Recent Advances on Challenges and Strategies of Manganese Dioxide Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries(AZIBs)are regarded as promising electrochemical energy storage devices owing to its low cost,intrinsic safety,abundant zinc reserves,and ideal specific capacity.Compared with other cathode materials,manganese dioxide with high voltage,environmental protection,and high theoretical specific capacity receives considerable attention.However,the problems of structural instability,manganese dissolution,and poor electrical conductivity make the exploration of high-performance manganese dioxide still a great challenge and impede its practical applications.Besides,zinc storage mechanisms involved are complex and somewhat controversial.To address these issues,tremendous efforts,such as surface engineering,heteroatoms doping,defect engineering,electrolyte modification,and some advanced characterization technologies,have been devoted to improving its electrochemical performance and illustrating zinc storage mechanism.In this review,we particularly focus on the classification of manganese dioxide based on crystal structures,zinc ions storage mechanisms,the existing challenges,and corresponding optimization strategies as well as structure-performance relationship.In the final section,the application perspectives of manganese oxide cathode materials in AZIBs are prospected.

Concentrations of copper, zinc and manganese in Tree Sparrow (Passer montanus) at Jixi, Heilongjiang Province, China

Concentrations of copper （Cu）, zinc （Zn） and manganese （Mn） were measured in four tissues of Tree Sparrow （Passer montanus） from three sites in Heilongjiang province, China, during four seasons. Among the four measured tissues （primary feathers, liver, heart, and pectoral muscle）, the highest concentrations were found in feathers （Zn） or liver （Cu and Mn）, and the lowest concentrations were in muscle, except Cu. For Mn, mean concentrations of the birds from the three study sites were, in decreasing order： Didao mining area （DMA） 〉 urban district of Jixi （UDJ） 〉 Phoenix Mountain national nature reserve （PMR, the reference site）, but not for Zn and Cu. There were significant differences between metal concentrations at the three sites, but differences were not significant for Mn （in muscle and feathers） and Cu （in feathers）. For most elements, the mean concentrations were greatest in summer.

INFLUENCE OF ZINC，MANGANESE AND SELENIUM ONSUPEROXIDE DISMUTASE ACTIVITY IN LUNGCANCER TISSUE AND CELL IN CULTURE

In this experiment,the cancer tissues and cells,Which were derived from Lewis lung cancer and A549 lung Cancer cell line,were respectively divided into four groups and zinc, manganese and selenium were respectively added to the medium for 24 hours. The superoxide dismutase activity in the tissues and the cells was estimated. It was found that the SOD activity was enhanced by zinc and manganese and the effect of zinc on SOD activity was superior to that of manganese. We supposed that the enhance of the SOD activity was relative to the activation of the SOD apoenzymes. This experimental result indicated that the inhibitory effect of zinc and manganese on carcinogenesis was achieved by SOD and the elements might be considered a SOD activator.

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnOnanoparticles(α-MnO@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO@C was prepared via a gel formation, using maleic acid(CHO) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnOnanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnOelectrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.

MOF-derived zinc manganese oxide nanosheets with valence-controllable composition for high-performance Li storage

Zinc manganese oxide(ZMO)system represents a notable family of mixed transition metal oxides(MTMOs)because of their superiority of the high theoretical capacity,adequacy of natural content,and low cost.However,the methods to match both the reliable synthesis and the designable construction of large-sized two-dimensional(2D)ZMO nanosheets are still considered as grand challenges.Herein,we have successfully realized the preparation of 2D ZMO nanosheets with large lateral sizes up to~20 mm by simple pyrolysis of 2D metal–organic framework(MOF)nanosheets precursor.The growth mechanism of 2D MOF is proposed to be based on the lamellar micelles formed by polyvinyl pyrrolidone(PVP).The obtained 2D and porous ZMO nanosheets exhibit high specific capacity as well as good rate capability.More importantly,the as-prepared ZMO electrode shows a remarkable capacity increment upon cycling(from 832 mAh g^(-1) at the 2nd cycle to 1418 mAh g^(-1) at the 700th cycle,at 1 A g^(-1)).Through simple adjustment of the calcination temperature,the valence state of Mn species in the yielding ZMO samples can be fine-tuned.Through systematic investigation towards these ZMOs containing different Mn species,the extra specific capacity is revealed to be chiefly on account of the arising of the valence state of Mn upon the cycling process.Moreover,it is disclosed that the higher-valent Mn the pristine ZMO contains,the more additional capacity it gains upon cycling.We believe that this work will inspire more detailed analysis on the relationship between the valence state of Mn and extra capacity.

High-Performance Aqueous Zinc–Manganese Battery with Reversible Mn^(2+)/Mn^(4+) Double Redox Achieved by Carbon Coated MnO_x Nanoparticles

There is an urgent need for low-cost,high-energy-density,environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage.Multi-electron redox is considerably crucial for the development of high-energy-density cathodes.Here we present highperformance aqueous zinc-manganese batteries with reversible Mn2+/Mn4+ double redox.The active Mn4+is generated in situ from the Mn2+-containing MnOx nanoparticles and electrolyte.Benefitting from the low crystallinity of the birnessite-type MnO2 as well as the electrolyte with Mn2+additive,the MnOX cathode achieves an ultrahigh energy density with a peak of845.1 Wh kg-1 and an ultralong lifespan of 1500 cycles.The combination of electrochemical measurements and material characterization reveals the reversible Mn2+/Mn4+double redox(birnessite-type MnO2? monoclinic MnOOH and spinel ZnMn2O4 H?Mn2+ions).The reversible Mn2+/Mn4+double redox electrode reaction mechanism offers new opportunities for the design of low-cost,high-energy-density cathodes for advanced rechargeable aqueous batteries.

Flexible Zinc-Manganese Dioxide Alkaline Batteries Based on Kelp Electrolytes

Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.

Effect of Sintering Conditions on Structure of Manganese Zinc Ferrite Powders

The structures of the Mn-Zn ferrites synthesized under different sintering conditions by the sol-gel method were investigated by the X-ray diffraction （XRD） and the scanning electron microscopy （SEM） with focus on two factors： the pre-sintering treatment and the calcining time. The results show that the sintering conditions have significant effects on the structures and the particle size of the Mn-Zn ferrites. Compared with the products without pre-sintering, those pre-sintered at 500℃ have a single phase and no diffraction peaks of Fe2O3 that could be found. The effects of the pre-sintering temperature on the structures of the ferrites were also studied. As a result, 500℃ proves to be the favorite in the pre-sintering treatment. The XRD patterns of the ferrites calcined at 1 200℃ for 6 h will present diffraction peaks of pure crystallization of spinel phase while those for 2 h or 4 h will show peaks of Fe2O3. The SEM also bears witness to well-grown grains of pure Mn-Zn ferrites if calcined for 6 hours.

Spectrophotometric Simultaneous Determination of Zinc(II), Manganese(II) and Iron(II) in Pharmaceutical Preparations Using OSC-PLS

This work reports the spectrophotometric simultaneous determination of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） in pharmaceutical preparation, using orthogonal signal correctionpartial least squares （OSC-PLS）. All the factors affecting on the sensitivity were optimized and the linear dynamic range for determination of these metals was found. The PLS modeling was used for the multivariate calibration of the spectrophotometric data. The OSC was used for preprocessing of data matrices and the prediction results of model. The experimental calibration matrix was designed by measuring the absorbance over the range 450-570 nm for 21 samples of 0.05-1.05, 0.10-1.10 and 0.05-1.05μg·mL^-1 of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ）, respectively. The RMSEP for zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） using OSC-PLS were 0.0164, 0.0132, 0.0146, respectively. The proposed method was successfully applied the determination of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） in pharmaceutical preparations.

LR6,LR03 Alkaline Hige Energy Zinc and Manganese Battery

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A Binder-Free Amorphous Manganese Dioxide for Aqueous Zinc-Ion Battery

Aqueous zinc-ion battery has attracted much attention due to its low price, high safety, and high theoretical specific capacity. However, most of their performances are limited by the unsatisfied architecture of cathodes. Herein, we fabricated amorphous manganese dioxide by an in situ deposition method. The amorphous manganese dioxide can directly serve as the cathode of an aqueous zinc-ion battery without a binder. The resultant cathode exhibits a high specific capacity of 133.9 mAh/g at 200 mA/g and a capacity retention of 82% over 50 cycles at 1 A/g.

Rational design of interfacial bonds within dual carbon-protected manganese oxide towards durable aqueous zinc ion battery

Manganese-based cathode materials are promising candidates for aqueous zinc ion batteries(AZIBs)by reason of their low cost and high energy density.However,their practical applicability is hampered by the intrinsic defects of poor electrical conductivity,sluggish reaction kinetics,and severe structural deterioration.Herein,we constructed a hierarchically porous structure composed of carbon-encapsulated Mn O nanoparticles(MOC)and three-dimensional(3D)nitrogen-doped graphene aerogel(NGA)(denoted as MOC@NGA).The hybrid was synthesized by a facile in-situ coprecipitation and annealing of manganesebased metal-organic framework(Mn-MOF74)and NGA composite(Mn-MOF74@NGA).Specifically,the carbon shells inherited from organic ligand of Mn-MOF74 could restrain the volume changes of Mn O,and the porous NGA prevented the agglomeration of MOC nanoparticles and enriched the types of interfacial chemical bonds.Profiting from the synergistic effect of rich interface chemical bonds and dual-carbon protection,the MOC@NGA hybrids exhibit fast interfacial electron/charge transfer and transport,and outstanding structural stability.Therefore,MOC@NGA cathode delivers an excellent rate performance(270 and 99.8 m Ah g^(-1)at 0.1 and 2.0 A g^(-1))and maintains an excellent specific capacity of 151.6 m Ah g^(-1)after 2,000cycles at 1.0 A g^(-1).Moreover,the fabricated MOC@NGA-based quasi-solid-state battery not only achieves outstanding flexibility but also displays impressive cycling stability,demonstrating a promising potential for portable and flexible equipment.This work provides a feasible strategy for the fabrication of the bridging structure of manganese-based oxides and porous carbon matrix for high-specific capacity and durable AZIBs cathodes.

β-MnO_(2) with proton conversion mechanism in rechargeable zinc ion battery

Rechargeable aqueous zinc ion battery(RAZIB)is a promising energy storage system due to its high safety,and high capacity.Among them,manganese oxides with low cost and low toxicity have drawn much attention.However,the under-debate proton reaction mechanism and unsatisfactory electrochemical performance limit their applications.Nanorod b-MnO_(2) synthesized by hydrothermal method is used to investigate the reaction mechanism.As cathode materials for RAZIB,the Zn//b-MnO_(2) delivers 355 mA h g^(-1)(based on cathode mass)at0.1 A g^(-1),and retain 110 mA h g^(-1) after 1000 cycles at 0.2 A g^(-1).Different from conventional zinc ion insertion/extraction mechanism,the proton conversion and Mn ion dissolution/deposition mechanism of b-MnO_(2) is proposed by analyzing the evolution of phase,structure,morphology,and element of b-MnO_(2) electrode,the pH change of electrolyte and the determination of intermediate phase MnO OH.Zinc ion,as a kind of Lewis acid,also provides protons through the formation of ZHS in the proton reaction process.This study of reaction mechanism provides a new perspective for the development of Zn//MnO_(2) battery chemistry.

Defect-engineered Mn_(3)O_(4)/CNTs composites enhancing reaction kinetics for zinc-ions storage performance

The designing of reasonable nanocomposite materials and proper introduction of defect engineering are of great significance for the improvement of the poor electronic conductivity and slow reaction kinetics of manganese-based compounds. Herein, we report manganese-deficient Mn_(3)O_(4) nanoparticles which grow in-situ on highly conductive carbon nanotubes(CNTs)(denoted as DMOC) as an advanced cathode material for aqueous rechargeable zinc-ion batteries(RAZIBs). According to experimental and calculation results, the DMOC cathode integrates the advantages of enriched Mn defects and small particle size. These features not only enhance electronic conductivity but also create more active site and contribute to fast reaction kinetics. Moreover, the structure of DMOC is maintained during the charging and discharging process, thus benefiting for excellent cycle stability. As a result, the DMOC electrode delivers a high specific capacity of 420.6 m A h g^(-1) at 0.1 A g^(-1) and an excellent cycle life of 2800 cycles at 2.0 A g^(-1) with a high-capacity retention of 84.1%. In addition, the soft-packaged battery assembled with DMOC cathode exhibits long cycle life and high energy density of 146.3 Wh kg^(-1) at 1.0 A g^(-1) . The results are beneficial for the development of Zn/Mn_(3)O_(4) battery for practical energy storage.

Trace metals and animal health: Interplay of the gut microbiota with iron, manganese, zinc, and copper

Metals such as iron,manganese,copper,and zinc are recognized as essential trace elements.These trace metals play critical roles in development,growth,and metabolism,participating in various metabolic processes by acting as cofactors of enzymes or providing structural support to proteins.Deficiency or toxicity of these metals can impact human and animal health,giving rise to a number of metabolic and neurological disorders.Proper breakdown,absorption,and elimination of these trace metals is a tightly regulated process that requires crosstalk between the host and these micronutrients.The gut is a complex system that serves as the interface between these components,but other factors that contribute to this delicate interaction are not well understood.The gut is home to trillions of microorganisms and microbial genes(the gut microbiome)that can regulate the metabolism and transport of micronutrients and contribute to the bioavailability of trace metals through their assimilation from food sources or by competing with the host.Furthermore,deficiency or toxicity of these metals can modulate the gut microenvironment,including microbiota,nutrient availability,stress,and immunity.Thus,understanding the role of the gut microbiota in the metabolism of manganese,iron,copper,and zinc,as well as in heavy metal deficiencies and toxicities,and vice versa,may provide insight into developing improved or alternative therapeutic strategies to address emerging health concerns.This review describes the current understanding of how the gut microbiome and trace metals interact and affect host health,particularly in pigs.

Sol-gel preparation and phosphorescence property of Mn^(2+)-doped zinc boro-silicate glass thin films

Mn2＋-doped zinc borosilicate （ZBSM） glass thin films were first synthesized by sol-gel method. In the experiment, a thin gel film was depos-ited onto quartz glass substrates by dip-coating method and then heat-treated to form a Mn2＋-doped zinc borosilicate glass thin film. Long lasting phosphorescence （LLP） and photo-stimulated long lasting phosphorescence （PSLLP） were found in the film sample. According to fluorescence spectra, LLP emission spectra, and PSLLP emission spectra, both LLP and PSLLP emissions are attributed to the energy level transition of 4Eg→4A1g from Mn2＋. Both the phosphorescence intensity decay curves contain a fast decay component and another slow decay one. The thermoluminescence （TL） spectra show that the sample has two kinds of traps at least and their energy level values are about 0.8 eV and 1.02 eV, which could be estimated by the Randall and Willcins formula. The infrared absorption spectra （IR） consist of characteristic vi-bration bands of Si-O-Si, Si-O-Zn, B-O in [BO3], B-O group, and Zn-O in [ZnO4]. Moreover, image storage and logical operation of the ZBSM film were carried out successfully through an experiment analogues of optical storage.

Oxygen‑Deficient β‑MnO_(2)@Graphene Oxide Cathode for High‑Rate and Long‑Life Aqueous Zinc Ion Batteries

Recent years have witnessed a booming interest in grid-scale electrochemical energy storage,where much attention has been paid to the aqueous zinc ion batteries(AZIBs).Among various cathode materials for AZIBs,manganese oxides have risen to prominence due to their high energy density and low cost.However,sluggish reaction kinetics and poor cycling stability dictate against their practical application.Herein,we demonstrate the combined use of defect engineering and interfacial optimization that can simultaneously promote rate capability and cycling stability of MnO_(2) cathodes.β-MnO_(2) with abundant oxygen vacancies(VO)and graphene oxide(GO)wrapping is synthesized,in which VO in the bulk accelerate the charge/discharge kinetics while GO on the surfaces inhibits the Mn dissolution.This electrode shows a sustained reversible capacity of~129.6 mAh g^(−1) even after 2000 cycles at a current rate of 4C,outperforming the state-of-the-art MnO_(2)-based cathodes.The superior performance can be rationalized by the direct interaction between surface VO and the GO coating layer,as well as the regulation of structural evolution ofβ-MnO_(2) during cycling.The combinatorial design scheme in this work offers a practical pathway for obtaining high-rate and long-life cathodes for AZIBs.

Oxide-based cathode materials for rechargeable zinc ion batteries:Progresses and challenges

With the increasing demands for electrical energy storage technologies,rechargeable zinc ion batteries(ZIBs)have been rapidly developed in recent years owing to their high safety,low cost and high energy storage capability.The cathode is an essential part of ZIBs,which hosts zinc ions and determines the capacity,rate and cycling performance of the battery.The mainstream cathodes for ZIBs are oxidebased materials with tunnel,layer or 3 D crystal structures.In this review,we mainly focus on the latest advanced oxide-based cathode materials in ZIBs,including manganese oxides,vanadium oxides,spinel compounds,and other metal oxide based cathodes.In addition,the mechanisms of zinc storage and recent development in cathode design have been discussed in detail.Finally,current challenges and perspectives for the future research directions of oxide-based cathodes in ZIBs are presented.

Molten salt synthesis of α-MnO_(2)/Mn_(2)O_(3) nanocomposite as a high-performance cathode material for aqueous zinc-ion batteries

Thanks to low cost,high safety,and large energy density,aqueous zinc-ion batteries have attracted tremendous interest worldwide.However,it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production.Herein,we use a molten salt method to synthesize nanostructured manganese oxides.The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture.It is found that the α-MnO_(2)/Mn_(2)O_(3) nanocomposite with the largest mass ratio of Mn_(2)O_(3) delivers the best electrochemical performances among all the products.And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder.In this situation,the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g^(-1) at 0.2 and 3 Ag^(-1),respectively.After 1000 cycles,it can retain 86.2% of the capacity at the 2 nd cycle.Thus,this nanocomposite holds great promise for practical applications.