Polymer engineering for electrodes of aqueous zinc ion batteries

With the increasing demand for scalable and cost-effective electrochemical energy storage,aqueous zinc ion batteries(AZIBs)have a broad application prospect as an inexpensive,efficient,and naturally secure energy storage device.However,the limitations suffered by AZIBs,including volume expansion and active materials dissolution of the cathode,electrochemical corrosion,irreversible side reactions,zinc dendrites of the anode,have seriously decelerated the civilianization process of AZIBs.Currently,polymers have tremendous superiority for application in AZIBs attributed to their exceptional chemical stability,tunable structure,high energy density and outstanding mechanical properties.Considering the expanding applications of AZIBs and the superiority of polymers,this comprehensive paper meticulously reviews the benefits of utilizing polymeric applied to cathodes and anodes,respectively.To begin with,with adjustable structure as an entry point,the correlation between polymer structure and the function of energy storage as well as optimization is deeply investigated in respect to the mechanism.Then,depending on the diversity of properties and structures,the development of polymers in AZIBs is summarized,including conductive polymers,redox polymers as well as carbon composite polymers for cathode and polyvinylidene fluoride-,carbonyl-,amino-,nitrile-based polymers for anode,and a comprehensive evaluation of the shortcomings of these strategies is provided.Finally,an outlook highlights some of the challenges posed by the application of polymers and offers insights into the potential future direction of polymers in AZIBs.It is designed to provide a thorough reference for researchers and developers working on polymer for AZIBs.

A Mixed Ether Electrolyte for Lithium Metal Anode Protection in Working Lithium-Sulfur Batteries

Lithium-sulfur(Li-S) battery is considered as a promising energy storage system to realize high energy density.Nevertheless,unstable lithium metal anode emerges as the bottleneck toward practical applications,especially with limited anode excess required in a working full cell.In this contribution,a mixed diisopropyl ether-based(mixed-DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li-S batteries with sulfurized polyacrylonitrile(SPAN) cathodes.The mixed-DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides,rendering significantly improved cycling stability.Concretely,Li | Cu half-cells with the mixed-DIPE electrolyte cycled stably for 120 cycles,which is nearly five times longer than that with routine carbonate-based electrolyte.Moreover,the mixedDIPE electrolyte contributed to a doubled life span of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte.This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high-energy-density Li-S batteries.

Towards full demonstration of high areal loading sulfur cathode in lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability.The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density.However,the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases.Herein,we used diameters of 5.0(D5)and 13.0(D13)mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading(4.5 mg cm^-2).The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large(D13)cathode.Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions,which results in inferior battery performance of the Li–S cell with large diameter cathode.This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading,carbon modified separators,organic electrolyte,and Li metal anode in a pouch cell,wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.

Carbon-Nitride-Based Materials for Advanced Lithium-Sulfur Batteries

Lithium-sulfur(Li-S)batteries are promising candidates for next-generation energy storage systems owing to their high energy density and low cost.However,critical challenges including severe shuttling of lithium polysulfides(LiPSs)and sluggish redox kinetics limit the practical application of Li-S batteries.Carbon nitrides(C_(x)N_(y)),represented by graphitic carbon nitride(g-C_(3)N_(4)),provide new opportunities for overcoming these challenges.With a graphene-like structure and high pyridinic-N content,g-C_(3)N_(4) can effectively immobilize LiPSs and enhance the redox kinetics of S species.In addition,its structure and properties including electronic conductivity and catalytic activity can be regulated by simple methods that facilitate its application in Li-S batteries.Here,the recent progress of applying C_(x)N_(y)-based materials including the optimized g-C_(3)N_(4),g-C_(3)N_(4)-based composites,and other novel C_(x)N_(y) materials is systematically reviewed in Li-S batteries,with a focus on the structure-activity relationship.The limitations of existing C_(x)N_(y)-based materials are identified,and the perspectives on the rational design of advanced C_(x)N_(y)-based materials are provided for high-performance Li-S batteries.

Functional lithiophilic polymer modified separator for dendrite-free and pulverization-free lithium metal batteries

Severe performance drop and fire risk due to the uneven lithium(Li) dendrite formation and growth during charge/discharge process has been considered as the major obstacle to the practical application of Li metal batteries.So inhibiting dendrite growth and producing a stable and robust solid electrolyte interface(SEI) layer are essential to enable the use of Li metal anodes.In this work,a functional lithiophilic polymer composed of chitosan(CTS),polyethylene oxide(PEO),and poly(triethylene glycol dimethacrylate)(PTEGDMA),was homogeneously deposited on a commercial Celgard separator by combining electrospraying and polymer photopolymerization techniques.The lithiophilic environment offered by the CTS-PEO-PTEGDMA layer enables uniform Li deposition and facilitates the formation of a robust homogeneous SEI layer,thus prevent the formation and growth of Li dendrites.As a result,both Li/Li symmetric cells and LiFePO4/Li full cells deliver significantly enhanced electrochemical performance and cycle life.Even after 1000 cycles,the specific capacity of the modified full cell could be maintained at65.8 mAh g^(-1), twice which of the unmodified cell(32.8 mAh g^(-1)).The long-term cycling stability in Li/Li symmetric cells,dendrite-free anodes in SEM images and XPS analysis suggest that the pulverization of the Li anode was effectively suppressed by the lithiophilic polymer layer.

MXenes for metal-ion and metal-sulfur batteries:Synthesis,properties,and electrochemistry

In 2011,a new class of 2D materials was discovered;after 2012,they began to be concerned;in 2017,the“gold rush”of the materials was triggered,and they are exactly MXenes.2D MXenes,a new class of transition metal carbides,carbonitrides and nitrides,have become the star and cutting-edge research materials in the field of emerging batteries systems due to their unique 2D structure,abundant surface chemistry,and excellent physical and electrochemical properties.This review focuses on the MXene materials and summarizes the recent advancements in the synthesis techniques and properties,in addition to a detailed discussion on the electrochemical energy storage applications,including alkali-ion(Li^(+),Na^(+),K^(+))storage,lithium-sulfur(Li–S)batteries,sodiumsulfur(Na–S)batteries,and metal anode protection.Special attentions are given to the elaborate design of nano-micro structures of MXenes for the various roles as electrodes,multifunctional components,S hosts,modified separators,and metal anode protective layers.The paper ends with a prospective summary of the promising research directions in terms of synthesis,structure,properties,analysis,and production on MXene materials.

Research Progress and Future Perspectives on Rechargeable Na-O_(2) and Na-CO_(2) Batteries

Rechargeable sodium–oxygen(Na-O_(2))and sodium–carbon dioxide(Na-CO_(2))batteries have attracted intensive research attention in recent years owing to their advantages of high theoretical energy density,modest cost,abundance of sodium resources,and promising potential for achieving real sodium–air batteries in large-scale energy storage systems.Nevertheless,current research on Na-O_(2)and Na-CO_(2)batteries is facing enormous challenges,such as low energy efficiency and limited cycle life,which are restricting their progress at the initial stage.Therefore,understanding their working principles,and the chemical and electrochemical reactions of the electrodes is indispensable to achieve their practical application and even the goal of true sodium–air batteries.This review aims to provide an overview of the research developments and future perspectives on Na-O_(2)and Na-CO_(2)batteries,which include the major aspects,such as working mechanisms,air cathode materials design strategies,sodium anode protection,and electrolyte stability.Moreover,the remaining issues and future research directions are also thoroughly discussed and presented.

Facile construction of a water-defendable Li anode protection enables rechargeable Li-O_(2) battery operating in humid atmosphere

The rechargeable Li-O_(2) battery endowed with high theoretical specific energy density has sparked intense research interest as a promising energy storage system. However, the intrinsic high activity of Li anode,especially to moisture, usually leads to inferior electrochemical performance of Li-O_(2) battery in humid environments, hindering its widespread application. To settle the trouble of poor moisture tolerance, fabricating a water-proof layer on the Li-metal anode could be an effective tactic. Herein, a facile strategy for constructing an ibuprofen-based protective layer on the Li anode has been proposed to realize highly rechargeable Li-O_(2) battery in humid atmosphere. Due to the in-situ reaction between ibuprofen reagent and metallic Li, the protective layer with a thickness of ~30 μm has been uniformly deposited on the surface of Li anode. Particularly, the protective layer, consisting of a large amount of hydrophobic alkyl group and benzene ring, can significantly resist water ingress and enhance the electrochemical stability of Li anode. As a result, the Li-O_(2) battery based on the protected Li anode achieves a long cycle life of 210 h(21 cycles at 1000 m Ah/g, 200 m A/g) in highly moist atmosphere with relative humidity(RH) of68%. This convenient and efficient strategy offers novel design concept of water-resistant metal anode,and paves the way to the promising future prospect for the high-energy Li-O_(2) battery implementing in the ambient atmosphere.

Revealing the importance of suppressing formation of lithium hydride and hydrogen in Li anode protection

The reviving of the“Holy Grail”lithium metal batteries(LMBs)is greatly hindered by severe parasitic reactions between Li anode and electrolytes.Herein,first,we comprehensively summarize the failure mechanisms and protection principles of the Li anode.Wherein,despite being in dispute,the formation of lithium hydride(LiH)is demonstrated to be one of the most critical factors for Li anode pulverization.Secondly,we trace the research history of LiH at electrodes of lithium batteries.In LMBs,LiH formation is suggested to be greatly associated with the generation of H_(2)from Li/electrolyte intrinsic parasitic reactions,and these intrinsic reactions are still not fully understood.Finally,density functional theory calculations reveal that H_(2)adsorption ability of representative Li anode protective species(such as LiF,Li_(3)N,BN,Li_(2)O,and graphene)is much higher than that of Li and LiH.Therefore,as an important supplement of well-known lithiophilicity theory/high interfacial energy theory and three key principles(mechanical stability,uniform ion transport,and chemical passivation),we propose that constructing an artificial solid electrolyte interphase layer enriched of components with much higher H_(2)adsorption ability than Li will serve as an effective principle for Li anode protection.In summary,suppressing formation of LiH and H_(2)will be very important for cycle life enhancement of practical LMBs.

Progress and challenges of electrolyte modulation in aqueous zinc-ion batteries

As a new type of green battery system,aqueous zinc-ion batteries(AZIBs)have gradually become a research hotspot due to their low cost,high safety,excellent stability,high theoretical capacity(820 mAh·g^(-1))of zinc anode,and low redox potential(-0.76 V vs.standard hydrogen electrode(SHE)).AZIBs have been expected to be an alternative to lithium-ion batteries for large-scale commercial energy storage applications.Unfortunately,they are facing thorny issues such as degradation of cycling performance,zinc dendrites,and side reactions.At the same time,these problems cause short cycling life of batteries,thus severely limiting their commercial application.In recent years,many more researches have been conducted on the modification of anode and cathode materials of AZIBs,but there is a lack of in-depth discussion on the characteristics and mechanism of electrolyte additives.In this review,we will make a systematic summary of the current problems with two electrodes in AZIBs,as well as the types and functions of electrolyte additives.Moreover,we further systematically describe the modulation mechanism of electrolyte additives in the performance of the cathode and anode.The prospects and development directions of additive modulation strategies for AZIBs electrolytes are prospected.

Li-air batteries:air stability of lithium metal anodes

Aprotic rechargeable lithium-air batteries(LABs)with an ultrahigh theoretical energy density(3,500 Wh kg^(-1))are known as the‘holy grail’of energy storage systems and could replace Li-ion batteries as the next-generation high-capacity batteries if a practical device could be realized.However,only a few researches focus on the battery performance and reactions in the ambient air environment,which is a major obstacle to promote the practical application of LABs.Here,we have summarized the recent research progress on LABs,especially with respect to the Li metal anodes.The chemical and electrochemical deteriorations of the Li metal anode under the ambient air are discussed in detail,and the parasitic reactions involving the cathode and electrolyte during the charge-discharge processes are included.We also provide stability perspectives on protecting the Li metal anodes and propose design principles for realizing high-performance LABs.

Hybrid electrolyte with robust garnet-ceramic electrolyte for lithium anode protection in lithium-oxygen batteries

Rechargeable lithium-oxygen （Li-O2） batteries have received intensive research interest due to its ultrahigh energy density, while its cycle stability is still hindered by the high reactivity of the Li anode with oxygen and moisture. To alleviate the corrosion of the metallic lithium anodes for achieving a stable Li-O2 battery, and as a proof-of-concept experiment, a distinctive hybrid electrolyte system with an organic/ceramic/organic electrolyte （OCOE） architecture is designed. Importantl~ the cycle number of Li-O2 batteries with OCOE is significantly improved compared with batteries with an organic electrolyte （OE）. This might be attributed to the effective suppression of the lithium anode corrosion caused by the OE degradation and the crossover of oxygen from the cathode. We consider that our facile, low-cost, and highly effective lithium protection strategy presents a new avenue to address the daunting corrosion problem of lithium metal anodes in Li-O2 batteries. In addition, the proposed strategy can be easily extended to other metal-O2 battery systems, such as Na-O2 batteries.

Development prospects of metal-based two-dimensional nanomaterials in lithium-sulfur batteries

A lithium-sulfur(Li-S)system is an important candidate for future lithium-ion system due to its low cost and high specific theoretical capacity(1675 m Ah/g,2600 Wh/kg),which is greatly hindered by the poor conductivity of sulfur,large volume change and dissolution of lithium polysulfides.Two-dimensional(2D)materials with monolayers or few-layers usually have peculiar structures and physical/chemical properties,which can resolve the critical issues in Li-S batteries.Especially,the metal-based 2D nanomaterials,including ferrum,cobalt or other metal-based composites with various anions,can provide high conductivity,large surface area and abundant reaction sites for restraining the diffusion for lithium polysulfides.In this mini-review,we will present an overview of recent developments on metal-based 2D nanomaterials with various anions as the electrode materials for Li-S batteries.Since the main bottleneck for the Li-S system is the shuttle of polysulfides,emphasis is placed on the structure and components,physical/chemical interaction and interaction mechanisms of the 2D materials.Finally,the challenges and prospects of metal-based 2D nanomaterials for Li-S batteries are discussed and proposed.

Superior plating/stripping performance through constructing an artificial interphase layer on metallic Mg anode

Rechargeable magnesium batteries(RMBs)have attracted tremendous attention in energy storage ap-plications in term of high abundance,high specific capacity and remarkable safety of metallic magne-sium(Mg)anode.However,a serious passivation of Mg anode in the conventional electrolytes leads to extremely poor plating/stripping performance,further hindering its applications.Herein,we propose a convenient method to construct an artificial interphase layer on Mg anode by substitution and alloy-ing reactions between SbCl_(3) and Mg.This Sb-based artificial interphase layer containing mainly MgCl_(2) and Mg_(3) Sb_(2) endows the significantly improved interfacial kinetics and electrochemical performance of Mg anode.The overpotential of Mg plating/stripping in conventional Mg(TFSI)2/DME electrolytes is vastly reduced from over 2 V to 0.25-0.3 V.Combining experiments and calculations,we demonstrate that un-der the uniform distribution of MgCl_(2) and Mg_(3) Sb_(2),an electric field with a favorable potential gradient is formed on the anode surface,which enables swift Mg^(2+)migration.Meanwhile,this layer can inhibit the decomposition of electrolytes to protect anode.This work provides an in-depth exploration of the artificial solid-electrolyte interface(SEI)construction,and a more achievable and safe path to realize the application of metallic Mg anode in RMBs.

A diluent protective organic additive electrolyte of hydrophilic hyperbranched polyester for long-life reversible aqueous zinc manganese oxide batteries

hydrophilic hyperbranched polyester(poly(tetramethylol acetylenediurea(TA)-CO-succinyl chloride)(PTS))was proposed to be used as an organic additive in aqueous ZnSO_(4)electrolyte to achieve a highly reversible zinc/manganese oxide battery.It is found that the zinc symmetric battery based on the 2.0 wt.%PTS/ZnSO_(4)electrolyte showed a long cycle stability of more than 2400 h at 1.0 mA·cm^(-2),which is much longer than that including the blank ZnSO_(4)electrolyte(140 h).Furthermore,the capacity retention of the Zn||MnO_(2)full cells employing the 2.0 wt.%PTS/ZnSO_(4)electrolyte remained 85%after 100 cycles at 0.2 A·g^(1),which is much higher than 20%capacity retention of the cell containing the blank ZnSO_(4)electrolyte,and also greater than 59.6%capacity retention of the cell including the 10.0 wt.%TA/ZnSO_(4)electrolyte.By using 2.0 wt.%PTS/ZnSO_(4)electrolytes,the capacity retention of the Zn||MnO_(2)full cells even reached 65%after 2000 cycles at a higher current density of 1.0 A·g^(1).It is further demonstrated that the PTS was firmly adsorbed on the zinc anode surface to form a protective layer.

Inhibition of Zinc Corrosion by Fucoidan in Natural Sea water

Research on corrosion behaviour of zinc in natural sea water without and with fucoidan was carried out by potentiodynamic polarisation test and electrochemical impedance spectroscopy （EIS）. The results revealed that fucoidan serves as a good inhibitor for zinc in sea water. Polarisation curves suggested that corrosion potential values shifted to the positive ones after adding inhibitor and fucoidan retards anodic reaction more. Thus, fucoidan can be acted as anodic inhibitor. EIS results showed two phenomena including a charge transfer and an adsorption film. The corrosion inhibition of fucoidan was further confirmed by the scanning electron microscope （SEM） and atomic force microscope （AFM） analysis. Langmuir＇s adsorption isotherm was found the appropriate adsorption model.

Electrolytes enriched by potassium perfluorinated sulfonates for lithium metal batteries

Lithium(Li) metal is widely considered as a promising anode for next-generation lithium metal batteries(LMBs) due to its high theoretical capacity and lowest electrochemical potential. However, the uncontrollable formation of Li dendrites has prevented its practical application. Herein, we propose a kind of multifunctional electrolyte additives(potassium perfluorinated sulfonates) from the multi-factor principle for electrolyte additive molecular design(EDMD) view to suppress the Li dendrite growth. The effects of these additives are revealed through experimental results, molecular dynamics simulations and firstprinciples calculations. Firstly, K^(+)can form an electrostatic shield on the surface of Li anode to prevent the growth of Li dendrites. Secondly, potassium perfluorinated sulfonates can improve the activity of electrolytes as co-conductive salts, and lower the electro-potential of Li nucleation. Thirdly, perfluorinated sulfonate anions not only can change the Li^(+)solvation sheath structure to decrease the desolvation energy barrier and increase the ion migration rate, but also can be partly decomposed to form the superior solid electrolyte interphase(SEI). Benefited from the synergistic effects, an outstanding cycle life over250 h at 1 m A cm^(-2) is achieved in symmetric Li||Li cells. In particular, potassium perfluorinated sulfonate additives(e.g., potassium perfluorohexyl sulfonate, denoted as K+PFHS) can also contribute to the formation of high-quality cathode electrolyte interphase(CEI). As a result, Li||LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2) full cells exhibit significantly enhanced cycling stability. This multi-factor principle for EDMD offers a unique insight on understanding the electrochemical behavior of ion-type electrolyte additives on both the Li metal anode and high-voltage cathode.

Comprehensive review on zinc-ion battery anode: Challenges and strategies

Zinc-ion batteries(ZIBs)have been extensively investigated and discussed as promising energy storage devices in recent years owing to their low cost,high energy density,inherent safety,and low environmental impact.Nevertheless,several challenges remain that need to be prioritized before realizing the wide-spread application of ZIBs.In particular,the development of zinc anodes has been hindered by many challenges,such as inevitable zinc dendrites,corrosion passivation,and the hydrogen evolution reaction(HER),which have severely limited the practical application of high-performance ZIBs.This review starts with a systematic discussion of the origins of zinc dendrites,corrosion passiv-ation,and the HER,as well as their effects on battery performance.Subse-quently,we discuss solutions to the above problems to protect the zinc anode,including the improvement of zinc anode materials,modification of the anode–electrolyte interface,and optimization of the electrolyte.In particular,this review emphasizes design strategies to protect zinc anodes from an inte-grated perspective with broad interest rather than a view with limited focus.In the final section,comments and perspectives are provided for the future design of high-performance zinc anodes.

Efforts towards Practical and Sustainable Li/Na-Air Batteries

The Li-O_(2) batteries have ttrcted much attention due to their parallel theoretical energy density to gaso-line.In the past 20 years,understanding and knowledge in Li-O_(2) battlry have greatly deepened in elucidat-ing the relationship between structure and performance.Our group has been focusing on the cathode en-gineering and anode protection strategy development in the past years,trying to make full use of the supe-riority of metal-air batteries towards applications.In this review,we aim to retrospect our efforts in devel-oping practical,sustainable metal-air batteries.We will first introduce the basic working principle of Li-O_(2) batteries and our progresses in L-O_(2) batteries with typical cathode designs and anode protection strategies,which have together promoted the large capacity,long life and low charge overpotential.We emphasize the designing art of carbon-based cathodes in this part along with a short talk on all-metal cathodes.The fol-lowing part is our research in Na-O2 batteries including both cathode and anode optimizations.The differ-ences between Li-O2 and Na-O2 batteries are also briefly discussed.Subsequently,our proof-of-concept work on Li-N2 battery,a new energy storage system and chemistry,is discussed with detailed information on the discharge product identifcation.Finally,we summarize our designed models and prototypes of flex-ible metal-air batteries that are promising to be used in flexible devices to deliver more power.