Zn-ion Hybrid Supercapacitors Research Articles

Highly flexible Zn-ion hybrid supercapacitors based on carbon fibers covalently combined with polypyrrole

Highly flexible Zn-ion hybrid supercapacitors based on carbon fibers covalently combined with polypyrrole

H2O/Ni2+ intercalated lamellar vanadium oxide as cathode materials for aqueous zn-ion hybrid supercapacitors

The low power density of batteries and the low energy density of conventional supercapacitors necessitate the development of new energy storage systems. While aqueous Zn-ion hybrid supercapacitor (ZHS) has received extensive attention as an attractive candidate for energy storage devices, its slow ion diffusion dynamics and unsatisfied cycling stability are remained to be addressed. Herein, lamellar structured NixV2O5·nH2O (NVO) with in-situ H2O/Ni2+ intercalation was synthesized and used as cathode materials to assemble Zn-ion asymmetric supercapacitor with the activated carbon as anode. Benefiting from the enlarged the lamellar spacing induced by ion intercalation, the ion diffusion ability was greatly improved and thus the energy storage performance was improved. A specific capacity of 52 mAh g−1 at the current density of 0.1 A g−1 and a power density of 51.6 W kg−1 at energy density of 27.2 Wh kg−1 were achieved. The supercapacitor displayed excellent cycle performance without obvious decay after 5000 cycles. Present work provided experimental support for commercial application of vanadium-based Zn-ion hybrid supercapacitors.

Ice template-assisting activation strategy to prepare biomass-derived porous carbon cages for high-performance Zn-ion hybrid supercapacitors

Biomass-derived porous carbons are desirable electrode material for supercapacitors, but the blocked carbon morphology leading to the poor accessibility and long diffusion distance hinders the practical application. Exposing the inner carbon space for smooth ion transport is crucial for the enhanced capacitive performance. Herein, porous carbon cages were prepared from heavy bio-oil using an ice template-assisting activation method. Ice crystals played crucial roles in the fabrication of cage-like morphology. By tuning the volume, ice crystals grew as templates to create cavities, prevent the shrinkage of carbon framework and transport activators into carbon bulks for high accessible surface area. The resultant porous carbons possess open structure with hollow cavities and layered shells, allowing the both excellent energy and power performance for symmetric supercapacitors and Zn-based hybrid supercapacitors. The assembled Zn-based hybrid supercapacitors achieve a favorable energy density of 119.02 Wh kg−1.

Highly stable and low-temperature-tolerant zinc ion storage enabled by carbitol electrolyte additive engineering

Aqueous zinc (Zn)-ion energy storage system is widely regarded as a promising candidate for future electrochemical energy storage applications but suffers insufficient lifespan and limited operating temperature. To address these issues, we introduce a carbitol additive for a novel hybrid electrolyte to enhance cycling stability and temperature adaptability by optimizing the coordination structure of Zn ion. The modified electrolyte not only restrains the hydrogen evolution, but also promotes a high-orientation Zn deposition and significantly limits the Zn dendrite growth. Taking advantage of improved electrolyte properties, the Zn symmetric cells with 10 % carbitol-modified electrolyte exhibit long-term cycle stability for 5000 h at 25 °C, and 400 h at −10 °C. More notably, the carbitol-modified electrolyte endows a stable reversible capacitance for Zn ion hybrid supercapacitors to be operated at different temperatures. Our work affords a reasonable electrolyte engineering strategy to fabricate a highly stable and low-temperature-tolerant Zn ion storage system.

Freeze-tolerant gel electrolyte membrane for flexible Zn-ion hybrid supercapacitor

At low temperatures, the working capability of Zn-ion energy storage devices at low temperatures is becoming a huge challenge in the field of electrochemical energy storage. This is primarily due to the slow kinetic process of ions along with the failure of hydrogel electrolytes under subzero temperatures. Herein, a flexible anti-freezing Zn-ion hybrid supercapacitor is developed with the use of freeze-tolerant polyacrylamide‑sodium alginate (PAM-SA) gel electrolyte membrane combined with graphene cathode and Zn foil anode. The freeze-tolerant PAM-SA gel electrolyte membrane is synthesized by a simple solvent displacement process and it shows an excellent ionic conductivity of ∼15.29 mS cm−1 at room-temperature (RT) with an anti-freezing ability of 4.17 mS cm−1 at −25 °C. Also, the prepared electrolyte membrane demonstrates an outstanding long-term stability over 900 h without the formation of Zn dendrites. The anti-freezing Zn-ion hybrid supercapacitor displays a sound electrochemical performance with an excellent capacity of 210.6 F g−1 in conjunction with the capacitance retention of 65 % even after charge-discharge cycling for 40,000 times at RT. Also, the device possesses an excellent anti-freezing performance. It can still deliver a capacity of 79.60 F g−1 and the capacitance retention of 80 % after cycling for 15,000 times even at a low temperature of −25 °C. These results indicate that the present work may offer a feasible way of constructing Zn-ion energy storage devices applicable in a subzero temperature environment.

Bioinspired design of graphene-based N/O self-doped nanoporous carbon from carp scales for advanced Zn-ion hybrid supercapacitors

Integrating the superiorities of high power density of supercapacitors and high energy density of batteries, safe and low cost aqueous Zn-ion hybrid supercapacitors (ZIHSCs) are regarded as a promising alternative for next generation energy storage devices. As potential cathode materials for ZIHSCs, porous carbon/graphene have been widely investigated recently, whereas the adjustment of their composition and structure to achieve favorable features of sustainability, long lifespan and high activity remains a challenge. Herein, a graphene-based N/O co-doped porous carbon is successfully constructed via an efficient approach of the carbonization and sequent KOH activation using renewable carp scales as carbon source. The unique lamellar structure with the exterior layer of hydroxyapatite and the beneath well-arranged collagen fibrils (rich in N and O) functions as catalytic base for the growth of graphene structure over the exterior layer and affords the self-doping with N and O heteroatoms, respectively. Expectedly, the resultant carbon possesses a hybrid structure of graphene base and nanoporous amorphous carbon, together with a proper N/O co-doping, resulting in fast electrochemical kinetics and abundant Zn2+ storage active sites for high power and energy outputs. Consequently, as-assembled aqueous ZIHSC displays a high specific capacity of 138.8 mAh g − 1 at 0.1 A g − 1, admirable rate capability of 61.7% retention rate at a 200-fold higher current, and attractive energy density of 111.1 Wh kg−1 at 100 W kg−1. More excitingly, as-constructed quasi-solid ZIHSC exhibits a satisfactory specific capacity of 117.8 mAh g − 1, a high energy density of 88.9 Wh kg−1 and a high power density of 10 kW kg−1, together with excellent cycling stability (capacity retention of 87.2% after 10,000 charge-discharge cycles at 5 A g − 1) and outstanding mechanical flexibility. Therefore, the designed conversion of carp scales to advanced carbons by taking advantages of its inherent composition and structure opens up hereditary view to construct high performance ZIHSCs from biomass sources.

Rice husk-derived carbon materials for aqueous Zn-ion hybrid supercapacitors

High-performance rice husk-derived carbonaceous electrode materials for aqueous zinc-ion hybrid supercapacitors (ZHSCs) were prepared via a simplistically one-step molten salt carbonization process in molten eutectic Na2CO3-K2CO3 at 750, 850 and 950 °C. ZHSC assembled by Zn foil as an anode and carbon material prepared at 850 °C as a cathode delivers 149.8, 120.1, 108.7, 100.3, 89.3, 80.7 and 69.8F g−1 from 0.2 to 20 A g−1 in 3 mol L−1 Zn(CF3SO3)2 aqueous solution with a rate performance of 47 % capacitance retention. It exhibited energy (power) density with 58.6 Wh kg−1 (167.8 W kg−1) at 0.2 A g−1 and power (energy) density with 10.0 kW kg−1 (9.7 Wh kg−1) at 20 A g−1 as well as excellent cyclic stability with 95.8 % capacitance retention and coulombic efficiency of 99.9 % after 3005 charge-discharge cycles at 2 A g−1. The relationship between structure and electrochemical energy storage performance is also discussed with performance depending on the synergistic effect of porous structure, specific surface area, electrical conductivity and heteroatom doping of rice husk-derived carbon materials.

Molecular engineering toward sustainable development of multiple-doped hierarchical porous carbons for superior zinc ion storage

Aqueous Zn-ion hybrid supercapacitors (ZHSCs) hold great potential as next-generation energy storage devices due to their low cost, excellent rate capability, long cycling life, and high safety. Heteroatom-doped hierarchical porous carbons (HD-HPCs) with integrated high specific surface area, multiscale pores, and abundant defects have been regarded as promising cathode materials for ZHSCs. However, the in situ architecture of HD-HPCs with these multiple advantages via a sustainable and controllable method remains an arduous challenge. Herein, a novel molecular engineering strategy was proposed for the in situ construction of N/P/O-doped HD-HPCs via the direct carbonization of multiple-heteroatom-rich hypermolecules. Such a strategy has multiple advantages, including the exclusion of pore-making techniques, activation agents, templates, and complicated and hazard washing processes, demonstrating its green and sustainable properties. The highly active multiple-heteroatom-rich hypermolecular precursors contributed to the formation of abundant micro/mesopores due to the self-abscission of heteroatoms and heteroatom-contiguous carbon atoms at high carbonization temperatures. Consequently, these active structural/compositional features endowed the optimal cathodes with outstanding storage capacities of 139.2 and 88.9 mA h g−1 at 0.5 and 20 A g−1 for aqueous ZHSCs, respectively. They also delivered a superior storage performance in quasi-solid ZHSCs (QS-ZHSCs) with a high specific capacity of 111.5 mA h g−1 at 0.5 A g−1. Superior energy/power densities and long cycling stability were also achieved for aqueous and QS-ZHSCs. The theoretical calculation confirmed the synergetic effects of multiple-atom doping on enhancing the electronic conductivity and reducing the energy barrier between Zn ions and carbon, which promote the Zn-ion adsorption capability. These findings shed fresh light on the straightforward manufacture of superior HD-HPCs for electrochemical energy storage.

A Silk Protein-Based Eutectogel as a Freeze-Resistant and Flexible Electrolyte for Zn-Ion Hybrid Supercapacitors.

A eutectogel (ETG) based on immobilizing a zinc salt deep eutectic solvent (DES) in a silk protein backbone is prepared by a coagulating bath method as a solid electrolyte for Zn-ion hybrid supercapacitors (ZHSCs). The Zn salt DES is composed by ethylene glycol (EG), urea, choline chloride (ChCl), and zinc chloride (ZnCl2) with a molar ratio of 6:10:3:3. A strong bonding of the DES liquid to the silk protein backbone is formed between protein macromolecules and the DES due to plenty of hydrogen bonds in both materials. The as-prepared ETG membrane is dense and has no obvious void defects, which possesses a fracture strength of 7.58 MPa and environmental stability. As a solid electrolyte, the ETG membrane exhibits a higher Zn2+ transference number of about 0.60 and a high ionic conductivity (12.31 mS cm-1 at room temperature and 3.63 mS cm-1 at -20 °C). A ZHSC (Zn∥ETG∥C) with the silk protein-based ETG electrolyte is assembled by Zn and active carbon as the anode and the cathode, respectively, which delivers a specific capacitance of 342.8 F g-1 at a current density of 0.2 A g-1 and maintains excellent cycling stability with 80% capacitance retention after 20,000 cycles at a high current rate (5 A g-1) at room temperature. Moreover, the Zn∥ETG∥C device can safely work under a lower temperature of about -18 °C and damaging situations, such as folding states and even cutting tests. The interface evolutions between the Zn anode and the ETG electrolyte are explored, and it was found that a ZnCO3/Zn(CH2OCO2)2 solid electrolyte interphase is in situ formed on the Zn anode, which can inhibit the growth of Zn dendrites. This work provides a new way to fabricate advanced electrolytes for applications in Zn-ion hybrid supercapacitors.

High-capacitance MXene anode based on Zn-ion pre-intercalation strategy for degradable micro Zn-ion hybrid supercapacitors

Degradable energy storage systems (ESSs) have been proposed to tackle increasing electronic waste such as heavy metals and toxic organic electrolytes. However, ensuring ESS degradability and cycle life at the same time is a paradox challenge. Here we reported a degradable micro Zn-ion hybrid supercapacitor (DMZHSC) based on MXene/ZnCl2 anode and MnO2-MWCNTs cathode. Considering the problem of the lower capacitance of MXene, the ZnCl2 modification strategy of pre-intercalating Zn2+ into the layer of MXene was used by osmotic pressure, opening more active sites for the subsequent Zn2+ intercalation. During this process, Cl- will replace part of the -F terminals on the surface of MXene. Benefited from above modification, the MXene/ZnCl2 anode shown a very high capacitance up to 529.1 F g−1 at 1.00 mV s−1, which is 32.2% higher than pure MXene (400.3 F g−1 at 1.00 mV s−1). More importantly, the assembled DMZHSCs not only possesses excellent flexibility but also can degrades within 2.0 h after mild external stimulation in PBS buffer. This work not only provides a new method for MXene modification but also provides a new idea for the construction of environmentally friendly new capacitors.

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 Cux -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 Cux -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.

Flexible Zn-ion hybrid supercapacitor enabled by N-Doped MnO2 cathode with high energy density and ultra-long cycle life

To meet the higher requirements for green energy, high-performance renewable energy technology based on earth‑abundant materials is essential. Aqueous zinc-ion hybrid supercapacitors (ZSC) have been regarded as an attractive candidate for sustainable electrochemical energy storage device combining the advantages of batteries and supercapacitors, but their unsatisfactory cycling stability and low energy density remain a problem to be solved. Herein, nitrogen-doped MnO2 (N-MnO2) nanowalls were synthesized by in situ deposition, which provides rich ion transport pathway and accelerates the extraction/insertion of zinc ions. As a result, N-MnO2 anode can be assembled to an aqueous zinc-ion hybrid capacitor with AC cathodes, presenting a high energy density of 712.5 μWh cm−2 at a power density of 1000 μW cm−2 (1 mA cm−2) and excellent cycle stability with a capacity retention rate of 92.9 % in 25,000 charge-discharge cycles. In addition, the flexible hybrid supercapacitor exhibits excellent mechanical flexibility, and the electrochemical performance remains stable under different bending angles. This work shows that ZSC device based on N-MnO2 nanowalls hold great potential for new energy storage devices.

Eutectic salt induced self-activation technique for porous graphene-like carbon nanosheets as the high-capacity cathodes for Zn-ion hybrid supercapacitors

• Graphene-like carbon nanosheets were obtained in different eutectic salts. • In-situ formed Na 2 CO 3 can serve as a chemical activation agent. • The roles of eutectic salt have been revealed. • The carbon has a surface area of 1739.5 m 2 /g with hierarchical pores. • The carbon nanosheets achieved high specific capacity of 169.1 mAh g −1 . The exploration of a non-corrosive and sustainable strategy to produce thin graphene-like porous carbon nanosheets with large specific surface area for electrochemical energy storage applications is highly desired yet a huge challenge. Herein, we report a eutectic salt induced self-activation process for the synthesis of a serials of porous carbon nanosheets with well-controlled microstructures just by simply changing the type of eutectic salt. The experiment results illustrated that the in-situ formed Na 2 CO 3 , which is usually “inert” when serves as a chemical activation reagent at relatively low temperature, display a significant enhanced chemical activation in eutectic salt medium. Specifically, thin graphene-like porous carbon nanosheets with a large specific surface of 1739.5 m 2 /g can be obtained in CsCl-NaCl eutectic salt. When acts as a cathode for Zn-ion hybrid supercapacitors (ZSCs), a high specific capacity of 169.1 mAh/g (at 0.1 A/g), large specific energy of 62.24 W h kg −1 (at an ultrahigh specific power of 16 kW g −1 ) and cyclic stability of 91.7 % after 10,000 cycles. In addition, a quasi-solid-state ZSC device, which can freely realize series to increase the working voltage, demonstrated its hold a potential for practical application. This strategy combines the advantages of the in-situ chemical activation with the advantages of the eutectic salt medium, which offers an alternative way for the producing of various functional nanocarbons for a variety of applications including electrochemical energy storage.

Achieving fast Zn-ion storage kinetics by confining nitrogen-enriched carbon nanofragments in a honeycomb-like matrix

Contriving ingenious and stable carbon structures is critical but of great challenge to improve the electrochemical kinetics in Zn-ion storage devices. In this study, nitrogen-enriched carbon nanofragments confined in a three-dimensional honeycomb-like hierarchical porous matrix are designed and constructed with a simple in situ confined thermal polymerization and carbonization strategy. By employing the as-prepared hierarchical carbon nanostructures for an advanced Zn-ion hybrid supercapacitor, a record high-rate capability has been obtained, manifested as a high specific capacity of 101.3 mAh g−1 at an extraordinary fast discharge rate of 100 A g−1. Additionally, a maximum energy density of 130.2 Wh kg−1 at a power density of 185 W kg−1, and a peerless power density of 92500 W kg−1 at the corresponding energy density of 93.7 Wh kg−1 are achieved, demonstrating the feasibility for high-power Zn-ion storage devices. Further kinetics and mechanism studies reveal that the fast Zn2+ storage kinetics originates from the N-enriched chemistry and the multiscale pore network which provide a hydrophilic surface, boost charge transfer, and expedite the ion diffusion.

Flexible thermotolerant Zn-ion hybrid supercapacitors enabled by heat-resistant polymer electrolyte

Hydrogel electrolytes often fail at high temperatures and thus common Zn-ion energy storage devices are rarely employed under high temperature conditions. Herein, a flexible heat-resistant nonflammable polymer electrolyte membrane has been prepared and employed in the fabrication of Zn-ion energy storage devices. The optimum electrolyte membrane exhibits a high room-temperature ionic-conductivity (∼1.52 × 10-3 S cm−1) along with a wide window of electrochemical stability (∼2.5 V). The membrane also shows a high tensile strength (4.3 MPa) and good flame-retardant performance. Moreover, it can effectively restrain the parasitic hydrogen evolution reaction as well as the Zn-dendrite formation. The Zn-ion hybrid supercapacitor (Zn-HS) fabricated with the membrane demonstrates good flexibility and thermotolerant performance. At a current density of 1 A/g, the device possesses a specific capacitance of 162.6 F/g at room temperature, 362.6 F/g at 80 °C, and 404.2 F/g at 100 °C. It also exhibits a long-term cycling capability (up to 30,000 cycles) even at 80 °C. Conclusively, the present work offers a promising way in designing heat-resistant nonflammable polymer electrolytes for flexible energy storage devices suitable for high-temperature applications.

High-performance Zn-ion hybrid supercapacitor enabled by the hierarchical N/S co-doped graphene/polyaniline cathode

Zinc ion hybrid supercapacitors (Zn-HSCs), combined with the superiorities of supercapacitors and batteries, are regarded to have evolutive potential in devices of energy storage. Herein, the nitrogen and sulfur co-doped graphene/polyaniline nanoarrays (NSG/PANI) have been successfully compounded by in-situ polymerization. The structural characterization shows that the NSG/PANI-50 nanocomposite possess more active sites and vertically arranged PANI nanoarrays on the surface of NSG. The Zn-HSCs devices assembled by the zinc foil as anode, NSG/PANI-x (x = 30, 50, 70) as cathode and ZnSO4 as electrolyte (NSG/PANI//ZnSO4 (aq.)//Zn) show extraordinary energy storage properties. The prepared NSG/PANI-50//Zn device exhibits exceptional specific capacitance of 268.4 F g−1 at 0.1 A g−1 (the retention rate is 75.2% as the current density increased 20-times from 0.1 A g−1 to 2 A g−1), high energy density (95.4 Wh kg−1) and excellent capacitance retention rate of ~ 93% at 5 A g−1 after 10,000 cycles. The diffusion-controlled behavior (72% of the total storage charge at 5 mV s−1) suggests that the diffusion-controlled process acts a momentous role in the process of energy storage. The impressive results demonstrate that NSG/PANI nanocomposite could be a potential high-performance electrode material for Zn-ion hybrid energy systems.

Graphite–graphene architecture for Zn-ion hybrid supercapacitor electrodes

Graphite–graphene architecture for Zn-ion hybrid supercapacitor electrodes

A multifunctional potassium peroxodisulfate activation strategy to construction of N, S co-doped carbon nanosheets for high-performance Zn-ion hybrid supercapacitors

A multifunctional potassium peroxodisulfate activation strategy to construction of N, S co-doped carbon nanosheets for high-performance Zn-ion hybrid supercapacitors

Unveiling the cooperative roles of pyrrolic-N and carboxyl groups in biomass-derived hierarchical porous carbon nanosheets for high energy-power Zn-ion hybrid supercapacitors

The low energy density of Zn-ion hybrid supercapacitors (ZHSCs) remains to be one of the key challenges against its commercialization due to the lack of cathode materials with high capacity, particularly at high current density. Herein, biomass-derived hierarchical porous carbon nanosheets functionalized with oxygen groups and nitrogen dopants used as the cathode for ZHSCs are synthesized via a consecutive two-step pyrolysis-activation strategy, which manifest a high capacity of 220.1 mAh g−1 at 0.2 A g−1, and maintain 118.2 mAh g−1 when the current density increases 100 times to 20 A g−1. Benefitting from the promising performance of the as-obtained cathode materials, the ZHSC finally demonstrates an ultra-high energy density of 181.6 Wh kg−1 at the power density of 165.0 W kg−1, which surpasses the vast majority of state-of-the-art reported ZHSCs. Accordingly, the experimental results and theoretical calculations reveal that the hierarchically porous ultrathin nanosheet architecture with macro-, meso- and micropores is favorable for boosting the physical adsorption of Zn2+, while the introduction of surface pyrrolic-N and carboxyl (–COOH) groups synergistically boosts the chemical adsorption of Zn2+. The present work provides insights into the synergistic effect of nitrogen doping and oxygen functional groups modification hierarchical porous carbon for Zn-ion storage.

MXene-based Zn-ion hybrid supercapacitors: Effects of anion carriers and MXene surface coatings on the capacities and life span

Energy storage devices such as rechargeable batteries and supercapacitors are of great importance for establishing clean energy sources. Accordingly, the production of these devices needs to rely on sustainable and environmentally friendly materials. This report provides an insight on the use of two-dimensional transition metal carbides (MXene) based electrodes, here shown for Mo1.33CTz-Ti3C2Tz mixed MXene, in Zn-ion hybrid supercapacitors (ZHSC) using aqueous and nonaqueous (acetonitrile-based) electrolytes. The effect of anion carriers on the accessible capacity, rate capability, and life span of the MXene//Zn hybrid supercapacitor is explored in-depth. Halide carriers such as chloride (Cl−) and iodide (I−) feature a superior performance, however, a fast passivation is observed in Cl− based electrolytes and a narrow potential window is achieved in I− based electrolytes. Importantly, a few micron layer of Ti3C2Tz MXene coated on the surface of the Zn anode is found to inhibit the side reactions and passivation observed in ZnCl2 solutions, which enables the use of such low-cost Zn salt in MXene//Ti3C2Tz-coated-Zn cells. The cells can be reversibly cycled over 10,000 cycles, delivering a capacity up to 200 mAh g−1 at low rate (0.5 mV s−1) and a capacity retention of about 36% at high rate (100 mV s−1). Furthermore, the Ti3C2Tz surface coating layer enhanced the coulombic efficiency in Zn(CF3SO3)2 electrolyte without affecting the accessible capacity or the rate capability. This work sheds light on the use of MXenes in sustainable low-cost ZHSC with high energy density and power density as a positive electrode material as well as a surface coating material for the Zn negative electrode.