculation on the Gibbs free energy change can confirm the formation of DAAM/H2O and [Zn(H2O)5]2+ from DAAM and [Zn(H2O)6]2+, indicating the effect of DAAM on the structural transformation of the hydrated Zn2+ ion. The MnO2//AC Zn-ion hybrid supercapacitor with the Zn(CF3SO3)2/DAAM (1 M) electrolyte shows the higher specific capacitances at 0.4 A g−1 and 0.5 A g−1 than the supercapacitor with the Zn(CF3SO3)2 electrolyte, probably due to the effect of DAAM on the structural transformation of the hydrated Zn2+ ion. This supercapacitor can provide the cycling stability of 80.2% (after 10,000 cycles) and the energy density of 35.6 Wh kg−1 (at 0.44 kW kg−1). The wise utilization of DAAM as an electrolyte additive, opens up new avenues for developing high-capacity Zn-foil-free Zn-ion hybrid supercapacitors.

High-performance Zn-ion hybrid supercapacitors enabled by rationally designed hierarchical SiC@C quasi-aligned nanoarrays

In the present work, we report the exploration of rationally designed electrodes based on quasi-aligned nanoarrays composited by the cores of SiC nanowires and shells of sulfur-doped porous carbons (SiC@PC-S), which are directly employed as the free-standing electrodes for Zn-ion hybrid supercapacitors. They behave an ultrahigh areal capacitance of 38.24 mF/cm2 at a scan rate of 10 mV/s, with an exceptional rate capability (~20.67 mF/cm2 even at 1000 mV/s). The as-constructed hybrid supercapacitors deliver a remarkable energy of 10.6 μWh/cm2, which is the highest one among SiC-based supercapacitors ever reported. Moreover, such hybrid devices exhibit a high power density of 7.2 mW/cm2 and a robust cycle stability with ~97 % capacitance retention after 5000 cycles at 2 mA/cm2, representing their promising practical applications.

Cross-linking and self-assembly synthesis of tannin-based carbon frameworks cathode for Zn-ion hybrid supercapacitors

Carbon frameworks with well-developed porosity present broad application prospects in energy-related materials, and green preparation still face challenges. Herein, the tannins-derived framework-like carbon material is obtained by cross-linking and self-assembly strategy.The phenolic hydroxyl and quinones in tannin cross-linking react with the amine groups in the methenamine by simple stirring, which drives the self-assembly of tannins and methenamine,contributing to the reaction products being precipitated in solution as aggregates with framework-like structure. The porosity and micromorphology of framework-like structures are further enriched by the thermal stability difference between tannin and methenamine. The methenamine of framework-like structures is entirely removed by the sublimation and decomposition and the tannin is transformed into carbon materials inheriting framework-like structures after the carbonization, which offers the path for rapid electron transport. The framework-like structure, excellent specific surface area and nitrogen doping give the assembled Zn-ion hybrid supercapacitors a superior specific capacitance of 165.3 mAh·g−1 (350.4 F·g−1). This device could be charged to 1.87 V to power the bulb by using solar panels. This study proves that the tannin-derived framework-like carbon is a promising electrode of the Zn-ion hybrid supercapacitors, which is beneficial for value-added and industrial supercapacitors application of green feedstocks.

Block Copolymer-Directed Facile Synthesis of N-Doped Mesoporous Graphitic Carbon for Reliable, High-Performance Zn Ion Hybrid Supercapacitor.

Ordered mesoporous carbons (OMCs) are promising materials for cathode materials of a Zn ion hybrid capacitor (Zn HC) due to their high surface area and interconnected porous structure. Graphitization of the framework and nitrogen doping have been used to improve the energy storage performance of the OMCs by enhancing electrical conductivity, pseudocapacitive reaction sites, and surface affinity toward aqueous electrolytes. Thus, when both methods are simultaneously implemented to the OMCs, the Zn HC would have improved energy storage performance. Herein, we introduce a facile synthetic method for N-doped mesoporous graphitic carbon (N-mgc) by utilizing polystyrene-block-poly(2-vinlypyridine) copolymer (PS-b-P2VP) as both soft-template and carbon/nitrogen sources. Co-assembly of PS-b-P2VP with Ni precursors for graphitization formed a mesostructured composite, which was converted to N-doped graphitic carbon through catalytic pyrolysis. After selective removal of Ni, N-mgc was prepared. The obtained N-mgc exhibited interconnected mesoporous structure with high nitrogen content and high surface area. When N-mgc was employed as a cathode material in Zn ion HC, excellent energy storage performance was achieved: a high specific capacitance (43 F/g at 0.2 A/g), a high energy density of 19.4 Wh/kg at a power density of 180 W/kg, and reliable cycle stability (>3000 cycles).

A flexible axial Zn ion hybrid supercapacitor with high surface capacitance and long cycle life

Zn-ion hybrid supercapacitors (ZSC) have shown great potential as energy storage devices as they incorporate the merits of rechargeable batteries and supercapacitors. However, the poor bendability, unsatisfied energy density and cycling stability are still challenging the practical application of ZSC. Herein, Zn-doped MnO2 nanowires (Zn-MnO2) binder-free cathodes is synthesized with the aid of a one-step hydrothermal approach, which improves the lattice distortion caused by Zn hydrate ions and provided rich ion transport path. The Zn-MnO2 cathode was assembled with the active carbon (AC) anode into an axial ZSC, achieving a surface capacitance of 1300 mF cm−2 and an energy density of 722.2 μWh cm−2 at power density of 1.99 mW cm−2. After 20,000 charge/discharge cycles, a capacity retention rate of 83.75% and a coulombic efficiency of 100% were achieved, indicating excellent cycle stability of present device. In addition, this axial ZSC reveals exquisite mechanical flexibility and electrochemical stability, enabling continuously power smartphones under bending conditions. Present work suggests that ZSC devices based on Zn-MnO2 have excellent doable for business energy storage devices.

Layered and honeycomb N-doped porous carbon for advanced Zn-ion hybrid supercapacitors and Li-ion batteries

Recently, Zn-ion hybrid supercapacitors (ZIHCs) have been widely investigated. Therefore, it is very important for the commercial development of ZIHCs to find high-capacity and stable cathodes. Herein, the layered and honeycomb porous carbon by a straight forward and scalable one-step simple KHCO3-activated method has been synthesized triumphantly. The obtained samples have large surface area, well-developed porosity. Meanwhile, the conductive network and abundant electrode active sites make them have great potential and advantages as electrodes for ZIHCs. After optimization, the honeycomb porous carbon-based ZIHCs demonstrated superior electrochemical performances (0.5 A g−1, 131 mAh g−1), excellent rate and cycling performance. Moreover, it demonstrated high energy density (104.6 Wh kg−1) and power density (12.0 kW kg−1). It can also effectively power the red light-emitting diodes (LEDs), showing the practical application of the porous carbon based ZIHCs. What is more important, the synthesized porous carbon revealed remarkable capacity for lithium-ion batteries (LIBs) (0.2 A g−1, 780 mAh g−1). Even at high current density of 5 A g−1, it still maintains an impressive capacity of 533 mAh g−1 after 1500 cycles. Based on our results, the honeycomb porous carbon could be potential electrodes for ZIHCs and LIBs.