Heterointerface Engineering-Induced Oxygen Defects for the Manganese Dissolution Inhibition in Aqueous Zinc Ion Batteries

Manganese-based material is a prospective cathode material for aqueous zinc ion batteries(ZIBs)by virtue of its high theoretical capacity,high operating voltage,and low price.However,the manganese dissolution during the electrochemical reaction causes its electrochemical cycling stability to be undesirable.In this work,heterointerface engineering-induced oxygen defects are introduced into heterostructure MnO_(2)(δa-MnO_(2))by in situ electrochemical activation to inhibit manganese dissolution for aqueous zinc ion batteries.Meanwhile,the heterointerface between the disordered amorphous and the crystalline MnO_(2)ofδa-MnO_(2)is decisive for the formation of oxygen defects.And the experimental results indicate that the manganese dissolution ofδa-MnO_(2)is considerably inhibited during the charge/discharge cycle.Theoretical analysis indicates that the oxygen defect regulates the electronic and band structure and the Mn-O bonding state of the electrode material,thereby promoting electron transport kinetics as well as inhibiting Mn dissolution.Consequently,the capacity ofδa-MnO_(2)does not degrade after 100 cycles at a current density of 0.5 Ag^(-1)and also 91%capacity retention after 500cycles at 1 Ag^(-1).This study provides a promising insight into the development of high-performance manganese-based cathode materials through a facile and low-cost strategy.

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Manganese Dioxide with High Specific Surface Area for Alkaline Battery

The authors reported a facile method for the synthesis of manganese dioxide without any template and catalyst at a low-temperature. The prepared sample was characterized with X-ray diffraction（XRD）, scanning electron microscopy（SEM）, Brunauer-Emmett-Teller（BET） surface analysis, Fourier transform infrared（FTIR） spectrometry, cyclic voltammetry, alternative current（AC） impedance test and battery discharge test. It is found that the prepared sample belongs to α-MnO2 and has a microsphere morphology and a large BET surface area. The electrochemical characterization indicates that the prepared sample displays a larger electrochemical capacitance than the commercial electrolytic manganese dioxides（EMD） in Na2SO4 solution, and exhibits larger discharge capacity than EMD, especially at a high rate discharge condition when it is used as cathode of alkaline Zn/MnO2 battery.

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.

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.

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.

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.

Effect of magnesium on the aluminothermic reduction rate of zinc oxide obtained from spent alkaline battery anodes for the preparation of Al–Zn–Mg alloys

The aluminothermic reduction of zinc oxide（ZnO） from alkaline battery anodes using molten Al may be a good option for the elaboration of secondary 7000-series alloys. This process is affected by the initial content of Mg within molten Al, which decreases the surface tension of the molten metal and conversely increases the wettability of ZnO particles. The effect of initial Mg concentration on the aluminothermic reduction rate of ZnO was analyzed at the following values： 0.90wt%, 1.20wt%, 4.00t%, 4.25wt%, and 4.40wt%. The ZnO particles were incorporated by mechanical agitation using a graphite paddle inside a bath of molten Al maintained at a constant temperature of 1123 K and at a constant agitation speed of 250 r/min, the treatment time was 240 min and the ZnO particle size was 450？500 mesh. The results show an increase in Zn concentration in the prepared alloys up to 5.43wt% for the highest initial concentration of Mg. The reaction products obtained were characterized by scanning electron microscopy and X-ray diffraction, and the efficiency of the reaction was measured on the basis of the different concentrations of Mg studied.

Determination of the density of zinc powders for alkaline battery

The density of zinc powder for alkaline battery was determined using a pyknometer.The results showed that powders made before the end of 2003 could reach relative densities above 99% of the theoretical density.Investigating the relative volume swelling of electrolysed gels of zinc powders,no evident relation between swelling and pyknometer density was found.

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.

Design strategy and comprehensive performance assessment towards Zn anode for alkaline rechargeable batteries

Alkaline Zn-based primary batteries have been commercialized in the past decades.However,their success has not been extended to secondary batteries due to the poor cycle reversibility of Zn anodes.Although some research has been conducted on alkaline Zn anodes,their performance is still far from commercial requirements.A variety of degradation mechanisms,including passivation,dendrites,morphological changes,and hydrogen precipitation,are claimed responsible for the failure of alkaline Zn metal anodes.What’s worse,these constraints always interact with each other,which leads to a single strategy being unable to suppress all the issues.Therefore,a comprehensive evaluation of the positive and negative effects of various strategies on performance is important to promote the commercialization of alkaline Zn batteries.Herein,the recent progress and performance of improvement strategies for Zn anode in alkaline conditions are reviewed systematically.First,the principles and challenges of alkaline Zn anodes are briefly analyzed.Then,various design strategies for alkaline Zn anodes from the perspectives of ion and electron regulation are highlighted.Last,through a comprehensive summary of various performance parameters,the advantages and disadvantages of different strategies are compared and evaluated.On the basis of this assessment,we aim to provide more insights into the anode design of high-performance alkaline rechargeable Zn batteries.

PVDF-HFP binder for advanced zinc−manganese batteries

In order to optimize and select the appropriate binder to improve the electrochemical performance of aqueous zinc-manganese batteries,the influences of water-soluble binders and oil-based binders on the zinc storage performance of manganese-based cathode materials were systematically investigated.The results show that the water-soluble binders with large numbers of hydroxyl and carboxyl groups are easily soluble in aqueous electrolytes,leading to poor electrochemical performance.Fortunately,the cathodes with polyvinylidene fluoride-hexafluoropropylene(PVDF-HFP)binder display high specific capacity of 264.9 mA·h/g and good capacity retention of 92%after 90 cycles at 100 mA/g.Meanwhile,PVDF-HFP binder with plenty of hydrophobic groups presents excellent ability in inhibiting cracks on the surface of electrode,reducing voltage polarization and charge transfer resistance,as well as maintaining electrode integrity.

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.

NixB/rGO as the cathode for high-performance aqueous alkaline zinc-based battery

Aqueous alkaline zinc batteries(AZBs)exhibit great potential due to their high capacity,high safety and low cost.However,despite these advantages,the lack of high stability and high utilization rate makes the search for high-performance cathode materials a great challenge.Here,an amorphous nickel boride/rGO(NixB/rG O)complex structure was designed.As a result of abundant unsaturated active sites and synergistic electronic effects,amorphous NixB exhibits excellent energy storage properties.As well as having high electrical conductivity,rGO avoids aggregation of NixB nanoparticles,ensuring that NixB/rGO electrodes have a high energy storage capacity.The structure has a strong adhesion between NixB and rGO,which protects its stable structure and extends its life.More importantly,the NixB/rGO//Zn full battery shows remarkable capacity(228.4 m Ah/g at 2 A/g),extraordinary cycle durability(93.7%retained after1000 cycles)and strong energy density 399.7 Wh/kg,when coupled with NixB/rGO cathode.This work will also shed light on other nickel-zinc batteries in order to achieve super durability and capacity.

Manganese vanadium oxide composite as a cathode for high-performance aqueous zinc-ion batteries

The development of clean renewable energy and energy storage devices is of great significance under the present energy crisis and environmental pollution background.Aqueous zinc-ion battery(ZIB)has become one of the most promising energy storage devices due to its high capacity,safety and low cost.However,the application of ZIB cathode is usually limited by low capacity and poor stability.Herein,we propose a novel heterostructure MnO/MnV_(2)O_(4)composite material composed of MOF derivatives and spinel with dual active components as cathode for ZIBs.Benefited from substantial framework of MOF derivatives and the synergistic effect of heterostructures,MnO/MnV_(2)O_(4)exhibits excellent rate performance(342 m Ah/g at 0.1 A/g,261 mAh/g at 15 A/g)and cycling performance(198.9 mAh/g at 10 A/g after 2000 cycles)in3 mol/L Zn(CF_(3)SO_(3))2electrolytes.This work extends the range of developing high-performance cathodes for ZIBs under high current density and is expected to enlighten the optimization of commercial energy storage devices.

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.

Effects of current density on preparation of grainy electrolytic manganese dioxide

Grainy electrolytic manganese dioxide was prepared by electrodeposition in a 0.9 mol/L MnSO4 and 2.5 mol/LH2SO4 solution. The structure, particle size and appearance of the grainy electrolytic manganese dioxide were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrographs measurements. Current density has important effects on cell voltage, anodic current efficiency and particle size of the grainy electrolytic manganese dioxide, and the optimum current density is 30 A/dm2. The grainy electrolytic manganese dioxide electrodeposited under the optimum conditions consists of γ-MnO2 with an orthorhombic lattice structure; the grainy electrolytic manganese dioxide has a spherical or sphere-like appearance and a narrow particle size distribution with an average particle diameter of 7.237 μm.

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.

Reductive atmospheric acid leaching of spent alkaline batteries in H_2SO_4/Na_2SO_3 solutions

This work studies the optimum reductive leaching process for manganese and zinc recovery from spent alkaline battery paste. The effects of reducing agents, acid concentration, pulp density, reaction temperature, and leaching time on the dissolution of manganese and zinc were investigated in detail. Manganese dissolution by reductive acidic media is an intermediate-controlled process with an activation energy of 12.28 kJ＇mo1-1. After being leached, manganese and zinc were selectively precipitated with sodium hydroxide. The zinc was entirely con- verted into zincate （Zn（OH）42-） ions and thus did not co-precipitate with manganese hydroxide during this treatment （2.0 M NaOH, 90 min, 200 r/rain, pH 〉 13）. After the manganese was removed from the solution, the Zn（OH）4^2- was precipitated as zinc sulfate in the presence of sulfuric acid. The results indicated that this process could be effective in recovering manganese and zinc from alkaline batteries.

Effects of temperature and concentration of sulfuric acid on the electrodeposition of grainy electrolytic manganese dioxide

The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of electrodeposition and the particle size of grainy electrolytic manganese dioxide （EMD） were investigated. The structure, particle size and appearance of grainy EMD were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficiency decrease. With the increase of electrolysis temperature in the range of 30-60℃, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30℃ and concentration of sulfuric acid of 2.5 mol/L for electrodeposition of the grainy EMD were obtained. XRD patterns show that the grainy EMD electrodeposited under the optimum conditions consists of γ-MnO2 and has an orthorhombic lattice structure. According to the results of SEM, the grainy EMD has a spherical or sphere-like appearance and a narrow particle size distribution with an average size of about 7μm. The grainy EMD is a promising cathode of rechargeable alkaline batteries for high energy density and a prospective precursor for production of the LiMn2O4 cathode of lithium ion batteries.