Biomass-derived mesoporous carbons materials coated by α-Mn3O4 with ultrafast zinc-ion diffusion ability as cathode for aqueous zinc ion batteries

Enabling Long-cycling Aqueous Zn-Mn3O4 Batteries via Segregated and Interlaced Carbon Frameworks

Mn3O4 is a promising candidate for aqueous zinc ion batteries (ZIBs) due to its high theoretical capacity (468.5 mAh g-1) and environmental friendliness, while its practical application is hindered by slow kinetics and rapid capacity degradation. Herein, a porous Mn3O4 with segregated and interlaced carbon framework (HCF-Mn3O4) is introduced. The in situ hydro-assembled interlaced carbon nanotube (CNT) forms a porous structure enhancing electron conduction and accelerating Zn2+ transport; while the segregated CNT network serves as an encapsulation layer to improve mechanical stability. Together, these features facilitate the simultaneous insertion and transformation of H+/Zn2+ and enhance Zn2+ diffusion kinetics. As a result, HCF-Mn3O4 achieves a high specific capacity of 474 mAh g-1 at 0.05 A g-1, excellent rate performance of 178 mAh g-1 at 1.50 A g-1, and stable cycling over 3000 cycles with minimal capacity decay (≈0.02% per cycle). This design offers new opportunities for developing high-rate, long-lasting ZIBs.

In-situ growth of co-intercalated MnO2 on 3D lignin-based carbon nanoflowers endows high-performance aqueous zinc-ion batteries cathode

The electrochemical kinetics, conductivity, and lifespan of MnO2 are significant challenges that impede its commercialization as a cathode material for aqueous zinc-ion batteries (AZIBs). In this study, carbon nanoflowers (NFCs) were prepared from lignin as a carbon source, and the dissolution behaviour of MnO2 during cycling was inhibited by uniformly loading nanoflower-like δ-MnO2 (MnO2@NFC) on NFCs in situ. Additionally, Co-intercalated δ-MnO2/lignin-based carbon nanoflowers (Co-MnO2@NFC) were prepared and used as the cathode for rechargeable AZIBs. The initial discharge capacity of the AZIBs using Co-MnO2@NFC as the cathode material is as high as 340 mAh·g-1 at a specific current density of 0.1 A·g-1, and the capacity retention rate reaches 88.1 % after 1000 cycles at 1.0 A·g-1. Co-MnO2@NFC exhibits excellent conductivity compared to δ-MnO2 and MnO2@NFC. Through electrochemical analysis and ex-situ characterization, the energy storage mechanism of Co-MnO2@NFC is identified as H+/Zn2+ co-insertion/extraction. This work enhances the stability of MnO2 by loading it onto NFC carriers. It improves the specific capacity of the material by intercalating Co ion, providing a new approach for the controllable design of cathodes for AZIBs.

Cutting-Edge Progress in Aqueous Zn-S Batteries: Innovations in Cathodes, Electrolytes, and Mediators

Rechargeable aqueous zinc-sulfur batteries (AZSBs) are emerging as prominent candidates for next-generation energy storage devices owing to their affordability, non-toxicity, environmental friendliness, non-flammability, and use of earth-abundant electrodes and aqueous electrolytes. However, AZSBs currently face challenges in achieving satisfied electrochemical performance due to slow kinetic reactions and limited stability. Therefore, further research and improvement efforts are crucial for advancing AZSBs technology. In this comprehensive review, it is delved into the primary mechanisms governing AZSBs, assess recent advancements in the field, and analyse pivotal modifications made to electrodes and electrolytes to enhance AZSBs performance. This includes the development of novel host materials for sulfur (S) cathodes, which are capable of supporting higher S loading capacities and the refinement of electrolyte compositions to improve ionic conductivity and stability. Moreover, the potential applications of AZSBs across various energy platforms and evaluate their market viability based on recent scholarly contributions is explored. By doing so, this review provides a visionary outlook on future research directions for AZSBs, driving continuous advancements in stable AZSBs technology and deepening the understanding of their charge-discharge dynamics. The insights presented in this review signify a significant step toward a sustainable energy future powered by renewable sources.

Nanoengineered RF-Sputtered Mn3O4 Cathode Thin Films for Aqueous Zinc-Ion Batteries: Insights into Diffusion Dynamics and Application Potential

Manganese oxides are a promising cathode material for aqueous zinc-ion batteries (AZIBs), but thin-film configurations remain underexplored. This study investigates the electrochemical dynamics of 60 nm thin Mn3O4 thin films, fabricated via RF magnetron reactive sputtering. It addresses the highest reported capacity (25 mAh/g) in thin film form, stability over 500 cycles, effective performance across varying current rates, surpassing previous studies and challenges such as phase stability, and capacity fading over extended cycling, aiming to enhance uniformity, minimizing diffusion barriers for improved performance. EIS reveals Zn2+ diffusion coefficients of 1.503 × 10-7, 1.336 × 10-16, and 1.947 × 10-20 cm2/s in precycle, charged, and discharged states, respectively, highlighting evolving diffusion dynamics during cycling. Structural instability during discharge leads to a decline in diffusion performance, emphasizing the need for material and interfacial optimizations to enhance stability and mitigate degradation. These findings underscore the critical role of interfacial engineering and structural stability in maintaining high ion diffusion rates and minimizing morphological degradation during cycling. The present study explores the critical role of targeted engineering in unlocking their full potential for lightweight, miniaturized, high-performance microbatteries for energy storage applications.

Regulating the zinc ion transport kinetics of Mn3O4 through copper doping towards high-capacity aqueous Zn-ion battery

High working voltage, large theoretical capacity and cheapness render Mn3O4 promising cathode candidate for aqueous zinc ion batteries (AZIBs). Unfortunately, poor electrochemical activity and bad structural stability lead to low capacity and unsatisfactory cycling performance. Herein, Mn3O4 material was fabricated through a facile precipitation reaction and divalent copper ions were introduced into the crystal framework, and ultra-small Cu-doped Mn3O4 nanocrystalline cathode materials with mixed valence states of Mn2+, Mn3+ and Mn4+ were obtained via post-calcination. The presence of Cu acts as structural stabilizer by partial substitution of Mn, as well as enhance the conductivity and reactivity of Mn3O4. Significantly, based on electrochemical investigations and ex-situ XPS characterization, a synergistic effect between copper and manganese was revealed in the Cu-doped Mn3O4, in which divalent Cu2+ can catalyze the transformation of Mn3+ and Mn4+ to divalent Mn2+, accompanied by the translation of Cu2+ to Cu0 and Cu+. Benefitting from the above advantages, the Mn3O4 cathode doped with moderate copper (abbreviated as CMO-2) delivers large discharge capacity of 352.9 mAh g-1 at 100 mA g-1, which is significantly better than Mn3O4 (only 247.8 mAh g-1). In addition, CMO-2 holds 203.3 mAh g-1 discharge capacity after 1000 cycles at 1 A g-1 with 98.6 % retention, and after 1000 cycles at 5 A g-1, it still performs decent discharge capacity of 104.2 mAh g-1. This work provides new ideas and approaches for constructing manganese-based AZIBs with long lifespan and high capacity.

Dual cross-linked cellulose-based hydrogel for dendrites-inhibited flexible zinc-ion energy storage devices with ultra-long cycles and high energy density

Hydrogel electrolytes, renowned for their mechanical robustness and versatility, are crucial in ensuring stable energy output in flexible energy storage devices. This work presents a dual cross-linked cellulose-based hydrogel electrolyte with chemical cross-linking from covalent bonding and physical cross-linking from hydrogen bonding. This electrolyte demonstrated outstanding mechanical strength and porous structure with abundant hydroxyl groups, which facilitates the migration of Zn2+ and suppresses the formation of undesirable zinc dendrite, thereby enhancing the ion conductivity (18.46 ± 0.39 mS cm-1 at room temperature) and extending electrochemical stability window (0-2.23 V). Zn||Zn symmetric cells based on this electrolyte demonstrated stable stripping/plating cycles of 3000 h at a current density of 1 mA cm-2. Furthermore, the corresponding flexible zinc-ion hybrid capacitor retains a 90.3 % capacity over 100,000 cycles at 10 A g-1, while remaining functional across various folding angles. Hence, this biomass-derived hydrogel electrolyte holds promise for flexible energy storage device applications.

In situ growth of Mn3O4 nanoparticles on accordion-like Ti3C2Tx MXene for advanced aqueous Zn-Ion batteries

Manganese-based cathodes are competitive candidates for state-of-the-art aqueous zinc-ion batteries (AZIBs) because of their easy preparation method, sufficient nature reserve, and environmental friendliness. However, their poor cycle stability and low rate performance have prevented them from practical applications. In this study, Mn3O4 nanoparticles were formed in situ on the surface and between the interlayers of Ti3C2Tx MXene, which was pretreated by the intercalation of K+ ions. Ti3C2Tx MXene not only provides abundant active sites and high conductivity but also hinders the structural damage of Mn3O4 during charging and discharging. Benefiting from the well-designed K-Ti3C2@Mn3O4 structure, the battery equipped with the K-Ti3C2@Mn3O4 cathode achieved a maximum specific capacity of 312 mAh/g at a current density of 0.3 A/g and carried a specific capacity of approximately 120 mAh/g at a current density of 1 A/g, which remained stable for approximately 500 cycles. The performance surpasses that of most reported Mn3O4-based cathodes. This study pioneers a new approach for building better cathode materials for AZIBs.

Deciphering the storage mechanism of biochar anchored with different morphology Mn3O4 as advanced anode material for lithium-ion batteries

Biochar is regarded as a promising lithium-ion batteries anode material, owing to its high cost-effectiveness. However, the poor specific capacity and cycling stability have limited its practical applications. A straightforward and cost-efficient solvothermal method is presented for synthesizing Mn3O4/biochar composites in this study. By adjusting solvothermal temperatures, Mn3O4 with different morphology is prepared and anchored on the biochar surface (MKAC-T) to improve the electrochemical performance. Due to the morphological effect of nanospherical Mn3O4 on the biochar surface, the MKAC-180 anode material demonstrates outstanding reversible capacity (992.5 mAh/g at 0.2 A/g), significant initial coulombic efficiency (61.1 %), stable cycling life (605.3 mAh/g at 1.0 A/g after 1000 cycles), and excellent rate performance (385.8 mAh/g at 1.6 A/g). Moreover, electro-kinetic analysis and ex-situ physicochemical characterizations are employed to illustrate the charge storage mechanisms of MKAC-180 anode. This study provides valuable insights into the "structure-activity relationship" between Mn3O4 microstructure and electrochemical performance for the Mn3O4/biochar composites, illuminating the industrial utilization of biomass carbon anode materials.

Carbonized Ganoderma Lucidum/V2O3 Composites as a Superior Cathode for High-Performance Aqueous Zinc-Ion Batteries

In response to the suboptimal electrochemical performance of low-valence vanadium oxides, Ganoderma lucidum biomass-derived carbon@V2O3 (V2O3@CGL) composites were prepared by evaporative self-assembly technology and high-temperature calcination. In the prepared composites, V2O3 effectively encapsulates CGL, serving as a support for V2O3 and enhancing electrical conductivity and structural stability. This results in improved overall performance for the composites. They revealed satisfactory electrochemical properties when assembled in aqueous zinc-ion batteries (AZIBs). The preliminary discharge specific capacity of the V2O3@CGL-2 (VOCG-2) composite electrode reached 407.87 mAh g-1 at 0.05 A g-1. After 1000 cycles, the capacity retention is 93.69% at 3 A g-1. This research underscores the feasibility of employing V2O3 and abundantly available biomass for high-performance AZIB cathodes.

Enhanced Ion Transport Through Mesopores Engineered with Additional Adsorption of Layered Double Hydroxides Array in Alkaline Flow Batteries

Efficient mass transfer in electrodes is essential for the electrochemical processes of battery charge and discharge, especially at high rates and capacities. This study introduces a 3D electrode design featuring layered double hydroxides (LDHs) nanosheets array grown in situ on a carbon felt surface for flow batteries. The mesoporous structure and surface characteristic of LDH nanosheets, especially, the hydroxyl groups forming a unique "H-bonding-like" geometry with ferrous cyanide ions, facilitate efficient adsorption and ion transport. Thus, the designed LDHs electrode enables the alkaline zinc-iron flow battery to maintain a voltage efficiency of 81.6% at an ultra-high current density of 320 mA cm-2, surpassing the values reported in previous studies. The energy efficiency remains above 84% after 375 cycles at a current density of 240 mA cm-2. Molecular dynamics simulations verify the enhanced adsorption effect of LDH materials on active ions, thus facilitating ion transport in the battery. This study provides a novel approach to improve mass transport in electrodes for alkaline flow batteries and other energy storage devices.

Porous layered ZnV2O4@C synthesized based on a bimetallic MOF as a stable cathode material for aqueous zinc ion batteries

Vanadium-based oxides are considered potential cathode materials for aqueous zinc ion batteries (AZIBs) due to their distinctive layered (or tunnel) structure suitable for zinc ion storage. However, the structural instability and sluggish kinetics of vanadium-based oxides have limited their capacity and cycling stability for large-scale applications. To overcome these shortcomings, here a porous vanadium-based oxide doped with zinc ions and carbon with the molecular formula ZnV2O4@C (ZVO@C) as the cathode material is synthesized by the pyrolysis of a bimetallic MOF precursor containing Zn/V. This electrode demonstrates a remarkable specific capacity of 425 mA h g-1 at 0.5 A g-1 and excellent cycling stability with about 97% capacity retention after 1000 cycles at 10 A g-1. The excellent electrochemical performance of ZVO@C can be attributed to more reaction active sites and the faster reaction kinetics for zinc ion diffusion and storage brought about by the porous layered spinel-type tunnel structure with high surface area and massive mesoporosity, as well as the enhanced electron transport efficiency and more stable channel structure achieved from the doped conductive carbon. The reaction mechanism and structural evolution of the ZVO@C electrode are analyzed using X-ray diffraction and X-ray photoelectron spectroscopy, revealing the formation of a new phase of ZnxV2O5·nH2O during the first charge, which participates in reversible cycling together with ZVO@C during the charging and discharging processes. Moreover, the energy storage mechanism is revealed, in which zinc ions and hydrogen ions jointly participate in intercalation and extraction. The present study demonstrates that constructing composite vanadium-based oxides based on bimetallic organic frameworks as precursor templates is an effective strategy for the development of high-performance cathode materials for AZIBs.

Manganese-Based Oxide Cathode Materials for Aqueous Zinc-Ion Batteries: Materials, Mechanism, Challenges, and Strategies

Aqueous zinc-ion batteries (AZIBs) have recently attracted worldwide attention due to the natural abundance of Zn, low cost, high safety, and environmental benignity. Up to the present, several kinds of cathode materials have been employed for aqueous zinc-ion batteries, including manganese-based, vanadium-based, organic electrode materials, Prussian Blues, and their analogues, etc. Among all the cathode materials, manganese (Mn)-based oxide cathode materials possess the advantages of low cost, high theoretical specific capacity, and abundance of reserves, making them the most promising cathode materials for commercialization. However, several critical issues, including intrinsically poor conductivity, sluggish diffusion kinetics of Zn2+, Jahn-Teller effect, and Mn dissolution, hinder their practical applications. This Review provides an overview of the development history, research status, and scientific challenges of manganese-based oxide cathode materials for aqueous zinc-ion batteries. In addition, the failure mechanisms of manganese-based oxide materials are also discussed. To address the issues facing manganese-based oxide cathode materials, various strategies, including pre-intercalation, defect engineering, interface modification, morphology regulation, electrolyte optimization, composite construction, and activation of dissolution/deposition mechanism, are summarized. Finally, based on the analysis above, we provide future guidelines for designing Mn-based oxide cathode materials for aqueous zinc-ion batteries.

Engineering improved strategies for spinel cathodes in high-performing zinc-ion batteries

The development of high-performing cathode materials for aqueous zinc-ion batteries (ZIBs) is highly important for the future large-scale energy storage. Owing to the distinctive framework structure, diversity of valences, and high electrochemical activity, spinel materials have been widely investigated and used for aqueous ZIBs. However, the stubborn issues of low electrical conductivity and sluggish kinetics plague their smooth applications in aqueous ZIBs, which stimulates the development of effective strategies to address these issues. This review highlights the recent advances of spinel-based cathode materials that include the configuration of aqueous ZIBs and corresponding reaction mechanisms. Subsequently, the classifications of spinel materials and their properties are also discussed. Then, the review mainly summarizes the effective strategies for elevating their electrochemical performance, including their morphology and structure design, defect engineering, heteroatom doping, and coupling with a conductive support. In the final section, several sound prospects in this fervent field are also proposed for future research and applications.

Application of Biomass Materials in Zinc-Ion Batteries

Currently, aqueous zinc-ion batteries, with large reserves of zinc metal and maturity of production, are a promising alternative to sustainable energy storage. Nevertheless, aqueous solution has poor frost resistance and is prone to side reactions. In addition, zinc dendrites also limit the performance of zinc-ion batteries. Biomass, with complex molecular structure and abundant functional groups, makes it have great application prospects. In this review, the research progress of biomass and its derived materials used in zinc-ion batteries are reviewed. The different regulation strategies and characteristics of biomass used in zinc-ion battery electrodes, electrolyte separators and binders are demonstrated. The regulation mechanism is analyzed. At the end, the development prospect and challenges of biomass in energy materials application are proposed.

Bio-Template Synthesis of V2O3@Carbonized Dictyophora Composites for Advanced Aqueous Zinc-Ion Batteries

In terms of new-generation energy-storing devices, aqueous zinc-ion batteries (AZIBs) are becoming the prime candidates because of their inexpensive nature, inherent safety, environmental benignity and abundant resources. Nevertheless, due to a restrained selection of cathodes, AZIBs often perform unsatisfactorily under long-life cycling and high-rate conditions. Consequently, we propose a facile evaporation-induced self-assembly technique for preparing V₂O₃@carbonized dictyophora (V₂O₃@CD) composites, utilizing economical and easily available biomass dictyophora as carbon sources and NH₄VO₃ as metal sources. When assembled in AZIBs, the V₂O₃@CD exhibits a high initial discharge capacity of 281.9 mAh g^-1 at 50 mA g^-1. The discharge capacity is still up to 151.9 mAh g^-1 after 1000 cycles at 1 A g^-1, showing excellent long-cycle durability. The extraordinary high electrochemical effectiveness of V₂O₃@CD could be mainly attributed to the formation of porous carbonized dictyophora frame. The formed porous carbon skeleton can ensure efficient electron transport and prevent V₂O₃ from losing electrical contact due to volume changes caused by Zn²⁺ intercalation/deintercalation. The strategy of metal-oxide-filled carbonized biomass material may provide insights into developing high-performance AZIBs and other potential energy storage devices, with a wide application range.

Mesoporous carbon material prepared from sewage sludge hydrochar using Pluronic F127 as template for efficient removal of phenolic compounds: Experimental study and mechanism interpretation via advanced statistical physics model

Mesoporous carbon material (MCM) with rich ether surface group was prepared from sewage sludge hydrochar using Pluronic F127 as template under pyrolysis activation, which provided an energy-efficient method to promote the resource utilization of sewage sludge as adsorbents for phenols removal from water. The MCM possessed high surface area (549 m²/g), abundant mesopores (average width 3.81 nm) and well-developed graphite structure. Acidic conditions and low temperatures favored the adsorption of phenolic compounds. The quick adsorption process of reaching over 85% of the capacity in the first 10 min and intraparticle diffusion as primary rate-limiting step were observed for all phenolic compounds. Advanced statistical physics analysis was used successfully to interpret the adsorption mechanism of phenols onto MCM and revealed a multi-molecular monolayer adsorption process primarily through negative charge-assisted hydrogen bond interaction where the ether functional group contributed to the predominant active sites. The adsorption capacity of phenolic compounds depended upon the number of molecules adsorbed per ether active site and the available density of ether bond group on the surface of MCM. 2,4,6-trichlorophenol showed a highest adsorption priority to occupy the limited ether active sites and its adsorption capacity reached 0.49 mmol/g, while p-nitrophenol exhibited a maximum number of molecules adsorbed on the single ether active site, showing an adsorption capacity of 0.42 mmol/g. The synergistic effect of multi-interactions mechanisms resulted in phenolic compounds removal with adsorption energies lower than 30 kJ/mol. This prepared MCM adsorbent is promising for application in treatment of water polluted by phenols.

A Review of MnO2 Composites Incorporated with Conductive Materials for Energy Storage

Manganese dioxide (MnO₂ ) has been widely used in the field of energy storage due to its high specific capacitance, low cost, natural abundance, and being environmentally friendly. However, suffering from poor electrical conductivity and high dissolvability, the performance of MnO₂ can no longer meet the needs of rapidly growing technological development, especially for the application as electrode material in metal-ion batteries and supercapacitors. In this review, recent studies on the development of binary or multiple MnO₂ -based composites with conductive components for energy storage are summarized. Firstly, general preparing methods for MnO₂ -based composites are introduced. Subsequently, the binary and multiple MnO₂ -based composites with carbon, conducting polymer, and other conductive materials are discussed respectively. The improvement in their performance is summarized as well. Finally, perspectives on the practical applications of MnO₂ -based composites are presented.

Hydrogen Bond Shielding Effect for High-Performance Aqueous Zinc Ion Batteries

Manganese oxides are highly desirable for the cathode of rechargeable aqueous zinc ion batteries (AZIBs) owing to their low cost and high abundance. However, the terrible structure stability of manganese oxide limits its practical application. Here, it is demonstrated that the hydrogen-bond shielding effect can improve the electrochemical performance of manganese oxide. Briefly, (NH₄ )_0.125 MnO₂ (NHMO) is prepared by introducing NH₄ ⁺ into the tunnel structure of α-MnO₂ . The robust hydrogen bonds between N-H and host O atoms can stabilize the lattice structure of α-MnO₂ and suppress the dissolution of Mn element. More importantly, it can also accelerate ions mobility kinetics by weakening the electrostatic interaction of host O atoms. Thus, the fabricated Zn||NHMO battery possesses impressive cycling life (99.5% of capacity retention over 10 000 cycles) and rate capability (109 mA h g^-1 of discharge capacity at 6000 mA g^-1 ). Comprehensive analyses reveal the essences of interfacial charge and bulk ions transfer. This finding opens new opportunities for the development of high-performance AZIBs.

Stability Optimization Strategies of Cathode Materials for Aqueous Zinc Ion Batteries: A Mini Review

Among the new energy storage devices, aqueous zinc ion batteries (AZIBs) have become the current research hot spot with significant advantages of low cost, high safety, and environmental protection. However, the cycle stability of cathode materials is unsatisfactory, which leads to great obstacles in the practical application of AZIBs. In recent years, a large number of studies have been carried out systematically and deeply around the optimization strategy of cathode material stability of AZIBs. In this review, the factors of cyclic stability attenuation of cathode materials and the strategies of optimizing the stability of cathode materials for AZIBs by vacancy, doping, object modification, and combination engineering were summarized. In addition, the mechanism and applicable material system of relevant optimization strategies were put forward, and finally, the future research direction was proposed in this article.

Cyclic Ether-Water Hybrid Electrolyte-Guided Dendrite-Free Lamellar Zinc Deposition by Tuning the Solvation Structure for High-Performance Aqueous Zinc-Ion Batteries

The serious zinc dendrites and poor cyclability at high cathode loading owing to the strong solvation effect of traditional aqueous electrolytes are the main bottlenecks to the development of aqueous rechargeable zinc-ion batteries (ARZIBs). Here, we design an ether-water hybrid zinc-ion electrolyte with bifunctional roles of not only unplugging the dendrites bottleneck at the Zn anode but also extending the cycle life at high cathode loading. A cyclic ether (1,4-dioxane (DX)) is incorporated into traditional ZnSO₄-based electrolytes to finely tune the solvation sheath of Zn²⁺. DX is found to guide the deposition orientation of zinc along the (002) plane, leading to not a dendritic structure but distinctively dense lamellar deposition due to the stronger affinity of the cyclic DX molecules toward Zn(002) than that of water, which is proven by density functional theory calculations. The cycling lifespan of the Zn anode extends up to over 600 h at 5.0 mA cm^-2 and maintains extremely high Coulombic efficiency of 99.8%, thereby further enabling the Zn-MnO₂ full cells to stably cycle at an ultrahigh mass loading of 9.4 mg cm^-2, paving the way to their practical applications. This work also provides a novel electrolyte regulating solution for other aqueous multivalent metal-ion batteries.

Intimately coupled Mn3O4nanocrystalline@3D honeycomb hierarchical porous network scaffold carbon for high-performance cathode of aqueous zinc-ion batteries

Herein, 3D honeycomb hierarchical porous network scaffold carbon is synthesized by a unique PVP-SiO₂-boiling method with the boiling bubbles as soft template and SiO₂nanospheres as hard template. Then MnO₂nanosheets intimately grow on the carbon matrix and are further decomposed to Mn₃O₄nanocrystalline with size of 7-9 nm. The obtained Mn₃O₄nanocrystalline@3D honeycomb hierarchical porous network scaffold carbon has abundant mesopores and large specific surface area (92 m²g^-1). When used as a cathode material for zinc-ion batteries, the synthesized composites exhibit high reversible capacity (546.2 mAh g^-1at 0.5 A g^-1), remarkable cycling stability (discharge capacity of 97.8 mAh g^-1at 3 A g^-1after 600 cycles) and superior rate capability (15.7 mAh g^-1at 10 A g^-1). The kinetics analyses indicate zinc storage mechanism includes diffusion process and capacitive process of Zn²⁺and H⁺ions, and the capacitive storage is dominant. The outstanding zinc storage performance benefits from the structural advantages. The unique carbon matrix improves electronic conductivity of Mn₃O₄, facilitates penetration of electrolyte, and well supports Mn₃O₄nanocrystalline. The small size and large specific surface area of Mn₃O₄nanocrystalline induce significant capacitive storage effect.

Surface modification of manganese monoxide through chemical vapor deposition to attain high energy storage performance for aqueous zinc-ion batteries

Surface modification of the manganese-based oxide electrode is considered to be a viable strategy to improve electrochemical property in aqueous zinc-ion batteries (ZIBs). However, the modification method through traditional wet-chemical technology can hardly to satisfy high rate capability for aqueous ZIBs due to unhomogeneous and nonconformal coating originates from surface energy mismatch. Herein, a surface modification strategy based on chemical vapor deposition is developed to enhance the electrochemical property of the inactive MnO in aqueous ZIBs. The constructed carbon coating modified MnO electrode shows excellent reversible capacity and superior rate capability with remarkable energy density of 351 Wh kg^-1 at 625 W kg^-1. The energy storage mechanism of the electrode during the charge and discharge processes is elucidated according to the ex-situ measurements of X-ray diffraction and photoelectron spectroscopy, Fourier transform infrared spectra, and galvanostatic intermittent titration techniques. Moreover, soft-packaged batteries are fabricated with the carbon coating modified MnO, which shows great promises for the practical application of the material. The work paves the way for the exploitation of high performance surface-modified electrode through chemical vapor deposition for aqueous ZIBs.