Strategies for Dendrite‐Free Anode in Aqueous Rechargeable Zinc Ion Batteries

Ongoing interest is focused on aqueous zinc ion batteries (ZIBs) for mass‐production energy storage systems as a result of their affordability, safety, and high energy density. Ensuring the stability of the electrode/electrolyte interface is of particular importance for prolonging the cycling ability to meet the practical requirements of rechargeable batteries. Zinc anodes exhibit poor cycle life and low coulombic efficiency, stemming from the severe dendrite growth, and irreversible byproducts such as H₂ and inactive ZnO. Great efforts have recently been devoted to zinc anode protection for designing high‐performance ZIBs. However, the intrinsic origins of zinc plating/striping are poorly understood, which greatly delay its potential applications. Rather than focusing on battery metrics, this review delves deeply into the underlying science that triggers the deposition/dissolution of zinc ions. Furthermore, recent advances in modulating the zinc coordination environment, uniforming interfacial electric fields, and inducing zinc deposition are highlighted and summarized. Finally, perspectives and suggestions are provided for designing highly stable zinc anodes for the industrialization of the aqueous rechargeable ZIBs in the near future.     

Nanostructured p‐n Junctions for Kinetic‐to‐Electrical Energy Conversion

Piezoelectric ZnO nanorods grown on a flexible substrate are combined with the p‐type semiconducting polymer PEDOT:PSS to produce a p‐n junction device that successfully demonstrates kinetic‐to‐electrical energy conversion. Both the voltage and current output of the devices are measured to be in the range of 10 mV and 10 μA cm^?2. Combining these figures for the best device gives a maximum possible power density of 0.4 mW cm^?3. Systematic testing of the devices is performed showing that the voltage output increases linearly with applied stress, and is reduced significantly by illumination with super‐band gap light. This provides strong evidence that the voltage output results from piezoelectric effects in the ZnO. The behavior of the devices is explained by considering the time‐dependent changes in band structure resulting from the straining of a piezoelectric material within a p‐n junction. It is shown that the rate of screening of the depolarisation field determines the power output of a piezoelectric energy harvesting device. This model is consistent with the behavior of a number of previous devices utilising the piezoelectric effect in ZnO.     

Zinc‐Induced Hyperleptinemia Relates to the Amelioration of Sucrose‐Induced Obesity with Zinc Repletion

Objective: Dietary zinc repletion can ameliorate sucrose‐induced obesity. A positive correlation between zinc and leptin has been recently noted, and both are known as important mediators in appetite control. In this study, we examined whether the reported amelioration of sucrose‐induced obesity by zinc repletion was consequent on the changes in circulating leptin levels. Research Methods and Procedures: Mice with obesity that was induced by giving a 32% sucrose solution in addition to a semipurified diet were divided into two groups based on whether they had 20 mg/liter zinc supplementation in their drinking water. Results: As expected, the mice with sucrose‐induced obesity had hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hyperleptinemia, and hypozincemia when compared with the mice given the diet alone. Body weight gain, body fat content, and food and sucrose intake tended to decrease but not with statistical significance in sucrose‐fed obese mice with zinc supplementation. Nevertheless, some serum variables (glucose, insulin, triglycerides, and zinc) in sucrose‐fed obese mice with zinc treatment were approximate to those values of the mice given the diet alone. Moreover, sucrose‐fed obese mice with zinc supplementation had the highest serum values of leptin. Discussion: This study indicates that the amelioration of sucrose‐induced obesity by zinc repletion may be partly attributable to the hyperleptinemia induced by the mineral.     

Concomitant disorder and high‐affinity zinc binding in the human zinc‐ and iron‐regulated transport protein 4 intracellular loop

The human zinc‐ and iron‐regulated transport protein 4 (hZIP4) protein is the major plasma membrane protein responsible for the uptake of zinc in the body, and as such it plays a key role in cellular zinc homeostasis. hZIP4 plasma membrane levels are regulated through post‐translational modification of its large, disordered, histidine‐rich cytosolic loop (ICL2) in response to intracellular zinc concentrations. Here, structural characteristics of the isolated disordered loop region, both in the absence and presence of zinc, were investigated using nuclear magnetic resonance (NMR) spectroscopy. NMR chemical shifts, coupling constants and temperature coefficients of the apoprotein, are consistent with a random coil with minor propensities for transient polyproline Type II helices and β‐strand in regions implicated in post‐translational modifications. The ICL2 protein remains disordered upon zinc binding, which induces exchange broadening. Paramagnetic relaxation enhancement experiments reveal that the histidine‐rich region in the apoprotein makes transient tertiary contacts with predicted post‐translational modification sites. The residue‐specific data presented here strengthen the relationship between hZIP4 post‐translational modifications, which impact its role in cellular zinc homeostasis, and zinc sensing by the intracellular loop. Furthermore, the zinc sensing mechanism employed by the ICL2 protein demonstrates that high‐affinity interactions can occur in the presence of conformational disorder.     

Recent Advances in Vanadium‐Based Aqueous Rechargeable Zinc‐Ion Batteries

Aqueous zinc‐ion batteries (AZIBs) have attracted considerable attention as promising next‐generation power sources because of the abundance, low cost, eco‐friendliness, and high security of Zn resources. Recently, vanadium‐based materials as cathodes in AZIBs have gained interest owing to their rich electrochemical interaction with Zn²⁺ and high theoretical capacity. However, existing AZIBs are still far from meeting commercial requirements. This article summarizes recent advances in the rational design of vanadium‐based materials toward AZIBs. In particular, it highlights various tactics that have been reported to increase the intercalation space, structural stability, and the diffusion ability of the guest Zn²⁺, as well as explores the structure‐dependent electrochemical performance and the corresponding energy storage mechanism. Furthermore, this article summarizes recent achievements in the optimization of aqueous electrolytes and Zn anodes to resolve the issues that remain with Zn anodes, including dendrite formation, passivation, corrosion, and the low coulombic efficiency of plating/stripping. The rationalization of these research findings can guide further investigations in the design of cathode/anode materials and electrolytes for next‐generation AZIBs.     

‘Turn‐on’ fluorescent chemosensors based on naphthaldehyde‐2‐pyridinehydrazone compounds for the detection of zinc ion in water at neutral pH

A series of naphthaldehyde‐2‐pyridinehydrazone derivatives were discovered to display interesting ‘turn‐on’ fluorescence response to Zn²⁺ in 99% water/DMSO (v/v) at pH 7.0. Mechanism study indicated that different substituent groups in the naphthaldehyde moiety exhibited significant influence on the detection of Zn²⁺. The electron rich group resulted in longer fluorescence wavelengths but smaller fluorescence enhancement for Zn²⁺. Among these compounds, 1 showed the highest fluorescence enhancement of 19‐fold with the lowest detection limit of 0.17 μmol/L toward Zn²⁺. The corresponding linear range was at least from 0.6 to 6.0 μmol/L. Significantly, 1 showed an excellent selectivity toward Zn²⁺ over other metal ions including Cd²⁺.     

Phosphorene as Cathode Material for High‐Voltage,Anti‐Self‐Discharge Zinc Ion Hybrid Capacitors

Output voltage and self‐discharge rate are two important performance indices for supercapacitors, which have long been overlooked, though these play a very significant role in their practical application. Here, a zinc anode is used to construct a zinc ion hybrid capacitor. Expanded operating voltage of the hybrid capacitor is obtained with novel electrolytes. In addition, significantly improved anti‐self‐discharge ability is achieved. The phosphorene‐based zinc ion capacitor exploiting a “water in salt” electrolyte with a working potential can reach 2.2 V, delivering 214.3 F g^?1 after 5000 cycles. The operating voltage is further extended to 2.5 V through the use of an organic solvent as the electrolyte; the solvent is prepared by adding 0.2 m ZnCl₂ into the tetraethylammonium tetrafluoroborate in propylene carbonate (Et₄NBF₄/PC) solvent, and it exhibits 105.9 F g^?1 even after 9500 cycles. More importantly, the phosphorene‐based capacitors possess excellent anti‐self‐discharge performance. The capacitors retain 76.16% of capacitance after resting for 300 h. The practical application of the zinc ion capacitor is demonstrated through a flexible paper‐based printed microcapacitor. It is believed that the developed zinc ion capacitor can effectively resolve the severe self‐discharge problem of supercapacitors. Moreover, high‐voltage zinc ion capacitors provide more opportunities for the application of supercapacitors.     

High‐Performance Reversible Aqueous Zn‐Ion Battery Based on Porous MnOx Nanorods Coated by MOF‐Derived N‐Doped Carbon

Rechargeable aqueous zinc‐ion batteries (ZIBs) have been emerging as potential large‐scale energy storage devices due to their high energy density, low cost, high safety, and environmental friendliness. However, the commonly used cathode materials in ZIBs exhibit poor electrochemical performance, such as significant capacity fading during long‐term cycling and poor performance at high current rates, which significantly hinder the further development of ZIBs. Herein, a new and highly reversible Mn‐based cathode material with porous framework and N‐doping (MnO_x@N‐C) is prepared through a metal–organic framework template strategy. Benefiting from the unique porous structure, conductive carbon network, and the synergetic effect of Zn²⁺ and Mn²⁺ in electrolyte, the MnO_x@N‐C shows excellent cycling stability, good rate performance, and high reversibility for aqueous ZIBs. Specifically, it exhibits high capacity of 305 mAh g^?1 after 600 cycles at 500 mA g^?1 and maintains achievable capacity of 100 mAh g^?1 at a quite high rate of 2000 mA g^?1 with long‐term cycling of up to 1600 cycles, which are superior to most reported ZIB cathode materials. Furthermore, insight into the Zn‐storage mechanism in MnO_x@N‐C is systematically studied and discussed via multiple analytical methods. This study opens new opportunities for designing low‐cost and high‐performance rechargeable aqueous ZIBs.     

Recent Advances in Flexible Zinc‐Based Rechargeable Batteries

Flexible Zn‐based batteries are regarded as promising alternatives to flexible lithium‐ion batteries for wearable electronics owing to the natural advantages of zinc, such as environmental friendliness and low cost. In the past few years, flexible Zn‐based batteries have been studied intensively and exciting achievements have been obtained in this field. However, the development of flexible Zn‐based batteries is still at an early stage. The challenges of developing flexible lithium‐ion batteries are presented here. Then, a brief overview of recent progress in flexible zinc secondary batteries from the perspective of advanced materials and some issues that remain to be addressed are discussed.     

Structure of the zinc‐bound amino‐terminal domain of the NMDA receptor NR2B subunit

N‐methyl‐D ‐aspartate (NMDA) receptors belong to the family of ionotropic glutamate receptors (iGluRs) that mediate the majority of fast excitatory synaptic transmission in the mammalian brain. One of the hallmarks for the function of NMDA receptors is that their ion channel activity is allosterically regulated by binding of modulator compounds to the extracellular amino‐terminal domain (ATD) distinct from the L ‐glutamate‐binding domain. The molecular basis for the ATD‐mediated allosteric regulation has been enigmatic because of a complete lack of structural information on NMDA receptor ATDs. Here, we report the crystal structures of ATD from the NR2B NMDA receptor subunit in the zinc‐free and zinc‐bound states. The structures reveal the overall clamshell‐like architecture distinct from the non‐NMDA receptor ATDs and molecular determinants for the zinc‐binding site, ion‐binding sites, and the architecture of the putative phenylethanolamine‐binding site.     

Defect Engineering in Manganese‐Based Oxides for Aqueous Rechargeable Zinc‐Ion Batteries: A Review

The development of advanced cathode materials for aqueous the zinc ion battery (ZIB) represents a crucial step toward building future large‐scale green energy conversion and storage systems. Recently, significant progress has been achieved in the development of manganese‐based oxides for ZIB via defect engineering, whereby the intrinsic capacity and energy density have been enhanced. In this review, an overview of the recent progress in the defect engineering of manganese‐based oxides for aqueous ZIBs is summarized in the following order: 1) the structures and properties of the commonly used manganese‐based oxides, 2) the classification of the various types of defect engineering commonly reported, 3) the various strategies used to create defects in materials, and 4) the effects of the various types of defect engineering on the electrochemical performance of manganese‐based oxides. Finally, a perspective on the defect engineering of manganese‐based oxides is proposed to further enhance their electrochemical performance as a ZIB cathode.     

Pseudo‐Zn–Air and Zn‐Ion Intercalation Dual Mechanisms to Realize High‐Areal Capacitance and Long‐Life Energy Storage in Aqueous Zn Battery

Aqueous zinc batteries are considered as promising alternatives to lithium ion batteries owing to their low cost and high safety. However, the developments of state‐of‐the‐art zinc‐ion batteries (ZIB) and zinc–air batteries (ZAB) are limited by the unsatisfied capacities and poor cycling stabilities, respectively. It is of significance in utilizing the long‐cycle life of ZIB and high capacity of ZAB to exploit advanced energy storage systems. Herein, a bulk composite of graphene oxide and vanadium oxide (V₅O₁₂·6H₂O) as cathode material for aqueous Zn batteries in a mild electrolyte is employed. The battery performance is demonstrated to arise from a combination of the reversible cations insertion/extraction in vanadium oxide and especially the electrochemical redox reactions on the surface functional groups of graphene oxide (named as pseudo‐Zn–air mechanism). Along with adjusting the hydroxyl content on the surface of graphene oxide, the specific capacity is significantly increased from 342 mAh g^?1 to a maximum of 496 mAh g^?1 at 100 mA g^?1. The surface‐controlled kinetics occurring in the bulk composite ensure a high areal capacity of 10.6 mAh cm^?2 at a mass loading of 26.5 mg cm^?2, and a capacity retention of 84.7% over 10 000 cycles at a high current density of 10 A g^?1.     

Folding in solution of the C‐catalytic protein fragment of angiotensin‐converting enzyme

Angiotensin‐converting enzyme (ACE) is a key molecule of the renin–angiotensin–aldosterone system which is responsible for the control of blood pressure. For over 30 years it has become the target for fighting off hypertension. Many inhibitors of the enzyme have been synthesized and used widely in medicine despite the lack of ACE structure. The last 5 years the crystal structure of ACE separate domains has been revealed, but in order to understand how the enzyme works it is necessary to study its structure in solution. We present here the cloning, overexpression in Escherichia coli, purification and structural study of the Ala₉₅₉ to Ser₁₀₆₆ region (ACE_C) that corresponds to the C‐catalytic domain of human somatic angiotensin‐I‐converting enzyme. ACE_C was purified under denatured conditions and the yield was 6 mg/l of culture. Circular dichroism (CD) spectroscopy indicated that 1,1,1‐trifluoroethanol (TFE) is necessary for the correct folding of the protein fragment. The described procedure can be used for the production of an isotopically labelled ACE_959–1066 protein fragment in order to study its structure in solution by NMR spectroscopy. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.     

Metal‐Organic Framework Integrated Anodes for Aqueous Zinc‐Ion Batteries

Zinc‐based batteries have a high capacity and are safe, cost‐effective, environmentally‐friendly, and capable of scalable production. However, dendrite formation and poor reversibility hinder their performance. Metal‐organic framework (MOF)‐based Zn anodes are made by wet chemistry to address these issues. These MOF‐based anodes exhibit high efficiency during Zn plating‐stripping and prevent dendrite formation, as shown by ex situ SEM analysis. The practicality of the MOF‐based anodes is demonstrated in aqueous Zn ion batteries, which show improved performance including specific capacity, cycle life, and safety relative to the pristine Zn anode due to their hydrophilic and porous surface. These results, along with the easy scalability of the process, demonstrate the high potential of MOF‐modified Zn anodes for use in dendrite‐free, higher‐performance, Zn‐based energy storage systems.     

Asymmetric Zinc‐Catalyzed Hydrosilylation of Ketones and the Effect of Carboxylate on the Enantioselectivity

Several chiral ligands containing (R,R)‐diaminocyclohexane moieties and pyrrole, furan, or benzene have been synthesized. These ligands were tested in enantioselective zinc‐catalyzed hydrosilylation reactions; excellent enantioselectivities were obtained when the ligands containing (R,R)‐diaminocyclohexane moieties and furan rings were used. For comparison, zinc chloride combined with different potassium carboxylate salts and ligands were also tested for catalytic hydrosilylation reactions. Chirality 25:275–280, 2013. © 2013 Wiley Periodicals, Inc.     

A Flexible Solid‐State Aqueous Zinc Hybrid Battery with Flat and High‐Voltage Discharge Plateau

The migration of zinc‐ion batteries from alkaline electrolyte to neutral or mild acidic electrolyte promotes research into their flexible applications. However, discharge voltage of many reported zinc‐ion batteries is far from satisfactory. On one hand, the battery voltage is substantially restricted by the narrow voltage window of aqueous electrolytes. On the other hand, many batteries yield a low‐voltage discharge plateau or show no plateau but capacitor‐like sloping discharge profiles. This impacts the battery's practicability for flexible electronics where stable and consistent high energy is needed. Herein, an aqueous zinc hybrid battery based on a highly concentrated dual‐ion electrolyte and a hierarchically structured lithium‐ion‐intercalative LiVPO₄F cathode is developed. This hybrid battery delivers a flat and high‐voltage discharge plateau of nearly 1.9 V, ranking among the highest reported values for all aqueous zinc‐based batteries. The resultant high energy density of 235.6 Wh kg^?1 at a power density of 320.8 W kg^?1 also outperforms most reported zinc‐based batteries. A designed solid‐state and long‐lasting hydrogel electrolyte is subsequently applied in the fabrication of a flexible battery, which can be integrated into various flexible devices as powerful energy supply. The idea of designing such a hybrid battery offers a new strategy for developing high‐voltage and high‐energy aqueous energy storage systems.